summaryrefslogtreecommitdiff
path: root/misc/memcmp.c
diff options
context:
space:
mode:
Diffstat (limited to 'misc/memcmp.c')
-rw-r--r--misc/memcmp.c373
1 files changed, 373 insertions, 0 deletions
diff --git a/misc/memcmp.c b/misc/memcmp.c
new file mode 100644
index 000000000..6096651e5
--- /dev/null
+++ b/misc/memcmp.c
@@ -0,0 +1,373 @@
+/* Copyright (C) 1991, 1993, 1995 Free Software Foundation, Inc.
+ Contributed by Torbjorn Granlund (tege@sics.se).
+
+NOTE: The canonical source of this file is maintained with the GNU C Library.
+Bugs can be reported to bug-glibc@prep.ai.mit.edu.
+
+This program is free software; you can redistribute it and/or modify it
+under the terms of the GNU General Public License as published by the
+Free Software Foundation; either version 2, or (at your option) any
+later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program; if not, write to the Free Software Foundation,
+Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#undef __ptr_t
+#if defined (__cplusplus) || (defined (__STDC__) && __STDC__)
+#define __ptr_t void *
+#else /* Not C++ or ANSI C. */
+#undef const
+#define const
+#define __ptr_t char *
+#endif /* C++ or ANSI C. */
+
+#if defined (HAVE_STRING_H) || defined (_LIBC)
+#include <string.h>
+#endif
+
+#ifdef _LIBC
+
+#include <memcopy.h>
+
+#else /* Not in the GNU C library. */
+
+#include <sys/types.h>
+
+/* Type to use for aligned memory operations.
+ This should normally be the biggest type supported by a single load
+ and store. Must be an unsigned type. */
+#define op_t unsigned long int
+#define OPSIZ (sizeof(op_t))
+
+/* Threshold value for when to enter the unrolled loops. */
+#define OP_T_THRES 16
+
+/* Type to use for unaligned operations. */
+typedef unsigned char byte;
+
+#ifndef WORDS_BIGENDIAN
+#define MERGE(w0, sh_1, w1, sh_2) (((w0) >> (sh_1)) | ((w1) << (sh_2)))
+#else
+#define MERGE(w0, sh_1, w1, sh_2) (((w0) << (sh_1)) | ((w1) >> (sh_2)))
+#endif
+
+#endif /* In the GNU C library. */
+
+#ifdef WORDS_BIGENDIAN
+#define CMP_LT_OR_GT(a, b) ((a) > (b) ? 1 : -1)
+#else
+#define CMP_LT_OR_GT(a, b) memcmp_bytes ((a), (b))
+#endif
+
+/* BE VERY CAREFUL IF YOU CHANGE THIS CODE! */
+
+/* The strategy of this memcmp is:
+
+ 1. Compare bytes until one of the block pointers is aligned.
+
+ 2. Compare using memcmp_common_alignment or
+ memcmp_not_common_alignment, regarding the alignment of the other
+ block after the initial byte operations. The maximum number of
+ full words (of type op_t) are compared in this way.
+
+ 3. Compare the few remaining bytes. */
+
+#ifndef WORDS_BIGENDIAN
+/* memcmp_bytes -- Compare A and B bytewise in the byte order of the machine.
+ A and B are known to be different.
+ This is needed only on little-endian machines. */
+#ifdef __GNUC__
+__inline
+#endif
+static int
+memcmp_bytes (a, b)
+ op_t a, b;
+{
+ long int srcp1 = (long int) &a;
+ long int srcp2 = (long int) &b;
+ op_t a0, b0;
+
+ do
+ {
+ a0 = ((byte *) srcp1)[0];
+ b0 = ((byte *) srcp2)[0];
+ srcp1 += 1;
+ srcp2 += 1;
+ }
+ while (a0 == b0);
+ return a0 - b0;
+}
+#endif
+
+/* memcmp_common_alignment -- Compare blocks at SRCP1 and SRCP2 with LEN `op_t'
+ objects (not LEN bytes!). Both SRCP1 and SRCP2 should be aligned for
+ memory operations on `op_t's. */
+#ifdef __GNUC__
+__inline
+#endif
+static int
+memcmp_common_alignment (srcp1, srcp2, len)
+ long int srcp1;
+ long int srcp2;
+ size_t len;
+{
+ op_t a0, a1;
+ op_t b0, b1;
+
+ switch (len % 4)
+ {
+ case 2:
+ a0 = ((op_t *) srcp1)[0];
+ b0 = ((op_t *) srcp2)[0];
+ srcp1 -= 2 * OPSIZ;
+ srcp2 -= 2 * OPSIZ;
+ len += 2;
+ goto do1;
+ case 3:
+ a1 = ((op_t *) srcp1)[0];
+ b1 = ((op_t *) srcp2)[0];
+ srcp1 -= OPSIZ;
+ srcp2 -= OPSIZ;
+ len += 1;
+ goto do2;
+ case 0:
+ if (OP_T_THRES <= 3 * OPSIZ && len == 0)
+ return 0;
+ a0 = ((op_t *) srcp1)[0];
+ b0 = ((op_t *) srcp2)[0];
+ goto do3;
+ case 1:
+ a1 = ((op_t *) srcp1)[0];
+ b1 = ((op_t *) srcp2)[0];
+ srcp1 += OPSIZ;
+ srcp2 += OPSIZ;
+ len -= 1;
+ if (OP_T_THRES <= 3 * OPSIZ && len == 0)
+ goto do0;
+ /* Fall through. */
+ }
+
+ do
+ {
+ a0 = ((op_t *) srcp1)[0];
+ b0 = ((op_t *) srcp2)[0];
+ if (a1 != b1)
+ return CMP_LT_OR_GT (a1, b1);
+
+ do3:
+ a1 = ((op_t *) srcp1)[1];
+ b1 = ((op_t *) srcp2)[1];
+ if (a0 != b0)
+ return CMP_LT_OR_GT (a0, b0);
+
+ do2:
+ a0 = ((op_t *) srcp1)[2];
+ b0 = ((op_t *) srcp2)[2];
+ if (a1 != b1)
+ return CMP_LT_OR_GT (a1, b1);
+
+ do1:
+ a1 = ((op_t *) srcp1)[3];
+ b1 = ((op_t *) srcp2)[3];
+ if (a0 != b0)
+ return CMP_LT_OR_GT (a0, b0);
+
+ srcp1 += 4 * OPSIZ;
+ srcp2 += 4 * OPSIZ;
+ len -= 4;
+ }
+ while (len != 0);
+
+ /* This is the right position for do0. Please don't move
+ it into the loop. */
+ do0:
+ if (a1 != b1)
+ return CMP_LT_OR_GT (a1, b1);
+ return 0;
+}
+
+/* memcmp_not_common_alignment -- Compare blocks at SRCP1 and SRCP2 with LEN
+ `op_t' objects (not LEN bytes!). SRCP2 should be aligned for memory
+ operations on `op_t', but SRCP1 *should be unaligned*. */
+#ifdef __GNUC__
+__inline
+#endif
+static int
+memcmp_not_common_alignment (srcp1, srcp2, len)
+ long int srcp1;
+ long int srcp2;
+ size_t len;
+{
+ op_t a0, a1, a2, a3;
+ op_t b0, b1, b2, b3;
+ op_t x;
+ int shl, shr;
+
+ /* Calculate how to shift a word read at the memory operation
+ aligned srcp1 to make it aligned for comparison. */
+
+ shl = 8 * (srcp1 % OPSIZ);
+ shr = 8 * OPSIZ - shl;
+
+ /* Make SRCP1 aligned by rounding it down to the beginning of the `op_t'
+ it points in the middle of. */
+ srcp1 &= -OPSIZ;
+
+ switch (len % 4)
+ {
+ case 2:
+ a1 = ((op_t *) srcp1)[0];
+ a2 = ((op_t *) srcp1)[1];
+ b2 = ((op_t *) srcp2)[0];
+ srcp1 -= 1 * OPSIZ;
+ srcp2 -= 2 * OPSIZ;
+ len += 2;
+ goto do1;
+ case 3:
+ a0 = ((op_t *) srcp1)[0];
+ a1 = ((op_t *) srcp1)[1];
+ b1 = ((op_t *) srcp2)[0];
+ srcp2 -= 1 * OPSIZ;
+ len += 1;
+ goto do2;
+ case 0:
+ if (OP_T_THRES <= 3 * OPSIZ && len == 0)
+ return 0;
+ a3 = ((op_t *) srcp1)[0];
+ a0 = ((op_t *) srcp1)[1];
+ b0 = ((op_t *) srcp2)[0];
+ srcp1 += 1 * OPSIZ;
+ goto do3;
+ case 1:
+ a2 = ((op_t *) srcp1)[0];
+ a3 = ((op_t *) srcp1)[1];
+ b3 = ((op_t *) srcp2)[0];
+ srcp1 += 2 * OPSIZ;
+ srcp2 += 1 * OPSIZ;
+ len -= 1;
+ if (OP_T_THRES <= 3 * OPSIZ && len == 0)
+ goto do0;
+ /* Fall through. */
+ }
+
+ do
+ {
+ a0 = ((op_t *) srcp1)[0];
+ b0 = ((op_t *) srcp2)[0];
+ x = MERGE(a2, shl, a3, shr);
+ if (x != b3)
+ return CMP_LT_OR_GT (x, b3);
+
+ do3:
+ a1 = ((op_t *) srcp1)[1];
+ b1 = ((op_t *) srcp2)[1];
+ x = MERGE(a3, shl, a0, shr);
+ if (x != b0)
+ return CMP_LT_OR_GT (x, b0);
+
+ do2:
+ a2 = ((op_t *) srcp1)[2];
+ b2 = ((op_t *) srcp2)[2];
+ x = MERGE(a0, shl, a1, shr);
+ if (x != b1)
+ return CMP_LT_OR_GT (x, b1);
+
+ do1:
+ a3 = ((op_t *) srcp1)[3];
+ b3 = ((op_t *) srcp2)[3];
+ x = MERGE(a1, shl, a2, shr);
+ if (x != b2)
+ return CMP_LT_OR_GT (x, b2);
+
+ srcp1 += 4 * OPSIZ;
+ srcp2 += 4 * OPSIZ;
+ len -= 4;
+ }
+ while (len != 0);
+
+ /* This is the right position for do0. Please don't move
+ it into the loop. */
+ do0:
+ x = MERGE(a2, shl, a3, shr);
+ if (x != b3)
+ return CMP_LT_OR_GT (x, b3);
+ return 0;
+}
+
+int
+memcmp (s1, s2, len)
+ const __ptr_t s1;
+ const __ptr_t s2;
+ size_t len;
+{
+ op_t a0;
+ op_t b0;
+ long int srcp1 = (long int) s1;
+ long int srcp2 = (long int) s2;
+ op_t res;
+
+ if (len >= OP_T_THRES)
+ {
+ /* There are at least some bytes to compare. No need to test
+ for LEN == 0 in this alignment loop. */
+ while (srcp2 % OPSIZ != 0)
+ {
+ a0 = ((byte *) srcp1)[0];
+ b0 = ((byte *) srcp2)[0];
+ srcp1 += 1;
+ srcp2 += 1;
+ res = a0 - b0;
+ if (res != 0)
+ return res;
+ len -= 1;
+ }
+
+ /* SRCP2 is now aligned for memory operations on `op_t'.
+ SRCP1 alignment determines if we can do a simple,
+ aligned compare or need to shuffle bits. */
+
+ if (srcp1 % OPSIZ == 0)
+ res = memcmp_common_alignment (srcp1, srcp2, len / OPSIZ);
+ else
+ res = memcmp_not_common_alignment (srcp1, srcp2, len / OPSIZ);
+ if (res != 0)
+ return res;
+
+ /* Number of bytes remaining in the interval [0..OPSIZ-1]. */
+ srcp1 += len & -OPSIZ;
+ srcp2 += len & -OPSIZ;
+ len %= OPSIZ;
+ }
+
+ /* There are just a few bytes to compare. Use byte memory operations. */
+ while (len != 0)
+ {
+ a0 = ((byte *) srcp1)[0];
+ b0 = ((byte *) srcp2)[0];
+ srcp1 += 1;
+ srcp2 += 1;
+ res = a0 - b0;
+ if (res != 0)
+ return res;
+ len -= 1;
+ }
+
+ return 0;
+}
+
+#ifdef weak_alias
+#undef bcmp
+weak_alias (memcmp, bcmp)
+#endif
+
+
generated by cgit v1.2.3 (git 2.25.1) at 2024-11-01 17:29:05 +0000