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117 lines
3.6 KiB
117 lines
3.6 KiB
"use strict";
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var utils = require("../utils");
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function DataReader(data) {
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this.data = data; // type : see implementation
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this.length = data.length;
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this.index = 0;
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this.zero = 0;
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}
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DataReader.prototype = {
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/**
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* Check that the offset will not go too far.
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* @param {string} offset the additional offset to check.
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* @throws {Error} an Error if the offset is out of bounds.
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*/
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checkOffset: function(offset) {
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this.checkIndex(this.index + offset);
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},
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/**
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* Check that the specified index will not be too far.
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* @param {string} newIndex the index to check.
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* @throws {Error} an Error if the index is out of bounds.
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*/
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checkIndex: function(newIndex) {
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if (this.length < this.zero + newIndex || newIndex < 0) {
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throw new Error("End of data reached (data length = " + this.length + ", asked index = " + (newIndex) + "). Corrupted zip ?");
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}
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},
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/**
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* Change the index.
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* @param {number} newIndex The new index.
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* @throws {Error} if the new index is out of the data.
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*/
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setIndex: function(newIndex) {
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this.checkIndex(newIndex);
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this.index = newIndex;
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},
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/**
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* Skip the next n bytes.
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* @param {number} n the number of bytes to skip.
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* @throws {Error} if the new index is out of the data.
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*/
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skip: function(n) {
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this.setIndex(this.index + n);
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},
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/**
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* Get the byte at the specified index.
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* @param {number} i the index to use.
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* @return {number} a byte.
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*/
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byteAt: function() {
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// see implementations
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},
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/**
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* Get the next number with a given byte size.
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* @param {number} size the number of bytes to read.
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* @return {number} the corresponding number.
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*/
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readInt: function(size) {
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var result = 0,
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i;
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this.checkOffset(size);
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for (i = this.index + size - 1; i >= this.index; i--) {
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result = (result << 8) + this.byteAt(i);
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}
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this.index += size;
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return result;
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},
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/**
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* Get the next string with a given byte size.
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* @param {number} size the number of bytes to read.
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* @return {string} the corresponding string.
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*/
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readString: function(size) {
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return utils.transformTo("string", this.readData(size));
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},
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/**
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* Get raw data without conversion, <size> bytes.
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* @param {number} size the number of bytes to read.
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* @return {Object} the raw data, implementation specific.
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*/
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readData: function() {
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// see implementations
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},
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/**
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* Find the last occurrence of a zip signature (4 bytes).
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* @param {string} sig the signature to find.
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* @return {number} the index of the last occurrence, -1 if not found.
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*/
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lastIndexOfSignature: function() {
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// see implementations
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},
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/**
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* Read the signature (4 bytes) at the current position and compare it with sig.
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* @param {string} sig the expected signature
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* @return {boolean} true if the signature matches, false otherwise.
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*/
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readAndCheckSignature: function() {
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// see implementations
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},
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/**
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* Get the next date.
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* @return {Date} the date.
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*/
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readDate: function() {
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var dostime = this.readInt(4);
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return new Date(Date.UTC(
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((dostime >> 25) & 0x7f) + 1980, // year
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((dostime >> 21) & 0x0f) - 1, // month
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(dostime >> 16) & 0x1f, // day
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(dostime >> 11) & 0x1f, // hour
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(dostime >> 5) & 0x3f, // minute
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(dostime & 0x1f) << 1)); // second
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}
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};
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module.exports = DataReader;
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