@cantoo/pdf-lib
Version:
Create and modify PDF files with JavaScript
142 lines • 4.34 kB
JavaScript
"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
const tslib_1 = require("tslib");
const errors_1 = require("../errors");
const Stream_1 = tslib_1.__importDefault(require("./Stream"));
/*
* Copyright 2012 Mozilla Foundation
*
* The DecodeStream class contained in this file is a TypeScript port of the
* JavaScript DecodeStream class in Mozilla's pdf.js project, made available
* under the Apache 2.0 open source license.
*/
// Lots of DecodeStreams are created whose buffers are never used. For these
// we share a single empty buffer. This is (a) space-efficient and (b) avoids
// having special cases that would be required if we used |null| for an empty
// buffer.
const emptyBuffer = new Uint8Array(0);
/**
* Super class for the decoding streams
*/
class DecodeStream {
constructor(maybeMinBufferLength) {
this.pos = 0;
this.bufferLength = 0;
this.eof = false;
this.buffer = emptyBuffer;
this.minBufferLength = 512;
if (maybeMinBufferLength) {
// Compute the first power of two that is as big as maybeMinBufferLength.
while (this.minBufferLength < maybeMinBufferLength) {
this.minBufferLength *= 2;
}
}
}
get isEmpty() {
while (!this.eof && this.bufferLength === 0) {
this.readBlock();
}
return this.bufferLength === 0;
}
getByte() {
const pos = this.pos;
while (this.bufferLength <= pos) {
if (this.eof) {
return -1;
}
this.readBlock();
}
return this.buffer[this.pos++];
}
getUint16() {
const b0 = this.getByte();
const b1 = this.getByte();
if (b0 === -1 || b1 === -1) {
return -1;
}
return (b0 << 8) + b1;
}
getInt32() {
const b0 = this.getByte();
const b1 = this.getByte();
const b2 = this.getByte();
const b3 = this.getByte();
return (b0 << 24) + (b1 << 16) + (b2 << 8) + b3;
}
getBytes(length, forceClamped = false) {
let end;
const pos = this.pos;
if (length) {
this.ensureBuffer(pos + length);
end = pos + length;
while (!this.eof && this.bufferLength < end) {
this.readBlock();
}
const bufEnd = this.bufferLength;
if (end > bufEnd) {
end = bufEnd;
}
}
else {
while (!this.eof) {
this.readBlock();
}
end = this.bufferLength;
}
this.pos = end;
const subarray = this.buffer.subarray(pos, end);
// `this.buffer` is either a `Uint8Array` or `Uint8ClampedArray` here.
return forceClamped && !(subarray instanceof Uint8ClampedArray)
? new Uint8ClampedArray(subarray)
: subarray;
}
peekByte() {
const peekedByte = this.getByte();
this.pos--;
return peekedByte;
}
peekBytes(length, forceClamped = false) {
const bytes = this.getBytes(length, forceClamped);
this.pos -= bytes.length;
return bytes;
}
skip(n) {
if (!n) {
n = 1;
}
this.pos += n;
}
reset() {
this.pos = 0;
}
makeSubStream(start, length /* dict */) {
const end = start + length;
while (this.bufferLength <= end && !this.eof) {
this.readBlock();
}
return new Stream_1.default(this.buffer, start, length /* dict */);
}
decode() {
while (!this.eof)
this.readBlock();
return this.buffer.subarray(0, this.bufferLength);
}
readBlock() {
throw new errors_1.MethodNotImplementedError(this.constructor.name, 'readBlock');
}
ensureBuffer(requested) {
const buffer = this.buffer;
if (requested <= buffer.byteLength) {
return buffer;
}
let size = this.minBufferLength;
while (size < requested) {
size *= 2;
}
const buffer2 = new Uint8Array(size);
buffer2.set(buffer);
return (this.buffer = buffer2);
}
}
exports.default = DecodeStream;
//# sourceMappingURL=DecodeStream.js.map