From ac73cedff0db06671e2cab871b84b909b71adbd2 Mon Sep 17 00:00:00 2001 From: "brian m. carlson" Date: Thu, 1 Feb 2018 02:18:38 +0000 Subject: hash: create union for hash context allocation In various parts of our code, we want to allocate a structure representing the internal state of a hash algorithm. The original implementation of the hash algorithm abstraction assumed we would do that using heap allocations, and added a context size element to struct git_hash_algo. However, most of the existing code uses stack allocations and conversion would needlessly complicate various parts of the code. Add a union for the purpose of allocating hash contexts on the stack and a typedef for ease of use. Use this union for defining the init, update, and final functions to avoid casts. Remove the ctxsz element for struct git_hash_algo, which is no longer very useful. This does mean that stack allocations will grow slightly as additional hash functions are added, but this should not be a significant problem, since we don't allocate many hash contexts. The improved usability and benefits from avoiding dynamic allocation outweigh this small downside. Signed-off-by: brian m. carlson Signed-off-by: Junio C Hamano --- hash.h | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-) (limited to 'hash.h') diff --git a/hash.h b/hash.h index 7122dea7b3..eb30f59be3 100644 --- a/hash.h +++ b/hash.h @@ -55,9 +55,15 @@ /* Number of algorithms supported (including unknown). */ #define GIT_HASH_NALGOS (GIT_HASH_SHA1 + 1) -typedef void (*git_hash_init_fn)(void *ctx); -typedef void (*git_hash_update_fn)(void *ctx, const void *in, size_t len); -typedef void (*git_hash_final_fn)(unsigned char *hash, void *ctx); +/* A suitably aligned type for stack allocations of hash contexts. */ +union git_hash_ctx { + git_SHA_CTX sha1; +}; +typedef union git_hash_ctx git_hash_ctx; + +typedef void (*git_hash_init_fn)(git_hash_ctx *ctx); +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); struct git_hash_algo { /* @@ -69,9 +75,6 @@ struct git_hash_algo { /* A four-byte version identifier, used in pack indices. */ uint32_t format_id; - /* The size of a hash context (e.g. git_SHA_CTX). */ - size_t ctxsz; - /* The length of the hash in binary. */ size_t rawsz; -- cgit v1.2.3