util: add gz_readline

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.

1 files changed, 85 insertions, 0 deletions

diff --git a/util/zlib-extra.c b/util/zlib-extra.c
new file mode 100644
index 00000000..2e704457
--- /dev/null
+++ b/util/zlib-extra.c
@@ -0,0 +1,85 @@
+/* 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 */
+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_ERRNO;
+	    default:
+		return UTIL_GZERROR;
+	    }
+	}
+
+	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;
+}
+
+const char *gz_error_string (util_status_t status, gzFile file)
+{
+    if (status == UTIL_GZERROR)
+	return gzerror (file, NULL);
+    else
+	return util_error_string (status);
+}