mirror of https://github.com/vbatts/merkle.git
95 lines
2.7 KiB
Go
95 lines
2.7 KiB
Go
package merkle
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import (
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"hash"
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"log"
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)
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// NewHash provides a hash.Hash to generate a merkle.Tree checksum, given a
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// HashMaker for the checksums of the blocks written and the blockSize of each
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// block per node in the tree.
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func NewHash(hm HashMaker, merkleBlockLength int) hash.Hash {
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mh := new(merkleHash)
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mh.blockSize = merkleBlockLength
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mh.hm = hm
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mh.tree = &Tree{Nodes: []*Node{}, BlockLength: merkleBlockLength}
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return mh
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}
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// TODO make a similar hash.Hash, that accepts an argument of a merkle.Tree,
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// that will validate nodes as the new bytes are written. If a new written
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// block fails checksum, then return an error on the io.Writer
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// TODO satisfy the hash.Hash interface
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type merkleHash struct {
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blockSize int
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tree *Tree
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hm HashMaker
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lastBlock []byte // as needed, for Sum()
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partialLastBlock bool
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}
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// XXX this will be tricky, as the last block can be less than the BlockSize.
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// if they get the sum, it will be mh.tree.Root().Checksum() at that point.
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//
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// But if they continue writing, it would mean a continuation of the bytes in
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// the last block. So popping the last node, and having a buffer for the bytes
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// in that last partial block.
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//
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// if that last block was complete, then no worries. start the next node.
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func (mh *merkleHash) Sum(b []byte) []byte {
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// TODO check if len(mh.lastBlock) < blockSize
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sum, err := mh.tree.Root().Checksum()
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if err != nil {
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log.Println(err)
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}
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return sum
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}
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func (mh *merkleHash) Write(b []byte) (int, error) {
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// basically we need to:
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// * chunk these writes into blockSize
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// * create Node of the sum
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// * add the Node to the tree
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// * stash remainder in the mh.lastBlock
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var (
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curBlock = make([]byte, mh.blockSize)
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numBytes int = 0
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numWritten int
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)
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if mh.lastBlock != nil && len(mh.lastBlock) > 0 {
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numBytes = copy(curBlock, mh.lastBlock)
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// not adding to numWritten, since these blocks were accounted for in a
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// prior Write()
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}
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if numBytes > 0 {
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copy(curBlock, b[:(mh.blockSize-numBytes)])
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numWritten += (mh.blockSize - numBytes)
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// TODO Node for curBlock
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n := NewNodeHashBlock(mh.hm, curBlock)
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_ = n
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}
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numBytes = len(b) - numBytes
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for i := 0; i < numBytes/mh.blockSize; i++ {
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// TODO Node for curBlock
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}
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// TODO stash (numBytes % mh.blockSize) in mh.lastBlock
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// TODO if len(mh.lastBlock) < blockSize, then set that before returning
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return numWritten, nil
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}
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func (mh *merkleHash) Reset() {
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mh.tree = &Tree{}
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mh.lastBlock = nil
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}
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// likely not the best to pass this through and not use our own node block
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// size, but let's revisit this.
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func (mh *merkleHash) BlockSize() int { return mh.hm().BlockSize() }
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func (mh *merkleHash) Size() int { return mh.hm().Size() }
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