/*
 *  ber_decoder.c
 *
 *  Copyright 2013 Michael Zillgith
 *
 *  This file is part of libIEC61850.
 *
 *  libIEC61850 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.
 *
 *  libIEC61850 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 libIEC61850.  If not, see <http://www.gnu.org/licenses/>.
 *
 *  See COPYING file for the complete license text.
 */

#include "ber_decode.h"
#include "platform_endian.h"

int
BerDecoder_decodeLength(uint8_t* buffer, int* length, int bufPos, int maxBufPos)
{
    if (bufPos >= maxBufPos)
        return -1;

    uint8_t len1 = buffer[bufPos++];

    if (len1 & 0x80) {
        int lenLength = len1 & 0x7f;

        if (lenLength == 0) { /* indefinite length form */
            *length = -1;
        }
        else {
            *length = 0;

            int i;
            for (i = 0; i < lenLength; i++) {
                if (bufPos >= maxBufPos)
                    return -1;

                *length <<= 8;
                *length += buffer[bufPos++];
            }
        }

    }
    else {
        *length = len1;
    }

    return bufPos;
}

char*
BerDecoder_decodeString(uint8_t* buffer, int strlen, int bufPos, int maxBufPos)
{
    char* string = (char*) malloc(strlen + 1);
    memcpy(string, buffer + bufPos, strlen);
    string[strlen] = 0;

    return string;
}

uint32_t
BerDecoder_decodeUint32(uint8_t* buffer, int intlen, int bufPos) {
    uint32_t value = 0;

    int i;
    for (i = 0; i < intlen; i++) {
        value <<= 8;
        value += buffer[bufPos + i];
    }

    return value;
}

float
BerDecoder_decodeFloat(uint8_t* buffer, int bufPos)
{
    float value;
    uint8_t* valueBuf = (uint8_t*) &value;

    int i;

    bufPos += 1; /* skip exponentWidth field */

#if (ORDER_LITTLE_ENDIAN == 1)
    for (i = 3; i >= 0; i--) {
        valueBuf[i] = buffer[bufPos++];
    }
#else
    for (i = 0; i < 4; i++) {
        valueBuf[i] = buffer[bufPos++];
    }
#endif

    return value;
}

double
BerDecoder_decodeDouble(uint8_t* buffer, int bufPos)
{
    double value;
    uint8_t* valueBuf = (uint8_t*) &value;

    int i;

    bufPos += 1; /* skip exponentWidth field */

#if (ORDER_LITTLE_ENDIAN == 1)
    for (i = 7; i >= 0; i--) {
        valueBuf[i] = buffer[bufPos++];
    }
#else
    for (i = 0; i < 8; i++) {
        valueBuf[i] = buffer[bufPos++];
    }
#endif

    return value;
}

bool
BerDecoder_decodeBoolean(uint8_t* buffer, int bufPos) {
    if (buffer[bufPos] != 0)
        return true;
    else
        return false;
}