[Patch v3] util: add gzreadline

[David Bremner <david@tethera.net>]

The idea is to provide a more or less drop in replacement for readline
to read from zlib/gzip streams.  Take the opportunity to replace
malloc with talloc.
---

This corrects one nasty bug, and a few style/optimization issues brought up by Tomi.

I'm not sure about the name. I agree in principle it would be good to
signal "talloc". I'm just not sure the best way to do that.

I'm also not sure about the error handling. the "real" getline sets
errno. Should we?

 util/Makefile.local |  2 +-
 util/zlib-extra.c   | 62 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 util/zlib-extra.h   | 10 +++++++++
 3 files changed, 73 insertions(+), 1 deletion(-)
 create mode 100644 util/zlib-extra.c
 create mode 100644 util/zlib-extra.h

diff --git a/util/Makefile.local b/util/Makefile.local
index 29c0ce6..e2a5b65 100644
--- a/util/Makefile.local
+++ b/util/Makefile.local
@@ -4,7 +4,7 @@ dir := util
 extra_cflags += -I$(srcdir)/$(dir)
 
 libutil_c_srcs := $(dir)/xutil.c $(dir)/error_util.c $(dir)/hex-escape.c \
-		  $(dir)/string-util.c $(dir)/talloc-extra.c
+		  $(dir)/string-util.c $(dir)/talloc-extra.c $(dir)/zlib-extra.c
 
 libutil_modules := $(libutil_c_srcs:.c=.o)
 
diff --git a/util/zlib-extra.c b/util/zlib-extra.c
new file mode 100644
index 0000000..7afe175
--- /dev/null
+++ b/util/zlib-extra.c
@@ -0,0 +1,62 @@
+/* zlib-extra.c -  Extra or enhanced routines for compressed I/O.
+ *
+ * Copyright (c) 2014 David Bremner
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see http://www.gnu.org/licenses/ .
+ *
+ * Author: David Bremner <david@tethera.net>
+ */
+
+#include "zlib-extra.h"
+#include <talloc.h>
+#include <stdio.h>
+#include <string.h>
+
+/* mimic POSIX/glibc getline, but on a zlib gzFile stream, and using talloc */
+ssize_t
+gzgetline (void *ctx, char **lineptr, size_t *n, gzFile stream) {
+
+    size_t len = *n;
+    char *buf = *lineptr;
+    size_t offset = 0;
+
+    if (len == 0 || buf == NULL) {
+	/* same as getdelim from gnulib */
+	len = 120;
+	buf = talloc_size (ctx, len);
+	if (buf == NULL)
+	    return -1;
+    }
+
+    while (1) {
+
+	if (!gzgets (stream, buf + offset, len - offset))
+	    return -1;
+
+	offset += strlen (buf+offset);
+
+	if ( buf[offset-1] == '\n' )
+	    break;
+
+	len *= 2;
+	buf = talloc_realloc (ctx, buf, char, len);
+	if (buf == NULL)
+	    return -1;
+
+    }
+
+    *lineptr = buf;
+    *n = len;
+    return offset;
+}
diff --git a/util/zlib-extra.h b/util/zlib-extra.h
new file mode 100644
index 0000000..c18480f
--- /dev/null
+++ b/util/zlib-extra.h
@@ -0,0 +1,10 @@
+#ifndef _ZLIB_EXTRA_H
+#define _ZLIB_EXTRA_H
+
+#include <zlib.h>
+
+/* Like getline, but read from a gzFile. Allocation is with talloc */
+ssize_t
+gzgetline (void *ctx, char **lineptr, size_t *n, gzFile stream);
+
+#endif
-- 
1.9.0