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Diffstat (limited to 'src/compressor.cpp')
| -rw-r--r-- | src/compressor.cpp | 185 |
1 files changed, 185 insertions, 0 deletions
diff --git a/src/compressor.cpp b/src/compressor.cpp new file mode 100644 index 0000000000..806175dd3e --- /dev/null +++ b/src/compressor.cpp @@ -0,0 +1,185 @@ +// Copyright (c) 2009-2010 Satoshi Nakamoto +// Copyright (c) 2009-2014 The Bitcoin developers +// Distributed under the MIT software license, see the accompanying +// file COPYING or http://www.opensource.org/licenses/mit-license.php. + +#include "compressor.h" + +#include "hash.h" +#include "key.h" +#include "script/standard.h" + +bool CScriptCompressor::IsToKeyID(CKeyID &hash) const +{ + if (script.size() == 25 && script[0] == OP_DUP && script[1] == OP_HASH160 + && script[2] == 20 && script[23] == OP_EQUALVERIFY + && script[24] == OP_CHECKSIG) { + memcpy(&hash, &script[3], 20); + return true; + } + return false; +} + +bool CScriptCompressor::IsToScriptID(CScriptID &hash) const +{ + if (script.size() == 23 && script[0] == OP_HASH160 && script[1] == 20 + && script[22] == OP_EQUAL) { + memcpy(&hash, &script[2], 20); + return true; + } + return false; +} + +bool CScriptCompressor::IsToPubKey(CPubKey &pubkey) const +{ + if (script.size() == 35 && script[0] == 33 && script[34] == OP_CHECKSIG + && (script[1] == 0x02 || script[1] == 0x03)) { + pubkey.Set(&script[1], &script[34]); + return true; + } + if (script.size() == 67 && script[0] == 65 && script[66] == OP_CHECKSIG + && script[1] == 0x04) { + pubkey.Set(&script[1], &script[66]); + return pubkey.IsFullyValid(); // if not fully valid, a case that would not be compressible + } + return false; +} + +bool CScriptCompressor::Compress(std::vector<unsigned char> &out) const +{ + CKeyID keyID; + if (IsToKeyID(keyID)) { + out.resize(21); + out[0] = 0x00; + memcpy(&out[1], &keyID, 20); + return true; + } + CScriptID scriptID; + if (IsToScriptID(scriptID)) { + out.resize(21); + out[0] = 0x01; + memcpy(&out[1], &scriptID, 20); + return true; + } + CPubKey pubkey; + if (IsToPubKey(pubkey)) { + out.resize(33); + memcpy(&out[1], &pubkey[1], 32); + if (pubkey[0] == 0x02 || pubkey[0] == 0x03) { + out[0] = pubkey[0]; + return true; + } else if (pubkey[0] == 0x04) { + out[0] = 0x04 | (pubkey[64] & 0x01); + return true; + } + } + return false; +} + +unsigned int CScriptCompressor::GetSpecialSize(unsigned int nSize) const +{ + if (nSize == 0 || nSize == 1) + return 20; + if (nSize == 2 || nSize == 3 || nSize == 4 || nSize == 5) + return 32; + return 0; +} + +bool CScriptCompressor::Decompress(unsigned int nSize, const std::vector<unsigned char> &in) +{ + switch(nSize) { + case 0x00: + script.resize(25); + script[0] = OP_DUP; + script[1] = OP_HASH160; + script[2] = 20; + memcpy(&script[3], &in[0], 20); + script[23] = OP_EQUALVERIFY; + script[24] = OP_CHECKSIG; + return true; + case 0x01: + script.resize(23); + script[0] = OP_HASH160; + script[1] = 20; + memcpy(&script[2], &in[0], 20); + script[22] = OP_EQUAL; + return true; + case 0x02: + case 0x03: + script.resize(35); + script[0] = 33; + script[1] = nSize; + memcpy(&script[2], &in[0], 32); + script[34] = OP_CHECKSIG; + return true; + case 0x04: + case 0x05: + unsigned char vch[33] = {}; + vch[0] = nSize - 2; + memcpy(&vch[1], &in[0], 32); + CPubKey pubkey(&vch[0], &vch[33]); + if (!pubkey.Decompress()) + return false; + assert(pubkey.size() == 65); + script.resize(67); + script[0] = 65; + memcpy(&script[1], pubkey.begin(), 65); + script[66] = OP_CHECKSIG; + return true; + } + return false; +} + +// Amount compression: +// * If the amount is 0, output 0 +// * first, divide the amount (in base units) by the largest power of 10 possible; call the exponent e (e is max 9) +// * if e<9, the last digit of the resulting number cannot be 0; store it as d, and drop it (divide by 10) +// * call the result n +// * output 1 + 10*(9*n + d - 1) + e +// * if e==9, we only know the resulting number is not zero, so output 1 + 10*(n - 1) + 9 +// (this is decodable, as d is in [1-9] and e is in [0-9]) + +uint64_t CTxOutCompressor::CompressAmount(uint64_t n) +{ + if (n == 0) + return 0; + int e = 0; + while (((n % 10) == 0) && e < 9) { + n /= 10; + e++; + } + if (e < 9) { + int d = (n % 10); + assert(d >= 1 && d <= 9); + n /= 10; + return 1 + (n*9 + d - 1)*10 + e; + } else { + return 1 + (n - 1)*10 + 9; + } +} + +uint64_t CTxOutCompressor::DecompressAmount(uint64_t x) +{ + // x = 0 OR x = 1+10*(9*n + d - 1) + e OR x = 1+10*(n - 1) + 9 + if (x == 0) + return 0; + x--; + // x = 10*(9*n + d - 1) + e + int e = x % 10; + x /= 10; + uint64_t n = 0; + if (e < 9) { + // x = 9*n + d - 1 + int d = (x % 9) + 1; + x /= 9; + // x = n + n = x*10 + d; + } else { + n = x+1; + } + while (e) { + n *= 10; + e--; + } + return n; +} |