[PATCH Draft 2 1/9] hex-escape: (en|de)code strings to/from restricted character set

[David Bremner <david@tethera.net>]

From: David Bremner <bremner@debian.org>

The character set is chosen to be suitable for pathnames, and the same
as that used by contrib/nmbug
---
 util/Makefile.local |    2 +-
 util/hex-escape.c   |  156 +++++++++++++++++++++++++++++++++++++++++++++++++++
 util/hex-escape.h   |   32 +++++++++++
 3 files changed, 189 insertions(+), 1 deletions(-)
 create mode 100644 util/hex-escape.c
 create mode 100644 util/hex-escape.h

diff --git a/util/Makefile.local b/util/Makefile.local
index 26e4c3f..2e63932 100644
--- a/util/Makefile.local
+++ b/util/Makefile.local
@@ -3,7 +3,7 @@
 dir := util
 extra_cflags += -I$(srcdir)/$(dir)
 
-libutil_c_srcs := $(dir)/xutil.c $(dir)/error_util.c
+libutil_c_srcs := $(dir)/xutil.c $(dir)/error_util.c $(dir)/hex-escape.c
 
 libutil_modules := $(libutil_c_srcs:.c=.o)
 
diff --git a/util/hex-escape.c b/util/hex-escape.c
new file mode 100644
index 0000000..f58b9a2
--- /dev/null
+++ b/util/hex-escape.c
@@ -0,0 +1,156 @@
+/* pathname.c -  Manage encoding and decoding of byte strings into path names
+ *
+ * Copyright (c) 2011 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 <assert.h>
+#include <string.h>
+#include <talloc.h>
+#include "error_util.h"
+#include "hex-escape.h"
+
+static const size_t default_buf_size = 1024;
+
+static const char *output_charset =
+    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+-_@=.:,";
+
+static const int escape_char = '%';
+
+static int
+is_output (char c)
+{
+    return (strchr (output_charset, c) != NULL);
+}
+
+static int
+maybe_realloc (void *ctx, size_t needed, char **out, size_t *out_size)
+{
+    if (*out_size < needed) {
+
+	if (*out == NULL)
+	    *out = talloc_size (ctx, needed);
+	else
+	    *out = talloc_realloc (ctx, *out, char, needed);
+
+	if (*out == NULL)
+	    return 0;
+
+	*out_size = needed;
+    }
+    return 1;
+}
+
+hex_status_t
+hex_encode (void *ctx, const char *in, char **out, size_t *out_size)
+{
+
+    const unsigned char *p;
+    char *q;
+
+    size_t escape_count = 0;
+    size_t len = 0;
+    size_t needed;
+
+    assert (ctx); assert (in); assert (out); assert (out_size);
+
+    for (p = (unsigned char *) in; *p; p++) {
+	escape_count += (!is_output (*p));
+	len++;
+    }
+
+    needed = len + escape_count * 2 + 1;
+
+    if (*out == NULL)
+	*out_size = 0;
+
+    if (!maybe_realloc (ctx, needed, out, out_size))
+	return HEX_OUT_OF_MEMORY;
+
+    q = *out;
+    p = (unsigned char *) in;
+
+    while (*p) {
+	if (is_output (*p)) {
+	    *q++ = *p++;
+	} else {
+	    sprintf (q, "%%%02x", *p++);
+	    q += 3;
+	}
+    }
+
+    *q = '\0';
+    return HEX_SUCCESS;
+}
+
+hex_status_t
+hex_decode (void *ctx, const char *in, char **out, size_t * out_size)
+{
+
+    char buf[3];
+
+    const char *p;
+    unsigned char *q;
+
+    size_t escape_count = 0;
+    size_t needed = 0;
+
+    assert (ctx); assert (in); assert (out); assert (out_size);
+
+    size_t len = strlen (in);
+
+    for (p = in; *p; p++)
+	escape_count += (*p == escape_char);
+
+    needed = len - escape_count * 2 + 1;
+
+    if (!maybe_realloc (ctx, needed, out, out_size))
+	return HEX_OUT_OF_MEMORY;
+
+    p = in;
+    q = (unsigned char *) *out;
+    buf[2] = 0;
+
+    while (*p) {
+
+	if (*p == escape_char) {
+
+	    char *endp;
+
+	    if (len < 3)
+		return HEX_SYNTAX_ERROR;
+
+	    buf[0] = p[1];
+	    buf[1] = p[2];
+
+	    *q = strtol (buf, &endp, 16);
+
+	    if (endp != buf + 2)
+		return HEX_SYNTAX_ERROR;
+
+	    len -= 3;
+	    p += 3;
+	    q++;
+	} else {
+	    *q++ = *p++;
+	}
+    }
+
+    *q = '\0';
+
+    return HEX_SUCCESS;
+}
diff --git a/util/hex-escape.h b/util/hex-escape.h
new file mode 100644
index 0000000..e409626
--- /dev/null
+++ b/util/hex-escape.h
@@ -0,0 +1,32 @@
+#ifndef _HEX_ESCAPE_H
+#define _HEX_ESCAPE_H
+
+typedef enum hex_status {
+    HEX_SUCCESS = 0,
+    HEX_SYNTAX_ERROR,
+    HEX_OUT_OF_MEMORY
+} hex_status_t;
+
+/*
+ * The API is modelled on that for getline.
+ *
+ * If 'out' points to a NULL pointer a char array of the appropriate
+ * size is allocated using talloc, and out_size is updated.
+ *
+ * If 'out' points to a non-NULL pointer, it assumed to describe an
+ * existing char array, with the size given in *out_size.  This array
+ * may be resized by talloc_realloc if needed; in this case *out_size
+ * will also be updated.
+ *
+ * Note that it is an error to pass a NULL pointer for any parameter
+ * of these routines.
+ */
+
+hex_status_t
+hex_encode (void *talloc_ctx, const char *in, char **out,
+            size_t *out_size);
+
+hex_status_t
+hex_decode (void *talloc_ctx, const char *in, char **out,
+            size_t *out_size);
+#endif
-- 
1.7.7.3