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Diffstat (limited to 'mysys/ptr_cmp.c')
| -rw-r--r-- | mysys/ptr_cmp.c | 231 |
1 files changed, 231 insertions, 0 deletions
diff --git a/mysys/ptr_cmp.c b/mysys/ptr_cmp.c new file mode 100644 index 00000000..7ea15baf --- /dev/null +++ b/mysys/ptr_cmp.c @@ -0,0 +1,231 @@ +/* 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; +} |