// SetBytes interprets b as the bytes of a big-endian integer
// and sets z to that value.
func (z *Int) SetBytes(b []byte) *Int {
z.doinit()
if len(b) == 0 {
z.SetInt64(0)
} else {
C.mpz_import(&z.i[0], C.size_t(len(b)), 1, 1, 1, 0, unsafe.Pointer(&b[0]))
}
return z
}
// SetUint64 sets z to x and returns z.
func (z *Int) SetUint64(x uint64) *Int {
z.doinit()
// Test for truncation
y := C.ulong(x)
if uint64(y) == x {
C.mpz_set_ui(&z.i[0], y)
} else {
C.mpz_import(&z.i[0], 1, 0, 8, 0, 0, unsafe.Pointer(&x))
}
return z
}
// SetInt64 sets z to x and returns z.
func (z *Int) SetInt64(x int64) *Int {
z.doinit()
// Test for truncation
y := C.long(x)
if int64(y) == x {
C.mpz_set_si(&z.i[0], y)
} else {
negative := false
if x < 0 {
x = -x
negative = true
}
C.mpz_import(&z.i[0], 1, 0, 8, 0, 0, unsafe.Pointer(&x))
if negative {
C.mpz_neg(&z.i[0], &z.i[0])
}
}
return z
}
// Rand sets z to a pseudo-random number in [0, n) and returns z.
func (z *Int) Rand(rnd *rand.Rand, n *Int) *Int {
z.doinit()
// Get rid of n <= 0 case
if n.Sign() <= 0 {
z.SetInt64(0)
return z
}
// Make a copy of n if aliased
t := n
aliased := false
if n == z {
aliased = true
t = new(Int).Set(n)
}
// Work out bit sizes and masks
bits := n.BitLen() // >= 1
nwords := (bits + 31) / 32 // >= 1
bitLengthOfMSW := uint(bits % 32)
if bitLengthOfMSW == 0 {
bitLengthOfMSW = 32
}
mask := uint32((1 << bitLengthOfMSW) - 1)
words := make([]uint32, nwords)
for {
// Make a most significant first array of random bytes
for i := 0; i < nwords; i++ {
words[i] = rnd.Uint32()
}
// Mask out the top bits so this is only just bigger than n
words[0] &= mask
C.mpz_import(&z.i[0], C.size_t(len(words)), 1, 4, 0, 0, unsafe.Pointer(&words[0]))
// Exit if z < n - should take ~1.5 iterations of loop on average
if z.Cmp(t) < 0 {
break
}
}
if aliased {
t.Clear()
}
return z
}