begin to write class FlexibleBigram

1 files changed, 123 insertions, 0 deletions

diff --git a/src/storage/flexible_ngram_kyotodb.h b/src/storage/flexible_ngram_kyotodb.h
index ed8bc2a..9cf866b 100644
--- a/src/storage/flexible_ngram_kyotodb.h
+++ b/src/storage/flexible_ngram_kyotodb.h
@@ -26,7 +26,130 @@
 #include <kcdb.h>
 #endif
 
+#include "memory_chunk.h"
+
 namespace pinyin{
+
+/**
+ * FlexibleBigram:
+ * @MagicHeader: the struct type of the magic header.
+ * @ArrayHeader: the struct type of the array header.
+ * @ArrayItem: the struct type of the array item.
+ *
+ * The flexible bi-gram is mainly used for training purpose.
+ *
+ */
+template<typename MagicHeader, typename ArrayHeader,
+         typename ArrayItem>
+class FlexibleBigram{
+    using kyotocabinet::BasicDB;
+
+    /* Note: some flexible bi-gram file format check should be here. */
+private:
+    BasicDB * m_db;
+
+    MemoryChunk m_chunk;
+
+    phrase_token_t m_magic_header_index[2];
+
+    char m_magic_number[4];
+
+    void reset(){
+        if ( m_db ){
+            m_db->synchronize();
+            m_db->close();
+            m_db = NULL;
+        }
+    }
+
+public:
+    /**
+     * FlexibleBigram::FlexibleBigram:
+     * @magic_number: the 4 bytes magic number of the flexible bi-gram.
+     *
+     * The constructor of the FlexibleBigram.
+     *
+     */
+    FlexibleBigram(const char * magic_number){
+        m_db = NULL;
+        m_magic_header_index[0] = null_token;
+        m_magic_header_index[1] = null_token;
+
+        memcpy(m_magic_number, magic_number, sizeof(m_magic_number));
+    }
+
+    /**
+     * FlexibleBigram::~FlexibleBigram:
+     *
+     * The destructor of the FlexibleBigram.
+     *
+     */
+    ~FlexibleBigram(){
+        reset();
+    }
+
+    /**
+     * FlexibleBigram::attach:
+     * @dbfile: the path name of the flexible bi-gram.
+     * @flags: the attach flags for the Berkeley DB.
+     * @returns: whether the attach operation is successful.
+     *
+     * Attach Berkeley DB on filesystem for training purpose.
+     *
+     */
+    bool attach(const char * dbfile, guint32 flags){
+        reset();
+        uint32_t mode = 0;
+
+        if (flags & ATTACH_READONLY)
+            mode |= BasicDB::OREADER;
+        if (flags & ATTACH_READWRITE) {
+            assert( !( flags & ATTACH_READONLY ) );
+            mode |= BasicDB::OREADER | BasicDB::OWRITER;
+        }
+
+        if (!dbfile)
+            return false;
+
+        m_db = new HashDB;
+
+        if (!m_db->open(dbfile, mode)) {
+            if (!(flags & ATTACH_CREATE)) {
+                delete m_db;
+                m_db = NULL;
+                return false;
+            }
+
+            mode |= BasicDB::OCREATE;
+            /* Create database file here, and write the signature. */
+            if (!m_db->open(dbfile, mode))
+                return false;
+
+            const char * kbuf = (char *) m_magic_header_index;
+            const size_t ksiz = sizeof(m_magic_header_index);
+            const char * vbuf = (char *) m_magic_number;
+            const size_t vsiz = sizeof(m_magic_number);
+            m_db->set(kbuf, ksiz, vbuf, vsiz);
+            return true;
+        }
+
+        /* check the signature. */
+        const char * kbuf = (char *) m_magic_header_index;
+        const size_t ksiz = sizeof(m_magic_header_index);
+        const int32_t vsiz = m_db->check(kbuf, ksiz);
+
+        m_chunk.set_size(vsiz);
+        char * vbuf = (char *) m_chunk.begin();
+        assert (vsiz == m_db->get(kbuf, sizeof(phrase_token_t),
+                                  vbuf, vsiz));
+
+        if ( memcmp(vbuf, m_magic_number,
+                    sizeof(m_magic_number)) == 0 )
+            return true;
+        return false;
+    }
+};
+
 };
 
 #endif