Current File : //lib/node_modules/npm/node_modules/asn1/lib/ber/reader.js
// Copyright 2011 Mark Cavage <mcavage@gmail.com> All rights reserved.
var assert = require('assert');
var Buffer = require('safer-buffer').Buffer;
var ASN1 = require('./types');
var errors = require('./errors');
// --- Globals
var newInvalidAsn1Error = errors.newInvalidAsn1Error;
// --- API
function Reader(data) {
if (!data || !Buffer.isBuffer(data))
throw new TypeError('data must be a node Buffer');
this._buf = data;
this._size = data.length;
// These hold the "current" state
this._len = 0;
this._offset = 0;
}
Object.defineProperty(Reader.prototype, 'length', {
enumerable: true,
get: function () { return (this._len); }
});
Object.defineProperty(Reader.prototype, 'offset', {
enumerable: true,
get: function () { return (this._offset); }
});
Object.defineProperty(Reader.prototype, 'remain', {
get: function () { return (this._size - this._offset); }
});
Object.defineProperty(Reader.prototype, 'buffer', {
get: function () { return (this._buf.slice(this._offset)); }
});
/**
* Reads a single byte and advances offset; you can pass in `true` to make this
* a "peek" operation (i.e., get the byte, but don't advance the offset).
*
* @param {Boolean} peek true means don't move offset.
* @return {Number} the next byte, null if not enough data.
*/
Reader.prototype.readByte = function (peek) {
if (this._size - this._offset < 1)
return null;
var b = this._buf[this._offset] & 0xff;
if (!peek)
this._offset += 1;
return b;
};
Reader.prototype.peek = function () {
return this.readByte(true);
};
/**
* Reads a (potentially) variable length off the BER buffer. This call is
* not really meant to be called directly, as callers have to manipulate
* the internal buffer afterwards.
*
* As a result of this call, you can call `Reader.length`, until the
* next thing called that does a readLength.
*
* @return {Number} the amount of offset to advance the buffer.
* @throws {InvalidAsn1Error} on bad ASN.1
*/
Reader.prototype.readLength = function (offset) {
if (offset === undefined)
offset = this._offset;
if (offset >= this._size)
return null;
var lenB = this._buf[offset++] & 0xff;
if (lenB === null)
return null;
if ((lenB & 0x80) === 0x80) {
lenB &= 0x7f;
if (lenB === 0)
throw newInvalidAsn1Error('Indefinite length not supported');
if (lenB > 4)
throw newInvalidAsn1Error('encoding too long');
if (this._size - offset < lenB)
return null;
this._len = 0;
for (var i = 0; i < lenB; i++)
this._len = (this._len << 8) + (this._buf[offset++] & 0xff);
} else {
// Wasn't a variable length
this._len = lenB;
}
return offset;
};
/**
* Parses the next sequence in this BER buffer.
*
* To get the length of the sequence, call `Reader.length`.
*
* @return {Number} the sequence's tag.
*/
Reader.prototype.readSequence = function (tag) {
var seq = this.peek();
if (seq === null)
return null;
if (tag !== undefined && tag !== seq)
throw newInvalidAsn1Error('Expected 0x' + tag.toString(16) +
': got 0x' + seq.toString(16));
var o = this.readLength(this._offset + 1); // stored in `length`
if (o === null)
return null;
this._offset = o;
return seq;
};
Reader.prototype.readInt = function () {
return this._readTag(ASN1.Integer);
};
Reader.prototype.readBoolean = function () {
return (this._readTag(ASN1.Boolean) === 0 ? false : true);
};
Reader.prototype.readEnumeration = function () {
return this._readTag(ASN1.Enumeration);
};
Reader.prototype.readString = function (tag, retbuf) {
if (!tag)
tag = ASN1.OctetString;
var b = this.peek();
if (b === null)
return null;
if (b !== tag)
throw newInvalidAsn1Error('Expected 0x' + tag.toString(16) +
': got 0x' + b.toString(16));
var o = this.readLength(this._offset + 1); // stored in `length`
if (o === null)
return null;
if (this.length > this._size - o)
return null;
this._offset = o;
if (this.length === 0)
return retbuf ? Buffer.alloc(0) : '';
var str = this._buf.slice(this._offset, this._offset + this.length);
this._offset += this.length;
return retbuf ? str : str.toString('utf8');
};
Reader.prototype.readOID = function (tag) {
if (!tag)
tag = ASN1.OID;
var b = this.readString(tag, true);
if (b === null)
return null;
var values = [];
var value = 0;
for (var i = 0; i < b.length; i++) {
var byte = b[i] & 0xff;
value <<= 7;
value += byte & 0x7f;
if ((byte & 0x80) === 0) {
values.push(value);
value = 0;
}
}
value = values.shift();
values.unshift(value % 40);
values.unshift((value / 40) >> 0);
return values.join('.');
};
Reader.prototype._readTag = function (tag) {
assert.ok(tag !== undefined);
var b = this.peek();
if (b === null)
return null;
if (b !== tag)
throw newInvalidAsn1Error('Expected 0x' + tag.toString(16) +
': got 0x' + b.toString(16));
var o = this.readLength(this._offset + 1); // stored in `length`
if (o === null)
return null;
if (this.length > 4)
throw newInvalidAsn1Error('Integer too long: ' + this.length);
if (this.length > this._size - o)
return null;
this._offset = o;
var fb = this._buf[this._offset];
var value = 0;
for (var i = 0; i < this.length; i++) {
value <<= 8;
value |= (this._buf[this._offset++] & 0xff);
}
if ((fb & 0x80) === 0x80 && i !== 4)
value -= (1 << (i * 8));
return value >> 0;
};
// --- Exported API
module.exports = Reader;
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