MOVEONLY: Move script/compressor out of script and put CTxOutCompressor (from

core) with it

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;
+}