Adds file_hash and file_number_from_hash

Allows the user to avoid hash recalculation when looking up the file in multiple MPQ archives. Fixes mbroemme#17
glebm · Nov 3, 2021 · a71dee4 · a71dee4
1 parent f1a3d48
commit a71dee4
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Showing 2 changed files with 21 additions and 10 deletions.
diff --git a/libmpq/mpq.c b/libmpq/mpq.c
@@ -591,26 +591,27 @@ int32_t libmpq__file_imploded(mpq_archive_s *mpq_archive, uint32_t file_number,
 	return LIBMPQ_SUCCESS;
 }
 
-/* this function return filenumber by the given name. */
-int32_t libmpq__file_number(mpq_archive_s *mpq_archive, const char *filename, uint32_t *number) {
-
-	/* some common variables. */
-	uint32_t i, hash1, hash2, hash3, ht_count;
+/* calculates the filename hash. */
+void libmpq__file_hash(const char *filename, uint32_t *hash1, uint32_t *hash2, uint32_t *hash3) {
+	*hash1 = libmpq__hash_string(filename, 0x0);
+	*hash2 = libmpq__hash_string(filename, 0x100);
+	*hash3 = libmpq__hash_string(filename, 0x200);
+}
 
+/* finds the file number with the given filename hash. */
+int32_t libmpq__file_number_from_hash(mpq_archive_s *mpq_archive, uint32_t hash1, uint32_t hash2, uint32_t hash3, uint32_t *number) {
 	/* if the list of file names doesn't include this one, we'll have
 	 * to figure out the file number the "hard" way.
 	 */
-	ht_count = mpq_archive->mpq_header.hash_table_count;
+	uint32_t ht_count = mpq_archive->mpq_header.hash_table_count;
 
-	hash1 = libmpq__hash_string (filename, 0x0) & (ht_count - 1);
-	hash2 = libmpq__hash_string (filename, 0x100);
-	hash3 = libmpq__hash_string (filename, 0x200);
+	hash1 &= (ht_count - 1);
 
 	/* loop through all files in mpq archive.
 	 * hash1 gives us a clue about the starting position of this
 	 * search.
 	 */
-	for (i = hash1; mpq_archive->mpq_hash[i].block_table_index != LIBMPQ_HASH_FREE; i = (i + 1) & (ht_count - 1)) {
+	for (uint32_t i = hash1; mpq_archive->mpq_hash[i].block_table_index != LIBMPQ_HASH_FREE; i = (i + 1) & (ht_count - 1)) {
 
 		/* if the other two hashes match, we found our file number. */
 		if (mpq_archive->mpq_hash[i].hash_a == hash2 &&
@@ -633,6 +634,14 @@ int32_t libmpq__file_number(mpq_archive_s *mpq_archive, const char *filename, ui
 	return LIBMPQ_ERROR_EXIST;
 }
 
+
+/* this function return filenumber by the given name. */
+int32_t libmpq__file_number(mpq_archive_s *mpq_archive, const char *filename, uint32_t *number) {
+	uint32_t hash1, hash2, hash3;
+	libmpq__file_hash(filename, &hash1, &hash2, &hash3);
+	return libmpq__file_number_from_hash(mpq_archive, hash1, hash2, hash3, number);
+}
+
 /* this function read the given file from archive into a buffer. */
 int32_t libmpq__file_read(mpq_archive_s *mpq_archive, uint32_t file_number, uint8_t *out_buf, libmpq__off_t out_size, libmpq__off_t *transferred) {
 

diff --git a/libmpq/mpq.h b/libmpq/mpq.h
@@ -87,6 +87,8 @@ extern LIBMPQ_API int32_t libmpq__file_encrypted(mpq_archive_s *mpq_archive, uin
 extern LIBMPQ_API int32_t libmpq__file_compressed(mpq_archive_s *mpq_archive, uint32_t file_number, uint32_t *compressed);
 extern LIBMPQ_API int32_t libmpq__file_imploded(mpq_archive_s *mpq_archive, uint32_t file_number, uint32_t *imploded);
 extern LIBMPQ_API int32_t libmpq__file_number(mpq_archive_s *mpq_archive, const char *filename, uint32_t *number);
+extern LIBMPQ_API void libmpq__file_hash(const char *filename, uint32_t *hash1, uint32_t *hash2, uint32_t *hash3);
+extern LIBMPQ_API int32_t libmpq__file_number_from_hash(mpq_archive_s *mpq_archive, uint32_t hash1, uint32_t hash2, uint32_t hash3, uint32_t *number);
 extern LIBMPQ_API int32_t libmpq__file_read(mpq_archive_s *mpq_archive, uint32_t file_number, uint8_t *out_buf, libmpq__off_t out_size, libmpq__off_t *transferred);
 extern LIBMPQ_API int32_t libmpq__file_read_with_filename(mpq_archive_s *mpq_archive, uint32_t file_number, const char *filename, uint8_t *out_buf, libmpq__off_t out_size, libmpq__off_t *transferred);