diff options
Diffstat (limited to 'src/uint256.h')
| -rw-r--r-- | src/uint256.h | 49 |
1 files changed, 26 insertions, 23 deletions
diff --git a/src/uint256.h b/src/uint256.h index 28de540226..56f7f44a16 100644 --- a/src/uint256.h +++ b/src/uint256.h @@ -1,6 +1,6 @@ // Copyright (c) 2009-2010 Satoshi Nakamoto // Copyright (c) 2009-2014 The Bitcoin developers -// Distributed under the MIT/X11 software license, see the accompanying +// Distributed under the MIT software license, see the accompanying // file COPYING or http://www.opensource.org/licenses/mit-license.php. #ifndef BITCOIN_UINT256_H @@ -255,8 +255,10 @@ public: return sizeof(pn); } - // Returns the position of the highest bit set plus one, or zero if the - // value is zero. + /** + * Returns the position of the highest bit set plus one, or zero if the + * value is zero. + */ unsigned int bits() const; uint64_t GetLow64() const @@ -301,26 +303,27 @@ public: uint256(uint64_t b) : base_uint<256>(b) {} explicit uint256(const std::string& str) : base_uint<256>(str) {} explicit uint256(const std::vector<unsigned char>& vch) : base_uint<256>(vch) {} - - // The "compact" format is a representation of a whole - // number N using an unsigned 32bit number similar to a - // floating point format. - // The most significant 8 bits are the unsigned exponent of base 256. - // This exponent can be thought of as "number of bytes of N". - // The lower 23 bits are the mantissa. - // Bit number 24 (0x800000) represents the sign of N. - // N = (-1^sign) * mantissa * 256^(exponent-3) - // - // Satoshi's original implementation used BN_bn2mpi() and BN_mpi2bn(). - // MPI uses the most significant bit of the first byte as sign. - // Thus 0x1234560000 is compact (0x05123456) - // and 0xc0de000000 is compact (0x0600c0de) - // (0x05c0de00) would be -0x40de000000 - // - // Bitcoin only uses this "compact" format for encoding difficulty - // targets, which are unsigned 256bit quantities. Thus, all the - // complexities of the sign bit and using base 256 are probably an - // implementation accident. + + /** + * The "compact" format is a representation of a whole + * number N using an unsigned 32bit number similar to a + * floating point format. + * The most significant 8 bits are the unsigned exponent of base 256. + * This exponent can be thought of as "number of bytes of N". + * The lower 23 bits are the mantissa. + * Bit number 24 (0x800000) represents the sign of N. + * N = (-1^sign) * mantissa * 256^(exponent-3) + * + * Satoshi's original implementation used BN_bn2mpi() and BN_mpi2bn(). + * MPI uses the most significant bit of the first byte as sign. + * Thus 0x1234560000 is compact (0x05123456) + * and 0xc0de000000 is compact (0x0600c0de) + * + * Bitcoin only uses this "compact" format for encoding difficulty + * targets, which are unsigned 256bit quantities. Thus, all the + * complexities of the sign bit and using base 256 are probably an + * implementation accident. + */ uint256& SetCompact(uint32_t nCompact, bool *pfNegative = NULL, bool *pfOverflow = NULL); uint32_t GetCompact(bool fNegative = false) const; |