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readbuffer.go
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readbuffer.go
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package readbuffer
import (
"io"
"time"
)
const (
readBufSize = 1 << 10
readTimeout = 100 * time.Millisecond
)
type ReadBuffer struct {
buf []byte
index int
len int
src io.Reader
finished bool
}
func New(stream io.Reader) ReadBuffer {
return ReadBuffer{
buf: make([]byte, readBufSize),
src: stream,
}
}
func (r *ReadBuffer) Get(n int) (res []byte, err error) {
n, res = r.appendFromBuffer(n, res)
if n == 0 {
return
}
for err = r.load(); err == nil; err = r.load() {
n, res = r.appendFromBuffer(n, res)
if n == 0 {
return
}
time.Sleep(readTimeout)
}
if n == 0 {
return
}
if err == io.EOF {
r.finished = true
err = nil
} else {
return nil, err
}
n, res = r.appendFromBuffer(n, res)
if n > 0 && r.finished {
return res, io.EOF
}
return
}
func (r *ReadBuffer) appendFromBuffer(n int, dst []byte) (int, []byte) {
length := r.len - r.index
if length >= n {
res := append(dst, r.buf[r.index:r.index+n]...)
r.index += n
return 0, res
}
res := append(dst, r.buf[r.index:r.len]...)
r.index = r.len
return n - length, res
}
func (r *ReadBuffer) load() error {
n, err := r.src.Read(r.buf)
r.len = n
r.index = 0
return err
}