Os: add ReceiveDatagram
Add a wrapper for recv(), which reads one datagram
from a socket. Add unit tests for the same.
While there:
- add NONNULL annotation to the |buf| argument of
Os::Write()
- add some more tests for Os::Write()
- replace an instance of EBADFD with EBADF
(the two errors are not necessarily the same,
and the documentation for write() talks about
EBADF, not EBADFD.)
- remove unnecessary ON_CALL in a test
(in WriteWithOverlyLargeBufferCausesDeath,
we expect to abort before calling RawOs::Write())
Bug: 32447384
Test: ./runtests.sh (on angler)
Change-Id: I1a8b7e94d415d5f63a2ccc842d292c6c65b85b09
diff --git a/os.cpp b/os.cpp
index d437066..ae8caca 100644
--- a/os.cpp
+++ b/os.cpp
@@ -58,6 +58,25 @@
return now_timestamp;
}
+std::tuple<size_t, Os::Errno> Os::ReceiveDatagram(int fd, void* buf,
+ size_t buflen) {
+ // recv() takes a size_t, but returns an ssize_t. That means that the largest
+ // successful read that recv() can report is the maximal ssize_t. Passing a
+ // larger |buflen| risks mistakenly reporting a truncated read.
+ CHECK(buflen <= GetMaxVal<ssize_t>());
+
+ const ssize_t res = raw_os_->Recv(fd, buf, buflen, MSG_TRUNC);
+ if (res < 0) {
+ return {0, errno};
+ }
+
+ // Due to the MSG_TRUNC flag, |res| may reasonably be larger than
+ // |buflen|. In such cases, |res| indicates the full size of the datagram,
+ // before being truncated to fit our buffer. Hence, we omit the
+ // buffer-overflow CHECK that exists in Write().
+ return {res, 0};
+}
+
std::tuple<size_t, Os::Errno> Os::Write(int fd, const void* buf,
size_t buflen) {
// write() takes a size_t, but returns an ssize_t. That means that the
