//
// unhex -- Converts hex dump file back into original binary file.
//
// 30-Mar-2009 tvb www.LeapSecond.com/tools
//

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

#define WIDE 16
int decode_16 (char *line, FILE *f);

// Global variables.

char *Path;

void main (int argc, char *argv[])
{
    char line[1000], dup[1000];
    long n, count;
    FILE *out;
    long line_addr, next_addr;

    if (argc < 2) {
        fprintf(stderr, "Usage: unhex output <input\n");
        exit(1);
    }
    Path = argv[1];
    if (fopen(Path, "r") != NULL) {
        fprintf(stderr, "%s: already exists\n", Path);
        exit(1);
    }
    out = fopen(Path, "wb");
    if (NULL == out) {
        fprintf(stderr, "%s: cannot create\n", Path);
        exit(1);
    }

    count = 0;
    next_addr = 0;
    while (fgets(line, sizeof line, stdin) != NULL) {
        if (strlen(line) < 14) {
            fprintf(stderr, "%s: not hex file (line too short)\n", Path);
            exit(1);
        }
        if (line[8] != ':' && line[8] != '*') {
            fprintf(stderr, "%s: not hex file (missing : or *)\n", Path);
            exit(1);
        }

        sscanf(line, "%x", &line_addr);
        while (line_addr > next_addr) {
            n = decode_16(dup, out);
            if (n != WIDE) {
                fprintf(stderr, "%s: not hex file (dup error)\n", Path);
                exit(1);
            }
            count += n;
            next_addr += WIDE;
        }

        if (line_addr == next_addr) {
            n = decode_16(line, out);
            count += n;
            next_addr += WIDE;
            if (n < WIDE) {
                break;
            }
        }
        if (line[8] == '*') {
            strcpy(dup, line);
        }
    }
    fclose(out);
    fprintf(stderr, "unhex: wrote %ld bytes to %s\n", count, Path);
}

#define RANGE(lo,x,hi) ( (x) >= (lo) && (x) <= (hi) )

int ishex (char c)
{
    return RANGE('0', c, '9') ||
           RANGE('a', c, 'f') ||
           RANGE('A', c, 'F');
}

int hex2dec (char c)
{
    return RANGE('0', c, '9') ? (c - '0') :
           RANGE('a', c, 'f') ? (c - 'a' + 10) :
           RANGE('A', c, 'F') ? (c - 'A' + 10) : -1;
}

int decode_16 (char *line, FILE *f)
{
    int i, n;
    char byte, *p;

    p = &line[8];
    if (*p != ':' && *p != '*') {
        fprintf(stderr, "%s: non hex address: %s\n", Path, line);
        exit(1);
    }

    p += 1;
    if (*p != ' ') {
        fprintf(stderr, "%s: non hex format: %s\n", Path, line);
        exit(1);
    }

    p += 1;
    n = 0;
    for (i = 0; i < WIDE; i += 1, p += 3) {
        if (strncmp(p, "end", 3) == 0) {
            return n;
        }
        if (strncmp(p, "-- ", 3) == 0) {
            return n;
        }
#if 0
        if (strncmp(p, "  ", 2) == 0) {
            return n;
        }
#endif
        if (!ishex(p[0]) || !ishex(p[1]) || p[2] != ' ') {
            fprintf(stderr, "%s: malformed hex digits: %s\n", Path, line);
            exit(1);
        }
        byte = hex2dec(p[0]) * 16 + hex2dec(p[1]);
        fwrite(&byte, 1, 1, f);
        n += 1;
    }

    return n;
}