thodg/libgit2/src/hash/sha1/generic.c
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Hash : 8832172e
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Date : 2019-02-22T14:32:40
hash: move SHA1 implementations to its own hashing context Create a separate `git_hash_sha1_ctx` structure that is specific to the SHA1 implementation and move all SHA1 functions over to use that one instead of the generic `git_hash_ctx`. The `git_hash_ctx` for now simply has a union containing this single SHA1 implementation, only, without any mechanism to distinguish between different algortihms.
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src/hash/sha1/generic.c
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/* * Copyright (C) the libgit2 contributors. All rights reserved. * * This file is part of libgit2, distributed under the GNU GPL v2 with * a Linking Exception. For full terms see the included COPYING file. */ #include "generic.h" #if defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__)) /* * Force usage of rol or ror by selecting the one with the smaller constant. * It _can_ generate slightly smaller code (a constant of 1 is special), but * perhaps more importantly it's possibly faster on any uarch that does a * rotate with a loop. */ #define SHA_ASM(op, x, n) (__extension__ ({ unsigned int __res; __asm__(op " %1,%0":"=r" (__res):"i" (n), "0" (x)); __res; })) #define SHA_ROL(x,n) SHA_ASM("rol", x, n) #define SHA_ROR(x,n) SHA_ASM("ror", x, n) #else #define SHA_ROT(X,l,r) (((X) << (l)) | ((X) >> (r))) #define SHA_ROL(X,n) SHA_ROT(X,n,32-(n)) #define SHA_ROR(X,n) SHA_ROT(X,32-(n),n) #endif /* * If you have 32 registers or more, the compiler can (and should) * try to change the array[] accesses into registers. However, on * machines with less than ~25 registers, that won't really work, * and at least gcc will make an unholy mess of it. * * So to avoid that mess which just slows things down, we force * the stores to memory to actually happen (we might be better off * with a 'W(t)=(val);asm("":"+m" (W(t))' there instead, as * suggested by Artur Skawina - that will also make gcc unable to * try to do the silly "optimize away loads" part because it won't * see what the value will be). * * Ben Herrenschmidt reports that on PPC, the C version comes close * to the optimized asm with this (ie on PPC you don't want that * 'volatile', since there are lots of registers). * * On ARM we get the best code generation by forcing a full memory barrier * between each SHA_ROUND, otherwise gcc happily get wild with spilling and * the stack frame size simply explode and performance goes down the drain. */ #if defined(__i386__) || defined(__x86_64__) #define setW(x, val) (*(volatile unsigned int *)&W(x) = (val)) #elif defined(__GNUC__) && defined(__arm__) #define setW(x, val) do { W(x) = (val); __asm__("":::"memory"); } while (0) #else #define setW(x, val) (W(x) = (val)) #endif /* * Performance might be improved if the CPU architecture is OK with * unaligned 32-bit loads and a fast ntohl() is available. * Otherwise fall back to byte loads and shifts which is portable, * and is faster on architectures with memory alignment issues. */ #if defined(__i386__) || defined(__x86_64__) || \ defined(_M_IX86) || defined(_M_X64) || \ defined(__ppc__) || defined(__ppc64__) || \ defined(__powerpc__) || defined(__powerpc64__) || \ defined(__s390__) || defined(__s390x__) #define get_be32(p) ntohl(*(const unsigned int *)(p)) #define put_be32(p, v) do { *(unsigned int *)(p) = htonl(v); } while (0) #else #define get_be32(p) ( \ (*((const unsigned char *)(p) + 0) << 24) | \ (*((const unsigned char *)(p) + 1) << 16) | \ (*((const unsigned char *)(p) + 2) << 8) | \ (*((const unsigned char *)(p) + 3) << 0) ) #define put_be32(p, v) do { \ unsigned int __v = (v); \ *((unsigned char *)(p) + 0) = __v >> 24; \ *((unsigned char *)(p) + 1) = __v >> 16; \ *((unsigned char *)(p) + 2) = __v >> 8; \ *((unsigned char *)(p) + 3) = __v >> 0; } while (0) #endif /* This "rolls" over the 512-bit array */ #define W(x) (array[(x)&15]) /* * Where do we get the source from? The first 16 iterations get it from * the input data, the next mix it from the 512-bit array. */ #define SHA_SRC(t) get_be32(data + t) #define SHA_MIX(t) SHA_ROL(W(t+13) ^ W(t+8) ^ W(t+2) ^ W(t), 1) #define SHA_ROUND(t, input, fn, constant, A, B, C, D, E) do { \ unsigned int TEMP = input(t); setW(t, TEMP); \ E += TEMP + SHA_ROL(A,5) + (fn) + (constant); \ B = SHA_ROR(B, 2); } while (0) #define T_0_15(t, A, B, C, D, E) SHA_ROUND(t, SHA_SRC, (((C^D)&B)^D) , 0x5a827999, A, B, C, D, E ) #define T_16_19(t, A, B, C, D, E) SHA_ROUND(t, SHA_MIX, (((C^D)&B)^D) , 0x5a827999, A, B, C, D, E ) #define T_20_39(t, A, B, C, D, E) SHA_ROUND(t, SHA_MIX, (B^C^D) , 0x6ed9eba1, A, B, C, D, E ) #define T_40_59(t, A, B, C, D, E) SHA_ROUND(t, SHA_MIX, ((B&C)+(D&(B^C))) , 0x8f1bbcdc, A, B, C, D, E ) #define T_60_79(t, A, B, C, D, E) SHA_ROUND(t, SHA_MIX, (B^C^D) , 0xca62c1d6, A, B, C, D, E ) static void hash__block(git_hash_sha1_ctx *ctx, const unsigned int *data) { unsigned int A,B,C,D,E; unsigned int array[16]; A = ctx->H[0]; B = ctx->H[1]; C = ctx->H[2]; D = ctx->H[3]; E = ctx->H[4]; /* Round 1 - iterations 0-16 take their input from 'data' */ T_0_15( 0, A, B, C, D, E); T_0_15( 1, E, A, B, C, D); T_0_15( 2, D, E, A, B, C); T_0_15( 3, C, D, E, A, B); T_0_15( 4, B, C, D, E, A); T_0_15( 5, A, B, C, D, E); T_0_15( 6, E, A, B, C, D); T_0_15( 7, D, E, A, B, C); T_0_15( 8, C, D, E, A, B); T_0_15( 9, B, C, D, E, A); T_0_15(10, A, B, C, D, E); T_0_15(11, E, A, B, C, D); T_0_15(12, D, E, A, B, C); T_0_15(13, C, D, E, A, B); T_0_15(14, B, C, D, E, A); T_0_15(15, A, B, C, D, E); /* Round 1 - tail. Input from 512-bit mixing array */ T_16_19(16, E, A, B, C, D); T_16_19(17, D, E, A, B, C); T_16_19(18, C, D, E, A, B); T_16_19(19, B, C, D, E, A); /* Round 2 */ T_20_39(20, A, B, C, D, E); T_20_39(21, E, A, B, C, D); T_20_39(22, D, E, A, B, C); T_20_39(23, C, D, E, A, B); T_20_39(24, B, C, D, E, A); T_20_39(25, A, B, C, D, E); T_20_39(26, E, A, B, C, D); T_20_39(27, D, E, A, B, C); T_20_39(28, C, D, E, A, B); T_20_39(29, B, C, D, E, A); T_20_39(30, A, B, C, D, E); T_20_39(31, E, A, B, C, D); T_20_39(32, D, E, A, B, C); T_20_39(33, C, D, E, A, B); T_20_39(34, B, C, D, E, A); T_20_39(35, A, B, C, D, E); T_20_39(36, E, A, B, C, D); T_20_39(37, D, E, A, B, C); T_20_39(38, C, D, E, A, B); T_20_39(39, B, C, D, E, A); /* Round 3 */ T_40_59(40, A, B, C, D, E); T_40_59(41, E, A, B, C, D); T_40_59(42, D, E, A, B, C); T_40_59(43, C, D, E, A, B); T_40_59(44, B, C, D, E, A); T_40_59(45, A, B, C, D, E); T_40_59(46, E, A, B, C, D); T_40_59(47, D, E, A, B, C); T_40_59(48, C, D, E, A, B); T_40_59(49, B, C, D, E, A); T_40_59(50, A, B, C, D, E); T_40_59(51, E, A, B, C, D); T_40_59(52, D, E, A, B, C); T_40_59(53, C, D, E, A, B); T_40_59(54, B, C, D, E, A); T_40_59(55, A, B, C, D, E); T_40_59(56, E, A, B, C, D); T_40_59(57, D, E, A, B, C); T_40_59(58, C, D, E, A, B); T_40_59(59, B, C, D, E, A); /* Round 4 */ T_60_79(60, A, B, C, D, E); T_60_79(61, E, A, B, C, D); T_60_79(62, D, E, A, B, C); T_60_79(63, C, D, E, A, B); T_60_79(64, B, C, D, E, A); T_60_79(65, A, B, C, D, E); T_60_79(66, E, A, B, C, D); T_60_79(67, D, E, A, B, C); T_60_79(68, C, D, E, A, B); T_60_79(69, B, C, D, E, A); T_60_79(70, A, B, C, D, E); T_60_79(71, E, A, B, C, D); T_60_79(72, D, E, A, B, C); T_60_79(73, C, D, E, A, B); T_60_79(74, B, C, D, E, A); T_60_79(75, A, B, C, D, E); T_60_79(76, E, A, B, C, D); T_60_79(77, D, E, A, B, C); T_60_79(78, C, D, E, A, B); T_60_79(79, B, C, D, E, A); ctx->H[0] += A; ctx->H[1] += B; ctx->H[2] += C; ctx->H[3] += D; ctx->H[4] += E; } int git_hash_sha1_global_init(void) { return 0; } int git_hash_sha1_ctx_init(git_hash_sha1_ctx *ctx) { return git_hash_sha1_init(ctx); } void git_hash_sha1_ctx_cleanup(git_hash_sha1_ctx *ctx) { GIT_UNUSED(ctx); } int git_hash_sha1_init(git_hash_sha1_ctx *ctx) { ctx->size = 0; /* Initialize H with the magic constants (see FIPS180 for constants) */ ctx->H[0] = 0x67452301; ctx->H[1] = 0xefcdab89; ctx->H[2] = 0x98badcfe; ctx->H[3] = 0x10325476; ctx->H[4] = 0xc3d2e1f0; return 0; } int git_hash_sha1_update(git_hash_sha1_ctx *ctx, const void *data, size_t len) { unsigned int lenW = ctx->size & 63; ctx->size += len; /* Read the data into W and process blocks as they get full */ if (lenW) { unsigned int left = 64 - lenW; if (len < left) left = (unsigned int)len; memcpy(lenW + (char *)ctx->W, data, left); lenW = (lenW + left) & 63; len -= left; data = ((const char *)data + left); if (lenW) return 0; hash__block(ctx, ctx->W); } while (len >= 64) { hash__block(ctx, data); data = ((const char *)data + 64); len -= 64; } if (len) memcpy(ctx->W, data, len); return 0; } int git_hash_sha1_final(git_oid *out, git_hash_sha1_ctx *ctx) { static const unsigned char pad[64] = { 0x80 }; unsigned int padlen[2]; int i; /* Pad with a binary 1 (ie 0x80), then zeroes, then length */ padlen[0] = htonl((uint32_t)(ctx->size >> 29)); padlen[1] = htonl((uint32_t)(ctx->size << 3)); i = ctx->size & 63; git_hash_sha1_update(ctx, pad, 1+ (63 & (55 - i))); git_hash_sha1_update(ctx, padlen, 8); /* Output hash */ for (i = 0; i < 5; i++) put_be32(out->id + i*4, ctx->H[i]); return 0; }