/
compactint.go
95 lines (86 loc) · 1.91 KB
/
compactint.go
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package util
import (
"encoding/binary"
"fmt"
"io"
"math"
)
var errVarIntDesc = "non-rule varint %x - discriminant %x must encode a value greater than %x "
func ReadVarInt(r io.Reader) (uint64, error) {
discriminant, err := BinarySerializer.Uint8(r)
if err != nil {
return 0, err
}
var result uint64
switch discriminant {
case 0xff:
sv, err := BinarySerializer.Uint64(r, binary.LittleEndian)
if err != nil {
return 0, err
}
result = sv
min := uint64(0x100000000)
if result < min {
return 0, fmt.Errorf(errVarIntDesc, result, discriminant, min)
}
case 0xfe:
sv, err := BinarySerializer.Uint32(r, binary.LittleEndian)
if err != nil {
return 0, err
}
result = uint64(sv)
min := uint64(0x10000)
if result < min {
return 0, fmt.Errorf(errVarIntDesc, result, discriminant, min)
}
case 0xfd:
sv, err := BinarySerializer.Uint16(r, binary.LittleEndian)
if err != nil {
return 0, err
}
result = uint64(sv)
min := uint64(0xfd)
if result < min {
return 0, fmt.Errorf(errVarIntDesc, result, discriminant, min)
}
default:
result = uint64(discriminant)
}
return result, nil
}
func WriteVarInt(w io.Writer, val uint64) error {
if val < 0xfd {
return BinarySerializer.PutUint8(w, uint8(val))
}
if val <= math.MaxUint16 {
err := BinarySerializer.PutUint8(w, 0xfd)
if err != nil {
return err
}
return BinarySerializer.PutUint16(w, binary.LittleEndian, uint16(val))
}
if val <= math.MaxUint32 {
err := BinarySerializer.PutUint8(w, 0xfe)
if err != nil {
return err
}
return BinarySerializer.PutUint32(w, binary.LittleEndian, uint32(val))
}
err := BinarySerializer.PutUint8(w, 0xff)
if err != nil {
return err
}
return BinarySerializer.PutUint64(w, binary.LittleEndian, val)
}
func VarIntSerializeSize(val uint64) uint32 {
if val < 0xfd {
return 1
}
if val <= math.MaxUint16 {
return 3
}
if val <= math.MaxUint32 {
return 5
}
return 9
}