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FOPENCOOKIE(3) BSD Library Functions Manual FOPENCOOKIE(3) NAME fopencookie -- open a stream LIBRARY Standard C Library (libc, -lc) SYNOPSIS #include <stdio.h> typedef ssize_t (*cookie_read_function_t)(void *cookie, char *buf, size_t size); typedef ssize_t (*cookie_write_function_t)(void *cookie, const char *buf, size_t size); typedef int (*cookie_seek_function_t)(void *cookie, off64_t *offset, int whence); typedef int (*cookie_close_function_t)(void *cookie); typedef struct { cookie_read_function_t *read; cookie_write_function_t *write; cookie_seek_function_t *seek; cookie_close_function_t *close; } cookie_io_functions_t; FILE * fopencookie(void *cookie, const char *mode, cookie_io_functions_t io_funcs); DESCRIPTION The fopencookie function associates a stream with up to four "I/O functions". These I/O functions will be used to read, write, seek and close the new stream. In general, omitting a function means that any attempt to perform the as- sociated operation on the resulting stream will fail. If the write func- tion is omitted, data written to the stream is discarded. If the close function is omitted, closing the stream will flush any buffered output and then succeed. The calling conventions of read, write, and close must match those, re- spectively, of read(2), write(2), and close(2) with the single exception that they are passed the cookie argument specified to fopencookie in place of the traditional file descriptor argument. The seek function up- dates the current stream offset using *offset and whence. If *offset is non-NULL, it updates *offset with the current stream offset. fopencookie is implemented as a thin shim around the funopen(3) inter- face. Limitations, possibilities, and requirements of that interface ap- ply to fopencookie. RETURN VALUES Upon successful completion, fopencookie returns a FILE pointer. Other- wise, NULL is returned and the global variable errno is set to indicate the error. ERRORS [EINVAL] A bogus mode was provided to fopencookie. [ENOMEM] The fopencookie function may fail and set errno for any of the errors specified for the malloc(3) routine. SEE ALSO fcntl(2), open(2), fclose(3), fopen(3), fseek(3), funopen(3) HISTORY The funopen() functions first appeared in 4.4BSD. The fopencookie func- tion first appeared in FreeBSD 11. BUGS The fopencookie function is a nonstandard glibc extension and may not be portable to systems other than FreeBSD and Linux. BSD May 9, 2016 BSD
NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUES | ERRORS | SEE ALSO | HISTORY | BUGS
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