[Patch v2 01/17] hex-escape: (en|de)code strings to/from restricted character set
david at tethera.net
david at tethera.net
Sat Nov 24 13:20:01 PST 2012
From: David Bremner <bremner at debian.org>
The character set is chosen to be suitable for pathnames, and the same
as that used by contrib/nmbug
[With additions by Jani Nikula]
---
util/Makefile.local | 2 +-
util/hex-escape.c | 168 +++++++++++++++++++++++++++++++++++++++++++++++++++
util/hex-escape.h | 41 +++++++++++++
3 files changed, 210 insertions(+), 1 deletion(-)
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 c7cae61..3ca623e 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..d8905d0
--- /dev/null
+++ b/util/hex-escape.c
@@ -0,0 +1,168 @@
+/* hex-escape.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 at tethera.net>
+ */
+
+#include <assert.h>
+#include <string.h>
+#include <talloc.h>
+#include <ctype.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 char 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 decode 'in' to 'out'.
+ *
+ * This must succeed for in == out to support hex_decode_inplace().
+ */
+static hex_status_t
+hex_decode_internal (const char *in, unsigned char *out)
+{
+ char buf[3];
+
+ while (*in) {
+ if (*in == escape_char) {
+ char *endp;
+
+ /* This also handles unexpected end-of-string. */
+ if (!isxdigit ((unsigned char) in[1]) ||
+ !isxdigit ((unsigned char) in[2]))
+ return HEX_SYNTAX_ERROR;
+
+ buf[0] = in[1];
+ buf[1] = in[2];
+ buf[2] = '\0';
+
+ *out = strtoul (buf, &endp, 16);
+
+ if (endp != buf + 2)
+ return HEX_SYNTAX_ERROR;
+
+ in += 3;
+ out++;
+ } else {
+ *out++ = *in++;
+ }
+ }
+
+ *out = '\0';
+
+ return HEX_SUCCESS;
+}
+
+hex_status_t
+hex_decode_inplace (char *s)
+{
+ /* A decoded string is never longer than the encoded one, so it is
+ * safe to decode a string onto itself. */
+ return hex_decode_internal (s, (unsigned char *) s);
+}
+
+hex_status_t
+hex_decode (void *ctx, const char *in, char **out, size_t * out_size)
+{
+ const char *p;
+ 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;
+
+ return hex_decode_internal (in, (unsigned char *) *out);
+}
diff --git a/util/hex-escape.h b/util/hex-escape.h
new file mode 100644
index 0000000..5182042
--- /dev/null
+++ b/util/hex-escape.h
@@ -0,0 +1,41 @@
+#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 for hex_encode() and hex_decode() 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);
+
+/*
+ * Non-allocating hex decode to decode 's' in-place. The length of the
+ * result is always equal to or shorter than the length of the
+ * original.
+ */
+hex_status_t
+hex_decode_inplace (char *s);
+#endif
--
1.7.10.4
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