1 files changed, 97 insertions, 0 deletions
diff --git a/klm/util/probing_hash_table.hh b/klm/util/probing_hash_table.hh
new file mode 100644
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+++ b/klm/util/probing_hash_table.hh
@@ -0,0 +1,97 @@
+#ifndef UTIL_PROBING_HASH_TABLE__
+#define UTIL_PROBING_HASH_TABLE__
+
+#include <algorithm>
+#include <cstddef>
+#include <functional>
+
+#include <assert.h>
+
+namespace util {
+
+/* Non-standard hash table
+ * Buckets must be set at the beginning and must be greater than maximum number
+ * of elements, else an infinite loop happens.
+ * Memory management and initialization is externalized to make it easier to
+ * serialize these to disk and load them quickly.
+ * Uses linear probing to find value.
+ * Only insert and lookup operations.  
+ */
+
+template <class PackingT, class HashT, class EqualT = std::equal_to<typename PackingT::Key> > class ProbingHashTable {
+  public:
+    typedef PackingT Packing;
+    typedef typename Packing::Key Key;
+    typedef typename Packing::MutableIterator MutableIterator;
+    typedef typename Packing::ConstIterator ConstIterator;
+
+    typedef HashT Hash;
+    typedef EqualT Equal;
+
+    static std::size_t Size(std::size_t entries, float multiplier) {
+      return std::max(entries + 1, static_cast<std::size_t>(multiplier * static_cast<float>(entries))) * Packing::kBytes;
+    }
+
+    // Must be assigned to later.  
+    ProbingHashTable()
+#ifdef DEBUG
+      : initialized_(false), entries_(0) 
+#endif
+    {}
+
+    ProbingHashTable(void *start, std::size_t allocated, const Key &invalid = Key(), const Hash &hash_func = Hash(), const Equal &equal_func = Equal())
+      : begin_(Packing::FromVoid(start)),
+        buckets_(allocated / Packing::kBytes),
+        end_(begin_ + (allocated / Packing::kBytes)),
+        invalid_(invalid),
+        hash_(hash_func),
+        equal_(equal_func) 
+#ifdef DEBUG
+        , initialized_(true),
+        entries_(0) 
+#endif
+    {}
+
+    template <class T> void Insert(const T &t) {
+#ifdef DEBUG
+      assert(initialized_);
+      assert(++entries_ < buckets_);
+#endif
+      for (MutableIterator i(begin_ + (hash_(t.GetKey()) % buckets_));;) {
+        if (equal_(i->GetKey(), invalid_)) { *i = t; return; }
+        if (++i == end_) { i = begin_; }
+      }
+    }
+
+    void FinishedInserting() {}
+
+    void LoadedBinary() {}
+
+    template <class Key> bool Find(const Key key, ConstIterator &out) const {
+#ifdef DEBUG
+      assert(initialized_);
+#endif
+      for (ConstIterator i(begin_ + (hash_(key) % buckets_));;) {
+        Key got(i->GetKey());
+        if (equal_(got, key)) { out = i; return true; }
+        if (equal_(got, invalid_)) { return false; }
+        if (++i == end_) { i = begin_; }
+      }    
+    }
+
+  private:
+    MutableIterator begin_;
+    std::size_t buckets_;
+    MutableIterator end_;
+    Key invalid_;
+    Hash hash_;
+    Equal equal_;
+#ifdef DEBUG
+    bool initialized_;
+    std::size_t entries_;
+#endif
+};
+
+} // namespace util
+
+#endif // UTIL_PROBING_HASH_TABLE__