Add zopen(), a stdio wrapper for gzipped data streams.

Obtained from:	NetBSD

lib/libz/Makefile

@@ -17,7 +17,8 @@ CFLAGS+=	-DHAS_snprintf -DHAS_vsnprintf
 CLEANFILES+=	example.o example foo.gz minigzip.o minigzip
 
 SRCS = adler32.c compress.c crc32.c gzio.c uncompr.c deflate.c trees.c \
-       zutil.c inflate.c infblock.c inftrees.c infcodes.c infutil.c inffast.c
+       zutil.c inflate.c infblock.c inftrees.c infcodes.c infutil.c \
+       inffast.c zopen.c
 INCS=		zconf.h zlib.h
 
 minigzip:	all minigzip.o

lib/libz/zopen.c

@@ -0,0 +1,39 @@
+/*
+ * Public domain stdio wrapper for libz, written by Johan Danielsson.
+ */
+
+#ifndef lint
+static const char rcsid[] = 
+  "$FreeBSD$";
+#endif /* not lint */
+
+#include <stdio.h>
+#include <zlib.h>
+
+FILE *zopen(const char *fname, const char *mode);
+
+/* convert arguments */
+static int
+xgzread(void *cookie, char *data, int size)
+{
+    return gzread(cookie, data, size);
+}
+
+static int
+xgzwrite(void *cookie, const char *data, int size)
+{
+    return gzwrite(cookie, (void*)data, size);
+}
+
+FILE *
+zopen(const char *fname, const char *mode)
+{
+    gzFile gz = gzopen(fname, mode);
+    if(gz == NULL)
+	return NULL;
+
+    if(*mode == 'r')
+	return (funopen(gz, xgzread, NULL, NULL, gzclose));
+    else
+	return (funopen(gz, NULL, xgzwrite, NULL, gzclose));
+}