diff options
Diffstat (limited to 'lm/filter/wrapper.hh')
-rw-r--r-- | lm/filter/wrapper.hh | 58 |
1 files changed, 58 insertions, 0 deletions
diff --git a/lm/filter/wrapper.hh b/lm/filter/wrapper.hh new file mode 100644 index 000000000..90b07a08f --- /dev/null +++ b/lm/filter/wrapper.hh @@ -0,0 +1,58 @@ +#ifndef LM_FILTER_WRAPPER_H__ +#define LM_FILTER_WRAPPER_H__ + +#include "util/string_piece.hh" + +#include <algorithm> +#include <string> +#include <vector> + +namespace lm { + +// Provide a single-output filter with the same interface as a +// multiple-output filter so clients code against one interface. +template <class Binary> class BinaryFilter { + public: + // Binary modes are just references (and a set) and it makes the API cleaner to copy them. + explicit BinaryFilter(Binary binary) : binary_(binary) {} + + template <class Iterator, class Output> void AddNGram(const Iterator &begin, const Iterator &end, const StringPiece &line, Output &output) { + if (binary_.PassNGram(begin, end)) + output.AddNGram(line); + } + + template <class Output> void AddNGram(const StringPiece &ngram, const StringPiece &line, Output &output) { + AddNGram(util::TokenIter<util::SingleCharacter, true>(ngram, ' '), util::TokenIter<util::SingleCharacter, true>::end(), line, output); + } + + void Flush() const {} + + private: + Binary binary_; +}; + +// Wrap another filter to pay attention only to context words +template <class FilterT> class ContextFilter { + public: + typedef FilterT Filter; + + explicit ContextFilter(Filter &backend) : backend_(backend) {} + + template <class Output> void AddNGram(const StringPiece &ngram, const StringPiece &line, Output &output) { + pieces_.clear(); + // TODO: this copy could be avoided by a lookahead iterator. + std::copy(util::TokenIter<util::SingleCharacter, true>(ngram, ' '), util::TokenIter<util::SingleCharacter, true>::end(), std::back_insert_iterator<std::vector<StringPiece> >(pieces_)); + backend_.AddNGram(pieces_.begin(), pieces_.end() - !pieces_.empty(), line, output); + } + + void Flush() const {} + + private: + std::vector<StringPiece> pieces_; + + Filter backend_; +}; + +} // namespace lm + +#endif // LM_FILTER_WRAPPER_H__ |