strmap: enable allocations to come from a mem_pool

For heavy users of strmaps, allowing the keys and entries to be
allocated from a memory pool can provide significant overhead savings.
Add an option to strmap_init_with_options() to specify a memory pool.

Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

strmap.c

@@ -1,5 +1,6 @@
 #include "git-compat-util.h"
 #include "strmap.h"
+#include "mem-pool.h"
 
 int cmp_strmap_entry(const void *hashmap_cmp_fn_data,
 		     const struct hashmap_entry *entry1,
@@ -24,13 +25,15 @@ static struct strmap_entry *find_strmap_entry(struct strmap *map,
 
 void strmap_init(struct strmap *map)
 {
-	strmap_init_with_options(map, 1);
+	strmap_init_with_options(map, NULL, 1);
 }
 
 void strmap_init_with_options(struct strmap *map,
+			      struct mem_pool *pool,
 			      int strdup_strings)
 {
 	hashmap_init(&map->map, cmp_strmap_entry, NULL, 0);
+	map->pool = pool;
 	map->strdup_strings = strdup_strings;
 }
 
@@ -42,6 +45,10 @@ static void strmap_free_entries_(struct strmap *map, int free_values)
 	if (!map)
 		return;
 
+	if (!free_values && map->pool)
+		/* Memory other than util is owned by and freed with the pool */
+		return;
+
 	/*
 	 * We need to iterate over the hashmap entries and free
 	 * e->key and e->value ourselves; hashmap has no API to
@@ -52,9 +59,11 @@ static void strmap_free_entries_(struct strmap *map, int free_values)
 	hashmap_for_each_entry(&map->map, &iter, e, ent) {
 		if (free_values)
 			free(e->value);
-		if (map->strdup_strings)
+		if (!map->pool) {
-			free((char*)e->key);
+			if (map->strdup_strings)
-		free(e);
+				free((char*)e->key);
+			free(e);
+		}
 	}
 }
 
@@ -77,11 +86,13 @@ static struct strmap_entry *create_entry(struct strmap *map,
 	struct strmap_entry *entry;
 	const char *key = str;
 
-	entry = xmalloc(sizeof(*entry));
+	entry = map->pool ? mem_pool_alloc(map->pool, sizeof(*entry))
+			  : xmalloc(sizeof(*entry));
 	hashmap_entry_init(&entry->ent, strhash(str));
 
 	if (map->strdup_strings)
-		key = xstrdup(str);
+		key = map->pool ? mem_pool_strdup(map->pool, str)
+				: xstrdup(str);
 	entry->key = key;
 	entry->value = data;
 	return entry;
@@ -128,9 +139,11 @@ void strmap_remove(struct strmap *map, const char *str, int free_value)
 		return;
 	if (free_value)
 		free(ret->value);
-	if (map->strdup_strings)
+	if (!map->pool) {
-		free((char*)ret->key);
+		if (map->strdup_strings)
-	free(ret);
+			free((char*)ret->key);
+		free(ret);
+	}
 }
 
 void strintmap_incr(struct strintmap *map, const char *str, intptr_t amt)

strmap.h

@@ -3,8 +3,10 @@
 
 #include "hashmap.h"
 
+struct mem_pool;
 struct strmap {
 	struct hashmap map;
+	struct mem_pool *pool;
 	unsigned int strdup_strings:1;
 };
 
@@ -37,9 +39,10 @@ void strmap_init(struct strmap *map);
 
 /*
  * Same as strmap_init, but for those who want to control the memory management
- * carefully instead of using the default of strdup_strings=1.
+ * carefully instead of using the default of strdup_strings=1 and pool=NULL.
  */
 void strmap_init_with_options(struct strmap *map,
+			      struct mem_pool *pool,
 			      int strdup_strings);
 
 /*
@@ -137,9 +140,10 @@ static inline void strintmap_init(struct strintmap *map, int default_value)
 
 static inline void strintmap_init_with_options(struct strintmap *map,
 					       int default_value,
+					       struct mem_pool *pool,
 					       int strdup_strings)
 {
-	strmap_init_with_options(&map->map, strdup_strings);
+	strmap_init_with_options(&map->map, pool, strdup_strings);
 	map->default_value = default_value;
 }
 
@@ -221,9 +225,10 @@ static inline void strset_init(struct strset *set)
 }
 
 static inline void strset_init_with_options(struct strset *set,
+					    struct mem_pool *pool,
 					    int strdup_strings)
 {
-	strmap_init_with_options(&set->map, strdup_strings);
+	strmap_init_with_options(&set->map, pool, strdup_strings);
 }
 
 static inline void strset_clear(struct strset *set)