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// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
/**
* @author Peter Boros
* @date 2004/12/17
* @version $Id$
* @file metadata.h
* @brief Generic metadata associated with perfect hash values. The
* data structutre is completely up to the user, but it is
* usually an array of fixed size records indexed by the
* perfect hash value, or it contains an index which maps the
* perfect hash values to variable size records.
*
*/
#pragma once
#include <stdlib.h>
#include "fsa.h"
namespace fsa {
// {{{ class MetaData
/**
* @class MetaData
* @brief Class for representing generic metadata.
*
* Generic metadata associated with perfect hash values. The data
* structutre is completely up to the user, but it is usually an array
* of fixed size records indexed by the perfect hash value, or it
* contains an index which maps the perfect hash values to variable
* size records.
*/
class MetaData {
public:
class Handle; // defined in metadatahandle.h
private:
static const uint32_t MAGIC = 0x873EA98B; /**< Magic number identifying metadata net files. */
static const FileAccessMethod _default_file_access_method = FILE_ACCESS_MMAP; /**< Default file access method (read/mmap). */
/**
* @struct Header
* @brief Concept net data file header.
*/
struct Header {
uint32_t _magic; /**< Magic number. */
uint32_t _version; /**< Version number. (currently not used) */
uint32_t _checksum; /**< Checksum. (currently not used) */
uint32_t _size; /**< Size of the data. */
uint32_t _reserved[10]; /**< Reserved for later use. */
uint32_t _user[50]; /**< User defined fields. */
};
void *_mmap_addr; /**< mmap address, NULL is file has not been mmapped. */
size_t _mmap_length; /**< mmap length. */
bool _ok; /**< Flag indicating successful initialization. */
Header _header;
void *_data;
/**
* @brief Reset the object.
*
* Resets the object to an empty %MetaData, and releases allocated memory.
*/
void reset();
/**
* @brief Read the metadata file from disk.
*
* @param datafile Name of the metadata file.
* @param fam File access mode (read or mmap). If not set, the
* global default access mode will be used.
* @return True on success.
*/
bool read(const char *datafile, FileAccessMethod fam = FILE_ACCESS_UNDEF);
/**
* @brief Unimplemented private default constructor.
*/
MetaData();
/**
* @brief Unimplemented private copy constructor.
*/
MetaData(const MetaData&);
/**
* @brief Unimplemented private assignment operator.
*/
const MetaData& operator=(const MetaData&);
public:
/**
* @brief Constructor.
*
* @param datafile Metadata file.
* @param fam File access mode (read or mmap). If not set, the
* global default access mode will be used.
*/
MetaData(const char *datafile, FileAccessMethod fam = FILE_ACCESS_UNDEF);
MetaData(const std::string &datafile, FileAccessMethod fam = FILE_ACCESS_UNDEF);
/**
* @brief Destructor.
*/
virtual ~MetaData();
/**
* @brief Check if initialization was successful.
*
* @return True if the initialization of the object succeeded.
*/
bool isOk() const
{
return _ok;
}
/**
* @brief Get user defined header field
*
* @param idx Field index
* @return Header field value.
*/
uint32_t user(unsigned int idx) const
{
if(_ok && idx<50)
return _header._user[idx];
else
return 0;
}
uint32_t getUIntEntry(uint32_t idx) const
{
if(_ok){
return ((const uint32_t*)_data)[idx];
}
else
return 0;
}
const void *getDirectRecordEntry(uint32_t idx, uint32_t size) const
{
if(_ok)
return (const void*)((const uint8_t*)_data+idx*size);
else
return NULL;
}
const void *getIndirectRecordEntry(uint32_t idx) const
{
if(_ok){
uint32_t offset=((const uint32_t*)_data)[idx];
return (const void*)((const uint8_t*)_data+offset);
}
else
return NULL;
}
const char *getCharPtrEntry(uint32_t offset) const
{
if(_ok)
return ((const char*)_data)+offset;
else
return NULL;
}
};
// }}}
} // namespace fsa
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