在blk文件中找寻目标块及交易示例

在blk文件中找寻目标块及交易示例

bitcoin所有得交易信息都以block的形式存放在文件中，存访文件名为blkxxxxx.dat，文件存放在blocks目录下。如测试网的block文件存放在testnet3\blocks目录下。

首先，设置当前数据主目录，

gArgs.SoftSetArg("-datadir",PATH);

其中PATH为主目录，可使用函数

GetDataDir()

来查看当前数据路径。
使用结构体CDiskBlockPos来存访block文件所在位置，其定义如下：

struct CDiskBlockPos
{
    int nFile;			// blk文件编号，如129，表示blk000129.dat
    unsigned int nPos;	// 文件指针偏移值

    ADD_SERIALIZE_METHODS;

    template <typename Stream, typename Operation>
    inline void SerializationOp(Stream& s, Operation ser_action) {
        READWRITE(VARINT(nFile));
        READWRITE(VARINT(nPos));
    }

    CDiskBlockPos() {
        SetNull();
    }

    CDiskBlockPos(int nFileIn, unsigned int nPosIn) {
        nFile = nFileIn;
        nPos = nPosIn;
    }

    friend bool operator==(const CDiskBlockPos &a, const CDiskBlockPos &b) {
        return (a.nFile == b.nFile && a.nPos == b.nPos);
    }

    friend bool operator!=(const CDiskBlockPos &a, const CDiskBlockPos &b) {
        return !(a == b);
    }

    void SetNull() { nFile = -1; nPos = 0; }
    bool IsNull() const { return (nFile == -1); }

    std::string ToString() const
    {
        return strprintf("CBlockDiskPos(nFile=%i, nPos=%i)", nFile, nPos);
    }

};

使用函数OpenBlockFile打开区块文件，定义如下：

/** Open a block file (blk?????.dat) */
FILE* OpenBlockFile(const CDiskBlockPos &pos, bool fReadOnly = false);

打开成功后，返回一个文件指针。

使用类CBufferedFile来读取文件内容，定义如下：

/** Non-refcounted RAII wrapper around a FILE* that implements a ring buffer to
 *  deserialize from. It guarantees the ability to rewind a given number of bytes.
 *
 *  Will automatically close the file when it goes out of scope if not null.
 *  If you need to close the file early, use file.fclose() instead of fclose(file).
 */
class CBufferedFile
{
private:
    const int nType;
    const int nVersion;

    FILE *src;            // source file
    uint64_t nSrcPos;     // how many bytes have been read from source
    uint64_t nReadPos;    // how many bytes have been read from this
    uint64_t nReadLimit;  // up to which position we're allowed to read
    uint64_t nRewind;     // how many bytes we guarantee to rewind
    std::vector<char> vchBuf; // the buffer

protected:
    // read data from the source to fill the buffer
    bool Fill() {
        unsigned int pos = nSrcPos % vchBuf.size();
        unsigned int readNow = vchBuf.size() - pos;
        unsigned int nAvail = vchBuf.size() - (nSrcPos - nReadPos) - nRewind;
        if (nAvail < readNow)
            readNow = nAvail;
        if (readNow == 0)
            return false;
        size_t nBytes = fread((void*)&vchBuf[pos], 1, readNow, src);
        if (nBytes == 0) {
            throw std::ios_base::failure(feof(src) ? "CBufferedFile::Fill: end of file" : "CBufferedFile::Fill: fread failed");
        } else {
            nSrcPos += nBytes;
            return true;
        }
    }

public:
    CBuffere