add non-stub implementation of catgets localization functions

these accept the netbsd/openbsd message catalog file format,
consisting of a sorted list of set headers and a sorted list of
message headers for each set, admitting trivial binary search for
lookups.

the gnu format was not chosen because it's unusably bad. it does not
admit efficient (log time or better) lookups; rather, it requires
linear search or hash table lookups, and the hash function is awful:
it's literally set_id*msg_id.

1 files changed, 33 insertions, 1 deletions

diff --git a/src/locale/catgets.c b/src/locale/catgets.c
index bbee8986..d4a44b35 100644
--- a/src/locale/catgets.c
+++ b/src/locale/catgets.c
@@ -1,6 +1,38 @@
+#define _BSD_SOURCE
 #include <nl_types.h>
+#include <endian.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <errno.h>
+
+#define V(p) be32toh(*(uint32_t *)(p))
+
+int cmp(const void *a, const void *b)
+{
+	uint32_t x = V(a), y = V(b);
+	return x<y ? -1 : x>y ? 1 : 0;
+}
 
 char *catgets (nl_catd catd, int set_id, int msg_id, const char *s)
 {
-	return (char *)s;
+	const char *map = (const char *)catd;
+	uint32_t nsets = V(map+4);
+	const char *sets = map+20;
+	const char *msgs = map+20+V(map+12);
+	const char *strings = map+20+V(map+16);
+	uint32_t set_id_be = htobe32(set_id);
+	uint32_t msg_id_be = htobe32(msg_id);
+	const char *set = bsearch(&set_id_be, sets, nsets, 12, cmp);
+	if (!set) {
+		errno = ENOMSG;
+		return (char *)s;
+	}
+	uint32_t nmsgs = V(set+4);
+	msgs += 12*V(set+8);
+	const char *msg = bsearch(&msg_id_be, msgs, nmsgs, 12, cmp);
+	if (!msg) {
+		errno = ENOMSG;
+		return (char *)s;
+	}
+	return (char *)(strings + V(msg+8));
 }