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buffered_reader.go
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buffered_reader.go
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package sockety
import (
"errors"
"io"
)
type bufferedReader struct {
source io.Reader
eof bool
buffer []byte
available offset
start offset
}
type BufferedReader interface {
Len() offset
MayHave(size offset) bool
ReadByte() (byte, error)
Read(target []byte) (offset, error)
Preload() error
}
func newBufferedReader(source io.Reader, buffer []byte) BufferedReader {
if err := validateReadBufferSize(offset(len(buffer))); err != nil {
panic(err)
}
return &bufferedReader{
source: source,
buffer: buffer,
}
}
func (b *bufferedReader) loadBytes() error {
bytes, err := b.source.Read(b.buffer[b.start+b.available:])
if err != nil {
return err
}
b.available += offset(bytes)
return nil
}
func (b *bufferedReader) Preload() error {
if b.available > 0 {
return nil
} else if b.eof {
return io.EOF
}
return b.loadBytes()
}
func (b *bufferedReader) ensure(size offset) error {
// TODO: Think if there is more performant way
if offset(len(b.buffer))-b.start < size {
b.buffer = append(b.buffer[b.start:], b.buffer[:b.start]...)
b.start = 0
}
for b.available < size {
err := b.loadBytes()
if err != nil {
return err
}
}
return nil
}
func (b *bufferedReader) collect(size offset) {
b.start += size
b.available -= size
if b.available == 0 {
b.start = 0
}
}
func (b *bufferedReader) Len() offset {
return b.available
}
func (b *bufferedReader) MayHave(size offset) bool {
if b.eof {
return b.available >= size
}
return true
}
func (b *bufferedReader) ReadByte() (byte, error) {
err := b.ensure(1)
if err != nil {
return 0, err
}
result := b.buffer[b.start]
b.collect(1)
return result, nil
}
func (b *bufferedReader) Read(target []byte) (offset, error) {
// Set up
o := offset(0)
l := offset(len(target))
// Read rest
for o < l {
left := l - o
// Read current available bytes
if b.available >= left {
copy(target[o:], b.buffer[b.start:b.start+left])
b.collect(left)
return l, nil
} else if b.available > 0 {
copy(target[o:], b.buffer[b.start:b.start+b.available])
o += b.available
b.collect(b.available)
}
err := b.loadBytes()
if err != nil {
return o, err
}
}
return o, nil
}
type limitedBufferedReader struct {
b BufferedReader
size offset
}
func limitBufferedReader(reader BufferedReader, size offset) BufferedReader {
return &limitedBufferedReader{
b: reader,
size: size,
}
}
func (b *limitedBufferedReader) collect(size offset) error {
if size > b.size {
return errors.New("sockety.limitedBufferedReader.collect: out of bounds")
}
b.size -= size
return nil
}
func (b *limitedBufferedReader) Len() offset {
l := b.b.Len()
if b.size > l {
return l
}
return b.size
}
func (b *limitedBufferedReader) MayHave(size offset) bool {
return size <= b.size && b.b.MayHave(size)
}
func (b *limitedBufferedReader) ReadByte() (byte, error) {
err := b.collect(1)
if err != nil {
return 0, err
}
return b.b.ReadByte()
}
func (b *limitedBufferedReader) Read(target []byte) (offset, error) {
err := b.collect(offset(len(target)))
if err != nil {
return 0, err
}
return b.b.Read(target)
}
func (b *limitedBufferedReader) Preload() error {
if b.size == 0 {
return io.EOF
}
return b.b.Preload()
}