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c6746a4f41
Let's not walk off the end of the array. Also, avoid an early `malloc()` in `add_prefix_entry()` (avoiding reuse of the same data structure for lookup as for adding a new item), and strengthen the condition for the bug condition. Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
110 lines
2.9 KiB
C
110 lines
2.9 KiB
C
#include "cache.h"
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#include "prefix-map.h"
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static int map_cmp(const void *unused_cmp_data,
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const void *entry,
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const void *entry_or_key,
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const void *unused_keydata)
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{
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const struct prefix_map_entry *a = entry;
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const struct prefix_map_entry *b = entry_or_key;
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return a->prefix_length != b->prefix_length ||
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strncmp(a->name, b->name, a->prefix_length);
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}
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static void add_prefix_entry(struct hashmap *map, const char *name,
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size_t prefix_length, struct prefix_item *item)
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{
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struct prefix_map_entry *result = xmalloc(sizeof(*result));
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result->name = name;
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result->prefix_length = prefix_length;
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result->item = item;
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hashmap_entry_init(result, memhash(name, prefix_length));
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hashmap_add(map, result);
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}
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static void init_prefix_map(struct prefix_map *prefix_map,
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int min_prefix_length, int max_prefix_length)
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{
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hashmap_init(&prefix_map->map, map_cmp, NULL, 0);
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prefix_map->min_length = min_prefix_length;
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prefix_map->max_length = max_prefix_length;
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}
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static void add_prefix_item(struct prefix_map *prefix_map,
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struct prefix_item *item)
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{
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struct prefix_map_entry e = { { NULL } }, *e2;
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int j;
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e.item = item;
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e.name = item->name;
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for (j = prefix_map->min_length;
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j <= prefix_map->max_length && e.name[j]; j++) {
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/* Avoid breaking UTF-8 multi-byte sequences */
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if (!isascii(e.name[j]))
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break;
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e.prefix_length = j;
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hashmap_entry_init(&e, memhash(e.name, j));
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e2 = hashmap_get(&prefix_map->map, &e, NULL);
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if (!e2) {
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/* prefix is unique at this stage */
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item->prefix_length = j;
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add_prefix_entry(&prefix_map->map, e.name, j, item);
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break;
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}
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if (!e2->item)
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continue; /* non-unique prefix */
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if (j != e2->item->prefix_length || memcmp(e.name, e2->name, j))
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BUG("unexpected prefix length: %d != %d (%s != %s)",
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j, (int)e2->item->prefix_length, e.name, e2->name);
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/* skip common prefix */
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for (; j < prefix_map->max_length && e.name[j]; j++) {
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if (e.item->name[j] != e2->item->name[j])
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break;
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add_prefix_entry(&prefix_map->map, e.name, j + 1,
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NULL);
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}
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/* e2 no longer refers to a unique prefix */
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if (j < prefix_map->max_length && e2->name[j]) {
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/* found a new unique prefix for e2's item */
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e2->item->prefix_length = j + 1;
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add_prefix_entry(&prefix_map->map, e2->name, j + 1,
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e2->item);
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}
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else
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e2->item->prefix_length = 0;
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e2->item = NULL;
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if (j < prefix_map->max_length && e.name[j]) {
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/* found a unique prefix for the item */
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e.item->prefix_length = j + 1;
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add_prefix_entry(&prefix_map->map, e.name, j + 1,
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e.item);
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} else
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/* item has no (short enough) unique prefix */
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e.item->prefix_length = 0;
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break;
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}
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}
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void find_unique_prefixes(struct prefix_item **list, size_t nr,
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int min_length, int max_length)
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{
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int i;
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struct prefix_map prefix_map;
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init_prefix_map(&prefix_map, min_length, max_length);
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for (i = 0; i < nr; i++)
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add_prefix_item(&prefix_map, list[i]);
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hashmap_free(&prefix_map.map, 1);
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}
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