Eneboo - Documentación para desarrolladores
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00001 /* 00002 * pg_crc.h 00003 * 00004 * PostgreSQL CRC support 00005 * 00006 * See Ross Williams' excellent introduction 00007 * A PAINLESS GUIDE TO CRC ERROR DETECTION ALGORITHMS, available from 00008 * ftp://ftp.rocksoft.com/papers/crc_v3.txt or several other net sites. 00009 * 00010 * We use a normal (not "reflected", in Williams' terms) CRC, using initial 00011 * all-ones register contents and a final bit inversion. 00012 * 00013 * The 64-bit variant is not used as of PostgreSQL 8.1, but we retain the 00014 * code for possible future use. 00015 * 00016 * 00017 * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group 00018 * Portions Copyright (c) 1994, Regents of the University of California 00019 * 00020 * $PostgreSQL: pgsql/src/include/utils/pg_crc.h,v 1.14 2005/10/15 02:49:46 momjian Exp $ 00021 */ 00022 #ifndef PG_CRC_H 00023 #define PG_CRC_H 00024 00025 00026 typedef uint32 pg_crc32; 00027 00028 /* Initialize a CRC accumulator */ 00029 #define INIT_CRC32(crc) ((crc) = 0xFFFFFFFF) 00030 00031 /* Finish a CRC calculation */ 00032 #define FIN_CRC32(crc) ((crc) ^= 0xFFFFFFFF) 00033 00034 /* Accumulate some (more) bytes into a CRC */ 00035 #define COMP_CRC32(crc, data, len) \ 00036 do { \ 00037 unsigned char *__data = (unsigned char *) (data); \ 00038 uint32 __len = (len); \ 00039 \ 00040 while (__len-- > 0) \ 00041 { \ 00042 int __tab_index = ((int) ((crc) >> 24) ^ *__data++) & 0xFF; \ 00043 (crc) = pg_crc32_table[__tab_index] ^ ((crc) << 8); \ 00044 } \ 00045 } while (0) 00046 00047 /* Check for equality of two CRCs */ 00048 #define EQ_CRC32(c1,c2) ((c1) == (c2)) 00049 00050 /* Constant table for CRC calculation */ 00051 extern const uint32 pg_crc32_table[]; 00052 00053 00054 #ifdef PROVIDE_64BIT_CRC 00055 00056 /* 00057 * If we have a 64-bit integer type, then a 64-bit CRC looks just like the 00058 * usual sort of implementation. If we have no working 64-bit type, then 00059 * fake it with two 32-bit registers. (Note: experience has shown that the 00060 * two-32-bit-registers code is as fast as, or even much faster than, the 00061 * 64-bit code on all but true 64-bit machines. INT64_IS_BUSTED is therefore 00062 * probably the wrong control symbol to use to select the implementation.) 00063 */ 00064 00065 #ifdef INT64_IS_BUSTED 00066 00067 /* 00068 * crc0 represents the LSBs of the 64-bit value, crc1 the MSBs. Note that 00069 * with crc0 placed first, the output of 32-bit and 64-bit implementations 00070 * will be bit-compatible only on little-endian architectures. If it were 00071 * important to make the two possible implementations bit-compatible on 00072 * all machines, we could do a configure test to decide how to order the 00073 * two fields, but it seems not worth the trouble. 00074 */ 00075 typedef struct pg_crc64 00076 { 00077 uint32 crc0; 00078 uint32 crc1; 00079 } pg_crc64; 00080 00081 /* Initialize a CRC accumulator */ 00082 #define INIT_CRC64(crc) ((crc).crc0 = 0xffffffff, (crc).crc1 = 0xffffffff) 00083 00084 /* Finish a CRC calculation */ 00085 #define FIN_CRC64(crc) ((crc).crc0 ^= 0xffffffff, (crc).crc1 ^= 0xffffffff) 00086 00087 /* Accumulate some (more) bytes into a CRC */ 00088 #define COMP_CRC64(crc, data, len) \ 00089 do { \ 00090 uint32 __crc0 = (crc).crc0; \ 00091 uint32 __crc1 = (crc).crc1; \ 00092 unsigned char *__data = (unsigned char *) (data); \ 00093 uint32 __len = (len); \ 00094 \ 00095 while (__len-- > 0) \ 00096 { \ 00097 int __tab_index = ((int) (__crc1 >> 24) ^ *__data++) & 0xFF; \ 00098 __crc1 = pg_crc64_table1[__tab_index] ^ ((__crc1 << 8) | (__crc0 >> 24)); \ 00099 __crc0 = pg_crc64_table0[__tab_index] ^ (__crc0 << 8); \ 00100 } \ 00101 (crc).crc0 = __crc0; \ 00102 (crc).crc1 = __crc1; \ 00103 } while (0) 00104 00105 /* Check for equality of two CRCs */ 00106 #define EQ_CRC64(c1,c2) ((c1).crc0 == (c2).crc0 && (c1).crc1 == (c2).crc1) 00107 00108 /* Constant table for CRC calculation */ 00109 extern const uint32 pg_crc64_table0[]; 00110 extern const uint32 pg_crc64_table1[]; 00111 #else /* int64 works */ 00112 00113 typedef struct pg_crc64 00114 { 00115 uint64 crc0; 00116 } pg_crc64; 00117 00118 /* Initialize a CRC accumulator */ 00119 #define INIT_CRC64(crc) ((crc).crc0 = UINT64CONST(0xffffffffffffffff)) 00120 00121 /* Finish a CRC calculation */ 00122 #define FIN_CRC64(crc) ((crc).crc0 ^= UINT64CONST(0xffffffffffffffff)) 00123 00124 /* Accumulate some (more) bytes into a CRC */ 00125 #define COMP_CRC64(crc, data, len) \ 00126 do { \ 00127 uint64 __crc0 = (crc).crc0; \ 00128 unsigned char *__data = (unsigned char *) (data); \ 00129 uint32 __len = (len); \ 00130 \ 00131 while (__len-- > 0) \ 00132 { \ 00133 int __tab_index = ((int) (__crc0 >> 56) ^ *__data++) & 0xFF; \ 00134 __crc0 = pg_crc64_table[__tab_index] ^ (__crc0 << 8); \ 00135 } \ 00136 (crc).crc0 = __crc0; \ 00137 } while (0) 00138 00139 /* Check for equality of two CRCs */ 00140 #define EQ_CRC64(c1,c2) ((c1).crc0 == (c2).crc0) 00141 00142 /* Constant table for CRC calculation */ 00143 extern const uint64 pg_crc64_table[]; 00144 #endif /* INT64_IS_BUSTED */ 00145 #endif /* PROVIDE_64BIT_CRC */ 00146 00147 #endif /* PG_CRC_H */