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encoding/hex: don't overallocate memory in DecodeString #67259

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encoding/hex: don't overallocate memory in DecodeString #67259

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a72fdb1
encoding/hex: don't over allocate memory in DecodeString
mateusz834 May 8, 2024
aeedf3f
simplify
mateusz834 May 8, 2024
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8 changes: 3 additions & 5 deletions src/encoding/hex/hex.go
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Original file line number Diff line number Diff line change
Expand Up @@ -136,11 +136,9 @@ func EncodeToString(src []byte) string {
// If the input is malformed, DecodeString returns
// the bytes decoded before the error.
func DecodeString(s string) ([]byte, error) {
src := []byte(s)
// We can use the source slice itself as the destination
// because the decode loop increments by one and then the 'seen' byte is not used anymore.
n, err := Decode(src, src)
return src[:n], err
dst := make([]byte, DecodedLen(len(s)))
n, err := Decode(dst, []byte(s))
return dst[:n], err
}

// Dump returns a string that contains a hex dump of the given data. The format
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12 changes: 12 additions & 0 deletions src/encoding/hex/hex_test.go
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Expand Up @@ -275,6 +275,18 @@ func BenchmarkDecode(b *testing.B) {
}
}

func BenchmarkDecodeString(b *testing.B) {
for _, size := range []int{256, 1024, 4096, 16384} {
src := strings.Repeat("2b744faa", size/8)
b.Run(fmt.Sprintf("%v", size), func(b *testing.B) {
b.SetBytes(int64(size))
for i := 0; i < b.N; i++ {
sink, _ = DecodeString(src)
}
})
}
}

func BenchmarkDump(b *testing.B) {
for _, size := range []int{256, 1024, 4096, 16384} {
src := bytes.Repeat([]byte{2, 3, 5, 7, 9, 11, 13, 17}, size/8)
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