newlib-cygwin/newlib/libc/machine/mips/strncpy.c

251 lines
6.0 KiB
C
Raw Normal View History

/*
* strncpy.S -- strncmp function. On at least some MIPS chips, you get better
* code by hand unrolling the loops, and by using store words to zero the
* remainder of the buffer than the default newlib C version.
*
* Copyright (c) 2001 Red Hat, Inc.
*
* The authors hereby grant permission to use, copy, modify, distribute,
* and license this software and its documentation for any purpose, provided
* that existing copyright notices are retained in all copies and that this
* notice is included verbatim in any distributions. No written agreement,
* license, or royalty fee is required for any of the authorized uses.
* Modifications to this software may be copyrighted by their authors
* and need not follow the licensing terms described here, provided that
* the new terms are clearly indicated on the first page of each file where
* they apply. */
#include <string.h>
#include <stddef.h>
#include <stdlib.h>
#include <stdint.h>
#if !defined(__GNUC__) || (__GNUC__ < 3)
#define __builtin_expect(a,b) a
#else
#ifdef __mips64
/* Don't use limits test for the size of long, in order to allow the use of
64-bit stores on MIPS3 machines, even if -mlong32 was used. */
typedef unsigned word_type __attribute__ ((mode (DI)));
#else
typedef unsigned word_type __attribute__ ((mode (SI)));
#endif
typedef unsigned si_type __attribute__ ((mode (SI)));
typedef unsigned hi_type __attribute__ ((mode (HI)));
#ifndef UNROLL_FACTOR
#define UNROLL_FACTOR 4
#elif (UNROLL_FACTOR != 2) && (UNROLL_FACTOR != 4)
#error "UNROLL_FACTOR must be 2 or 4"
#endif
#endif
char *
strncpy (char *dst0, const char *src0, size_t count)
{
#if defined(PREFER_SIZE_OVER_SPEED) || defined(__OPTIMIZE_SIZE__) || defined(__mips16) || !defined(__GNUC__) || (__GNUC__ < 3)
char *dst, *end;
const char *src;
int ch;
dst = dst0;
src = src0;
end = dst + count;
while (dst != end)
{
*dst++ = ch = *src++;
if (__builtin_expect (ch == '\0', 0))
{
while (dst != end)
*dst++ = '\0';
break;
}
}
return dst0;
#else
unsigned char *dst;
unsigned char *dst_end;
unsigned char *end;
const unsigned char *src;
int ch0, ch1;
#if UNROLL_FACTOR > 2
int ch2, ch3;
#endif
int ch;
int odd_bytes;
size_t long_count;
dst = (unsigned char *)dst0;
src = (unsigned const char *)src0;
/* Take care of any odd bytes in the source data because we
* want to unroll where we read ahead 2 or 4 bytes at a time and then
* check each byte for the null terminator. This can result in
* a segfault for the case where the source pointer is unaligned,
* the null terminator is in valid memory, but reading 2 or 4 bytes at a
* time blindly eventually goes outside of valid memory. */
while (((uintptr_t) src & (UNROLL_FACTOR - 1)) != 0 && count > 0)
{
*dst++ = ch = *src++;
--count;
if (ch == '\0')
{
end = dst + count;
while (dst != end)
*dst++ = '\0';
return dst0;
}
}
if (__builtin_expect (count >= 4, 1))
{
odd_bytes = (count & (UNROLL_FACTOR - 1));
count -= odd_bytes;
do
{
ch0 = src[0];
ch1 = src[1];
#if UNROLL_FACTOR > 2
ch2 = src[2];
ch3 = src[3];
#endif
src += UNROLL_FACTOR;
count -= UNROLL_FACTOR;
dst[0] = ch0;
if (ch0 == '\0')
goto found_null0;
dst[1] = ch1;
if (ch1 == '\0')
goto found_null1;
#if UNROLL_FACTOR > 2
dst[2] = ch2;
if (ch2 == '\0')
goto found_null2;
dst[3] = ch3;
if (ch3 == '\0')
goto found_null3;
#endif
dst += UNROLL_FACTOR;
}
while (count);
/* fall through, count == 0, no null found, deal with last bytes */
count = odd_bytes;
}
end = dst + count;
while (dst != end)
{
*dst++ = ch = *src++;
if (ch == '\0')
{
while (dst != end)
*dst++ = '\0';
break;
}
}
return dst0;
/* Found null byte in first byte, count has been decremented by 4, null has
been stored in dst[0]. */
found_null0:
count++; /* add 1 to cover remaining byte */
dst -= 1; /* adjust dst += 4 gets correct ptr */
/* fall through */
/* Found null byte in second byte, count has been decremented by 4, null has
been stored in dst[1]. */
found_null1:
#if UNROLL_FACTOR > 2
count++; /* add 1 to cover remaining byte */
dst -= 1; /* adjust dst += 4 gets correct ptr */
/* fall through */
/* Found null byte in third byte, count has been decremented by 4, null has
been stored in dst[2]. */
found_null2:
count++; /* add 1 to cover remaining byte */
dst -= 1; /* adjust dst += 4 gets correct ptr */
/* fall through */
/* Found null byte in fourth byte, count is accurate, dst has not been
updated yet. */
found_null3:
#endif
count += odd_bytes; /* restore odd byte count */
dst += UNROLL_FACTOR;
/* Zero fill remainder of the array. Unroll the loop, and use word/dword
stores where we can. */
while (count && (((long)dst) & (sizeof (word_type) - 1)) != 0)
{
count--;
*dst++ = 0;
}
while (count >= UNROLL_FACTOR*sizeof (word_type))
{
count -= UNROLL_FACTOR*sizeof (word_type);
dst += UNROLL_FACTOR*sizeof (word_type);
#if UNROLL_FACTOR > 2
((word_type *)(void *)dst)[-4] = 0;
((word_type *)(void *)dst)[-3] = 0;
#endif
((word_type *)(void *)dst)[-2] = 0;
((word_type *)(void *)dst)[-1] = 0;
}
#if UNROLL_FACTOR > 2
if (count >= 2*sizeof (word_type))
{
count -= 2*sizeof (word_type);
((word_type *)(void *)dst)[0] = 0;
((word_type *)(void *)dst)[1] = 0;
dst += 2*sizeof (word_type);
}
#endif
if (count >= sizeof (word_type))
{
count -= sizeof (word_type);
((word_type *)(void *)dst)[0] = 0;
dst += sizeof (word_type);
}
#ifdef __mips64
if (count >= sizeof (si_type))
{
count -= sizeof (si_type);
((si_type *)(void *)dst)[0] = 0;
dst += sizeof (si_type);
}
#endif
if (count >= sizeof (hi_type))
{
count -= sizeof (hi_type);
((hi_type *)(void *)dst)[0] = 0;
dst += sizeof (hi_type);
}
if (count)
*dst = '\0';
return dst0;
#endif
}