Documentation ¶
Overview ¶
Package binary implements translation between numbers and byte sequences and encoding and decoding of varints.
Numbers are translated by reading and writing fixed-size values. A fixed-size value is either a fixed-size arithmetic type (int8, uint8, int16, float32, complex64, ...) or an array or struct containing only fixed-size values.
Varints are a method of encoding integers using one or more bytes; numbers with smaller absolute value take a smaller number of bytes. For a specification, see http://code.google.com/apis/protocolbuffers/docs/encoding.html.
Index ¶
- Constants
- Variables
- func PutUvarint(buf []byte, x uint64) int
- func PutVarint(buf []byte, x int64) int
- func Read(r io.Reader, order ByteOrder, data interface{}) error
- func ReadUvarint(r io.ByteReader) (uint64, error)
- func ReadVarint(r io.ByteReader) (int64, error)
- func Size(v interface{}) int
- func Uvarint(buf []byte) (uint64, int)
- func Varint(buf []byte) (int64, int)
- func Write(w io.Writer, order ByteOrder, data interface{}) error
- type ByteOrder
Examples ¶
Constants ¶
const ( MaxVarintLen16 = 3 MaxVarintLen32 = 5 MaxVarintLen64 = 10 )
MaxVarintLenN is the maximum length of a varint-encoded N-bit integer.
Variables ¶
var BigEndian bigEndian
BigEndian is the big-endian implementation of ByteOrder.
var LittleEndian littleEndian
LittleEndian is the little-endian implementation of ByteOrder.
Functions ¶
func PutUvarint ¶
PutUvarint encodes a uint64 into buf and returns the number of bytes written. If the buffer is too small, PutUvarint will panic.
func PutVarint ¶
PutVarint encodes an int64 into buf and returns the number of bytes written. If the buffer is too small, PutVarint will panic.
func Read ¶
Read reads structured binary data from r into data. Data must be a pointer to a fixed-size value or a slice of fixed-size values. Bytes read from r are decoded using the specified byte order and written to successive fields of the data. When reading into structs, the field data for fields with blank (_) field names is skipped; i.e., blank field names may be used for padding.
Example ¶
package main import ( "bytes" "encoding/binary" "fmt" ) func main() { var pi float64 b := []byte{0x18, 0x2d, 0x44, 0x54, 0xfb, 0x21, 0x09, 0x40} buf := bytes.NewBuffer(b) err := binary.Read(buf, binary.LittleEndian, &pi) if err != nil { fmt.Println("binary.Read failed:", err) } fmt.Print(pi) }
Output: 3.141592653589793
func ReadUvarint ¶
func ReadUvarint(r io.ByteReader) (uint64, error)
ReadUvarint reads an encoded unsigned integer from r and returns it as a uint64.
func ReadVarint ¶
func ReadVarint(r io.ByteReader) (int64, error)
ReadVarint reads an encoded signed integer from r and returns it as an int64.
func Size ¶
func Size(v interface{}) int
Size returns how many bytes Write would generate to encode the value v, which must be a fixed-size value or a slice of fixed-size values, or a pointer to such data.
func Uvarint ¶
Uvarint 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 Varint ¶
Varint 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 Write ¶
Write writes the binary representation of data into w. Data must be a fixed-size value or a slice of fixed-size values, or a pointer to such data. Bytes written to w are encoded using the specified byte order and read from successive fields of the data. When writing structs, zero values are written for fields with blank (_) field names.
Example ¶
package main import ( "bytes" "encoding/binary" "fmt" "math" ) func main() { buf := new(bytes.Buffer) var pi float64 = math.Pi err := binary.Write(buf, binary.LittleEndian, pi) if err != nil { fmt.Println("binary.Write failed:", err) } fmt.Printf("% x", buf.Bytes()) }
Output: 18 2d 44 54 fb 21 09 40
Example (Multi) ¶
package main import ( "bytes" "encoding/binary" "fmt" ) func main() { buf := new(bytes.Buffer) var data = []interface{}{ uint16(61374), int8(-54), uint8(254), } for _, v := range data { err := binary.Write(buf, binary.LittleEndian, v) if err != nil { fmt.Println("binary.Write failed:", err) } } fmt.Printf("%x", buf.Bytes()) }
Output: beefcafe
Types ¶
type ByteOrder ¶
type ByteOrder interface { Uint16([]byte) uint16 Uint32([]byte) uint32 Uint64([]byte) uint64 PutUint16([]byte, uint16) PutUint32([]byte, uint32) PutUint64([]byte, uint64) String() string }
A ByteOrder specifies how to convert byte sequences into 16-, 32-, or 64-bit unsigned integers.