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-rw-r--r--src/compressor.cpp185
1 files changed, 185 insertions, 0 deletions
diff --git a/src/compressor.cpp b/src/compressor.cpp
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+// 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;
+}