Merge pull request #58 from tayloraswift/gzip

Gzip

Package.swift

@@ -24,13 +24,15 @@ let package:Package = .init(name: "swift-png",
     ],
     targets:
     [
-        .target(name: "LZ77"),
+        .target(name: "LZ77", dependencies:
+            [
+                .product(name: "CRC", package: "swift-hash"),
+            ]),
 
         .target(name: "PNG",
             dependencies:
             [
                 .target(name: "LZ77"),
-                .product(name: "CRC", package: "swift-hash"),
             ]),
 
         .target(name: "PNGInspection",

Snippets/GzipCompression.swift

@@ -0,0 +1,40 @@
+import LZ77
+import PNG
+
+let path:String = "Snippets/GzipCompression/example"
+
+guard
+let original:[UInt8] = (System.File.Source.open(path: "\(path).gz")
+{
+    (source:inout System.File.Source) -> [UInt8]? in
+
+    guard let count:Int = source.count
+    else
+    {
+        return nil
+    }
+    return source.read(count: count)
+} ?? nil)
+else
+{
+    fatalError("failed to open or read file '\(path).gz'")
+}
+
+var inflator:Gzip.Inflator = .init()
+try inflator.push(original[...])
+
+let utf8:[UInt8] = inflator.pull()
+let text:String = .init(decoding: utf8, as: Unicode.UTF8.self)
+
+print(text)
+
+var deflator:Gzip.Deflator = .init(level: 13, exponent: 15, hint: 128 << 10)
+    deflator.push(utf8[...], last: true)
+
+let _:Void? = System.File.Destination.open(path: "\(path).txt.gz")
+{
+    while let part:[UInt8] = deflator.pull()
+    {
+        $0.write(part)
+    }
+}

Sources/LZ77/Deflator/LZ77.Deflator.swift

@@ -8,48 +8,21 @@ extension LZ77
     struct Deflator
     {
         private
-        var stream:Stream
+        var buffers:DeflatorBuffers<LZ77.Format>
+
+        public
+        init(format:LZ77.Format = .zlib, level:Int, exponent:Int = 15, hint:Int = 1 << 12)
+        {
+            self.buffers = .init(format: format, level: level, exponent: exponent, hint: hint)
+        }
     }
 }
 extension LZ77.Deflator
 {
-    public
-    init(format:LZ77.DeflateFormat = .zlib, level:Int, exponent:Int = 15, hint:Int = 1 << 12)
-    {
-        let e:Int
-        switch format
-        {
-        case .zlib: e = exponent
-        case .ios : e = 15
-        }
-
-        self.stream = .init(format: format, level: level, exponent: e, hint: hint)
-        self.stream.start(exponent: e)
-    }
-
     public mutating
     func push(_ data:ArraySlice<UInt8>, last:Bool = false)
     {
-        // rebase input buffer
-        if !data.isEmpty
-        {
-            self.stream.input.enqueue(contentsOf: data)
-        }
-        guard self.stream.input.count > 4096 || last
-        else
-        {
-            return
-        }
-
-        while let _:Void = self.stream.compress(all: last)
-        {
-            self.stream.block(final: false)
-        }
-        if last
-        {
-            self.stream.block(final: true)
-            self.stream.checksum()
-        }
+        self.buffers.push(data, last: last)
     }
 
     /// Returns a block of compressed data from this deflator, if available. If no compressed
@@ -58,20 +31,14 @@ extension LZ77.Deflator
     public mutating
     func pull() -> [UInt8]?
     {
-        if  let complete:[UInt8] = self.pop()
-        {
-            return complete
-        }
-
-        let flushed:[UInt8] = self.stream.output.pull()
-        return flushed.isEmpty ? nil : flushed
+        self.buffers.pull()
     }
 
     /// Removes and returns a complete block of compressed data from this deflator, if
     /// available.
     public mutating
     func pop() -> [UInt8]?
     {
-        self.stream.output.pop()
+        self.buffers.pop()
     }
 }