1 files changed, 78 insertions, 0 deletions
diff --git a/modules/util/io.go b/modules/util/io.go
new file mode 100644
index 0000000..1559b01
--- /dev/null
+++ b/modules/util/io.go
@@ -0,0 +1,78 @@
+// Copyright 2021 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package util
+
+import (
+	"bytes"
+	"errors"
+	"io"
+)
+
+// ReadAtMost reads at most len(buf) bytes from r into buf.
+// It returns the number of bytes copied. n is only less than len(buf) if r provides fewer bytes.
+// If EOF or ErrUnexpectedEOF occurs while reading, err will be nil.
+func ReadAtMost(r io.Reader, buf []byte) (n int, err error) {
+	n, err = io.ReadFull(r, buf)
+	if err == io.EOF || err == io.ErrUnexpectedEOF {
+		err = nil
+	}
+	return n, err
+}
+
+// ReadWithLimit reads at most "limit" bytes from r into buf.
+// If EOF or ErrUnexpectedEOF occurs while reading, err will be nil.
+func ReadWithLimit(r io.Reader, n int) (buf []byte, err error) {
+	return readWithLimit(r, 1024, n)
+}
+
+func readWithLimit(r io.Reader, batch, limit int) ([]byte, error) {
+	if limit <= batch {
+		buf := make([]byte, limit)
+		n, err := ReadAtMost(r, buf)
+		if err != nil {
+			return nil, err
+		}
+		return buf[:n], nil
+	}
+	res := bytes.NewBuffer(make([]byte, 0, batch))
+	bufFix := make([]byte, batch)
+	eof := false
+	for res.Len() < limit && !eof {
+		bufTmp := bufFix
+		if res.Len()+batch > limit {
+			bufTmp = bufFix[:limit-res.Len()]
+		}
+		n, err := io.ReadFull(r, bufTmp)
+		if err == io.EOF || err == io.ErrUnexpectedEOF {
+			eof = true
+		} else if err != nil {
+			return nil, err
+		}
+		if _, err = res.Write(bufTmp[:n]); err != nil {
+			return nil, err
+		}
+	}
+	return res.Bytes(), nil
+}
+
+// ErrNotEmpty is an error reported when there is a non-empty reader
+var ErrNotEmpty = errors.New("not-empty")
+
+// IsEmptyReader reads a reader and ensures it is empty
+func IsEmptyReader(r io.Reader) (err error) {
+	var buf [1]byte
+
+	for {
+		n, err := r.Read(buf[:])
+		if err != nil {
+			if err == io.EOF {
+				return nil
+			}
+			return err
+		}
+		if n > 0 {
+			return ErrNotEmpty
+		}
+	}
+}