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-rw-r--r--common/math/big.go22
-rw-r--r--common/math/big_test.go11
2 files changed, 17 insertions, 16 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)
}