1bab947596
The functions for generating transaction and block hashes contained a few error checks for conditions which could never fail without run-time panics. This commit removes those superfluous checks and adds explanatory comments.
122 lines
3.5 KiB
Go
122 lines
3.5 KiB
Go
// Copyright (c) 2013 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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// TxnCount (varInt) + PrevBlock and MerkleRoot hashes.
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const maxBlockHeaderPayload = 16 + maxVarIntPayload + (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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// Number of transactions in the block. For the bitcoin headers
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// (MsgHeaders) message, this must be 0. This is encoded as a variable
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// length integer on the wire.
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TxnCount uint64
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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(pver uint32) (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, pver, 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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// 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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TxnCount: 0,
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}
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}
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// readBlockHeader reads a bitcoin block header from r.
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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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count, err := readVarInt(r, pver)
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if err != nil {
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return err
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}
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bh.TxnCount = count
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return nil
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}
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// writeBlockHeader writes a bitcoin block header to w.
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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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err = writeVarInt(w, pver, bh.TxnCount)
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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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