[truffle] Prefix file with our bytecode with a magic string

Raku · Jul 10, 2018 · d842cdc · d842cdc
1 parent 0daebf1
commit d842cdc
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Showing 3 changed files with 21 additions and 0 deletions.
diff --git a/src/vm/jvm/runtime/org/perl6/nqp/truffle/ByteCodeReader.java b/src/vm/jvm/runtime/org/perl6/nqp/truffle/ByteCodeReader.java
@@ -3,6 +3,7 @@
 import java.io.UnsupportedEncodingException;
 import java.nio.ByteBuffer;
 import java.nio.ByteOrder;
+import java.util.Arrays;
 
 public class ByteCodeReader {
     private ByteBuffer buffer;
@@ -31,6 +32,13 @@ public double readNum() {
         return buffer.getDouble();
     }
 
+    public boolean hasMagicString() {
+        if (buffer.remaining() < ByteCodeWriter.MAGIC.length) return false;
+        byte maybeMagic[] = new byte[ByteCodeWriter.MAGIC.length];
+        buffer.get(maybeMagic);
+        return Arrays.equals(maybeMagic, ByteCodeWriter.MAGIC);
+    }
+
     public String readStr() {
         int length = buffer.getInt();
         byte[] encoded = new byte[length];

diff --git a/src/vm/jvm/runtime/org/perl6/nqp/truffle/ByteCodeWriter.java b/src/vm/jvm/runtime/org/perl6/nqp/truffle/ByteCodeWriter.java
@@ -5,6 +5,7 @@
 import java.nio.ByteOrder;
 
 public class ByteCodeWriter {
+    static byte[] MAGIC = new byte[] {'T', 'R', 'U', 'F', 'F', 'L', 'E', '6', '\r', '\n'};
     private ByteBuffer buffer;
 
     ByteCodeWriter() {
@@ -29,6 +30,11 @@ private void growToHold(int required) {
         }
     }
 
+    public void writeMagicString() {
+        growToHold(MAGIC.length);
+        buffer.put(MAGIC);
+    }
+
     public void writeOpCode(int opCode) {
         growToHold(4);
         buffer.putInt(opCode);

diff --git a/src/vm/jvm/runtime/org/perl6/nqp/truffle/TruffleCompiler.java b/src/vm/jvm/runtime/org/perl6/nqp/truffle/TruffleCompiler.java
@@ -109,7 +109,10 @@ protected void childrenToByteCode(SixModelObject node, int from, ByteCodeWriter
 
     public void writeByteCode(SixModelObject tast, String output, ThreadContext tc) {
         ByteCodeWriter writer = new ByteCodeWriter();
+
+        writer.writeMagicString();
         writer.writeVersion(0);
+
         tastToByteCode(tast, writer, tc);
 
         try {
@@ -145,6 +148,10 @@ public void runByteCode(String input) {
             buffer.order(ByteOrder.LITTLE_ENDIAN);
 
             ByteCodeReader reader = new ByteCodeReader(buffer);
+
+            if (!reader.hasMagicString()) {
+                throw new RuntimeException("Bytecode stream corrupt (missing magic string)");
+            }
             long version = reader.readVersion();
 
             FrameDescriptor frameDescriptor = new FrameDescriptor();