Squashed commit of the following:

commit 3ce3be7
Author: Martin Lau <martinlau@livemail.tw>
Date:   Tue Dec 22 18:06:59 2020 +0800

    add bzip2; add set Compression

commit 91757ad
Author: Martin Lau <martinlau@livemail.tw>
Date:   Tue Dec 22 15:31:00 2020 +0800

    update README

commit 65efb44
Author: martin.lau <martin.lau@office.feng.com>
Date:   Tue Dec 22 07:24:49 2020 +0000

    fix build error on linux

commit 5c070be
Author: Martin Lau <martinlau@livemail.tw>
Date:   Tue Dec 22 14:59:12 2020 +0800

    support ios

commit 39995d4
Author: Martin Lau <martinlau@livemail.tw>
Date:   Tue Dec 22 13:47:17 2020 +0800

    Update libzip to 1.7.3

Sources/LibzipSwift/ZipArchive.swift

@@ -10,6 +10,8 @@ import libzip
 
 public final class ZipArchive: ZipErrorHandler {
     private var compressionCallback: ((Double) -> Void)?
+    private var compressionMethod: CompressionMethod = .default
+    private var compressionLevel: CompressionLevel = .fastest
 
     internal var archivePointer: OpaquePointer!
 
@@ -305,6 +307,7 @@ public final class ZipArchive: ZipErrorHandler {
                     var external_fa = entry.externalAttributes.attributes
                     external_fa |= permissionsMask
                     try entry.setExternalAttributes(operatingSystem: .unix, attributes: external_fa)
+                    try entry.setCompression(method: compressionMethod, flags: compressionLevel)
                 }
             }
             return result
@@ -353,6 +356,11 @@ public final class ZipArchive: ZipErrorHandler {
         return false
     }
 
+    public func setCompression(cm: CompressionMethod, cl: CompressionLevel) {
+        compressionMethod = cm
+        compressionLevel = cl
+    }
+
     /// extract all entries to folder.
     /// - Parameters:
     ///   - dir: the dst folder.

Sources/LibzipSwift/ZipConst.swift

@@ -25,6 +25,7 @@ public struct CompressionMethod: RawRepresentable {
 
     public static let `default` = CompressionMethod(rawValue: ZIP_CM_DEFAULT)
     public static let store = CompressionMethod(rawValue: ZIP_CM_STORE)
+    public static let bzip2 = CompressionMethod(rawValue: ZIP_CM_BZIP2)
     public static let deflate = CompressionMethod(rawValue: ZIP_CM_DEFLATE)
     public static let deflate64 = CompressionMethod(rawValue: ZIP_CM_DEFLATE64)
 }