From 8380dcd700e80cd22745bcffb3625f90f943950c Mon Sep 17 00:00:00 2001
From: Jeff King <peff@peff.net>
Date: Thu, 28 Jan 2021 01:20:23 -0500
Subject: [PATCH] oid_pos(): access table through const pointers

When we are looking up an oid in an array, we obviously don't need to
write to the array. Let's mark it as const in the function interfaces,
as well as in the local variables we use to derference the void pointer
(note a few cases use pointers-to-pointers, so we mark everything
const).

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 builtin/name-rev.c  | 4 ++--
 commit-graph.c      | 4 ++--
 commit.c            | 4 ++--
 hash-lookup.c       | 2 +-
 hash-lookup.h       | 4 ++--
 oid-array.c         | 4 ++--
 pack-bitmap-write.c | 4 ++--
 7 files changed, 13 insertions(+), 13 deletions(-)

diff --git a/builtin/name-rev.c b/builtin/name-rev.c
index 27138fdce47..b221d300147 100644
--- a/builtin/name-rev.c
+++ b/builtin/name-rev.c
@@ -390,9 +390,9 @@ static void name_tips(void)
 	}
 }
 
-static const struct object_id *nth_tip_table_ent(size_t ix, void *table_)
+static const struct object_id *nth_tip_table_ent(size_t ix, const void *table_)
 {
-	struct tip_table_entry *table = table_;
+	const struct tip_table_entry *table = table_;
 	return &table[ix].oid;
 }
 
diff --git a/commit-graph.c b/commit-graph.c
index 248f1efb73e..b09fce5f573 100644
--- a/commit-graph.c
+++ b/commit-graph.c
@@ -1012,9 +1012,9 @@ static int write_graph_chunk_oids(struct hashfile *f,
 	return 0;
 }
 
-static const struct object_id *commit_to_oid(size_t index, void *table)
+static const struct object_id *commit_to_oid(size_t index, const void *table)
 {
-	struct commit **commits = table;
+	const struct commit * const *commits = table;
 	return &commits[index]->object.oid;
 }
 
diff --git a/commit.c b/commit.c
index 39eab5b36bc..fd2831dad32 100644
--- a/commit.c
+++ b/commit.c
@@ -105,9 +105,9 @@ static timestamp_t parse_commit_date(const char *buf, const char *tail)
 	return parse_timestamp(dateptr, NULL, 10);
 }
 
-static const struct object_id *commit_graft_oid_access(size_t index, void *table)
+static const struct object_id *commit_graft_oid_access(size_t index, const void *table)
 {
-	struct commit_graft **commit_graft_table = table;
+	const struct commit_graft * const *commit_graft_table = table;
 	return &commit_graft_table[index]->oid;
 }
 
diff --git a/hash-lookup.c b/hash-lookup.c
index d15bb345749..b98ed5e11e8 100644
--- a/hash-lookup.c
+++ b/hash-lookup.c
@@ -50,7 +50,7 @@ static uint32_t take2(const struct object_id *oid, size_t ofs)
  * The oid of element i (between 0 and nr - 1) should be returned
  * by "fn(i, table)".
  */
-int oid_pos(const struct object_id *oid, void *table, size_t nr,
+int oid_pos(const struct object_id *oid, const void *table, size_t nr,
 	    oid_access_fn fn)
 {
 	size_t hi = nr;
diff --git a/hash-lookup.h b/hash-lookup.h
index 7b3ecad1f03..dbd71ebaf73 100644
--- a/hash-lookup.h
+++ b/hash-lookup.h
@@ -1,10 +1,10 @@
 #ifndef HASH_LOOKUP_H
 #define HASH_LOOKUP_H
 
-typedef const struct object_id *oid_access_fn(size_t index, void *table);
+typedef const struct object_id *oid_access_fn(size_t index, const void *table);
 
 int oid_pos(const struct object_id *oid,
-	    void *table,
+	    const void *table,
 	    size_t nr,
 	    oid_access_fn fn);
 
diff --git a/oid-array.c b/oid-array.c
index a19235afbf8..73ba76e9e9a 100644
--- a/oid-array.c
+++ b/oid-array.c
@@ -22,9 +22,9 @@ void oid_array_sort(struct oid_array *array)
 	array->sorted = 1;
 }
 
-static const struct object_id *oid_access(size_t index, void *table)
+static const struct object_id *oid_access(size_t index, const void *table)
 {
-	struct object_id *array = table;
+	const struct object_id *array = table;
 	return &array[index];
 }
 
diff --git a/pack-bitmap-write.c b/pack-bitmap-write.c
index f21259dfc82..88d9e696a54 100644
--- a/pack-bitmap-write.c
+++ b/pack-bitmap-write.c
@@ -610,9 +610,9 @@ static inline void dump_bitmap(struct hashfile *f, struct ewah_bitmap *bitmap)
 		die("Failed to write bitmap index");
 }
 
-static const struct object_id *oid_access(size_t pos, void *table)
+static const struct object_id *oid_access(size_t pos, const void *table)
 {
-	struct pack_idx_entry **index = table;
+	const struct pack_idx_entry * const *index = table;
 	return &index[pos]->oid;
 }