06d1236d49
This commit introduces two new functions for Blockheader named Serialize and Deserialize. The functions provide a stable mechanism for serializing and deserializing block headers to and from disk. The main benefit here is deserialization of the header since typically only full blocks are serialized to disk. Then when a header is needed, only the header portion of the block is read and deserialized.
129 lines
4.3 KiB
Go
129 lines
4.3 KiB
Go
// Copyright (c) 2013-2014 Conformal Systems LLC.
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// Use of this source code is governed by an ISC
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// license that can be found in the LICENSE file.
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package btcwire
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import (
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"bytes"
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"io"
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"time"
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)
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// BlockVersion is the current latest supported block version.
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const BlockVersion uint32 = 2
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// Version 4 bytes + Timestamp 4 bytes + Bits 4 bytes + Nonce 4 bytes +
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// PrevBlock and MerkleRoot hashes.
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const maxBlockHeaderPayload = 16 + (HashSize * 2)
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// BlockHeader defines information about a block and is used in the bitcoin
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// block (MsgBlock) and headers (MsgHeaders) messages.
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type BlockHeader struct {
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// Version of the block. This is not the same as the protocol version.
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Version uint32
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// Hash of the previous block in the block chain.
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PrevBlock ShaHash
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// Merkle tree reference to hash of all transactions for the block.
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MerkleRoot ShaHash
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// Time the block was created. This is, unfortunately, encoded as a
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// uint32 on the wire and therefore is limited to 2106.
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Timestamp time.Time
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// Difficulty target for the block.
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Bits uint32
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// Nonce used to generate the block.
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Nonce uint32
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}
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// blockHashLen is a constant that represents how much of the block header is
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// used when computing the block sha 0:blockHashLen
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const blockHashLen = 80
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// BlockSha computes the block identifier hash for the given block header.
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func (h *BlockHeader) BlockSha() (ShaHash, error) {
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// Encode the header and run double sha256 everything prior to the
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// number of transactions. Ignore the error returns since there is no
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// way the encode could fail except being out of memory which would
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// cause a run-time panic. Also, SetBytes can't fail here due to the
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// fact DoubleSha256 always returns a []byte of the right size
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// regardless of input.
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var buf bytes.Buffer
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var sha ShaHash
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_ = writeBlockHeader(&buf, 0, h)
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_ = sha.SetBytes(DoubleSha256(buf.Bytes()[0:blockHashLen]))
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// Even though this function can't currently fail, it still returns
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// a potential error to help future proof the API should a failure
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// become possible.
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return sha, nil
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}
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// Deserialize decodes a block header from r into the receiver using a format
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// that is suitable for long-term storage such as a database while respecting
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// the Version field.
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func (h *BlockHeader) Deserialize(r io.Reader) error {
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// At the current time, there is no difference between the wire encoding
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// at protocol version 0 and the stable long-term storage format. As
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// a result, make use of readBlockHeader.
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return readBlockHeader(r, 0, h)
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}
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// Serialize encodes a block header from r into the receiver using a format
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// that is suitable for long-term storage such as a database while respecting
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// the Version field.
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func (h *BlockHeader) Serialize(w io.Writer) error {
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// At the current time, there is no difference between the wire encoding
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// at protocol version 0 and the stable long-term storage format. As
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// a result, make use of writeBlockHeader.
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return writeBlockHeader(w, 0, h)
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}
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// NewBlockHeader returns a new BlockHeader using the provided previous block
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// hash, merkle root hash, difficulty bits, and nonce used to generate the
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// block with defaults for the remaining fields.
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func NewBlockHeader(prevHash *ShaHash, merkleRootHash *ShaHash, bits uint32,
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nonce uint32) *BlockHeader {
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return &BlockHeader{
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Version: BlockVersion,
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PrevBlock: *prevHash,
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MerkleRoot: *merkleRootHash,
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Timestamp: time.Now(),
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Bits: bits,
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Nonce: nonce,
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}
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}
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// readBlockHeader reads a bitcoin block header from r. See Deserialize for
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// decoding block headers stored to disk, such as in a database, as opposed to
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// decoding from the wire.
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func readBlockHeader(r io.Reader, pver uint32, bh *BlockHeader) error {
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var sec uint32
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err := readElements(r, &bh.Version, &bh.PrevBlock, &bh.MerkleRoot, &sec,
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&bh.Bits, &bh.Nonce)
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if err != nil {
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return err
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}
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bh.Timestamp = time.Unix(int64(sec), 0)
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return nil
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}
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// writeBlockHeader writes a bitcoin block header to w. See Serialize for
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// encoding block headers to be stored to disk, such as in a database, as
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// opposed to encoding for the wire.
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func writeBlockHeader(w io.Writer, pver uint32, bh *BlockHeader) error {
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sec := uint32(bh.Timestamp.Unix())
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err := writeElements(w, bh.Version, &bh.PrevBlock, &bh.MerkleRoot,
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sec, bh.Bits, bh.Nonce)
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if err != nil {
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return err
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}
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return nil
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}
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