Data commit

Task/Bitcoin-address-validation/Dart/bitcoin-address-validation.dart

@@ -0,0 +1,99 @@
+import 'package:crypto/crypto.dart';
+
+class Bitcoin {
+  final String ALPHABET =
+      "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz";
+
+  List<int> bigIntToByteArray(BigInt data) {
+    String str;
+    bool neg = false;
+    if (data < BigInt.zero) {
+      str = (~data).toRadixString(16);
+      neg = true;
+    } else str = data.toRadixString(16);
+    int p = 0;
+    int len = str.length;
+
+    int blen = (len + 1) ~/ 2;
+    int boff = 0;
+    List bytes;
+    if (neg) {
+      if (len & 1 == 1) {
+        p = -1;
+      }
+      int byte0 = ~int.parse(str.substring(0, p + 2), radix: 16);
+      if (byte0 < -128) byte0 += 256;
+      if (byte0 >= 0) {
+        boff = 1;
+        bytes = new List<int>(blen + 1);
+        bytes[0] = -1;
+        bytes[1] = byte0;
+      } else {
+        bytes = new List<int>(blen);
+        bytes[0] = byte0;
+      }
+      for (int i = 1; i < blen; ++i) {
+        int byte = ~int.parse(str.substring(p + (i << 1), p + (i << 1) + 2),
+            radix: 16);
+        if (byte < -128) byte += 256;
+        bytes[i + boff] = byte;
+      }
+    } else {
+      if (len & 1 == 1) {
+        p = -1;
+      }
+      int byte0 = int.parse(str.substring(0, p + 2), radix: 16);
+      if (byte0 > 127) byte0 -= 256;
+      if (byte0 < 0) {
+        boff = 1;
+        bytes = new List<int>(blen + 1);
+        bytes[0] = 0;
+        bytes[1] = byte0;
+      } else {
+        bytes = new List<int>(blen);
+        bytes[0] = byte0;
+      }
+      for (int i = 1; i < blen; ++i) {
+        int byte =
+            int.parse(str.substring(p + (i << 1), p + (i << 1) + 2), radix: 16);
+        if (byte > 127) byte -= 256;
+        bytes[i + boff] = byte;
+      }
+    }
+    return bytes;
+  }
+
+  List<int> arrayCopy(bytes, srcOffset, result, destOffset, bytesLength) {
+    for (int i = srcOffset; i < bytesLength; i++) {
+      result[destOffset + i] = bytes[i];
+    }
+    return result;
+  }
+
+  List<int> decodeBase58To25Bytes(String input) {
+    BigInt number = BigInt.zero;
+    for (String t in input.split('')) {
+      int p = ALPHABET.indexOf(t);
+      if (p == (-1))
+        return null;
+      number = number * (BigInt.from(58)) + (BigInt.from(p));
+    }
+    List<int> result = new List<int>(24);
+    List<int> numBytes = bigIntToByteArray(number);
+    return arrayCopy(
+        numBytes, 0, result, result.length - numBytes.length, numBytes.length);
+  }
+
+  validateAddress(String address) {
+    List<int> decoded = new List.from(decodeBase58To25Bytes(address));
+    List<int> temp = new List<int>.from(decoded);
+    temp.insert(0, 0);
+    List<int> hash1 = sha256.convert(temp.sublist(0, 21)).bytes;
+    List<int> hash2 = sha256.convert(hash1).bytes;
+    if (hash2[0] != decoded[20] ||
+        hash2[1] != decoded[21] ||
+        hash2[2] != decoded[22] ||
+        hash2[3] != decoded[23]) return false;
+    return true;
+  }
+}