Vastly reduce the number of read(2)s done in tzload.
This costs us about 1000 fewer syscalls, which makes "adb shell strace date"
a lot more readable (which is the reason I've been meaning to fix this for a
long time now), but also actually saves a measurable amount of time.
Longer-term we should try to keep the tzdata mmap(2)ed in like libcore
does.
Change-Id: I1dd9c81968a13d3a6a55ba17f8a7d5c1f38cd103
diff --git a/libc/tzcode/localtime.c b/libc/tzcode/localtime.c
index 202f031..258ea5e 100644
--- a/libc/tzcode/localtime.c
+++ b/libc/tzcode/localtime.c
@@ -2167,26 +2167,40 @@
}
off_t specific_zone_offset = -1;
+ ssize_t index_size = ntohl(header.data_offset) - ntohl(header.index_offset);
+ char* index = malloc(index_size);
+ if (TEMP_FAILURE_RETRY(read(fd, index, index_size)) != index_size) {
+ fprintf(stderr, "%s: could not read index of \"%s\": %s\n",
+ __FUNCTION__, path, (bytes_read == -1) ? strerror(errno) : "short read");
+ free(index);
+ close(fd);
+ return -1;
+ }
static const size_t NAME_LENGTH = 40;
- unsigned char buf[NAME_LENGTH + 3 * sizeof(int32_t)];
+ struct index_entry_t {
+ char buf[NAME_LENGTH];
+ int32_t start;
+ int32_t length;
+ int32_t raw_gmt_offset;
+ };
- size_t id_count = (ntohl(header.data_offset) - ntohl(header.index_offset)) / sizeof(buf);
+ size_t id_count = (ntohl(header.data_offset) - ntohl(header.index_offset)) / sizeof(struct index_entry_t);
+ struct index_entry_t* entry = (struct index_entry_t*) index;
for (size_t i = 0; i < id_count; ++i) {
- if (TEMP_FAILURE_RETRY(read(fd, buf, sizeof(buf))) != (ssize_t) sizeof(buf)) {
- break;
- }
-
char this_id[NAME_LENGTH + 1];
- memcpy(this_id, buf, NAME_LENGTH);
+ memcpy(this_id, entry->buf, NAME_LENGTH);
this_id[NAME_LENGTH] = '\0';
if (strcmp(this_id, olson_id) == 0) {
- specific_zone_offset = to_int(buf + NAME_LENGTH) + ntohl(header.data_offset);
- *data_size = to_int(buf + NAME_LENGTH + sizeof(int32_t));
+ specific_zone_offset = ntohl(entry->start) + ntohl(header.data_offset);
+ *data_size = ntohl(entry->length);
break;
}
+
+ ++entry;
}
+ free(index);
if (specific_zone_offset == -1) {
XLOG(("%s: couldn't find zone \"%s\"\n", __FUNCTION__, olson_id));