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secp256k1: Tighten max magnitudes in comments. #3442

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Sep 9, 2024
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secp256k1: Tighten max magnitudes in comments. #3442

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23 changes: 12 additions & 11 deletions dcrec/secp256k1/field.go
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Original file line number Diff line number Diff line change
Expand Up @@ -139,7 +139,7 @@ const (
// and the caller MUST normalize the field value if a given operation would
// cause the magnitude of the result to exceed the max allowed value.
//
// IMPORTANT: The max allowed magnitude of a field value is 64.
// IMPORTANT: The max allowed magnitude of a field value is 32.
type FieldVal struct {
// Each 256-bit value is represented as 10 32-bit integers in base 2^26.
// This provides 6 bits of overflow in each word (10 bits in the most
Expand Down Expand Up @@ -628,14 +628,14 @@ func (f *FieldVal) Equals(val *FieldVal) bool {
}

// NegateVal negates the passed value and stores the result in f in constant
// time. The caller must provide the magnitude of the passed value for a
// correct result.
// time. The caller must provide the maximum magnitude of the passed value for
// a correct result.
//
// The field value is returned to support chaining. This enables syntax like:
// f.NegateVal(f2).AddInt(1) so that f = -f2 + 1.
//
// Preconditions:
// - The max magnitude MUST be 63
// - The max magnitude MUST be 31
// Output Normalized: No
// Output Max Magnitude: Input magnitude + 1
func (f *FieldVal) NegateVal(val *FieldVal, magnitude uint32) *FieldVal {
Expand Down Expand Up @@ -672,14 +672,14 @@ func (f *FieldVal) NegateVal(val *FieldVal, magnitude uint32) *FieldVal {
}

// Negate negates the field value in constant time. The existing field value is
// modified. The caller must provide the magnitude of the field value for a
// correct result.
// modified. The caller must provide the maximum magnitude of the field value
// for a correct result.
//
// The field value is returned to support chaining. This enables syntax like:
// f.Negate().AddInt(1) so that f = -f + 1.
//
// Preconditions:
// - The max magnitude MUST be 63
// - The max magnitude MUST be 31
// Output Normalized: No
// Output Max Magnitude: Input magnitude + 1
func (f *FieldVal) Negate(magnitude uint32) *FieldVal {
Expand All @@ -694,7 +694,8 @@ func (f *FieldVal) Negate(magnitude uint32) *FieldVal {
// f.AddInt(1).Add(f2) so that f = f + 1 + f2.
//
// Preconditions:
// - The field value MUST have a max magnitude of 63
// - The field value MUST have a max magnitude of 31
// - The integer MUST be a max of 32767
// Output Normalized: No
// Output Max Magnitude: Existing field magnitude + 1
func (f *FieldVal) AddInt(ui uint16) *FieldVal {
Expand All @@ -713,7 +714,7 @@ func (f *FieldVal) AddInt(ui uint16) *FieldVal {
// f.Add(f2).AddInt(1) so that f = f + f2 + 1.
//
// Preconditions:
// - The sum of the magnitudes of the two field values MUST be a max of 64
// - The sum of the magnitudes of the two field values MUST be a max of 32
// Output Normalized: No
// Output Max Magnitude: Sum of the magnitude of the two individual field values
func (f *FieldVal) Add(val *FieldVal) *FieldVal {
Expand Down Expand Up @@ -742,7 +743,7 @@ func (f *FieldVal) Add(val *FieldVal) *FieldVal {
// f3.Add2(f, f2).AddInt(1) so that f3 = f + f2 + 1.
//
// Preconditions:
// - The sum of the magnitudes of the two field values MUST be a max of 64
// - The sum of the magnitudes of the two field values MUST be a max of 32
// Output Normalized: No
// Output Max Magnitude: Sum of the magnitude of the two field values
func (f *FieldVal) Add2(val *FieldVal, val2 *FieldVal) *FieldVal {
Expand Down Expand Up @@ -774,7 +775,7 @@ func (f *FieldVal) Add2(val *FieldVal, val2 *FieldVal) *FieldVal {
// f.MulInt(2).Add(f2) so that f = 2 * f + f2.
//
// Preconditions:
// - The field value magnitude multiplied by given val MUST be a max of 64
// - The field value magnitude multiplied by given val MUST be a max of 32
// Output Normalized: No
// Output Max Magnitude: Existing field magnitude times the provided integer val
func (f *FieldVal) MulInt(val uint8) *FieldVal {
Expand Down