diff --git a/Sources/BZip2.swift b/Sources/BZip2.swift
index a5825f2b..2d862447 100644
--- a/Sources/BZip2.swift
+++ b/Sources/BZip2.swift
@@ -80,6 +80,7 @@ public class BZip2: DecompressionAlgorithm {
 
         while true {
             let blockType: Int64 = Int64(pointerData.intFromBits(count: 48))
+            // TODO: Add CRC check.
             // Next 32 bits are crc (which currently is not checked).
             let _ = pointerData.intFromBits(count: 32)
 
@@ -114,7 +115,9 @@ public class BZip2: DecompressionAlgorithm {
                         bitMask >>= 1
                     }
                 } else {
-                    used.append(contentsOf: Array(repeating: false, count: 16))
+                    for _ in 0..<16 {
+                        used.append(false)
+                    }
                 }
                 mapMask >>= 1
             }
@@ -209,7 +212,9 @@ public class BZip2: DecompressionAlgorithm {
                 repeatPower <<= 1
                 continue
             } else if repeat_ > 0 {
-                buffer.append(contentsOf: Array(repeating: favourites[0], count: repeat_))
+                for _ in 0..<repeat_ {
+                    buffer.append(favourites[0])
+                }
                 repeat_ = 0
             }
             if symbol == symbolsInUse - 1 {
diff --git a/Sources/Deflate.swift b/Sources/Deflate.swift
index b1a7b545..f4bcecd9 100644
--- a/Sources/Deflate.swift
+++ b/Sources/Deflate.swift
@@ -72,11 +72,8 @@ public class Deflate: DecompressionAlgorithm {
                 // Process uncompressed data into the output
                 // TODO: Replace precondition with guard and error throwing.
                 precondition(pointerData.bitMask == 1, "Misaligned byte.")
-                var ind = out.count
-                out.append(contentsOf: Array(repeating: 0, count: length))
                 for _ in 0..<length {
-                    out[ind] = pointerData.alignedByte()
-                    ind += 1
+                    out.append(pointerData.alignedByte())
                 }
             } else if blockType == [1, 0] || blockType == [0, 1] {
                 // Block with Huffman coding (either static or dynamic)
@@ -149,7 +146,9 @@ public class Deflate: DecompressionAlgorithm {
                         } else {
                             throw DeflateError.HuffmanTableError
                         }
-                        codeLengths.append(contentsOf: Array(repeating: what, count: count))
+                        for _ in 0..<count {
+                            codeLengths.append(what)
+                        }
                         n += count
                     }
                     // We have read codeLengths for both tables at once.
@@ -197,9 +196,12 @@ public class Deflate: DecompressionAlgorithm {
                             // The amount of times we do this is round(length / distance).
                             // length actually indicates the amount of data we get from this nextSymbol.
                             let repeatCount: Int = length / distance
-                            let arrayToRepeat = Array(repeating: out[out.count - distance..<out.count],
-                                                      count: repeatCount).flatMap { $0 }
-                            out.append(contentsOf: arrayToRepeat)
+                            let count = out.count
+                            for _ in 0..<repeatCount {
+                                for i in count - distance..<count {
+                                    out.append(out[i])
+                                }
+                            }
                             // Now we deal with the remainings.
                             if length - distance * repeatCount == distance {
                                 for i in out.count - distance..<out.count {
diff --git a/Sources/HuffmanTree.swift b/Sources/HuffmanTree.swift
index 5a7ce074..8292211f 100644
--- a/Sources/HuffmanTree.swift
+++ b/Sources/HuffmanTree.swift
@@ -45,8 +45,9 @@ class HuffmanTree: CustomStringConvertible {
             let finish = pair[0]
             let endbits = pair[1]
             if bits > 0 {
-                lengths.append(contentsOf:
-                    (start..<finish).map { [$0, bits] })
+                for i in start..<finish{
+                    lengths.append([i, bits])
+                }
             }
             start = finish
             bits = endbits
diff --git a/Sources/ZlibArchive.swift b/Sources/ZlibArchive.swift
index dca3178b..cc854def 100644
--- a/Sources/ZlibArchive.swift
+++ b/Sources/ZlibArchive.swift
@@ -97,7 +97,6 @@ public class ZlibArchive: Archive {
         if fdict == 1 {
             pointerData.index += 4
         }
-        // TODO: Add parsing of preset dictionary
 
         return info
     }
@@ -108,8 +107,8 @@ public class ZlibArchive: Archive {
         If data passed is not actually a zlib archive, `ZlibError` will be thrown.
 
         If data inside the archive is not actually compressed with DEFLATE algorithm, `DeflateError` will be thrown.
-     
-     - Note: This function is NOT specification compliant because it does not checks ADLER-32 checksum and preset dicitionaries.
+    
+     - Note: This function is specification compliant.
 
      - Parameter archiveData: Data compressed with zlib.
 
diff --git a/Tests/GzipTests.swift b/Tests/GzipTests.swift
index 5b9c641c..b66f9f01 100644
--- a/Tests/GzipTests.swift
+++ b/Tests/GzipTests.swift
@@ -14,7 +14,8 @@ class GzipTests: XCTestCase {
     static let testType: String = "gz"
 
     func perform(test testName: String, answer answerServiceInfo: GzipArchive.ServiceInfo) {
-        guard let testData = try? Data(contentsOf: Constants.url(forTest: testName, withType: GzipTests.testType)) else {
+        guard let testData = try? Data(contentsOf: Constants.url(forTest: testName,
+                                                                 withType: GzipTests.testType)) else {
             XCTFail("Failed to load test archive")
             return
         }
@@ -112,7 +113,8 @@ class GzipTests: XCTestCase {
     }
 
     func testGzipFull() {
-        guard let testData = try? Data(contentsOf: Constants.url(forTest: "random_file", withType: GzipTests.testType)) else {
+        guard let testData = try? Data(contentsOf: Constants.url(forTest: "random_file",
+                                                                 withType: GzipTests.testType)) else {
             XCTFail("Failed to load test archive")
             return
         }
diff --git a/Tests/ZlibTests.swift b/Tests/ZlibTests.swift
index e7ee60be..546d32a1 100644
--- a/Tests/ZlibTests.swift
+++ b/Tests/ZlibTests.swift
@@ -15,7 +15,8 @@ class ZlibTests: XCTestCase {
 
     func testZlib() {
         let testName = "test"
-        guard let testData = try? Data(contentsOf: Constants.url(forTest: testName, withType: ZlibTests.testType)) else {
+        guard let testData = try? Data(contentsOf: Constants.url(forTest: testName,
+                                                                 withType: ZlibTests.testType)) else {
             XCTFail("Failed to load test archive")
             return
         }
@@ -33,7 +34,8 @@ class ZlibTests: XCTestCase {
     }
 
     func testZlibFull() {
-        guard let testData = try? Data(contentsOf: Constants.url(forTest: "random_file", withType: ZlibTests.testType)) else {
+        guard let testData = try? Data(contentsOf: Constants.url(forTest: "random_file",
+                                                                 withType: ZlibTests.testType)) else {
             XCTFail("Failed to load test archive")
             return
         }