/*
 * 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);
}