@cantoo/pdf-lib
Version:
Create and modify PDF files with JavaScript
165 lines • 6.97 kB
JavaScript
import PDFRef from '../objects/PDFRef.js';
import CharCodes from '../syntax/CharCodes.js';
import { copyStringIntoBuffer, padStart } from '../../utils/index.js';
/**
* Entries should be added using the [[addEntry]] and [[addDeletedEntry]]
* methods.
*/
class PDFCrossRefSection {
constructor(firstEntry) {
this.subsections = firstEntry ? [[firstEntry]] : [];
this.chunkIdx = 0;
this.chunkLength = firstEntry ? 1 : 0;
}
addEntry(ref, offset) {
this.append({ ref, offset, deleted: false });
}
addDeletedEntry(ref, nextFreeObjectNumber) {
// fix the first entry if required
if (!this.subsections.length) {
this.subsections = [
[
{
ref: PDFRef.of(0, 65535),
offset: ref.objectNumber,
deleted: true,
},
],
];
this.chunkIdx = 0;
this.chunkLength = 1;
}
else if (!this.subsections[0][0].offset) {
this.subsections[0][0].offset = ref.objectNumber;
}
this.append({ ref, offset: nextFreeObjectNumber, deleted: true });
}
toString() {
let section = 'xref\n';
for (let rangeIdx = 0, rangeLen = this.subsections.length; rangeIdx < rangeLen; rangeIdx++) {
const range = this.subsections[rangeIdx];
section += `${range[0].ref.objectNumber} ${range.length}\n`;
for (let entryIdx = 0, entryLen = range.length; entryIdx < entryLen; entryIdx++) {
const entry = range[entryIdx];
section += padStart(String(entry.offset), 10, '0');
section += ' ';
section += padStart(String(entry.ref.generationNumber), 5, '0');
section += ' ';
section += entry.deleted ? 'f' : 'n';
section += ' \n';
}
}
return section;
}
sizeInBytes() {
let size = 5;
for (let idx = 0, len = this.subsections.length; idx < len; idx++) {
const subsection = this.subsections[idx];
const subsectionLength = subsection.length;
const [firstEntry] = subsection;
size += 2;
size += String(firstEntry.ref.objectNumber).length;
size += String(subsectionLength).length;
size += 20 * subsectionLength;
}
return size;
}
copyBytesInto(buffer, offset) {
const initialOffset = offset;
buffer[offset++] = CharCodes.x;
buffer[offset++] = CharCodes.r;
buffer[offset++] = CharCodes.e;
buffer[offset++] = CharCodes.f;
buffer[offset++] = CharCodes.Newline;
offset += this.copySubsectionsIntoBuffer(this.subsections, buffer, offset);
return offset - initialOffset;
}
copySubsectionsIntoBuffer(subsections, buffer, offset) {
const initialOffset = offset;
const length = subsections.length;
for (let idx = 0; idx < length; idx++) {
const subsection = this.subsections[idx];
const firstObjectNumber = String(subsection[0].ref.objectNumber);
offset += copyStringIntoBuffer(firstObjectNumber, buffer, offset);
buffer[offset++] = CharCodes.Space;
const rangeLength = String(subsection.length);
offset += copyStringIntoBuffer(rangeLength, buffer, offset);
buffer[offset++] = CharCodes.Newline;
offset += this.copyEntriesIntoBuffer(subsection, buffer, offset);
}
return offset - initialOffset;
}
copyEntriesIntoBuffer(entries, buffer, offset) {
const length = entries.length;
for (let idx = 0; idx < length; idx++) {
const entry = entries[idx];
const entryOffset = padStart(String(entry.offset), 10, '0');
offset += copyStringIntoBuffer(entryOffset, buffer, offset);
buffer[offset++] = CharCodes.Space;
const entryGen = padStart(String(entry.ref.generationNumber), 5, '0');
offset += copyStringIntoBuffer(entryGen, buffer, offset);
buffer[offset++] = CharCodes.Space;
buffer[offset++] = entry.deleted ? CharCodes.f : CharCodes.n;
buffer[offset++] = CharCodes.Space;
buffer[offset++] = CharCodes.Newline;
}
return 20 * length;
}
append(currEntry) {
if (this.chunkLength === 0) {
this.subsections.push([currEntry]);
this.chunkIdx = 0;
this.chunkLength = 1;
return;
}
const chunk = this.subsections[this.chunkIdx];
const prevEntry = chunk[this.chunkLength - 1];
if (currEntry.ref.objectNumber - prevEntry.ref.objectNumber !== 1) {
// the current chunk is not the right chunk, find the right one, or create a new one
for (let c = 0; c < this.subsections.length; c++) {
const first = this.subsections[c][0];
const last = this.subsections[c][this.subsections[c].length - 1];
if (first.ref.objectNumber > currEntry.ref.objectNumber) {
// goes before this subsection, or at the start of it
if (first.ref.objectNumber - currEntry.ref.objectNumber === 1) {
// first element of subsection
this.subsections[c].unshift(currEntry);
if (c === this.chunkIdx)
this.chunkLength += 1;
return;
}
else {
// create subsection
this.subsections.splice(c, 0, [currEntry]);
this.chunkIdx++;
return;
}
}
else if (last.ref.objectNumber > currEntry.ref.objectNumber) {
// goes in this subsection, find its place..
const cep = this.subsections[c].findIndex((ee) => ee.ref.objectNumber > currEntry.ref.objectNumber);
this.subsections[c].splice(cep, 0, currEntry);
if (c === this.chunkIdx)
this.chunkLength += 1;
}
// bigger, keep looking
}
// if got to here, then a new subsection is required
this.subsections.push([currEntry]);
this.chunkIdx += 1;
this.chunkLength = 1;
}
else {
chunk.push(currEntry);
this.chunkLength += 1;
}
}
}
PDFCrossRefSection.create = () => new PDFCrossRefSection({
ref: PDFRef.of(0, 65535),
offset: 0,
deleted: true,
});
PDFCrossRefSection.createEmpty = () => new PDFCrossRefSection();
export default PDFCrossRefSection;
//# sourceMappingURL=PDFCrossRefSection.js.map