From c215e1fb62fe276b024b20afdb2a6176c79dfb9d Mon Sep 17 00:00:00 2001
From: Jonas Borjesson <jonas@jonasborjesson.com>
Date: Fri, 20 Oct 2023 10:38:27 -0700
Subject: [PATCH] Allowing to dump a string to hex using lowercase alphabet

Turns out that e.g. GitHub is using lowercase alphabet for their hex dumps so when comparing signatures we need to also be able to change the alphabet to lower case.
---
 .../java/com/google/polo/pairing/HexDump.java | 51 ++++++++++++++++---
 .../com/google/polo/pairing/HexDumpTest.java  | 19 +++++++
 2 files changed, 64 insertions(+), 6 deletions(-)
 create mode 100644 snice-commons/src/test/java/com/google/polo/pairing/HexDumpTest.java

diff --git a/snice-commons/src/main/java/com/google/polo/pairing/HexDump.java b/snice-commons/src/main/java/com/google/polo/pairing/HexDump.java
index d9154ed..4689ca2 100644
--- a/snice-commons/src/main/java/com/google/polo/pairing/HexDump.java
+++ b/snice-commons/src/main/java/com/google/polo/pairing/HexDump.java
@@ -19,14 +19,39 @@
 import java.nio.charset.Charset;
 
 public class HexDump {
-    private final static char[] HEX_DIGITS = {
+   private final static char[] HEX_DIGITS = {
             '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F' };
 
+    private final static char[] HEX_DIGITS_LOWER_CASE = {
+            '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' };
+
+    /**
+     * Dump a byte array as hex, with the option to select whether the ABCDEF hex digits should be
+     * upper or lower case.
+     */
+    public static String dumpHexString(final byte[] array, boolean upperCase) {
+        return dumpHexString(array, 0, array.length, upperCase);
+    }
+
     public static String dumpHexString(final byte[] array) {
-        return dumpHexString(array, 0, array.length);
+        return dumpHexString(array, 0, array.length, true);
     }
 
     public static String dumpHexString(final byte[] array, final int offset, final int length) {
+        return dumpHexString(array, offset, length, true);
+    }
+
+    /**
+     * Dump the given byte array as a hex string, with the option to select whether the ABCDEF hex digits should be
+     * upper or lower case.
+     *
+     * @param array the byte array
+     * @param offset the offset into the byte array
+     * @param length the length of the byte array to dump
+     * @param upperCase flag indicating whether the ABCDEF hex digits should be upper or lower case.
+     * @return
+     */
+    public static String dumpHexString(final byte[] array, final int offset, final int length, boolean upperCase) {
         final StringBuilder result = new StringBuilder();
 
         final byte[] line = new byte[16];
@@ -84,11 +109,19 @@ public static String toHexString(final byte b) {
     }
 
     public static String toHexString(final boolean prefix, final byte[] array) {
-        return toHexString(prefix, array, 0, array.length);
+        return toHexString(prefix, array, 0, array.length, true);
+    }
+
+    public static String toHexString(final boolean prefix, final byte[] array, final boolean upperCase) {
+        return toHexString(prefix, array, 0, array.length, upperCase);
+    }
+
+    public static String toHexString(final byte[] array, final boolean upperCase) {
+        return toHexString(true, array, 0, array.length, upperCase);
     }
 
     public static String toHexString(final byte[] array) {
-        return toHexString(true, array, 0, array.length);
+        return toHexString(true, array, 0, array.length, true);
     }
 
     public static String toHexString(final byte[] array, final int offset, final int length) {
@@ -96,6 +129,12 @@ public static String toHexString(final byte[] array, final int offset, final int
     }
 
     public static String toHexString(final boolean prefix, final byte[] array, final int offset, final int length) {
+        return toHexString(prefix, array, offset, length, true);
+    }
+
+    public static String toHexString(final boolean prefix, final byte[] array, final int offset, final int length, boolean upperCase) {
+        final char[] alphabet = upperCase ? HEX_DIGITS : HEX_DIGITS_LOWER_CASE;
+
         final char[] buf;
         int bufIndex = 0;
 
@@ -112,8 +151,8 @@ public static String toHexString(final boolean prefix, final byte[] array, final
 
         for (int i = offset; i < (offset + length); i++) {
             final byte b = array[i];
-            buf[bufIndex++] = HEX_DIGITS[(b >>> 4) & 0x0F];
-            buf[bufIndex++] = HEX_DIGITS[b & 0x0F];
+            buf[bufIndex++] = alphabet[(b >>> 4) & 0x0F];
+            buf[bufIndex++] = alphabet[b & 0x0F];
         }
 
         return new String(buf);
diff --git a/snice-commons/src/test/java/com/google/polo/pairing/HexDumpTest.java b/snice-commons/src/test/java/com/google/polo/pairing/HexDumpTest.java
new file mode 100644
index 0000000..771dc80
--- /dev/null
+++ b/snice-commons/src/test/java/com/google/polo/pairing/HexDumpTest.java
@@ -0,0 +1,19 @@
+package com.google.polo.pairing;
+
+import org.junit.Test;
+
+import static org.junit.Assert.*;
+
+/**
+ * @author borjesson.jonas@gmail.com
+ */
+public class HexDumpTest {
+
+    @Test
+    public void testDumpHexString() {
+        final var bytes = new byte[] { 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, (byte) 0xFF };
+        assertEquals("0x0A0B0C0D0EFF", HexDump.toHexString(bytes));
+        assertEquals("0x0a0b0c0d0eff", HexDump.toHexString(bytes, false));
+    }
+
+}
\ No newline at end of file