141 lines
4.7 KiB
C
141 lines
4.7 KiB
C
/****************************************************************************
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* libs/libc/string/lib_bsdmemccpy.c
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*
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* Copyright (c) 1994-2009 Red Hat, Inc. All rights reserved.
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*
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* This copyrighted material is made available to anyone wishing to use,
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* modify, copy, or redistribute it subject to the terms and conditions
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* of the BSD License. This program is distributed in the hope that
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* it will be useful, but WITHOUT ANY WARRANTY expressed or implied,
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* including the implied warranties of MERCHANTABILITY or FITNESS FOR
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* A PARTICULAR PURPOSE. A copy of this license is available at
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* http://www.opensource.org/licenses. Any Red Hat trademarks that are
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* incorporated in the source code or documentation are not subject to
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* the BSD License and may only be used or replicated with the express
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* permission of Red Hat, Inc.
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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 <nuttx/config.h>
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#include <sys/types.h>
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#include <string.h>
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/****************************************************************************
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* Pre-processor Definitions
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****************************************************************************/
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/* Nonzero if either x or y is not aligned on a "long" boundary. */
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#define UNALIGNED(x, y) \
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(((long)(uintptr_t)(x) & (sizeof(long) - 1)) | ((long)(uintptr_t)(y) & (sizeof(long) - 1)))
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/* How many bytes are copied each iteration of the word copy loop. */
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#define LITTLEBLOCKSIZE (sizeof(long))
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/* Threshhold for punting to the byte copier. */
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#define TOO_SMALL(len) ((len) < LITTLEBLOCKSIZE)
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/* Macros for detecting endchar */
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#if LONG_MAX == 2147483647
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# define DETECTNULL(x) (((x) - 0x01010101) & ~(x) & 0x80808080)
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#elif LONG_MAX == 9223372036854775807
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/* Nonzero if x (a long int) contains a NULL byte. */
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# define DETECTNULL(x) (((x) - 0x0101010101010101) & ~(x) & 0x8080808080808080)
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#endif
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: memccpy
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*
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* Description:
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* The memccpy() function copies bytes from memory area s2 into s1,
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* stopping after the first occurrence of byte c (converted to an unsigned
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* char) is copied, or after n bytes are copied, whichever comes first. If
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* copying takes place between objects that overlap, the behavior is
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* undefined.
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*
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* Returned Value:
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* The memccpy() function returns a pointer to the byte after the copy of c
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* in s1, or a null pointer if c was not found in the first n bytes of s2.
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*
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****************************************************************************/
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#undef memccpy /* See mm/README.txt */
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FAR void *memccpy(FAR void *s1, FAR const void *s2, int c, size_t n)
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{
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FAR void *ptr = NULL;
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FAR unsigned char *pout = (FAR unsigned char *)s1;
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FAR const unsigned char *pin = (FAR const unsigned char *)s2;
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FAR long *paligned_out;
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FAR const long *paligned_in;
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unsigned char endchar = c & 0xff;
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/* If the size is small, or either pin or pout is unaligned,
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* then punt into the byte copy loop. This should be rare.
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*/
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if (!TOO_SMALL(n) && !UNALIGNED(pin, pout))
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{
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unsigned int i;
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unsigned long mask = 0;
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paligned_out = (FAR long *)pout;
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paligned_in = (FAR long *)pin;
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/* The fast code reads the ASCII one word at a time and only
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* performs the bytewise search on word-sized segments if they
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* contain the search character, which is detected by XORing
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* the word-sized segment with a word-sized block of the search
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* character and then detecting for the presence of NULL in the
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* result.
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*/
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for (i = 0; i < LITTLEBLOCKSIZE; i++)
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{
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mask = (mask << 8) + endchar;
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}
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/* Copy one long word at a time if possible. */
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while (n >= LITTLEBLOCKSIZE)
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{
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unsigned long buffer = (unsigned long)(*paligned_in);
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buffer ^= mask;
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if (DETECTNULL(buffer))
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{
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break; /* endchar is found, go byte by byte from here */
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}
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*paligned_out++ = *paligned_in++;
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n -= LITTLEBLOCKSIZE;
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}
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/* Pick up any residual with a byte copier. */
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pout = (FAR unsigned char *)paligned_out;
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pin = (FAR unsigned char *)paligned_in;
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}
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while (n--)
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{
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if ((*pout++ = *pin++) == endchar)
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{
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ptr = pout;
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break;
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}
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}
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return ptr;
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}
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