1 files changed, 132 insertions, 0 deletions
diff --git a/vendor/github.com/jackc/pgx/v5/pgconn/internal/bgreader/bgreader.go b/vendor/github.com/jackc/pgx/v5/pgconn/internal/bgreader/bgreader.go
new file mode 100644
index 000000000..aa1a3d39c
--- /dev/null
+++ b/vendor/github.com/jackc/pgx/v5/pgconn/internal/bgreader/bgreader.go
@@ -0,0 +1,132 @@
+// Package bgreader provides a io.Reader that can optionally buffer reads in the background.
+package bgreader
+
+import (
+	"io"
+	"sync"
+
+	"github.com/jackc/pgx/v5/internal/iobufpool"
+)
+
+const (
+	bgReaderStatusStopped = iota
+	bgReaderStatusRunning
+	bgReaderStatusStopping
+)
+
+// BGReader is an io.Reader that can optionally buffer reads in the background. It is safe for concurrent use.
+type BGReader struct {
+	r io.Reader
+
+	cond           *sync.Cond
+	bgReaderStatus int32
+	readResults    []readResult
+}
+
+type readResult struct {
+	buf *[]byte
+	err error
+}
+
+// Start starts the backgrounder reader. If the background reader is already running this is a no-op. The background
+// reader will stop automatically when the underlying reader returns an error.
+func (r *BGReader) Start() {
+	r.cond.L.Lock()
+	defer r.cond.L.Unlock()
+
+	switch r.bgReaderStatus {
+	case bgReaderStatusStopped:
+		r.bgReaderStatus = bgReaderStatusRunning
+		go r.bgRead()
+	case bgReaderStatusRunning:
+		// no-op
+	case bgReaderStatusStopping:
+		r.bgReaderStatus = bgReaderStatusRunning
+	}
+}
+
+// Stop tells the background reader to stop after the in progress Read returns. It is safe to call Stop when the
+// background reader is not running.
+func (r *BGReader) Stop() {
+	r.cond.L.Lock()
+	defer r.cond.L.Unlock()
+
+	switch r.bgReaderStatus {
+	case bgReaderStatusStopped:
+		// no-op
+	case bgReaderStatusRunning:
+		r.bgReaderStatus = bgReaderStatusStopping
+	case bgReaderStatusStopping:
+		// no-op
+	}
+}
+
+func (r *BGReader) bgRead() {
+	keepReading := true
+	for keepReading {
+		buf := iobufpool.Get(8192)
+		n, err := r.r.Read(*buf)
+		*buf = (*buf)[:n]
+
+		r.cond.L.Lock()
+		r.readResults = append(r.readResults, readResult{buf: buf, err: err})
+		if r.bgReaderStatus == bgReaderStatusStopping || err != nil {
+			r.bgReaderStatus = bgReaderStatusStopped
+			keepReading = false
+		}
+		r.cond.L.Unlock()
+		r.cond.Broadcast()
+	}
+}
+
+// Read implements the io.Reader interface.
+func (r *BGReader) Read(p []byte) (int, error) {
+	r.cond.L.Lock()
+	defer r.cond.L.Unlock()
+
+	if len(r.readResults) > 0 {
+		return r.readFromReadResults(p)
+	}
+
+	// There are no unread background read results and the background reader is stopped.
+	if r.bgReaderStatus == bgReaderStatusStopped {
+		return r.r.Read(p)
+	}
+
+	// Wait for results from the background reader
+	for len(r.readResults) == 0 {
+		r.cond.Wait()
+	}
+	return r.readFromReadResults(p)
+}
+
+// readBackgroundResults reads a result previously read by the background reader. r.cond.L must be held.
+func (r *BGReader) readFromReadResults(p []byte) (int, error) {
+	buf := r.readResults[0].buf
+	var err error
+
+	n := copy(p, *buf)
+	if n == len(*buf) {
+		err = r.readResults[0].err
+		iobufpool.Put(buf)
+		if len(r.readResults) == 1 {
+			r.readResults = nil
+		} else {
+			r.readResults = r.readResults[1:]
+		}
+	} else {
+		*buf = (*buf)[n:]
+		r.readResults[0].buf = buf
+	}
+
+	return n, err
+}
+
+func New(r io.Reader) *BGReader {
+	return &BGReader{
+		r: r,
+		cond: &sync.Cond{
+			L: &sync.Mutex{},
+		},
+	}
+}