398 lines
10 KiB
JavaScript
398 lines
10 KiB
JavaScript
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var Chainsaw = require('chainsaw');
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var EventEmitter = require('events').EventEmitter;
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var Buffers = require('buffers');
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var Vars = require('./lib/vars.js');
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var Stream = require('stream').Stream;
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exports = module.exports = function (bufOrEm, eventName) {
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if (Buffer.isBuffer(bufOrEm)) {
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return exports.parse(bufOrEm);
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}
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var s = exports.stream();
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if (bufOrEm && bufOrEm.pipe) {
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bufOrEm.pipe(s);
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}
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else if (bufOrEm) {
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bufOrEm.on(eventName || 'data', function (buf) {
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s.write(buf);
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});
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bufOrEm.on('end', function () {
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s.end();
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});
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}
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return s;
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};
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exports.stream = function (input) {
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if (input) return exports.apply(null, arguments);
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var pending = null;
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function getBytes (bytes, cb, skip) {
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pending = {
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bytes : bytes,
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skip : skip,
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cb : function (buf) {
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pending = null;
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cb(buf);
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},
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};
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dispatch();
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}
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var offset = null;
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function dispatch () {
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if (!pending) {
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if (caughtEnd) done = true;
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return;
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}
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if (typeof pending === 'function') {
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pending();
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}
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else {
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var bytes = offset + pending.bytes;
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if (buffers.length >= bytes) {
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var buf;
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if (offset == null) {
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buf = buffers.splice(0, bytes);
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if (!pending.skip) {
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buf = buf.slice();
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}
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}
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else {
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if (!pending.skip) {
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buf = buffers.slice(offset, bytes);
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}
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offset = bytes;
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}
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if (pending.skip) {
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pending.cb();
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}
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else {
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pending.cb(buf);
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}
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}
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}
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}
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function builder (saw) {
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function next () { if (!done) saw.next() }
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var self = words(function (bytes, cb) {
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return function (name) {
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getBytes(bytes, function (buf) {
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vars.set(name, cb(buf));
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next();
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});
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};
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});
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self.tap = function (cb) {
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saw.nest(cb, vars.store);
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};
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self.into = function (key, cb) {
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if (!vars.get(key)) vars.set(key, {});
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var parent = vars;
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vars = Vars(parent.get(key));
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saw.nest(function () {
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cb.apply(this, arguments);
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this.tap(function () {
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vars = parent;
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});
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}, vars.store);
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};
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self.flush = function () {
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vars.store = {};
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next();
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};
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self.loop = function (cb) {
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var end = false;
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saw.nest(false, function loop () {
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this.vars = vars.store;
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cb.call(this, function () {
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end = true;
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next();
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}, vars.store);
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this.tap(function () {
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if (end) saw.next()
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else loop.call(this)
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}.bind(this));
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}, vars.store);
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};
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self.buffer = function (name, bytes) {
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if (typeof bytes === 'string') {
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bytes = vars.get(bytes);
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}
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getBytes(bytes, function (buf) {
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vars.set(name, buf);
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next();
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});
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};
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self.skip = function (bytes) {
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if (typeof bytes === 'string') {
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bytes = vars.get(bytes);
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}
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getBytes(bytes, function () {
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next();
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});
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};
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self.scan = function find (name, search) {
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if (typeof search === 'string') {
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search = new Buffer(search);
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}
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else if (!Buffer.isBuffer(search)) {
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throw new Error('search must be a Buffer or a string');
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}
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var taken = 0;
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pending = function () {
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var pos = buffers.indexOf(search, offset + taken);
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var i = pos-offset-taken;
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if (pos !== -1) {
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pending = null;
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if (offset != null) {
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vars.set(
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name,
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buffers.slice(offset, offset + taken + i)
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);
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offset += taken + i + search.length;
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}
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else {
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vars.set(
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name,
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buffers.slice(0, taken + i)
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);
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buffers.splice(0, taken + i + search.length);
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}
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next();
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dispatch();
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} else {
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i = Math.max(buffers.length - search.length - offset - taken, 0);
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}
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taken += i;
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};
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dispatch();
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};
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self.peek = function (cb) {
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offset = 0;
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saw.nest(function () {
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cb.call(this, vars.store);
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this.tap(function () {
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offset = null;
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});
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});
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};
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return self;
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};
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var stream = Chainsaw.light(builder);
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stream.writable = true;
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var buffers = Buffers();
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stream.write = function (buf) {
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buffers.push(buf);
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dispatch();
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};
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var vars = Vars();
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var done = false, caughtEnd = false;
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stream.end = function () {
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caughtEnd = true;
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};
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stream.pipe = Stream.prototype.pipe;
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Object.getOwnPropertyNames(EventEmitter.prototype).forEach(function (name) {
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stream[name] = EventEmitter.prototype[name];
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});
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return stream;
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};
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exports.parse = function parse (buffer) {
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var self = words(function (bytes, cb) {
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return function (name) {
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if (offset + bytes <= buffer.length) {
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var buf = buffer.slice(offset, offset + bytes);
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offset += bytes;
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vars.set(name, cb(buf));
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}
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else {
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vars.set(name, null);
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}
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return self;
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};
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});
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var offset = 0;
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var vars = Vars();
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self.vars = vars.store;
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self.tap = function (cb) {
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cb.call(self, vars.store);
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return self;
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};
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self.into = function (key, cb) {
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if (!vars.get(key)) {
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vars.set(key, {});
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}
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var parent = vars;
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vars = Vars(parent.get(key));
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cb.call(self, vars.store);
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vars = parent;
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return self;
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};
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self.loop = function (cb) {
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var end = false;
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var ender = function () { end = true };
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while (end === false) {
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cb.call(self, ender, vars.store);
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}
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return self;
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};
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self.buffer = function (name, size) {
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if (typeof size === 'string') {
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size = vars.get(size);
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}
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var buf = buffer.slice(offset, Math.min(buffer.length, offset + size));
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offset += size;
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vars.set(name, buf);
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return self;
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};
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self.skip = function (bytes) {
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if (typeof bytes === 'string') {
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bytes = vars.get(bytes);
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}
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offset += bytes;
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return self;
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};
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self.scan = function (name, search) {
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if (typeof search === 'string') {
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search = new Buffer(search);
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}
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else if (!Buffer.isBuffer(search)) {
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throw new Error('search must be a Buffer or a string');
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}
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vars.set(name, null);
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// simple but slow string search
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for (var i = 0; i + offset <= buffer.length - search.length + 1; i++) {
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for (
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var j = 0;
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j < search.length && buffer[offset+i+j] === search[j];
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j++
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);
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if (j === search.length) break;
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}
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vars.set(name, buffer.slice(offset, offset + i));
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offset += i + search.length;
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return self;
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};
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self.peek = function (cb) {
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var was = offset;
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cb.call(self, vars.store);
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offset = was;
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return self;
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};
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self.flush = function () {
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vars.store = {};
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return self;
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};
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self.eof = function () {
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return offset >= buffer.length;
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};
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return self;
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};
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// convert byte strings to unsigned little endian numbers
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function decodeLEu (bytes) {
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var acc = 0;
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for (var i = 0; i < bytes.length; i++) {
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acc += Math.pow(256,i) * bytes[i];
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}
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return acc;
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}
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// convert byte strings to unsigned big endian numbers
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function decodeBEu (bytes) {
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var acc = 0;
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for (var i = 0; i < bytes.length; i++) {
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acc += Math.pow(256, bytes.length - i - 1) * bytes[i];
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}
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return acc;
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}
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// convert byte strings to signed big endian numbers
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function decodeBEs (bytes) {
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var val = decodeBEu(bytes);
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if ((bytes[0] & 0x80) == 0x80) {
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val -= Math.pow(256, bytes.length);
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}
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return val;
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}
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// convert byte strings to signed little endian numbers
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function decodeLEs (bytes) {
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var val = decodeLEu(bytes);
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if ((bytes[bytes.length - 1] & 0x80) == 0x80) {
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val -= Math.pow(256, bytes.length);
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}
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return val;
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}
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function words (decode) {
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var self = {};
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[ 1, 2, 4, 8 ].forEach(function (bytes) {
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var bits = bytes * 8;
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self['word' + bits + 'le']
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= self['word' + bits + 'lu']
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= decode(bytes, decodeLEu);
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self['word' + bits + 'ls']
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= decode(bytes, decodeLEs);
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self['word' + bits + 'be']
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= self['word' + bits + 'bu']
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= decode(bytes, decodeBEu);
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self['word' + bits + 'bs']
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= decode(bytes, decodeBEs);
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});
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// word8be(n) == word8le(n) for all n
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self.word8 = self.word8u = self.word8be;
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self.word8s = self.word8bs;
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return self;
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}
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