Added offset setter method for reader class

JackRKelly · Dec 20, 2020 · 48044e3 · 48044e3
1 parent 59d1538
commit 48044e3
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Showing 2 changed files with 49 additions and 45 deletions.
diff --git a/src/reader.ts b/src/reader.ts
@@ -66,6 +66,10 @@ export class Reader {
  return this.buffer.indexOf(header, 0, "hex");
  }
 
+ setOffset(offset: number): void {
+ this.offset = offset;
+ }
+
  constructor(zip: Buffer) {
  this.offset = 0;
  this.buffer = zip;

diff --git a/src/unzip.ts b/src/unzip.ts
@@ -3,21 +3,21 @@ import * as fs from "fs";
 import { compressionMethod, formatModTime, formatModDate } from "./util";
 
 const readLocalFileHeader = (reader: Reader) => {
- // 0 | 4 : Local file header signature = 0x04034b50 (read as a little-endian number)
- // 4 | 2 : Version needed to extract (minimum)
- // 6 | 2 : General purpose bit flag
- // 8 | 2 : Compression method
- // 10 | 2 : File last modification time
- // 12 | 2 : File last modification date
- // 14 | 4 : CRC-32 of uncompressed data
- // 18 | 4 : Compressed size
- // 22 | 4 : Uncompressed size
- // 26 | 2 : File name length (n)
- // 28 | 2 : Extra field length (m)
- // 30 | n : File name
- // 30+n | m : Extra field
+ // 0 | 4 : Local file header signature = 0x04034b50 (read as a little-endian number)
+ // 4 | 2 : Version needed to extract (minimum)
+ // 6 | 2 : General purpose bit flag
+ // 8 | 2 : Compression method
+ // 10 | 2 : File last modification time
+ // 12 | 2 : File last modification date
+ // 14 | 4 : CRC-32 of uncompressed data
+ // 18 | 4 : Compressed size
+ // 22 | 4 : Uncompressed size
+ // 26 | 2 : File name length (n)
+ // 28 | 2 : Extra field length (m)
+ // 30 | n : File name
+ // 30+n | m : Extra field
 
- reader.offset = reader.findHeader(LESignature.LocalFile);
+ reader.setOffset(reader.findHeader(LESignature.LocalFile));
  let signature = reader.read4Bytes();
  let extractVersion = reader.read2Bytes();
  let bitFlag = reader.read2Bytes();
@@ -53,28 +53,28 @@ const readLocalFileHeader = (reader: Reader) => {
 };
 
 const readCentralDirectory = (reader: Reader) => {
- // 0  | 4 : Central directory file header signature = 0x02014b50
- // 4  | 2 : Version made by
- // 6  | 2 : Version needed to extract (minimum)
- // 8  | 2 : General purpose bit flag
- // 10  | 2 : Compression method
- // 12  | 2 : File last modification time
- // 14  | 2 : File last modification date
- // 16  | 4 : CRC-32 of uncompressed data
- // 20  | 4 : Compressed size
- // 24  | 4 : Uncompressed size
- // 28  | 2 : File name length (n)
- // 30  | 2 : Extra field length (m)
- // 32  | 2 : File comment length (k)
- // 34  | 2 : Disk number where file starts
- // 36  | 2 : Internal file attributes
- // 38  | 4 : External file attributes
- // 42  | 4 : Relative offset of local file header. This is the number of bytes between the start of the first disk on which the file occurs, and the start of the local file header. This allows software reading the central directory to locate the position of the file inside the ZIP file.
- // 46  | n : File name
- // 46+n  | m : Extra field
- // 46+n+m | k : File comment
+ // 0  | 4 : Central directory file header signature = 0x02014b50
+ // 4  | 2 : Version made by
+ // 6  | 2 : Version needed to extract (minimum)
+ // 8  | 2 : General purpose bit flag
+ // 10  | 2 : Compression method
+ // 12  | 2 : File last modification time
+ // 14  | 2 : File last modification date
+ // 16  | 4 : CRC-32 of uncompressed data
+ // 20  | 4 : Compressed size
+ // 24  | 4 : Uncompressed size
+ // 28  | 2 : File name length (n)
+ // 30  | 2 : Extra field length (m)
+ // 32  | 2 : File comment length (k)
+ // 34  | 2 : Disk number where file starts
+ // 36  | 2 : Internal file attributes
+ // 38  | 4 : External file attributes
+ // 42  | 4 : Relative offset of local file header. This is the number of bytes between the start of the first disk on which the file occurs, and the start of the local file header. This allows software reading the central directory to locate the position of the file inside the ZIP file.
+ // 46  | n : File name
+ // 46+n  | m : Extra field
+ // 46+n+m | k : File comment
 
- reader.offset = reader.findHeader(LESignature.CentralDirectory);
+ reader.setOffset(reader.findHeader(LESignature.CentralDirectory));
  let signature = reader.read4Bytes();
  let version = reader.read2Bytes();
  let extractVersion = reader.read2Bytes();
@@ -122,17 +122,17 @@ const readCentralDirectory = (reader: Reader) => {
 };
 
 const readEndCentralDirectory = (reader: Reader) => {
- // 0 | 4 : End of central directory signature = 0x06054b50
- // 4 | 2 : Number of this disk
- // 6 | 2 : Disk where central directory starts
- // 8 | 2 : Number of central directory records on this disk
- // 10 | 2 : Total number of central directory records
- // 12 | 4 : Size of central directory (bytes)
- // 16 | 4 : Offset of start of central directory, relative to start of archive
- // 20 | 2 : Comment length (n)
- // 22 | n : Comment
+ // 0 | 4 : End of central directory signature = 0x06054b50
+ // 4 | 2 : Number of this disk
+ // 6 | 2 : Disk where central directory starts
+ // 8 | 2 : Number of central directory records on this disk
+ // 10 | 2 : Total number of central directory records
+ // 12 | 4 : Size of central directory (bytes)
+ // 16 | 4 : Offset of start of central directory, relative to start of archive
+ // 20 | 2 : Comment length (n)
+ // 22 | n : Comment
 
- reader.offset = reader.findHeader(LESignature.EndCentralDirectory);
+ reader.setOffset(reader.findHeader(LESignature.EndCentralDirectory));
  let signature = reader.read4Bytes();
  let diskNumber = reader.read2Bytes();
  let diskCentralStart = reader.read2Bytes();