nuttx/libs/libc/stream/lib_memsistream.c

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/****************************************************************************
* libs/libc/stream/lib_memsistream.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: memsistream_getc
****************************************************************************/
static int memsistream_getc(FAR struct lib_sistream_s *this)
{
FAR struct lib_memsistream_s *mthis = (FAR struct lib_memsistream_s *)this;
int ret;
DEBUGASSERT(this);
/* Get the next character (if any) from the buffer */
if (mthis->offset < mthis->buflen)
{
ret = mthis->buffer[mthis->offset];
mthis->offset++;
this->nget++;
}
else
{
ret = EOF;
}
return ret;
}
/****************************************************************************
* Name: meminstream_gets
****************************************************************************/
static int memsistream_gets(FAR struct lib_instream_s *this,
FAR void *buffer, int len)
{
FAR struct lib_memsistream_s *mthis = (FAR struct lib_memsistream_s *)this;
int ret;
DEBUGASSERT(this);
/* Get the buffer (if any) from the stream */
if (this->nget < mthis->buflen)
{
ret = mthis->buflen - this->nget;
ret = ret < len ? ret : len;
this->nget += ret;
memcpy(buffer, mthis->buffer, ret);
}
else
{
ret = EOF;
}
return ret;
}
/****************************************************************************
* Name: memsistream_seek
****************************************************************************/
static off_t memsistream_seek(FAR struct lib_sistream_s *this, off_t offset,
int whence)
{
FAR struct lib_memsistream_s *mthis = (FAR struct lib_memsistream_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_memsistream
*
* Description:
* Initializes a stream for use with a fixed-size memory buffer.
*
* Input Parameters:
* instream - User allocated, uninitialized instance of struct
* lib_memsistream_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 (instream initialized).
*
****************************************************************************/
void lib_memsistream(FAR struct lib_memsistream_s *instream,
FAR const char *bufstart, int buflen)
{
instream->public.getc = memsistream_getc;
instream->public.gets = memsistream_gets;
instream->public.seek = memsistream_seek;
instream->public.nget = 0; /* Total number of characters read */
instream->buffer = bufstart; /* Start of buffer */
instream->offset = 0; /* Will be the buffer index */
instream->buflen = buflen; /* Length of the buffer */
}