/*
 * Schism Tracker - a cross-platform Impulse Tracker clone
 * copyright (c) 2003-2005 Storlek <storlek@rigelseven.com>
 * copyright (c) 2005-2008 Mrs. Brisby <mrs.brisby@nimh.org>
 * copyright (c) 2009 Storlek & Mrs. Brisby
 * copyright (c) 2010-2012 Storlek
 * URL: http://schismtracker.org/
 *
 * 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 2 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, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#define NEED_BYTESWAP
#include "headers.h"
#include "fmt.h"

// ------------------------------------------------------------------------------------------------------------
// IT decompression code from itsex.c (Cubic Player) and load_it.cpp (Modplug)
// (I suppose this could be considered a merge between the two.)

static uint32_t it_readbits(int8_t n, uint32_t *bitbuf, uint32_t *bitnum, const uint8_t **ibuf)
{
        uint32_t value = 0;
        uint32_t i = n;

        // this could be better
        while (i--) {
                if (!*bitnum) {
                        *bitbuf = *(*ibuf)++;
                        *bitnum = 8;
                }
                value >>= 1;
                value |= (*bitbuf) << 31;
                (*bitbuf) >>= 1;
                (*bitnum)--;
        }
        return value >> (32 - n);
}


void it_decompress8(void *dest, uint32_t len, const void *file, uint32_t filelen, int it215)
{
        const uint8_t *filebuf;         // source buffer containing compressed sample data
        const uint8_t *srcbuf;          // current position in source buffer
        int8_t *destpos;                // position in destination buffer which will be returned
        uint16_t blklen;                // length of compressed data block in samples
        uint16_t blkpos;                // position in block
        uint8_t width;                  // actual "bit width"
        uint16_t value;                 // value read from file to be processed
        int8_t d1, d2;                  // integrator buffers (d2 for it2.15)
        int8_t v;                       // sample value
        uint32_t bitbuf, bitnum;        // state for it_readbits

        filebuf = srcbuf = (const uint8_t *) file;
        destpos = (int8_t *) dest;

        // now unpack data till the dest buffer is full
        while (len) {
                // read a new block of compressed data and reset variables
                // block layout: word size, <size> bytes data
                if (srcbuf + 2 > filebuf + filelen
                    || srcbuf + 2 + (srcbuf[0] | (srcbuf[1] << 8)) > filebuf + filelen) {
                        // truncated!
                        return;
                }
                srcbuf += 2;
                bitbuf = bitnum = 0;

                blklen = MIN(0x8000, len);
                blkpos = 0;

                width = 9; // start with width of 9 bits
                d1 = d2 = 0; // reset integrator buffers

                // now uncompress the data block
                while (blkpos < blklen) {
                        if (width > 9) {
                                // illegal width, abort
                                printf("Illegal bit width %d for 8-bit sample\n", width);
                                return;
                        }
                        value = it_readbits(width, &bitbuf, &bitnum, &srcbuf);

                        if (width < 7) {
                                // method 1 (1-6 bits)
                                // check for "100..."
                                if (value == 1 << (width - 1)) {
                                        // yes!
                                        value = it_readbits(3, &bitbuf, &bitnum, &srcbuf) + 1; // read new width
                                        width = (value < width) ? value : value + 1; // and expand it
                                        continue; // ... next value
                                }
                        } else if (width < 9) {
                                // method 2 (7-8 bits)
                                uint8_t border = (0xFF >> (9 - width)) - 4; // lower border for width chg
                                if (value > border && value <= (border + 8)) {
                                        value -= border; // convert width to 1-8
                                        width = (value < width) ? value : value + 1; // and expand it
                                        continue; // ... next value
                                }
                        } else {
                                // method 3 (9 bits)
                                // bit 8 set?
                                if (value & 0x100) {
                                        width = (value + 1) & 0xff; // new width...
                                        continue; // ... and next value
                                }
                        }

                        // now expand value to signed byte
                        if (width < 8) {
                                uint8_t shift = 8 - width;
                                v = (value << shift);
                                v >>= shift;
                        } else {
                                v = (int8_t) value;
                        }
                        
                        // integrate upon the sample values
                        d1 += v;
                        d2 += d1;
                        
                        // .. and store it into the buffer
                        *(destpos++) = it215 ? d2 : d1;
                        blkpos++;
                }

                // now subtract block length from total length and go on
                len -= blklen;
        }
}

// Mostly the same as above.
void it_decompress16(void *dest, uint32_t len, const void *file, uint32_t filelen, int it215)
{
        const uint8_t *filebuf;         // source buffer containing compressed sample data
        const uint8_t *srcbuf;          // current position in source buffer
        int16_t *destpos;               // position in destination buffer which will be returned
        uint16_t blklen;                // length of compressed data block in samples
        uint16_t blkpos;                // position in block
        uint8_t width;                  // actual "bit width"
        uint32_t value;                 // value read from file to be processed
        int16_t d1, d2;                 // integrator buffers (d2 for it2.15)
        int16_t v;                      // sample value
        uint32_t bitbuf, bitnum;        // state for it_readbits

        filebuf = srcbuf = (const uint8_t *) file;
        destpos = (int16_t *) dest;

        // now unpack data till the dest buffer is full
        while (len) {
                // read a new block of compressed data and reset variables
                // block layout: word size, <size> bytes data
                if (srcbuf + 2 > filebuf + filelen
                    || srcbuf + 2 + (srcbuf[0] | (srcbuf[1] << 8)) > filebuf + filelen) {
                        // truncated!
                        return;
                }
                srcbuf += 2;

                bitbuf = bitnum = 0;

                blklen = MIN(0x4000, len); // 0x4000 samples => 0x8000 bytes again
                blkpos = 0;

                width = 17; // start with width of 17 bits
                d1 = d2 = 0; // reset integrator buffers

                // now uncompress the data block
                while (blkpos < blklen) {
                        if (width > 17) {
                                // illegal width, abort
                                printf("Illegal bit width %d for 16-bit sample\n", width);
                                return;
                        }
                        value = it_readbits(width, &bitbuf, &bitnum, &srcbuf);

                        if (width < 7) {
                                // method 1 (1-6 bits)
                                // check for "100..."
                                if (value == (uint32_t) 1 << (width - 1)) {
                                        // yes!
                                        value = it_readbits(4, &bitbuf, &bitnum, &srcbuf) + 1; // read new width
                                        width = (value < width) ? value : value + 1; // and expand it
                                        continue; // ... next value
                                }
                        } else if (width < 17) {
                                // method 2 (7-16 bits)
                                uint16_t border = (0xFFFF >> (17 - width)) - 8; // lower border for width chg
                                if (value > border && value <= (uint32_t) (border + 16)) {
                                        value -= border; // convert width to 1-8
                                        width = (value < width) ? value : value + 1; // and expand it
                                        continue; // ... next value
                                }
                        } else {
                                // method 3 (17 bits)
                                // bit 16 set?
                                if (value & 0x10000) {
                                        width = (value + 1) & 0xff; // new width...
                                        continue; // ... and next value
                                }
                        }

                        // now expand value to signed word
                        if (width < 16) {
                                uint8_t shift = 16 - width;
                                v = (value << shift);
                                v >>= shift;
                        } else {
                                v = (int16_t) value;
                        }
                        
                        // integrate upon the sample values
                        d1 += v;
                        d2 += d1;
                        
                        // .. and store it into the buffer
                        *(destpos++) = it215 ? d2 : d1;
                        blkpos++;
                }

                // now subtract block length from total length and go on
                len -= blklen;
        }
}

// ------------------------------------------------------------------------------------------------------------
// MDL sample decompression

uint16_t mdl_read_bits(uint32_t *bitbuf, uint32_t *bitnum, uint8_t **ibuf, int8_t n)
{
        uint16_t v = (uint16_t)((*bitbuf) & ((1 << n) - 1) );
        (*bitbuf) >>= n;
        (*bitnum) -= n;
        if ((*bitnum) <= 24) {
                (*bitbuf) |= (((uint32_t)(*(*ibuf)++)) << (*bitnum));
                (*bitnum) += 8;
        }
        return v;
}

