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// Package streamio contains wrappers intended for turning gRPC streams
// that send/receive messages with a []byte field into io.Writers and
// io.Readers.
//
package streamio
import (
"io"
"os"
"strconv"
)
func init() {
bufSize64, err := strconv.ParseInt(os.Getenv("GITALY_STREAMIO_WRITE_BUFFER_SIZE"), 10, 32)
if err == nil && bufSize64 > 0 {
WriteBufferSize = int(bufSize64)
}
}
// NewReader turns receiver into an io.Reader. Errors from the receiver
// function are passed on unmodified. This means receiver should emit
// io.EOF when done.
func NewReader(receiver func() ([]byte, error)) io.Reader {
return &receiveReader{receiver: receiver}
}
type receiveReader struct {
receiver func() ([]byte, error)
data []byte
err error
}
func (rr *receiveReader) Read(p []byte) (int, error) {
if len(rr.data) == 0 {
rr.data, rr.err = rr.receiver()
}
n := copy(p, rr.data)
rr.data = rr.data[n:]
if len(rr.data) == 0 {
return n, rr.err
}
return n, nil
}
// WriteTo implements io.WriterTo.
func (rr *receiveReader) WriteTo(w io.Writer) (int64, error) {
var written int64
// Deal with left-over state in rr.data and rr.err, if any
if len(rr.data) > 0 {
n, err := w.Write(rr.data)
written += int64(n)
if err != nil {
return written, err
}
}
if rr.err != nil {
return written, rr.err
}
// Consume the response stream
var errRead, errWrite error
var n int
var buf []byte
for errWrite == nil && errRead != io.EOF {
buf, errRead = rr.receiver()
if errRead != nil && errRead != io.EOF {
return written, errRead
}
if len(buf) > 0 {
n, errWrite = w.Write(buf)
written += int64(n)
}
}
return written, errWrite
}
// NewWriter turns sender into an io.Writer. The sender callback will
// receive []byte arguments of length at most WriteBufferSize.
func NewWriter(sender func(p []byte) error) io.Writer {
return &sendWriter{sender: sender}
}
// WriteBufferSize is the largest []byte that Write() will pass to its
// underlying send function. This value can be changed at runtime using
// the GITALY_STREAMIO_WRITE_BUFFER_SIZE environment variable.
var WriteBufferSize = 128 * 1024
type sendWriter struct {
sender func([]byte) error
}
func (sw *sendWriter) Write(p []byte) (int, error) {
var sent int
for len(p) > 0 {
chunkSize := len(p)
if chunkSize > WriteBufferSize {
chunkSize = WriteBufferSize
}
if err := sw.sender(p[:chunkSize]); err != nil {
return sent, err
}
sent += chunkSize
p = p[chunkSize:]
}
return sent, nil
}
// ReadFrom implements io.ReaderFrom.
func (sw *sendWriter) ReadFrom(r io.Reader) (int64, error) {
var nRead int64
buf := make([]byte, WriteBufferSize)
var errRead, errSend error
for errSend == nil && errRead != io.EOF {
var n int
n, errRead = r.Read(buf)
nRead += int64(n)
if errRead != nil && errRead != io.EOF {
return nRead, errRead
}
if n > 0 {
errSend = sw.sender(buf[:n])
}
}
return nRead, errSend
}
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