From 73b6e703fbb1c3154ee90ff132e74f63cf45335c Mon Sep 17 00:00:00 2001
From: a dinosaur <dino@a-dinosaur.com>
Date: Wed, 13 Nov 2024 21:20:50 +1100
Subject: [PATCH] Optimise hex digest string conversion

---
 Sources/apk/Index/ApkIndexDigest.swift | 25 ++++++++++++++++++++++++-
 1 file changed, 24 insertions(+), 1 deletion(-)

diff --git a/Sources/apk/Index/ApkIndexDigest.swift b/Sources/apk/Index/ApkIndexDigest.swift
index ac0d3d9..2de5798 100644
--- a/Sources/apk/Index/ApkIndexDigest.swift
+++ b/Sources/apk/Index/ApkIndexDigest.swift
@@ -105,5 +105,28 @@ extension ApkIndexDigest.DigestType: CustomStringConvertible {
 }
 
 extension ApkIndexDigest: CustomStringConvertible {
-  var description: String { "[\(self.type)] \(self.data.map { String(format: "%02X", $0) }.joined())" }
+#if DEBUG
+  private static let hex = Array("0123456789ABCDEF".unicodeScalars)
+  var description: String {
+    var s = "[\(self.type)] "
+    s.reserveCapacity(10 + self.data.count * 2)
+    Self.hex.withUnsafeBufferPointer { hp in
+      for b in self.data {
+        s.unicodeScalars.append(hp[Int(b >> 4)])
+        s.unicodeScalars.append(hp[Int(b & 15)])
+      }
+    }
+    return s
+  }
+#else
+  private static let hex = "0123456789ABCDEF".map(\.asciiValue!)
+  var description: String {
+    Self.hex.withUnsafeBufferPointer { hp in
+      let hexChars = self.data.flatMap { b in
+        [hp[Int(b >> 4)], hp[Int(b & 15)]]
+      }
+      return "[\(self.type)] \(String(bytes: hexChars, encoding: .ascii)!)"
+    }
+  }
+#endif
 }