src/hb-subset.cc

/*
 * Copyright © 2018  Google, Inc.
 *
 *  This is part of HarfBuzz, a text shaping library.
 *
 * Permission is hereby granted, without written agreement and without
 * license or royalty fees, to use, copy, modify, and distribute this
 * software and its documentation for any purpose, provided that the
 * above copyright notice and the following two paragraphs appear in
 * all copies of this software.
 *
 * IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR
 * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
 * ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN
 * IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
 * DAMAGE.
 *
 * THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,
 * BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
 * FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
 * ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO
 * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
 *
 * Google Author(s): Garret Rieger, Rod Sheeter, Behdad Esfahbod
 */

#include "hb-object-private.hh"
#include "hb-open-type-private.hh"

#include "hb-subset-glyf.hh"
#include "hb-subset-private.hh"
#include "hb-subset-plan.hh"

#include "hb-open-file-private.hh"
#include "hb-ot-cmap-table.hh"
#include "hb-ot-glyf-table.hh"


#ifndef HB_NO_VISIBILITY
const void * const OT::_hb_NullPool[HB_NULL_POOL_SIZE / sizeof (void *)] = {};
#endif


struct hb_subset_profile_t {
  hb_object_header_t header;
  ASSERT_POD ();
};

/**
 * hb_subset_profile_create:
 *
 * Return value: New profile with default settings.
 *
 * Since: 1.8.0
 **/
hb_subset_profile_t *
hb_subset_profile_create ()
{
  return hb_object_create<hb_subset_profile_t>();
}

/**
 * hb_subset_profile_destroy:
 *
 * Since: 1.8.0
 **/
void
hb_subset_profile_destroy (hb_subset_profile_t *profile)
{
  if (!hb_object_destroy (profile)) return;

  free (profile);
}

template<typename TableType>
static hb_blob_t *
_subset (hb_subset_plan_t *plan, hb_face_t *source)
{
    OT::Sanitizer<TableType> sanitizer;
    hb_blob_t *source_blob = sanitizer.sanitize (source->reference_table (TableType::tableTag));
    const TableType *table = OT::Sanitizer<TableType>::lock_instance (source_blob);
    hb_blob_t *result = table->subset(plan, source);

    hb_blob_destroy (source_blob);

    hb_tag_t tag = TableType::tableTag;
    DEBUG_MSG(SUBSET, nullptr, "Subset %c%c%c%c %s", HB_UNTAG(tag), result ? "success" : "FAILED!");
    return result;
}


/*
 * A face that has add_table().
 */

struct hb_subset_face_data_t
{
  struct table_entry_t
  {
    inline int cmp (const hb_tag_t *t) const
    {
      if (*t < tag) return -1;
      if (*t > tag) return -1;
      return 0;
    }

    hb_tag_t   tag;
    hb_blob_t *blob;
  };

  hb_prealloced_array_t<table_entry_t, 32> tables;
};

static hb_subset_face_data_t *
_hb_subset_face_data_create (void)
{
  hb_subset_face_data_t *data = (hb_subset_face_data_t *) calloc (1, sizeof (hb_subset_face_data_t));
  if (unlikely (!data))
    return nullptr;

  return data;
}

static void
_hb_subset_face_data_destroy (void *user_data)
{
  hb_subset_face_data_t *data = (hb_subset_face_data_t *) user_data;

  data->tables.finish ();

  free (data);
}

static hb_blob_t *
_hb_subset_face_data_reference_blob (hb_subset_face_data_t *data)
{

  unsigned int table_count = data->tables.len;
  unsigned int face_length = table_count * 16 + 12;

  for (unsigned int i = 0; i < table_count; i++)
    face_length += _hb_ceil_to_4 (hb_blob_get_length (data->tables.array[i].blob));

  char *buf = (char *) malloc (face_length);
  if (unlikely (!buf))
    return nullptr;

  OT::hb_serialize_context_t c (buf, face_length);
  OT::OpenTypeFontFile *f = c.start_serialize<OT::OpenTypeFontFile> ();

  bool is_cff = data->tables.lsearch (HB_TAG ('C','F','F',' ')) || data->tables.lsearch (HB_TAG ('C','F','F','2'));
  hb_tag_t sfnt_tag = is_cff ? OT::OpenTypeFontFile::CFFTag : OT::OpenTypeFontFile::TrueTypeTag;

  OT::Supplier<hb_tag_t>    tags_supplier  (&data->tables[0].tag, table_count, sizeof (data->tables[0]));
  OT::Supplier<hb_blob_t *> blobs_supplier (&data->tables[0].blob, table_count, sizeof (data->tables[0]));
  bool ret = f->serialize_single (&c,
				  sfnt_tag,
				  tags_supplier,
				  blobs_supplier,
				  table_count);

  c.end_serialize ();

  if (unlikely (!ret))
  {
    free (buf);
    return nullptr;
  }

  return hb_blob_create (buf, face_length, HB_MEMORY_MODE_WRITABLE, buf, free);
}

static hb_blob_t *
_hb_subset_face_reference_table (hb_face_t *face, hb_tag_t tag, void *user_data)
{
  hb_subset_face_data_t *data = (hb_subset_face_data_t *) user_data;

  if (!tag)
    return _hb_subset_face_data_reference_blob (data);

  hb_subset_face_data_t::table_entry_t *entry = data->tables.lsearch (tag);
  if (entry)
    return hb_blob_reference (entry->blob);

  return nullptr;
}

static hb_face_t *
hb_subset_face_create (void)
{
  hb_subset_face_data_t *data = _hb_subset_face_data_create ();
  if (unlikely (!data)) return hb_face_get_empty ();

  return hb_face_create_for_tables (_hb_subset_face_reference_table,
				    data,
				    _hb_subset_face_data_destroy);
}

static bool
hb_subset_face_add_table (hb_face_t *face, hb_tag_t tag, hb_blob_t *blob)
{
  if (unlikely (face->destroy != _hb_subset_face_data_destroy))
    return false;

  hb_subset_face_data_t *data = (hb_subset_face_data_t *) face->user_data;
  hb_subset_face_data_t::table_entry_t *entry = data->tables.push ();
  if (unlikely (!entry))
    return false;

  entry->tag = tag;
  entry->blob = hb_blob_reference (blob);

  return true;
}

static bool
_add_head_and_set_loca_version (hb_face_t *source, bool use_short_loca, hb_face_t *dest)
{
  hb_blob_t *head_blob = OT::Sanitizer<OT::head>().sanitize (hb_face_reference_table (source, HB_OT_TAG_head));
  const OT::head *head = OT::Sanitizer<OT::head>::lock_instance (head_blob);
  bool has_head = (head != nullptr);

  if (has_head) {
    OT::head *head_prime = (OT::head *) calloc (OT::head::static_size, 1);
    memcpy (head_prime, head, OT::head::static_size);
    head_prime->indexToLocFormat.set (use_short_loca ? 0 : 1);

    hb_blob_t *head_prime_blob = hb_blob_create ((const char*) head_prime,
                                                 OT::head::static_size,
                                                 HB_MEMORY_MODE_WRITABLE,
                                                 head_prime,
                                                 free);
    has_head = has_head && hb_subset_face_add_table (dest, HB_OT_TAG_head, head_prime_blob);

    hb_blob_destroy (head_prime_blob);
  }

  hb_blob_destroy (head_blob);

  return has_head;
}

static bool
_subset_glyf (hb_subset_plan_t *plan, hb_face_t *source, hb_face_t *dest)
{
  hb_blob_t *glyf_prime = nullptr;
  hb_blob_t *loca_prime = nullptr;

  bool success = true;
  bool use_short_loca = false;
  // TODO(grieger): Migrate to subset function on the table like cmap.
  if (hb_subset_glyf_and_loca (plan, source, &use_short_loca, &glyf_prime, &loca_prime)) {
    success = success && hb_subset_face_add_table (dest, HB_OT_TAG_glyf, glyf_prime);
    success = success && hb_subset_face_add_table (dest, HB_OT_TAG_loca, loca_prime);
    success = success && _add_head_and_set_loca_version (source, use_short_loca, dest);
  } else {
    success = false;
  }
  hb_blob_destroy (loca_prime);
  hb_blob_destroy (glyf_prime);

  return success;
}

static bool
_subset_table (hb_subset_plan_t *plan,
               hb_face_t        *source,
               hb_tag_t          tag,
               hb_blob_t        *source_blob,
               hb_face_t        *dest)
{
  // TODO (grieger): Handle updating the head table (loca format + num glyphs)
  DEBUG_MSG(SUBSET, nullptr, "begin subset %c%c%c%c", HB_UNTAG(tag));
  hb_blob_t *dest_blob;
  switch (tag) {
    case HB_OT_TAG_glyf:
      return _subset_glyf (plan, source, dest);
    case HB_OT_TAG_head:
      // SKIP head, it's handled by glyf
      return true;
    case HB_OT_TAG_loca:
      // SKIP loca, it's handle by glyf
      return true;
    case HB_OT_TAG_cmap:
      dest_blob = _subset<const OT::cmap> (plan, source);
      break;
    default:
      dest_blob = source_blob;
      break;
  } 
  DEBUG_MSG(SUBSET, nullptr, "subset %c%c%c%c %s", HB_UNTAG(tag), dest_blob ? "ok" : "FAILED");
  if (unlikely(!dest_blob)) return false;
  if (unlikely(!hb_subset_face_add_table (dest, tag, dest_blob))) return false;
  return true;
}

/**
 * hb_subset:
 * @source: font face data to be subset.
 * @profile: profile to use for the subsetting.
 * @input: input to use for the subsetting.
 *
 * Subsets a font according to provided profile and input.
 **/
hb_face_t *
hb_subset (hb_face_t *source,
	   hb_subset_profile_t *profile,
           hb_subset_input_t *input)
{
  if (unlikely (!profile || !input || !source)) return hb_face_get_empty();

  hb_subset_plan_t *plan = hb_subset_plan_create (source, profile, input);

  hb_face_t *dest = hb_subset_face_create ();
  hb_tag_t table_tags[32];
  unsigned int offset = 0, count;
  bool success = true;
  do {
    count = ARRAY_LENGTH (table_tags);
    hb_face_get_table_tags (source, offset, &count, table_tags);
    for (unsigned int i = 0; i < count; i++)
    {
      hb_tag_t tag = table_tags[i];
      hb_blob_t *blob = hb_face_reference_table (source, tag);
      success = success && _subset_table (plan, source, tag, blob, dest);
      hb_blob_destroy (blob);
    }
  } while (count == ARRAY_LENGTH (table_tags));

  // TODO(grieger): Remove once basic subsetting is working + tests updated.
  hb_face_destroy (dest);
  return success ? hb_face_reference (source) : hb_face_get_empty ();
}