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Manu Herrera
2019-10-01 12:22:30 -03:00
parent 41e6aad190
commit d301c63596
915 changed files with 378049 additions and 11 deletions
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vendor/github.com/btcsuite/btcd/blockchain/compress.go generated vendored Normal file
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// Copyright (c) 2015-2016 The btcsuite developers
// Use of this source code is governed by an ISC
// license that can be found in the LICENSE file.
package blockchain
import (
"github.com/btcsuite/btcd/btcec"
"github.com/btcsuite/btcd/txscript"
)
// -----------------------------------------------------------------------------
// A variable length quantity (VLQ) is an encoding that uses an arbitrary number
// of binary octets to represent an arbitrarily large integer. The scheme
// employs a most significant byte (MSB) base-128 encoding where the high bit in
// each byte indicates whether or not the byte is the final one. In addition,
// to ensure there are no redundant encodings, an offset is subtracted every
// time a group of 7 bits is shifted out. Therefore each integer can be
// represented in exactly one way, and each representation stands for exactly
// one integer.
//
// Another nice property of this encoding is that it provides a compact
// representation of values that are typically used to indicate sizes. For
// example, the values 0 - 127 are represented with a single byte, 128 - 16511
// with two bytes, and 16512 - 2113663 with three bytes.
//
// While the encoding allows arbitrarily large integers, it is artificially
// limited in this code to an unsigned 64-bit integer for efficiency purposes.
//
// Example encodings:
// 0 -> [0x00]
// 127 -> [0x7f] * Max 1-byte value
// 128 -> [0x80 0x00]
// 129 -> [0x80 0x01]
// 255 -> [0x80 0x7f]
// 256 -> [0x81 0x00]
// 16511 -> [0xff 0x7f] * Max 2-byte value
// 16512 -> [0x80 0x80 0x00]
// 32895 -> [0x80 0xff 0x7f]
// 2113663 -> [0xff 0xff 0x7f] * Max 3-byte value
// 270549119 -> [0xff 0xff 0xff 0x7f] * Max 4-byte value
// 2^64-1 -> [0x80 0xfe 0xfe 0xfe 0xfe 0xfe 0xfe 0xfe 0xfe 0x7f]
//
// References:
// https://en.wikipedia.org/wiki/Variable-length_quantity
// http://www.codecodex.com/wiki/Variable-Length_Integers
// -----------------------------------------------------------------------------
// serializeSizeVLQ returns the number of bytes it would take to serialize the
// passed number as a variable-length quantity according to the format described
// above.
func serializeSizeVLQ(n uint64) int {
size := 1
for ; n > 0x7f; n = (n >> 7) - 1 {
size++
}
return size
}
// putVLQ serializes the provided number to a variable-length quantity according
// to the format described above and returns the number of bytes of the encoded
// value. The result is placed directly into the passed byte slice which must
// be at least large enough to handle the number of bytes returned by the
// serializeSizeVLQ function or it will panic.
func putVLQ(target []byte, n uint64) int {
offset := 0
for ; ; offset++ {
// The high bit is set when another byte follows.
highBitMask := byte(0x80)
if offset == 0 {
highBitMask = 0x00
}
target[offset] = byte(n&0x7f) | highBitMask
if n <= 0x7f {
break
}
n = (n >> 7) - 1
}
// Reverse the bytes so it is MSB-encoded.
for i, j := 0, offset; i < j; i, j = i+1, j-1 {
target[i], target[j] = target[j], target[i]
}
return offset + 1
}
// deserializeVLQ deserializes the provided variable-length quantity according
// to the format described above. It also returns the number of bytes
// deserialized.
func deserializeVLQ(serialized []byte) (uint64, int) {
var n uint64
var size int
for _, val := range serialized {
size++
n = (n << 7) | uint64(val&0x7f)
if val&0x80 != 0x80 {
break
}
n++
}
return n, size
}
// -----------------------------------------------------------------------------
// In order to reduce the size of stored scripts, a domain specific compression
// algorithm is used which recognizes standard scripts and stores them using
// less bytes than the original script. The compression algorithm used here was
// obtained from Bitcoin Core, so all credits for the algorithm go to it.
//
// The general serialized format is:
//
// <script size or type><script data>
//
// Field Type Size
// script size or type VLQ variable
// script data []byte variable
//
// The specific serialized format for each recognized standard script is:
//
// - Pay-to-pubkey-hash: (21 bytes) - <0><20-byte pubkey hash>
// - Pay-to-script-hash: (21 bytes) - <1><20-byte script hash>
// - Pay-to-pubkey**: (33 bytes) - <2, 3, 4, or 5><32-byte pubkey X value>
// 2, 3 = compressed pubkey with bit 0 specifying the y coordinate to use
// 4, 5 = uncompressed pubkey with bit 0 specifying the y coordinate to use
// ** Only valid public keys starting with 0x02, 0x03, and 0x04 are supported.
//
// Any scripts which are not recognized as one of the aforementioned standard
// scripts are encoded using the general serialized format and encode the script
// size as the sum of the actual size of the script and the number of special
// cases.
// -----------------------------------------------------------------------------
// The following constants specify the special constants used to identify a
// special script type in the domain-specific compressed script encoding.
//
// NOTE: This section specifically does not use iota since these values are
// serialized and must be stable for long-term storage.
const (
// cstPayToPubKeyHash identifies a compressed pay-to-pubkey-hash script.
cstPayToPubKeyHash = 0
// cstPayToScriptHash identifies a compressed pay-to-script-hash script.
cstPayToScriptHash = 1
// cstPayToPubKeyComp2 identifies a compressed pay-to-pubkey script to
// a compressed pubkey. Bit 0 specifies which y-coordinate to use
// to reconstruct the full uncompressed pubkey.
cstPayToPubKeyComp2 = 2
// cstPayToPubKeyComp3 identifies a compressed pay-to-pubkey script to
// a compressed pubkey. Bit 0 specifies which y-coordinate to use
// to reconstruct the full uncompressed pubkey.
cstPayToPubKeyComp3 = 3
// cstPayToPubKeyUncomp4 identifies a compressed pay-to-pubkey script to
// an uncompressed pubkey. Bit 0 specifies which y-coordinate to use
// to reconstruct the full uncompressed pubkey.
cstPayToPubKeyUncomp4 = 4
// cstPayToPubKeyUncomp5 identifies a compressed pay-to-pubkey script to
// an uncompressed pubkey. Bit 0 specifies which y-coordinate to use
// to reconstruct the full uncompressed pubkey.
cstPayToPubKeyUncomp5 = 5
// numSpecialScripts is the number of special scripts recognized by the
// domain-specific script compression algorithm.
numSpecialScripts = 6
)
// isPubKeyHash returns whether or not the passed public key script is a
// standard pay-to-pubkey-hash script along with the pubkey hash it is paying to
// if it is.
func isPubKeyHash(script []byte) (bool, []byte) {
if len(script) == 25 && script[0] == txscript.OP_DUP &&
script[1] == txscript.OP_HASH160 &&
script[2] == txscript.OP_DATA_20 &&
script[23] == txscript.OP_EQUALVERIFY &&
script[24] == txscript.OP_CHECKSIG {
return true, script[3:23]
}
return false, nil
}
// isScriptHash returns whether or not the passed public key script is a
// standard pay-to-script-hash script along with the script hash it is paying to
// if it is.
func isScriptHash(script []byte) (bool, []byte) {
if len(script) == 23 && script[0] == txscript.OP_HASH160 &&
script[1] == txscript.OP_DATA_20 &&
script[22] == txscript.OP_EQUAL {
return true, script[2:22]
}
return false, nil
}
// isPubKey returns whether or not the passed public key script is a standard
// pay-to-pubkey script that pays to a valid compressed or uncompressed public
// key along with the serialized pubkey it is paying to if it is.
//
// NOTE: This function ensures the public key is actually valid since the
// compression algorithm requires valid pubkeys. It does not support hybrid
// pubkeys. This means that even if the script has the correct form for a
// pay-to-pubkey script, this function will only return true when it is paying
// to a valid compressed or uncompressed pubkey.
func isPubKey(script []byte) (bool, []byte) {
// Pay-to-compressed-pubkey script.
if len(script) == 35 && script[0] == txscript.OP_DATA_33 &&
script[34] == txscript.OP_CHECKSIG && (script[1] == 0x02 ||
script[1] == 0x03) {
// Ensure the public key is valid.
serializedPubKey := script[1:34]
_, err := btcec.ParsePubKey(serializedPubKey, btcec.S256())
if err == nil {
return true, serializedPubKey
}
}
// Pay-to-uncompressed-pubkey script.
if len(script) == 67 && script[0] == txscript.OP_DATA_65 &&
script[66] == txscript.OP_CHECKSIG && script[1] == 0x04 {
// Ensure the public key is valid.
serializedPubKey := script[1:66]
_, err := btcec.ParsePubKey(serializedPubKey, btcec.S256())
if err == nil {
return true, serializedPubKey
}
}
return false, nil
}
// compressedScriptSize returns the number of bytes the passed script would take
// when encoded with the domain specific compression algorithm described above.
func compressedScriptSize(pkScript []byte) int {
// Pay-to-pubkey-hash script.
if valid, _ := isPubKeyHash(pkScript); valid {
return 21
}
// Pay-to-script-hash script.
if valid, _ := isScriptHash(pkScript); valid {
return 21
}
// Pay-to-pubkey (compressed or uncompressed) script.
if valid, _ := isPubKey(pkScript); valid {
return 33
}
// When none of the above special cases apply, encode the script as is
// preceded by the sum of its size and the number of special cases
// encoded as a variable length quantity.
return serializeSizeVLQ(uint64(len(pkScript)+numSpecialScripts)) +
len(pkScript)
}
// decodeCompressedScriptSize treats the passed serialized bytes as a compressed
// script, possibly followed by other data, and returns the number of bytes it
// occupies taking into account the special encoding of the script size by the
// domain specific compression algorithm described above.
func decodeCompressedScriptSize(serialized []byte) int {
scriptSize, bytesRead := deserializeVLQ(serialized)
if bytesRead == 0 {
return 0
}
switch scriptSize {
case cstPayToPubKeyHash:
return 21
case cstPayToScriptHash:
return 21
case cstPayToPubKeyComp2, cstPayToPubKeyComp3, cstPayToPubKeyUncomp4,
cstPayToPubKeyUncomp5:
return 33
}
scriptSize -= numSpecialScripts
scriptSize += uint64(bytesRead)
return int(scriptSize)
}
// putCompressedScript compresses the passed script according to the domain
// specific compression algorithm described above directly into the passed
// target byte slice. The target byte slice must be at least large enough to
// handle the number of bytes returned by the compressedScriptSize function or
// it will panic.
func putCompressedScript(target, pkScript []byte) int {
// Pay-to-pubkey-hash script.
if valid, hash := isPubKeyHash(pkScript); valid {
target[0] = cstPayToPubKeyHash
copy(target[1:21], hash)
return 21
}
// Pay-to-script-hash script.
if valid, hash := isScriptHash(pkScript); valid {
target[0] = cstPayToScriptHash
copy(target[1:21], hash)
return 21
}
// Pay-to-pubkey (compressed or uncompressed) script.
if valid, serializedPubKey := isPubKey(pkScript); valid {
pubKeyFormat := serializedPubKey[0]
switch pubKeyFormat {
case 0x02, 0x03:
target[0] = pubKeyFormat
copy(target[1:33], serializedPubKey[1:33])
return 33
case 0x04:
// Encode the oddness of the serialized pubkey into the
// compressed script type.
target[0] = pubKeyFormat | (serializedPubKey[64] & 0x01)
copy(target[1:33], serializedPubKey[1:33])
return 33
}
}
// When none of the above special cases apply, encode the unmodified
// script preceded by the sum of its size and the number of special
// cases encoded as a variable length quantity.
encodedSize := uint64(len(pkScript) + numSpecialScripts)
vlqSizeLen := putVLQ(target, encodedSize)
copy(target[vlqSizeLen:], pkScript)
return vlqSizeLen + len(pkScript)
}
// decompressScript returns the original script obtained by decompressing the
// passed compressed script according to the domain specific compression
// algorithm described above.
//
// NOTE: The script parameter must already have been proven to be long enough
// to contain the number of bytes returned by decodeCompressedScriptSize or it
// will panic. This is acceptable since it is only an internal function.
func decompressScript(compressedPkScript []byte) []byte {
// In practice this function will not be called with a zero-length or
// nil script since the nil script encoding includes the length, however
// the code below assumes the length exists, so just return nil now if
// the function ever ends up being called with a nil script in the
// future.
if len(compressedPkScript) == 0 {
return nil
}
// Decode the script size and examine it for the special cases.
encodedScriptSize, bytesRead := deserializeVLQ(compressedPkScript)
switch encodedScriptSize {
// Pay-to-pubkey-hash script. The resulting script is:
// <OP_DUP><OP_HASH160><20 byte hash><OP_EQUALVERIFY><OP_CHECKSIG>
case cstPayToPubKeyHash:
pkScript := make([]byte, 25)
pkScript[0] = txscript.OP_DUP
pkScript[1] = txscript.OP_HASH160
pkScript[2] = txscript.OP_DATA_20
copy(pkScript[3:], compressedPkScript[bytesRead:bytesRead+20])
pkScript[23] = txscript.OP_EQUALVERIFY
pkScript[24] = txscript.OP_CHECKSIG
return pkScript
// Pay-to-script-hash script. The resulting script is:
// <OP_HASH160><20 byte script hash><OP_EQUAL>
case cstPayToScriptHash:
pkScript := make([]byte, 23)
pkScript[0] = txscript.OP_HASH160
pkScript[1] = txscript.OP_DATA_20
copy(pkScript[2:], compressedPkScript[bytesRead:bytesRead+20])
pkScript[22] = txscript.OP_EQUAL
return pkScript
// Pay-to-compressed-pubkey script. The resulting script is:
// <OP_DATA_33><33 byte compressed pubkey><OP_CHECKSIG>
case cstPayToPubKeyComp2, cstPayToPubKeyComp3:
pkScript := make([]byte, 35)
pkScript[0] = txscript.OP_DATA_33
pkScript[1] = byte(encodedScriptSize)
copy(pkScript[2:], compressedPkScript[bytesRead:bytesRead+32])
pkScript[34] = txscript.OP_CHECKSIG
return pkScript
// Pay-to-uncompressed-pubkey script. The resulting script is:
// <OP_DATA_65><65 byte uncompressed pubkey><OP_CHECKSIG>
case cstPayToPubKeyUncomp4, cstPayToPubKeyUncomp5:
// Change the leading byte to the appropriate compressed pubkey
// identifier (0x02 or 0x03) so it can be decoded as a
// compressed pubkey. This really should never fail since the
// encoding ensures it is valid before compressing to this type.
compressedKey := make([]byte, 33)
compressedKey[0] = byte(encodedScriptSize - 2)
copy(compressedKey[1:], compressedPkScript[1:])
key, err := btcec.ParsePubKey(compressedKey, btcec.S256())
if err != nil {
return nil
}
pkScript := make([]byte, 67)
pkScript[0] = txscript.OP_DATA_65
copy(pkScript[1:], key.SerializeUncompressed())
pkScript[66] = txscript.OP_CHECKSIG
return pkScript
}
// When none of the special cases apply, the script was encoded using
// the general format, so reduce the script size by the number of
// special cases and return the unmodified script.
scriptSize := int(encodedScriptSize - numSpecialScripts)
pkScript := make([]byte, scriptSize)
copy(pkScript, compressedPkScript[bytesRead:bytesRead+scriptSize])
return pkScript
}
// -----------------------------------------------------------------------------
// In order to reduce the size of stored amounts, a domain specific compression
// algorithm is used which relies on there typically being a lot of zeroes at
// end of the amounts. The compression algorithm used here was obtained from
// Bitcoin Core, so all credits for the algorithm go to it.
//
// While this is simply exchanging one uint64 for another, the resulting value
// for typical amounts has a much smaller magnitude which results in fewer bytes
// when encoded as variable length quantity. For example, consider the amount
// of 0.1 BTC which is 10000000 satoshi. Encoding 10000000 as a VLQ would take
// 4 bytes while encoding the compressed value of 8 as a VLQ only takes 1 byte.
//
// Essentially the compression is achieved by splitting the value into an
// exponent in the range [0-9] and a digit in the range [1-9], when possible,
// and encoding them in a way that can be decoded. More specifically, the
// encoding is as follows:
// - 0 is 0
// - Find the exponent, e, as the largest power of 10 that evenly divides the
// value up to a maximum of 9
// - When e < 9, the final digit can't be 0 so store it as d and remove it by
// dividing the value by 10 (call the result n). The encoded value is thus:
// 1 + 10*(9*n + d-1) + e
// - When e==9, the only thing known is the amount is not 0. The encoded value
// is thus:
// 1 + 10*(n-1) + e == 10 + 10*(n-1)
//
// Example encodings:
// (The numbers in parenthesis are the number of bytes when serialized as a VLQ)
// 0 (1) -> 0 (1) * 0.00000000 BTC
// 1000 (2) -> 4 (1) * 0.00001000 BTC
// 10000 (2) -> 5 (1) * 0.00010000 BTC
// 12345678 (4) -> 111111101(4) * 0.12345678 BTC
// 50000000 (4) -> 47 (1) * 0.50000000 BTC
// 100000000 (4) -> 9 (1) * 1.00000000 BTC
// 500000000 (5) -> 49 (1) * 5.00000000 BTC
// 1000000000 (5) -> 10 (1) * 10.00000000 BTC
// -----------------------------------------------------------------------------
// compressTxOutAmount compresses the passed amount according to the domain
// specific compression algorithm described above.
func compressTxOutAmount(amount uint64) uint64 {
// No need to do any work if it's zero.
if amount == 0 {
return 0
}
// Find the largest power of 10 (max of 9) that evenly divides the
// value.
exponent := uint64(0)
for amount%10 == 0 && exponent < 9 {
amount /= 10
exponent++
}
// The compressed result for exponents less than 9 is:
// 1 + 10*(9*n + d-1) + e
if exponent < 9 {
lastDigit := amount % 10
amount /= 10
return 1 + 10*(9*amount+lastDigit-1) + exponent
}
// The compressed result for an exponent of 9 is:
// 1 + 10*(n-1) + e == 10 + 10*(n-1)
return 10 + 10*(amount-1)
}
// decompressTxOutAmount returns the original amount the passed compressed
// amount represents according to the domain specific compression algorithm
// described above.
func decompressTxOutAmount(amount uint64) uint64 {
// No need to do any work if it's zero.
if amount == 0 {
return 0
}
// The decompressed amount is either of the following two equations:
// x = 1 + 10*(9*n + d - 1) + e
// x = 1 + 10*(n - 1) + 9
amount--
// The decompressed amount is now one of the following two equations:
// x = 10*(9*n + d - 1) + e
// x = 10*(n - 1) + 9
exponent := amount % 10
amount /= 10
// The decompressed amount is now one of the following two equations:
// x = 9*n + d - 1 | where e < 9
// x = n - 1 | where e = 9
n := uint64(0)
if exponent < 9 {
lastDigit := amount%9 + 1
amount /= 9
n = amount*10 + lastDigit
} else {
n = amount + 1
}
// Apply the exponent.
for ; exponent > 0; exponent-- {
n *= 10
}
return n
}
// -----------------------------------------------------------------------------
// Compressed transaction outputs consist of an amount and a public key script
// both compressed using the domain specific compression algorithms previously
// described.
//
// The serialized format is:
//
// <compressed amount><compressed script>
//
// Field Type Size
// compressed amount VLQ variable
// compressed script []byte variable
// -----------------------------------------------------------------------------
// compressedTxOutSize returns the number of bytes the passed transaction output
// fields would take when encoded with the format described above.
func compressedTxOutSize(amount uint64, pkScript []byte) int {
return serializeSizeVLQ(compressTxOutAmount(amount)) +
compressedScriptSize(pkScript)
}
// putCompressedTxOut compresses the passed amount and script according to their
// domain specific compression algorithms and encodes them directly into the
// passed target byte slice with the format described above. The target byte
// slice must be at least large enough to handle the number of bytes returned by
// the compressedTxOutSize function or it will panic.
func putCompressedTxOut(target []byte, amount uint64, pkScript []byte) int {
offset := putVLQ(target, compressTxOutAmount(amount))
offset += putCompressedScript(target[offset:], pkScript)
return offset
}
// decodeCompressedTxOut decodes the passed compressed txout, possibly followed
// by other data, into its uncompressed amount and script and returns them along
// with the number of bytes they occupied prior to decompression.
func decodeCompressedTxOut(serialized []byte) (uint64, []byte, int, error) {
// Deserialize the compressed amount and ensure there are bytes
// remaining for the compressed script.
compressedAmount, bytesRead := deserializeVLQ(serialized)
if bytesRead >= len(serialized) {
return 0, nil, bytesRead, errDeserialize("unexpected end of " +
"data after compressed amount")
}
// Decode the compressed script size and ensure there are enough bytes
// left in the slice for it.
scriptSize := decodeCompressedScriptSize(serialized[bytesRead:])
if len(serialized[bytesRead:]) < scriptSize {
return 0, nil, bytesRead, errDeserialize("unexpected end of " +
"data after script size")
}
// Decompress and return the amount and script.
amount := decompressTxOutAmount(compressedAmount)
script := decompressScript(serialized[bytesRead : bytesRead+scriptSize])
return amount, script, bytesRead + scriptSize, nil
}