1 files changed, 84 insertions, 0 deletions
diff --git a/klm/lm/builder/ngram.hh b/klm/lm/builder/ngram.hh
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+++ b/klm/lm/builder/ngram.hh
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+#ifndef LM_BUILDER_NGRAM__
+#define LM_BUILDER_NGRAM__
+
+#include "lm/weights.hh"
+#include "lm/word_index.hh"
+
+#include <cstddef>
+
+#include <assert.h>
+#include <stdint.h>
+#include <string.h>
+
+namespace lm {
+namespace builder {
+
+struct Uninterpolated {
+  float prob;  // Uninterpolated probability.
+  float gamma; // Interpolation weight for lower order.
+};
+
+union Payload {
+  uint64_t count;
+  Uninterpolated uninterp;
+  ProbBackoff complete;
+};
+
+class NGram {
+  public:
+    NGram(void *begin, std::size_t order) 
+      : begin_(static_cast<WordIndex*>(begin)), end_(begin_ + order) {}
+
+    const uint8_t *Base() const { return reinterpret_cast<const uint8_t*>(begin_); }
+    uint8_t *Base() { return reinterpret_cast<uint8_t*>(begin_); }
+
+    void ReBase(void *to) {
+      std::size_t difference = end_ - begin_;
+      begin_ = reinterpret_cast<WordIndex*>(to);
+      end_ = begin_ + difference;
+    }
+
+    // Would do operator++ but that can get confusing for a stream.  
+    void NextInMemory() {
+      ReBase(&Value() + 1);
+    }
+
+    // Lower-case in deference to STL.  
+    const WordIndex *begin() const { return begin_; }
+    WordIndex *begin() { return begin_; }
+    const WordIndex *end() const { return end_; }
+    WordIndex *end() { return end_; }
+
+    const Payload &Value() const { return *reinterpret_cast<const Payload *>(end_); }
+    Payload &Value() { return *reinterpret_cast<Payload *>(end_); }
+
+    uint64_t &Count() { return Value().count; }
+    const uint64_t Count() const { return Value().count; }
+
+    std::size_t Order() const { return end_ - begin_; }
+
+    static std::size_t TotalSize(std::size_t order) {
+      return order * sizeof(WordIndex) + sizeof(Payload);
+    }
+    std::size_t TotalSize() const {
+      // Compiler should optimize this.  
+      return TotalSize(Order());
+    }
+    static std::size_t OrderFromSize(std::size_t size) {
+      std::size_t ret = (size - sizeof(Payload)) / sizeof(WordIndex);
+      assert(size == TotalSize(ret));
+      return ret;
+    }
+
+  private:
+    WordIndex *begin_, *end_;
+};
+
+const WordIndex kUNK = 0;
+const WordIndex kBOS = 1;
+const WordIndex kEOS = 2;
+
+} // namespace builder
+} // namespace lm
+
+#endif // LM_BUILDER_NGRAM__