pdf-lib
Version:
Create and modify PDF files with JavaScript
53 lines • 2.06 kB
JavaScript
/*
* Copyright 2012 Mozilla Foundation
*
* The RunLengthStream class contained in this file is a TypeScript port of the
* JavaScript RunLengthStream class in Mozilla's pdf.js project, made available
* under the Apache 2.0 open source license.
*/
import { __extends } from "tslib";
import DecodeStream from "./DecodeStream";
var RunLengthStream = /** @class */ (function (_super) {
__extends(RunLengthStream, _super);
function RunLengthStream(stream, maybeLength) {
var _this = _super.call(this, maybeLength) || this;
_this.stream = stream;
return _this;
}
RunLengthStream.prototype.readBlock = function () {
// The repeatHeader has following format. The first byte defines type of run
// and amount of bytes to repeat/copy: n = 0 through 127 - copy next n bytes
// (in addition to the second byte from the header), n = 129 through 255 -
// duplicate the second byte from the header (257 - n) times, n = 128 - end.
var repeatHeader = this.stream.getBytes(2);
if (!repeatHeader || repeatHeader.length < 2 || repeatHeader[0] === 128) {
this.eof = true;
return;
}
var buffer;
var bufferLength = this.bufferLength;
var n = repeatHeader[0];
if (n < 128) {
// copy n bytes
buffer = this.ensureBuffer(bufferLength + n + 1);
buffer[bufferLength++] = repeatHeader[1];
if (n > 0) {
var source = this.stream.getBytes(n);
buffer.set(source, bufferLength);
bufferLength += n;
}
}
else {
n = 257 - n;
var b = repeatHeader[1];
buffer = this.ensureBuffer(bufferLength + n + 1);
for (var i = 0; i < n; i++) {
buffer[bufferLength++] = b;
}
}
this.bufferLength = bufferLength;
};
return RunLengthStream;
}(DecodeStream));
export default RunLengthStream;
//# sourceMappingURL=RunLengthStream.js.map