diff options
| -rw-r--r-- | common/math/big.go | 22 | ||||
| -rw-r--r-- | common/math/big_test.go | 11 | ||||
| -rw-r--r-- | core/vm/instructions.go | 4 |
3 files changed, 19 insertions, 18 deletions
diff --git a/common/math/big.go b/common/math/big.go index 48ad90216..c49d751fa 100644 --- a/common/math/big.go +++ b/common/math/big.go @@ -130,10 +130,10 @@ func PaddedBigBytes(bigint *big.Int, n int) []byte { return ret } -// LittleEndianByteAt returns the byte at position n, -// if bigint is considered little-endian. -// So n==0 gives the least significant byte -func LittleEndianByteAt(bigint *big.Int, n int) byte { +// bigEndianByteAt returns the byte at position n, +// if bigint is considered big-endian. +// So n==0 returns the least significant byte +func bigEndianByteAt(bigint *big.Int, n int) byte { words := bigint.Bits() // Check word-bucket the byte will reside in i := n / wordBytes @@ -147,15 +147,15 @@ func LittleEndianByteAt(bigint *big.Int, n int) byte { return byte(word >> shift) } -// BigEndian32ByteAt returns the byte at position n, -// if bigint is considered big-endian. -// So n==0 gives the most significant byte -// WARNING: Only works for bigints in 32-byte range -func BigEndian32ByteAt(bigint *big.Int, n int) byte { - if n > 31 { +// Byte returns the byte at position n, +// if bigint is considered little-endian with the supplied padlength. +// n==0 returns the most significant byte +// bigint '5', padlength 32, n=31 => 5 +func Byte(bigint *big.Int, padlength, n int) byte { + if n >= padlength { return byte(0) } - return LittleEndianByteAt(bigint, 31-n) + return bigEndianByteAt(bigint, padlength-1-n) } // ReadBits encodes the absolute value of bigint as big-endian bytes. Callers must ensure diff --git a/common/math/big_test.go b/common/math/big_test.go index d4de7b8c3..7cce7c212 100644 --- a/common/math/big_test.go +++ b/common/math/big_test.go @@ -157,13 +157,13 @@ func BenchmarkPaddedBigBytesSmallOnePadding(b *testing.B) { func BenchmarkByteAtBrandNew(b *testing.B) { bigint := MustParseBig256("0x18F8F8F1000111000110011100222004330052300000000000000000FEFCF3CC") for i := 0; i < b.N; i++ { - BigEndian32ByteAt(bigint, 15) + bigEndianByteAt(bigint, 15) } } func BenchmarkByteAt(b *testing.B) { bigint := MustParseBig256("0x18F8F8F1000111000110011100222004330052300000000000000000FEFCF3CC") for i := 0; i < b.N; i++ { - BigEndian32ByteAt(bigint, 15) + bigEndianByteAt(bigint, 15) } } func BenchmarkByteAtOld(b *testing.B) { @@ -225,7 +225,7 @@ func TestLittleEndianByteAt(t *testing.T) { } for _, test := range tests { v := new(big.Int).SetBytes(common.Hex2Bytes(test.x)) - actual := LittleEndianByteAt(v, test.y) + actual := bigEndianByteAt(v, test.y) if actual != test.exp { t.Fatalf("Expected [%v] %v:th byte to be %v, was %v.", test.x, test.y, test.exp, actual) } @@ -254,11 +254,12 @@ func TestBigEndianByteAt(t *testing.T) { {"0000000000000000000000000000000000000000000000000000000000102030", 31, 0x30}, {"0000000000000000000000000000000000000000000000000000000000102030", 30, 0x20}, {"ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff", 32, 0x0}, - {"ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff", 0xFFFFFFFF, 0x0}, + {"ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff", 31, 0xFF}, + {"ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff", 0xFFFF, 0x0}, } for _, test := range tests { v := new(big.Int).SetBytes(common.Hex2Bytes(test.x)) - actual := BigEndian32ByteAt(v, test.y) + actual := Byte(v, 32, test.y) if actual != test.exp { t.Fatalf("Expected [%v] %v:th byte to be %v, was %v.", test.x, test.y, test.exp, actual) } diff --git a/core/vm/instructions.go b/core/vm/instructions.go index bcaf18e8a..f5164fcdd 100644 --- a/core/vm/instructions.go +++ b/core/vm/instructions.go @@ -258,8 +258,8 @@ func opXor(pc *uint64, evm *EVM, contract *Contract, memory *Memory, stack *Stac func opByte(pc *uint64, evm *EVM, contract *Contract, memory *Memory, stack *Stack) ([]byte, error) { th, val := stack.pop(), stack.peek() if th.Cmp(common.Big32) < 0 { - b := math.BigEndian32ByteAt(val, int(th.Int64())) - val.SetInt64(int64(b)) + b := math.Byte(val, 32, int(th.Int64())) + val.SetUint64(uint64(b)) } else { val.SetUint64(0) } |