nuttx/libs/libc/stream/lib_memsostream.c

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/****************************************************************************
* libs/libc/stream/lib_memsostream.c
*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership. The
* ASF licenses this file to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance with the
* License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations
* under the License.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <assert.h>
#include "libc.h"
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Name: memsostream_putc
****************************************************************************/
static void memsostream_putc(FAR struct lib_sostream_s *this, int ch)
{
FAR struct lib_memsostream_s *mthis = (FAR struct lib_memsostream_s *)this;
DEBUGASSERT(this);
/* If this will not overrun the buffer, then write the character to the
* buffer. Not that buflen was pre-decremented when the stream was
* created so it is okay to write past the end of the buflen by one.
*/
if (mthis->offset < mthis->buflen)
{
mthis->buffer[mthis->offset] = ch;
mthis->offset++;
this->nput++;
mthis->buffer[mthis->offset] = '\0';
}
}
/****************************************************************************
* Name: memsostream_seek
****************************************************************************/
static off_t memsostream_seek(FAR struct lib_sostream_s *this, off_t offset,
int whence)
{
FAR struct lib_memsostream_s *mthis = (FAR struct lib_memsostream_s *)this;
off_t newpos;
DEBUGASSERT(this);
switch (whence)
{
case SEEK_CUR:
newpos = (off_t)mthis->offset + offset;
break;
case SEEK_SET:
newpos = offset;
break;
case SEEK_END:
newpos = (off_t)mthis->buflen + offset;
break;
default:
return (off_t)ERROR;
}
/* Make sure that the new position is within range */
if (newpos < 0 || newpos >= (off_t)mthis->buflen)
{
return (off_t)ERROR;
}
/* Return the new position */
mthis->offset = (size_t)newpos;
return newpos;
}
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: lib_memsostream
*
* Description:
* Initializes a stream for use with a fixed-size memory buffer.
*
* Input Parameters:
* outstream - User allocated, uninitialized instance of struct
* lib_memsostream_s to be initialized.
* bufstart - Address of the beginning of the fixed-size memory buffer
* buflen - Size of the fixed-sized memory buffer in bytes
*
* Returned Value:
* None (outstream initialized).
*
****************************************************************************/
void lib_memsostream(FAR struct lib_memsostream_s *outstream,
FAR char *bufstart, int buflen)
{
outstream->public.put = memsostream_putc;
outstream->public.flush = lib_snoflush;
outstream->public.seek = memsostream_seek;
outstream->public.nput = 0; /* Total number of characters written */
outstream->buffer = bufstart; /* Start of buffer */
outstream->offset = 0; /* Will be the buffer index */
outstream->buflen = buflen - 1; /* Save space for null terminator */
outstream->buffer[0] = '\0'; /* Start with an empty string */
}