refactor: Move byte utilities to core:common module (#3977)

Signed-off-by: James Rich <2199651+jamesarich@users.noreply.github.com>

core/common/src/main/kotlin/org/meshtastic/core/common/ByteUtils.kt

@@ -0,0 +1,25 @@
+/*
+ * Copyright (c) 2025 Meshtastic LLC
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package org.meshtastic.core.common
+
+/** Utility function to make it easy to declare byte arrays */
+fun byteArrayOfInts(vararg ints: Int) = ByteArray(ints.size) { pos -> ints[pos].toByte() }
+
+fun xorHash(b: ByteArray) = b.fold(0) { acc, x -> acc xor (x.toInt() and BYTE_MASK) }
+
+private const val BYTE_MASK = 0xff

core/model/build.gradle.kts

@@ -31,6 +31,7 @@ android {
 }
 
 dependencies {
+    implementation(projects.core.common)
     implementation(projects.core.proto)
     implementation(projects.core.strings)
 

core/model/src/main/kotlin/org/meshtastic/core/model/Channel.kt

@@ -18,6 +18,8 @@
 package org.meshtastic.core.model
 
 import com.google.protobuf.ByteString
+import org.meshtastic.core.common.byteArrayOfInts
+import org.meshtastic.core.common.xorHash
 import org.meshtastic.proto.ChannelProtos
 import org.meshtastic.proto.ConfigKt.loRaConfig
 import org.meshtastic.proto.ConfigProtos
@@ -25,11 +27,6 @@ import org.meshtastic.proto.ConfigProtos.Config.LoRaConfig.ModemPreset
 import org.meshtastic.proto.channelSettings
 import java.security.SecureRandom
 
-/** Utility function to make it easy to declare byte arrays - FIXME move someplace better */
-fun byteArrayOfInts(vararg ints: Int) = ByteArray(ints.size) { pos -> ints[pos].toByte() }
-
-fun xorHash(b: ByteArray) = b.fold(0) { acc, x -> acc xor (x.toInt() and 0xff) }
-
 data class Channel(
     val settings: ChannelProtos.ChannelSettings = default.settings,
     val loraConfig: ConfigProtos.Config.LoRaConfig = default.loraConfig,