resources/js/helpers/bps.js

   1 import CRC32 from 'crc-32';
   2
   3 const ACTION_SOURCE_READ = 0;
   4 const ACTION_TARGET_READ = 1;
   5 const ACTION_SOURCE_COPY = 2;
   6 const ACTION_TARGET_COPY = 3;
   7
   8 /**
   9  * Class to apply and create BPS's.
  10  *
  11  * @see https://www.romhacking.net/documents/746/
  12  */
  13 export default class BPS {
  14
  15         constructor() {
  16                 this.sourceSize = 0;
  17                 this.targetSize = 0;
  18                 this.metaDataString = "";
  19                 this.meta = {};
  20                 this.actionsOffset = 0;
  21                 this.sourceFile = null;
  22                 this.sourceChecksum = 0;
  23                 this.targetFile = null;
  24                 this.targetChecksum = 0;
  25                 this.patchSourceChecksum = 0;
  26                 this.patchTargetChecksum = 0;
  27                 this.patchChecksum = 0;
  28                 this.patchFile = null;
  29         }
  30
  31         /**
  32          * Set the patch file to be used.
  33          *
  34          * @param file BPS formatted file.
  35          */
  36         setPatch(file) {
  37                 this.patchFile = new Uint8Array(file);
  38
  39                 // Check BPS1 at beginning of patch file
  40                 const checkHeader = new Uint32Array(file.slice(0, 4))[0];
  41                 if (checkHeader !== 827543618) {
  42                         throw new Error("Not a valid patch file");
  43                 }
  44
  45                 let seek = 4; // skip BPS1
  46                 const decodedSourceSize = this.decodeBPS(this.patchFile, seek);
  47                 this.sourceSize = decodedSourceSize.number;
  48                 seek += decodedSourceSize.length;
  49                 const decodedTargetSize = this.decodeBPS(this.patchFile, seek);
  50                 this.targetSize = decodedTargetSize.number;
  51                 seek += decodedTargetSize.length;
  52
  53                 const decodedMetaDataLength = this.decodeBPS(this.patchFile, seek);
  54
  55                 seek += decodedMetaDataLength.length;
  56                 if (decodedMetaDataLength.number) {
  57                         const metaArray = this.patchFile.slice(
  58                                 seek,
  59                                 seek + decodedMetaDataLength.number
  60                         );
  61                         for (let i = 0; i < metaArray.byteLength; ++i) {
  62                                 this.metaDataString += String.fromCharCode(metaArray[i]);
  63                         }
  64                         this.meta = JSON.parse(this.metaDataString);
  65                         seek += decodedMetaDataLength.number;
  66                 }
  67
  68                 this.actionsOffset = seek;
  69
  70                 const buf32 = new Int32Array(file.slice(file.byteLength - 12));
  71
  72                 this.patchSourceChecksum = buf32[0];
  73                 this.patchTargetChecksum = buf32[1];
  74                 this.patchChecksum = buf32[2];
  75
  76                 if (
  77                         this.patchChecksum !==
  78                         CRC32.buf(this.patchFile.slice(0, this.patchFile.byteLength - 4))
  79                 ) {
  80                         throw new Error("Patch checksum incorrect");
  81                 }
  82
  83                 return this;
  84         }
  85
  86         setSource(file) {
  87                 this.sourceFile = new Uint8Array(file);
  88                 this.sourceChecksum = CRC32.buf(file);
  89
  90                 return this;
  91         }
  92
  93         setTarget(file) {
  94                 this.targetFile = new Uint8Array(file);
  95                 this.targetChecksum = CRC32.buf(file);
  96
  97                 return this;
  98         }
  99
 100         /**
 101          * Apply the currently loaded patch to the currently loaded file
 102          * and return the patched array buffer.
 103          */
 104         applyPatch() {
 105                 if (this.patchFile === null) {
 106                         throw new Error("Patch not set");
 107                 }
 108
 109                 if (this.sourceFile === null) {
 110                         throw new Error("Source not set");
 111                 }
 112
 113                 if (this.patchSourceChecksum !== this.sourceChecksum) {
 114                         throw new Error("Source checksum incorrect");
 115                 }
 116
 117                 let newFileSize = 0;
 118                 let seek = this.actionsOffset;
 119
 120                 // determine target filesize
 121                 while (seek < this.patchFile.byteLength - 12) {
 122                         let data = this.decodeBPS(this.patchFile, seek);
 123                         let action = {
 124                                 type: data.number & 3,
 125                                 length: (data.number >> 2) + 1
 126                         };
 127
 128                         seek += data.length;
 129
 130                         newFileSize += action.length;
 131
 132                         switch (action.type) {
 133                                 case ACTION_TARGET_READ:
 134                                         seek += action.length;
 135                                         break;
 136                                 case ACTION_SOURCE_COPY:
 137                                 case ACTION_TARGET_COPY:
 138                                         seek += this.decodeBPS(this.patchFile, seek).length;
 139                                         break;
 140                         }
 141                 }
 142
 143                 const tempFile = new ArrayBuffer(newFileSize);
 144                 const tempFileView = new Uint8Array(tempFile);
 145
 146                 // patch
 147                 let outputOffset = 0;
 148                 let sourceRelativeOffset = 0;
 149                 let targetRelativeOffset = 0;
 150
 151                 seek = this.actionsOffset;
 152
 153                 while (seek < this.patchFile.byteLength - 12) {
 154                         const data = this.decodeBPS(this.patchFile, seek);
 155                         let data2;
 156                         const action = {
 157                                 type: data.number & 3,
 158                                 length: (data.number >> 2) + 1
 159                         };
 160
 161                         seek += data.length;
 162
 163                         switch (action.type) {
 164                                 case ACTION_SOURCE_READ:
 165                                         for (let i = 0; i < action.length; ++i) {
 166                                                 tempFileView[outputOffset + i] = this.sourceFile[outputOffset + i];
 167                                         }
 168                                         outputOffset += action.length;
 169                                         break;
 170                                 case ACTION_TARGET_READ:
 171                                         for (let i = 0; i < action.length; ++i) {
 172                                                 tempFileView[outputOffset + i] = this.patchFile[seek + i];
 173                                         }
 174                                         outputOffset += action.length;
 175                                         seek += action.length;
 176                                         break;
 177                                 case ACTION_SOURCE_COPY:
 178                                         data2 = this.decodeBPS(this.patchFile, seek);
 179                                         seek += data2.length;
 180                                         sourceRelativeOffset +=
 181                                                 (data2.number & 1 ? -1 : 1) * (data2.number >> 1);
 182                                         while (action.length--) {
 183                                                 tempFileView[outputOffset] = this.sourceFile[sourceRelativeOffset];
 184                                                 outputOffset++;
 185                                                 sourceRelativeOffset++;
 186                                         }
 187                                         break;
 188                                 case ACTION_TARGET_COPY:
 189                                         data2 = this.decodeBPS(this.patchFile, seek);
 190                                         seek += data2.length;
 191                                         targetRelativeOffset +=
 192                                                 (data2.number & 1 ? -1 : 1) * (data2.number >> 1);
 193                                         while (action.length--) {
 194                                                 tempFileView[outputOffset] = tempFileView[targetRelativeOffset];
 195                                                 outputOffset++;
 196                                                 targetRelativeOffset++;
 197                                         }
 198                                         break;
 199                         }
 200                 }
 201
 202                 this.setTarget(tempFile);
 203
 204                 if (this.patchTargetChecksum !== this.targetChecksum) {
 205                         throw new Error("Target checksum incorrect");
 206                 }
 207
 208                 return tempFile;
 209         }
 210
 211         /**
 212          * Create a patch from the source and target binaries and return it as an
 213          * array buffer.
 214          */
 215         createPatch() {
 216                 throw new Error("Not Currently Implemented");
 217         }
 218
 219         /**
 220          * Convert BPS number format into number.
 221          *
 222          * @todo this is inherrently dangerous with while(true)
 223          *
 224          * @param dataBytes
 225          * @param i
 226          */
 227         decodeBPS(dataBytes, i) {
 228                 let number = 0;
 229                 let shift = 1;
 230                 let len = 0;
 231                 for (let j = 0; j < 16; ++j) {
 232                         let x = dataBytes[i];
 233                         i++;
 234                         len++;
 235                         number += (x & 0x7f) * shift;
 236                         if (x & 0x80) {
 237                                 break;
 238                         }
 239                         shift <<= 7;
 240                         number += shift;
 241                 }
 242                 return {
 243                         number: number,
 244                         length: len
 245                 };
 246         }
 247
 248         /**
 249          * Convert number into BPS number format.
 250          *
 251          * @todo this is inherrently dangerous with while(true)
 252          *
 253          * @param toEncode
 254          */
 255         encodeBPS(toEncode) {
 256                 let array = [];
 257
 258                 for (let i = 0; i < 16; ++i) {
 259                         let x = toEncode & 0x7f;
 260                         toEncode >>= 7;
 261                         if (toEncode === 0) {
 262                                 array.push(0x80 | x);
 263
 264                                 break;
 265                         }
 266                         array.push(x);
 267                         toEncode--;
 268                 }
 269
 270                 return Uint8Array.from(array);
 271         }
 272 }