/* ndisasm.c   the Netwide Disassembler main module
 *
 * The Netwide Assembler is copyright (C) 1996 Simon Tatham and
 * Julian Hall. All rights reserved. The software is
 * redistributable under the licence given in the file "Licence"
 * distributed in the NASM archive.
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <errno.h>

#include "nasm.h"
#include "nasmlib.h"
#include "sync.h"
#include "disasm.h"

extern long eatbyte (unsigned char *data, char *output);

#define BPL 8                          /* bytes per line of hex dump */

static const char *help =
"usage: ndisasm [-a] [-i] [-h] [-r] [-u] [-b bits] [-o origin] [-s sync...]\n"
"               [-e bytes] [-k start,bytes] file\n"
"   -a or -i activates auto (intelligent) sync\n"
"   -u sets USE32 (32-bit mode)\n"
"   -b 16 or -b 32 sets number of bits too\n"
"   -h displays this text\n"
"   -r displays the version number\n"
"   -e skips <bytes> bytes of header\n"
"   -k avoids disassembling <bytes> bytes from position <start>\n";

static void output_ins (unsigned long, unsigned char *, int, char *);
static void skip (unsigned long dist, FILE *fp);

int main(int argc, char **argv) {
    unsigned char buffer[INSN_MAX * 2], *p, *q;
    char outbuf[256];
    char *pname = *argv;
    char *filename = NULL;
    unsigned long nextsync, synclen, initskip = 0L;
    int lenread, lendis;
    int autosync = FALSE;
    int bits = 16;
    int eof = FALSE;
    int rn_error;
    long offset;
    FILE *fp;

    offset = 0;
    init_sync();

    while (--argc) {
        char *v, *vv, *p = *++argv;
        if (*p == '-') {
            p++;
            while (*p) switch (tolower(*p)) {
              case 'a':                /* auto or intelligent sync */
              case 'i':
                autosync = TRUE;
                p++;
                break;
              case 'h':
                fprintf(stderr, help);
                return 0;
              case 'r':
                fprintf(stderr, "NDISASM version " NASM_VER "\n");
                return 0;
              case 'u':                /* USE32 */
                bits = 32;
                p++;
                break;
              case 'b':                /* bits */
                v = p[1] ? p+1 : --argc ? *++argv : NULL;
                if (!v) {
                    fprintf(stderr, "%s: `-b' requires an argument\n", pname);
                    return 1;
                }
                if (!strcmp(v, "16"))
                    bits = 16;
                else if (!strcmp(v, "32"))
                    bits = 32;
                else {
                    fprintf(stderr, "%s: argument to `-b' should"
                            " be `16' or `32'\n", pname);
                }
                p = "";                /* force to next argument */
                break;
              case 'o':                /* origin */
                v = p[1] ? p+1 : --argc ? *++argv : NULL;
                if (!v) {
                    fprintf(stderr, "%s: `-o' requires an argument\n", pname);
                    return 1;
                }
                offset = readnum (v, &rn_error);
                if (rn_error) {
                    fprintf(stderr, "%s: `-o' requires a numeric argument\n",
                            pname);
                    return 1;
                }
                p = "";                /* force to next argument */
                break;
              case 's':                /* sync point */
                v = p[1] ? p+1 : --argc ? *++argv : NULL;
                if (!v) {
                    fprintf(stderr, "%s: `-s' requires an argument\n", pname);
                    return 1;
                }
                add_sync (readnum (v, &rn_error), 0L);
                if (rn_error) {
                    fprintf(stderr, "%s: `-s' requires a numeric argument\n",
                            pname);
                    return 1;
                }
                p = "";                /* force to next argument */
                break;
              case 'e':                /* skip a header */
                v = p[1] ? p+1 : --argc ? *++argv : NULL;
                if (!v) {
                    fprintf(stderr, "%s: `-e' requires an argument\n", pname);
                    return 1;
                }
                initskip = readnum (v, &rn_error);
                if (rn_error) {
                    fprintf(stderr, "%s: `-e' requires a numeric argument\n",
                            pname);
                    return 1;
                }
                p = "";                /* force to next argument */
                break;
              case 'k':                /* skip a region */
                v = p[1] ? p+1 : --argc ? *++argv : NULL;
                if (!v) {
                    fprintf(stderr, "%s: `-k' requires an argument\n", pname);
                    return 1;
                }
                vv = strchr(v, ',');
                if (!vv) {
                    fprintf(stderr, "%s: `-k' requires two numbers separated"
                            " by a comma\n", pname);
                    return 1;
                }
                *vv++ = '\0';
                nextsync = readnum (v, &rn_error);
                if (rn_error) {
                    fprintf(stderr, "%s: `-k' requires numeric arguments\n",
                            pname);
                    return 1;
                }
                synclen = readnum (vv, &rn_error);
                if (rn_error) {
                    fprintf(stderr, "%s: `-k' requires numeric arguments\n",
                            pname);
                    return 1;
                }
                add_sync (nextsync, synclen);
                p = "";                /* force to next argument */
                break;
            }
        } else if (!filename) {
            filename = p;
        } else {
            fprintf(stderr, "%s: more than one filename specified\n", pname);
            return 1;
        }
    }

    if (!filename) {
        fprintf(stderr, help, pname);
        return 0;
    }

    fp = fopen(filename, "rb");
    if (!fp) {
        fprintf(stderr, "%s: unable to open `%s': %s\n",
                pname, filename, strerror(errno));
        return 1;
    }
    if (initskip > 0)
        skip (initskip, fp);

    /*
     * This main loop is really horrible, and wants rewriting with
     * an axe. It'll stay the way it is for a while though, until I
     * find the energy...
     */

    p = q = buffer;
    nextsync = next_sync (offset, &synclen);
    do {
        unsigned long to_read = buffer+sizeof(buffer)-p;
        if (to_read > nextsync-offset-(p-q))
            to_read = nextsync-offset-(p-q);
        lenread = fread (p, 1, to_read, fp);
        if (lenread == 0)
            eof = TRUE;                /* help along systems with bad feof */
        p += lenread;
        if (offset == nextsync) {
            if (synclen) {
                printf("%08lX  skipping 0x%lX bytes\n", offset, synclen);
                offset += synclen;
                skip (synclen, fp);
            }
            p = q = buffer;
            nextsync = next_sync (offset, &synclen);
        }
        while (p > q && (p - q >= INSN_MAX || lenread == 0)) {
            lendis = disasm (q, outbuf, bits, offset, autosync);
            if (!lendis || lendis > (p - q) ||
                lendis > nextsync-offset)
                lendis = eatbyte (q, outbuf);
            output_ins (offset, q, lendis, outbuf);
            q += lendis;
            offset += lendis;
        }
        if (q >= buffer+INSN_MAX) {
            unsigned char *r = buffer, *s = q;
            int count = p - q;
            while (count--)
                *r++ = *s++;
            p -= (q - buffer);
            q = buffer;
        }
    } while (lenread > 0 || !(eof || feof(fp)));
    fclose (fp);
    return 0;
}

static void output_ins (unsigned long offset, unsigned char *data,
                        int datalen, char *insn) {
    int bytes;
    printf("%08lX  ", offset);

    bytes = 0;
    while (datalen > 0 && bytes < BPL) {
        printf("%02X", *data++);
        bytes++;
        datalen--;
    }

    printf("%*s%s\n", (BPL+1-bytes)*2, "", insn);

    while (datalen > 0) {
        printf("         -");
        bytes = 0;
        while (datalen > 0 && bytes < BPL) {
            printf("%02X", *data++);
            bytes++;
            datalen--;
        }
        printf("\n");
    }
}

/*
 * Skip a certain amount of data in a file, either by seeking if
 * possible, or if that fails then by reading and discarding.
 */
static void skip (unsigned long dist, FILE *fp) {
    char buffer[256];                  /* should fit on most stacks :-) */

    /*
     * Got to be careful with fseek: at least one fseek I've tried
     * doesn't approve of SEEK_CUR. So I'll use SEEK_SET and
     * ftell... horrible but apparently necessary.
     */
    if (fseek (fp, dist+ftell(fp), SEEK_SET)) {
        while (dist > 0) {
            unsigned long len = (dist < sizeof(buffer) ?
                                 dist : sizeof(buffer));
            if (fread (buffer, 1, len, fp) < len) {
                perror("fread");
                exit(1);
            }
            dist -= len;
        }
    }
}
