Implement find_unique_prefixes() by sorting the prefix items
lexicographically and then looking for unique prefixes in adjacent
pairs. It's definitely shorter than the current hashmap-based
implementation (101 vs 149 lines), subjectively easier to follow, and
hopefully less buggy (some of the new elements in the test trigger
failure with the hashmap).
TODO: deal multi-byte caracter sequences, make the test tool more
developer-friendly
---
Makefile | 2 +-
add-interactive.c | 2 +-
prefix-map.c | 109 -------------------------------------
prefix-map.h | 40 --------------
t/helper/test-prefix-map.c | 31 +++++++----
unique-prefix.c | 73 +++++++++++++++++++++++++
unique-prefix.h | 28 ++++++++++
7 files changed, 124 insertions(+), 161 deletions(-)
delete mode 100644 prefix-map.c
delete mode 100644 prefix-map.h
create mode 100644 unique-prefix.c
create mode 100644 unique-prefix.h
diff --git a/Makefile b/Makefile
index 545a0e8743..6773041f0d 100644
--- a/Makefile
+++ b/Makefile
@@ -944,7 +944,6 @@ LIB_OBJS += patch-ids.o
LIB_OBJS += path.o
LIB_OBJS += pathspec.o
LIB_OBJS += pkt-line.o
-LIB_OBJS += prefix-map.o
LIB_OBJS += preload-index.o
LIB_OBJS += pretty.o
LIB_OBJS += prio-queue.o
@@ -1013,6 +1012,7 @@ LIB_OBJS += transport-helper.o
LIB_OBJS += tree-diff.o
LIB_OBJS += tree.o
LIB_OBJS += tree-walk.o
+LIB_OBJS += unique-prefix.o
LIB_OBJS += unpack-trees.o
LIB_OBJS += upload-pack.o
LIB_OBJS += url.o
diff --git a/add-interactive.c b/add-interactive.c
index c431c72e3f..cf22749b81 100644
--- a/add-interactive.c
+++ b/add-interactive.c
@@ -5,7 +5,7 @@
#include "diffcore.h"
#include "revision.h"
#include "refs.h"
-#include "prefix-map.h"
+#include "unique-prefix.h"
struct add_i_state {
struct repository *r;
diff --git a/prefix-map.c b/prefix-map.c
deleted file mode 100644
index 747ddb4ebc..0000000000
--- a/prefix-map.c
+++ /dev/null
@@ -1,109 +0,0 @@
-#include "cache.h"
-#include "prefix-map.h"
-
-static int map_cmp(const void *unused_cmp_data,
- const void *entry,
- const void *entry_or_key,
- const void *unused_keydata)
-{
- const struct prefix_map_entry *a = entry;
- const struct prefix_map_entry *b = entry_or_key;
-
- return a->prefix_length != b->prefix_length ||
- strncmp(a->name, b->name, a->prefix_length);
-}
-
-static void add_prefix_entry(struct hashmap *map, const char *name,
- size_t prefix_length, struct prefix_item *item)
-{
- struct prefix_map_entry *result = xmalloc(sizeof(*result));
- result->name = name;
- result->prefix_length = prefix_length;
- result->item = item;
- hashmap_entry_init(result, memhash(name, prefix_length));
- hashmap_add(map, result);
-}
-
-static void init_prefix_map(struct prefix_map *prefix_map,
- int min_prefix_length, int max_prefix_length)
-{
- hashmap_init(&prefix_map->map, map_cmp, NULL, 0);
- prefix_map->min_length = min_prefix_length;
- prefix_map->max_length = max_prefix_length;
-}
-
-static void add_prefix_item(struct prefix_map *prefix_map,
- struct prefix_item *item)
-{
- struct prefix_map_entry e = { { NULL } }, *e2;
- int j;
-
- e.item = item;
- e.name = item->name;
-
- for (j = prefix_map->min_length;
- j <= prefix_map->max_length && e.name[j]; j++) {
- /* Avoid breaking UTF-8 multi-byte sequences */
- if (!isascii(e.name[j]))
- break;
-
- e.prefix_length = j;
- hashmap_entry_init(&e, memhash(e.name, j));
- e2 = hashmap_get(&prefix_map->map, &e, NULL);
- if (!e2) {
- /* prefix is unique at this stage */
- item->prefix_length = j;
- add_prefix_entry(&prefix_map->map, e.name, j, item);
- break;
- }
-
- if (!e2->item)
- continue; /* non-unique prefix */
-
- if (j != e2->item->prefix_length || memcmp(e.name, e2->name, j))
- BUG("unexpected prefix length: %d != %d (%s != %s)",
- j, (int)e2->item->prefix_length, e.name, e2->name);
-
- /* skip common prefix */
- for (; j < prefix_map->max_length && e.name[j]; j++) {
- if (e.item->name[j] != e2->item->name[j])
- break;
- add_prefix_entry(&prefix_map->map, e.name, j + 1,
- NULL);
- }
-
- /* e2 no longer refers to a unique prefix */
- if (j < prefix_map->max_length && e2->name[j]) {
- /* found a new unique prefix for e2's item */
- e2->item->prefix_length = j + 1;
- add_prefix_entry(&prefix_map->map, e2->name, j + 1,
- e2->item);
- }
- else
- e2->item->prefix_length = 0;
- e2->item = NULL;
-
- if (j < prefix_map->max_length && e.name[j]) {
- /* found a unique prefix for the item */
- e.item->prefix_length = j + 1;
- add_prefix_entry(&prefix_map->map, e.name, j + 1,
- e.item);
- } else
- /* item has no (short enough) unique prefix */
- e.item->prefix_length = 0;
-
- break;
- }
-}
-
-void find_unique_prefixes(struct prefix_item **list, size_t nr,
- int min_length, int max_length)
-{
- int i;
- struct prefix_map prefix_map;
-
- init_prefix_map(&prefix_map, min_length, max_length);
- for (i = 0; i < nr; i++)
- add_prefix_item(&prefix_map, list[i]);
- hashmap_free(&prefix_map.map, 1);
-}
diff --git a/prefix-map.h b/prefix-map.h
deleted file mode 100644
index ce3b8a4a32..0000000000
--- a/prefix-map.h
+++ /dev/null
@@ -1,40 +0,0 @@
-#ifndef PREFIX_MAP_H
-#define PREFIX_MAP_H
-
-#include "hashmap.h"
-
-struct prefix_item {
- const char *name;
- size_t prefix_length;
-};
-
-struct prefix_map_entry {
- struct hashmap_entry e;
- const char *name;
- size_t prefix_length;
- /* if item is NULL, the prefix is not unique */
- struct prefix_item *item;
-};
-
-struct prefix_map {
- struct hashmap map;
- int min_length, max_length;
-};
-
-/*
- * Find unique prefixes in a given list of strings.
- *
- * Typically, the `struct prefix_item` information will be but a field in the
- * actual item struct; For this reason, the `list` parameter is specified as a
- * list of pointers to the items.
- *
- * The `min_length`/`max_length` parameters define what length the unique
- * prefixes should have.
- *
- * If no unique prefix could be found for a given item, its `prefix_length`
- * will be set to 0.
- */
-void find_unique_prefixes(struct prefix_item **list, size_t nr,
- int min_length, int max_length);
-
-#endif
diff --git a/t/helper/test-prefix-map.c b/t/helper/test-prefix-map.c
index 3f1c90eaf0..d472ff5dc6 100644
--- a/t/helper/test-prefix-map.c
+++ b/t/helper/test-prefix-map.c
@@ -1,6 +1,5 @@
#include "test-tool.h"
-#include "cache.h"
-#include "prefix-map.h"
+#include "unique-prefix.h"
static size_t test_count, failed_count;
@@ -24,25 +23,32 @@ static void check(int succeeded, const char *file, size_t line_no,
#define EXPECT_SIZE_T_EQUALS(expect, actual, hint) \
check(expect == actual, __FILE__, __LINE__, \
- "size_t's do not match: %" \
- PRIdMAX " != %" PRIdMAX " (%s) (%s)", \
+ "size_t's do not match: expected: %" \
+ PRIdMAX " got: %" PRIdMAX " (%s) (%s)", \
(intmax_t)expect, (intmax_t)actual, #actual, hint)
int cmd__prefix_map(int argc, const char **argv)
{
-#define NR 5
- struct prefix_item items[NR] = {
+ size_t i;
+ struct prefix_item items[] = {
{ "unique" },
{ "hell" },
{ "hello" },
{ "wok" },
{ "world" },
+ { "a" },
+ { "" },
+ { "pq" },
+ { "pq" },
+ { "pqr" },
};
- struct prefix_item *list[NR] = {
- items, items + 1, items + 2, items + 3, items + 4
- };
+ struct prefix_item *list[ARRAY_SIZE(items)];
+ for (i = 0; i < ARRAY_SIZE(items); i++) {
+ list[i] = &items[i];
+ list[i]->prefix_length = 12345; /* dummy */
+ }
- find_unique_prefixes(list, NR, 1, 3);
+ find_unique_prefixes(list, ARRAY_SIZE(list), 1, 3);
#define EXPECT_PREFIX_LENGTH_EQUALS(expect, index) \
EXPECT_SIZE_T_EQUALS(expect, list[index]->prefix_length, \
@@ -53,6 +59,11 @@ int cmd__prefix_map(int argc, const char **argv)
EXPECT_PREFIX_LENGTH_EQUALS(0, 2);
EXPECT_PREFIX_LENGTH_EQUALS(3, 3);
EXPECT_PREFIX_LENGTH_EQUALS(3, 4);
+ EXPECT_PREFIX_LENGTH_EQUALS(1, 5);
+ EXPECT_PREFIX_LENGTH_EQUALS(0, 6);
+ EXPECT_PREFIX_LENGTH_EQUALS(0, 7);
+ EXPECT_PREFIX_LENGTH_EQUALS(0, 8);
+ EXPECT_PREFIX_LENGTH_EQUALS(3, 9);
return !!failed_count;
}
diff --git a/unique-prefix.c b/unique-prefix.c
new file mode 100644
index 0000000000..327e8fa32c
--- /dev/null
+++ b/unique-prefix.c
@@ -0,0 +1,73 @@
+#include "git-compat-util.h"
+#include "unique-prefix.h"
+
+static int prefix_item_ptr_cmp(const void *item1, const void *item2)
+{
+ const struct prefix_item *pi1 = *((struct prefix_item**) item1);
+ const struct prefix_item *pi2 = *((struct prefix_item**) item2);
+ return strcmp(pi1->name, pi2->name);
+}
+
+static int str_is_shorter_than(const char *s, size_t len)
+{
+ for (; *s && len; s++, len--);
+ return !!len;
+}
+
+static size_t str_common_prefix_len(const char *s1, const char *s2, size_t limit)
+{
+ size_t i;
+ for (i = 0; i < limit; i++)
+ if (s1[i] != s2[i] || s1[i] == '\0')
+ return i;
+ return limit + 1;
+}
+
+void find_unique_prefixes(struct prefix_item **items, size_t nr,
+ int min_length, int max_length)
+{
+ size_t i;
+ struct prefix_item **sorted_items;
+
+ ALLOC_ARRAY(sorted_items, nr);
+ COPY_ARRAY(sorted_items, items, nr);
+ QSORT(sorted_items, nr, prefix_item_ptr_cmp);
+
+ if (str_is_shorter_than(sorted_items[0]->name, min_length))
+ sorted_items[0]->prefix_length = 0;
+ else
+ sorted_items[0]->prefix_length = min_length;
+ for (i = 1; i < nr; i++) {
+ size_t common_len = str_common_prefix_len(
+ sorted_items[i - 1]->name, sorted_items[i]->name,
+ max_length);
+
+ if (!sorted_items[i - 1]->prefix_length)
+ /*
+ * The previous iteration already determined that
+ * it doesn't have a unique prefix.
+ */
+ ;
+ else if (max_length < common_len)
+ sorted_items[i - 1]->prefix_length = 0;
+ else if (sorted_items[i - 1]->name[common_len] == '\0')
+ /* Either prefix of or equal to the next string. */
+ sorted_items[i - 1]->prefix_length = 0;
+ else if (sorted_items[i - 1]->prefix_length <= common_len)
+ sorted_items[i - 1]->prefix_length = common_len + 1;
+
+ if (max_length < common_len)
+ sorted_items[i]->prefix_length = 0;
+ else if (sorted_items[i]->name[common_len] == '\0')
+ /* the two strings are the same */
+ sorted_items[i]->prefix_length = 0;
+ else if (min_length <= common_len)
+ sorted_items[i]->prefix_length = common_len + 1;
+ else if (str_is_shorter_than(sorted_items[i]->name, min_length))
+ sorted_items[i]->prefix_length = 0;
+ else
+ sorted_items[i]->prefix_length = min_length;
+ }
+
+ free(sorted_items);
+}
diff --git a/unique-prefix.h b/unique-prefix.h
new file mode 100644
index 0000000000..cbddc29a9a
--- /dev/null
+++ b/unique-prefix.h
@@ -0,0 +1,28 @@
+#ifndef UNIQUE_PREFIX_H
+#define UNIQUE_PREFIX_H
+
+struct prefix_item {
+ const char *name;
+ size_t prefix_length;
+};
+
+/*
+ * Find unique prefixes in a given array of strings.
+ * Given a list of names, find unique prefixes (i.e. the first <n> characters
+ * that uniquely identify the names) and store the lengths of the unique
+ * prefixes in the 'prefix_length' field of the elements of the given array.
+ *
+ * Typically, the `struct prefix_item` information will be a field in the
+ * actual item struct; For this reason, the `items` parameter is specified
+ * as an array of pointers to the items.
+ *
+ * The `min_length`/`max_length` parameters define what length the unique
+ * prefixes should have.
+ *
+ * If no unique prefix could be found for a given item, its `prefix_length`
+ * will be set to 0.
+ */
+void find_unique_prefixes(struct prefix_item **items, size_t nr,
+ int min_length, int max_length);
+
+#endif
--
2.23.0.331.g4e51dcdf11
