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hash: implement and use a context cloning function

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For all of our SHA-1 implementations and most of our SHA-256
implementations, the hash context we use is a real struct.  For these
implementations, it's possible to copy a hash context by making a copy
of the struct.

However, for our libgcrypt implementation, our hash context is a
pointer.  Consequently, copying it does not lead to an independent hash
context like we intended.

Fortunately, however, libgcrypt provides us with a handy function to
copy hash contexts.  Let's add a cloning function to the hash algorithm
API, and use it in the one place we need to make a hash context copy.
With this change, our libgcrypt SHA-256 implementation is fully
functional with all of our other hash implementations.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
brian m. carlson 2020-02-22 20:17:27 +00:00 committed by Junio C Hamano
parent 207899137d
commit 768e30ea27
4 changed files with 46 additions and 1 deletions
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2
csum-file.c
View File

@ -157,7 +157,7 @@ void hashfile_checkpoint(struct hashfile *f, struct hashfile_checkpoint *checkpo
{
hashflush(f);
checkpoint->offset = f->total;
checkpoint->ctx = f->ctx;
the_hash_algo->clone_fn(&checkpoint->ctx, &f->ctx);
}
int hashfile_truncate(struct hashfile *f, struct hashfile_checkpoint *checkpoint)

21
hash.h
View File

@ -16,6 +16,7 @@
#endif
#if defined(SHA256_GCRYPT)
#define SHA256_NEEDS_CLONE_HELPER
#include "sha256/gcrypt.h"
#elif defined(SHA256_OPENSSL)
#include <openssl/sha.h>
@ -54,12 +55,28 @@
#define git_SHA256_Update platform_SHA256_Update
#define git_SHA256_Final platform_SHA256_Final
#ifdef platform_SHA256_Clone
#define git_SHA256_Clone platform_SHA256_Clone
#endif
#ifdef SHA1_MAX_BLOCK_SIZE
#include "compat/sha1-chunked.h"
#undef git_SHA1_Update
#define git_SHA1_Update git_SHA1_Update_Chunked
#endif
static inline void git_SHA1_Clone(git_SHA_CTX *dst, const git_SHA_CTX *src)
{
memcpy(dst, src, sizeof(*dst));
}
#ifndef SHA256_NEEDS_CLONE_HELPER
static inline void git_SHA256_Clone(git_SHA256_CTX *dst, const git_SHA256_CTX *src)
{
memcpy(dst, src, sizeof(*dst));
}
#endif
/*
* Note that these constants are suitable for indexing the hash_algos array and
* comparing against each other, but are otherwise arbitrary, so they should not
@ -85,6 +102,7 @@ union git_hash_ctx {
typedef union git_hash_ctx git_hash_ctx;
typedef void (*git_hash_init_fn)(git_hash_ctx *ctx);
typedef void (*git_hash_clone_fn)(git_hash_ctx *dst, const git_hash_ctx *src);
typedef void (*git_hash_update_fn)(git_hash_ctx *ctx, const void *in, size_t len);
typedef void (*git_hash_final_fn)(unsigned char *hash, git_hash_ctx *ctx);
@ -110,6 +128,9 @@ struct git_hash_algo {
/* The hash initialization function. */
git_hash_init_fn init_fn;
/* The hash context cloning function. */
git_hash_clone_fn clone_fn;
/* The hash update function. */
git_hash_update_fn update_fn;

18
sha1-file.c
View File

@ -74,6 +74,11 @@ static void git_hash_sha1_init(git_hash_ctx *ctx)
git_SHA1_Init(&ctx->sha1);
}
static void git_hash_sha1_clone(git_hash_ctx *dst, const git_hash_ctx *src)
{
git_SHA1_Clone(&dst->sha1, &src->sha1);
}
static void git_hash_sha1_update(git_hash_ctx *ctx, const void *data, size_t len)
{
git_SHA1_Update(&ctx->sha1, data, len);
@ -90,6 +95,11 @@ static void git_hash_sha256_init(git_hash_ctx *ctx)
git_SHA256_Init(&ctx->sha256);
}
static void git_hash_sha256_clone(git_hash_ctx *dst, const git_hash_ctx *src)
{
git_SHA256_Clone(&dst->sha256, &src->sha256);
}
static void git_hash_sha256_update(git_hash_ctx *ctx, const void *data, size_t len)
{
git_SHA256_Update(&ctx->sha256, data, len);
@ -105,6 +115,11 @@ static void git_hash_unknown_init(git_hash_ctx *ctx)
BUG("trying to init unknown hash");
}
static void git_hash_unknown_clone(git_hash_ctx *dst, const git_hash_ctx *src)
{
BUG("trying to clone unknown hash");
}
static void git_hash_unknown_update(git_hash_ctx *ctx, const void *data, size_t len)
{
BUG("trying to update unknown hash");
@ -123,6 +138,7 @@ const struct git_hash_algo hash_algos[GIT_HASH_NALGOS] = {
0,
0,
git_hash_unknown_init,
git_hash_unknown_clone,
git_hash_unknown_update,
git_hash_unknown_final,
NULL,
@ -136,6 +152,7 @@ const struct git_hash_algo hash_algos[GIT_HASH_NALGOS] = {
GIT_SHA1_HEXSZ,
GIT_SHA1_BLKSZ,
git_hash_sha1_init,
git_hash_sha1_clone,
git_hash_sha1_update,
git_hash_sha1_final,
&empty_tree_oid,
@ -149,6 +166,7 @@ const struct git_hash_algo hash_algos[GIT_HASH_NALGOS] = {
GIT_SHA256_HEXSZ,
GIT_SHA256_BLKSZ,
git_hash_sha256_init,
git_hash_sha256_clone,
git_hash_sha256_update,
git_hash_sha256_final,
&empty_tree_oid_sha256,

6
sha256/gcrypt.h
View File

@ -22,8 +22,14 @@ inline void gcrypt_SHA256_Final(unsigned char *digest, gcrypt_SHA256_CTX *ctx)
memcpy(digest, gcry_md_read(*ctx, GCRY_MD_SHA256), SHA256_DIGEST_SIZE);
}
inline void gcrypt_SHA256_Clone(gcrypt_SHA256_CTX *dst, const gcrypt_SHA256_CTX *src)
{
gcry_md_copy(dst, *src);
}
#define platform_SHA256_CTX gcrypt_SHA256_CTX
#define platform_SHA256_Init gcrypt_SHA256_Init
#define platform_SHA256_Clone gcrypt_SHA256_Clone
#define platform_SHA256_Update gcrypt_SHA256_Update
#define platform_SHA256_Final gcrypt_SHA256_Final