node-haystack Episode 6: Data Structure And Constants

来源：互联网发布：蓝桥物流软件编辑：程序博客网时间：2024/05/31 18:56

The structure of block could be(data field not included):

#pragma pack(push)#pragma pack(2) // Make sure the data aligning at 2bytes boundary    typedef struct {        u128    key;        u32     cookie;        u16     tag;        u16     flag;        u32     size;        u32     checkSum;    } block_info_t;#pragma pack(pop)

And the element of index hash looks like:

typedef struct {    u128    key;    u32 cookie;    u16 tag;    u16 flag;    u32 size;    u64 pos;} block_index_value_t;using blk_idx_val_t = block_index_value_t;using block_index_map_t = unordered_map<std::string, blk_idx_val_t>;using bidx_map_t = block_index_map_t;

Some crucial constants:

const u32   MAX_ERROR = 128; /*!< Max errors can be tolerated. */const size_t PARSE_QUEUE_LEN = 8192;    /*!< Quele length for paseing blocks. */const size_t READ_BUFFER_SIZE = 128 * 1024 * 1024; /*!< Read buffer size. */const static bfs::fstream::openmode FILE_MODE= bfs::fstream::in | bfs::fstream::out | bfs::fstream::binary; /*!< Default open mode for volume. */// File magic numbersstatic const u64 MAGIC_NUM_VOLUME = 0x6b63617453796148; //!< Magic number of volume, equals { 'H', 'a', 'y', 'S', 't', 'a', 'c', 'k' };static const u32 MAGIC_NUM_HEADER = 0x53796148; //!< Magic number of block header, equals { 'H', 'a', 'y', 'S' };static const u32 MAGIC_NUM_FOOTER = 0x6b636174; //!< Magic number of block footer, equals { 't', 'a', 'c', 'k' };const u16 FLAG_NORMAL = 0x0000; //!< Flag value for normal block.const u16 FLAG_REMOVE = 0x0001; //!< Falg value for deleted block.const u8 PADDING_VALUE[7] = { 0xCC, 0xCC, 0xCC, 0xCC, 0xCC, 0xCC, 0xCC };   //!< Bytes for padding filling.

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