Fix NIOHTTPDecompression bug for multi-request channels (#221)

Motivation:

`NIOHTTPDecompression` erroneously accumulates decompressed data sizes across multiple requests in a single channel, leading to unwarranted `DecompressionError.limit` errors. This affects applications using persistent connections, as the decompression limits are improperly enforced. This change aims to address and rectify this issue.

Modifications:

- Add initialization of `inflated` within `Decompressor.initializeDecoder`.
- Introduced new tests to validate decompression functionality across multiple requests on the same channel

Result:

This fix ensures each request's decompression size is independently considered, eliminating incorrect limit errors, and enhancing reliability for applications using HTTP compression with persistent connections.

Author: sidepelican

Sources/NIOHTTPCompression/HTTPDecompression.swift

@@ -129,6 +129,7 @@ public enum NIOHTTPDecompression {
             self.stream.zalloc = nil
             self.stream.zfree = nil
             self.stream.opaque = nil
+            self.inflated = 0
 
             let rc = CNIOExtrasZlib_inflateInit2(&self.stream, encoding.window)
             guard rc == Z_OK else {

Tests/NIOHTTPCompressionTests/HTTPResponseDecompressorTest.swift

@@ -143,6 +143,21 @@ class HTTPResponseDecompressorTest: XCTestCase {
         }
     }
 
+    func testDecompressionMultipleWriteWithLimit() {
+        let channel = EmbeddedChannel()
+        XCTAssertNoThrow(try channel.pipeline.addHandler(NIOHTTPResponseDecompressor(limit: .size(272))).wait())
+
+        let headers = HTTPHeaders([("Content-Encoding", "deflate")])
+        // this compressed payload is 272 bytes long uncompressed
+        let body = ByteBuffer.of(bytes: [120, 156, 75, 76, 28, 5, 200, 0, 0, 248, 66, 103, 17])
+
+        for i in 0..<3 {
+            XCTAssertNoThrow(try channel.writeInbound(HTTPClientResponsePart.head(.init(version: .init(major: 1, minor: 1), status: .ok, headers: headers))), "\(i)")
+            XCTAssertNoThrow(try channel.writeInbound(HTTPClientResponsePart.body(body)), "\(i)")
+            XCTAssertNoThrow(try channel.writeInbound(HTTPClientResponsePart.end(nil)), "\(i)")
+        }
+    }
+
     func testDecompression() {
         let channel = EmbeddedChannel()
         XCTAssertNoThrow(try channel.pipeline.addHandler(NIOHTTPResponseDecompressor(limit: .none)).wait())