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android / toolchain / rustc / refs/heads/main / . / vendor / pulldown-cmark-0.11.0 / src / firstpass.rs
blob: c9ecc0eba06dbe403ee0668d42f0edc2fa468a36 [file] [log] [blame] [edit]
//! The first pass resolves all block structure, generating an AST. Within a block, items
//! are in a linear chain with potential inline markup identified.
use std::cmp::max;
use std::ops::Range;
use crate::parse::{
scan_containers, Allocations, FootnoteDef, HeadingAttributes, Item, ItemBody, LinkDef,
LINK_MAX_NESTED_PARENS,
};
use crate::strings::CowStr;
use crate::tree::{Tree, TreeIndex};
use crate::Options;
use crate::{
linklabel::{scan_link_label_rest, LinkLabel},
HeadingLevel,
};
use crate::{scanners::*, MetadataBlockKind};
use unicase::UniCase;
/// Runs the first pass, which resolves the block structure of the document,
/// and returns the resulting tree.
pub(crate) fn run_first_pass(text: &str, options: Options) -> (Tree<Item>, Allocations<'_>) {
// This is a very naive heuristic for the number of nodes
// we'll need.
let start_capacity = max(128, text.len() / 32);
let lookup_table = &create_lut(&options);
let first_pass = FirstPass {
text,
tree: Tree::with_capacity(start_capacity),
begin_list_item: None,
last_line_blank: false,
allocs: Allocations::new(),
options,
lookup_table,
next_paragraph_task: None,
brace_context_next: 0,
brace_context_stack: Vec::new(),
};
first_pass.run()
}
// Each level of brace nesting adds another entry to a hash table.
// To limit the amount of memory consumed, do not create a new brace
// context beyond some amount deep.
//
// There are actually two limits at play here: this one,
// and the one where the maximum amount of distinct contexts passes
// the 255 item limit imposed by using `u8`. When over 255 distinct
// contexts are created, it wraps around, while this one instead makes it
// saturate, which is a better behavior.
const MATH_BRACE_CONTEXT_MAX_NESTING: usize = 25;
/// State for the first parsing pass.
struct FirstPass<'a, 'b> {
text: &'a str,
tree: Tree<Item>,
begin_list_item: Option<usize>,
last_line_blank: bool,
allocs: Allocations<'a>,
options: Options,
lookup_table: &'b LookupTable,
/// This is `Some(item)` when the next paragraph
/// starts with a task list marker.
next_paragraph_task: Option<Item>,
/// Math environment brace nesting.
brace_context_stack: Vec<u8>,
brace_context_next: usize,
}
impl<'a, 'b> FirstPass<'a, 'b> {
fn run(mut self) -> (Tree<Item>, Allocations<'a>) {
let mut ix = 0;
while ix < self.text.len() {
ix = self.parse_block(ix);
}
for _ in 0..self.tree.spine_len() {
self.pop(ix);
}
(self.tree, self.allocs)
}
/// Returns offset after block.
fn parse_block(&mut self, mut start_ix: usize) -> usize {
let bytes = self.text.as_bytes();
let mut line_start = LineStart::new(&bytes[start_ix..]);
// math spans and their braces are tracked only within a single block
self.brace_context_stack.clear();
self.brace_context_next = 0;
let i = scan_containers(
&self.tree,
&mut line_start,
self.options.has_gfm_footnotes(),
);
for _ in i..self.tree.spine_len() {
self.pop(start_ix);
}
if self.options.contains(Options::ENABLE_OLD_FOOTNOTES) {
// finish footnote if it's still open and was preceded by blank line
if let Some(node_ix) = self.tree.peek_up() {
if let ItemBody::FootnoteDefinition(..) = self.tree[node_ix].item.body {
if self.last_line_blank {
self.pop(start_ix);
}
}
}
// Footnote definitions of the form
// [^bar]:
// * anything really
let container_start = start_ix + line_start.bytes_scanned();
if let Some(bytecount) = self.parse_footnote(container_start) {
start_ix = container_start + bytecount;
start_ix += scan_blank_line(&bytes[start_ix..]).unwrap_or(0);
line_start = LineStart::new(&bytes[start_ix..]);
}
}
// Process new containers
loop {
if self.options.has_gfm_footnotes()
|| self.options.contains(Options::ENABLE_OLD_FOOTNOTES)
{
// Footnote definitions of the form
// [^bar]:
// * anything really
let save = line_start.clone();
let indent = line_start.scan_space_upto(4);
if indent < 4 {
let container_start = start_ix + line_start.bytes_scanned();
if let Some(bytecount) = self.parse_footnote(container_start) {
start_ix = container_start + bytecount;
line_start = LineStart::new(&bytes[start_ix..]);
continue;
} else {
line_start = save;
}
} else {
line_start = save;
}
}
let container_start = start_ix + line_start.bytes_scanned();
if let Some((ch, index, indent)) = line_start.scan_list_marker() {
let after_marker_index = start_ix + line_start.bytes_scanned();
self.continue_list(container_start, ch, index);
self.tree.append(Item {
start: container_start,
end: after_marker_index, // will get updated later if item not empty
body: ItemBody::ListItem(indent),
});
self.tree.push();
if let Some(n) = scan_blank_line(&bytes[after_marker_index..]) {
self.begin_list_item = Some(after_marker_index + n);
return after_marker_index + n;
}
if self.options.contains(Options::ENABLE_TASKLISTS) {
self.next_paragraph_task =
line_start.scan_task_list_marker().map(|is_checked| Item {
start: after_marker_index,
end: start_ix + line_start.bytes_scanned(),
body: ItemBody::TaskListMarker(is_checked),
});
}
} else if line_start.scan_blockquote_marker() {
let kind = if self.options.contains(Options::ENABLE_GFM) {
line_start.scan_blockquote_tag()
} else {
None
};
self.finish_list(start_ix);
self.tree.append(Item {
start: container_start,
end: 0, // will get set later
body: ItemBody::BlockQuote(kind),
});
self.tree.push();
if kind.is_some() {
// blockquote tag leaves us at the end of the line
// we need to scan through all the container syntax for the next line
// and break out if we can't re-scan all of them
let ix = start_ix + line_start.bytes_scanned();
let mut lazy_line_start = LineStart::new(&bytes[ix..]);
let current_container = scan_containers(
&self.tree,
&mut lazy_line_start,
self.options.has_gfm_footnotes(),
) == self.tree.spine_len();
if !lazy_line_start.scan_space(4)
&& self.scan_paragraph_interrupt(
&bytes[ix + lazy_line_start.bytes_scanned()..],
current_container,
)
{
return ix;
} else {
// blockquote tags act as if they were nested in a paragraph
// so you can lazily continue the imaginary paragraph off of them
line_start = lazy_line_start;
line_start.scan_all_space();
start_ix = ix;
break;
}
}
} else {
break;
}
}
let ix = start_ix + line_start.bytes_scanned();
if let Some(n) = scan_blank_line(&bytes[ix..]) {
if let Some(node_ix) = self.tree.peek_up() {
match &mut self.tree[node_ix].item.body {
ItemBody::BlockQuote(..) => (),
ItemBody::ListItem(indent) if self.begin_list_item.is_some() => {
self.last_line_blank = true;
// This is a blank list item.
// While the list itself can be continued no matter how many blank lines
// there are between this one and the next one, it cannot nest anything
// else, so its indentation should not be subtracted from the line start.
*indent = 0;
}
_ => {
self.last_line_blank = true;
}
}
}
return ix + n;
}
self.finish_list(start_ix);
// Save `remaining_space` here to avoid needing to backtrack `line_start` for HTML blocks
let remaining_space = line_start.remaining_space();
let indent = line_start.scan_space_upto(4);
if indent == 4 {
let ix = start_ix + line_start.bytes_scanned();
let remaining_space = line_start.remaining_space();
return self.parse_indented_code_block(ix, remaining_space);
}
let ix = start_ix + line_start.bytes_scanned();
if let Some((_n, metadata_block_ch)) = scan_metadata_block(
&bytes[ix..],
self.options
.contains(Options::ENABLE_YAML_STYLE_METADATA_BLOCKS),
self.options
.contains(Options::ENABLE_PLUSES_DELIMITED_METADATA_BLOCKS),
) {
return self.parse_metadata_block(ix, indent, metadata_block_ch);
}
// HTML Blocks
if bytes[ix] == b'<' {
// Types 1-5 are all detected by one function and all end with the same
// pattern
if let Some(html_end_tag) = get_html_end_tag(&bytes[(ix + 1)..]) {
return self.parse_html_block_type_1_to_5(
ix,
html_end_tag,
remaining_space,
indent,
);
}
// Detect type 6
if starts_html_block_type_6(&bytes[(ix + 1)..]) {
return self.parse_html_block_type_6_or_7(ix, remaining_space, indent);
}
// Detect type 7
if let Some(_html_bytes) = scan_html_type_7(&bytes[ix..]) {
return self.parse_html_block_type_6_or_7(ix, remaining_space, indent);
}
}
if let Ok(n) = scan_hrule(&bytes[ix..]) {
return self.parse_hrule(n, ix);
}
if let Some(atx_size) = scan_atx_heading(&bytes[ix..]) {
return self.parse_atx_heading(ix, atx_size);
}
if let Some((n, fence_ch)) = scan_code_fence(&bytes[ix..]) {
return self.parse_fenced_code_block(ix, indent, fence_ch, n);
}
// parse refdef
while let Some((bytecount, label, link_def)) =
self.parse_refdef_total(start_ix + line_start.bytes_scanned())
{
self.allocs.refdefs.0.entry(label).or_insert(link_def);
let container_start = start_ix + line_start.bytes_scanned();
let mut ix = container_start + bytecount;
// Refdefs act as if they were contained within a paragraph, for purposes of lazy
// continuations. For example:
//
// ```
// > [foo]: http://example.com
// bar
// ```
//
// is equivalent to
//
// ```
// > bar
//
// [foo]: http://example.com
// ```
if let Some(nl) = scan_blank_line(&bytes[ix..]) {
ix += nl;
let mut lazy_line_start = LineStart::new(&bytes[ix..]);
let current_container = scan_containers(
&self.tree,
&mut lazy_line_start,
self.options.has_gfm_footnotes(),
) == self.tree.spine_len();
if !lazy_line_start.scan_space(4)
&& self.scan_paragraph_interrupt(
&bytes[ix + lazy_line_start.bytes_scanned()..],
current_container,
)
{
return ix;
} else {
line_start = lazy_line_start;
line_start.scan_all_space();
start_ix = ix;
}
} else {
return ix;
}
}
let ix = start_ix + line_start.bytes_scanned();
self.parse_paragraph(ix)
}
/// Returns the offset of the first line after the table.
/// Assumptions: current focus is a table element and the table header
/// matches the separator line (same number of columns).
fn parse_table(
&mut self,
table_cols: usize,
head_start: usize,
body_start: usize,
) -> Option<usize> {
// filled empty cells are limited to protect against quadratic growth
// https://github.com/raphlinus/pulldown-cmark/issues/832
let mut missing_empty_cells = 0;
// parse header. this shouldn't fail because we made sure the table header is ok
let (_sep_start, thead_ix) =
self.parse_table_row_inner(head_start, table_cols, &mut missing_empty_cells)?;
self.tree[thead_ix].item.body = ItemBody::TableHead;
// parse body
let mut ix = body_start;
while let Some((next_ix, _row_ix)) =
self.parse_table_row(ix, table_cols, &mut missing_empty_cells)
{
ix = next_ix;
}
self.pop(ix);
Some(ix)
}
/// Call this when containers are taken care of.
/// Returns bytes scanned, row_ix
fn parse_table_row_inner(
&mut self,
mut ix: usize,
row_cells: usize,
missing_empty_cells: &mut usize,
) -> Option<(usize, TreeIndex)> {
// Limit to prevent a malicious input from causing a denial of service.
const MAX_AUTOCOMPLETED_CELLS: usize = 1 << 18; // = 0x40000
let bytes = self.text.as_bytes();
let mut cells = 0;
let mut final_cell_ix = None;
let old_cur = self.tree.cur();
let row_ix = self.tree.append(Item {
start: ix,
end: 0, // set at end of this function
body: ItemBody::TableRow,
});
self.tree.push();
loop {
ix += scan_ch(&bytes[ix..], b'|');
let start_ix = ix;
ix += scan_whitespace_no_nl(&bytes[ix..]);
if let Some(eol_bytes) = scan_eol(&bytes[ix..]) {
ix += eol_bytes;
break;
}
let cell_ix = self.tree.append(Item {
start: start_ix,
end: ix,
body: ItemBody::TableCell,
});
self.tree.push();
let (next_ix, _brk) = self.parse_line(ix, None, TableParseMode::Active);
self.tree[cell_ix].item.end = next_ix;
self.tree.pop();
ix = next_ix;
cells += 1;
if cells == row_cells {
final_cell_ix = Some(cell_ix);
}
}
if let (Some(cur), 0) = (old_cur, cells) {
self.pop(ix);
self.tree[cur].next = None;
return None;
}
// fill empty cells if needed
// note: this is where GFM and commonmark-extra diverge. we follow
// GFM here
for _ in cells..row_cells {
if *missing_empty_cells >= MAX_AUTOCOMPLETED_CELLS {
return None;
}
*missing_empty_cells += 1;
self.tree.append(Item {
start: ix,
end: ix,
body: ItemBody::TableCell,
});
}
// drop excess cells
if let Some(cell_ix) = final_cell_ix {
self.tree[cell_ix].next = None;
}
self.pop(ix);
Some((ix, row_ix))
}
/// Returns first offset after the row and the tree index of the row.
fn parse_table_row(
&mut self,
mut ix: usize,
row_cells: usize,
missing_empty_cells: &mut usize,
) -> Option<(usize, TreeIndex)> {
let bytes = self.text.as_bytes();
let mut line_start = LineStart::new(&bytes[ix..]);
let current_container = scan_containers(
&self.tree,
&mut line_start,
self.options.has_gfm_footnotes(),
) == self.tree.spine_len();
if !current_container {
return None;
}
line_start.scan_all_space();
ix += line_start.bytes_scanned();
if scan_paragraph_interrupt_no_table(
&bytes[ix..],
current_container,
self.options.has_gfm_footnotes(),
&self.tree,
) {
return None;
}
let (ix, row_ix) = self.parse_table_row_inner(ix, row_cells, missing_empty_cells)?;
Some((ix, row_ix))
}
/// Returns offset of line start after paragraph.
fn parse_paragraph(&mut self, start_ix: usize) -> usize {
let node_ix = self.tree.append(Item {
start: start_ix,
end: 0, // will get set later
body: ItemBody::Paragraph,
});
self.tree.push();
if let Some(item) = self.next_paragraph_task {
self.tree.append(item);
self.next_paragraph_task = None;
}
let bytes = self.text.as_bytes();
let mut ix = start_ix;
loop {
let scan_mode = if self.options.contains(Options::ENABLE_TABLES) && ix == start_ix {
TableParseMode::Scan
} else {
TableParseMode::Disabled
};
let (next_ix, brk) = self.parse_line(ix, None, scan_mode);
// break out when we find a table
if let Some(Item {
body: ItemBody::Table(alignment_ix),
..
}) = brk
{
let table_cols = self.allocs[alignment_ix].len();
self.tree[node_ix].item.body = ItemBody::Table(alignment_ix);
// this clears out any stuff we may have appended - but there may
// be a cleaner way
self.tree[node_ix].child = None;
self.tree.pop();
self.tree.push();
if let Some(ix) = self.parse_table(table_cols, ix, next_ix) {
return ix;
}
}
ix = next_ix;
let mut line_start = LineStart::new(&bytes[ix..]);
let current_container = scan_containers(
&self.tree,
&mut line_start,
self.options.has_gfm_footnotes(),
) == self.tree.spine_len();
let trailing_backslash_pos = match brk {
Some(Item {
start,
body: ItemBody::HardBreak(true),
..
}) if bytes[start] == b'\\' => Some(start),
_ => None,
};
if !line_start.scan_space(4) {
let ix_new = ix + line_start.bytes_scanned();
if current_container {
if let Some(ix_setext) =
self.parse_setext_heading(ix_new, node_ix, trailing_backslash_pos.is_some())
{
if let Some(pos) = trailing_backslash_pos {
self.tree.append_text(pos, pos + 1, false);
}
ix = ix_setext;
break;
}
}
// first check for non-empty lists, then for other interrupts
let suffix = &bytes[ix_new..];
if self.scan_paragraph_interrupt(suffix, current_container) {
if let Some(pos) = trailing_backslash_pos {
self.tree.append_text(pos, pos + 1, false);
}
break;
}
}
line_start.scan_all_space();
if line_start.is_at_eol() {
if let Some(pos) = trailing_backslash_pos {
self.tree.append_text(pos, pos + 1, false);
}
break;
}
ix = next_ix + line_start.bytes_scanned();
if let Some(item) = brk {
self.tree.append(item);
}
}
self.pop(ix);
ix
}
/// Returns end ix of setext_heading on success.
fn parse_setext_heading(
&mut self,
ix: usize,
node_ix: TreeIndex,
has_trailing_content: bool,
) -> Option<usize> {
let bytes = self.text.as_bytes();
let (n, level) = scan_setext_heading(&bytes[ix..])?;
let mut attrs = None;
if let Some(cur_ix) = self.tree.cur() {
let parent_ix = self.tree.peek_up().unwrap();
let header_start = self.tree[parent_ix].item.start;
// Note that `self.tree[parent_ix].item.end` might be zero at this point.
// Use the end position of the current node (i.e. the last known child
// of the parent) instead.
let header_end = self.tree[cur_ix].item.end;
// extract the trailing attribute block
let (content_end, attrs_) =
self.extract_and_parse_heading_attribute_block(header_start, header_end);
attrs = attrs_;
// strip trailing whitespace
let new_end = if has_trailing_content {
content_end
} else {
let trailing_ws =
scan_rev_while(&bytes[header_start..content_end], is_ascii_whitespace_no_nl);
content_end - trailing_ws
};
if attrs.is_some() {
// remove trailing block attributes
self.tree.truncate_siblings(new_end);
}
if let Some(cur_ix) = self.tree.cur() {
self.tree[cur_ix].item.end = new_end;
}
}
self.tree[node_ix].item.body = ItemBody::Heading(
level,
attrs.map(|attrs| self.allocs.allocate_heading(attrs)),
);
Some(ix + n)
}
/// Parse a line of input, appending text and items to tree.
///
/// Returns: index after line and an item representing the break.
fn parse_line(
&mut self,
start: usize,
end: Option<usize>,
mode: TableParseMode,
) -> (usize, Option<Item>) {
let bytes = self.text.as_bytes();
let bytes = match end {
Some(end) => &bytes[..end],
None => bytes,
};
let bytes_len = bytes.len();
let mut pipes = 0;
let mut last_pipe_ix = start;
let mut begin_text = start;
let mut backslash_escaped = false;
let (final_ix, brk) = iterate_special_bytes(self.lookup_table, bytes, start, |ix, byte| {
match byte {
b'\n' | b'\r' => {
if let TableParseMode::Active = mode {
return LoopInstruction::BreakAtWith(ix, None);
}
let mut i = ix;
let eol_bytes = scan_eol(&bytes[ix..]).unwrap();
let end_ix = ix + eol_bytes;
let trailing_backslashes = scan_rev_while(&bytes[..ix], |b| b == b'\\');
if trailing_backslashes % 2 == 1 && end_ix < bytes_len {
i -= 1;
self.tree.append_text(begin_text, i, backslash_escaped);
backslash_escaped = false;
return LoopInstruction::BreakAtWith(
end_ix,
Some(Item {
start: i,
end: end_ix,
body: ItemBody::HardBreak(true),
}),
);
}
if mode == TableParseMode::Scan && pipes > 0 {
// check if we may be parsing a table
let next_line_ix = ix + eol_bytes;
let mut line_start = LineStart::new(&bytes[next_line_ix..]);
if scan_containers(
&self.tree,
&mut line_start,
self.options.has_gfm_footnotes(),
) == self.tree.spine_len()
{
let table_head_ix = next_line_ix + line_start.bytes_scanned();
let (table_head_bytes, alignment) =
scan_table_head(&bytes[table_head_ix..]);
if table_head_bytes > 0 {
// computing header count from number of pipes
let header_count =
count_header_cols(bytes, pipes, start, last_pipe_ix);
// make sure they match the number of columns we find in separator line
if alignment.len() == header_count {
let alignment_ix = self.allocs.allocate_alignment(alignment);
let end_ix = table_head_ix + table_head_bytes;
return LoopInstruction::BreakAtWith(
end_ix,
Some(Item {
start: i,
end: end_ix, // must update later
body: ItemBody::Table(alignment_ix),
}),
);
}
}
}
}
let trailing_whitespace =
scan_rev_while(&bytes[..ix], is_ascii_whitespace_no_nl);
if trailing_whitespace >= 2 {
i -= trailing_whitespace;
self.tree.append_text(begin_text, i, backslash_escaped);
backslash_escaped = false;
return LoopInstruction::BreakAtWith(
end_ix,
Some(Item {
start: i,
end: end_ix,
body: ItemBody::HardBreak(false),
}),
);
}
self.tree
.append_text(begin_text, ix - trailing_whitespace, backslash_escaped);
backslash_escaped = false;
LoopInstruction::BreakAtWith(
end_ix,
Some(Item {
start: i,
end: end_ix,
body: ItemBody::SoftBreak,
}),
)
}
b'\\' => {
if ix + 1 < bytes_len && is_ascii_punctuation(bytes[ix + 1]) {
self.tree.append_text(begin_text, ix, backslash_escaped);
if bytes[ix + 1] == b'`' {
let count = 1 + scan_ch_repeat(&bytes[(ix + 2)..], b'`');
self.tree.append(Item {
start: ix + 1,
end: ix + count + 1,
body: ItemBody::MaybeCode(count, true),
});
begin_text = ix + 1 + count;
backslash_escaped = false;
LoopInstruction::ContinueAndSkip(count)
} else if bytes[ix + 1] == b'|' && TableParseMode::Active == mode {
// Yeah, it's super weird that backslash escaped pipes in tables aren't "real"
// backslash escapes.
//
// This tree structure is intended for the benefit of inline analysis, and it
// is supposed to operate as-if backslash escaped pipes were stripped out in a
// separate pass.
begin_text = ix + 1;
backslash_escaped = false;
LoopInstruction::ContinueAndSkip(1)
} else if ix + 2 < bytes_len
&& bytes[ix + 1] == b'\\'
&& bytes[ix + 2] == b'|'
&& TableParseMode::Active == mode
{
// To parse `\\|`, discard the backslashes and parse the `|` that follows it.
begin_text = ix + 2;
backslash_escaped = true;
LoopInstruction::ContinueAndSkip(2)
} else {
begin_text = ix + 1;
backslash_escaped = true;
LoopInstruction::ContinueAndSkip(1)
}
} else {
LoopInstruction::ContinueAndSkip(0)
}
}
c @ b'*' | c @ b'_' | c @ b'~' => {
let string_suffix = &self.text[ix..];
let count = 1 + scan_ch_repeat(&string_suffix.as_bytes()[1..], c);
let can_open = delim_run_can_open(
&self.text[start..],
string_suffix,
count,
ix - start,
mode,
);
let can_close = delim_run_can_close(
&self.text[start..],
string_suffix,
count,
ix - start,
mode,
);
let is_valid_seq = c != b'~' || count <= 2;
if (can_open || can_close) && is_valid_seq {
self.tree.append_text(begin_text, ix, backslash_escaped);
backslash_escaped = false;
for i in 0..count {
self.tree.append(Item {
start: ix + i,
end: ix + i + 1,
body: ItemBody::MaybeEmphasis(count - i, can_open, can_close),
});
}
begin_text = ix + count;
}
LoopInstruction::ContinueAndSkip(count - 1)
}
b'$' => {
let string_suffix = &self.text[ix..];
let can_open = !string_suffix[1..]
.as_bytes()
.first()
.copied()
.map_or(true, is_ascii_whitespace);
let can_close = ix > start
&& !self.text[..ix]
.as_bytes()
.last()
.copied()
.map_or(true, is_ascii_whitespace);
// 0xFFFF_FFFF... represents the root brace context. Using None would require
// storing Option<u8>, which is bigger than u8.
//
// These shouldn't conflict unless you have 255 levels of nesting, which is
// past the intended limit anyway.
//
// Unbalanced braces will cause the root to be changed, which is why it gets
// stored here.
let brace_context =
if self.brace_context_stack.len() > MATH_BRACE_CONTEXT_MAX_NESTING {
self.brace_context_next as u8
} else {
self.brace_context_stack.last().copied().unwrap_or_else(|| {
self.brace_context_stack.push(!0);
!0
})
};
self.tree.append_text(begin_text, ix, backslash_escaped);
self.tree.append(Item {
start: ix,
end: ix + 1,
body: ItemBody::MaybeMath(can_open, can_close, brace_context),
});
begin_text = ix + 1;
LoopInstruction::ContinueAndSkip(0)
}
b'{' => {
if self.brace_context_stack.len() == MATH_BRACE_CONTEXT_MAX_NESTING {
self.brace_context_stack.push(self.brace_context_next as u8);
self.brace_context_next = MATH_BRACE_CONTEXT_MAX_NESTING;
} else if self.brace_context_stack.len() > MATH_BRACE_CONTEXT_MAX_NESTING {
// When we reach the limit of nesting, switch from actually matching
// braces to just counting them.
self.brace_context_next += 1;
} else if !self.brace_context_stack.is_empty() {
// Store nothing if no math environment has been reached yet.
self.brace_context_stack.push(self.brace_context_next as u8);
self.brace_context_next += 1;
}
LoopInstruction::ContinueAndSkip(0)
}
b'}' => {
if let &mut [ref mut top_level_context] = &mut self.brace_context_stack[..] {
// Unbalanced Braces
//
// The initial, root top-level brace context is -1, but this is changed whenever an unbalanced
// close brace is encountered:
//
// This is not a math environment: $}$
// ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^|^
// -1 |-2
//
// To ensure this can't get parsed as math, each side of the unbalanced
// brace is an irreversibly separate brace context. As long as the math
// environment itself contains balanced braces, they should share a top level context.
//
// Math environment contains 2+2: $}$2+2$
// ^^^ this is a math environment
*top_level_context = top_level_context.wrapping_sub(1);
} else if self.brace_context_stack.len() > MATH_BRACE_CONTEXT_MAX_NESTING {
// When we exceed 25 levels of nesting, switch from accurately balancing braces
// to just counting them. When we dip back below the limit, switch back.
if self.brace_context_next <= MATH_BRACE_CONTEXT_MAX_NESTING {
self.brace_context_stack.pop();
} else {
self.brace_context_next -= 1;
}
} else {
self.brace_context_stack.pop();
}
LoopInstruction::ContinueAndSkip(0)
}
b'`' => {
self.tree.append_text(begin_text, ix, backslash_escaped);
backslash_escaped = false;
let count = 1 + scan_ch_repeat(&bytes[(ix + 1)..], b'`');
self.tree.append(Item {
start: ix,
end: ix + count,
body: ItemBody::MaybeCode(count, false),
});
begin_text = ix + count;
LoopInstruction::ContinueAndSkip(count - 1)
}
b'<' if bytes.get(ix + 1) != Some(&b'\\') => {
// Note: could detect some non-HTML cases and early escape here, but not
// clear that's a win.
self.tree.append_text(begin_text, ix, backslash_escaped);
backslash_escaped = false;
self.tree.append(Item {
start: ix,
end: ix + 1,
body: ItemBody::MaybeHtml,
});
begin_text = ix + 1;
LoopInstruction::ContinueAndSkip(0)
}
b'!' => {
if ix + 1 < bytes_len && bytes[ix + 1] == b'[' {
self.tree.append_text(begin_text, ix, backslash_escaped);
backslash_escaped = false;
self.tree.append(Item {
start: ix,
end: ix + 2,
body: ItemBody::MaybeImage,
});
begin_text = ix + 2;
LoopInstruction::ContinueAndSkip(1)
} else {
LoopInstruction::ContinueAndSkip(0)
}
}
b'[' => {
self.tree.append_text(begin_text, ix, backslash_escaped);
backslash_escaped = false;
self.tree.append(Item {
start: ix,
end: ix + 1,
body: ItemBody::MaybeLinkOpen,
});
begin_text = ix + 1;
LoopInstruction::ContinueAndSkip(0)
}
b']' => {
self.tree.append_text(begin_text, ix, backslash_escaped);
backslash_escaped = false;
self.tree.append(Item {
start: ix,
end: ix + 1,
body: ItemBody::MaybeLinkClose(true),
});
begin_text = ix + 1;
LoopInstruction::ContinueAndSkip(0)
}
b'&' => match scan_entity(&bytes[ix..]) {
(n, Some(value)) => {
self.tree.append_text(begin_text, ix, backslash_escaped);
backslash_escaped = false;
self.tree.append(Item {
start: ix,
end: ix + n,
body: ItemBody::SynthesizeText(self.allocs.allocate_cow(value)),
});
begin_text = ix + n;
LoopInstruction::ContinueAndSkip(n - 1)
}
_ => LoopInstruction::ContinueAndSkip(0),
},
b'|' => {
if ix != 0 && bytes[ix - 1] == b'\\' {
LoopInstruction::ContinueAndSkip(0)
} else if let TableParseMode::Active = mode {
LoopInstruction::BreakAtWith(ix, None)
} else {
last_pipe_ix = ix;
pipes += 1;
LoopInstruction::ContinueAndSkip(0)
}
}
b'.' => {
if ix + 2 < bytes.len() && bytes[ix + 1] == b'.' && bytes[ix + 2] == b'.' {
self.tree.append_text(begin_text, ix, backslash_escaped);
backslash_escaped = false;
self.tree.append(Item {
start: ix,
end: ix + 3,
body: ItemBody::SynthesizeChar('…'),
});
begin_text = ix + 3;
LoopInstruction::ContinueAndSkip(2)
} else {
LoopInstruction::ContinueAndSkip(0)
}
}
b'-' => {
let count = 1 + scan_ch_repeat(&bytes[(ix + 1)..], b'-');
if count == 1 {
LoopInstruction::ContinueAndSkip(0)
} else {
let itembody = if count == 2 {
ItemBody::SynthesizeChar('–')
} else if count == 3 {
ItemBody::SynthesizeChar('—')
} else {
let (ems, ens) = match count % 6 {
0 | 3 => (count / 3, 0),
2 | 4 => (0, count / 2),
1 => (count / 3 - 1, 2),
_ => (count / 3, 1),
};
// – and — are 3 bytes each in utf8
let mut buf = String::with_capacity(3 * (ems + ens));
for _ in 0..ems {
buf.push('—');
}
for _ in 0..ens {
buf.push('–');
}
ItemBody::SynthesizeText(self.allocs.allocate_cow(buf.into()))
};
self.tree.append_text(begin_text, ix, backslash_escaped);
backslash_escaped = false;
self.tree.append(Item {
start: ix,
end: ix + count,
body: itembody,
});
begin_text = ix + count;
LoopInstruction::ContinueAndSkip(count - 1)
}
}
c @ b'\'' | c @ b'"' => {
let string_suffix = &self.text[ix..];
let can_open =
delim_run_can_open(&self.text[start..], string_suffix, 1, ix - start, mode);
let can_close = delim_run_can_close(
&self.text[start..],
string_suffix,
1,
ix - start,
mode,
);
self.tree.append_text(begin_text, ix, backslash_escaped);
backslash_escaped = false;
self.tree.append(Item {
start: ix,
end: ix + 1,
body: ItemBody::MaybeSmartQuote(c, can_open, can_close),
});
begin_text = ix + 1;
LoopInstruction::ContinueAndSkip(0)
}
_ => LoopInstruction::ContinueAndSkip(0),
}
});
if brk.is_none() {
let trailing_whitespace =
scan_rev_while(&bytes[begin_text..final_ix], is_ascii_whitespace_no_nl);
// need to close text at eof
self.tree.append_text(
begin_text,
final_ix - trailing_whitespace,
backslash_escaped,
);
}
(final_ix, brk)
}
/// When start_ix is at the beginning of an HTML block of type 1 to 5,
/// this will find the end of the block, adding the block itself to the
/// tree and also keeping track of the lines of HTML within the block.
///
/// The html_end_tag is the tag that must be found on a line to end the block.
fn parse_html_block_type_1_to_5(
&mut self,
start_ix: usize,
html_end_tag: &str,
mut remaining_space: usize,
mut indent: usize,
) -> usize {
self.tree.append(Item {
start: start_ix,
end: 0, // set later
body: ItemBody::HtmlBlock,
});
self.tree.push();
let bytes = self.text.as_bytes();
let mut ix = start_ix;
let end_ix;
loop {
let line_start_ix = ix;
ix += scan_nextline(&bytes[ix..]);
self.append_html_line(remaining_space.max(indent), line_start_ix, ix);
let mut line_start = LineStart::new(&bytes[ix..]);
let n_containers = scan_containers(
&self.tree,
&mut line_start,
self.options.has_gfm_footnotes(),
);
if n_containers < self.tree.spine_len() {
end_ix = ix;
break;
}
if self.text[line_start_ix..ix].contains(html_end_tag) {
end_ix = ix;
break;
}
let next_line_ix = ix + line_start.bytes_scanned();
if next_line_ix == self.text.len() {
end_ix = next_line_ix;
break;
}
ix = next_line_ix;
remaining_space = line_start.remaining_space();
indent = 0;
}
self.pop(end_ix);
ix
}
/// When start_ix is at the beginning of an HTML block of type 6 or 7,
/// this will consume lines until there is a blank line and keep track of
/// the HTML within the block.
fn parse_html_block_type_6_or_7(
&mut self,
start_ix: usize,
mut remaining_space: usize,
mut indent: usize,
) -> usize {
self.tree.append(Item {
start: start_ix,
end: 0, // set later
body: ItemBody::HtmlBlock,
});
self.tree.push();
let bytes = self.text.as_bytes();
let mut ix = start_ix;
let end_ix;
loop {
let line_start_ix = ix;
ix += scan_nextline(&bytes[ix..]);
self.append_html_line(remaining_space.max(indent), line_start_ix, ix);
let mut line_start = LineStart::new(&bytes[ix..]);
let n_containers = scan_containers(
&self.tree,
&mut line_start,
self.options.has_gfm_footnotes(),
);
if n_containers < self.tree.spine_len() || line_start.is_at_eol() {
end_ix = ix;
break;
}
let next_line_ix = ix + line_start.bytes_scanned();
if next_line_ix == self.text.len() || scan_blank_line(&bytes[next_line_ix..]).is_some()
{
end_ix = next_line_ix;
break;
}
ix = next_line_ix;
remaining_space = line_start.remaining_space();
indent = 0;
}
self.pop(end_ix);
ix
}
fn parse_indented_code_block(&mut self, start_ix: usize, mut remaining_space: usize) -> usize {
self.tree.append(Item {
start: start_ix,
end: 0, // will get set later
body: ItemBody::IndentCodeBlock,
});
self.tree.push();
let bytes = self.text.as_bytes();
let mut last_nonblank_child = None;
let mut last_nonblank_ix = 0;
let mut end_ix = 0;
self.last_line_blank = false;
let mut ix = start_ix;
loop {
let line_start_ix = ix;
ix += scan_nextline(&bytes[ix..]);
self.append_code_text(remaining_space, line_start_ix, ix);
// TODO(spec clarification): should we synthesize newline at EOF?
if !self.last_line_blank {
last_nonblank_child = self.tree.cur();
last_nonblank_ix = ix;
end_ix = ix;
}
let mut line_start = LineStart::new(&bytes[ix..]);
let n_containers = scan_containers(
&self.tree,
&mut line_start,
self.options.has_gfm_footnotes(),
);
if n_containers < self.tree.spine_len()
|| !(line_start.scan_space(4) || line_start.is_at_eol())
{
break;
}
let next_line_ix = ix + line_start.bytes_scanned();
if next_line_ix == self.text.len() {
break;
}
ix = next_line_ix;
remaining_space = line_start.remaining_space();
self.last_line_blank = scan_blank_line(&bytes[ix..]).is_some();
}
// Trim trailing blank lines.
if let Some(child) = last_nonblank_child {
self.tree[child].next = None;
self.tree[child].item.end = last_nonblank_ix;
}
self.pop(end_ix);
ix
}
fn parse_fenced_code_block(
&mut self,
start_ix: usize,
indent: usize,
fence_ch: u8,
n_fence_char: usize,
) -> usize {
let bytes = self.text.as_bytes();
let mut info_start = start_ix + n_fence_char;
info_start += scan_whitespace_no_nl(&bytes[info_start..]);
// TODO: info strings are typically very short. wouldn't it be faster
// to just do a forward scan here?
let mut ix = info_start + scan_nextline(&bytes[info_start..]);
let info_end = ix - scan_rev_while(&bytes[info_start..ix], is_ascii_whitespace);
let info_string = unescape(&self.text[info_start..info_end], self.tree.is_in_table());
self.tree.append(Item {
start: start_ix,
end: 0, // will get set later
body: ItemBody::FencedCodeBlock(self.allocs.allocate_cow(info_string)),
});
self.tree.push();
loop {
let mut line_start = LineStart::new(&bytes[ix..]);
let n_containers = scan_containers(
&self.tree,
&mut line_start,
self.options.has_gfm_footnotes(),
);
if n_containers < self.tree.spine_len() {
// this line will get parsed again as not being part of the code
// if it's blank, it should be parsed as a blank line
self.pop(ix);
return ix;
}
line_start.scan_space(indent);
let mut close_line_start = line_start.clone();
if !close_line_start.scan_space(4 - indent) {
let close_ix = ix + close_line_start.bytes_scanned();
if let Some(n) = scan_closing_code_fence(&bytes[close_ix..], fence_ch, n_fence_char)
{
ix = close_ix + n;
self.pop(ix);
// try to read trailing whitespace or it will register as a completely blank line
return ix + scan_blank_line(&bytes[ix..]).unwrap_or(0);
}
}
let remaining_space = line_start.remaining_space();
ix += line_start.bytes_scanned();
let next_ix = ix + scan_nextline(&bytes[ix..]);
self.append_code_text(remaining_space, ix, next_ix);
ix = next_ix;
}
}
fn parse_metadata_block(
&mut self,
start_ix: usize,
indent: usize,
metadata_block_ch: u8,
) -> usize {
// metadata blocks cannot be indented
if indent > 0 {
return 0;
}
let bytes = self.text.as_bytes();
let metadata_block_kind = match metadata_block_ch {
b'-' => MetadataBlockKind::YamlStyle,
b'+' => MetadataBlockKind::PlusesStyle,
_ => panic!("Erroneous metadata block character when parsing metadata block"),
};
// 3 delimiter characters
let mut ix = start_ix + 3 + scan_nextline(&bytes[start_ix + 3..]);
self.tree.append(Item {
start: start_ix,
end: 0, // will get set later
body: ItemBody::MetadataBlock(metadata_block_kind),
});
self.tree.push();
loop {
let mut line_start = LineStart::new(&bytes[ix..]);
let n_containers = scan_containers(
&self.tree,
&mut line_start,
self.options.has_gfm_footnotes(),
);
if n_containers < self.tree.spine_len() {
break;
}
if let (_, 0) = calc_indent(&bytes[ix..], 4) {
if let Some(n) = scan_closing_metadata_block(&bytes[ix..], metadata_block_ch) {
ix += n;
break;
}
}
let remaining_space = line_start.remaining_space();
ix += line_start.bytes_scanned();
let next_ix = ix + scan_nextline(&bytes[ix..]);
self.append_code_text(remaining_space, ix, next_ix);
ix = next_ix;
}
self.pop(ix);
// try to read trailing whitespace or it will register as a completely blank line
ix + scan_blank_line(&bytes[ix..]).unwrap_or(0)
}
fn append_code_text(&mut self, remaining_space: usize, start: usize, end: usize) {
if remaining_space > 0 {
let cow_ix = self.allocs.allocate_cow(" "[..remaining_space].into());
self.tree.append(Item {
start,
end: start,
body: ItemBody::SynthesizeText(cow_ix),
});
}
if self.text.as_bytes()[end - 2] == b'\r' {
// Normalize CRLF to LF
self.tree.append_text(start, end - 2, false);
self.tree.append_text(end - 1, end, false);
} else {
self.tree.append_text(start, end, false);
}
}
/// Appends a line of HTML to the tree.
fn append_html_line(&mut self, remaining_space: usize, start: usize, end: usize) {
if remaining_space > 0 {
let cow_ix = self.allocs.allocate_cow(" "[..remaining_space].into());
self.tree.append(Item {
start,
end: start,
body: ItemBody::SynthesizeText(cow_ix),
});
}
if self.text.as_bytes()[end - 2] == b'\r' {
// Normalize CRLF to LF
self.tree.append(Item {
start,
end: end - 2,
body: ItemBody::Html,
});
self.tree.append(Item {
start: end - 1,
end,
body: ItemBody::Html,
});
} else {
self.tree.append(Item {
start,
end,
body: ItemBody::Html,
});
}
}
/// Pop a container, setting its end.
fn pop(&mut self, ix: usize) {
let cur_ix = self.tree.pop().unwrap();
self.tree[cur_ix].item.end = ix;
if let ItemBody::List(true, _, _) = self.tree[cur_ix].item.body {
surgerize_tight_list(&mut self.tree, cur_ix);
self.begin_list_item = None;
}
}
/// Close a list if it's open. Also set loose if last line was blank
/// and end current list if it's a lone, empty item
fn finish_list(&mut self, ix: usize) {
self.finish_empty_list_item();
if let Some(node_ix) = self.tree.peek_up() {
if let ItemBody::List(_, _, _) = self.tree[node_ix].item.body {
self.pop(ix);
}
}
if self.last_line_blank {
if let Some(node_ix) = self.tree.peek_grandparent() {
if let ItemBody::List(ref mut is_tight, _, _) = self.tree[node_ix].item.body {
*is_tight = false;
}
}
self.last_line_blank = false;
}
}
fn finish_empty_list_item(&mut self) {
if let Some(begin_list_item) = self.begin_list_item {
if self.last_line_blank {
// A list item can begin with at most one blank line.
if let Some(node_ix) = self.tree.peek_up() {
if let ItemBody::ListItem(_) = self.tree[node_ix].item.body {
self.pop(begin_list_item);
}
}
}
}
self.begin_list_item = None;
}
/// Continue an existing list or start a new one if there's not an open
/// list that matches.
fn continue_list(&mut self, start: usize, ch: u8, index: u64) {
self.finish_empty_list_item();
if let Some(node_ix) = self.tree.peek_up() {
if let ItemBody::List(ref mut is_tight, existing_ch, _) = self.tree[node_ix].item.body {
if existing_ch == ch {
if self.last_line_blank {
*is_tight = false;
self.last_line_blank = false;
}
return;
}
}
// TODO: this is not the best choice for end; maybe get end from last list item.
self.finish_list(start);
}
self.tree.append(Item {
start,
end: 0, // will get set later
body: ItemBody::List(true, ch, index),
});
self.tree.push();
self.last_line_blank = false;
}
/// Parse a thematic break.
///
/// Returns index of start of next line.
fn parse_hrule(&mut self, hrule_size: usize, ix: usize) -> usize {
self.tree.append(Item {
start: ix,
end: ix + hrule_size,
body: ItemBody::Rule,
});
ix + hrule_size
}
/// Parse an ATX heading.
///
/// Returns index of start of next line.
fn parse_atx_heading(&mut self, start: usize, atx_level: HeadingLevel) -> usize {
let mut ix = start;
let heading_ix = self.tree.append(Item {
start,
end: 0, // set later
body: ItemBody::default(), // set later
});
ix += atx_level as usize;
// next char is space or eol (guaranteed by scan_atx_heading)
let bytes = self.text.as_bytes();
if let Some(eol_bytes) = scan_eol(&bytes[ix..]) {
self.tree[heading_ix].item.end = ix + eol_bytes;
self.tree[heading_ix].item.body = ItemBody::Heading(atx_level, None);
return ix + eol_bytes;
}
// skip leading spaces
let skip_spaces = scan_whitespace_no_nl(&bytes[ix..]);
ix += skip_spaces;
// now handle the header text
let header_start = ix;
let header_node_idx = self.tree.push(); // so that we can set the endpoint later
// trim the trailing attribute block before parsing the entire line, if necessary
let (end, content_end, attrs) = if self.options.contains(Options::ENABLE_HEADING_ATTRIBUTES)
{
// the start of the next line is the end of the header since the
// header cannot have line breaks
let header_end = header_start + scan_nextline(&bytes[header_start..]);
let (content_end, attrs) =
self.extract_and_parse_heading_attribute_block(header_start, header_end);
self.parse_line(ix, Some(content_end), TableParseMode::Disabled);
(header_end, content_end, attrs)
} else {
let (line_ix, line_brk) = self.parse_line(ix, None, TableParseMode::Disabled);
ix = line_ix;
// Backslash at end is actually hard line break
if let Some(Item {
start,
end,
body: ItemBody::HardBreak(true),
}) = line_brk
{
self.tree.append_text(start, end, false);
}
(ix, ix, None)
};
self.tree[header_node_idx].item.end = end;
// remove trailing matter from header text
let mut empty_text_node = false;
if let Some(cur_ix) = self.tree.cur() {
// remove closing of the ATX heading
let header_text = &bytes[header_start..content_end];
let mut limit = header_text
.iter()
.rposition(|&b| !(b == b'\n' || b == b'\r' || b == b' '))
.map_or(0, |i| i + 1);
let closer = header_text[..limit]
.iter()
.rposition(|&b| b != b'#')
.map_or(0, |i| i + 1);
if closer == 0 {
limit = closer;
} else {
let spaces = scan_rev_while(&header_text[..closer], |b| b == b' ');
if spaces > 0 {
limit = closer - spaces;
}
}
// if text is only spaces, then remove them
self.tree[cur_ix].item.end = limit + header_start;
// limit = 0 when text is empty after removing spaces
if limit == 0 {
empty_text_node = true;
}
}
if empty_text_node {
self.tree.remove_node();
} else {
self.tree.pop();
}
self.tree[heading_ix].item.body = ItemBody::Heading(
atx_level,
attrs.map(|attrs| self.allocs.allocate_heading(attrs)),
);
end
}
/// Returns the number of bytes scanned on success.
fn parse_footnote(&mut self, start: usize) -> Option<usize> {
let bytes = &self.text.as_bytes()[start..];
if !bytes.starts_with(b"[^") {
return None;
}
let (mut i, label) = if self.options.has_gfm_footnotes() {
// GitHub doesn't allow footnote definition labels to contain line breaks.
// It actually does allow this for link definitions under certain circumstances,
// but for this it's simpler to avoid it.
scan_link_label_rest(&self.text[start + 2..], &|_| None, self.tree.is_in_table())?
} else {
self.parse_refdef_label(start + 2)?
};
if self.options.has_gfm_footnotes() && label.bytes().any(|b| b == b'\r' || b == b'\n') {
// GitHub doesn't allow footnote definition labels to contain line breaks,
// even if they're escaped.
return None;
}
i += 2;
if scan_ch(&bytes[i..], b':') == 0 {
return None;
}
i += 1;
self.finish_list(start);
if self.options.has_gfm_footnotes() {
if let Some(node_ix) = self.tree.peek_up() {
if let ItemBody::FootnoteDefinition(..) = self.tree[node_ix].item.body {
// finish previous footnote if it's still open
self.pop(start);
}
}
i += scan_whitespace_no_nl(&bytes[i..]);
}
self.allocs.footdefs.0.insert(
UniCase::new(label.clone()),
FootnoteDef { use_count: 0 },
);
self.tree.append(Item {
start,
end: 0, // will get set later
// TODO: check whether the label here is strictly necessary
body: ItemBody::FootnoteDefinition(self.allocs.allocate_cow(label)),
});
self.tree.push();
Some(i)
}
/// Tries to parse a reference label, which can be interrupted by new blocks.
/// On success, returns the number of bytes of the label and the label itself.
fn parse_refdef_label(&self, start: usize) -> Option<(usize, CowStr<'a>)> {
scan_link_label_rest(
&self.text[start..],
&|bytes| {
let mut line_start = LineStart::new(bytes);
let current_container = scan_containers(
&self.tree,
&mut line_start,
self.options.has_gfm_footnotes(),
) == self.tree.spine_len();
if line_start.scan_space(4) {
return Some(line_start.bytes_scanned());
}
let bytes_scanned = line_start.bytes_scanned();
let suffix = &bytes[bytes_scanned..];
if self.scan_paragraph_interrupt(suffix, current_container)
|| (current_container && scan_setext_heading(suffix).is_some())
{
None
} else {
Some(bytes_scanned)
}
},
self.tree.is_in_table(),
)
}
/// Returns number of bytes scanned, label and definition on success.
fn parse_refdef_total(&mut self, start: usize) -> Option<(usize, LinkLabel<'a>, LinkDef<'a>)> {
let bytes = &self.text.as_bytes()[start..];
if scan_ch(bytes, b'[') == 0 {
return None;
}
let (mut i, label) = self.parse_refdef_label(start + 1)?;
i += 1;
if scan_ch(&bytes[i..], b':') == 0 {
return None;
}
i += 1;
let (bytecount, link_def) = self.scan_refdef(start, start + i)?;
Some((bytecount + i, UniCase::new(label), link_def))
}
/// Returns number of bytes and number of newlines
fn scan_refdef_space(&self, bytes: &[u8], mut i: usize) -> Option<(usize, usize)> {
let mut newlines = 0;
loop {
let whitespaces = scan_whitespace_no_nl(&bytes[i..]);
i += whitespaces;
if let Some(eol_bytes) = scan_eol(&bytes[i..]) {
i += eol_bytes;
newlines += 1;
if newlines > 1 {
return None;
}
} else {
break;
}
let mut line_start = LineStart::new(&bytes[i..]);
let current_container = scan_containers(
&self.tree,
&mut line_start,
self.options.has_gfm_footnotes(),
) == self.tree.spine_len();
if !line_start.scan_space(4) {
let suffix = &bytes[i + line_start.bytes_scanned()..];
if self.scan_paragraph_interrupt(suffix, current_container)
|| scan_setext_heading(suffix).is_some()
{
return None;
}
}
i += line_start.bytes_scanned();
}
Some((i, newlines))
}
// returns (bytelength, title_str)
fn scan_refdef_title<'t>(&self, text: &'t str) -> Option<(usize, CowStr<'t>)> {
let bytes = text.as_bytes();
let closing_delim = match bytes.first()? {
b'\'' => b'\'',
b'"' => b'"',
b'(' => b')',
_ => return None,
};
let mut bytecount = 1;
let mut linestart = 1;
let mut linebuf = None;
while let Some(&c) = bytes.get(bytecount) {
match c {
b'(' if closing_delim == b')' => {
// https://spec.commonmark.org/0.30/#link-title
// a sequence of zero or more characters between matching parentheses ((...)),
// including a ( or ) character only if it is backslash-escaped.
return None;
}
b'\n' | b'\r' => {
// push text to line buffer
// this is used to strip the block formatting:
//
// > [first]: http://example.com "
// > second"
//
// should get turned into `<a href="example.com" title=" second">first</a>`
let linebuf = if let Some(linebuf) = &mut linebuf {
linebuf
} else {
linebuf = Some(String::new());
linebuf.as_mut().unwrap()
};
linebuf.push_str(&text[linestart..bytecount]);
linebuf.push('\n'); // normalize line breaks
// skip line break
bytecount += 1;
if c == b'\r' && bytes.get(bytecount) == Some(&b'\n') {
bytecount += 1;
}
let mut line_start = LineStart::new(&bytes[bytecount..]);
let current_container = scan_containers(
&self.tree,
&mut line_start,
self.options.has_gfm_footnotes(),
) == self.tree.spine_len();
if !line_start.scan_space(4) {
let suffix = &bytes[bytecount + line_start.bytes_scanned()..];
if self.scan_paragraph_interrupt(suffix, current_container)
|| scan_setext_heading(suffix).is_some()
{
return None;
}
}
line_start.scan_all_space();
bytecount += line_start.bytes_scanned();
linestart = bytecount;
if scan_blank_line(&bytes[bytecount..]).is_some() {
// blank line - not allowed
return None;
}
}
b'\\' => {
bytecount += 1;
if let Some(c) = bytes.get(bytecount) {
if c != &b'\r' && c != &b'\n' {
bytecount += 1;
}
}
}
c if c == closing_delim => {
let cow = if let Some(mut linebuf) = linebuf {
linebuf.push_str(&text[linestart..bytecount]);
CowStr::from(linebuf)
} else {
CowStr::from(&text[linestart..bytecount])
};
return Some((bytecount + 1, cow));
}
_ => {
bytecount += 1;
}
}
}
None
}
/// Returns # of bytes and definition.
/// Assumes the label of the reference including colon has already been scanned.
fn scan_refdef(&self, span_start: usize, start: usize) -> Option<(usize, LinkDef<'a>)> {
let bytes = self.text.as_bytes();
// whitespace between label and url (including up to one newline)
let (mut i, _newlines) = self.scan_refdef_space(bytes, start)?;
// scan link dest
let (dest_length, dest) = scan_link_dest(self.text, i, LINK_MAX_NESTED_PARENS)?;
if dest_length == 0 {
return None;
}
let dest = unescape(dest, self.tree.is_in_table());
i += dest_length;
// no title
let mut backup = (
i - start,
LinkDef {
dest,
title: None,
span: span_start..i,
},
);
// scan whitespace between dest and label
let (mut i, newlines) =
if let Some((new_i, mut newlines)) = self.scan_refdef_space(bytes, i) {
if i == self.text.len() {
newlines += 1;
}
if new_i == i && newlines == 0 {
return None;
}
if newlines > 1 {
return Some(backup);
};
(new_i, newlines)
} else {
return Some(backup);
};
// scan title
// if this fails but newline == 1, return also a refdef without title
if let Some((title_length, title)) = self.scan_refdef_title(&self.text[i..]) {
i += title_length;
if scan_blank_line(&bytes[i..]).is_some() {
backup.0 = i - start;
backup.1.span = span_start..i;
backup.1.title = Some(unescape(title, self.tree.is_in_table()));
return Some(backup);
}
}
if newlines > 0 {
Some(backup)
} else {
None
}
}
/// Checks whether we should break a paragraph on the given input.
fn scan_paragraph_interrupt(&self, bytes: &[u8], current_container: bool) -> bool {
let gfm_footnote = self.options.has_gfm_footnotes();
if scan_paragraph_interrupt_no_table(bytes, current_container, gfm_footnote, &self.tree) {
return true;
}
// pulldown-cmark allows heavy tables, that have a `|` on the header row,
// to interrupt paragraphs.
//
// ```markdown
// This is a table
// | a | b | c |
// |---|---|---|
// | d | e | f |
//
// This is not a table
// a | b | c
// ---|---|---
// d | e | f
// ```
if !self.options.contains(Options::ENABLE_TABLES) || !bytes.starts_with(b"|") {
return false;
}
// Checking if something's a valid table or not requires looking at two lines.
// First line, count unescaped pipes.
let mut pipes = 0;
let mut next_line_ix = 0;
let mut bsesc = false;
let mut last_pipe_ix = 0;
for (i, &byte) in bytes.iter().enumerate() {
match byte {
b'\\' => {
bsesc = true;
continue;
}
b'|' if !bsesc => {
pipes += 1;
last_pipe_ix = i;
}
b'\r' | b'\n' => {
next_line_ix = i + scan_eol(&bytes[i..]).unwrap();
break;
}
_ => {}
}
bsesc = false;
}
// scan_eol can't return 0, so this can't be zero
if next_line_ix == 0 {
return false;
}
// Scan the table head. The part that looks like:
//
// |---|---|---|
//
// Also scan any containing items, since it's on its own line, and
// might be nested inside a block quote or something
//
// > Table: First
// > | first col | second col |
// > |-----------|------------|
// ^
// | need to skip over the `>` when checking for the table
let mut line_start = LineStart::new(&bytes[next_line_ix..]);
if scan_containers(
&self.tree,
&mut line_start,
self.options.has_gfm_footnotes(),
) != self.tree.spine_len()
{
return false;
}
let table_head_ix = next_line_ix + line_start.bytes_scanned();
let (table_head_bytes, alignment) = scan_table_head(&bytes[table_head_ix..]);
if table_head_bytes == 0 {
return false;
}
// computing header count from number of pipes
let header_count = count_header_cols(bytes, pipes, 0, last_pipe_ix);
// make sure they match the number of columns we find in separator line
alignment.len() == header_count
}
/// Extracts and parses a heading attribute block if exists.
///
/// Returns `(end_offset_of_heading_content, (id, classes))`.
///
/// If `header_end` is less than or equal to `header_start`, the given
/// input is considered as empty.
fn extract_and_parse_heading_attribute_block(
&mut self,
header_start: usize,
header_end: usize,
) -> (usize, Option<HeadingAttributes<'a>>) {
if !self.options.contains(Options::ENABLE_HEADING_ATTRIBUTES) {
return (header_end, None);
}
// extract the trailing attribute block
let header_bytes = &self.text.as_bytes()[header_start..header_end];
let (content_len, attr_block_range_rel) =
extract_attribute_block_content_from_header_text(header_bytes);
let content_end = header_start + content_len;
let attrs = attr_block_range_rel.and_then(|r| {
parse_inside_attribute_block(
&self.text[(header_start + r.start)..(header_start + r.end)],
)
});
(content_end, attrs)
}
}
/// Scanning modes for `Parser`'s `parse_line` method.
#[derive(PartialEq, Eq, Copy, Clone)]
enum TableParseMode {
/// Inside a paragraph, scanning for table headers.
Scan,
/// Inside a table.
Active,
/// Inside a paragraph, not scanning for table headers.
Disabled,
}
/// Computes the number of header columns in a table line by computing the number of dividing pipes
/// that aren't followed or preceded by whitespace.
fn count_header_cols(
bytes: &[u8],
mut pipes: usize,
mut start: usize,
last_pipe_ix: usize,
) -> usize {
// was first pipe preceded by whitespace? if so, subtract one
start += scan_whitespace_no_nl(&bytes[start..]);
if bytes[start] == b'|' {
pipes -= 1;
}
// was last pipe followed by whitespace? if so, sub one
if scan_blank_line(&bytes[(last_pipe_ix + 1)..]).is_some() {
pipes
} else {
pipes + 1
}
}
/// Checks whether we should break a paragraph on the given input.
///
/// Use `FirstPass::scan_paragraph_interrupt` in any context that allows
/// tables to interrupt the paragraph.
fn scan_paragraph_interrupt_no_table(
bytes: &[u8],
current_container: bool,
gfm_footnote: bool,
tree: &Tree<Item>,
) -> bool {
scan_eol(bytes).is_some()
|| scan_hrule(bytes).is_ok()
|| scan_atx_heading(bytes).is_some()
|| scan_code_fence(bytes).is_some()
|| scan_blockquote_start(bytes).is_some()
|| scan_listitem(bytes).map_or(false, |(ix, delim, index, _)| {
! current_container ||
tree.is_in_table() ||
// we don't allow interruption by either empty lists or
// numbered lists starting at an index other than 1
(delim == b'*' || delim == b'-' || delim == b'+' || index == 1)
&& (scan_blank_line(&bytes[ix..]).is_none())
})
|| bytes.starts_with(b"<")
&& (get_html_end_tag(&bytes[1..]).is_some() || starts_html_block_type_6(&bytes[1..]))
|| (gfm_footnote
&& bytes.starts_with(b"[^")
&& scan_link_label_rest(
std::str::from_utf8(&bytes[2..]).unwrap(),
&|_| None,
tree.is_in_table(),
)
.map_or(false, |(len, _)| bytes.get(2 + len) == Some(&b':')))
}
/// Assumes `text_bytes` is preceded by `<`.
fn get_html_end_tag(text_bytes: &[u8]) -> Option<&'static str> {
static BEGIN_TAGS: &[&[u8]; 4] = &[b"pre", b"style", b"script", b"textarea"];
static ST_BEGIN_TAGS: &[&[u8]; 3] = &[b"!--", b"?", b"![CDATA["];
for (beg_tag, end_tag) in BEGIN_TAGS
.iter()
.zip(["</pre>", "</style>", "</script>", "</textarea>"].iter())
{
let tag_len = beg_tag.len();
if text_bytes.len() < tag_len {
// begin tags are increasing in size
break;
}
if !text_bytes[..tag_len].eq_ignore_ascii_case(beg_tag) {
continue;
}
// Must either be the end of the line...
if text_bytes.len() == tag_len {
return Some(end_tag);
}
// ...or be followed by whitespace, newline, or '>'.
let s = text_bytes[tag_len];
if is_ascii_whitespace(s) || s == b'>' {
return Some(end_tag);
}
}
for (beg_tag, end_tag) in ST_BEGIN_TAGS.iter().zip(["-->", "?>", "]]>"].iter()) {
if text_bytes.starts_with(beg_tag) {
return Some(end_tag);
}
}
if text_bytes.len() > 1 && text_bytes[0] == b'!' && text_bytes[1].is_ascii_alphabetic() {
Some(">")
} else {
None
}
}
// https://english.stackexchange.com/a/285573
fn surgerize_tight_list(tree: &mut Tree<Item>, list_ix: TreeIndex) {
let mut list_item = tree[list_ix].child;
while let Some(listitem_ix) = list_item {
// first child is special, controls how we repoint list_item.child
let list_item_firstborn = tree[listitem_ix].child;
// Check that list item has children - this is not necessarily the case!
if let Some(firstborn_ix) = list_item_firstborn {
if let ItemBody::Paragraph = tree[firstborn_ix].item.body {
tree[listitem_ix].child = tree[firstborn_ix].child;
}
let mut list_item_child = Some(firstborn_ix);
let mut node_to_repoint = None;
while let Some(child_ix) = list_item_child {
// surgerize paragraphs
let repoint_ix = if let ItemBody::Paragraph = tree[child_ix].item.body {
if let Some(child_firstborn) = tree[child_ix].child {
if let Some(repoint_ix) = node_to_repoint {
tree[repoint_ix].next = Some(child_firstborn);
}
let mut child_lastborn = child_firstborn;
while let Some(lastborn_next_ix) = tree[child_lastborn].next {
child_lastborn = lastborn_next_ix;
}
child_lastborn
} else {
child_ix
}
} else {
child_ix
};
node_to_repoint = Some(repoint_ix);
tree[repoint_ix].next = tree[child_ix].next;
list_item_child = tree[child_ix].next;
}
}
list_item = tree[listitem_ix].next;
}
}
/// Determines whether the delimiter run starting at given index is
/// left-flanking, as defined by the commonmark spec (and isn't intraword
/// for _ delims).
/// suffix is &s[ix..], which is passed in as an optimization, since taking
/// a string subslice is O(n).
fn delim_run_can_open(
s: &str,
suffix: &str,
run_len: usize,
ix: usize,
mode: TableParseMode,
) -> bool {
let next_char = if let Some(c) = suffix.chars().nth(run_len) {
c
} else {
return false;
};
if next_char.is_whitespace() {
return false;
}
if ix == 0 {
return true;
}
if mode == TableParseMode::Active {
if s[..ix].ends_with('|') && !s[..ix].ends_with(r"\|") {
return true;
}
if next_char == '|' {
return false;
}
}
let delim = suffix.chars().next().unwrap();
// `*` and `~~` can be intraword, `_` and `~` cannot
if delim == '*' && !is_punctuation(next_char) {
return true;
}
if delim == '~' && run_len > 1 {
return true;
}
let prev_char = s[..ix].chars().last().unwrap();
if delim == '~' && prev_char == '~' && !is_punctuation(next_char) {
return true;
}
prev_char.is_whitespace()
|| is_punctuation(prev_char) && (delim != '\'' || ![']', ')'].contains(&prev_char))
}
/// Determines whether the delimiter run starting at given index is
/// right-flanking, as defined by the commonmark spec (and isn't intraword
/// for _ delims)
fn delim_run_can_close(
s: &str,
suffix: &str,
run_len: usize,
ix: usize,
mode: TableParseMode,
) -> bool {
if ix == 0 {
return false;
}
let prev_char = s[..ix].chars().last().unwrap();
if prev_char.is_whitespace() {
return false;
}
let next_char = if let Some(c) = suffix.chars().nth(run_len) {
c
} else {
return true;
};
if mode == TableParseMode::Active {
if s[..ix].ends_with('|') && !s[..ix].ends_with(r"\|") {
return false;
}
if next_char == '|' {
return true;
}
}
let delim = suffix.chars().next().unwrap();
// `*` and `~~` can be intraword, `_` and `~` cannot
if (delim == '*' || (delim == '~' && run_len > 1)) && !is_punctuation(prev_char) {
return true;
}
if delim == '~' && prev_char == '~' {
return true;
}
next_char.is_whitespace() || is_punctuation(next_char)
}
fn create_lut(options: &Options) -> LookupTable {
#[cfg(all(target_arch = "x86_64", feature = "simd"))]
{
LookupTable {
simd: simd::compute_lookup(options),
scalar: special_bytes(options),
}
}
#[cfg(not(all(target_arch = "x86_64", feature = "simd")))]
{
special_bytes(options)
}
}
fn special_bytes(options: &Options) -> [bool; 256] {
let mut bytes = [false; 256];
let standard_bytes = [
b'\n', b'\r', b'*', b'_', b'&', b'\\', b'[', b']', b'<', b'!', b'`',
];
for &byte in &standard_bytes {
bytes[byte as usize] = true;
}
if options.contains(Options::ENABLE_TABLES) {
bytes[b'|' as usize] = true;
}
if options.contains(Options::ENABLE_STRIKETHROUGH) {
bytes[b'~' as usize] = true;
}
if options.contains(Options::ENABLE_MATH) {
bytes[b'$' as usize] = true;
bytes[b'{' as usize] = true;
bytes[b'}' as usize] = true;
}
if options.contains(Options::ENABLE_SMART_PUNCTUATION) {
for &byte in &[b'.', b'-', b'"', b'\''] {
bytes[byte as usize] = true;
}
}
bytes
}
enum LoopInstruction<T> {
/// Continue looking for more special bytes, but skip next few bytes.
ContinueAndSkip(usize),
/// Break looping immediately, returning with the given index and value.
BreakAtWith(usize, T),
}
#[cfg(all(target_arch = "x86_64", feature = "simd"))]
struct LookupTable {
simd: [u8; 16],
scalar: [bool; 256],
}
#[cfg(not(all(target_arch = "x86_64", feature = "simd")))]
type LookupTable = [bool; 256];
/// This function walks the byte slices from the given index and
/// calls the callback function on all bytes (and their indices) that are in the following set:
/// `` ` ``, `\`, `&`, `*`, `_`, `~`, `!`, `<`, `[`, `]`, `|`, `\r`, `\n`
/// It is guaranteed not call the callback on other bytes.
/// Whenever `callback(ix, byte)` returns a `ContinueAndSkip(n)` value, the callback
/// will not be called with an index that is less than `ix + n + 1`.
/// When the callback returns a `BreakAtWith(end_ix, opt+val)`, no more callbacks will be
/// called and the function returns immediately with the return value `(end_ix, opt_val)`.
/// If `BreakAtWith(..)` is never returned, this function will return the first
/// index that is outside the byteslice bound and a `None` value.
fn iterate_special_bytes<F, T>(
lut: &LookupTable,
bytes: &[u8],
ix: usize,
callback: F,
) -> (usize, Option<T>)
where
F: FnMut(usize, u8) -> LoopInstruction<Option<T>>,
{
#[cfg(all(target_arch = "x86_64", feature = "simd"))]
{
simd::iterate_special_bytes(lut, bytes, ix, callback)
}
#[cfg(not(all(target_arch = "x86_64", feature = "simd")))]
{
scalar_iterate_special_bytes(lut, bytes, ix, callback)
}
}
fn scalar_iterate_special_bytes<F, T>(
lut: &[bool; 256],
bytes: &[u8],
mut ix: usize,
mut callback: F,
) -> (usize, Option<T>)
where
F: FnMut(usize, u8) -> LoopInstruction<Option<T>>,
{
while ix < bytes.len() {
let b = bytes[ix];
if lut[b as usize] {
match callback(ix, b) {
LoopInstruction::ContinueAndSkip(skip) => {
ix += skip;
}
LoopInstruction::BreakAtWith(ix, val) => {
return (ix, val);
}
}
}
ix += 1;
}
(ix, None)
}
/// Split the usual heading content range and the content inside the trailing attribute block.
///
/// Returns `(leading_content_len, Option<trailing_attr_block_range>)`.
///
/// Note that `trailing_attr_block_range` will be empty range when the block
/// is `{}`, since the range is content inside the wrapping `{` and `}`.
///
/// The closing `}` of an attribute block can have trailing whitespaces.
/// They are automatically trimmed when the attribute block is being searched.
///
/// However, this method does not trim the trailing whitespaces of heading content.
/// It is callers' responsibility to trim them if necessary.
fn extract_attribute_block_content_from_header_text(
heading: &[u8],
) -> (usize, Option<Range<usize>>) {
let heading_len = heading.len();
let mut ix = heading_len;
ix -= scan_rev_while(heading, |b| {
b == b'\n' || b == b'\r' || b == b' ' || b == b'\t'
});
if ix == 0 {
return (heading_len, None);
}
let attr_block_close = ix - 1;
if heading.get(attr_block_close) != Some(&b'}') {
// The last character is not `}`. No attribute blocks found.
return (heading_len, None);
}
// move cursor before the closing right brace (`}`)
ix -= 1;
ix -= scan_rev_while(&heading[..ix], |b| {
// Characters to be excluded:
// * `{` and `}`: special characters to open and close an attribute block.
// * `\\`: a special character to escape many characters and disable some syntaxes.
// + Handling of this escape character differs among markdown processors.
// + Escaped characters will be separate text node from neighbors, so
// it is not easy to handle unescaped string and trim the trailing block.
// * `<` and `>`: special characters to start and end HTML tag.
// + No known processors converts `{#<i>foo</i>}` into
// `id="&lt;i&gt;foo&lt;/&gt;"` as of this writing, so hopefully
// this restriction won't cause compatibility issues.
// * `\n` and `\r`: a newline character.
// + Setext heading can have multiple lines. However it is hard to support
// attribute blocks that have newline inside, since the parsing proceeds line by
// line and lines will be separate nodes even they are logically a single text.
!matches!(b, b'{' | b'}' | b'<' | b'>' | b'\\' | b'\n' | b'\r')
});
if ix == 0 {
// `{` is not found. No attribute blocks available.
return (heading_len, None);
}
let attr_block_open = ix - 1;
if heading[attr_block_open] != b'{' {
// `{` is not found. No attribute blocks available.
return (heading_len, None);
}
(attr_block_open, Some(ix..attr_block_close))
}
/// Parses an attribute block content, such as `.class1 #id .class2`.
///
/// Returns `(id, classes)`.
///
/// It is callers' responsibility to find opening and closing characters of the attribute
/// block. Usually [`extract_attribute_block_content_from_header_text`] function does it for you.
///
/// Note that this parsing requires explicit whitespace separators between
/// attributes. This is intentional design with the reasons below:
///
/// * to keep conversion simple and easy to understand for any possible input,
/// * to avoid adding less obvious conversion rule that can reduce compatibility
/// with other implementations more, and
/// * to follow the major design of implementations with the support for the
/// attribute blocks extension (as of this writing).
///
/// See also: [`Options::ENABLE_HEADING_ATTRIBUTES`].
///
/// [`Options::ENABLE_HEADING_ATTRIBUTES`]: `crate::Options::ENABLE_HEADING_ATTRIBUTES`
fn parse_inside_attribute_block(inside_attr_block: &str) -> Option<HeadingAttributes<'_>> {
let mut id = None;
let mut classes = Vec::new();
let mut attrs = Vec::new();
for attr in inside_attr_block.split_ascii_whitespace() {
// iterator returned by `str::split_ascii_whitespace` never emits empty
// strings, so taking first byte won't panic.
if attr.len() > 1 {
let first_byte = attr.as_bytes()[0];
if first_byte == b'#' {
id = Some(attr[1..].into());
} else if first_byte == b'.' {
classes.push(attr[1..].into());
} else {
let split = attr.split_once('=');
if let Some((key, value)) = split {
attrs.push((key.into(), Some(value.into())));
} else {
attrs.push((attr.into(), None));
}
}
}
}
Some(HeadingAttributes { id, classes, attrs })
}
#[cfg(all(target_arch = "x86_64", feature = "simd"))]
mod simd {
//! SIMD byte scanning logic.
//!
//! This module provides functions that allow walking through byteslices, calling
//! provided callback functions on special bytes and their indices using SIMD.
//! The byteset is defined in `compute_lookup`.
//!
//! The idea is to load in a chunk of 16 bytes and perform a lookup into a set of
//! bytes on all the bytes in this chunk simultaneously. We produce a 16 bit bitmask
//! from this and call the callback on every index corresponding to a 1 in this mask
//! before moving on to the next chunk. This allows us to move quickly when there
//! are no or few matches.
//!
//! The table lookup is inspired by this [great overview]. However, since all of the
//! bytes we're interested in are ASCII, we don't quite need the full generality of
//! the universal algorithm and are hence able to skip a few instructions.
//!
//! [great overview]: http://0x80.pl/articles/simd-byte-lookup.html
use super::{LookupTable, LoopInstruction};
use crate::Options;
use core::arch::x86_64::*;
const VECTOR_SIZE: usize = std::mem::size_of::<__m128i>();
/// Generates a lookup table containing the bitmaps for our
/// special marker bytes. This is effectively a 128 element 2d bitvector,
/// that can be indexed by a four bit row index (the lower nibble)
/// and a three bit column index (upper nibble).
pub(super) fn compute_lookup(options: &Options) -> [u8; 16] {
let mut lookup = [0u8; 16];
let standard_bytes = [
b'\n', b'\r', b'*', b'_', b'&', b'\\', b'[', b']', b'<', b'!', b'`',
];
for &byte in &standard_bytes {
add_lookup_byte(&mut lookup, byte);
}
if options.contains(Options::ENABLE_TABLES) {
add_lookup_byte(&mut lookup, b'|');
}
if options.contains(Options::ENABLE_STRIKETHROUGH) {
add_lookup_byte(&mut lookup, b'~');
}
if options.contains(Options::ENABLE_MATH) {
add_lookup_byte(&mut lookup, b'$');
add_lookup_byte(&mut lookup, b'{');
add_lookup_byte(&mut lookup, b'}');
}
if options.contains(Options::ENABLE_SMART_PUNCTUATION) {
for &byte in &[b'.', b'-', b'"', b'\''] {
add_lookup_byte(&mut lookup, byte);
}
}
lookup
}
fn add_lookup_byte(lookup: &mut [u8; 16], byte: u8) {
lookup[(byte & 0x0f) as usize] |= 1 << (byte >> 4);
}
/// Computes a bit mask for the given byteslice starting from the given index,
/// where the 16 least significant bits indicate (by value of 1) whether or not
/// there is a special character at that byte position. The least significant bit
/// corresponds to `bytes[ix]` and the most significant bit corresponds to
/// `bytes[ix + 15]`.
/// It is only safe to call this function when `bytes.len() >= ix + VECTOR_SIZE`.
#[target_feature(enable = "ssse3")]
#[inline]
unsafe fn compute_mask(lut: &[u8; 16], bytes: &[u8], ix: usize) -> i32 {
debug_assert!(bytes.len() >= ix + VECTOR_SIZE);
let bitmap = _mm_loadu_si128(lut.as_ptr() as *const __m128i);
// Small lookup table to compute single bit bitshifts
// for 16 bytes at once.
let bitmask_lookup =
_mm_setr_epi8(1, 2, 4, 8, 16, 32, 64, -128, -1, -1, -1, -1, -1, -1, -1, -1);
// Load input from memory.
let raw_ptr = bytes.as_ptr().add(ix) as *const __m128i;
let input = _mm_loadu_si128(raw_ptr);
// Compute the bitmap using the bottom nibble as an index
// into the lookup table. Note that non-ascii bytes will have
// their most significant bit set and will map to lookup[0].
let bitset = _mm_shuffle_epi8(bitmap, input);
// Compute the high nibbles of the input using a 16-bit rightshift of four
// and a mask to prevent most-significant bit issues.
let higher_nibbles = _mm_and_si128(_mm_srli_epi16(input, 4), _mm_set1_epi8(0x0f));
// Create a bitmask for the bitmap by perform a left shift of the value
// of the higher nibble. Bytes with their most significant set are mapped
// to -1 (all ones).
let bitmask = _mm_shuffle_epi8(bitmask_lookup, higher_nibbles);
// Test the bit of the bitmap by AND'ing the bitmap and the mask together.
let tmp = _mm_and_si128(bitset, bitmask);
// Check whether the result was not null. NEQ is not a SIMD intrinsic,
// but comparing to the bitmask is logically equivalent. This also prevents us
// from matching any non-ASCII bytes since none of the bitmaps were all ones
// (-1).
let result = _mm_cmpeq_epi8(tmp, bitmask);
// Return the resulting bitmask.
_mm_movemask_epi8(result)
}
/// Calls callback on byte indices and their value.
/// Breaks when callback returns LoopInstruction::BreakAtWith(ix, val). And skips the
/// number of bytes in callback return value otherwise.
/// Returns the final index and a possible break value.
pub(super) fn iterate_special_bytes<F, T>(
lut: &LookupTable,
bytes: &[u8],
ix: usize,
callback: F,
) -> (usize, Option<T>)
where
F: FnMut(usize, u8) -> LoopInstruction<Option<T>>,
{
if is_x86_feature_detected!("ssse3") && bytes.len() >= VECTOR_SIZE {
unsafe { simd_iterate_special_bytes(&lut.simd, bytes, ix, callback) }
} else {
super::scalar_iterate_special_bytes(&lut.scalar, bytes, ix, callback)
}
}
/// Calls the callback function for every 1 in the given bitmask with
/// the index `offset + ix`, where `ix` is the position of the 1 in the mask.
/// Returns `Ok(ix)` to continue from index `ix`, `Err((end_ix, opt_val)` to break with
/// final index `end_ix` and optional value `opt_val`.
unsafe fn process_mask<F, T>(
mut mask: i32,
bytes: &[u8],
mut offset: usize,
callback: &mut F,
) -> Result<usize, (usize, Option<T>)>
where
F: FnMut(usize, u8) -> LoopInstruction<Option<T>>,
{
while mask != 0 {
let mask_ix = mask.trailing_zeros() as usize;
offset += mask_ix;
match callback(offset, *bytes.get_unchecked(offset)) {
LoopInstruction::ContinueAndSkip(skip) => {
offset += skip + 1;
mask = mask.wrapping_shr((skip + 1 + mask_ix) as u32);
}
LoopInstruction::BreakAtWith(ix, val) => return Err((ix, val)),
}
}
Ok(offset)
}
#[target_feature(enable = "ssse3")]
/// Important: only call this function when `bytes.len() >= 16`. Doing
/// so otherwise may exhibit undefined behaviour.
unsafe fn simd_iterate_special_bytes<F, T>(
lut: &[u8; 16],
bytes: &[u8],
mut ix: usize,
mut callback: F,
) -> (usize, Option<T>)
where
F: FnMut(usize, u8) -> LoopInstruction<Option<T>>,
{
debug_assert!(bytes.len() >= VECTOR_SIZE);
let upperbound = bytes.len() - VECTOR_SIZE;
while ix < upperbound {
let mask = compute_mask(lut, bytes, ix);
let block_start = ix;
ix = match process_mask(mask, bytes, ix, &mut callback) {
Ok(ix) => std::cmp::max(ix, VECTOR_SIZE + block_start),
Err((end_ix, val)) => return (end_ix, val),
};
}
if bytes.len() > ix {
// shift off the bytes at start we have already scanned
let mask = compute_mask(lut, bytes, upperbound) >> ix - upperbound;
if let Err((end_ix, val)) = process_mask(mask, bytes, ix, &mut callback) {
return (end_ix, val);
}
}
(bytes.len(), None)
}
#[cfg(test)]
mod simd_test {
use super::super::create_lut;
use super::{iterate_special_bytes, LoopInstruction};
use crate::Options;
fn check_expected_indices(bytes: &[u8], expected: &[usize], skip: usize) {
let mut opts = Options::empty();
opts.insert(Options::ENABLE_MATH);
opts.insert(Options::ENABLE_TABLES);
opts.insert(Options::ENABLE_FOOTNOTES);
opts.insert(Options::ENABLE_STRIKETHROUGH);
opts.insert(Options::ENABLE_TASKLISTS);
let lut = create_lut(&opts);
let mut indices = vec![];
iterate_special_bytes::<_, i32>(&lut, bytes, 0, |ix, _byte_ty| {
indices.push(ix);
LoopInstruction::ContinueAndSkip(skip)
});
assert_eq!(&indices[..], expected);
}
#[test]
fn simple_no_match() {
check_expected_indices("abcdef0123456789".as_bytes(), &[], 0);
}
#[test]
fn simple_match() {
check_expected_indices("*bcd&f0123456789".as_bytes(), &[0, 4], 0);
}
#[test]
fn single_open_fish() {
check_expected_indices("<".as_bytes(), &[0], 0);
}
#[test]
fn long_match() {
check_expected_indices("0123456789abcde~*bcd&f0".as_bytes(), &[15, 16, 20], 0);
}
#[test]
fn border_skip() {
check_expected_indices("0123456789abcde~~~~d&f0".as_bytes(), &[15, 20], 3);
}
#[test]
fn exhaustive_search() {
let chars = [
b'\n', b'\r', b'*', b'_', b'~', b'|', b'&', b'\\', b'[', b']', b'<', b'!', b'`',
b'$', b'{', b'}',
];
for &c in &chars {
for i in 0u8..=255 {
if !chars.contains(&i) {
// full match
let mut buf = [i; 18];
buf[3] = c;
buf[6] = c;
check_expected_indices(&buf[..], &[3, 6], 0);
}
}
}
}
}
}