/**
* This class uses BinaryXMLDecoder to follow the structure of a ndnb binary element to
* determine its end.
*
* Copyright (C) 2013-2015 Regents of the University of California.
* @author: Jeff Thompson <[email protected]>
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
* A copy of the GNU Lesser General Public License is in the file COPYING.
*/
var BinaryXMLDecoder = require('./binary-xml-decoder.js').BinaryXMLDecoder;
var DynamicBuffer = require('../util/dynamic-buffer.js').DynamicBuffer;
var XML_EXT = 0x00;
var XML_TAG = 0x01;
var XML_DTAG = 0x02;
var XML_ATTR = 0x03;
var XML_DATTR = 0x04;
var XML_BLOB = 0x05;
var XML_UDATA = 0x06;
var XML_CLOSE = 0x0;
var XML_SUBTYPE_PROCESSING_INSTRUCTIONS = 16;
var XML_TT_BITS = 3;
var XML_TT_MASK = ((1 << XML_TT_BITS) - 1);
var XML_TT_VAL_BITS = XML_TT_BITS + 1;
var XML_TT_VAL_MASK = ((1 << (XML_TT_VAL_BITS)) - 1);
var XML_REG_VAL_BITS = 7;
var XML_REG_VAL_MASK = ((1 << XML_REG_VAL_BITS) - 1);
var XML_TT_NO_MORE = (1 << XML_REG_VAL_BITS); // 0x80
/**
* @constructor
*/
var BinaryXMLStructureDecoder = function BinaryXMLDecoder()
{
this.gotElementEnd = false;
this.offset = 0;
this.level = 0;
this.state = BinaryXMLStructureDecoder.READ_HEADER_OR_CLOSE;
this.headerLength = 0;
this.useHeaderBuffer = false;
this.headerBuffer = new DynamicBuffer(5);
this.nBytesToRead = 0;
};
exports.BinaryXMLStructureDecoder = BinaryXMLStructureDecoder;
BinaryXMLStructureDecoder.READ_HEADER_OR_CLOSE = 0;
BinaryXMLStructureDecoder.READ_BYTES = 1;
/**
* Continue scanning input starting from this.offset. If found the end of the element
* which started at offset 0 then return true, else false.
* If this returns false, you should read more into input and call again.
* You have to pass in input each time because the array could be reallocated.
* This throws an exception for badly formed ndnb.
*/
BinaryXMLStructureDecoder.prototype.findElementEnd = function(
// Buffer
input)
{
if (this.gotElementEnd)
// Someone is calling when we already got the end.
return true;
var decoder = new BinaryXMLDecoder(input);
while (true) {
if (this.offset >= input.length)
// All the cases assume we have some input.
return false;
switch (this.state) {
case BinaryXMLStructureDecoder.READ_HEADER_OR_CLOSE:
// First check for XML_CLOSE.
if (this.headerLength == 0 && input[this.offset] == XML_CLOSE) {
++this.offset;
// Close the level.
--this.level;
if (this.level == 0) {
// Finished.
this.gotElementEnd = true;
return true;
}
if (this.level < 0)
throw new Error("BinaryXMLStructureDecoder: Unexpected close tag at offset " + (this.offset - 1));
// Get ready for the next header.
this.startHeader();
break;
}
var startingHeaderLength = this.headerLength;
while (true) {
if (this.offset >= input.length) {
// We can't get all of the header bytes from this input. Save in headerBuffer.
this.useHeaderBuffer = true;
var nNewBytes = this.headerLength - startingHeaderLength;
this.headerBuffer.copy(input.slice(this.offset - nNewBytes, nNewBytes), startingHeaderLength);
return false;
}
var headerByte = input[this.offset++];
++this.headerLength;
if (headerByte & XML_TT_NO_MORE)
// Break and read the header.
break;
}
var typeAndVal;
if (this.useHeaderBuffer) {
// Copy the remaining bytes into headerBuffer.
nNewBytes = this.headerLength - startingHeaderLength;
this.headerBuffer.copy(input.slice(this.offset - nNewBytes, nNewBytes), startingHeaderLength);
typeAndVal = new BinaryXMLDecoder(this.headerBuffer.array).decodeTypeAndVal();
}
else {
// We didn't have to use the headerBuffer.
decoder.seek(this.offset - this.headerLength);
typeAndVal = decoder.decodeTypeAndVal();
}
if (typeAndVal == null)
throw new Error("BinaryXMLStructureDecoder: Can't read header starting at offset " +
(this.offset - this.headerLength));
// Set the next state based on the type.
var type = typeAndVal.t;
if (type == XML_DATTR)
// We already consumed the item. READ_HEADER_OR_CLOSE again.
// ndnb has rules about what must follow an attribute, but we are just scanning.
this.startHeader();
else if (type == XML_DTAG || type == XML_EXT) {
// Start a new level and READ_HEADER_OR_CLOSE again.
++this.level;
this.startHeader();
}
else if (type == XML_TAG || type == XML_ATTR) {
if (type == XML_TAG)
// Start a new level and read the tag.
++this.level;
// Minimum tag or attribute length is 1.
this.nBytesToRead = typeAndVal.v + 1;
this.state = BinaryXMLStructureDecoder.READ_BYTES;
// ndnb has rules about what must follow an attribute, but we are just scanning.
}
else if (type == XML_BLOB || type == XML_UDATA) {
this.nBytesToRead = typeAndVal.v;
this.state = BinaryXMLStructureDecoder.READ_BYTES;
}
else
throw new Error("BinaryXMLStructureDecoder: Unrecognized header type " + type);
break;
case BinaryXMLStructureDecoder.READ_BYTES:
var nRemainingBytes = input.length - this.offset;
if (nRemainingBytes < this.nBytesToRead) {
// Need more.
this.offset += nRemainingBytes;
this.nBytesToRead -= nRemainingBytes;
return false;
}
// Got the bytes. Read a new header or close.
this.offset += this.nBytesToRead;
this.startHeader();
break;
default:
// We don't expect this to happen.
throw new Error("BinaryXMLStructureDecoder: Unrecognized state " + this.state);
}
}
};
/**
* Set the state to READ_HEADER_OR_CLOSE and set up to start reading the header
*/
BinaryXMLStructureDecoder.prototype.startHeader = function()
{
this.headerLength = 0;
this.useHeaderBuffer = false;
this.state = BinaryXMLStructureDecoder.READ_HEADER_OR_CLOSE;
};
/**
* Set the offset into the input, used for the next read.
*/
BinaryXMLStructureDecoder.prototype.seek = function(offset)
{
this.offset = offset;
};