85 lines
2.9 KiB
C
85 lines
2.9 KiB
C
/****************************************************************************
|
|
* libs/libc/unistd/lib_swab.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 <nuttx/config.h>
|
|
|
|
#include <sys/types.h>
|
|
#include <unistd.h>
|
|
#include <assert.h>
|
|
|
|
/****************************************************************************
|
|
* Public Functions
|
|
****************************************************************************/
|
|
|
|
/****************************************************************************
|
|
* Name: strncpy
|
|
*
|
|
* Description:
|
|
* The swab() function will copy nbytes bytes, which are pointed to by
|
|
* 'src', to the object pointed to by 'dest', exchanging adjacent bytes.
|
|
* The 'nbytes' argument should be even. If 'nbytes' is odd, swab() copies
|
|
* and exchanges 'nbytes'-1 bytes and the disposition of the last byte is
|
|
* unspecified. If copying takes place between objects that overlap, the
|
|
* behavior is undefined. If nbytes is negative, swab() does nothing.
|
|
*
|
|
* Returned Value:
|
|
* None
|
|
*
|
|
****************************************************************************/
|
|
|
|
void swab(FAR const void *src, FAR void *dest, ssize_t nbytes)
|
|
{
|
|
FAR const uint8_t *src8 = (FAR const uint8_t *)src;
|
|
FAR uint8_t *dest8 = (FAR uint8_t *)dest;
|
|
FAR uint8_t *end8;
|
|
|
|
DEBUGASSERT(src != NULL && dest != NULL);
|
|
|
|
/* Do nother if nbytes is negative or it there are few then 2 bytes to be
|
|
* transferred.
|
|
*/
|
|
|
|
if (nbytes > 1)
|
|
{
|
|
/* The end of dest buffer + 1 byte (skipping any odd numbered byte at
|
|
* the end of the buffer.
|
|
*/
|
|
|
|
end8 = dest8 + (nbytes & ~1);
|
|
|
|
/* Loop until the destination is equal to the end + 1 address */
|
|
|
|
while (dest8 != end8)
|
|
{
|
|
register uint8_t tmp;
|
|
|
|
/* Transfer the bytes, swapping the order */
|
|
|
|
tmp = *src8++;
|
|
*dest8++ = *src8++;
|
|
*dest8++ = tmp;
|
|
}
|
|
}
|
|
}
|