Bound animated WebP decoding resources

QuickLook.Plugin/QuickLook.Plugin.ImageViewer/AnimatedImage/Providers/WebPAnimationInfo.cs

@@ -0,0 +1,206 @@
+// Copyright © 2017-2026 QL-Win Contributors
+//
+// This file is part of QuickLook program.
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+using System;
+using System.IO;
+
+namespace QuickLook.Plugin.ImageViewer.AnimatedImage.Providers;
+
+internal enum WebPAnimationInspectionStatus
+{
+    NotAnimated,
+    Animated,
+    Invalid
+}
+
+internal sealed class WebPAnimationInfo
+{
+    public int Width { get; set; }
+
+    public int Height { get; set; }
+
+    public int FrameCount { get; set; }
+}
+
+/// <summary>
+/// Reads only the WebP container metadata needed to decide whether an animation is safe to decode.
+/// Image data is deliberately skipped so a malformed file cannot allocate frame-sized buffers here.
+/// </summary>
+internal static class WebPAnimationInspector
+{
+    private const byte AnimationFlag = 0x02;
+
+    public static WebPAnimationInspectionStatus Inspect(
+        string fileName,
+        int maxFrameCount,
+        out WebPAnimationInfo info,
+        out string error)
+    {
+        info = new WebPAnimationInfo();
+        error = null;
+
+        try
+        {
+            using var stream = new FileStream(
+                fileName,
+                FileMode.Open,
+                FileAccess.Read,
+                FileShare.ReadWrite | FileShare.Delete);
+
+            if (stream.Length < 12)
+                return WebPAnimationInspectionStatus.NotAnimated;
+
+            var header = new byte[12];
+            ReadExactly(stream, header, header.Length);
+
+            if (!IsFourCc(header, 0, "RIFF") || !IsFourCc(header, 8, "WEBP"))
+                return WebPAnimationInspectionStatus.NotAnimated;
+
+            var riffSize = BitConverter.ToUInt32(header, 4);
+            if (riffSize < 4)
+                return Invalid(info, out error, "RIFF 容器长度无效");
+
+            var riffEnd = 8L + riffSize;
+            if (riffEnd > stream.Length)
+                return Invalid(info, out error, "RIFF 容器被截断");
+
+            var hasVp8x = false;
+            var animationFlagSet = false;
+            var hasAnimChunk = false;
+            var position = 12L;
+            var chunkHeader = new byte[16];
+
+            while (position + 8 <= riffEnd)
+            {
+                stream.Position = position;
+                ReadExactly(stream, chunkHeader, 8);
+
+                var chunkSize = BitConverter.ToUInt32(chunkHeader, 4);
+                var dataStart = position + 8;
+                var nextPosition = dataStart + chunkSize + (chunkSize & 1);
+
+                if (nextPosition < dataStart || nextPosition > riffEnd)
+                    return Invalid(info, out error, "WebP 数据块长度无效");
+
+                if (IsFourCc(chunkHeader, 0, "VP8X"))
+                {
+                    if (hasVp8x || chunkSize < 10)
+                        return Invalid(info, out error, "VP8X 数据块无效");
+
+                    hasVp8x = true;
+                    stream.Position = dataStart;
+                    ReadExactly(stream, chunkHeader, 10);
+
+                    animationFlagSet = (chunkHeader[0] & AnimationFlag) != 0;
+                    info.Width = ReadUInt24LittleEndian(chunkHeader, 4) + 1;
+                    info.Height = ReadUInt24LittleEndian(chunkHeader, 7) + 1;
+                }
+                else if (IsFourCc(chunkHeader, 0, "ANIM"))
+                {
+                    if (chunkSize < 6)
+                        return Invalid(info, out error, "ANIM 数据块无效");
+
+                    hasAnimChunk = true;
+                }
+                else if (IsFourCc(chunkHeader, 0, "ANMF"))
+                {
+                    if (chunkSize < 16 || !hasVp8x || info.Width <= 0 || info.Height <= 0)
+                        return Invalid(info, out error, "ANMF 数据块缺少有效的画布信息");
+
+                    if (info.FrameCount >= maxFrameCount)
+                        return Invalid(info, out error, $"动画帧数超过上限 {maxFrameCount}");
+
+                    stream.Position = dataStart;
+                    ReadExactly(stream, chunkHeader, 12);
+
+                    var frameX = ReadUInt24LittleEndian(chunkHeader, 0) * 2L;
+                    var frameY = ReadUInt24LittleEndian(chunkHeader, 3) * 2L;
+                    var frameWidth = ReadUInt24LittleEndian(chunkHeader, 6) + 1L;
+                    var frameHeight = ReadUInt24LittleEndian(chunkHeader, 9) + 1L;
+
+                    if (frameX + frameWidth > info.Width || frameY + frameHeight > info.Height)
+                        return Invalid(info, out error, "动画帧超出 WebP 画布范围");
+
+                    info.FrameCount++;
+                }
+
+                position = nextPosition;
+            }
+
+            if (!hasVp8x)
+            {
+                return info.FrameCount > 0
+                    ? Invalid(info, out error, "动画 WebP 缺少 VP8X 数据块")
+                    : WebPAnimationInspectionStatus.NotAnimated;
+            }
+
+            if (!animationFlagSet)
+            {
+                return info.FrameCount > 0
+                    ? Invalid(info, out error, "WebP 动画标志与 ANMF 数据块不一致")
+                    : WebPAnimationInspectionStatus.NotAnimated;
+            }
+
+            if (!hasAnimChunk || info.FrameCount < 2)
+                return Invalid(info, out error, "动画 WebP 的帧信息不完整");
+
+            return WebPAnimationInspectionStatus.Animated;
+        }
+        catch (Exception e) when (e is IOException || e is UnauthorizedAccessException || e is ArgumentException)
+        {
+            return Invalid(info, out error, e.Message);
+        }
+    }
+
+    private static WebPAnimationInspectionStatus Invalid(
+        WebPAnimationInfo info,
+        out string error,
+        string message)
+    {
+        error = message;
+        return WebPAnimationInspectionStatus.Invalid;
+    }
+
+    private static void ReadExactly(Stream stream, byte[] buffer, int count)
+    {
+        var offset = 0;
+
+        while (offset < count)
+        {
+            var read = stream.Read(buffer, offset, count - offset);
+            if (read == 0)
+                throw new EndOfStreamException("WebP 数据意外结束");
+
+            offset += read;
+        }
+    }
+
+    private static bool IsFourCc(byte[] buffer, int offset, string value)
+    {
+        return buffer[offset] == value[0]
+            && buffer[offset + 1] == value[1]
+            && buffer[offset + 2] == value[2]
+            && buffer[offset + 3] == value[3];
+    }
+
+    private static int ReadUInt24LittleEndian(byte[] buffer, int offset)
+    {
+        return buffer[offset]
+            | (buffer[offset + 1] << 8)
+            | (buffer[offset + 2] << 16);
+    }
+}