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feat: add sizevarint + sizeuvarint

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This commit is contained in:
Matthew Kim 2024-03-17 14:28:59 -04:00
parent 0a6f05e30f
commit 68a1f18b65
2 changed files with 27 additions and 0 deletions
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17
src/encoding/binary/varint.go
View File

@ -27,6 +27,7 @@ package binary
import (
"errors"
"io"
"math/bits"
)
// MaxVarintLenN is the maximum length of a varint-encoded N-bit integer.
@ -164,3 +165,19 @@ func ReadVarint(r io.ByteReader) (int64, error) {
}
return x, err
}
// SizeUvarint returns the encoded size of a unsigned varint.
// The size is guaranteed to be within 1 and 10, inclusive.
func SizeUvarint(x uint64) int {
return int(9*uint32(bits.Len64(x))+64) / 64
}
// SizeVarint returns the encoded size of a signed varint.
// The size is guaranteed to be within 1 and 10, inclusive.
func SizeVarint(x int64) int {
ux := uint64(x) << 1
if x < 0 {
ux = ^ux
}
return SizeUvarint(ux)
}

10
src/encoding/binary/varint_test.go
View File

@ -36,6 +36,11 @@ func testVarint(t *testing.T, x int64) {
t.Errorf("Varint(%d): got n = %d; want %d", x, m, n)
}
l := SizeVarint(x)
if n != l {
t.Errorf("SizeVarint(%d): got n = %d, want %d", x, m, l)
}
buf2 := []byte("prefix")
buf2 = AppendVarint(buf2, x)
if string(buf2) != "prefix"+string(buf[:n]) {
@ -62,6 +67,11 @@ func testUvarint(t *testing.T, x uint64) {
t.Errorf("Uvarint(%d): got n = %d; want %d", x, m, n)
}
l := SizeUvarint(x)
if n != l {
t.Errorf("SizeUvarint(%d): got n = %d, want %d", x, m, l)
}
buf2 := []byte("prefix")
buf2 = AppendUvarint(buf2, x)
if string(buf2) != "prefix"+string(buf[:n]) {