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path: root/src/stdio/__stdio_read.c
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2012-05-25avoid using pthread cleanup push/pop in stdio when not neededRich Felker1-3/+7
unfortunately in dynamic-linked programs, these macros cause pthread_self to be initialized, which costs a couple syscalls, and (much worse) would necessarily fail, crash, and burn on ancient (2.4 and earlier) kernels where setting up a thread pointer does not work. i'd like to do this in a more generic way that avoids all use of cleanup push/pop before pthread_self has been successfully called and avoids ugly if/else constructs like the one in this commit, but for now, this will suffice.
2012-02-02make stdio open, read, and write operations cancellation pointsRich Felker1-1/+10
it should be noted that only the actual underlying buffer flush and fill operations are cancellable, not reads from or writes to the buffer. this behavior is compatible with POSIX, which makes all cancellation points in stdio optional, and it achieves the goal of allowing cancellation of a thread that's "stuck" on IO (due to a non-responsive socket/pipe peer, slow/stuck hardware, etc.) without imposing any measurable performance cost.
2011-04-09work around a nasty bug in linux readv syscallRich Felker1-3/+4
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.
2011-03-28major stdio overhaul, using readv/writev, plus other changesRich Felker1-1/+17
the biggest change in this commit is that stdio now uses readv to fill the caller's buffer and the FILE buffer with a single syscall, and likewise writev to flush the FILE buffer and write out the caller's buffer in a single syscall. making this change required fundamental architectural changes to stdio, so i also made a number of other improvements in the process: - the implementation no longer assumes that further io will fail following errors, and no longer blocks io when the error flag is set (though the latter could easily be changed back if desired) - unbuffered mode is no longer implemented as a one-byte buffer. as a consequence, scanf unreading has to use ungetc, to the unget buffer has been enlarged to hold at least 2 wide characters. - the FILE structure has been rearranged to maintain the locations of the fields that might be used in glibc getc/putc type macros, while shrinking the structure to save some space. - error cases for fflush, fseek, etc. should be more correct. - library-internal macros are used for getc_unlocked and putc_unlocked now, eliminating some ugly code duplication. __uflow and __overflow are no longer used anywhere but these macros. switch to read or write mode is also separated so the code can be better shared, e.g. with ungetc. - lots of other small things.
2011-03-20global cleanup to use the new syscall interfaceRich Felker1-1/+1
2011-02-12initial check-in, version 0.5.0v0.5.0Rich Felker1-0/+6