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-rw-r--r--libc/string/generic/memcmp.c340
1 files changed, 340 insertions, 0 deletions
diff --git a/libc/string/generic/memcmp.c b/libc/string/generic/memcmp.c
new file mode 100644
index 000000000..d9c3a7cab
--- /dev/null
+++ b/libc/string/generic/memcmp.c
@@ -0,0 +1,340 @@
+/* Copyright (C) 1991,1993,1995,1997,1998,2003,2004
+ Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+ Contributed by Torbjorn Granlund (tege@sics.se).
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library 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
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, write to the Free
+ Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+ 02111-1307 USA. */
+
+#include <string.h>
+
+#undef memcmp
+
+#include "memcopy.h"
+
+#include <endian.h>
+
+#if __BYTE_ORDER == __BIG_ENDIAN
+# define WORDS_BIGENDIAN
+#endif
+
+#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. */
+
+static int memcmp_bytes __P((op_t, op_t));
+
+# 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
+
+static int memcmp_common_alignment __P((long, long, size_t));
+
+/* 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. */
+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)
+ {
+ default: /* Avoid warning about uninitialized local variables. */
+ 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;
+}
+
+static int memcmp_not_common_alignment __P((long, long, size_t));
+
+/* 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*. */
+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)
+ {
+ default: /* Avoid warning about uninitialized local variables. */
+ 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
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