[parser/crf] adding crf_trainer, which can be thought of as a "base class" as much as that's possible in C, for creating trainers for the CRF. It doesn't deal with the weights or their representation, just provides an interface for keeping track of string features and label names, and holds the crf_context

src/crf_trainer.h

@@ -0,0 +1,38 @@
+#ifndef CRF_TRAINER_H
+#define CRF_TRAINER_H
+
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "collections.h"
+#include "crf_context.h"
+#include "string_utils.h"
+#include "tokens.h"
+#include "trie.h"
+#include "trie_utils.h"
+
+typedef struct crf_trainer {
+    uint32_t num_classes;
+    khash_t(str_uint32) *features;
+    khash_t(str_uint32) *prev_tag_features;
+    khash_t(str_uint32) *classes;
+    cstring_array *class_strings;
+    crf_context_t *context;
+} crf_trainer_t;
+
+
+crf_trainer_t *crf_trainer_new(size_t num_classes);
+void crf_trainer_destroy(crf_trainer_t *self);
+
+bool crf_trainer_get_class_id(crf_trainer_t *self, char *class_name, uint32_t *class_id, bool add_if_missing);
+bool crf_trainer_hash_feature_to_id(crf_trainer_t *self, char *feature, uint32_t *feature_id);
+bool crf_trainer_hash_feature_to_id_exists(crf_trainer_t *self, char *feature, uint32_t *feature_id, bool *exists);
+
+bool crf_trainer_hash_prev_tag_feature_to_id(crf_trainer_t *self, char *feature, uint32_t *feature_id);
+bool crf_trainer_hash_prev_tag_feature_to_id_exists(crf_trainer_t *self, char *feature, uint32_t *feature_id, bool *exists);
+
+
+bool crf_trainer_get_feature_id(crf_trainer_t *self, char *feature, uint32_t *feature_id);
+bool crf_trainer_get_prev_tag_feature_id(crf_trainer_t *self, char *feature, uint32_t *feature_id);
+
+#endif