github.com/cockroachdb/apd/v3@v3.2.0/bigint_go1.15_test.go (about)

     1  // Copyright 2022 The Cockroach Authors.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
    12  // implied. See the License for the specific language governing
    13  // permissions and limitations under the License.
    14  
    15  //go:build go1.15
    16  // +build go1.15
    17  
    18  package apd
    19  
    20  import (
    21  	"testing"
    22  	"testing/quick"
    23  )
    24  
    25  // TestBigIntMatchesMathBigInt15 is like TestBigIntMatchesMathBigInt, but for
    26  // parts of the shared BigInt/big.Int API that were introduced in go1.15.
    27  func TestBigIntMatchesMathBigInt15(t *testing.T) {
    28  	t.Run("FillBytes", func(t *testing.T) {
    29  		apd := func(z number) []byte {
    30  			return z.toApd(t).FillBytes(make([]byte, len(z)))
    31  		}
    32  		math := func(z number) []byte {
    33  			return z.toMath(t).FillBytes(make([]byte, len(z)))
    34  		}
    35  		require(t, quick.CheckEqual(apd, math, nil))
    36  	})
    37  }
    38  
    39  //////////////////////////////////////////////////////////////////////////////////
    40  // The following tests were copied from the standard library's math/big package //
    41  //////////////////////////////////////////////////////////////////////////////////
    42  
    43  func TestBigIntFillBytes(t *testing.T) {
    44  	checkResult := func(t *testing.T, buf []byte, want *BigInt) {
    45  		t.Helper()
    46  		got := new(BigInt).SetBytes(buf)
    47  		if got.CmpAbs(want) != 0 {
    48  			t.Errorf("got 0x%x, want 0x%x: %x", got, want, buf)
    49  		}
    50  	}
    51  	panics := func(f func()) (panic bool) {
    52  		defer func() { panic = recover() != nil }()
    53  		f()
    54  		return
    55  	}
    56  
    57  	for _, n := range []string{
    58  		"0",
    59  		"1000",
    60  		"0xffffffff",
    61  		"-0xffffffff",
    62  		"0xffffffffffffffff",
    63  		"0x10000000000000000",
    64  		"0xabababababababababababababababababababababababababa",
    65  		"0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff",
    66  	} {
    67  		t.Run(n, func(t *testing.T) {
    68  			t.Logf(n)
    69  			x, ok := new(BigInt).SetString(n, 0)
    70  			if !ok {
    71  				panic("invalid test entry")
    72  			}
    73  
    74  			// Perfectly sized buffer.
    75  			byteLen := (x.BitLen() + 7) / 8
    76  			buf := make([]byte, byteLen)
    77  			checkResult(t, x.FillBytes(buf), x)
    78  
    79  			// Way larger, checking all bytes get zeroed.
    80  			buf = make([]byte, 100)
    81  			for i := range buf {
    82  				buf[i] = 0xff
    83  			}
    84  			checkResult(t, x.FillBytes(buf), x)
    85  
    86  			// Too small.
    87  			if byteLen > 0 {
    88  				buf = make([]byte, byteLen-1)
    89  				if !panics(func() { x.FillBytes(buf) }) {
    90  					t.Errorf("expected panic for small buffer and value %x", x)
    91  				}
    92  			}
    93  		})
    94  	}
    95  }