From: Elijah Newren <newren@xxxxxxxxx> Add strmap as a new struct and associated utility functions, specifically for hashmaps that map strings to some value. The API is taken directly from Peff's proposal at https://lore.kernel.org/git/20180906191203.GA26184@xxxxxxxxxxxxxxxxxxxxx/ Peff only included the header, not the implementation, so it isn't clear what the structure was he was going to use for the hash entries. Instead of having my str_entry struct have three subfields (the hashmap_entry, the string, and the void* value), I made it only have two -- the hashmap_entry and a string_list_item, for two reasons: 1) a strmap is often the data structure we want where string_list has been used in the past. Using the same building block for individual entries in both makes it easier to adopt and reuse parts of the string_list API in strmap. 2) In some cases, after doing lots of other work, I want to be able to iterate over the items in my strmap in sorted order. hashmap obviously doesn't support that, but I wanted to be able to export the strmap to a string_list easily and then use its functions. (Note: I do not need the data structure to both be sorted and have efficient lookup at all times. If I did, I might use a B-tree instead, as suggested by brian in response to Peff in the thread noted above. In my case, most strmaps will never need sorting, but in one special case at the very end of a bunch of other work I want to iterate over the items in sorted order without doing any more lookups afterward.) Also, I removed the STRMAP_INIT macro, since it cannot be used to correctly initialize a strmap; the underlying hashmap needs a call to hashmap_init() to allocate the hash table first. Signed-off-by: Elijah Newren <newren@xxxxxxxxx> --- Makefile | 1 + strmap.c | 81 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ strmap.h | 47 ++++++++++++++++++++++++++++++++ 3 files changed, 129 insertions(+) create mode 100644 strmap.c create mode 100644 strmap.h diff --git a/Makefile b/Makefile index 65f8cfb236..0da15a9ee5 100644 --- a/Makefile +++ b/Makefile @@ -988,6 +988,7 @@ LIB_OBJS += strbuf.o LIB_OBJS += strvec.o LIB_OBJS += streaming.o LIB_OBJS += string-list.o +LIB_OBJS += strmap.o LIB_OBJS += sub-process.o LIB_OBJS += submodule-config.o LIB_OBJS += submodule.o diff --git a/strmap.c b/strmap.c new file mode 100644 index 0000000000..1c9fdb3b1e --- /dev/null +++ b/strmap.c @@ -0,0 +1,81 @@ +#include "git-compat-util.h" +#include "strmap.h" + +static int cmp_str_entry(const void *hashmap_cmp_fn_data, + const struct hashmap_entry *entry1, + const struct hashmap_entry *entry2, + const void *keydata) +{ + const struct str_entry *e1, *e2; + + e1 = container_of(entry1, const struct str_entry, ent); + e2 = container_of(entry2, const struct str_entry, ent); + return strcmp(e1->item.string, e2->item.string); +} + +static struct str_entry *find_str_entry(struct strmap *map, + const char *str) +{ + struct str_entry entry; + hashmap_entry_init(&entry.ent, strhash(str)); + entry.item.string = (char *)str; + return hashmap_get_entry(&map->map, &entry, ent, NULL); +} + +void strmap_init(struct strmap *map) +{ + hashmap_init(&map->map, cmp_str_entry, NULL, 0); +} + +void strmap_clear(struct strmap *map, int free_util) +{ + struct hashmap_iter iter; + struct str_entry *e; + + if (!map) + return; + + hashmap_for_each_entry(&map->map, &iter, e, ent /* member name */) { + free(e->item.string); + if (free_util) + free(e->item.util); + } + hashmap_free_entries(&map->map, struct str_entry, ent); + strmap_init(map); +} + +/* + * Insert "str" into the map, pointing to "data". A copy of "str" is made, so + * it does not need to persist after the this function is called. + * + * If an entry for "str" already exists, its data pointer is overwritten, and + * the original data pointer returned. Otherwise, returns NULL. + */ +void *strmap_put(struct strmap *map, const char *str, void *data) +{ + struct str_entry *entry = find_str_entry(map, str); + void *old = NULL; + + if (entry) { + old = entry->item.util; + entry->item.util = data; + } else { + entry = xmalloc(sizeof(*entry)); + hashmap_entry_init(&entry->ent, strhash(str)); + entry->item.string = strdup(str); + entry->item.util = data; + hashmap_add(&map->map, &entry->ent); + } + return old; +} + +void *strmap_get(struct strmap *map, const char *str) +{ + struct str_entry *entry = find_str_entry(map, str); + return entry ? entry->item.util : NULL; +} + +int strmap_contains(struct strmap *map, const char *str) +{ + return find_str_entry(map, str) != NULL; +} diff --git a/strmap.h b/strmap.h new file mode 100644 index 0000000000..eb5807f6fa --- /dev/null +++ b/strmap.h @@ -0,0 +1,47 @@ +#ifndef STRMAP_H +#define STRMAP_H + +#include "hashmap.h" +#include "string-list.h" + +struct strmap { + struct hashmap map; +}; + +struct str_entry { + struct hashmap_entry ent; + struct string_list_item item; +}; + +/* + * Initialize an empty strmap + */ +void strmap_init(struct strmap *map); + +/* + * Remove all entries from the map, releasing any allocated resources. + */ +void strmap_clear(struct strmap *map, int free_values); + +/* + * Insert "str" into the map, pointing to "data". A copy of "str" is made, so + * it does not need to persist after the this function is called. + * + * If an entry for "str" already exists, its data pointer is overwritten, and + * the original data pointer returned. Otherwise, returns NULL. + */ +void *strmap_put(struct strmap *map, const char *str, void *data); + +/* + * Return the data pointer mapped by "str", or NULL if the entry does not + * exist. + */ +void *strmap_get(struct strmap *map, const char *str); + +/* + * Return non-zero iff "str" is present in the map. This differs from + * strmap_get() in that it can distinguish entries with a NULL data pointer. + */ +int strmap_contains(struct strmap *map, const char *str); + +#endif /* STRMAP_H */ -- gitgitgadget
