Fix package upload for files >32mb (go-gitea#20622)

* Rewind file before first read.
* Added tests.

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

modules/packages/hashed_buffer_test.go

@@ -0,0 +1,47 @@
+// Copyright 2022 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package packages
+
+import (
+	"fmt"
+	"io"
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestHashedBuffer(t *testing.T) {
+	cases := []struct {
+		MaxMemorySize int
+		Data          string
+		HashMD5       string
+		HashSHA1      string
+		HashSHA256    string
+		HashSHA512    string
+	}{
+		{5, "test", "098f6bcd4621d373cade4e832627b4f6", "a94a8fe5ccb19ba61c4c0873d391e987982fbbd3", "9f86d081884c7d659a2feaa0c55ad015a3bf4f1b2b0b822cd15d6c15b0f00a08", "ee26b0dd4af7e749aa1a8ee3c10ae9923f618980772e473f8819a5d4940e0db27ac185f8a0e1d5f84f88bc887fd67b143732c304cc5fa9ad8e6f57f50028a8ff"},
+		{5, "testtest", "05a671c66aefea124cc08b76ea6d30bb", "51abb9636078defbf888d8457a7c76f85c8f114c", "37268335dd6931045bdcdf92623ff819a64244b53d0e746d438797349d4da578", "125d6d03b32c84d492747f79cf0bf6e179d287f341384eb5d6d3197525ad6be8e6df0116032935698f99a09e265073d1d6c32c274591bf1d0a20ad67cba921bc"},
+	}
+
+	for _, c := range cases {
+		buf, err := CreateHashedBufferFromReader(strings.NewReader(c.Data), c.MaxMemorySize)
+		assert.NoError(t, err)
+
+		assert.EqualValues(t, len(c.Data), buf.Size())
+
+		data, err := io.ReadAll(buf)
+		assert.NoError(t, err)
+		assert.Equal(t, c.Data, string(data))
+
+		hashMD5, hashSHA1, hashSHA256, hashSHA512 := buf.Sums()
+		assert.Equal(t, c.HashMD5, fmt.Sprintf("%x", hashMD5))
+		assert.Equal(t, c.HashSHA1, fmt.Sprintf("%x", hashSHA1))
+		assert.Equal(t, c.HashSHA256, fmt.Sprintf("%x", hashSHA256))
+		assert.Equal(t, c.HashSHA512, fmt.Sprintf("%x", hashSHA512))
+
+		assert.NoError(t, buf.Close())
+	}
+}

modules/util/filebuffer/file_backed_buffer.go

@@ -103,35 +103,45 @@ func (b *FileBackedBuffer) Size() int64 {
 	return b.size
 }
 
-func (b *FileBackedBuffer) switchToReader() {
+func (b *FileBackedBuffer) switchToReader() error {
 	if b.reader != nil {
-		return
+		return nil
 	}
 
 	if b.file != nil {
+		if _, err := b.file.Seek(0, io.SeekStart); err != nil {
+			return err
+		}
 		b.reader = b.file
 	} else {
 		b.reader = bytes.NewReader(b.buffer.Bytes())
 	}
+	return nil
 }
 
 // Read implements io.Reader
 func (b *FileBackedBuffer) Read(p []byte) (int, error) {
-	b.switchToReader()
+	if err := b.switchToReader(); err != nil {
+		return 0, err
+	}
 
 	return b.reader.Read(p)
 }
 
 // ReadAt implements io.ReaderAt
 func (b *FileBackedBuffer) ReadAt(p []byte, off int64) (int, error) {
-	b.switchToReader()
+	if err := b.switchToReader(); err != nil {
+		return 0, err
+	}
 
 	return b.reader.ReadAt(p, off)
 }
 
 // Seek implements io.Seeker
 func (b *FileBackedBuffer) Seek(offset int64, whence int) (int64, error) {
-	b.switchToReader()
+	if err := b.switchToReader(); err != nil {
+		return 0, err
+	}
 
 	return b.reader.Seek(offset, whence)
 }

modules/util/filebuffer/file_backed_buffer_test.go

@@ -0,0 +1,36 @@
+// Copyright 2022 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package filebuffer
+
+import (
+	"io"
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestFileBackedBuffer(t *testing.T) {
+	cases := []struct {
+		MaxMemorySize int
+		Data          string
+	}{
+		{5, "test"},
+		{5, "testtest"},
+	}
+
+	for _, c := range cases {
+		buf, err := CreateFromReader(strings.NewReader(c.Data), c.MaxMemorySize)
+		assert.NoError(t, err)
+
+		assert.EqualValues(t, len(c.Data), buf.Size())
+
+		data, err := io.ReadAll(buf)
+		assert.NoError(t, err)
+		assert.Equal(t, c.Data, string(data))
+
+		assert.NoError(t, buf.Close())
+	}
+}