hugo.c

/* hugo.c  Treaty of Babel module for hugo files
 * 2006 By L. Ross Raszewski
 *
 * This file depends on treaty_builder.h
 *
 * This file is public domain, but note that any changes to this file
 * may render it noncompliant with the Treaty of Babel
 */

#define FORMAT hugo
#define HOME_PAGE "http://www.generalcoffee.com"
#define FORMAT_EXT ".hex"
#define NO_METADATA
#define NO_COVER

#include "treaty_builder.h"
#include <ctype.h>
#include <stdio.h>

static int number_of_hexadecimals_before_hyphen(char *s, size_t len)
{
    size_t offset = 0;

    while (offset < len && isxdigit(s[offset]))
        offset++;

    if (offset == len || (offset < len && s[offset] == '-'))
        return offset;

    return 0;
}

/* We look for the pattern XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX (8-4-4-4-12)
 * where X is a number or A-F.
 * One Hugo game, PAXLess, uses lowercase letters. The rest all use uppercase.
 */
static int isUUID(char *s)
{
    if (!(number_of_hexadecimals_before_hyphen(s, 9) == 8))
        return 0;
    if (!(number_of_hexadecimals_before_hyphen(s+9, 5) == 4))
        return 0;
    if (!(number_of_hexadecimals_before_hyphen(s+14, 5) == 4))
        return 0;
    if (!(number_of_hexadecimals_before_hyphen(s+19, 5) == 4))
        return 0;
    if (!(number_of_hexadecimals_before_hyphen(s+24, 12) == 12))
        return 0;
    return 1;
}

/* The Hugo text obfuscation adds 20 to every character */
static char hugo_decode(char c)
{
    int decoded_char = c - 20;
    if (decoded_char < 0)
        decoded_char = decoded_char + 256;
    return (char)decoded_char;
}

static int32 get_story_file_IFID(void *s_file, int32 extent, char *output, int32 output_extent)
{

    size_t i,j;
    char ser[9];
    char buffer[32];
    char UUID_candidate[37];
    char hyphen = '-'+20;

    char *story_file = (char *) s_file;

    if (extent<0x0B) return INVALID_STORY_FILE_RV;

    for(i=0;i<extent-28;i++)
    {
        /* First we look for an obfuscated hyphen, '-' + 20 */
        /* We need to look 8 characters behind and 28 ahead */
        if (story_file[i] == hyphen && i >= 8 && extent-i >= 28 &&
            story_file[i+5] == hyphen &&
            story_file[i+10] == hyphen &&
            story_file[i+15] == hyphen)
        {
            for (j=0;j<36;j++)
            {
                UUID_candidate[j] = hugo_decode(story_file[i+j-8]);
            }
            if (isUUID(UUID_candidate))
            {
                /* Found valid UUID at file offset i - 8 */
                ASSERT_OUTPUT_SIZE((signed) 37);
                memcpy(output,UUID_candidate,36);
                output[36]='\0';
                return 1;
            }
        }
    }

    /* Found no UUID in file. Construct legacy IFID */

    memcpy(ser, (char *) story_file+0x03, 8);
    ser[8]=0;

    for(j=0;j<8;j++)
        if (!isalnum(ser[j])) ser[j]='-';

    sprintf(buffer,"HUGO-%d-%02X-%02X-%s",story_file[0],story_file[1], story_file[2],ser);

    ASSERT_OUTPUT_SIZE((signed) strlen(buffer)+1);
    strcpy((char *)output,buffer);
    return 1;
}

static uint32 read_hugo_addx(unsigned char *from)
{
    return ((uint32) from[0])| ((uint32)from[1] << 8);
}

static int32 claim_story_file(void *story_file, int32 exten)
{
    unsigned char *sf=(unsigned char *)story_file;
    int32 i;
    int32 scale;
    uint32 extent=(uint32) exten;

    if (!story_file || extent < 0x28) return  INVALID_STORY_FILE_RV;

    /* 39 is the largest version currently accepted by the Hugo interpreter:
       https://github.com/garglk/garglk/blob/master/terps/hugo/source/hemisc.c#L1310-L1362
    */
    if (sf[0] > 39) return INVALID_STORY_FILE_RV;

    if (sf[0]<34) scale=4;
    else scale=16;
    for(i=3;i<0x0B;i++) if (sf[i]<0x20 || sf[i]>0x7e) return INVALID_STORY_FILE_RV;
    for(i=0x0b;i<0x18;i+=2)
        if (read_hugo_addx(sf+i) * scale > extent) return INVALID_STORY_FILE_RV;

    return VALID_STORY_FILE_RV;
}