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Diffstat (limited to 'lib/libc/stdio/open_memstream.3')
| -rw-r--r-- | lib/libc/stdio/open_memstream.3 | 155 |
1 files changed, 155 insertions, 0 deletions
diff --git a/lib/libc/stdio/open_memstream.3 b/lib/libc/stdio/open_memstream.3 new file mode 100644 index 0000000..9396830 --- /dev/null +++ b/lib/libc/stdio/open_memstream.3 @@ -0,0 +1,155 @@ +.\" Copyright (c) 2013 Advanced Computing Technologies LLC +.\" Written by: John H. Baldwin <jhb@FreeBSD.org> +.\" All rights reserved. +.\" +.\" Redistribution and use in source and binary forms, with or without +.\" modification, are permitted provided that the following conditions +.\" are met: +.\" 1. Redistributions of source code must retain the above copyright +.\" notice, this list of conditions and the following disclaimer. +.\" 2. Redistributions in binary form must reproduce the above copyright +.\" notice, this list of conditions and the following disclaimer in the +.\" documentation and/or other materials provided with the distribution. +.\" +.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND +.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE +.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE +.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE +.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL +.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS +.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) +.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT +.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY +.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF +.\" SUCH DAMAGE. +.\" +.\" $FreeBSD$ +.\" +.Dd February 27, 2013 +.Dt OPEN_MEMSTREAM 3 +.Os +.Sh NAME +.Nm open_memstream , +.Nm open_wmemstream +.Nd dynamic memory buffer stream open functions +.Sh LIBRARY +.Lb libc +.Sh SYNOPSIS +.In stdio.h +.Ft FILE * +.Fn open_memstream "char **bufp" "size_t **sizep" +.In wchar.h +.Ft FILE * +.Fn open_wmemstream "wchar_t **bufp" "size_t **sizep" +.Sh DESCRIPTION +The +.Fn open_memstream +and +.Fn open_wmemstream +functions create a write-only, seekable stream backed by a dynamically +allocated memory buffer. +The +.Fn open_memstream +function creates a byte-oriented stream, +while the +.Fn open_wmemstream +function creates a wide-oriented stream. +.Pp +Each stream maintains a current position and size. +Initially, +the position and size are set to zero. +Each write begins at the current position and advances it the number of +successfully written bytes for +.Fn open_memstream +or wide characters for +.Fn open_wmemstream . +If a write moves the current position beyond the length of the buffer, +the length of the buffer is extended and a null character is appended to the +buffer. +.Pp +A stream's buffer always contains a null character at the end of the buffer +that is not included in the current length. +.Pp +If a stream's current position is moved beyond the current length via a +seek operation and a write is performed, +the characters between the current length and the current position are filled +with null characters before the write is performed. +.Pp +After a successful call to +.Xr fclose 3 +or +.Xr fflush 3 , +the pointer referenced by +.Fa bufp +will contain the start of the memory buffer and the variable referenced by +.Fa sizep +will contain the smaller of the current position and the current buffer length. +.Pp +After a successful call to +.Xr fflush 3, +the pointer referenced by +.Fa bufp +and the variable referenced by +.Fa sizep +are only valid until the next write operation or a call to +.Xr fclose 3. +.Pp +Once a stream is closed, +the allocated buffer referenced by +.Fa bufp +should be released via a call to +.Xr free 3 +when it is no longer needed. +.Sh IMPLEMENTATION NOTES +Internally all I/O streams are effectively byte-oriented, +so using wide-oriented operations to write to a stream opened via +.Fn open_wmemstream +results in wide characters being expanded to a stream of multibyte characters +in stdio's internal buffers. +These multibyte characters are then converted back to wide characters when +written into the stream. +As a result, +the wide-oriented streams maintain an internal multibyte character conversion +state that is cleared on any seek opertion that changes the current position. +This should have no effect as long as wide-oriented output operations are used +on a wide-oriented stream. +.Sh RETURN VALUES +Upon successful completion, +.Fn open_memstream +and +.Fn open_wmemstream +return a +.Tn FILE +pointer. +Otherwise, +.Dv NULL +is returned and the global variable +.Va errno +is set to indicate the error. +.Sh ERRORS +.Bl -tag -width Er +.It Bq Er EINVAL +The +.Fa bufp +or +.Fa sizep +argument was +.Dv NULL . +.It Bq Er ENOMEM +Memory for the stream or buffer could not be allocated. +.El +.Sh SEE ALSO +.Xr fclose 3 , +.Xr fflush 3 , +.Xr fopen 3 , +.Xr free 3 , +.Xr fseek 3 , +.Xr sbuf 3 , +.Xr stdio 3 +.Sh STANDARDS +The +.Fn open_memstream +and +.Fn open_wmemstream +functions conform to +.St -p1003.1-2008 . |
