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move bignumber random and umod to util package big.go
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Original file line number | Diff line number | Diff line change |
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package util | ||
|
||
import ( | ||
"crypto/rand" | ||
"math/big" | ||
) | ||
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// Umod returns the unsigned modulus of x and y. | ||
// It ensures the result is always non-negative. | ||
func Umod(x *big.Int, y *big.Int) *big.Int { | ||
// Ensure divisor y is not zero | ||
if y.Sign() == 0 { | ||
panic("division by zero") | ||
} | ||
|
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// If the dividend x is zero, the modulus is zero | ||
if x.Sign() == 0 { | ||
return big.NewInt(0) | ||
} | ||
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mod := new(big.Int) | ||
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// Handle cases where x is negative and y is positive | ||
if x.Sign() < 0 && y.Sign() > 0 { | ||
mod.Neg(x) | ||
mod.Mod(mod, y) | ||
mod.Neg(mod) | ||
if mod.Sign() < 0 { | ||
mod.Add(mod, y) | ||
} | ||
} else if x.Sign() > 0 && y.Sign() < 0 { | ||
// Handle cases where x is positive and y is negative | ||
mod.Mod(x, new(big.Int).Neg(y)) | ||
} else if x.Sign() < 0 && y.Sign() < 0 { | ||
// Handle cases where both x and y are negative | ||
mod.Neg(x) | ||
mod.Mod(mod, new(big.Int).Neg(y)) | ||
mod.Neg(mod) | ||
if mod.Sign() < 0 { | ||
mod.Sub(mod, y) | ||
} | ||
} else { | ||
// Both numbers are positive | ||
mod.Mod(x, y) | ||
} | ||
|
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// Ensure the result is non-negative | ||
if mod.Sign() < 0 { | ||
mod.Add(mod, new(big.Int).Abs(y)) | ||
} | ||
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return mod | ||
} | ||
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func NewRandomBigInt(byteLen int) *big.Int { | ||
b := make([]byte, byteLen) | ||
_, err := rand.Read(b) | ||
if err != nil { | ||
panic(err) | ||
} | ||
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return new(big.Int).SetBytes(b) | ||
} |