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| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 | 2x 2x 58x 26x 8x 14x 10x 20x 12x 8x 53x 53x 5x 48x 43x 43x 43x 43x 48x 48x 43x 43x 43x 5x 5x 5x 5x 5x 5x 29x 29x 29x 29x 29x 29x 29x 10x 10x 10x 10x 10x 10x 10x 9x 9x 9x 9x 9x 9x 9x 9x 9x 4x 4x 4x 4x 4x 4x 4x 4x 4x 4x 43x 43x 57x 57x 57x 5x 52x 4x 4x 29x 29x 10x 10x 9x 9x 52x 52x 48x 4x 43x 43x 2x 2x 2x 2x | // -*- js-indent: 2 -*-
// Interpreter for bit syntax AST.
// Grammar:
//
// pattern := segment ("," segment)*
// segment := (value | var) (":" size)? ("/" specifier ("-" specifier)*)? | string
// var := "_" | identifier
// size := integer | var
// specifier := "little" | "big" | "signed" | "unsigned" | "unit" ":" 0..256 | type
// type := "integer" | "binary" | "float"
//
// where integer has the obvious meaning, and identifier is anything
// other than "_" that fits the JavaScript identifier specification.
//
// We'll use an object to represent each segment, and an array of
// segments for a pattern. We won't try to optimise for groups of
// patterns; we'll just step through each to see if it works. We rely
// a hypothetical prior step to check that it's a valid pattern.
// ? compile to intermediate instructions ?
// A segment looks like
// {
// type: string, // 'string' is special case
// size: integer | true, // true means 'all remaining'
// name: string | null, // (may be '_')
// value: value | null, // either name OR value
// unit: integer,
// signed: boolean,
// bigendian: boolean
// }
'use strict';
var ints = require('buffer-more-ints');
var debug = (process.env.DEBUG) ?
function(s) { console.log(s); } : function () {};
function parse_int(bin, off, sizeInBytes, bigendian, signed) {
switch (sizeInBytes) {
case 1:
return (signed) ? bin.readInt8(off) : bin.readUInt8(off);
case 2:
return (bigendian) ?
(signed) ? bin.readInt16BE(off) : bin.readUInt16BE(off) :
(signed) ? bin.readInt16LE(off) : bin.readUInt16LE(off);
case 4:
return (bigendian) ?
(signed) ? bin.readInt32BE(off) : bin.readUInt32BE(off) :
(signed) ? bin.readInt32LE(off) : bin.readUInt32LE(off);
case 8:
return (bigendian) ?
((signed) ? ints.readInt64BE : ints.readUInt64BE)(bin, off) :
((signed) ? ints.readInt64LE : ints.readUInt64LE)(bin, off);
default:
throw "Integers must be 8-, 16-, 32- or 64-bit";
}
}
function parse_float(bin, off, sizeInBytes, bigendian) {
switch (sizeInBytes) {
case 4:
return (bigendian) ? bin.readFloatBE(off) : bin.readFloatLE(off);
case 8:
return (bigendian) ? bin.readDoubleBE(off) : bin.readDoubleLE(off);
default:
throw "Floats must be 32- or 64-bit";
}
}
function bcdToInt(buf) {
var r = 0;
var len = (buf.length * 2) - 1;
for (var k = 0; k < buf.length; k++) {
var v = buf[k];
r += (Math.pow(10, len) * (v >> 4)) + (Math.pow(10, (len - 1)) * (v & 15));
len = len - 2;
}
return r;
}
function size_of(segment, bound) {
var size = segment.size;
if (typeof size === 'string') {
return bound[size];
} else {
return size;
}
}
function new_scope(env) {
function scope() {};
scope.prototype = env;
return new scope();
}
function bindings(scope) {
var s = {};
for (var k in scope) {
Eif (scope.hasOwnProperty(k)) {
s[k] = scope[k];
}
}
return s;
}
function match(pattern, binary, boundvars) {
var offset = 0, vars = new_scope(boundvars);
var binsize = binary.length * 8;
function skip_bits(segment) {
debug("skip bits"); debug(segment);
var size = size_of(segment, vars);
Eif (size === null) {
Eif (offset % 8 === 0) {
offset = binsize;
return true;
}
else {
return false;
}
}
var bits = segment.unit * size;
if (offset + bits > binsize) {
return false;
}
else {
offset += bits;
}
}
function get_integer(segment) {
debug("get_integer"); debug(segment);
// let's do only multiples of eight bits for now
var unit = segment.unit, size = size_of(segment, vars);
var bitsize = size * unit;
var byteoffset = offset / 8; // NB assumes aligned
offset += bitsize;
Iif (bitsize % 8 > 0 || (offset > binsize)) {
return false;
}
else {
return parse_int(binary, byteoffset, bitsize / 8,
segment.bigendian, segment.signed);
}
}
function get_float(segment) {
debug("get_float"); debug(segment);
var unit = segment.unit; var size = size_of(segment, vars);
var bitsize = size * unit;
var byteoffset = offset / 8; // assume aligned
offset += bitsize;
Iif (offset > binsize) {
return false;
}
else {
return parse_float(binary, byteoffset,
bitsize / 8, segment.bigendian);
}
}
function get_binary(segment) {
debug("get_binary"); debug(segment);
var unit = segment.unit, size = size_of(segment, vars);
var byteoffset = offset / 8; // NB alignment
Iif (segment.z) {
for (var i = byteoffset; i < binary.length; i++) {
offset += 8;
var segm = binary[i];
if (segm === 0) {
return binary.slice(byteoffset, i);
}
}
return false;
}
Iif (size === null) {
offset = binsize;
return binary.slice(byteoffset);
}
else {
var bitsize = size * unit;
Iif (bitsize % 8 > 0 || (offset + bitsize) > binsize) {
return false;
}
else {
offset += bitsize;
return binary.slice(byteoffset, byteoffset + bitsize / 8);
}
}
}
function get_string(segment) {
debug("get_string"); debug(segment);
var len = segment.value != undefined ? segment.value.length : size_of(segment, vars);
var byteoffset = offset / 8;
Iif (segment.z) {
var strVal = '';
for (var i = byteoffset; i < binary.length; i++) {
offset += 8;
var segm = binary[i];
if (segm === 0) {
return strVal;
break;
}
strVal += String.fromCharCode(segm);
}
return false;
}
offset += len * 8;
Iif (offset > binsize) {
return false;
}
// FIXME bytes vs UTF8 characters
var val = binary.slice(byteoffset, byteoffset + len).toString('utf8');
Iif (segment.hex) {
val = (Buffer.from(val, 'hex')).toString();
} else Iif (segment.binary) {
var regex = new RegExp(/^[01]+$/);
if (!regex.test(val)) {
throw "Invalid binary string value!";
}
var bytesCount = val.length / 8;
var resString = '';
for (var k = 0; k < bytesCount; k++) {
var chrInt = parseInt(val.substr((k * 8), 8), 2);
resString += String.fromCharCode(chrInt);
}
val = resString;
}
return val;
}
function get_bcd(segment) {
debug("get_bcd"); debug(segment);
var len = segment.size;
var byteoffset = offset / 8;
offset += len * 8;
if (offset > binsize) {
return false;
}
var buf = binary.slice(byteoffset, byteoffset + len);
var val = bcdToInt(buf);
return val;
}
var patternlen = pattern.length;
for (var i = 0; i < patternlen; i++) {
var segment = pattern[i];
var result = false;
if (segment.name === '_') {
result = skip_bits(segment);
}
else {
switch (segment.type) {
case 'string':
result = get_string(segment);
break;
case 'integer':
result = get_integer(segment);
break;
case 'float':
result = get_float(segment);
break;
case 'binary':
result = get_binary(segment);
break;
case 'bcd':
result = get_bcd(segment);
break;
}
Iif (result === false) {
return false;
}
else if (segment.name) {
vars[segment.name] = result;
}
else Iif (segment.value != result) {
return false;
}
}
}
Eif (offset == binsize) {
return bindings(vars);
}
else {
return false;
}
}
module.exports.match = match;
module.exports.parse_int = parse_int;
module.exports.parse_float = parse_float;
module.exports.bcdToInt = bcdToInt;
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