diff --git a/src/locale/catclose.c b/src/locale/catclose.c
index 02cd3e5c9c7a76a553e950c475e67b2c1e125259..54e24dd2163bc85a250b2efc7a36fa0f0aa446e8 100644
--- a/src/locale/catclose.c
+++ b/src/locale/catclose.c
@@ -1,6 +1,14 @@
+#define _BSD_SOURCE
 #include <nl_types.h>
+#include <stdint.h>
+#include <endian.h>
+#include <sys/mman.h>
+
+#define V(p) be32toh(*(uint32_t *)(p))
 
 int catclose (nl_catd catd)
 {
+	char *map = (char *)catd;
+	munmap(map, V(map+8)+20);
 	return 0;
 }
diff --git a/src/locale/catgets.c b/src/locale/catgets.c
index bbee8986fc581ebce93494b2dad7539c37083628..d4a44b3555b0e6207351e6c9e5546bf6830c12ce 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));
 }
diff --git a/src/locale/catopen.c b/src/locale/catopen.c
index 3fbc77178fb24e7c9661f383dccdd9b762387957..97f2446d37f983d085c9965dd700e91eabe55969 100644
--- a/src/locale/catopen.c
+++ b/src/locale/catopen.c
@@ -1,8 +1,79 @@
+#define _BSD_SOURCE
 #include <nl_types.h>
+#include <string.h>
+#include <stdint.h>
+#include <endian.h>
 #include <errno.h>
+#include <langinfo.h>
+#include <locale.h>
+#include <sys/mman.h>
+#include "libc.h"
 
-nl_catd catopen (const char *name, int oflag)
+#define V(p) be32toh(*(uint32_t *)(p))
+
+static nl_catd do_catopen(const char *name)
+{
+	size_t size;
+	const unsigned char *map = __map_file(name, &size);
+	/* Size recorded in the file must match file size; otherwise
+	 * the information needed to unmap the file will be lost. */
+	if (!map || V(map) != 0xff88ff89 || 20+V(map+8) != size) {
+		if(map) munmap((void *)map, size);
+		errno = ENOENT;
+		return (nl_catd)-1;
+	}
+	return (nl_catd)map;
+}
+
+nl_catd catopen(const char *name, int oflag)
 {
-	errno = EOPNOTSUPP;
+	nl_catd catd;
+
+	if (strchr(name, '/')) return do_catopen(name);
+
+	char buf[PATH_MAX];
+	size_t i;
+	const char *path, *lang, *p, *z;
+	if (libc.secure || !(path = getenv("NLSPATH"))) {
+		errno = ENOENT;
+		return (nl_catd)-1;
+	}
+	lang = oflag ? nl_langinfo(_NL_LOCALE_NAME(LC_MESSAGES)) : getenv("LANG");
+	if (!lang) lang = "";
+	for (p=path; *p; p=z) {
+		i = 0;
+		z = __strchrnul(p, ':');
+		for (; p<z; p++) {
+			const char *v;
+			size_t l;
+			if (*p!='%') v=p, l=1;
+			else switch (*++p) {
+			case 'N': v=name; l=strlen(v); break;
+			case 'L': v=lang; l=strlen(v); break;
+			case 'l': v=lang; l=strcspn(v,"_.@"); break;
+			case 't':
+				v=__strchrnul(lang,'_');
+				if (*v) v++;
+				l=strcspn(v,".@");
+				break;
+			case 'c': v="UTF-8"; l=5; break;
+			case '%': v="%"; l=1; break;
+			default: v=0;
+			}
+			if (!v || l >= sizeof buf - i) {
+				break;
+			}
+			memcpy(buf+i, v, l);
+			i += l;
+		}
+		if (!*z && (p<z || !i)) break;
+		if (p<z) continue;
+		if (*z) z++;
+		buf[i] = 0;
+		/* Leading : or :: in NLSPATH is same as %N */
+		catd = do_catopen(i ? buf : name);
+		if (catd != (nl_catd)-1) return catd;
+	}
+	errno = ENOENT;
 	return (nl_catd)-1;
 }