Fix a performance issue with decoding base16 encoded string

EosioSwift.podspec

@@ -24,7 +24,7 @@ Pod::Spec.new do |s|
 
   s.source           = { :git => 'https://github.com/EOSIO/eosio-swift.git', :tag => "v" + s.version.to_s }
 
-  s.swift_version         = '4.2'
+  s.swift_version         = '5.0'
   s.ios.deployment_target = '11.0'
 
   s.source_files = 'EosioSwift/**/*.swift'
@@ -36,4 +36,5 @@ Pod::Spec.new do |s|
 
   s.ios.dependency 'BigInt', '~> 3.1'
   s.ios.dependency 'PromiseKit', '~> 6.8'
+  s.ios.dependency 'Base16'
 end

EosioSwift/Extensions/DataExtensions.swift

@@ -8,6 +8,7 @@
 
 import Foundation
 import CommonCrypto
+import Base16
 
 public extension Data {
 
@@ -57,17 +58,8 @@ public extension Data {
     ///
     /// - Parameter hexString: A Base16 encoded string.
     init?(hexString: String) {
-        let len = hexString.count / 2
-        var data = Data(capacity: len)
-        for i in 0..<len {
-            let j = hexString.index(hexString.startIndex, offsetBy: i*2) // swiftlint:disable:this identifier_name
-            let k = hexString.index(j, offsetBy: 2) // swiftlint:disable:this identifier_name
-            let bytes = hexString[j..<k]
-            if var num = UInt8(bytes, radix: 16) {
-                data.append(&num, count: 1)
-            } else {
-                return nil
-            }
+        guard let data = try? Base16.decode(hexString) else {
+            return nil
         }
         self = data
     }

Podfile

@@ -13,4 +13,5 @@ target 'EosioSwift' do
   pod 'BigInt', '~> 3.1', :inhibit_warnings => true
   pod 'SwiftLint'
   pod 'PromiseKit', '~> 6.8'
+  pod 'Base16'
 end

Podfile.lock

@@ -1,4 +1,5 @@
 PODS:
+  - Base16 (0.1.0)
   - BigInt (3.1.0):
     - SipHash (~> 1.2)
   - OHHTTPStubs/Core (8.0.0)
@@ -27,26 +28,29 @@ PODS:
   - SwiftLint (0.32.0)
 
 DEPENDENCIES:
+  - Base16
   - BigInt (~> 3.1)
   - OHHTTPStubs/Swift
   - PromiseKit (~> 6.8)
   - SwiftLint
 
 SPEC REPOS:
   https://github.com/cocoapods/specs.git:
+    - Base16
     - BigInt
     - OHHTTPStubs
     - PromiseKit
     - SipHash
     - SwiftLint
 
 SPEC CHECKSUMS:
+  Base16: cf36a62b7936f7bd0b80e84299e41e4098c66457
   BigInt: 76b5dfdfa3e2e478d4ffdf161aeede5502e2742f
   OHHTTPStubs: 9cbce6364bec557cc3439aa6bb7514670d780881
   PromiseKit: 51794a832647e7b819336dc2279039ce9f1cc49b
   SipHash: fad90a4683e420c52ef28063063dbbce248ea6d4
   SwiftLint: 009a898ef2a1c851f45e1b59349bf6ff2ddc990d
 
-PODFILE CHECKSUM: 1d10bec70f8d2560be35e67e47b034772bba25f7
+PODFILE CHECKSUM: a4243c338086085c3dd9dc5842406963c397c4ee
 
 COCOAPODS: 1.7.5