MirOS Manual: gzfdopen(3), gzfopen(3)

GZFOPEN(3)                 BSD Programmer's Manual                  GZFOPEN(3)


     gzfopen, gzfdopen - deflated stream open functions


     #include <zlib.h>

     FILE *
     gzfopen(const char *path, const char *mode);

     FILE *
     gzfdopen(int filedes, const char *mode);


     The gzfopen() function opens the file whose name is the string pointed to
     by path and associates a zlib stream with it.

     The gzfdopen() function associates a zlib stream with the existing file
     descriptor filedes. The mode of the stream must be compatible with the
     mode of the file descriptor. The stream is positioned at the file offset
     of the file descriptor, which must point to the first byte of the deflate
     magic in read mode. If gzfdopen() fails, the file descriptor filedes is
     not affected in any way. If gzfdopen() succeeds, any subsequential
     fclose() will also close and invalidate filedes.

     The argument mode points to a string beginning with one of the following
     characters (additional characters may follow):

     "r"     Open file for reading.

     "w"     Truncate file to zero length or create text file for writing.

     "a"     Open for writing. The file is created if it does not exist.

     The characters which can follow are the same as for the gzopen() func-

     "b"     Binary mode (meaningless under UNIX).

     "f"     Set the zlib stream strategy to filtered.

     "h"     Set the zlib stream strategy to huffman-only.

     "R"     Set the zlib stream to use RLE compression instead of deflate.

     "0..9"  Set the compression level of the zlib stream used for writing.


     Upon successful completion, gzfopen() and gzfdopen() return a FILE
     pointer. Otherwise, NULL is returned and the global variable errno is set
     to indicate the error.


     For both the gzfopen() and gzfdopen() functions, as well as stream opera-
     tions (read, write, seek, close), the code tries to meaningful map the
     zlib error codes to errno values. An unknown error is mapped to

     gzfopen() and gzfdopen() can return any error code which the underlying
     funopen() function returns, and fail for additional reasons.


     close(2), funopen(3), gzclose(3), gzdopen(3), gzopen(3), gzread(3),
     gzseek(3), gzwrite(3), lseek(2), open(2), read(2), write(2)

     The description of deflateInit2() inside compress(3).


     gzfopen and gzfdopen first appeared in MirOS #9.


     The code and manual page have been written by Thorsten Glaser


     Attempt to lseek() on the stream is subject to the same limitations as
     gzseek() is, and discouraged.

MirOS BSD #10-current          January 24, 2006                              1

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