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zip.js
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zip.js
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class BinaryWriter {
constructor(buffer, offset, length) {
this.data = new DataView(buffer, offset, length);
this.position = 0;
}
writeInt16(value, littleEndian) {
this.data.setInt16(this.position, value, littleEndian);
this.position += 2;
}
writeInt32(value, littleEndian) {
this.data.setInt32(this.position, value, littleEndian);
this.position += 4;
}
writeData(data) {
const window = new Uint8Array(this.data.buffer, this.data.byteOffset + this.position, data.length);
for (let i = 0; i < data.length; i++)
window[i] = data[i];
this.position += data.length;
}
}
const crc = new Crc32();
function getEntryRecordSize(entry) {
return 30 + entry.nameData.length + entry.fileData.length;
}
function writeEntryRecord(entry, writer) {
writer.writeInt32(0x504B0304); // Signature
writer.writeInt32(0x0A000000); // Version and Flags
writer.writeInt16(0x0000); // Compression type
writer.writeInt16(0x0000); // Time
writer.writeInt16(0x0000); // Date
writer.writeInt32(crc.calculate(entry.fileData), true); // CRC32
writer.writeInt32(entry.fileData.length, true); // Compressed file size
writer.writeInt32(entry.fileData.length, true); // Uncompressed file size
writer.writeInt16(entry.nameData.length, true); // File name length
writer.writeInt16(0); // Extra field length
writer.writeData(entry.nameData);
writer.writeData(entry.fileData);
}
function getCentralDirectoryEntrySize(entry) {
return 46 + entry.nameData.length;
}
function writeCentralDirectoryEntry(entry, writer) {
writer.writeInt32(0x504b0102); // Signature
writer.writeInt16(0x3F00); // Version made by
writer.writeInt16(0x1000); // Version to extract
writer.writeInt16(0x0000); // Flags
writer.writeInt16(0x0000); // Compression type
writer.writeInt16(0x0000); // Time
writer.writeInt16(0x0000); // Date
writer.writeInt32(crc.calculate(entry.fileData), true); // CRC32
writer.writeInt32(entry.fileData.length, true); // Compressed file size
writer.writeInt32(entry.fileData.length, true); // Uncompressed file size
writer.writeInt16(entry.nameData.length, true); // File name length
writer.writeInt16(0); // Extra field length
writer.writeInt16(0); // Field comment length
writer.writeInt16(0); // Disk number
writer.writeInt16(0); // Internal attributes
writer.writeInt32(32, true); // External attributes
writer.writeInt32(entry.dataPosition, true); // Data offset
writer.writeData(entry.nameData);
}
function getEndLocatorSize() {
return 22;
}
function writeEndLocator(writer, entryCount, directoryOffset, directorySize) {
writer.writeInt32(0x504b0506); // Signature
writer.writeInt16(0); // Disk number
writer.writeInt16(0); // Start disk number
writer.writeInt16(entryCount, true); // Entries on disk
writer.writeInt16(entryCount, true); // Entries in directory
writer.writeInt32(directorySize, true); // Directory size
writer.writeInt32(directoryOffset, true); // Directory offset
writer.writeInt16(0); // Comment length
}
function createZip(files) {
let totalSize = 0;
for (let file of files) {
totalSize += getEntryRecordSize(file);
totalSize += getCentralDirectoryEntrySize(file);
}
totalSize += getEndLocatorSize();
const result = new ArrayBuffer(totalSize);
let position = 0;
// Write the records
for (let file of files) {
const entryRecordSize = getEntryRecordSize(file);
file.dataPosition = position;
const writer = new BinaryWriter(result, position, entryRecordSize);
writeEntryRecord(file, writer);
position += entryRecordSize;
}
const centralDirectoryStart = position;
// Write the directory
for (let file of files) {
const centralDirectoryEntrySize = getCentralDirectoryEntrySize(file);
const writer = new BinaryWriter(result, position, centralDirectoryEntrySize);
writeCentralDirectoryEntry(file, writer);
position += centralDirectoryEntrySize;
}
// Write the endlocator
{
const writer = new BinaryWriter(result, position, getEndLocatorSize());
writeEndLocator(writer, files.length, centralDirectoryStart, position - centralDirectoryStart);
}
console.info(new Uint8Array(result));
return result;
}