133 lines
4.5 KiB
C
133 lines
4.5 KiB
C
/****************************************************************************
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* libs/libc/stdio/lib_vasprintf.c
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*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership. The
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* ASF licenses this file to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance with the
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* License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <stdio.h>
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#include <stdlib.h>
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#include <stdarg.h>
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#include <assert.h>
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#include "libc.h"
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/****************************************************************************
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* Pre-processor Definitions
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****************************************************************************/
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: vasprintf
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*
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* Description:
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* This function is similar to vsprintf, except that it dynamically
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* allocates a string (as with malloc) to hold the output, instead of
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* putting the output in a buffer you allocate in advance. The ptr
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* argument should be the address of a char * object, and a successful
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* call to vasprintf stores a pointer to the newly allocated string at that
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* location.
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*
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* Returned Value:
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* The returned value is the number of characters allocated for the buffer,
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* or less than zero if an error occurred. Usually this means that the
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* buffer could not be allocated.
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*
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****************************************************************************/
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int vasprintf(FAR char **ptr, FAR const IPTR char *fmt, va_list ap)
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{
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struct lib_outstream_s nulloutstream;
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struct lib_memoutstream_s memoutstream;
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/* On some architectures, va_list is really a pointer to a structure on
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* the stack. And the va_arg builtin will modify that instance of va_list.
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* Since vasprintf traverse the parameters in the va_list twice, the
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* va_list will be altered in this first cases and the second usage will
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* fail. This is a known issue with x86_64.
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*/
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#ifdef va_copy
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va_list ap2;
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#endif
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FAR char *buf;
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int nbytes;
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DEBUGASSERT(ptr && fmt);
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#ifdef va_copy
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va_copy(ap2, ap);
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#endif
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/* First, use a nullstream to get the size of the buffer. The number
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* of bytes returned may or may not include the null terminator.
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*/
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lib_nulloutstream(&nulloutstream);
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lib_vsprintf((FAR struct lib_outstream_s *)&nulloutstream, fmt, ap);
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/* Then allocate a buffer to hold that number of characters, adding one
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* for the null terminator.
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*/
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buf = (FAR char *)lib_malloc(nulloutstream.nput + 1);
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if (!buf)
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{
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#ifdef va_copy
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va_end(ap2);
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#endif
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return ERROR;
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}
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/* Initialize a memory stream to write into the allocated buffer. The
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* memory stream will reserve one byte at the end of the buffer for the
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* null terminator and will not report this in the number of output bytes.
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*/
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lib_memoutstream((FAR struct lib_memoutstream_s *)&memoutstream,
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buf, nulloutstream.nput + 1);
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/* Then let lib_vsprintf do it's real thing */
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#ifdef va_copy
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nbytes = lib_vsprintf((FAR struct lib_outstream_s *)&memoutstream.public,
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fmt, ap2);
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va_end(ap2);
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#else
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nbytes = lib_vsprintf((FAR struct lib_outstream_s *)&memoutstream.public,
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fmt, ap);
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#endif
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/* Return a pointer to the string to the caller. NOTE: the memstream put()
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* method has already added the NUL terminator to the end of the string
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* (not included in the nput count).
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*
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* Hmmm.. looks like the memory would be stranded if lib_vsprintf()
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* returned an error. Does that ever happen?
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*/
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DEBUGASSERT(nbytes < 0 || nbytes == nulloutstream.nput);
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*ptr = buf;
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return nbytes;
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}
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