[Patch v2 2/3] util: add gzreadline

[David Bremner]

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.
---
 util/Makefile.local |  2 +-
 util/zlib-extra.c   | 59 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 util/zlib-extra.h   | 10 +++++++++
 3 files changed, 70 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..cda369f
--- /dev/null
+++ b/util/zlib-extra.c
@@ -0,0 +1,59 @@
+/* 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 at 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) {
+	/* XXX arbitrary choice of initial size */
+	len = BUFSIZ;
+	buf = talloc_size (ctx, len);
+    }
+
+    while (1) {
+
+	if (!gzgets (stream, buf + offset, len))
+	    return -1;
+
+	/* XXX wasted effort re-counting length of whole line */
+	offset = strlen (buf);
+
+	if ( buf[offset-1] == '\n' )
+	    break;
+
+	len *= 2;
+	buf = talloc_realloc (ctx, buf, char, len);
+
+    }
+
+    *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