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readers.go
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readers.go
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package vm
import (
"encoding/binary"
"fmt"
"io"
"math"
)
type ByteReader interface {
ReadByte() (byte, error)
}
func readBool(r io.Reader) (bool, error) {
var b byte
var err error
if br, ok := r.(ByteReader); ok {
b, err = br.ReadByte()
} else {
bs := make([]byte, 1)
_, err = io.ReadFull(r, bs)
if err != nil {
return false, err
}
b = bs[0]
}
return b == 1, nil
}
func readBytes(r io.Reader) ([]byte, error) {
size, err := readLong(r)
if err != nil {
return nil, err
}
if size == 0 {
return []byte{}, nil
}
bb := make([]byte, size)
_, err = io.ReadFull(r, bb)
return bb, err
}
func readDouble(r io.Reader) (float64, error) {
buf := make([]byte, 8)
_, err := io.ReadFull(r, buf)
if err != nil {
return 0, err
}
bits := binary.LittleEndian.Uint64(buf)
val := math.Float64frombits(bits)
return val, nil
}
func readFloat(r io.Reader) (float32, error) {
buf := make([]byte, 4)
_, err := io.ReadFull(r, buf)
if err != nil {
return 0, err
}
bits := binary.LittleEndian.Uint32(buf)
val := math.Float32frombits(bits)
return val, nil
}
func readInt(r io.Reader) (int32, error) {
var v int
var b byte
var err error
if br, ok := r.(ByteReader); ok {
for shift := uint(0); ; shift += 7 {
if b, err = br.ReadByte(); err != nil {
return 0, err
}
v |= int(b&127) << shift
if b&128 == 0 {
break
}
}
} else {
buf := make([]byte, 1)
for shift := uint(0); ; shift += 7 {
if _, err := io.ReadFull(r, buf); err != nil {
return 0, err
}
b = buf[0]
v |= int(b&127) << shift
if b&128 == 0 {
break
}
}
}
datum := (int32(v>>1) ^ -int32(v&1))
return datum, nil
}
func readLong(r io.Reader) (int64, error) {
var v uint64
var b byte
var err error
if br, ok := r.(ByteReader); ok {
for shift := uint(0); ; shift += 7 {
if b, err = br.ReadByte(); err != nil {
return 0, err
}
v |= uint64(b&127) << shift
if b&128 == 0 {
break
}
}
} else {
buf := make([]byte, 1)
for shift := uint(0); ; shift += 7 {
if _, err = io.ReadFull(r, buf); err != nil {
return 0, err
}
b = buf[0]
v |= uint64(b&127) << shift
if b&128 == 0 {
break
}
}
}
datum := (int64(v>>1) ^ -int64(v&1))
return datum, nil
}
func readString(r io.Reader) (string, error) {
len, err := readLong(r)
if err != nil {
return "", err
}
// makeslice can fail depending on available memory.
// We arbitrarily limit string size to sane default (~2.2GB).
if len < 0 || len > math.MaxInt32 {
return "", fmt.Errorf("string length out of range: %d", len)
}
if len == 0 {
return "", nil
}
bb := make([]byte, len)
_, err = io.ReadFull(r, bb)
if err != nil {
return "", err
}
return string(bb), nil
}
func readFixed(r io.Reader, size int) ([]byte, error) {
bb := make([]byte, size)
_, err := io.ReadFull(r, bb)
return bb, err
}