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09a9a7bd0b
This is an old API-parameter that is now unused within the PDF.js project itself, and its description says that it's (partly) being used for "range requests operations".
Note that the `length` API-parameter is used to set the *initial* `contentLength` in various `BasePDFStreamReader` implementations, however it's always overridden by the "Content-Length" header (sent by the server) when that one exists *and* is a valid number. While we currently fallback to the keep the initial `contentLength` otherwise, note however how in that case range requests will always be *disabled* and thus the only spot in the code-base [where `fullReader.contentLength` is necessary](873378b718/src/core/worker.js (L230-L236)) cannot actually be reached.
Hence the only possible reason to use the `length` API-parameter would be for improved progress reporting[1] during streaming of PDF data in rare cases where the "Content-Length" header is missing/invalid, but the user *somehow* has information from another source about the correct `length` of the PDF document.
That situation feels very much like an edge-case, but it's obviously impossible to know if someone is depending on it. However, please note that there's a work-around available for users affected by this removal:
- Implement a `PDFDataRangeTransport` instance together with custom data-fetching[2], since in that case its `length`-parameter will always be used as-is.
Finally, updates various `BasePDFStreamReader` implementations to only set the `_isRangeSupported` field once the headers are available (since previously we'd just overwrite the "initial" value anyway).
---
[1] I.e. to avoid the "indeterminate" loadingBar being displayed in the viewer.
[2] This is what e.g. the Firefox PDF Viewer uses.
122 lines
3.3 KiB
JavaScript
122 lines
3.3 KiB
JavaScript
/* Copyright 2012 Mozilla Foundation
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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import { assert, ResponseException } from "../shared/util.js";
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import { getFilenameFromContentDispositionHeader } from "./content_disposition.js";
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import { isPdfFile } from "./display_utils.js";
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function createHeaders(isHttp, httpHeaders) {
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const headers = new Headers();
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if (!isHttp || !httpHeaders || typeof httpHeaders !== "object") {
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return headers;
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}
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for (const key in httpHeaders) {
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const val = httpHeaders[key];
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if (val !== undefined) {
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headers.append(key, val);
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}
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}
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return headers;
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}
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function getResponseOrigin(url) {
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// Notably, null is distinct from "null" string (e.g. from file:-URLs).
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return URL.parse(url)?.origin ?? null;
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}
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function validateRangeRequestCapabilities({
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responseHeaders,
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isHttp,
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rangeChunkSize,
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disableRange,
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}) {
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if (typeof PDFJSDev === "undefined" || PDFJSDev.test("TESTING")) {
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assert(
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Number.isInteger(rangeChunkSize) && rangeChunkSize > 0,
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"rangeChunkSize must be an integer larger than zero."
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);
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}
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const rv = {
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contentLength: 0,
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isRangeSupported: false,
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};
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const length = parseInt(responseHeaders.get("Content-Length"), 10);
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if (!Number.isInteger(length)) {
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return rv;
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}
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rv.contentLength = length;
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if (length <= 2 * rangeChunkSize) {
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// The file size is smaller than the size of two chunks, so it does not
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// make any sense to abort the request and retry with a range request.
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return rv;
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}
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if (disableRange || !isHttp) {
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return rv;
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}
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if (responseHeaders.get("Accept-Ranges") !== "bytes") {
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return rv;
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}
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const contentEncoding = responseHeaders.get("Content-Encoding") || "identity";
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if (contentEncoding === "identity") {
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rv.isRangeSupported = true;
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}
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return rv;
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}
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function extractFilenameFromHeader(responseHeaders) {
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const contentDisposition = responseHeaders.get("Content-Disposition");
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if (contentDisposition) {
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let filename = getFilenameFromContentDispositionHeader(contentDisposition);
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if (filename.includes("%")) {
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try {
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filename = decodeURIComponent(filename);
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} catch {}
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}
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if (isPdfFile(filename)) {
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return filename;
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}
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}
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return null;
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}
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function createResponseError(status, url) {
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return new ResponseException(
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`Unexpected server response (${status}) while retrieving PDF "${url.href}".`,
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status,
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/* missing = */ status === 404 || (status === 0 && url.protocol === "file:")
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);
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}
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function ensureResponseOrigin(rangeOrigin, origin) {
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if (rangeOrigin !== origin) {
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throw new Error(
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`Expected range response-origin "${rangeOrigin}" to match "${origin}".`
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);
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}
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}
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export {
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createHeaders,
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createResponseError,
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ensureResponseOrigin,
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extractFilenameFromHeader,
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getResponseOrigin,
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validateRangeRequestCapabilities,
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};
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