From: "brian m. carlson" <sandals@crustytoothpaste.net>
To: git@vger.kernel.org
Cc: "Nguyễn Thái Ngọc Duy" <pclouds@gmail.com>,
"Patryk Obara" <patryk.obara@gmail.com>,
"Jeff King" <peff@peff.net>,
"Eric Sunshine" <sunshine@sunshineco.com>
Subject: [PATCH v2 02/12] hash: create union for hash context allocation
Date: Thu, 1 Feb 2018 02:18:38 +0000 [thread overview]
Message-ID: <20180201021848.533188-3-sandals@crustytoothpaste.net> (raw)
In-Reply-To: <20180201021848.533188-1-sandals@crustytoothpaste.net>
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 <sandals@crustytoothpaste.net>
---
hash.h | 15 +++++++++------
sha1_file.c | 20 +++++++++-----------
2 files changed, 18 insertions(+), 17 deletions(-)
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;
diff --git a/sha1_file.c b/sha1_file.c
index 3da70ac650..ec6ecea170 100644
--- a/sha1_file.c
+++ b/sha1_file.c
@@ -39,32 +39,32 @@ const struct object_id empty_blob_oid = {
EMPTY_BLOB_SHA1_BIN_LITERAL
};
-static void git_hash_sha1_init(void *ctx)
+static void git_hash_sha1_init(git_hash_ctx *ctx)
{
- git_SHA1_Init((git_SHA_CTX *)ctx);
+ git_SHA1_Init(&ctx->sha1);
}
-static void git_hash_sha1_update(void *ctx, const void *data, size_t len)
+static void git_hash_sha1_update(git_hash_ctx *ctx, const void *data, size_t len)
{
- git_SHA1_Update((git_SHA_CTX *)ctx, data, len);
+ git_SHA1_Update(&ctx->sha1, data, len);
}
-static void git_hash_sha1_final(unsigned char *hash, void *ctx)
+static void git_hash_sha1_final(unsigned char *hash, git_hash_ctx *ctx)
{
- git_SHA1_Final(hash, (git_SHA_CTX *)ctx);
+ git_SHA1_Final(hash, &ctx->sha1);
}
-static void git_hash_unknown_init(void *ctx)
+static void git_hash_unknown_init(git_hash_ctx *ctx)
{
die("trying to init unknown hash");
}
-static void git_hash_unknown_update(void *ctx, const void *data, size_t len)
+static void git_hash_unknown_update(git_hash_ctx *ctx, const void *data, size_t len)
{
die("trying to update unknown hash");
}
-static void git_hash_unknown_final(unsigned char *hash, void *ctx)
+static void git_hash_unknown_final(unsigned char *hash, git_hash_ctx *ctx)
{
die("trying to finalize unknown hash");
}
@@ -75,7 +75,6 @@ const struct git_hash_algo hash_algos[GIT_HASH_NALGOS] = {
0x00000000,
0,
0,
- 0,
git_hash_unknown_init,
git_hash_unknown_update,
git_hash_unknown_final,
@@ -86,7 +85,6 @@ const struct git_hash_algo hash_algos[GIT_HASH_NALGOS] = {
"sha-1",
/* "sha1", big-endian */
0x73686131,
- sizeof(git_SHA_CTX),
GIT_SHA1_RAWSZ,
GIT_SHA1_HEXSZ,
git_hash_sha1_init,
next prev parent reply other threads:[~2018-02-01 2:19 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-01 2:18 [PATCH v2 00/12] object_id part 11 (the_hash_algo) brian m. carlson
2018-02-01 2:18 ` [PATCH v2 01/12] hash: move SHA-1 macros to hash.h brian m. carlson
2018-02-02 19:39 ` Junio C Hamano
2018-02-01 2:18 ` brian m. carlson [this message]
2018-02-01 2:18 ` [PATCH v2 03/12] builtin/index-pack: improve hash function abstraction brian m. carlson
2018-02-01 2:18 ` [PATCH v2 04/12] builtin/unpack-objects: switch uses of SHA-1 to the_hash_algo brian m. carlson
2018-02-01 2:18 ` [PATCH v2 05/12] sha1_file: " brian m. carlson
2018-02-01 2:18 ` [PATCH v2 06/12] fast-import: switch various " brian m. carlson
2018-02-01 2:18 ` [PATCH v2 07/12] pack-check: convert various uses of SHA-1 to abstract forms brian m. carlson
2018-02-01 2:18 ` [PATCH v2 08/12] pack-write: switch various SHA-1 values " brian m. carlson
2018-02-01 2:18 ` [PATCH v2 09/12] read-cache: abstract away uses of SHA-1 brian m. carlson
2018-02-01 2:18 ` [PATCH v2 10/12] csum-file: rename sha1file to hashfile brian m. carlson
2018-02-01 2:18 ` [PATCH v2 11/12] csum-file: abstract uses of SHA-1 brian m. carlson
2018-02-01 2:18 ` [PATCH v2 12/12] bulk-checkin: abstract SHA-1 usage brian m. carlson
2018-02-01 22:06 ` [PATCH v2 00/12] object_id part 11 (the_hash_algo) Stefan Beller
2018-02-02 19:46 ` Junio C Hamano
2018-02-06 0:34 ` brian m. carlson
2018-02-06 14:52 ` Junio C Hamano
2018-02-08 2:48 ` [PATCH v2] hash: update obsolete reference to SHA1_HEADER brian m. carlson
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
List information: http://vger.kernel.org/majordomo-info.html
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20180201021848.533188-3-sandals@crustytoothpaste.net \
--to=sandals@crustytoothpaste.net \
--cc=git@vger.kernel.org \
--cc=patryk.obara@gmail.com \
--cc=pclouds@gmail.com \
--cc=peff@peff.net \
--cc=sunshine@sunshineco.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
Code repositories for project(s) associated with this public inbox
https://80x24.org/mirrors/git.git
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).