RepoMirrors/musl
1
0
Fork 0
mirror of git://git.musl-libc.org/musl synced 2024-12-17 12:14:42 +00:00
Code Issues Packages Projects Releases Wiki Activity

work around a nasty bug in linux readv syscall

Browse Source 
according to posix, readv "shall be equivalent to read(), except..."
that it places the data into the buffers specified by the iov array.
however on linux, when reading from a terminal, each iov element
behaves almost like a separate read. this means that if the first iov
exactly satisfied the request (e.g. a length-one read of '\n') and the
second iov is nonzero length, the syscall will block again after
getting the blank line from the terminal until another line is read.
simply put, entering a single blank line becomes impossible.

the solution, fortunately, is simple. whenever the buffer size is
nonzero, reduce the length of the requested read by one byte and let
the last byte go through the buffer. this way, readv will already be
in the second (and last) iov, and won't re-block on the second iov.
This commit is contained in:
Rich Felker 2011-04-09 01:17:55 -04:00
parent 67e793e5e1
commit 2cff36a84f
1 changed files with 4 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
src/stdio/__stdio_read.c
View File

@ -3,7 +3,7 @@
size_t __stdio_read(FILE *f, unsigned char *buf, size_t len)
{
struct iovec iov[2] = {
{ .iov_base = buf, .iov_len = len },
{ .iov_base = buf, .iov_len = len - !!f->buf_size },
{ .iov_base = f->buf, .iov_len = f->buf_size }
};
ssize_t cnt;
@ -14,9 +14,10 @@ size_t __stdio_read(FILE *f, unsigned char *buf, size_t len)
f->rpos = f->rend = 0;
return cnt;
}
if (cnt <= len) return cnt;
cnt -= len;
if (cnt <= iov[0].iov_len) return cnt;
cnt -= iov[0].iov_len;
f->rpos = f->buf;
f->rend = f->buf + cnt;
if (f->buf_size) buf[len-1] = *f->rpos++;
return len;
}