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package vlq
import (
"errors"
"io"
)
const (
MaxLen16 = 3
MaxLen32 = 5
MaxLen64 = 10
)
var overflow = errors.New("vlq: number overflows a 64-bit integer")
// PutUint encodes a uint64 into buf and returns the number of bytes written.
// If the buffer is too small, PutUint will panic.
func PutUint(buf []byte, x uint64) int {
var n uint
for n = 9; n > 0; n-- {
if x >= 1<<(n*7) {
break
}
}
i := int(n) + 1
buf[n] = byte(x) & 0x7F
for n > 0 {
n--
x >>= 7
buf[n] = byte(x) | 0x80
}
return i
}
// Uint decodes a uint64 from buf and returns that value and the
// number of bytes read (> 0). If an error occurred, the value is 0
// and the number of bytes n is <= 0 meaning:
//
// n == 0: buf too small
// n < 0: value larger than 64 bits (overflow)
// and -n is the number of bytes read
//
func Uint(buf []byte) (uint64, int) {
var x uint64
for i, b := range buf {
x = (x << 7) | uint64(b&0x7f)
if b < 0x80 {
return x, i + 1
} else if i == 9 {
return 0, -i - 1 // overflow
}
}
return x, 0
}
// PutInt encodes an int64 into buf and returns the number of bytes written.
// If the buffer is too small, PutInt will panic.
func PutInt(buf []byte, x int64) int {
ux := uint64(x) << 1
if x < 0 {
ux = ^ux
}
return PutUint(buf, ux)
}
// Int decodes an int64 from buf and returns that value and the
// number of bytes read (> 0). If an error occurred, the value is 0
// and the number of bytes n is <= 0 with the following meaning:
//
// n == 0: buf too small
// n < 0: value larger than 64 bits (overflow)
// and -n is the number of bytes read
//
func Int(buf []byte) (int64, int) {
ux, n := Uint(buf) // ok to continue in presence of error
x := int64(ux >> 1)
if ux&1 != 0 {
x = ^x
}
return x, n
}
// ReadUint reads an encoded unsigned integer from r and returns it as a uint64.
func ReadUint(r io.ByteReader) (uint64, error) {
var x uint64
for i := 0; ; i++ {
b, err := r.ReadByte()
if err != nil {
return x, err
}
x = (x << 7) | uint64(b&0x7f)
if b < 0x80 {
return x, nil
} else if i == 9 {
return 0, overflow
}
}
}
// ReadInt reads an encoded signed integer from r and returns it as an int64.
func ReadInt(r io.ByteReader) (int64, error) {
ux, err := ReadUint(r) // ok to continue in presence of error
x := int64(ux >> 1)
if ux&1 != 0 {
x = ^x
}
return x, err
}
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