hash.h

   1 #ifndef HASH_H
   2 #define HASH_H
   3
   4 #include "git-compat-util.h"
   5 #include "repository.h"
   6
   7 #if defined(SHA1_PPC)
   8 #include "ppc/sha1.h"
   9 #elif defined(SHA1_APPLE)
  10 #include <CommonCrypto/CommonDigest.h>
  11 #elif defined(SHA1_OPENSSL)
  12 #include <openssl/sha.h>
  13 #elif defined(SHA1_DC)
  14 #include "sha1dc_git.h"
  15 #else /* SHA1_BLK */
  16 #include "block-sha1/sha1.h"
  17 #endif
  18
  19 #if defined(SHA256_GCRYPT)
  20 #define SHA256_NEEDS_CLONE_HELPER
  21 #include "sha256/gcrypt.h"
  22 #elif defined(SHA256_OPENSSL)
  23 #include <openssl/sha.h>
  24 #else
  25 #include "sha256/block/sha256.h"
  26 #endif
  27
  28 #ifndef platform_SHA_CTX
  29 /*
  30  * platform's underlying implementation of SHA-1; could be OpenSSL,
  31  * blk_SHA, Apple CommonCrypto, etc...  Note that the relevant
  32  * SHA-1 header may have already defined platform_SHA_CTX for our
  33  * own implementations like block-sha1 and ppc-sha1, so we list
  34  * the default for OpenSSL compatible SHA-1 implementations here.
  35  */
  36 #define platform_SHA_CTX        SHA_CTX
  37 #define platform_SHA1_Init      SHA1_Init
  38 #define platform_SHA1_Update    SHA1_Update
  39 #define platform_SHA1_Final     SHA1_Final
  40 #endif
  41
  42 #define git_SHA_CTX             platform_SHA_CTX
  43 #define git_SHA1_Init           platform_SHA1_Init
  44 #define git_SHA1_Update         platform_SHA1_Update
  45 #define git_SHA1_Final          platform_SHA1_Final
  46
  47 #ifndef platform_SHA256_CTX
  48 #define platform_SHA256_CTX     SHA256_CTX
  49 #define platform_SHA256_Init    SHA256_Init
  50 #define platform_SHA256_Update  SHA256_Update
  51 #define platform_SHA256_Final   SHA256_Final
  52 #endif
  53
  54 #define git_SHA256_CTX          platform_SHA256_CTX
  55 #define git_SHA256_Init         platform_SHA256_Init
  56 #define git_SHA256_Update       platform_SHA256_Update
  57 #define git_SHA256_Final        platform_SHA256_Final
  58
  59 #ifdef platform_SHA256_Clone
  60 #define git_SHA256_Clone        platform_SHA256_Clone
  61 #endif
  62
  63 #ifdef SHA1_MAX_BLOCK_SIZE
  64 #include "compat/sha1-chunked.h"
  65 #undef git_SHA1_Update
  66 #define git_SHA1_Update         git_SHA1_Update_Chunked
  67 #endif
  68
  69 static inline void git_SHA1_Clone(git_SHA_CTX *dst, const git_SHA_CTX *src)
  70 {
  71         memcpy(dst, src, sizeof(*dst));
  72 }
  73
  74 #ifndef SHA256_NEEDS_CLONE_HELPER
  75 static inline void git_SHA256_Clone(git_SHA256_CTX *dst, const git_SHA256_CTX *src)
  76 {
  77         memcpy(dst, src, sizeof(*dst));
  78 }
  79 #endif
  80
  81 /*
  82  * Note that these constants are suitable for indexing the hash_algos array and
  83  * comparing against each other, but are otherwise arbitrary, so they should not
  84  * be exposed to the user or serialized to disk.  To know whether a
  85  * git_hash_algo struct points to some usable hash function, test the format_id
  86  * field for being non-zero.  Use the name field for user-visible situations and
  87  * the format_id field for fixed-length fields on disk.
  88  */
  89 /* An unknown hash function. */
  90 #define GIT_HASH_UNKNOWN 0
  91 /* SHA-1 */
  92 #define GIT_HASH_SHA1 1
  93 /* SHA-256  */
  94 #define GIT_HASH_SHA256 2
  95 /* Number of algorithms supported (including unknown). */
  96 #define GIT_HASH_NALGOS (GIT_HASH_SHA256 + 1)
  97
  98 /* A suitably aligned type for stack allocations of hash contexts. */
  99 union git_hash_ctx {
 100         git_SHA_CTX sha1;
 101         git_SHA256_CTX sha256;
 102 };
 103 typedef union git_hash_ctx git_hash_ctx;
 104
 105 typedef void (*git_hash_init_fn)(git_hash_ctx *ctx);
 106 typedef void (*git_hash_clone_fn)(git_hash_ctx *dst, const git_hash_ctx *src);
 107 typedef void (*git_hash_update_fn)(git_hash_ctx *ctx, const void *in, size_t len);
 108 typedef void (*git_hash_final_fn)(unsigned char *hash, git_hash_ctx *ctx);
 109
 110 struct git_hash_algo {
 111         /*
 112          * The name of the algorithm, as appears in the config file and in
 113          * messages.
 114          */
 115         const char *name;
 116
 117         /* A four-byte version identifier, used in pack indices. */
 118         uint32_t format_id;
 119
 120         /* The length of the hash in binary. */
 121         size_t rawsz;
 122
 123         /* The length of the hash in hex characters. */
 124         size_t hexsz;
 125
 126         /* The block size of the hash. */
 127         size_t blksz;
 128
 129         /* The hash initialization function. */
 130         git_hash_init_fn init_fn;
 131
 132         /* The hash context cloning function. */
 133         git_hash_clone_fn clone_fn;
 134
 135         /* The hash update function. */
 136         git_hash_update_fn update_fn;
 137
 138         /* The hash finalization function. */
 139         git_hash_final_fn final_fn;
 140
 141         /* The OID of the empty tree. */
 142         const struct object_id *empty_tree;
 143
 144         /* The OID of the empty blob. */
 145         const struct object_id *empty_blob;
 146 };
 147 extern const struct git_hash_algo hash_algos[GIT_HASH_NALGOS];
 148
 149 /*
 150  * Return a GIT_HASH_* constant based on the name.  Returns GIT_HASH_UNKNOWN if
 151  * the name doesn't match a known algorithm.
 152  */
 153 int hash_algo_by_name(const char *name);
 154 /* Identical, except based on the format ID. */
 155 int hash_algo_by_id(uint32_t format_id);
 156 /* Identical, except based on the length. */
 157 int hash_algo_by_length(int len);
 158 /* Identical, except for a pointer to struct git_hash_algo. */
 159 static inline int hash_algo_by_ptr(const struct git_hash_algo *p)
 160 {
 161         return p - hash_algos;
 162 }
 163
 164 /* The length in bytes and in hex digits of an object name (SHA-1 value). */
 165 #define GIT_SHA1_RAWSZ 20
 166 #define GIT_SHA1_HEXSZ (2 * GIT_SHA1_RAWSZ)
 167 /* The block size of SHA-1. */
 168 #define GIT_SHA1_BLKSZ 64
 169
 170 /* The length in bytes and in hex digits of an object name (SHA-256 value). */
 171 #define GIT_SHA256_RAWSZ 32
 172 #define GIT_SHA256_HEXSZ (2 * GIT_SHA256_RAWSZ)
 173 /* The block size of SHA-256. */
 174 #define GIT_SHA256_BLKSZ 64
 175
 176 /* The length in byte and in hex digits of the largest possible hash value. */
 177 #define GIT_MAX_RAWSZ GIT_SHA256_RAWSZ
 178 #define GIT_MAX_HEXSZ GIT_SHA256_HEXSZ
 179 /* The largest possible block size for any supported hash. */
 180 #define GIT_MAX_BLKSZ GIT_SHA256_BLKSZ
 181
 182 struct object_id {
 183         unsigned char hash[GIT_MAX_RAWSZ];
 184 };
 185
 186 #define the_hash_algo the_repository->hash_algo
 187
 188 extern const struct object_id null_oid;
 189
 190 static inline int hashcmp(const unsigned char *sha1, const unsigned char *sha2)
 191 {
 192         /*
 193          * Teach the compiler that there are only two possibilities of hash size
 194          * here, so that it can optimize for this case as much as possible.
 195          */
 196         if (the_hash_algo->rawsz == GIT_MAX_RAWSZ)
 197                 return memcmp(sha1, sha2, GIT_MAX_RAWSZ);
 198         return memcmp(sha1, sha2, GIT_SHA1_RAWSZ);
 199 }
 200
 201 static inline int oidcmp(const struct object_id *oid1, const struct object_id *oid2)
 202 {
 203         return hashcmp(oid1->hash, oid2->hash);
 204 }
 205
 206 static inline int hasheq(const unsigned char *sha1, const unsigned char *sha2)
 207 {
 208         /*
 209          * We write this here instead of deferring to hashcmp so that the
 210          * compiler can properly inline it and avoid calling memcmp.
 211          */
 212         if (the_hash_algo->rawsz == GIT_MAX_RAWSZ)
 213                 return !memcmp(sha1, sha2, GIT_MAX_RAWSZ);
 214         return !memcmp(sha1, sha2, GIT_SHA1_RAWSZ);
 215 }
 216
 217 static inline int oideq(const struct object_id *oid1, const struct object_id *oid2)
 218 {
 219         return hasheq(oid1->hash, oid2->hash);
 220 }
 221
 222 static inline int is_null_oid(const struct object_id *oid)
 223 {
 224         return oideq(oid, &null_oid);
 225 }
 226
 227 static inline void hashcpy(unsigned char *sha_dst, const unsigned char *sha_src)
 228 {
 229         memcpy(sha_dst, sha_src, the_hash_algo->rawsz);
 230 }
 231
 232 static inline void oidcpy(struct object_id *dst, const struct object_id *src)
 233 {
 234         memcpy(dst->hash, src->hash, GIT_MAX_RAWSZ);
 235 }
 236
 237 static inline struct object_id *oiddup(const struct object_id *src)
 238 {
 239         struct object_id *dst = xmalloc(sizeof(struct object_id));
 240         oidcpy(dst, src);
 241         return dst;
 242 }
 243
 244 static inline void hashclr(unsigned char *hash)
 245 {
 246         memset(hash, 0, the_hash_algo->rawsz);
 247 }
 248
 249 static inline void oidclr(struct object_id *oid)
 250 {
 251         memset(oid->hash, 0, GIT_MAX_RAWSZ);
 252 }
 253
 254 static inline void oidread(struct object_id *oid, const unsigned char *hash)
 255 {
 256         memcpy(oid->hash, hash, the_hash_algo->rawsz);
 257 }
 258
 259 static inline int is_empty_blob_sha1(const unsigned char *sha1)
 260 {
 261         return hasheq(sha1, the_hash_algo->empty_blob->hash);
 262 }
 263
 264 static inline int is_empty_blob_oid(const struct object_id *oid)
 265 {
 266         return oideq(oid, the_hash_algo->empty_blob);
 267 }
 268
 269 static inline int is_empty_tree_sha1(const unsigned char *sha1)
 270 {
 271         return hasheq(sha1, the_hash_algo->empty_tree->hash);
 272 }
 273
 274 static inline int is_empty_tree_oid(const struct object_id *oid)
 275 {
 276         return oideq(oid, the_hash_algo->empty_tree);
 277 }
 278
 279 const char *empty_tree_oid_hex(void);
 280 const char *empty_blob_oid_hex(void);
 281
 282 #endif