make sure byte swapping is optimal for git
[git/git.git] / block-sha1 / sha1.c
CommitLineData
d7c208a9
LT
1/*
2 * Based on the Mozilla SHA1 (see mozilla-sha1/sha1.c),
3 * optimized to do word accesses rather than byte accesses,
4 * and to avoid unnecessary copies into the context array.
5 */
6
51ea5519
NP
7/* this is only to get definitions for memcpy(), ntohl() and htonl() */
8#include "../git-compat-util.h"
d7c208a9
LT
9
10#include "sha1.h"
11
b8e48a89
LT
12#if defined(__i386__) || defined(__x86_64__)
13
dc52fd29
NP
14/*
15 * Force usage of rol or ror by selecting the one with the smaller constant.
16 * It _can_ generate slightly smaller code (a constant of 1 is special), but
17 * perhaps more importantly it's possibly faster on any uarch that does a
18 * rotate with a loop.
19 */
20
fd536d34 21#define SHA_ASM(op, x, n) ({ unsigned int __res; __asm__(op " %1,%0":"=r" (__res):"i" (n), "0" (x)); __res; })
b8e48a89
LT
22#define SHA_ROL(x,n) SHA_ASM("rol", x, n)
23#define SHA_ROR(x,n) SHA_ASM("ror", x, n)
24
25#else
26
fd536d34 27#define SHA_ROT(X,l,r) (((X) << (l)) | ((X) >> (r)))
b8e48a89
LT
28#define SHA_ROL(X,n) SHA_ROT(X,n,32-(n))
29#define SHA_ROR(X,n) SHA_ROT(X,32-(n),n)
30
31#endif
d7c208a9 32
926172c5
LT
33/*
34 * If you have 32 registers or more, the compiler can (and should)
35 * try to change the array[] accesses into registers. However, on
36 * machines with less than ~25 registers, that won't really work,
37 * and at least gcc will make an unholy mess of it.
38 *
39 * So to avoid that mess which just slows things down, we force
40 * the stores to memory to actually happen (we might be better off
41 * with a 'W(t)=(val);asm("":"+m" (W(t))' there instead, as
42 * suggested by Artur Skawina - that will also make gcc unable to
43 * try to do the silly "optimize away loads" part because it won't
44 * see what the value will be).
45 *
46 * Ben Herrenschmidt reports that on PPC, the C version comes close
47 * to the optimized asm with this (ie on PPC you don't want that
48 * 'volatile', since there are lots of registers).
dc52fd29
NP
49 *
50 * On ARM we get the best code generation by forcing a full memory barrier
51 * between each SHA_ROUND, otherwise gcc happily get wild with spilling and
52 * the stack frame size simply explode and performance goes down the drain.
926172c5 53 */
dc52fd29
NP
54
55#if defined(__i386__) || defined(__x86_64__)
926172c5 56 #define setW(x, val) (*(volatile unsigned int *)&W(x) = (val))
dc52fd29
NP
57#elif defined(__arm__)
58 #define setW(x, val) do { W(x) = (val); __asm__("":::"memory"); } while (0)
926172c5
LT
59#else
60 #define setW(x, val) (W(x) = (val))
61#endif
ab14c823 62
660231aa
NP
63/*
64 * Performance might be improved if the CPU architecture is OK with
65 * unaligned 32-bit loads and a fast ntohl() is available.
66 * Otherwise fall back to byte loads and shifts which is portable,
67 * and is faster on architectures with memory alignment issues.
68 */
69
ee7dc310
NP
70#if defined(__i386__) || defined(__x86_64__) || \
71 defined(__ppc__) || defined(__ppc64__) || \
72 defined(__powerpc__) || defined(__powerpc64__) || \
73 defined(__s390__) || defined(__s390x__)
660231aa
NP
74
75#define get_be32(p) ntohl(*(unsigned int *)(p))
76#define put_be32(p, v) do { *(unsigned int *)(p) = htonl(v); } while (0)
77
78#else
79
80#define get_be32(p) ( \
81 (*((unsigned char *)(p) + 0) << 24) | \
82 (*((unsigned char *)(p) + 1) << 16) | \
83 (*((unsigned char *)(p) + 2) << 8) | \
84 (*((unsigned char *)(p) + 3) << 0) )
85#define put_be32(p, v) do { \
86 unsigned int __v = (v); \
87 *((unsigned char *)(p) + 0) = __v >> 24; \
88 *((unsigned char *)(p) + 1) = __v >> 16; \
89 *((unsigned char *)(p) + 2) = __v >> 8; \
90 *((unsigned char *)(p) + 3) = __v >> 0; } while (0)
91
92#endif
93
dc52fd29
NP
94/* This "rolls" over the 512-bit array */
95#define W(x) (array[(x)&15])
96
ab14c823
LT
97/*
98 * Where do we get the source from? The first 16 iterations get it from
99 * the input data, the next mix it from the 512-bit array.
100 */
660231aa 101#define SHA_SRC(t) get_be32(data + t)
ab14c823
LT
102#define SHA_MIX(t) SHA_ROL(W(t+13) ^ W(t+8) ^ W(t+2) ^ W(t), 1)
103
30d12d4c 104#define SHA_ROUND(t, input, fn, constant, A, B, C, D, E) do { \
66c9c6c0
LT
105 unsigned int TEMP = input(t); setW(t, TEMP); \
106 E += TEMP + SHA_ROL(A,5) + (fn) + (constant); \
107 B = SHA_ROR(B, 2); } while (0)
ab14c823 108
30d12d4c
LT
109#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 )
110#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 )
111#define T_20_39(t, A, B, C, D, E) SHA_ROUND(t, SHA_MIX, (B^C^D) , 0x6ed9eba1, A, B, C, D, E )
112#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 )
113#define T_60_79(t, A, B, C, D, E) SHA_ROUND(t, SHA_MIX, (B^C^D) , 0xca62c1d6, A, B, C, D, E )
ab14c823 114
30ba0de7 115static void blk_SHA1_Block(blk_SHA_CTX *ctx, const unsigned int *data)
d7c208a9 116{
30d12d4c 117 unsigned int A,B,C,D,E;
7b5075fc 118 unsigned int array[16];
d7c208a9 119
d7c208a9
LT
120 A = ctx->H[0];
121 B = ctx->H[1];
122 C = ctx->H[2];
123 D = ctx->H[3];
124 E = ctx->H[4];
125
ab14c823 126 /* Round 1 - iterations 0-16 take their input from 'data' */
30d12d4c
LT
127 T_0_15( 0, A, B, C, D, E);
128 T_0_15( 1, E, A, B, C, D);
129 T_0_15( 2, D, E, A, B, C);
130 T_0_15( 3, C, D, E, A, B);
131 T_0_15( 4, B, C, D, E, A);
132 T_0_15( 5, A, B, C, D, E);
133 T_0_15( 6, E, A, B, C, D);
134 T_0_15( 7, D, E, A, B, C);
135 T_0_15( 8, C, D, E, A, B);
136 T_0_15( 9, B, C, D, E, A);
137 T_0_15(10, A, B, C, D, E);
138 T_0_15(11, E, A, B, C, D);
139 T_0_15(12, D, E, A, B, C);
140 T_0_15(13, C, D, E, A, B);
141 T_0_15(14, B, C, D, E, A);
142 T_0_15(15, A, B, C, D, E);
139e3456 143
ab14c823 144 /* Round 1 - tail. Input from 512-bit mixing array */
30d12d4c
LT
145 T_16_19(16, E, A, B, C, D);
146 T_16_19(17, D, E, A, B, C);
147 T_16_19(18, C, D, E, A, B);
148 T_16_19(19, B, C, D, E, A);
d7c208a9 149
ab14c823 150 /* Round 2 */
30d12d4c
LT
151 T_20_39(20, A, B, C, D, E);
152 T_20_39(21, E, A, B, C, D);
153 T_20_39(22, D, E, A, B, C);
154 T_20_39(23, C, D, E, A, B);
155 T_20_39(24, B, C, D, E, A);
156 T_20_39(25, A, B, C, D, E);
157 T_20_39(26, E, A, B, C, D);
158 T_20_39(27, D, E, A, B, C);
159 T_20_39(28, C, D, E, A, B);
160 T_20_39(29, B, C, D, E, A);
161 T_20_39(30, A, B, C, D, E);
162 T_20_39(31, E, A, B, C, D);
163 T_20_39(32, D, E, A, B, C);
164 T_20_39(33, C, D, E, A, B);
165 T_20_39(34, B, C, D, E, A);
166 T_20_39(35, A, B, C, D, E);
167 T_20_39(36, E, A, B, C, D);
168 T_20_39(37, D, E, A, B, C);
169 T_20_39(38, C, D, E, A, B);
170 T_20_39(39, B, C, D, E, A);
d7c208a9 171
ab14c823 172 /* Round 3 */
30d12d4c
LT
173 T_40_59(40, A, B, C, D, E);
174 T_40_59(41, E, A, B, C, D);
175 T_40_59(42, D, E, A, B, C);
176 T_40_59(43, C, D, E, A, B);
177 T_40_59(44, B, C, D, E, A);
178 T_40_59(45, A, B, C, D, E);
179 T_40_59(46, E, A, B, C, D);
180 T_40_59(47, D, E, A, B, C);
181 T_40_59(48, C, D, E, A, B);
182 T_40_59(49, B, C, D, E, A);
183 T_40_59(50, A, B, C, D, E);
184 T_40_59(51, E, A, B, C, D);
185 T_40_59(52, D, E, A, B, C);
186 T_40_59(53, C, D, E, A, B);
187 T_40_59(54, B, C, D, E, A);
188 T_40_59(55, A, B, C, D, E);
189 T_40_59(56, E, A, B, C, D);
190 T_40_59(57, D, E, A, B, C);
191 T_40_59(58, C, D, E, A, B);
192 T_40_59(59, B, C, D, E, A);
d7c208a9 193
ab14c823 194 /* Round 4 */
30d12d4c
LT
195 T_60_79(60, A, B, C, D, E);
196 T_60_79(61, E, A, B, C, D);
197 T_60_79(62, D, E, A, B, C);
198 T_60_79(63, C, D, E, A, B);
199 T_60_79(64, B, C, D, E, A);
200 T_60_79(65, A, B, C, D, E);
201 T_60_79(66, E, A, B, C, D);
202 T_60_79(67, D, E, A, B, C);
203 T_60_79(68, C, D, E, A, B);
204 T_60_79(69, B, C, D, E, A);
205 T_60_79(70, A, B, C, D, E);
206 T_60_79(71, E, A, B, C, D);
207 T_60_79(72, D, E, A, B, C);
208 T_60_79(73, C, D, E, A, B);
209 T_60_79(74, B, C, D, E, A);
210 T_60_79(75, A, B, C, D, E);
211 T_60_79(76, E, A, B, C, D);
212 T_60_79(77, D, E, A, B, C);
213 T_60_79(78, C, D, E, A, B);
214 T_60_79(79, B, C, D, E, A);
d7c208a9
LT
215
216 ctx->H[0] += A;
217 ctx->H[1] += B;
218 ctx->H[2] += C;
219 ctx->H[3] += D;
220 ctx->H[4] += E;
221}
30ba0de7
NP
222
223void blk_SHA1_Init(blk_SHA_CTX *ctx)
224{
225 ctx->size = 0;
226
227 /* Initialize H with the magic constants (see FIPS180 for constants) */
228 ctx->H[0] = 0x67452301;
229 ctx->H[1] = 0xefcdab89;
230 ctx->H[2] = 0x98badcfe;
231 ctx->H[3] = 0x10325476;
232 ctx->H[4] = 0xc3d2e1f0;
233}
234
235void blk_SHA1_Update(blk_SHA_CTX *ctx, const void *data, unsigned long len)
236{
237 int lenW = ctx->size & 63;
238
239 ctx->size += len;
240
241 /* Read the data into W and process blocks as they get full */
242 if (lenW) {
243 int left = 64 - lenW;
244 if (len < left)
245 left = len;
246 memcpy(lenW + (char *)ctx->W, data, left);
247 lenW = (lenW + left) & 63;
248 len -= left;
a1221857 249 data = ((const char *)data + left);
30ba0de7
NP
250 if (lenW)
251 return;
252 blk_SHA1_Block(ctx, ctx->W);
253 }
254 while (len >= 64) {
255 blk_SHA1_Block(ctx, data);
a1221857 256 data = ((const char *)data + 64);
30ba0de7
NP
257 len -= 64;
258 }
259 if (len)
260 memcpy(ctx->W, data, len);
261}
262
263void blk_SHA1_Final(unsigned char hashout[20], blk_SHA_CTX *ctx)
264{
265 static const unsigned char pad[64] = { 0x80 };
266 unsigned int padlen[2];
267 int i;
268
269 /* Pad with a binary 1 (ie 0x80), then zeroes, then length */
270 padlen[0] = htonl(ctx->size >> 29);
271 padlen[1] = htonl(ctx->size << 3);
272
273 i = ctx->size & 63;
274 blk_SHA1_Update(ctx, pad, 1+ (63 & (55 - i)));
275 blk_SHA1_Update(ctx, padlen, 8);
276
277 /* Output hash */
278 for (i = 0; i < 5; i++)
660231aa 279 put_be32(hashout + i*4, ctx->H[i]);
30ba0de7 280}