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/*
 * \file ngram_model_dmp.h DMP format for N-Gram models
 *
 * Author: David Huggins-Daines <dhuggins@cs.cmu.edu>
 */

#ifndef __NGRAM_MODEL_DMP_H__
#define __NGRAM_MODEL_DMP_H__

#include "sphinxbase/mmio.h"

#include "ngram_model_internal.h"
#include "lm3g_model.h"

/**
 * On-disk representation of bigrams.
 */
struct bigram_s {
    uint16 wid;	/**< Index of unigram entry for this.  (NOT dictionary id.) */
    uint16 prob2;	/**< Index into array of actual bigram probs */
    uint16 bo_wt2;	/**< Index into array of actual bigram backoff wts */
    uint16 trigrams;	/**< Index of 1st entry in lm_t.trigrams[],
			   RELATIVE TO its segment base (see lm3g_model.h) */
};

/**
 * On-disk representation of trigrams.
 *
 * As with bigrams, trigram prob info kept in a separate table for conserving
 * memory space.
 */
struct trigram_s {
    uint16 wid;	  /**< Index of unigram entry for this.  (NOT dictionary id.) */
    uint16 prob3; /**< Index into array of actual trigram probs */
};

/**
 * Subclass of ngram_model for DMP file reading.
 */
typedef struct ngram_model_dmp_s {
    ngram_model_t base;  /**< Base ngram_model_t structure */
    lm3g_model_t lm3g;   /**< Common lm3g_model_t structure */
    mmio_file_t *dump_mmap; /**< mmap() of dump file (or NULL if none) */
} ngram_model_dmp_t;

/**
 * Construct a DMP format model from a generic base model.
 *
 * Note: If base is already a DMP format model, this just calls
 * ngram_model_retain(), and any changes will also be made in the base
 * model.
 */
ngram_model_dmp_t *ngram_model_dmp_build(ngram_model_t *base);


#endif /*  __NGRAM_MODEL_DMP_H__ */