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