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-rw-r--r--mysys/ptr_cmp.c231
1 files changed, 231 insertions, 0 deletions
diff --git a/mysys/ptr_cmp.c b/mysys/ptr_cmp.c
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+++ b/mysys/ptr_cmp.c
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+/* Copyright (c) 2000, 2015, Oracle and/or its affiliates. All rights reserved.
+
+ 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; version 2 of the License.
+
+ 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., 51 Franklin St, Fifth Floor, Boston, MA 02110-1335 USA */
+
+/*
+ get_ptr_compare(len) returns a pointer to a optimal byte-compare function
+ for a array of stringpointer where all strings have size len.
+ The bytes are compare as unsigned chars.
+ */
+
+#include "mysys_priv.h"
+#include <myisampack.h>
+/*
+ * On some platforms, memcmp() is faster than the unrolled ptr_compare_N
+ * functions, as memcmp() is usually a platform-specific implementation
+ * written in assembler. for example one in /usr/lib/libc/libc_hwcap*.so.1.
+ * on Solaris, or on Windows inside C runtime linrary.
+ *
+ * On Solaris, native implementation is also usually faster than the
+ * built-in memcmp supplied by GCC, so it is recommended to build
+ * with "-fno-builtin-memcmp"in CFLAGS if building with GCC on Solaris.
+ */
+
+/*
+ Daniel Blacks tests shows that libc memcmp is generally faster than
+ ptr_cmp() at least of x86 and power8 platforms, so we use the libc
+ code as deafult for now
+*/
+
+#define USE_NATIVE_MEMCMP 1
+
+#ifdef USE_NATIVE_MEMCMP
+
+#include <string.h>
+
+static int native_compare(size_t *length, unsigned char **a, unsigned char **b)
+{
+ return memcmp(*a, *b, *length);
+}
+
+qsort2_cmp get_ptr_compare (size_t size __attribute__((unused)))
+{
+ return (qsort2_cmp) native_compare;
+}
+
+#else /* USE_NATIVE_MEMCMP */
+
+static int ptr_compare(size_t *compare_length, uchar **a, uchar **b);
+static int ptr_compare_0(size_t *compare_length, uchar **a, uchar **b);
+static int ptr_compare_1(size_t *compare_length, uchar **a, uchar **b);
+static int ptr_compare_2(size_t *compare_length, uchar **a, uchar **b);
+static int ptr_compare_3(size_t *compare_length, uchar **a, uchar **b);
+static int degenerate_compare_func(size_t *compare_length, uchar **a, uchar **b)
+{
+ DBUG_ASSERT(*compare_length == 0);
+ return 0;
+}
+
+qsort2_cmp get_ptr_compare (size_t size)
+{
+ if (size == 0)
+ return (qsort2_cmp) degenerate_compare_func;
+ if (size < 4)
+ return (qsort2_cmp) ptr_compare;
+ switch (size & 3) {
+ case 0: return (qsort2_cmp) ptr_compare_0;
+ case 1: return (qsort2_cmp) ptr_compare_1;
+ case 2: return (qsort2_cmp) ptr_compare_2;
+ case 3: return (qsort2_cmp) ptr_compare_3;
+ }
+ return 0; /* Impossible */
+}
+ /*
+ Compare to keys to see witch is smaller.
+ Loop unrolled to make it quick !!
+ */
+
+#define cmp(N) if (first[N] != last[N]) return (int) first[N] - (int) last[N]
+
+static int ptr_compare(size_t *compare_length, uchar **a, uchar **b)
+{
+ size_t length= *compare_length;
+ uchar *first,*last;
+
+ DBUG_ASSERT(length > 0);
+ first= *a; last= *b;
+ while (--length)
+ {
+ if (*first++ != *last++)
+ return (int) first[-1] - (int) last[-1];
+ }
+ return (int) first[0] - (int) last[0];
+}
+
+
+static int ptr_compare_0(size_t *compare_length,uchar **a, uchar **b)
+{
+ size_t length= *compare_length;
+ uchar *first,*last;
+
+ first= *a; last= *b;
+ loop:
+ cmp(0);
+ cmp(1);
+ cmp(2);
+ cmp(3);
+ if ((length-=4))
+ {
+ first+=4;
+ last+=4;
+ goto loop;
+ }
+ return (0);
+}
+
+
+static int ptr_compare_1(size_t *compare_length,uchar **a, uchar **b)
+{
+ size_t length= *compare_length-1;
+ uchar *first,*last;
+
+ first= *a+1; last= *b+1;
+ cmp(-1);
+ loop:
+ cmp(0);
+ cmp(1);
+ cmp(2);
+ cmp(3);
+ if ((length-=4))
+ {
+ first+=4;
+ last+=4;
+ goto loop;
+ }
+ return (0);
+}
+
+static int ptr_compare_2(size_t *compare_length,uchar **a, uchar **b)
+{
+ size_t length= *compare_length-2;
+ uchar *first,*last;
+
+ first= *a +2 ; last= *b +2;
+ cmp(-2);
+ cmp(-1);
+ loop:
+ cmp(0);
+ cmp(1);
+ cmp(2);
+ cmp(3);
+ if ((length-=4))
+ {
+ first+=4;
+ last+=4;
+ goto loop;
+ }
+ return (0);
+}
+
+static int ptr_compare_3(size_t *compare_length,uchar **a, uchar **b)
+{
+ size_t length= *compare_length-3;
+ uchar *first,*last;
+
+ first= *a +3 ; last= *b +3;
+ cmp(-3);
+ cmp(-2);
+ cmp(-1);
+ loop:
+ cmp(0);
+ cmp(1);
+ cmp(2);
+ cmp(3);
+ if ((length-=4))
+ {
+ first+=4;
+ last+=4;
+ goto loop;
+ }
+ return (0);
+}
+
+#endif /* USE_NATIVE_MEMCMP */
+
+void my_store_ptr(uchar *buff, size_t pack_length, my_off_t pos)
+{
+ switch (pack_length) {
+#if SIZEOF_OFF_T > 4
+ case 8: mi_int8store(buff,pos); break;
+ case 7: mi_int7store(buff,pos); break;
+ case 6: mi_int6store(buff,pos); break;
+ case 5: mi_int5store(buff,pos); break;
+#endif
+ case 4: mi_int4store(buff,pos); break;
+ case 3: mi_int3store(buff,pos); break;
+ case 2: mi_int2store(buff,pos); break;
+ case 1: buff[0]= (uchar) pos; break;
+ default: DBUG_ASSERT(0);
+ }
+ return;
+}
+
+my_off_t my_get_ptr(uchar *ptr, size_t pack_length)
+{
+ my_off_t pos;
+ switch (pack_length) {
+#if SIZEOF_OFF_T > 4
+ case 8: pos= (my_off_t) mi_uint8korr(ptr); break;
+ case 7: pos= (my_off_t) mi_uint7korr(ptr); break;
+ case 6: pos= (my_off_t) mi_uint6korr(ptr); break;
+ case 5: pos= (my_off_t) mi_uint5korr(ptr); break;
+#endif
+ case 4: pos= (my_off_t) mi_uint4korr(ptr); break;
+ case 3: pos= (my_off_t) mi_uint3korr(ptr); break;
+ case 2: pos= (my_off_t) mi_uint2korr(ptr); break;
+ case 1: pos= (my_off_t) *(uchar*) ptr; break;
+ default: DBUG_ASSERT(0); return 0;
+ }
+ return pos;
+}