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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; }
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__
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