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956cacaef7
[misc] add split test for a per request pdfCachingMinChunkSize GitOrigin-RevId: 6a8a3c6267501789f2047a67b03db6ac6df427c3
67 lines
2.2 KiB
JavaScript
67 lines
2.2 KiB
JavaScript
const { NoXrefTableError } = require('./Errors')
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const fs = require('fs')
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const { O_RDONLY, O_NOFOLLOW } = fs.constants
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const MAX_XREF_FILE_SIZE = 1024 * 1024
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/** Parse qpdf --show-xref output to get a table of xref entries
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*
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* @param {string} filePath
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* @param {number} pdfFileSize
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* @returns
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*/
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async function parseXrefTable(filePath, pdfFileSize) {
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try {
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// the xref table will be written to output.pdfxref when available
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const xRefFilePath = filePath + 'xref'
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// check the size of the file (as it is untrusted)
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const stats = await fs.promises.stat(xRefFilePath)
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if (!stats.isFile()) {
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throw new NoXrefTableError('xref file invalid type')
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}
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if (stats.size === 0) {
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throw new NoXrefTableError('xref file empty')
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}
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if (stats.size > MAX_XREF_FILE_SIZE) {
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throw new NoXrefTableError('xref file too large')
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}
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const content = await fs.promises.readFile(xRefFilePath, {
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encoding: 'ascii',
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flag: O_RDONLY | O_NOFOLLOW,
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})
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// the qpdf xref table output looks like this:
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//
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// 3/0: uncompressed; offset = 194159
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//
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// we only need the uncompressed objects
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const matches = content.matchAll(
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// put an upper limit of 10^10 on all the matched numbers for safety
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// ignore the generation id in "id/gen"
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// in a linearized pdf all objects must have generation number 0
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/^\d{1,9}\/\d{1,9}: uncompressed; offset = (\d{1,9})$/gm
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)
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// include a zero-index object for backwards compatibility with
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// our existing xref table parsing code
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const xRefEntries = [{ offset: 0 }]
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// extract all the xref table entries
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for (const match of matches) {
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const offset = parseInt(match[1], 10)
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xRefEntries.push({ offset, uncompressed: true })
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}
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if (xRefEntries.length === 1) {
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throw new NoXrefTableError('xref file has no objects')
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}
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return { xRefEntries }
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} catch (err) {
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if (err instanceof NoXrefTableError) {
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throw err
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} else if (err.code) {
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throw new NoXrefTableError(`xref file error ${err.code}`)
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} else {
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throw new NoXrefTableError('xref file parse error')
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}
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}
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}
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module.exports = {
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parseXrefTable,
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}
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