CasperSecurity
const { isReadableStream } = require('./utils');
const TextDecoder = require('./text-decoder');
const STACK_OBJECT = 1;
const STACK_ARRAY = 2;
const decoder = new TextDecoder();
function isObject(value) {
return value !== null && typeof value === 'object';
}
function adjustPosition(error, parser) {
if (error.name === 'SyntaxError' && parser.jsonParseOffset) {
error.message = error.message.replace(/at position (\d+)/, (_, pos) =>
'at position ' + (Number(pos) + parser.jsonParseOffset)
);
}
return error;
}
function append(array, elements) {
// Note: Avoid to use array.push(...elements) since it may lead to
// "RangeError: Maximum call stack size exceeded" for a long arrays
const initialLength = array.length;
array.length += elements.length;
for (let i = 0; i < elements.length; i++) {
array[initialLength + i] = elements[i];
}
}
module.exports = function(chunkEmitter) {
let parser = new ChunkParser();
if (isObject(chunkEmitter) && isReadableStream(chunkEmitter)) {
return new Promise((resolve, reject) => {
chunkEmitter
.on('data', chunk => {
try {
parser.push(chunk);
} catch (e) {
reject(adjustPosition(e, parser));
parser = null;
}
})
.on('error', (e) => {
parser = null;
reject(e);
})
.on('end', () => {
try {
resolve(parser.finish());
} catch (e) {
reject(adjustPosition(e, parser));
} finally {
parser = null;
}
});
});
}
if (typeof chunkEmitter === 'function') {
const iterator = chunkEmitter();
if (isObject(iterator) && (Symbol.iterator in iterator || Symbol.asyncIterator in iterator)) {
return new Promise(async (resolve, reject) => {
try {
for await (const chunk of iterator) {
parser.push(chunk);
}
resolve(parser.finish());
} catch (e) {
reject(adjustPosition(e, parser));
} finally {
parser = null;
}
});
}
}
throw new Error(
'Chunk emitter should be readable stream, generator, ' +
'async generator or function returning an iterable object'
);
};
class ChunkParser {
constructor() {
this.value = undefined;
this.valueStack = null;
this.stack = new Array(100);
this.lastFlushDepth = 0;
this.flushDepth = 0;
this.stateString = false;
this.stateStringEscape = false;
this.pendingByteSeq = null;
this.pendingChunk = null;
this.chunkOffset = 0;
this.jsonParseOffset = 0;
}
parseAndAppend(fragment, wrap) {
// Append new entries or elements
if (this.stack[this.lastFlushDepth - 1] === STACK_OBJECT) {
if (wrap) {
this.jsonParseOffset--;
fragment = '{' + fragment + '}';
}
Object.assign(this.valueStack.value, JSON.parse(fragment));
} else {
if (wrap) {
this.jsonParseOffset--;
fragment = '[' + fragment + ']';
}
append(this.valueStack.value, JSON.parse(fragment));
}
}
prepareAddition(fragment) {
const { value } = this.valueStack;
const expectComma = Array.isArray(value)
? value.length !== 0
: Object.keys(value).length !== 0;
if (expectComma) {
// Skip a comma at the beginning of fragment, otherwise it would
// fail to parse
if (fragment[0] === ',') {
this.jsonParseOffset++;
return fragment.slice(1);
}
// When value (an object or array) is not empty and a fragment
// doesn't start with a comma, a single valid fragment starting
// is a closing bracket. If it's not, a prefix is adding to fail
// parsing. Otherwise, the sequence of chunks can be successfully
// parsed, although it should not, e.g. ["[{}", "{}]"]
if (fragment[0] !== '}' && fragment[0] !== ']') {
this.jsonParseOffset -= 3;
return '[[]' + fragment;
}
}
return fragment;
}
flush(chunk, start, end) {
let fragment = chunk.slice(start, end);
// Save position correction an error in JSON.parse() if any
this.jsonParseOffset = this.chunkOffset + start;
// Prepend pending chunk if any
if (this.pendingChunk !== null) {
fragment = this.pendingChunk + fragment;
this.jsonParseOffset -= this.pendingChunk.length;
this.pendingChunk = null;
}
if (this.flushDepth === this.lastFlushDepth) {
// Depth didn't changed, so it's a root value or entry/element set
if (this.flushDepth > 0) {
this.parseAndAppend(this.prepareAddition(fragment), true);
} else {
// That's an entire value on a top level
this.value = JSON.parse(fragment);
this.valueStack = {
value: this.value,
prev: null
};
}
} else if (this.flushDepth > this.lastFlushDepth) {
// Add missed closing brackets/parentheses
for (let i = this.flushDepth - 1; i >= this.lastFlushDepth; i--) {
fragment += this.stack[i] === STACK_OBJECT ? '}' : ']';
}
if (this.lastFlushDepth === 0) {
// That's a root value
this.value = JSON.parse(fragment);
this.valueStack = {
value: this.value,
prev: null
};
} else {
this.parseAndAppend(this.prepareAddition(fragment), true);
}
// Move down to the depths to the last object/array, which is current now
for (let i = this.lastFlushDepth || 1; i < this.flushDepth; i++) {
let value = this.valueStack.value;
if (this.stack[i - 1] === STACK_OBJECT) {
// find last entry
let key;
// eslint-disable-next-line curly
for (key in value);
value = value[key];
} else {
// last element
value = value[value.length - 1];
}
this.valueStack = {
value,
prev: this.valueStack
};
}
} else /* this.flushDepth < this.lastFlushDepth */ {
fragment = this.prepareAddition(fragment);
// Add missed opening brackets/parentheses
for (let i = this.lastFlushDepth - 1; i >= this.flushDepth; i--) {
this.jsonParseOffset--;
fragment = (this.stack[i] === STACK_OBJECT ? '{' : '[') + fragment;
}
this.parseAndAppend(fragment, false);
for (let i = this.lastFlushDepth - 1; i >= this.flushDepth; i--) {
this.valueStack = this.valueStack.prev;
}
}
this.lastFlushDepth = this.flushDepth;
}
push(chunk) {
if (typeof chunk !== 'string') {
// Suppose chunk is Buffer or Uint8Array
// Prepend uncompleted byte sequence if any
if (this.pendingByteSeq !== null) {
const origRawChunk = chunk;
chunk = new Uint8Array(this.pendingByteSeq.length + origRawChunk.length);
chunk.set(this.pendingByteSeq);
chunk.set(origRawChunk, this.pendingByteSeq.length);
this.pendingByteSeq = null;
}
// In case Buffer/Uint8Array, an input is encoded in UTF8
// Seek for parts of uncompleted UTF8 symbol on the ending
// This makes sense only if we expect more chunks and last char is not multi-bytes
if (chunk[chunk.length - 1] > 127) {
for (let seqLength = 0; seqLength < chunk.length; seqLength++) {
const byte = chunk[chunk.length - 1 - seqLength];
// 10xxxxxx - 2nd, 3rd or 4th byte
// 110xxxxx – first byte of 2-byte sequence
// 1110xxxx - first byte of 3-byte sequence
// 11110xxx - first byte of 4-byte sequence
if (byte >> 6 === 3) {
seqLength++;
// If the sequence is really incomplete, then preserve it
// for the future chunk and cut off it from the current chunk
if ((seqLength !== 4 && byte >> 3 === 0b11110) ||
(seqLength !== 3 && byte >> 4 === 0b1110) ||
(seqLength !== 2 && byte >> 5 === 0b110)) {
this.pendingByteSeq = chunk.slice(chunk.length - seqLength);
chunk = chunk.slice(0, -seqLength);
}
break;
}
}
}
// Convert chunk to a string, since single decode per chunk
// is much effective than decode multiple small substrings
chunk = decoder.decode(chunk);
}
const chunkLength = chunk.length;
let lastFlushPoint = 0;
let flushPoint = 0;
// Main scan loop
scan: for (let i = 0; i < chunkLength; i++) {
if (this.stateString) {
for (; i < chunkLength; i++) {
if (this.stateStringEscape) {
this.stateStringEscape = false;
} else {
switch (chunk.charCodeAt(i)) {
case 0x22: /* " */
this.stateString = false;
continue scan;
case 0x5C: /* \ */
this.stateStringEscape = true;
}
}
}
break;
}
switch (chunk.charCodeAt(i)) {
case 0x22: /* " */
this.stateString = true;
this.stateStringEscape = false;
break;
case 0x2C: /* , */
flushPoint = i;
break;
case 0x7B: /* { */
// Open an object
flushPoint = i + 1;
this.stack[this.flushDepth++] = STACK_OBJECT;
break;
case 0x5B: /* [ */
// Open an array
flushPoint = i + 1;
this.stack[this.flushDepth++] = STACK_ARRAY;
break;
case 0x5D: /* ] */
case 0x7D: /* } */
// Close an object or array
flushPoint = i + 1;
this.flushDepth--;
if (this.flushDepth < this.lastFlushDepth) {
this.flush(chunk, lastFlushPoint, flushPoint);
lastFlushPoint = flushPoint;
}
break;
case 0x09: /* \t */
case 0x0A: /* \n */
case 0x0D: /* \r */
case 0x20: /* space */
// Move points forward when they points on current position and it's a whitespace
if (lastFlushPoint === i) {
lastFlushPoint++;
}
if (flushPoint === i) {
flushPoint++;
}
break;
}
}
if (flushPoint > lastFlushPoint) {
this.flush(chunk, lastFlushPoint, flushPoint);
}
// Produce pendingChunk if something left
if (flushPoint < chunkLength) {
if (this.pendingChunk !== null) {
// When there is already a pending chunk then no flush happened,
// appending entire chunk to pending one
this.pendingChunk += chunk;
} else {
// Create a pending chunk, it will start with non-whitespace since
// flushPoint was moved forward away from whitespaces on scan
this.pendingChunk = chunk.slice(flushPoint, chunkLength);
}
}
this.chunkOffset += chunkLength;
}
finish() {
if (this.pendingChunk !== null) {
this.flush('', 0, 0);
this.pendingChunk = null;
}
return this.value;
}
};