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![brian m. carlson](/assets/img/avatar_default.png)
Up until recently, object IDs did not have an algorithm member, only a hash. Consequently, it was possible to share one null (all-zeros) object ID among all hash algorithms. Now that we're going to be handling objects from multiple hash algorithms, it's important to make sure that all object IDs have a correct algorithm field. Introduce a per-algorithm null OID, and add it to struct hash_algo. Introduce a wrapper function as well, and use it everywhere we used to use the null_oid constant. Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
319 lines
8.8 KiB
C
319 lines
8.8 KiB
C
#ifndef HASH_H
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#define HASH_H
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#include "git-compat-util.h"
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#include "repository.h"
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#if defined(SHA1_PPC)
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#include "ppc/sha1.h"
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#elif defined(SHA1_APPLE)
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#include <CommonCrypto/CommonDigest.h>
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#elif defined(SHA1_OPENSSL)
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#include <openssl/sha.h>
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#elif defined(SHA1_DC)
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#include "sha1dc_git.h"
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#else /* SHA1_BLK */
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#include "block-sha1/sha1.h"
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#endif
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#if defined(SHA256_GCRYPT)
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#define SHA256_NEEDS_CLONE_HELPER
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#include "sha256/gcrypt.h"
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#elif defined(SHA256_OPENSSL)
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#include <openssl/sha.h>
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#else
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#include "sha256/block/sha256.h"
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#endif
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#ifndef platform_SHA_CTX
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/*
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* platform's underlying implementation of SHA-1; could be OpenSSL,
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* blk_SHA, Apple CommonCrypto, etc... Note that the relevant
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* SHA-1 header may have already defined platform_SHA_CTX for our
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* own implementations like block-sha1 and ppc-sha1, so we list
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* the default for OpenSSL compatible SHA-1 implementations here.
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*/
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#define platform_SHA_CTX SHA_CTX
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#define platform_SHA1_Init SHA1_Init
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#define platform_SHA1_Update SHA1_Update
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#define platform_SHA1_Final SHA1_Final
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#endif
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#define git_SHA_CTX platform_SHA_CTX
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#define git_SHA1_Init platform_SHA1_Init
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#define git_SHA1_Update platform_SHA1_Update
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#define git_SHA1_Final platform_SHA1_Final
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#ifndef platform_SHA256_CTX
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#define platform_SHA256_CTX SHA256_CTX
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#define platform_SHA256_Init SHA256_Init
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#define platform_SHA256_Update SHA256_Update
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#define platform_SHA256_Final SHA256_Final
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#endif
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#define git_SHA256_CTX platform_SHA256_CTX
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#define git_SHA256_Init platform_SHA256_Init
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#define git_SHA256_Update platform_SHA256_Update
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#define git_SHA256_Final platform_SHA256_Final
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#ifdef platform_SHA256_Clone
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#define git_SHA256_Clone platform_SHA256_Clone
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#endif
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#ifdef SHA1_MAX_BLOCK_SIZE
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#include "compat/sha1-chunked.h"
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#undef git_SHA1_Update
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#define git_SHA1_Update git_SHA1_Update_Chunked
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#endif
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static inline void git_SHA1_Clone(git_SHA_CTX *dst, const git_SHA_CTX *src)
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{
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memcpy(dst, src, sizeof(*dst));
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}
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#ifndef SHA256_NEEDS_CLONE_HELPER
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static inline void git_SHA256_Clone(git_SHA256_CTX *dst, const git_SHA256_CTX *src)
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{
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memcpy(dst, src, sizeof(*dst));
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}
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#endif
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/*
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* Note that these constants are suitable for indexing the hash_algos array and
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* comparing against each other, but are otherwise arbitrary, so they should not
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* be exposed to the user or serialized to disk. To know whether a
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* git_hash_algo struct points to some usable hash function, test the format_id
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* field for being non-zero. Use the name field for user-visible situations and
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* the format_id field for fixed-length fields on disk.
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*/
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/* An unknown hash function. */
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#define GIT_HASH_UNKNOWN 0
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/* SHA-1 */
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#define GIT_HASH_SHA1 1
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/* SHA-256 */
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#define GIT_HASH_SHA256 2
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/* Number of algorithms supported (including unknown). */
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#define GIT_HASH_NALGOS (GIT_HASH_SHA256 + 1)
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/* The length in bytes and in hex digits of an object name (SHA-1 value). */
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#define GIT_SHA1_RAWSZ 20
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#define GIT_SHA1_HEXSZ (2 * GIT_SHA1_RAWSZ)
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/* The block size of SHA-1. */
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#define GIT_SHA1_BLKSZ 64
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/* The length in bytes and in hex digits of an object name (SHA-256 value). */
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#define GIT_SHA256_RAWSZ 32
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#define GIT_SHA256_HEXSZ (2 * GIT_SHA256_RAWSZ)
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/* The block size of SHA-256. */
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#define GIT_SHA256_BLKSZ 64
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/* The length in byte and in hex digits of the largest possible hash value. */
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#define GIT_MAX_RAWSZ GIT_SHA256_RAWSZ
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#define GIT_MAX_HEXSZ GIT_SHA256_HEXSZ
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/* The largest possible block size for any supported hash. */
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#define GIT_MAX_BLKSZ GIT_SHA256_BLKSZ
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struct object_id {
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unsigned char hash[GIT_MAX_RAWSZ];
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int algo;
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};
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/* A suitably aligned type for stack allocations of hash contexts. */
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union git_hash_ctx {
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git_SHA_CTX sha1;
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git_SHA256_CTX sha256;
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};
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typedef union git_hash_ctx git_hash_ctx;
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typedef void (*git_hash_init_fn)(git_hash_ctx *ctx);
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typedef void (*git_hash_clone_fn)(git_hash_ctx *dst, const git_hash_ctx *src);
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typedef void (*git_hash_update_fn)(git_hash_ctx *ctx, const void *in, size_t len);
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typedef void (*git_hash_final_fn)(unsigned char *hash, git_hash_ctx *ctx);
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typedef void (*git_hash_final_oid_fn)(struct object_id *oid, git_hash_ctx *ctx);
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struct git_hash_algo {
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/*
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* The name of the algorithm, as appears in the config file and in
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* messages.
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*/
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const char *name;
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/* A four-byte version identifier, used in pack indices. */
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uint32_t format_id;
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/* The length of the hash in binary. */
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size_t rawsz;
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/* The length of the hash in hex characters. */
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size_t hexsz;
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/* The block size of the hash. */
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size_t blksz;
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/* The hash initialization function. */
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git_hash_init_fn init_fn;
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/* The hash context cloning function. */
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git_hash_clone_fn clone_fn;
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/* The hash update function. */
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git_hash_update_fn update_fn;
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/* The hash finalization function. */
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git_hash_final_fn final_fn;
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/* The hash finalization function for object IDs. */
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git_hash_final_oid_fn final_oid_fn;
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/* The OID of the empty tree. */
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const struct object_id *empty_tree;
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/* The OID of the empty blob. */
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const struct object_id *empty_blob;
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/* The all-zeros OID. */
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const struct object_id *null_oid;
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};
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extern const struct git_hash_algo hash_algos[GIT_HASH_NALGOS];
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/*
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* Return a GIT_HASH_* constant based on the name. Returns GIT_HASH_UNKNOWN if
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* the name doesn't match a known algorithm.
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*/
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int hash_algo_by_name(const char *name);
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/* Identical, except based on the format ID. */
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int hash_algo_by_id(uint32_t format_id);
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/* Identical, except based on the length. */
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int hash_algo_by_length(int len);
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/* Identical, except for a pointer to struct git_hash_algo. */
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static inline int hash_algo_by_ptr(const struct git_hash_algo *p)
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{
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return p - hash_algos;
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}
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#define the_hash_algo the_repository->hash_algo
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const struct object_id *null_oid(void);
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static inline int hashcmp_algop(const unsigned char *sha1, const unsigned char *sha2, const struct git_hash_algo *algop)
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{
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/*
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* Teach the compiler that there are only two possibilities of hash size
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* here, so that it can optimize for this case as much as possible.
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*/
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if (algop->rawsz == GIT_MAX_RAWSZ)
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return memcmp(sha1, sha2, GIT_MAX_RAWSZ);
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return memcmp(sha1, sha2, GIT_SHA1_RAWSZ);
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}
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static inline int hashcmp(const unsigned char *sha1, const unsigned char *sha2)
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{
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return hashcmp_algop(sha1, sha2, the_hash_algo);
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}
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static inline int oidcmp(const struct object_id *oid1, const struct object_id *oid2)
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{
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const struct git_hash_algo *algop;
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if (!oid1->algo)
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algop = the_hash_algo;
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else
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algop = &hash_algos[oid1->algo];
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return hashcmp_algop(oid1->hash, oid2->hash, algop);
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}
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static inline int hasheq_algop(const unsigned char *sha1, const unsigned char *sha2, const struct git_hash_algo *algop)
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{
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/*
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* We write this here instead of deferring to hashcmp so that the
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* compiler can properly inline it and avoid calling memcmp.
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*/
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if (algop->rawsz == GIT_MAX_RAWSZ)
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return !memcmp(sha1, sha2, GIT_MAX_RAWSZ);
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return !memcmp(sha1, sha2, GIT_SHA1_RAWSZ);
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}
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static inline int hasheq(const unsigned char *sha1, const unsigned char *sha2)
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{
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return hasheq_algop(sha1, sha2, the_hash_algo);
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}
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static inline int oideq(const struct object_id *oid1, const struct object_id *oid2)
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{
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const struct git_hash_algo *algop;
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if (!oid1->algo)
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algop = the_hash_algo;
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else
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algop = &hash_algos[oid1->algo];
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return hasheq_algop(oid1->hash, oid2->hash, algop);
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}
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static inline int is_null_oid(const struct object_id *oid)
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{
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return oideq(oid, null_oid());
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}
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static inline void hashcpy(unsigned char *sha_dst, const unsigned char *sha_src)
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{
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memcpy(sha_dst, sha_src, the_hash_algo->rawsz);
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}
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static inline void oidcpy(struct object_id *dst, const struct object_id *src)
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{
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memcpy(dst->hash, src->hash, GIT_MAX_RAWSZ);
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dst->algo = src->algo;
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}
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static inline struct object_id *oiddup(const struct object_id *src)
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{
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struct object_id *dst = xmalloc(sizeof(struct object_id));
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oidcpy(dst, src);
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return dst;
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}
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static inline void hashclr(unsigned char *hash)
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{
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memset(hash, 0, the_hash_algo->rawsz);
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}
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static inline void oidclr(struct object_id *oid)
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{
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memset(oid->hash, 0, GIT_MAX_RAWSZ);
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oid->algo = hash_algo_by_ptr(the_hash_algo);
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}
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static inline void oidread(struct object_id *oid, const unsigned char *hash)
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{
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memcpy(oid->hash, hash, the_hash_algo->rawsz);
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oid->algo = hash_algo_by_ptr(the_hash_algo);
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}
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static inline int is_empty_blob_sha1(const unsigned char *sha1)
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{
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return hasheq(sha1, the_hash_algo->empty_blob->hash);
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}
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static inline int is_empty_blob_oid(const struct object_id *oid)
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{
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return oideq(oid, the_hash_algo->empty_blob);
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}
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static inline int is_empty_tree_sha1(const unsigned char *sha1)
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{
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return hasheq(sha1, the_hash_algo->empty_tree->hash);
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}
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static inline int is_empty_tree_oid(const struct object_id *oid)
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{
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return oideq(oid, the_hash_algo->empty_tree);
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}
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static inline void oid_set_algo(struct object_id *oid, const struct git_hash_algo *algop)
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{
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oid->algo = hash_algo_by_ptr(algop);
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}
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const char *empty_tree_oid_hex(void);
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const char *empty_blob_oid_hex(void);
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#endif
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