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open_memstream(3c)

open_memstream(3C)       Standard C Library Functions       open_memstream(3C)

NAME
       open_memstream, open_wmemstream - open a dynamic memory buffer stream

SYNOPSIS
       #include <stdio.h>


       FILE *open_memstream(char **bufp, size_t *sizep);


       #include <wchar.h>


       FILE *open_wmemstream(wchar_t **bufp, size_t *sizep);

DESCRIPTION
       The  open_memstream()  and  open_wmemstream()  functions  create an I/O
       stream associated with  a  dynamically  allocated  memory  buffer.  The
       stream is opened for writing and is seekable.


       The stream associated with a call to open_memstream() is byte-oriented.


       The  stream  associated  with  a call to open_wmemstream() is wide-ori‐
       ented.


       The stream maintains a current position in the allocated buffer  and  a
       current buffer length. The position is initially set to zero (the start
       of the buffer). Each write to the stream starts at the current position
       and  move this position by the number of successfully written bytes for
       open_memstream() or the number of successfully written wide  characters
       for  open_wmemstream(). The length is initially set to zero. If a write
       moves the position to a value larger than the current length, the  cur‐
       rent length is set to this position. In this case, a null character for
       open_memstream()  or a null wide character for open_wmemstream() is ap‐
       pended to the current buffer. For both functions, the terminating  null
       is not included in the calculation of the buffer length.


       After a successful fflush() or fclose(), the pointer referenced by bufp
       contains  the  address  of  the  buffer, and the variable pointed to by
       sizep contains the smaller of the current buffer length and the  number
       of  bytes  for  open_memstream(),  or the number of wide characters for
       open_wmemstream(), between the beginning of the buffer and the  current
       file position indicator.


       After  a  successful fflush(), the pointer referenced by bufp() and the
       variable referenced by sizep remain valid only until the next write op‐
       eration on the stream or a call to fclose().

RETURN VALUES
       Upon successful completion, these functions return a pointer to the ob‐
       ject controlling the stream. Otherwise, a null  pointer  shall  be  re‐
       turned, and errno shall be set to indicate the error.

ERRORS
       These functions will fail if:

       EINVAL    The bufp or sizep argument is NULL.


       ENOMEM    Insufficient storage space is available.


USAGE
       The  buffer  created by these functions should be freed by the applica‐
       tion after closing the stream, by means of a call to free().


       Unlike a stream opened by fmemopen(), the mode of a  stream  opened  by
       open_memstream()  or  open_wmemstream()  cannot be changed by a call to
       freopen(NULL, mode, stream).

ATTRIBUTES
       See attributes(7) for descriptions of the following attributes:

       tab() box; cw(2.75i) |cw(2.75i) lw(2.75i) |lw(2.75i) ATTRIBUTE  TYPEAT‐
       TRIBUTE  VALUE _ Interface StabilityCommitted _ MT-LevelMT-Safe _ Stan‐
       dardSee standards(7).


SEE ALSO
       fmemopen(3C), fopen(3C), freopen(3C), malloc(3C), attributes(7),  stan‐
       dards(7)

Oracle Solaris 11.4               04 Oct 2013               open_memstream(3C)
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