/*
    xa65 - 6502 cross assembler and utility suite
    reloc65 - relocates 'o65' files
    Copyright (C) 1997 Andre Fachat (a.fachat@physik.tu-chemnitz.de)

    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., 675 Mass Ave, Cambridge, MA 02139, USA.
*/

/*
    Modified by Dag Lem <resid@nimrod.no>
    Relocate and extract text segment from memory buffer instead of file.
    For use with VICE VSID.
*/

#include <stdio.h>
#include <string.h>

#include "psid.h"

#define BUF (9 * 2 + 8)         /* 16 bit header */

typedef struct {
    char *fname;
    size_t fsize;
    unsigned char *buf;
    int tbase, tlen, dbase, dlen, bbase, blen, zbase, zlen;
    int tdiff, ddiff, bdiff, zdiff;
    unsigned char *segt;
    unsigned char *segd;
    unsigned char *utab;
    unsigned char *rttab;
    unsigned char *rdtab;
    unsigned char *extab;
} file65;

static int read_options(unsigned char *f);
static int read_undef(unsigned char *f);
static unsigned char *reloc_seg(unsigned char *f, int len, unsigned char *rtab, file65 *fp);
static unsigned char *reloc_globals(unsigned char *, file65 *fp);

static file65 file;
static const unsigned char cmp[] = {1, 0, 'o', '6', '5'};

int reloc65(char **buf, int *fsize, int addr)
{
    int mode, hlen;

    int tflag = 0, dflag = 0, bflag = 0, zflag = 0;
    int tbase = 0, dbase = 0, bbase = 0, zbase = 0;
    int extract = 0;

    file.buf = (unsigned char *)*buf;
    file.fsize = *fsize;
    tflag = 1;
    tbase = addr;
    extract = 1;

    if (memcmp(file.buf, cmp, 5) != 0) {
        return 0;
    }

    mode = file.buf[7] * 256 + file.buf[6];
    if (mode & 0x2000) {
        return 0;
    } else if (mode & 0x4000) {
        return 0;
    }

    hlen = BUF + read_options(file.buf + BUF);

    file.tbase = file.buf[9] * 256 + file.buf[8];
    file.tlen = file.buf[11] * 256 + file.buf[10];
    file.tdiff = tflag ? tbase - file.tbase : 0;
    file.dbase = file.buf[13] * 256 + file.buf[12];
    file.dlen = file.buf[15] * 256 + file.buf[14];
    file.ddiff = dflag ? dbase - file.dbase : 0;
    file.bbase = file.buf[17] * 256 + file.buf[16];
    file.blen = file.buf[19] * 256 + file.buf[18];
    file.bdiff = bflag ? bbase - file.bbase : 0;
    file.zbase = file.buf[21] * 256 + file.buf[20];
    file.zlen = file.buf[23] * 256 + file.buf[21];
    file.zdiff = zflag ? zbase - file.zbase : 0;

    file.segt = file.buf + hlen;
    file.segd = file.segt + file.tlen;
    file.utab = file.segd + file.dlen;

    file.rttab = file.utab + read_undef(file.utab);

    file.rdtab = reloc_seg(file.segt, file.tlen, file.rttab, &file);
    file.extab = reloc_seg(file.segd, file.dlen, file.rdtab, &file);

    reloc_globals(file.extab, &file);

    if (tflag) {
        file.buf[9] = (tbase >> 8) & 255;
        file.buf[8] = tbase & 255;
    }
    if (dflag) {
        file.buf[13] = (dbase >> 8) & 255;
        file.buf[12] = dbase & 255;
    }
    if (bflag) {
        file.buf[17] = (bbase >> 8) & 255;
        file.buf[16] = bbase & 255;
    }
    if (zflag) {
        file.buf[21] = (zbase >> 8) & 255;
        file.buf[20] = zbase & 255;
    }

    switch (extract) {
        case 0: /* whole file */
            return 1;
        case 1: /* text segment */
            *buf = (char *)(file.segt);
            *fsize = file.tlen;
            return 1;
        case 2:
            *buf = (char *)(file.segd);
            *fsize = file.dlen;
            return 1;
        default:
            return 0;
    }
}

static int read_options(unsigned char *buf)
{
    int c, l = 0;

    c = buf[0];
    while (c && c != EOF) {
        c &= 255;
        l += c;
        c = buf[l];
    }
    return ++l;
}

static int read_undef(unsigned char *buf)
{
    int n, l = 2;

    n = buf[0] + 256 * buf[1];
    while (n) {
        n--;
        while (!buf[l++]) {}
    }
    return l;
}

#define reldiff(s) (((s) == 2) ? fp->tdiff : (((s) == 3) ? fp->ddiff : (((s) == 4) ? fp->bdiff : (((s) == 5) ? fp->zdiff : 0))))

static unsigned char *reloc_seg(unsigned char *buf, int len, unsigned char *rtab, file65 *fp)
{
    int adr = -1;
    int type, seg, old, new;
    while (*rtab) {
        if ((*rtab & 255) == 255) {
            adr += 254;
            rtab++;
        } else {
            adr += *rtab & 255;
            rtab++;
            type = *rtab & 0xe0;
            seg = *rtab & 0x07;
            rtab++;
            switch (type) {
                case 0x80:
                    old = buf[adr] + 256 * buf[adr + 1];
                    new = old + reldiff(seg);
                    buf[adr] = new & 255;
                    buf[adr + 1] = (new >> 8) & 255;
                    break;
                case 0x40:
                    old = buf[adr] * 256 + *rtab;
                    new = old + reldiff(seg);
                    buf[adr] = (new >> 8) & 255;
                    *rtab = new & 255;
                    rtab++;
                    break;
                case 0x20:
                    old = buf[adr];
                    new = old + reldiff(seg);
                    buf[adr] = new & 255;
                    break;
            }
            if (seg == 0) {
                rtab += 2;
            }
        }
    }
    return ++rtab;
}

static unsigned char *reloc_globals(unsigned char *buf, file65 *fp)
{
    int n, old, new, seg;

    n = buf[0] + 256 * buf[1];
    buf += 2;

    while (n) {
        while (*(buf++)) {
        }
        seg = *buf;
        old = buf[1] + 256 * buf[2];
        new = old + reldiff(seg);
        buf[1] = new & 255;
        buf[2] = (new >> 8) & 255;
        buf += 3;
        n--;
    }
    return buf;
}