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.

util/Makefile.local

@@ -4,7 +4,8 @@ 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 \
+		$(dir)/util.c
 
 libutil_modules := $(libutil_c_srcs:.c=.o)
 

util/util.c

@@ -0,0 +1,24 @@
+#include "util.h"
+#include "error_util.h"
+#include <string.h>
+#include <errno.h>
+
+const char *
+util_error_string (util_status_t errnum)
+{
+    switch (errnum) {
+    case UTIL_SUCCESS:
+	return "success";
+    case UTIL_OUT_OF_MEMORY:
+	return "out of memory";
+    case UTIL_EOF:
+	return "end of file";
+    case UTIL_ERRNO:
+	return strerror (errno);
+    case UTIL_GZERROR:
+	/* we lack context to be more informative here */
+	return "zlib error";
+    default:
+	INTERNAL_ERROR("unexpected error status %d", errnum);
+    }
+}

util/util.h

@@ -0,0 +1,29 @@
+#ifndef _UTIL_H
+#define _UTIL_H
+
+typedef enum util_status {
+    /**
+     * No error occurred.
+     */
+    UTIL_SUCCESS = 0,
+    /**
+     * Out of memory.
+     */
+    UTIL_OUT_OF_MEMORY,
+    /**
+     * End of stream reached while attempting to read.
+     */
+    UTIL_EOF,
+    /**
+     * Low level error occured, consult errno.
+     */
+    UTIL_ERRNO,
+    /**
+     * Zlib error occured, call gzerror for details.
+     */
+    UTIL_GZERROR
+} util_status_t;
+
+const char *
+util_error_string (util_status_t status);
+#endif

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);
+}

util/zlib-extra.h

@@ -0,0 +1,25 @@
+#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.
+ * Returns:
+ *
+ *   UTIL_SUCCESS, UTIL_OUT_OF_MEMORY, UTIL_ERRNO, UTIL_GZERROR
+ *			Consult util.h for description
+ *
+ *   UTIL_EOF		End of file encountered before
+ *			any characters read
+ */
+util_status_t
+gz_getline (void *ctx, char **lineptr, ssize_t *bytes_read, gzFile stream);
+
+/* return a suitable error string based on the return status
+ *  from gz_readline
+ */
+
+const char *
+gz_error_string (util_status_t status, gzFile stream);
+#endif