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// Copyright 2025 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package ec_test
import (
"testing"
"github.com/google/go-cmp/cmp"
"github.com/tink-crypto/tink-go/v2/internal/ec"
)
func TestBigIntBytesToFixedSizeBuffer(t *testing.T) {
for _, tc := range []struct {
name string
input []byte
size int
want []byte
}{
{
name: "same size",
input: []byte{0x01, 0x02, 0x03, 0x04},
size: 4,
want: []byte{0x01, 0x02, 0x03, 0x04},
},
{
name: "input smaller than size",
input: []byte{0x01, 0x02, 0x03, 0x04},
size: 5,
want: []byte{0x00, 0x01, 0x02, 0x03, 0x04},
},
{
name: "input larger than size",
input: []byte{0x00, 0x00, 0x03, 0x04, 0x05, 0x06},
size: 4,
want: []byte{0x03, 0x04, 0x05, 0x06},
},
{
name: "input larger than size with leading zeros",
input: []byte{0x00, 0x00, 0x03, 0x04, 0x05, 0x06},
size: 5,
want: []byte{0x00, 0x03, 0x04, 0x05, 0x06},
},
} {
t.Run(tc.name, func(t *testing.T) {
got, err := ec.BigIntBytesToFixedSizeBuffer(tc.input, tc.size)
if err != nil {
t.Fatalf("ec.BigIntBytesToFixedSizeBuffer(%v, %v) err = %v, want nil", tc.input, tc.size, err)
}
if diff := cmp.Diff(tc.want, got); diff != "" {
t.Errorf("ec.BigIntBytesToFixedSizeBuffer(%v, %v) returned unexpected diff (-want +got):\n%s", tc.input, tc.size, diff)
}
})
}
}
func TestBigIntBytesToFixedSizeBuffer_FailsWhenInputTooLarge(t *testing.T) {
if _, err := ec.BigIntBytesToFixedSizeBuffer([]byte{0x01, 0x02}, 1); err == nil {
t.Errorf("ec.BigIntBytesToFixedSizeBuffer() err = nil, want error")
}
}
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