[Patch v6 2/6] util: add gz_readline

[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/util.h         | 12 +++++++++
 util/zlib-extra.c   | 77 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 util/zlib-extra.h   | 11 ++++++++
 4 files changed, 101 insertions(+), 1 deletion(-)
 create mode 100644 util/util.h
 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/util.h b/util/util.h
new file mode 100644
index 0000000..8663cfc
--- /dev/null
+++ b/util/util.h
@@ -0,0 +1,12 @@
+#ifndef _UTIL_H
+#define _UTIL_H
+
+typedef enum util_status {
+    UTIL_SUCCESS = 0,
+    UTIL_ERROR = 1,
+    UTIL_OUT_OF_MEMORY,
+    UTIL_EOF,
+    UTIL_FILE,
+} util_status_t;
+
+#endif
diff --git a/util/zlib-extra.c b/util/zlib-extra.c
new file mode 100644
index 0000000..922ab52
--- /dev/null
+++ b/util/zlib-extra.c
@@ -0,0 +1,77 @@
+/* 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 */
+util_status_t
+gz_getline (void *talloc_ctx, char **bufptr, ssize_t *bytes_read, gzFile stream)
+{
+    char *buf = *bufptr;
+    unsigned int len;
+    size_t offset = 0;
+
+    if (buf) {
+	len = talloc_array_length (buf);
+    } else {
+	/* same as getdelim from gnulib */
+	len = 120;
+	buf = talloc_array (talloc_ctx, char, len);
+	if (buf == NULL)
+	    return UTIL_OUT_OF_MEMORY;
+    }
+
+    while (1) {
+	if (! gzgets (stream, buf + offset, len - offset)) {
+	    /* Null indicates EOF or error */
+	    int zlib_status = 0;
+	    (void) gzerror (stream, &zlib_status);
+	    switch (zlib_status) {
+	    case Z_OK:
+		/* no data read before EOF */
+		if (offset == 0)
+		    return UTIL_EOF;
+		else
+		    goto SUCCESS;
+	    case Z_ERRNO:
+		return UTIL_FILE;
+	    default:
+		return UTIL_ERROR;
+	    }
+	}
+
+	offset += strlen (buf + offset);
+
+	if (buf[offset - 1] == '\n')
+	    goto SUCCESS;
+
+	len *= 2;
+	buf = talloc_realloc (talloc_ctx, buf, char, len);
+	if (buf == NULL)
+	    return UTIL_OUT_OF_MEMORY;
+    }
+ SUCCESS:
+    *bufptr = buf;
+    *bytes_read = offset;
+    return UTIL_SUCCESS;
+}
diff --git a/util/zlib-extra.h b/util/zlib-extra.h
new file mode 100644
index 0000000..ed67115
--- /dev/null
+++ b/util/zlib-extra.h
@@ -0,0 +1,11 @@
+#ifndef _ZLIB_EXTRA_H
+#define _ZLIB_EXTRA_H
+
+#include "util.h"
+#include <zlib.h>
+
+/* Like getline, but read from a gzFile. Allocation is with talloc */
+util_status_t
+gz_getline (void *ctx, char **lineptr, ssize_t *bytes_read, gzFile stream);
+
+#endif
-- 
1.9.0