From 902f2e19bdb649baee4e07cdb9cc9e7785f209b5 Mon Sep 17 00:00:00 2001 From: David Bremner Date: Fri, 15 Jun 2012 01:08:36 +0300 Subject: [PATCH] hex-escape: (en|de)code strings to/from restricted character set 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 | 161 ++++++++++++++++++++++++++++++++++++++++++++ util/hex-escape.h | 41 +++++++++++ 3 files changed, 203 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 c7cae61e..3ca623ec 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 00000000..b7e2e07a --- /dev/null +++ b/util/hex-escape.c @@ -0,0 +1,161 @@ +/* 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 + */ + +#include +#include +#include +#include +#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 char *p; + char *q; + + size_t needed = 1; /* for the NUL */ + + assert (ctx); assert (in); assert (out); assert (out_size); + + for (p = in; *p; p++) { + needed += is_output (*p) ? 1 : 3; + } + + if (*out == NULL) + *out_size = 0; + + if (!maybe_realloc (ctx, needed, out, out_size)) + return HEX_OUT_OF_MEMORY; + + q = *out; + p = in; + + while (*p) { + if (is_output (*p)) { + *q++ = *p++; + } else { + sprintf (q, "%%%02x", (unsigned char)*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 needed = 1; /* for the NUL */ + + assert (ctx); assert (in); assert (out); assert (out_size); + + for (p = in; *p; p++) + if ((p[0] == escape_char) && isxdigit (p[1]) && isxdigit (p[2])) + needed -= 1; + else + needed += 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 00000000..5182042e --- /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