1 files changed, 247 insertions, 0 deletions
diff --git a/src/image/gif/reader_test.go b/src/image/gif/reader_test.go
new file mode 100644
index 000000000..7b6f50436
--- /dev/null
+++ b/src/image/gif/reader_test.go
@@ -0,0 +1,247 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package gif
+
+import (
+	"bytes"
+	"compress/lzw"
+	"image"
+	"image/color"
+	"reflect"
+	"testing"
+)
+
+// header, palette and trailer are parts of a valid 2x1 GIF image.
+const (
+	headerStr = "GIF89a" +
+		"\x02\x00\x01\x00" + // width=2, height=1
+		"\x80\x00\x00" // headerFields=(a color map of 2 pixels), backgroundIndex, aspect
+	paletteStr = "\x10\x20\x30\x40\x50\x60" // the color map, also known as a palette
+	trailerStr = "\x3b"
+)
+
+// lzwEncode returns an LZW encoding (with 2-bit literals) of n zeroes.
+func lzwEncode(n int) []byte {
+	b := &bytes.Buffer{}
+	w := lzw.NewWriter(b, lzw.LSB, 2)
+	w.Write(make([]byte, n))
+	w.Close()
+	return b.Bytes()
+}
+
+func TestDecode(t *testing.T) {
+	testCases := []struct {
+		nPix    int  // The number of pixels in the image data.
+		extra   bool // Whether to write an extra block after the LZW-encoded data.
+		wantErr error
+	}{
+		{0, false, errNotEnough},
+		{1, false, errNotEnough},
+		{2, false, nil},
+		{2, true, errTooMuch},
+		{3, false, errTooMuch},
+	}
+	for _, tc := range testCases {
+		b := &bytes.Buffer{}
+		b.WriteString(headerStr)
+		b.WriteString(paletteStr)
+		// Write an image with bounds 2x1 but tc.nPix pixels. If tc.nPix != 2
+		// then this should result in an invalid GIF image. First, write a
+		// magic 0x2c (image descriptor) byte, bounds=(0,0)-(2,1), a flags
+		// byte, and 2-bit LZW literals.
+		b.WriteString("\x2c\x00\x00\x00\x00\x02\x00\x01\x00\x00\x02")
+		if tc.nPix > 0 {
+			enc := lzwEncode(tc.nPix)
+			if len(enc) > 0xff {
+				t.Errorf("nPix=%d, extra=%t: compressed length %d is too large", tc.nPix, tc.extra, len(enc))
+				continue
+			}
+			b.WriteByte(byte(len(enc)))
+			b.Write(enc)
+		}
+		if tc.extra {
+			b.WriteString("\x01\x02") // A 1-byte payload with an 0x02 byte.
+		}
+		b.WriteByte(0x00) // An empty block signifies the end of the image data.
+		b.WriteString(trailerStr)
+
+		got, err := Decode(b)
+		if err != tc.wantErr {
+			t.Errorf("nPix=%d, extra=%t\ngot  %v\nwant %v", tc.nPix, tc.extra, err, tc.wantErr)
+		}
+
+		if tc.wantErr != nil {
+			continue
+		}
+		want := &image.Paletted{
+			Pix:    []uint8{0, 0},
+			Stride: 2,
+			Rect:   image.Rect(0, 0, 2, 1),
+			Palette: color.Palette{
+				color.RGBA{0x10, 0x20, 0x30, 0xff},
+				color.RGBA{0x40, 0x50, 0x60, 0xff},
+			},
+		}
+		if !reflect.DeepEqual(got, want) {
+			t.Errorf("nPix=%d, extra=%t\ngot  %v\nwant %v", tc.nPix, tc.extra, got, want)
+		}
+	}
+}
+
+func TestTransparentIndex(t *testing.T) {
+	b := &bytes.Buffer{}
+	b.WriteString(headerStr)
+	b.WriteString(paletteStr)
+	for transparentIndex := 0; transparentIndex < 3; transparentIndex++ {
+		if transparentIndex < 2 {
+			// Write the graphic control for the transparent index.
+			b.WriteString("\x21\xf9\x00\x01\x00\x00")
+			b.WriteByte(byte(transparentIndex))
+			b.WriteByte(0)
+		}
+		// Write an image with bounds 2x1, as per TestDecode.
+		b.WriteString("\x2c\x00\x00\x00\x00\x02\x00\x01\x00\x00\x02")
+		enc := lzwEncode(2)
+		if len(enc) > 0xff {
+			t.Fatalf("compressed length %d is too large", len(enc))
+		}
+		b.WriteByte(byte(len(enc)))
+		b.Write(enc)
+		b.WriteByte(0x00)
+	}
+	b.WriteString(trailerStr)
+
+	g, err := DecodeAll(b)
+	if err != nil {
+		t.Fatalf("DecodeAll: %v", err)
+	}
+	c0 := color.RGBA{paletteStr[0], paletteStr[1], paletteStr[2], 0xff}
+	c1 := color.RGBA{paletteStr[3], paletteStr[4], paletteStr[5], 0xff}
+	cz := color.RGBA{}
+	wants := []color.Palette{
+		{cz, c1},
+		{c0, cz},
+		{c0, c1},
+	}
+	if len(g.Image) != len(wants) {
+		t.Fatalf("got %d images, want %d", len(g.Image), len(wants))
+	}
+	for i, want := range wants {
+		got := g.Image[i].Palette
+		if !reflect.DeepEqual(got, want) {
+			t.Errorf("palette #%d:\ngot  %v\nwant %v", i, got, want)
+		}
+	}
+}
+
+// testGIF is a simple GIF that we can modify to test different scenarios.
+var testGIF = []byte{
+	'G', 'I', 'F', '8', '9', 'a',
+	1, 0, 1, 0, // w=1, h=1 (6)
+	128, 0, 0, // headerFields, bg, aspect (10)
+	0, 0, 0, 1, 1, 1, // color map and graphics control (13)
+	0x21, 0xf9, 0x04, 0x00, 0x00, 0x00, 0xff, 0x00, // (19)
+	// frame 1 (0,0 - 1,1)
+	0x2c,
+	0x00, 0x00, 0x00, 0x00,
+	0x01, 0x00, 0x01, 0x00, // (32)
+	0x00,
+	0x02, 0x02, 0x4c, 0x01, 0x00, // lzw pixels
+	// trailer
+	0x3b,
+}
+
+func try(t *testing.T, b []byte, want string) {
+	_, err := DecodeAll(bytes.NewReader(b))
+	var got string
+	if err != nil {
+		got = err.Error()
+	}
+	if got != want {
+		t.Fatalf("got %v, want %v", got, want)
+	}
+}
+
+func TestBounds(t *testing.T) {
+	// Make a local copy of testGIF.
+	gif := make([]byte, len(testGIF))
+	copy(gif, testGIF)
+	// Make the bounds too big, just by one.
+	gif[32] = 2
+	want := "gif: frame bounds larger than image bounds"
+	try(t, gif, want)
+
+	// Make the bounds too small; does not trigger bounds
+	// check, but now there's too much data.
+	gif[32] = 0
+	want = "gif: too much image data"
+	try(t, gif, want)
+	gif[32] = 1
+
+	// Make the bounds really big, expect an error.
+	want = "gif: frame bounds larger than image bounds"
+	for i := 0; i < 4; i++ {
+		gif[32+i] = 0xff
+	}
+	try(t, gif, want)
+}
+
+func TestNoPalette(t *testing.T) {
+	b := &bytes.Buffer{}
+
+	// Manufacture a GIF with no palette, so any pixel at all
+	// will be invalid.
+	b.WriteString(headerStr[:len(headerStr)-3])
+	b.WriteString("\x00\x00\x00") // No global palette.
+
+	// Image descriptor: 2x1, no local palette.
+	b.WriteString("\x2c\x00\x00\x00\x00\x02\x00\x01\x00\x00\x02")
+
+	// Encode the pixels: neither is in range, because there is no palette.
+	pix := []byte{0, 128}
+	enc := &bytes.Buffer{}
+	w := lzw.NewWriter(enc, lzw.LSB, 2)
+	w.Write(pix)
+	w.Close()
+	b.WriteByte(byte(len(enc.Bytes())))
+	b.Write(enc.Bytes())
+	b.WriteByte(0x00) // An empty block signifies the end of the image data.
+
+	b.WriteString(trailerStr)
+
+	try(t, b.Bytes(), "gif: invalid pixel value")
+}
+
+func TestPixelOutsidePaletteRange(t *testing.T) {
+	for _, pval := range []byte{0, 1, 2, 3, 255} {
+		b := &bytes.Buffer{}
+
+		// Manufacture a GIF with a 2 color palette.
+		b.WriteString(headerStr)
+		b.WriteString(paletteStr)
+
+		// Image descriptor: 2x1, no local palette.
+		b.WriteString("\x2c\x00\x00\x00\x00\x02\x00\x01\x00\x00\x02")
+
+		// Encode the pixels; some pvals trigger the expected error.
+		pix := []byte{pval, pval}
+		enc := &bytes.Buffer{}
+		w := lzw.NewWriter(enc, lzw.LSB, 2)
+		w.Write(pix)
+		w.Close()
+		b.WriteByte(byte(len(enc.Bytes())))
+		b.Write(enc.Bytes())
+		b.WriteByte(0x00) // An empty block signifies the end of the image data.
+
+		b.WriteString(trailerStr)
+
+		// No error expected, unless the pixels are beyond the 2 color palette.
+		want := ""
+		if pval >= 2 {
+			want = "gif: invalid pixel value"
+		}
+		try(t, b.Bytes(), want)
+	}
+}