Performance improvements on the PoW miner

quartz/src/main/java/com/vitorpamplona/quartz/nip13Pow/miner/ByteArrayExt.kt

@@ -37,13 +37,3 @@ fun ByteArray.indexOf(sequence: ByteArray): Int {
     }
     return -1
 }
-
-fun ByteArray.set(
-    value: ByteArray,
-    startIndex: Int,
-) {
-    var index = startIndex
-    for (byte in value) {
-        this[index++] = byte
-    }
-}

quartz/src/main/java/com/vitorpamplona/quartz/nip13Pow/miner/PoWMiner.kt

@@ -32,8 +32,9 @@ class PoWMiner(
     val desiredPoW: Int,
 ) {
     val hasher = Sha256Hasher()
+    val emptyBytesForDesiredPoW = desiredPoW / 8
 
-    fun rank(byteArray: ByteArray) = PoWRankEvaluator.calculatePowRankOf(hasher.hash(byteArray))
+    fun reachedDesiredPoW(byteArray: ByteArray) = PoWRankEvaluator.atLeastPowRank(hasher.hash(byteArray), desiredPoW, emptyBytesForDesiredPoW)
 
     fun run() = runDigit(buffer.nonceStarts)
 
@@ -42,15 +43,17 @@ class PoWMiner(
             // replaces the background base by the nonce integers
             buffer.bytes[index] = testByte
 
-            if (rank(buffer.bytes) >= desiredPoW) return true
+            if (index + 1 < buffer.nonceEnds) {
-
+                if (runDigit(index + 1)) return true
-            if (index + 1 < buffer.nonceEnds && runDigit(index + 1)) return true
+            } else {
+                if (reachedDesiredPoW(buffer.bytes)) return true
+            }
         }
         return false
     }
 
     companion object {
-        private val STARTING_NONCE_SIZE = 5
+        private const val STARTING_NONCE_SIZE = 5
 
         // make sure these chars are not escaped by the JSON stringifier
         private val VALID_CHARS: List<Char> =

quartz/src/main/java/com/vitorpamplona/quartz/nip13Pow/miner/PoWRankEvaluator.kt

@@ -103,5 +103,18 @@ class PoWRankEvaluator {
             }
             return rank
         }
+
+        @JvmStatic
+        fun atLeastPowRank(
+            id: ByteArray,
+            minPoW: Int,
+            emptyBytes: Int,
+        ): Boolean {
+            for (index in 0 until emptyBytes) {
+                if (id[index] != R8) return false
+            }
+
+            return calculatePowRankOf(id) >= minPoW
+        }
     }
 }