1 files changed, 47 insertions, 0 deletions
diff --git a/eth/tracers/internal/tracers/bigram_tracer.js b/eth/tracers/internal/tracers/bigram_tracer.js
new file mode 100644
index 0000000..421c360
--- /dev/null
+++ b/eth/tracers/internal/tracers/bigram_tracer.js
@@ -0,0 +1,47 @@
+// Copyright 2018 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+{
+    // hist is the counters of opcode bigrams
+    hist: {},
+    // lastOp is last operation
+    lastOp: '',
+    // execution depth of last op
+    lastDepth: 0,
+    // step is invoked for every opcode that the VM executes.
+    step: function(log, db) {
+        var op = log.op.toString();
+        var depth = log.getDepth();
+        if (depth == this.lastDepth){
+            var key = this.lastOp+'-'+op;
+            if (this.hist[key]){
+                this.hist[key]++;
+            }
+            else {
+                this.hist[key] = 1;
+            }
+        }
+        this.lastOp = op;
+        this.lastDepth = depth;
+    },
+    // fault is invoked when the actual execution of an opcode fails.
+    fault: function(log, db) {},
+    // result is invoked when all the opcodes have been iterated over and returns
+    // the final result of the tracing.
+    result: function(ctx) {
+        return this.hist;
+    },
+}