Remove null terminator from Base38 String in kotlin (#27578)

* Remove null terminator from  Base38 String in kotlin

* Override the equals method from the Any class

src/controller/java/src/chip/onboardingpayload/Base38.kt

@@ -54,7 +54,7 @@ fun base38Encode(inBuf: ByteArray, outBuf: CharArray): Unit {
 
     val base38CharactersNeeded = kBase38CharactersNeededInNBytesChunk[bytesInChunk - 1].toByte()
 
-    if ((outIdx + base38CharactersNeeded) >= outBuf.size) {
+    if ((outIdx + base38CharactersNeeded) > outBuf.size) {
       throw OnboardingPayloadException("Buffer is too small")
     }
 
@@ -63,12 +63,6 @@ fun base38Encode(inBuf: ByteArray, outBuf: CharArray): Unit {
       value /= kRadix.toInt()
     }
   }
-
-  if (outIdx < outBuf.size) {
-    outBuf[outIdx] = '\u0000'
-  } else {
-    throw OnboardingPayloadException("Buffer is too small")
-  }
 }
 
 /*

src/controller/java/src/chip/onboardingpayload/OnboardingPayload.kt

@@ -143,6 +143,20 @@ class OnboardingPayload(
     setupPinCode
   )
 
+  override fun equals(other: Any?): Boolean {
+    if (this === other) return true
+    if (other !is OnboardingPayload) return false
+
+    return version == other.version &&
+            vendorId == other.vendorId &&
+            productId == other.productId &&
+            commissioningFlow == other.commissioningFlow &&
+            discoveryCapabilities == other.discoveryCapabilities &&
+            discriminator == other.discriminator &&
+            hasShortDiscriminator == other.hasShortDiscriminator &&
+            setupPinCode == other.setupPinCode
+  }
+
   fun addOptionalQRCodeInfo(info: OptionalQRCodeInfo) {
     optionalQRCodeInfo[info.tag] = info
   }

src/controller/java/src/chip/onboardingpayload/QRCodeBasicOnboardingPayloadGenerator.kt

@@ -18,6 +18,7 @@
 package chip.onboardingpayload
 
 import java.lang.StringBuilder
+import java.util.concurrent.atomic.AtomicInteger
 
 /**
  * A minimal QR code setup payload generator that omits any optional data,
@@ -27,7 +28,7 @@ class QRCodeBasicOnboardingPayloadGenerator(private val payload: OnboardingPaylo
 
   /**
    * This function is called to encode the binary data of a payload to a
-   * base38 null-terminated string.
+   * base38 string.
    *
    * The resulting size of the outBuffer span will be the size of data written.
    *
@@ -63,7 +64,9 @@ fun payloadBase38RepresentationWithTLV(
     throw OnboardingPayloadException("Buffer is too small")
   } else {
     val subBuffer = outBuffer.copyOfRange(prefixLen, outBuffer.size)
-    kQRCodePrefix.toCharArray(outBuffer, 0, prefixLen)
+    for (i in kQRCodePrefix.indices) {
+      outBuffer[i] = kQRCodePrefix[i]
+    }
 
     base38Encode(bits, subBuffer)
 
@@ -81,7 +84,7 @@ private fun generateBitSet(
   tlvDataStart: ByteArray?,
   tlvDataLengthInBytes: Int
 ) {
-  var offset = 0
+  var offset: AtomicInteger = AtomicInteger(0)
   val totalPayloadSizeInBits = kTotalPayloadDataSizeInBits + (tlvDataLengthInBytes * 8)
   if (bits.size * 8 < totalPayloadSizeInBits)
     throw OnboardingPayloadException("Buffer is too small")
@@ -100,18 +103,19 @@ private fun generateBitSet(
 // Populates numberOfBits starting from LSB of input into bits, which is assumed to be zero-initialized
 private fun populateBits(
   bits: ByteArray,
-  offset: Int,
+  offset: AtomicInteger,
   input: Long,
   numberOfBits: Int,
   totalPayloadDataSizeInBits: Int
 ) {
-  if (offset + numberOfBits > totalPayloadDataSizeInBits)
+  if (offset.get() + numberOfBits > totalPayloadDataSizeInBits)
     throw OnboardingPayloadException("Invalid argument")
 
   if (input >= (1L shl numberOfBits))
     throw OnboardingPayloadException("Invalid argument")
 
-  var index = offset
+  var index = offset.get()
+  offset.addAndGet(numberOfBits)
   var inputValue = input
   while (inputValue != 0L) {
     if (inputValue and 1L != 0L) {
@@ -125,7 +129,7 @@ private fun populateBits(
 
 private fun populateTLVBits(
   bits: ByteArray,
-  offset: Int,
+  offset: AtomicInteger,
   tlvBuf: ByteArray?,
   tlvBufSizeInBytes: Int,
   totalPayloadDataSizeInBits: Int

src/controller/java/src/chip/onboardingpayload/QRCodeOnboardingPayloadGenerator.kt

@@ -111,12 +111,11 @@ class QRCodeOnboardingPayloadGenerator(private val onboardingPayload: Onboarding
     }
 
     var tlvDataLengthInBytes = generateTLVFromOptionalData(onboardingPayload, tlvDataStart, tlvDataStartSize)
-
     val bits = ByteArray(kTotalPayloadDataSizeInBytes + tlvDataLengthInBytes)
     val buffer = CharArray(base38EncodedLength(bits.size) + kQRCodePrefix.length)
     payloadBase38RepresentationWithTLV(onboardingPayload, buffer, bits, tlvDataStart, tlvDataLengthInBytes)
 
-    return buffer.toString()
+    return String(buffer)
   }
 
   private fun generateTLVFromOptionalData(