/*
 * Copyright (C) Internet Systems Consortium, Inc. ("ISC")
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
 * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
 * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
 * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
 * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
 * PERFORMANCE OF THIS SOFTWARE.
 */

/* $Id: hex.c,v 1.5 2020/02/26 18:47:59 florian Exp $ */

/*! \file */

#include <ctype.h>
#include <string.h>

#include <isc/buffer.h>
#include <isc/hex.h>
#include <isc/region.h>
#include <isc/types.h>
#include <isc/util.h>

#define RETERR(x) do { \
	isc_result_t _r = (x); \
	if (_r != ISC_R_SUCCESS) \
		return (_r); \
	} while (0)

static const char hex[] = "0123456789ABCDEF";

isc_result_t
isc_hex_totext(isc_region_t *source, int wordlength,
	       const char *wordbreak, isc_buffer_t *target)
{
	char buf[3];
	unsigned int loops = 0;

	if (wordlength < 2)
		wordlength = 2;

	memset(buf, 0, sizeof(buf));
	while (source->length > 0) {
		buf[0] = hex[(source->base[0] >> 4) & 0xf];
		buf[1] = hex[(source->base[0]) & 0xf];
		RETERR(isc_str_tobuffer(buf, target));
		isc_region_consume(source, 1);

		loops++;
		if (source->length != 0 &&
		    (int)((loops + 1) * 2) >= wordlength)
		{
			loops = 0;
			RETERR(isc_str_tobuffer(wordbreak, target));
		}
	}
	return (ISC_R_SUCCESS);
}

/*%
 * State of a hex decoding process in progress.
 */
typedef struct {
	int length;		/*%< Desired length of binary data or -1 */
	isc_buffer_t *target;	/*%< Buffer for resulting binary data */
	int digits;		/*%< Number of buffered hex digits */
	int val[2];
} hex_decode_ctx_t;

static inline void
hex_decode_init(hex_decode_ctx_t *ctx, int length, isc_buffer_t *target)
{
	ctx->digits = 0;
	ctx->length = length;
	ctx->target = target;
}

static inline isc_result_t
hex_decode_char(hex_decode_ctx_t *ctx, int c) {
	const char *s;

	if ((s = strchr(hex, toupper(c))) == NULL)
		return (ISC_R_BADHEX);
	ctx->val[ctx->digits++] = (int)(s - hex);
	if (ctx->digits == 2) {
		unsigned char num;

		num = (ctx->val[0] << 4) + (ctx->val[1]);
		RETERR(isc_mem_tobuffer(ctx->target, &num, 1));
		if (ctx->length >= 0) {
			if (ctx->length == 0)
				return (ISC_R_BADHEX);
			else
				ctx->length -= 1;
		}
		ctx->digits = 0;
	}
	return (ISC_R_SUCCESS);
}

static inline isc_result_t
hex_decode_finish(hex_decode_ctx_t *ctx) {
	if (ctx->length > 0)
		return (ISC_R_UNEXPECTEDEND);
	if (ctx->digits != 0)
		return (ISC_R_BADHEX);
	return (ISC_R_SUCCESS);
}

isc_result_t
isc_hex_decodestring(const char *cstr, isc_buffer_t *target) {
	hex_decode_ctx_t ctx;

	hex_decode_init(&ctx, -1, target);
	for (;;) {
		int c = *cstr++;
		if (c == '\0')
			break;
		if (c == ' ' || c == '\t' || c == '\n' || c== '\r')
			continue;
		RETERR(hex_decode_char(&ctx, c));
	}
	RETERR(hex_decode_finish(&ctx));
	return (ISC_R_SUCCESS);
}