getc_unlocked¶

Synopsis¶

#include <stdio.h>

int getc_unlocked(FILE *stream);

int getchar_unlocked(void);

int putc_unlocked(int c, FILE *stream);

int putchar_unlocked(int c);

Description¶

stdio functions with explicit client locking.

Arguments:

stream - the stream to be read or written, c - a character to be put down.

Versions of the functions with names without “_unlocked” which are functionally equivalent to the original versions, with the exception that they are not implemented in a fully thread-safe manner. They are thread-safe when used within a scope protected by flockfile() (or ftrylockfile()) and funlockfile(). These functions can safely be used in a multithreaded program if and only if they are called while the invoking thread owns the (FILE *) object, as is the case after a successful call to the flockfile() or ftrylockfile() functions.

If getc_unlocked() or putc_unlocked() are implemented as macros they may evaluate stream more than once, so the stream argument should never be an expression with side effects.

Return value¶

Upon successful completion, the functions return the byte read or written to or from the stream pointed to by stream.

Errors¶

[EAGAIN] The O_NONBLOCK flag is set for the file descriptor underlying stream and the thread would be delayed in the operation.
[EBADF] The file descriptor underlying stream is not a valid file descriptor open for reading or writing.
[EFBIG] An attempt was made to write to a file that exceeds the maximum file size.
[EINTR] The read or write operation was terminated due to the receipt of a signal, and no data was transferred.
[EIO] A physical I/O error has occurred, or the process is in a background process group attempting to read or write from or to its controlling terminal.
[ENOSPC] There was no free space remaining on the device containing the file.
[EOVERFLOW] The file is a regular file and an attempt was made to read at or beyond the offset maximum associated with the corresponding stream.
[ENOMEM] Insufficient storage space is available.
[ENXIO] A request was made of a nonexistent device, or the request was outside the capabilities of the device.
[EPIPE] An attempt is made to write to a pipe or FIFO that is not open for reading by any process. A SIGPIPE signal is also sent to the thread.

Implementation tasks¶

Implement error handling for the getc_unlocked() function.
Implement error handling for the getchar_unlocked() function.
Implement error handling for the putc_unlocked() function.
Implement error handling for the putchar_unlocked() function.