track node state for smarter union

1 files changed, 36 insertions, 0 deletions

diff --git a/decoder/node_state_hash.h b/decoder/node_state_hash.h
new file mode 100644
index 00000000..cdc05877
--- /dev/null
+++ b/decoder/node_state_hash.h
@@ -0,0 +1,36 @@
+#ifndef _NODE_STATE_HASH_
+#define _NODE_STATE_HASH_
+
+#include <cassert>
+#include <cstring>
+#include "murmur_hash3.h"
+#include "ffset.h"
+
+namespace cdec {
+
+  struct FirstPassNode {
+    FirstPassNode(int cat, int i, int j, int pi, int pj) : lhs(cat), s(i), t(j), u(pi), v(pj) {}
+    int32_t lhs;
+    short s;
+    short t;
+    short u;
+    short v;
+  };
+
+  inline uint64_t HashNode(int cat, int i, int j, int pi, int pj) {
+    FirstPassNode fpn(cat, i, j, pi, pj);
+    return MurmurHash3_64(&fpn, sizeof(FirstPassNode), 2654435769U);
+  }
+
+  inline uint64_t HashNode(uint64_t old_hash, const FFState& state) {
+    uint8_t buf[1024];
+    std::memcpy(buf, &old_hash, sizeof(uint64_t));
+    assert(state.size() < (1024u - sizeof(uint64_t)));
+    std::memcpy(&buf[sizeof(uint64_t)], state.begin(), state.size());
+    return MurmurHash3_64(buf, sizeof(uint64_t) + state.size(), 2654435769U);
+  }
+
+}
+
+#endif
+