transaction and script parsing improvements

src/main/java/com/sparrowwallet/drongo/protocol/Script.java

@@ -23,8 +23,14 @@ public class Script {
     protected byte[] program;
 
     public Script(byte[] programBytes) {
+        this(programBytes, true);
+    }
+
+    Script(byte[] programBytes, boolean parse) {
         program = programBytes;
-        parse(programBytes);
+        if(parse) {
+            parse();
+        }
     }
 
     public Script(List<ScriptChunk> chunks) {
@@ -38,7 +44,7 @@ public class Script {
             new ScriptChunk(ScriptOpCodes.OP_CHECKSIG, null, 24),
     };
 
-    private void parse(byte[] program) {
+    void parse() {
         chunks = new ArrayList<>(5);   // Common size.
         ByteArrayInputStream bis = new ByteArrayInputStream(program);
         int initialSize = bis.available();

src/main/java/com/sparrowwallet/drongo/protocol/ScriptChunk.java

@@ -110,12 +110,18 @@ public class ScriptChunk {
         }
 
         try {
-            new Script(data);
+            Script script = new Script(data);
+            //Flaky: Test if contains a non-zero opcode, otherwise not a script
+            for(ScriptChunk chunk : script.getChunks()) {
+                if(chunk.getOpcode() != OP_0) {
+                    return true;
+                }
+            }
         } catch(ProtocolException e) {
             return false;
         }
 
-        return true;
+        return false;
     }
 
     public Script getScript() {

src/main/java/com/sparrowwallet/drongo/protocol/ScriptOpCodes.java

@@ -291,25 +291,25 @@ public class ScriptOpCodes {
     }
 
     /**
-     * Converts the given OpCode into a string (eg "0", "PUSHDATA", or "NON_OP(10)")
+     * Converts the given OpCode into a string (eg "0", "PUSHDATA", or "RETURN_10")
      */
     public static String getOpCodeName(int opcode) {
         if (opCodeNameMap.containsKey((Integer)opcode)) {
             return opCodeNameMap.get(opcode);
         }
 
-        return "NON_OP(" + opcode + ")";
+        return "RETURN_" + opcode;
     }
 
     /**
-     * Converts the given pushdata OpCode into a string (eg "PUSHDATA2", or "PUSHDATA(23)")
+     * Converts the given pushdata OpCode into a string (eg "PUSHDATA_2", or "PUSHDATA_23")
      */
     public static String getPushDataName(int opcode) {
         if (opCodeNameMap.containsKey(opcode)) {
             return opCodeNameMap.get(opcode);
         }
 
-        return "PUSHDATA(" + opcode + ")";
+        return "PUSHDATA_" + opcode;
     }
 
     /**

src/main/java/com/sparrowwallet/drongo/protocol/Transaction.java

@@ -320,6 +320,12 @@ public class Transaction extends TransactionPart {
         return inputs.size() == 1 && inputs.get(0).isCoinBase();
     }
 
+    public static boolean isTransaction(byte[] bytes) {
+        //Incomplete quick test
+        long version = Utils.readUint32(bytes, 0);
+        return version > 0 && version < 5;
+    }
+
     public Sha256Hash hashForSignature(int inputIndex, Script redeemScript, SigHash type, boolean anyoneCanPay) {
         int sigHash = TransactionSignature.calcSigHashValue(type, anyoneCanPay);
         return hashForSignature(inputIndex, redeemScript.getProgram(), (byte) sigHash);

src/main/java/com/sparrowwallet/drongo/protocol/TransactionInput.java

@@ -45,7 +45,17 @@ public class TransactionInput extends TransactionPart {
 
     public Script getScriptSig() {
         if(scriptSig == null) {
-            scriptSig = new Script(scriptBytes);
+            if(isCoinBase()) {
+                //ScriptSig may be invalid, attempt to parse
+                scriptSig = new Script(scriptBytes, false);
+                try {
+                    scriptSig.parse();
+                } catch (ProtocolException e) {
+                    scriptSig = new Script(scriptSig.getChunks());
+                }
+            } else {
+                scriptSig = new Script(scriptBytes);
+            }
         }
 
         return scriptSig;

src/main/java/com/sparrowwallet/drongo/psbt/PSBT.java

@@ -519,9 +519,15 @@ public class PSBT {
     }
 
     public static boolean isPSBT(byte[] b) {
-        ByteBuffer buffer = ByteBuffer.wrap(b);
-        int header = buffer.getInt();
-        return header == PSBT_MAGIC_INT;
+        try {
+            ByteBuffer buffer = ByteBuffer.wrap(b);
+            int header = buffer.getInt();
+            return header == PSBT_MAGIC_INT;
+        } catch (Exception e) {
+            //ignore
+        }
+
+        return false;
     }
 
     public static boolean isPSBT(String s) {