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laanwj/bignum_setcompact.cpp

Created September 21, 2012 15:33
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Checks for all 32 bit integers whether SetCompactNew(x) == SetCompactOld(x)
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bignum_setcompact.cpp
// g++ bignum_setcompact.cpp -o ./bignum_setcompact -lcrypto -O3
// Checks for all 32 bit integers whether SetCompactNew(x) == SetCompactOld(x)
#include <limits>
#include <stdexcept>
#include <vector>
#include <openssl/bn.h>
#include <algorithm>
#include <assert.h>
#include <sys/types.h>
#include <sys/wait.h>
// Number of threads to use
static const int NUM_CPUS = 6;
////////////////////// Bignum implementation to test ///////////////////
typedef unsigned long long uint64;
typedef long long int64;
/** Errors thrown by the bignum class */
class bignum_error : public std::runtime_error
{
public:
explicit bignum_error(const std::string& str) : std::runtime_error(str) {}
};
/** RAII encapsulated BN_CTX (OpenSSL bignum context) */
class CAutoBN_CTX
{
protected:
BN_CTX* pctx;
BN_CTX* operator=(BN_CTX* pnew) { return pctx = pnew; }
public:
CAutoBN_CTX()
{
pctx = BN_CTX_new();
if (pctx == NULL)
throw bignum_error("CAutoBN_CTX : BN_CTX_new() returned NULL");
}
~CAutoBN_CTX()
{
if (pctx != NULL)
BN_CTX_free(pctx);
}
operator BN_CTX*() { return pctx; }
BN_CTX& operator*() { return *pctx; }
BN_CTX** operator&() { return &pctx; }
bool operator!() { return (pctx == NULL); }
};
/** C++ wrapper for BIGNUM (OpenSSL bignum) */
class CBigNum : public BIGNUM
{
public:
CBigNum()
{
BN_init(this);
}
CBigNum(const CBigNum& b)
{
BN_init(this);
if (!BN_copy(this, &b))
{
BN_clear_free(this);
throw bignum_error("CBigNum::CBigNum(const CBigNum&) : BN_copy failed");
}
}
CBigNum& operator=(const CBigNum& b)
{
if (!BN_copy(this, &b))
throw bignum_error("CBigNum::operator= : BN_copy failed");
return (*this);
}
~CBigNum()
{
BN_clear_free(this);
}
//CBigNum(char n) is not portable. Use 'signed char' or 'unsigned char'.
CBigNum(signed char n) { BN_init(this); if (n >= 0) setulong(n); else setint64(n); }
CBigNum(short n) { BN_init(this); if (n >= 0) setulong(n); else setint64(n); }
CBigNum(int n) { BN_init(this); if (n >= 0) setulong(n); else setint64(n); }
CBigNum(long n) { BN_init(this); if (n >= 0) setulong(n); else setint64(n); }
CBigNum(int64 n) { BN_init(this); setint64(n); }
CBigNum(unsigned char n) { BN_init(this); setulong(n); }
CBigNum(unsigned short n) { BN_init(this); setulong(n); }
CBigNum(unsigned int n) { BN_init(this); setulong(n); }
CBigNum(unsigned long n) { BN_init(this); setulong(n); }
CBigNum(uint64 n) { BN_init(this); setuint64(n); }
explicit CBigNum(const std::vector<unsigned char>& vch)
{
BN_init(this);
setvch(vch);
}
void setulong(unsigned long n)
{
if (!BN_set_word(this, n))
throw bignum_error("CBigNum conversion from unsigned long : BN_set_word failed");
}
unsigned long getulong() const
{
return BN_get_word(this);
}
unsigned int getuint() const
{
return BN_get_word(this);
}
int getint() const
{
unsigned long n = BN_get_word(this);
if (!BN_is_negative(this))
return (n > (unsigned long)std::numeric_limits<int>::max() ? std::numeric_limits<int>::max() : n);
else
return (n > (unsigned long)std::numeric_limits<int>::max() ? std::numeric_limits<int>::min() : -(int)n);
}
void setint64(int64 sn)
{
unsigned char pch[sizeof(sn) + 6];
unsigned char* p = pch + 4;
bool fNegative;
uint64 n;
if (sn < (int64)0)
{
// Since the minimum signed integer cannot be represented as positive so long as its type is signed, and it's not well-defined what happens if you make it unsigned before negating it, we instead increment the negative integer by 1, convert it, then increment the (now positive) unsigned integer by 1 to compensate
n = -(sn + 1);
++n;
fNegative = true;
} else {
n = sn;
fNegative = false;
}
bool fLeadingZeroes = true;
for (int i = 0; i < 8; i++)
{
unsigned char c = (n >> 56) & 0xff;
n <<= 8;
if (fLeadingZeroes)
{
if (c == 0)
continue;
if (c & 0x80)
*p++ = (fNegative ? 0x80 : 0);
else if (fNegative)
c |= 0x80;
fLeadingZeroes = false;
}
*p++ = c;
}
unsigned int nSize = p - (pch + 4);
pch[0] = (nSize >> 24) & 0xff;
pch[1] = (nSize >> 16) & 0xff;
pch[2] = (nSize >> 8) & 0xff;
pch[3] = (nSize) & 0xff;
BN_mpi2bn(pch, p - pch, this);
}
void setuint64(uint64 n)
{
unsigned char pch[sizeof(n) + 6];
unsigned char* p = pch + 4;
bool fLeadingZeroes = true;
for (int i = 0; i < 8; i++)
{
unsigned char c = (n >> 56) & 0xff;
n <<= 8;
if (fLeadingZeroes)
{
if (c == 0)
continue;
if (c & 0x80)
*p++ = 0;
fLeadingZeroes = false;
}
*p++ = c;
}
unsigned int nSize = p - (pch + 4);
pch[0] = (nSize >> 24) & 0xff;
pch[1] = (nSize >> 16) & 0xff;
pch[2] = (nSize >> 8) & 0xff;
pch[3] = (nSize) & 0xff;
BN_mpi2bn(pch, p - pch, this);
}
void setvch(const std::vector<unsigned char>& vch)
{
std::vector<unsigned char> vch2(vch.size() + 4);
unsigned int nSize = vch.size();
// BIGNUM's byte stream format expects 4 bytes of
// big endian size data info at the front
vch2[0] = (nSize >> 24) & 0xff;
vch2[1] = (nSize >> 16) & 0xff;
vch2[2] = (nSize >> 8) & 0xff;
vch2[3] = (nSize >> 0) & 0xff;
// swap data to big endian
reverse_copy(vch.begin(), vch.end(), vch2.begin() + 4);
BN_mpi2bn(&vch2[0], vch2.size(), this);
}
std::vector<unsigned char> getvch() const
{
unsigned int nSize = BN_bn2mpi(this, NULL);
if (nSize <= 4)
return std::vector<unsigned char>();
std::vector<unsigned char> vch(nSize);
BN_bn2mpi(this, &vch[0]);
vch.erase(vch.begin(), vch.begin() + 4);
reverse(vch.begin(), vch.end());
return 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.
//
// This implementation directly uses shifts instead of going
// through an intermediate MPI representation.
CBigNum& SetCompactNew(unsigned int nCompact)
{
unsigned int nSize = nCompact >> 24;
bool fNegative =(nCompact & 0x00800000) != 0;
unsigned int nWord = nCompact & 0x007fffff;
if (nSize <= 3)
{
nWord >>= 8*(3-nSize);
BN_set_word(this, nWord);
}
else
{
BN_set_word(this, nWord);
BN_lshift(this, this, 8*(nSize-3));
}
BN_set_negative(this, fNegative);
return *this;
}
unsigned int GetCompactNew() const
{
unsigned int nSize = BN_num_bytes(this);
unsigned int nCompact = 0;
if (nSize <= 3)
nCompact = BN_get_word(this) << 8*(3-nSize);
else
{
CBigNum bn;
BN_rshift(&bn, this, 8*(nSize-3));
nCompact = BN_get_word(&bn);
}
// The 0x00800000 bit denotes the sign.
// Thus, if it is already set, divide the mantissa by 256 and increase the exponent.
if (nCompact & 0x00800000)
{
nCompact >>= 8;
nSize++;
}
nCompact |= nSize << 24;
nCompact |= (BN_is_negative(this) ? 0x00800000 : 0);
return nCompact;
}
CBigNum& SetCompactOld(unsigned int nCompact)
{
unsigned int nSize = nCompact >> 24;
std::vector<unsigned char> vch(4 + nSize);
vch[3] = nSize;
if (nSize >= 1) vch[4] = (nCompact >> 16) & 0xff;
if (nSize >= 2) vch[5] = (nCompact >> 8) & 0xff;
if (nSize >= 3) vch[6] = (nCompact >> 0) & 0xff;
BN_mpi2bn(&vch[0], vch.size(), this);
return *this;
}
unsigned int GetCompactOld() const
{
unsigned int nSize = BN_bn2mpi(this, NULL);
std::vector<unsigned char> vch(nSize);
nSize -= 4;
BN_bn2mpi(this, &vch[0]);
unsigned int nCompact = nSize << 24;
if (nSize >= 1) nCompact |= (vch[4] << 16);
if (nSize >= 2) nCompact |= (vch[5] << 8);
if (nSize >= 3) nCompact |= (vch[6] << 0);
return nCompact;
}
void SetHex(const std::string& str)
{
// skip 0x
const char* psz = str.c_str();
while (isspace(*psz))
psz++;
bool fNegative = false;
if (*psz == '-')
{
fNegative = true;
psz++;
}
if (psz[0] == '0' && tolower(psz[1]) == 'x')
psz += 2;
while (isspace(*psz))
psz++;
// hex string to bignum
static signed char phexdigit[256] = { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,1,2,3,4,5,6,7,8,9,0,0,0,0,0,0, 0,0xa,0xb,0xc,0xd,0xe,0xf,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0xa,0xb,0xc,0xd,0xe,0xf,0,0,0,0,0,0,0,0,0 };
*this = 0;
while (isxdigit(*psz))
{
*this <<= 4;
int n = phexdigit[(unsigned char)*psz++];
*this += n;
}
if (fNegative)
*this = 0 - *this;
}
std::string ToString(int nBase=10) const
{
CAutoBN_CTX pctx;
CBigNum bnBase = nBase;
CBigNum bn0 = 0;
std::string str;
CBigNum bn = *this;
BN_set_negative(&bn, false);
CBigNum dv;
CBigNum rem;
if (BN_cmp(&bn, &bn0) == 0)
return "0";
while (BN_cmp(&bn, &bn0) > 0)
{
if (!BN_div(&dv, &rem, &bn, &bnBase, pctx))
throw bignum_error("CBigNum::ToString() : BN_div failed");
bn = dv;
unsigned int c = rem.getulong();
str += "0123456789abcdef"[c];
}
if (BN_is_negative(this))
str += "-";
reverse(str.begin(), str.end());
return str;
}
std::string GetHex() const
{
return ToString(16);
}
bool operator!() const
{
return BN_is_zero(this);
}
CBigNum& operator+=(const CBigNum& b)
{
if (!BN_add(this, this, &b))
throw bignum_error("CBigNum::operator+= : BN_add failed");
return *this;
}
CBigNum& operator-=(const CBigNum& b)
{
*this = *this - b;
return *this;
}
CBigNum& operator*=(const CBigNum& b)
{
CAutoBN_CTX pctx;
if (!BN_mul(this, this, &b, pctx))
throw bignum_error("CBigNum::operator*= : BN_mul failed");
return *this;
}
CBigNum& operator/=(const CBigNum& b)
{
*this = *this / b;
return *this;
}
CBigNum& operator%=(const CBigNum& b)
{
*this = *this % b;
return *this;
}
CBigNum& operator<<=(unsigned int shift)
{
if (!BN_lshift(this, this, shift))
throw bignum_error("CBigNum:operator<<= : BN_lshift failed");
return *this;
}
CBigNum& operator>>=(unsigned int shift)
{
// Note: BN_rshift segfaults on 64-bit if 2^shift is greater than the number
// if built on ubuntu 9.04 or 9.10, probably depends on version of OpenSSL
CBigNum a = 1;
a <<= shift;
if (BN_cmp(&a, this) > 0)
{
*this = 0;
return *this;
}
if (!BN_rshift(this, this, shift))
throw bignum_error("CBigNum:operator>>= : BN_rshift failed");
return *this;
}
CBigNum& operator++()
{
// prefix operator
if (!BN_add(this, this, BN_value_one()))
throw bignum_error("CBigNum::operator++ : BN_add failed");
return *this;
}
const CBigNum operator++(int)
{
// postfix operator
const CBigNum ret = *this;
++(*this);
return ret;
}
CBigNum& operator--()
{
// prefix operator
CBigNum r;
if (!BN_sub(&r, this, BN_value_one()))
throw bignum_error("CBigNum::operator-- : BN_sub failed");
*this = r;
return *this;
}
const CBigNum operator--(int)
{
// postfix operator
const CBigNum ret = *this;
--(*this);
return ret;
}
friend inline const CBigNum operator-(const CBigNum& a, const CBigNum& b);
friend inline const CBigNum operator/(const CBigNum& a, const CBigNum& b);
friend inline const CBigNum operator%(const CBigNum& a, const CBigNum& b);
};
inline const CBigNum operator+(const CBigNum& a, const CBigNum& b)
{
CBigNum r;
if (!BN_add(&r, &a, &b))
throw bignum_error("CBigNum::operator+ : BN_add failed");
return r;
}
inline const CBigNum operator-(const CBigNum& a, const CBigNum& b)
{
CBigNum r;
if (!BN_sub(&r, &a, &b))
throw bignum_error("CBigNum::operator- : BN_sub failed");
return r;
}
inline const CBigNum operator-(const CBigNum& a)
{
CBigNum r(a);
BN_set_negative(&r, !BN_is_negative(&r));
return r;
}
inline const CBigNum operator*(const CBigNum& a, const CBigNum& b)
{
CAutoBN_CTX pctx;
CBigNum r;
if (!BN_mul(&r, &a, &b, pctx))
throw bignum_error("CBigNum::operator* : BN_mul failed");
return r;
}
inline const CBigNum operator/(const CBigNum& a, const CBigNum& b)
{
CAutoBN_CTX pctx;
CBigNum r;
if (!BN_div(&r, NULL, &a, &b, pctx))
throw bignum_error("CBigNum::operator/ : BN_div failed");
return r;
}
inline const CBigNum operator%(const CBigNum& a, const CBigNum& b)
{
CAutoBN_CTX pctx;
CBigNum r;
if (!BN_mod(&r, &a, &b, pctx))
throw bignum_error("CBigNum::operator% : BN_div failed");
return r;
}
inline const CBigNum operator<<(const CBigNum& a, unsigned int shift)
{
CBigNum r;
if (!BN_lshift(&r, &a, shift))
throw bignum_error("CBigNum:operator<< : BN_lshift failed");
return r;
}
inline const CBigNum operator>>(const CBigNum& a, unsigned int shift)
{
CBigNum r = a;
r >>= shift;
return r;
}
inline bool operator==(const CBigNum& a, const CBigNum& b) { return (BN_cmp(&a, &b) == 0); }
inline bool operator!=(const CBigNum& a, const CBigNum& b) { return (BN_cmp(&a, &b) != 0); }
inline bool operator<=(const CBigNum& a, const CBigNum& b) { return (BN_cmp(&a, &b) <= 0); }
inline bool operator>=(const CBigNum& a, const CBigNum& b) { return (BN_cmp(&a, &b) >= 0); }
inline bool operator<(const CBigNum& a, const CBigNum& b) { return (BN_cmp(&a, &b) < 0); }
inline bool operator>(const CBigNum& a, const CBigNum& b) { return (BN_cmp(&a, &b) > 0); }
///////////////////////// Beginning of test code ///////////////////////
int run_numbers(int proc, uint64 start, uint64 end)
{
CBigNum num_old;
CBigNum num_new;
int errors = 0;
printf("%i: range %08llx - %08llx\n", proc, start, end);
for(uint64 c = start; c < end; ++c)
{
unsigned int x = (unsigned int)c;
num_old.SetCompactOld(x);
num_new.SetCompactNew(x);
if(num_old != num_new)
{
printf("Mismatch: %08x is %c%s (old) versus %c%s (new)\n", x,
BN_is_negative(&num_old)?'-':' ', num_old.GetHex().c_str(),
BN_is_negative(&num_new)?'-':' ', num_new.GetHex().c_str());
errors += 1;
}
if((x&0xFFFFF)==0)
{
printf("%08x\n", x);
fflush(stdout);
}
++x;
}
return errors != 0;
}
int main()
{
pid_t pids[NUM_CPUS];
// fork
for(int i=0; i<NUM_CPUS; ++i)
{
pid_t pid = fork();
assert(pid >= 0);
if(pid == 0)
{
exit(run_numbers(pid, (0x100000000ULL * i)/(NUM_CPUS), (0x100000000ULL * (i+1))/(NUM_CPUS)));
}
pids[i] = pid;
}
// join
int errors = 0;
for(int i=0; i<NUM_CPUS; ++i)
{
int status = -1;
assert(waitpid(pids[i], &status, 0) == pids[i]);
errors += WEXITSTATUS(status);
}
if(errors != 0)
{
printf("\033[31mThere were errors!\033[0m\n");
}
return 0;
}
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