From 6392506ab43493cc6af71c817d26cd6cef63315d Mon Sep 17 00:00:00 2001
From: Jason Nelson <jason@carbonmade.com>
Date: Tue, 30 Jan 2024 10:01:47 -0800
Subject: [PATCH 01/30] Eliminate allocation in PhotoshopReader

---
 MetadataExtractor/Formats/Photoshop/PhotoshopReader.cs | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/MetadataExtractor/Formats/Photoshop/PhotoshopReader.cs b/MetadataExtractor/Formats/Photoshop/PhotoshopReader.cs
index 198d3e746..c410f84d7 100644
--- a/MetadataExtractor/Formats/Photoshop/PhotoshopReader.cs
+++ b/MetadataExtractor/Formats/Photoshop/PhotoshopReader.cs
@@ -53,12 +53,15 @@ public IReadOnlyList<Directory> Extract(SequentialReader reader, int length)
             // http://www.adobe.com/devnet-apps/photoshop/fileformatashtml/#50577409_pgfId-1037504
             var pos = 0;
             int clippingPathCount = 0;
+
+            Span<byte> signature = stackalloc byte[4];
+
             while (pos < length)
             {
                 try
                 {
                     // 4 bytes for the signature ("8BIM", "PHUT", etc.)
-                    var signature = reader.GetString(4, Encoding.UTF8);
+                    reader.GetBytes(signature);
                     pos += 4;
 
                     // 2 bytes for the resource identifier (tag type).
@@ -106,7 +109,7 @@ public IReadOnlyList<Directory> Extract(SequentialReader reader, int length)
                     }
 
                     // Skip any unsupported IRBs
-                    if (signature != "8BIM")
+                    if (!signature.SequenceEqual("8BIM"u8))
                         continue;
 
                     switch (tagType)

From 722774aa77779cd8c121cfd6257142f8e5ef7587 Mon Sep 17 00:00:00 2001
From: Jason Nelson <jason@carbonmade.com>
Date: Wed, 31 Jan 2024 09:57:57 -0800
Subject: [PATCH 02/30] Use switch expressions

---
 ...lympusCameraSettingsMakernoteDescriptor.cs | 145 +++++-------------
 1 file changed, 42 insertions(+), 103 deletions(-)

diff --git a/MetadataExtractor/Formats/Exif/makernotes/OlympusCameraSettingsMakernoteDescriptor.cs b/MetadataExtractor/Formats/Exif/makernotes/OlympusCameraSettingsMakernoteDescriptor.cs
index e61711690..ea409176e 100644
--- a/MetadataExtractor/Formats/Exif/makernotes/OlympusCameraSettingsMakernoteDescriptor.cs
+++ b/MetadataExtractor/Formats/Exif/makernotes/OlympusCameraSettingsMakernoteDescriptor.cs
@@ -160,30 +160,16 @@ public sealed class OlympusCameraSettingsMakernoteDescriptor(OlympusCameraSettin
                 return null;
 
             var sb = new StringBuilder();
-            switch (values[0])
+            sb.Append(values[0] switch
             {
-                case 0:
-                    sb.Append("Single AF");
-                    break;
-                case 1:
-                    sb.Append("Sequential shooting AF");
-                    break;
-                case 2:
-                    sb.Append("Continuous AF");
-                    break;
-                case 3:
-                    sb.Append("Multi AF");
-                    break;
-                case 4:
-                    sb.Append("Face detect");
-                    break;
-                case 10:
-                    sb.Append("MF");
-                    break;
-                default:
-                    sb.Append("Unknown (" + values[0] + ")");
-                    break;
-            }
+                0 => "Single AF",
+                1 => "Sequential shooting AF",
+                2 => "Continuous AF",
+                3 => "Multi AF",
+                4 => "Face detect",
+                10 => "MF",
+                _ => $"Unknown ({values[0]})"
+            });
 
             if (values.Length > 1)
             {
@@ -231,18 +217,12 @@ public sealed class OlympusCameraSettingsMakernoteDescriptor(OlympusCameraSettin
 
             var sb = new StringBuilder();
 
-            switch (values[0])
+            sb.Append(values[0] switch
             {
-                case 0:
-                    sb.Append("AF not used");
-                    break;
-                case 1:
-                    sb.Append("AF used");
-                    break;
-                default:
-                    sb.Append("Unknown (" + values[0] + ")");
-                    break;
-            }
+                0 => "AF not used",
+                1 => "AF used",
+                _ => $"Unknown ({values[0]})"
+            });
 
             if (values.Length > 1)
                 sb.Append("; " + values[1]);
@@ -385,24 +365,14 @@ public sealed class OlympusCameraSettingsMakernoteDescriptor(OlympusCameraSettin
 
             var sb = new StringBuilder();
 
-            switch (values[0])
+            sb.Append(values[0] switch
             {
-                case 0:
-                    sb.Append("Off");
-                    break;
-                case 3:
-                    sb.Append("TTL");
-                    break;
-                case 4:
-                    sb.Append("Auto");
-                    break;
-                case 5:
-                    sb.Append("Manual");
-                    break;
-                default:
-                    sb.Append("Unknown (" + values[0] + ")");
-                    break;
-            }
+                0 => sb.Append("Off"),
+                3 => sb.Append("TTL"),
+                4 => sb.Append("Auto"),
+                5 => sb.Append("Manual"),
+                _ => $"Unknown ({values[0]})"
+            });
 
             for (var i = 1; i < values.Length; i++)
                 sb.Append("; ").Append(values[i]);
@@ -692,33 +662,17 @@ public sealed class OlympusCameraSettingsMakernoteDescriptor(OlympusCameraSettin
                 return null;
 
             var sb = new StringBuilder();
-            switch (values[0])
+            sb.Append(values[0] switch
             {
-                case 1:
-                    sb.Append("Vivid");
-                    break;
-                case 2:
-                    sb.Append("Natural");
-                    break;
-                case 3:
-                    sb.Append("Muted");
-                    break;
-                case 4:
-                    sb.Append("Portrait");
-                    break;
-                case 5:
-                    sb.Append("i-Enhance");
-                    break;
-                case 256:
-                    sb.Append("Monotone");
-                    break;
-                case 512:
-                    sb.Append("Sepia");
-                    break;
-                default:
-                    sb.Append("Unknown (").Append(values[0]).Append(')');
-                    break;
-            }
+                1 => "Vivid",
+                2 => "Natural",
+                3 => "Muted",
+                4 => "Portrait",
+                5 => "i-Enhance",
+                256 => "Monotone",
+                512 => "Sepia",
+                _ => $"Unknown ({values[0]})"
+            });
 
             if (values.Length > 1)
                 sb.Append("; ").Append(values[1]);
@@ -822,33 +776,18 @@ public sealed class OlympusCameraSettingsMakernoteDescriptor(OlympusCameraSettin
                     sb.Append("Partial Color " + values[i] + "; ");
                 else if (i == 4)
                 {
-                    switch (values[i])
+                    sb.Append(values[i] switch
                     {
-                        case 0x0000:
-                            sb.Append("No Effect");
-                            break;
-                        case 0x8010:
-                            sb.Append("Star Light");
-                            break;
-                        case 0x8020:
-                            sb.Append("Pin Hole");
-                            break;
-                        case 0x8030:
-                            sb.Append("Frame");
-                            break;
-                        case 0x8040:
-                            sb.Append("Soft Focus");
-                            break;
-                        case 0x8050:
-                            sb.Append("White Edge");
-                            break;
-                        case 0x8060:
-                            sb.Append("B&W");
-                            break;
-                        default:
-                            sb.Append("Unknown (").Append(values[i]).Append(')');
-                            break;
-                    }
+                        0x0000 => "No Effect",
+                        0x8010 => "Star Light",
+                        0x8020 => "Pin Hole",
+                        0x8030 => "Frame",
+                        0x8040 => "Soft Focus",
+                        0x8050 => "White Edge",
+                        0x8060 => "B&W",
+                        _ => $"Unknown ({values[i]})"
+                    });
+
                     sb.Append("; ");
                 }
                 else if (i == 6)

From 4df2738fcff02d80ef10beb83b85a676e6264784 Mon Sep 17 00:00:00 2001
From: Jason Nelson <jason@carbonmade.com>
Date: Wed, 31 Jan 2024 09:58:41 -0800
Subject: [PATCH 03/30] Add BufferReader

---
 MetadataExtractor/IO/BufferReader.cs | 157 +++++++++++++++++++++++++++
 1 file changed, 157 insertions(+)
 create mode 100644 MetadataExtractor/IO/BufferReader.cs

diff --git a/MetadataExtractor/IO/BufferReader.cs b/MetadataExtractor/IO/BufferReader.cs
new file mode 100644
index 000000000..5141f1485
--- /dev/null
+++ b/MetadataExtractor/IO/BufferReader.cs
@@ -0,0 +1,157 @@
+// Copyright (c) Drew Noakes and contributors. All Rights Reserved. Licensed under the Apache License, Version 2.0. See LICENSE in the project root for license information.
+
+using System.Buffers.Binary;
+
+namespace MetadataExtractor.IO;
+
+internal ref struct BufferReader(ReadOnlySpan<byte> bytes, bool isBigEndian)
+{
+    private readonly ReadOnlySpan<byte> _bytes = bytes;
+    private int _position = 0;
+    private bool _isBigEndian = isBigEndian;
+
+    public long Position => _position;
+
+    public byte GetByte()
+    {
+        if (_position >= _bytes.Length)
+            throw new IOException("End of data reached.");
+
+        return _bytes[_position++];
+    }
+
+    public void GetBytes(scoped Span<byte> bytes)
+    {
+        if (_position + bytes.Length > _bytes.Length)
+            throw new IOException("End of data reached.");
+
+        _bytes.Slice(_position, bytes.Length).CopyTo(bytes);
+        _position += bytes.Length;
+    }
+
+    public byte[] GetBytes(int count)
+    {
+        if (_position + count > _bytes.Length)
+            throw new IOException("End of data reached.");
+
+        var bytes = new byte[count];
+
+        _bytes.Slice(0, count).CopyTo(bytes);
+        _position += count;
+        return bytes;
+    }
+
+    public int Available()
+    {
+        return _bytes.Length - _position;
+    }
+
+    public void Skip(long n)
+    {
+        if (n < 0)
+            throw new ArgumentException("n must be zero or greater.");
+
+        if (_position + n > _bytes.Length)
+            throw new IOException("End of data reached.");
+
+        _position += unchecked((int)n);
+    }
+
+    public bool TrySkip(long n)
+    {
+        if (n < 0)
+            throw new ArgumentException("n must be zero or greater.");
+
+        _position += unchecked((int)n);
+
+        if (_position > _bytes.Length)
+        {
+            _position = _bytes.Length;
+            return false;
+        }
+
+        return true;
+    }
+
+    public sbyte GetSByte()
+    {
+        return unchecked((sbyte)GetByte());
+    }
+
+    public ushort GetUInt16()
+    {
+        Span<byte> bytes = stackalloc byte[2];
+
+        GetBytes(bytes);
+
+        return _isBigEndian
+            ? BinaryPrimitives.ReadUInt16BigEndian(bytes)
+            : BinaryPrimitives.ReadUInt16LittleEndian(bytes);
+    }
+
+    public short GetInt16()
+    {
+        Span<byte> bytes = stackalloc byte[2];
+
+        GetBytes(bytes);
+
+        return _isBigEndian
+            ? BinaryPrimitives.ReadInt16BigEndian(bytes)
+            : BinaryPrimitives.ReadInt16LittleEndian(bytes);
+    }
+
+    public uint GetUInt32()
+    {
+        Span<byte> bytes = stackalloc byte[4];
+
+        GetBytes(bytes);
+
+        return _isBigEndian
+            ? BinaryPrimitives.ReadUInt32BigEndian(bytes)
+            : BinaryPrimitives.ReadUInt32LittleEndian(bytes);
+    }
+
+    public int GetInt32()
+    {
+        Span<byte> bytes = stackalloc byte[4];
+
+        GetBytes(bytes);
+
+        return _isBigEndian
+            ? BinaryPrimitives.ReadInt32BigEndian(bytes)
+            : BinaryPrimitives.ReadInt32LittleEndian(bytes);
+    }
+
+    public long GetInt64()
+    {
+        Span<byte> bytes = stackalloc byte[8];
+        GetBytes(bytes);
+
+        return _isBigEndian
+            ? BinaryPrimitives.ReadInt64BigEndian(bytes)
+            : BinaryPrimitives.ReadInt64LittleEndian(bytes);
+    }
+
+    public ulong GetUInt64()
+    {
+        Span<byte> bytes = stackalloc byte[8];
+        GetBytes(bytes);
+
+        return _isBigEndian
+            ? BinaryPrimitives.ReadUInt64BigEndian(bytes)
+            : BinaryPrimitives.ReadUInt64LittleEndian(bytes);
+    }
+
+    public string GetString(int bytesRequested, Encoding encoding)
+    {
+        // This check is important on .NET Framework
+        if (bytesRequested is 0)
+            return "";
+
+        Span<byte> bytes = bytesRequested < 256 ? stackalloc byte[bytesRequested] : new byte[bytesRequested];
+
+        GetBytes(bytes);
+
+        return encoding.GetString(bytes);
+    }
+}

From 224eade1c217025a30c0954aa2795f05a6b443a9 Mon Sep 17 00:00:00 2001
From: Jason Nelson <jason@carbonmade.com>
Date: Wed, 31 Jan 2024 09:59:12 -0800
Subject: [PATCH 04/30] Eliminate two allocations in FlirReader

---
 MetadataExtractor/Formats/Flir/FlirReader.cs | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/MetadataExtractor/Formats/Flir/FlirReader.cs b/MetadataExtractor/Formats/Flir/FlirReader.cs
index 529590953..253beb20c 100644
--- a/MetadataExtractor/Formats/Flir/FlirReader.cs
+++ b/MetadataExtractor/Formats/Flir/FlirReader.cs
@@ -153,8 +153,9 @@ public IEnumerable<Directory> Extract(IndexedReader reader)
                     directory.Set(TagRawValueMedian, reader2.GetUInt16(TagRawValueMedian));
                     directory.Set(TagRawValueRange, reader2.GetUInt16(TagRawValueRange));
 
-                    var dateTimeBytes = reader2.GetBytes(TagDateTimeOriginal, 10);
-                    var dateTimeReader = new SequentialByteArrayReader(dateTimeBytes, isMotorolaByteOrder: false);
+                    Span<byte> dateTimeBytes = stackalloc byte[10];
+                    reader2.GetBytes(TagDateTimeOriginal, dateTimeBytes);
+                    var dateTimeReader = new BufferReader(dateTimeBytes, isBigEndian: false);
                     var tm = dateTimeReader.GetUInt32();
                     var ss = dateTimeReader.GetUInt32() & 0xffff;
                     var tz = dateTimeReader.GetInt16();

From 461a6b422542f1472c9e91d7766a6614f80fc651 Mon Sep 17 00:00:00 2001
From: Jason Nelson <jason@carbonmade.com>
Date: Wed, 31 Jan 2024 10:03:48 -0800
Subject: [PATCH 05/30] Eliminate allocation in OlympusMakernoteDirectory

---
 .../Formats/Exif/makernotes/OlympusMakernoteDirectory.cs      | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/MetadataExtractor/Formats/Exif/makernotes/OlympusMakernoteDirectory.cs b/MetadataExtractor/Formats/Exif/makernotes/OlympusMakernoteDirectory.cs
index 20de3f2a5..9afa7668a 100644
--- a/MetadataExtractor/Formats/Exif/makernotes/OlympusMakernoteDirectory.cs
+++ b/MetadataExtractor/Formats/Exif/makernotes/OlympusMakernoteDirectory.cs
@@ -448,9 +448,9 @@ public override void Set(int tagType, object value)
                 base.Set(tagType, value);
         }
 
-        private void ProcessCameraSettings(byte[] bytes)
+        private void ProcessCameraSettings(ReadOnlySpan<byte> bytes)
         {
-            var reader = new SequentialByteArrayReader(bytes);
+            var reader = new BufferReader(bytes, isBigEndian: true);
             var count = bytes.Length / 4;
 
             for (var i = 0; i < count; i++)

From cbe2d098395b692b3351df481d7decd57bc26830 Mon Sep 17 00:00:00 2001
From: Jason Nelson <jason@carbonmade.com>
Date: Wed, 31 Jan 2024 10:08:41 -0800
Subject: [PATCH 06/30] Eliminate various allocations in BplistReader

---
 .../Formats/Apple/BplistReader.cs              | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/MetadataExtractor/Formats/Apple/BplistReader.cs b/MetadataExtractor/Formats/Apple/BplistReader.cs
index 6f13eb3cb..8258fc52b 100644
--- a/MetadataExtractor/Formats/Apple/BplistReader.cs
+++ b/MetadataExtractor/Formats/Apple/BplistReader.cs
@@ -43,7 +43,7 @@ public static PropertyListResults Parse(byte[] bplist)
 
         Trailer trailer = ReadTrailer();
 
-        SequentialByteArrayReader reader = new(bplist, baseIndex: checked((int)(trailer.OffsetTableOffset + trailer.TopObject)));
+        var reader = new BufferReader(bplist.AsSpan(checked((int)(trailer.OffsetTableOffset + trailer.TopObject))), isBigEndian: true);
 
         int[] offsets = new int[(int)trailer.NumObjects];
 
@@ -63,7 +63,7 @@ public static PropertyListResults Parse(byte[] bplist)
 
         for (int i = 0; i < offsets.Length; i++)
         {
-            reader = new SequentialByteArrayReader(bplist, offsets[i]);
+            reader = new BufferReader(bplist.AsSpan(offsets[i]), isBigEndian: true);
 
             byte b = reader.GetByte();
 
@@ -73,13 +73,13 @@ public static PropertyListResults Parse(byte[] bplist)
             object obj = objectFormat switch
             {
                 // dict
-                0x0D => HandleDict(marker),
+                0x0D => HandleDict(ref reader, marker),
                 // string (ASCII)
                 0x05 => reader.GetString(bytesRequested: marker & 0x0F, Encoding.ASCII),
                 // data
-                0x04 => HandleData(marker),
+                0x04 => HandleData(ref reader, marker),
                 // int
-                0x01 => HandleInt(marker),
+                0x01 => HandleInt(ref reader, marker),
                 // unknown
                 _ => throw new NotSupportedException($"Unsupported object format {objectFormat:X2}.")
             };
@@ -91,7 +91,7 @@ public static PropertyListResults Parse(byte[] bplist)
 
         Trailer ReadTrailer()
         {
-            SequentialByteArrayReader reader = new(bplist, bplist.Length - Trailer.SizeBytes);
+            var reader = new BufferReader(bplist.AsSpan(bplist.Length - Trailer.SizeBytes), isBigEndian: true);
 
             // Skip 5-byte unused values, 1-byte sort version.
             reader.Skip(6);
@@ -106,7 +106,7 @@ Trailer ReadTrailer()
             };
         }
 
-        object HandleInt(byte marker)
+        static object HandleInt(ref BufferReader reader, byte marker)
         {
             return marker switch
             {
@@ -118,7 +118,7 @@ object HandleInt(byte marker)
             };
         }
 
-        Dictionary<byte, byte> HandleDict(byte count)
+        static Dictionary<byte, byte> HandleDict(ref BufferReader reader, byte count)
         {
             var keyRefs = new byte[count];
 
@@ -137,7 +137,7 @@ Dictionary<byte, byte> HandleDict(byte count)
             return map;
         }
 
-        object HandleData(byte marker)
+        object HandleData(ref BufferReader reader, byte marker)
         {
             int byteCount = marker;
 

From a26f6f3edc8838970e1e008056fb21029f73dbd9 Mon Sep 17 00:00:00 2001
From: Jason Nelson <jason@carbonmade.com>
Date: Wed, 31 Jan 2024 10:09:37 -0800
Subject: [PATCH 07/30] Eliminate allocation in JpegReader

---
 MetadataExtractor/Formats/Jpeg/JpegReader.cs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/MetadataExtractor/Formats/Jpeg/JpegReader.cs b/MetadataExtractor/Formats/Jpeg/JpegReader.cs
index c9bd4bfae..78499c0a1 100644
--- a/MetadataExtractor/Formats/Jpeg/JpegReader.cs
+++ b/MetadataExtractor/Formats/Jpeg/JpegReader.cs
@@ -29,7 +29,7 @@ public JpegDirectory Extract(JpegSegment segment)
             // The value of TagCompressionType is determined by the segment type found
             directory.Set(JpegDirectory.TagCompressionType, (int)segment.Type - (int)JpegSegmentType.Sof0);
 
-            SequentialReader reader = new SequentialByteArrayReader(segment.Bytes);
+            var reader = new BufferReader(segment.Span, isBigEndian: true);
 
             try
             {

From d84ae433c7b391d40b5d110c9822f66054e3fb78 Mon Sep 17 00:00:00 2001
From: Jason Nelson <jason@carbonmade.com>
Date: Wed, 31 Jan 2024 10:11:04 -0800
Subject: [PATCH 08/30] Eliminate allocation in PngChromaticities

---
 .../Formats/Png/PngChromaticities.cs          | 25 +++++++------------
 1 file changed, 9 insertions(+), 16 deletions(-)

diff --git a/MetadataExtractor/Formats/Png/PngChromaticities.cs b/MetadataExtractor/Formats/Png/PngChromaticities.cs
index 9d6ab6897..16f6cb75b 100644
--- a/MetadataExtractor/Formats/Png/PngChromaticities.cs
+++ b/MetadataExtractor/Formats/Png/PngChromaticities.cs
@@ -20,23 +20,16 @@ public PngChromaticities(byte[] bytes)
             if (bytes.Length != 8 * 4)
                 throw new PngProcessingException("Invalid number of bytes");
 
-            var reader = new SequentialByteArrayReader(bytes);
+            var reader = new BufferReader(bytes, isBigEndian: true);
 
-            try
-            {
-                WhitePointX = reader.GetInt32();
-                WhitePointY = reader.GetInt32();
-                RedX = reader.GetInt32();
-                RedY = reader.GetInt32();
-                GreenX = reader.GetInt32();
-                GreenY = reader.GetInt32();
-                BlueX = reader.GetInt32();
-                BlueY = reader.GetInt32();
-            }
-            catch (IOException ex)
-            {
-                throw new PngProcessingException(ex);
-            }
+            WhitePointX = reader.GetInt32();
+            WhitePointY = reader.GetInt32();
+            RedX = reader.GetInt32();
+            RedY = reader.GetInt32();
+            GreenX = reader.GetInt32();
+            GreenY = reader.GetInt32();
+            BlueX = reader.GetInt32();
+            BlueY = reader.GetInt32();
         }
     }
 }

From 6f33bc8f5e0b4bafd148482a56ff50fa2fadc382 Mon Sep 17 00:00:00 2001
From: Jason Nelson <jason@carbonmade.com>
Date: Wed, 31 Jan 2024 10:12:13 -0800
Subject: [PATCH 09/30] Eliminate allocation in PngDescriptor

---
 MetadataExtractor/Formats/Png/PngDescriptor.cs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/MetadataExtractor/Formats/Png/PngDescriptor.cs b/MetadataExtractor/Formats/Png/PngDescriptor.cs
index 1f019323e..9894e5bcd 100644
--- a/MetadataExtractor/Formats/Png/PngDescriptor.cs
+++ b/MetadataExtractor/Formats/Png/PngDescriptor.cs
@@ -82,10 +82,10 @@ public sealed class PngDescriptor(PngDirectory directory)
             if (bytes is null)
                 return null;
 
-            var reader = new SequentialByteArrayReader(bytes);
+            var reader = new BufferReader(bytes, isBigEndian: true);
             try
             {
-                // TODO do we need to normalise these based upon the bit depth?
+                // TODO do we need to normalize these based upon the bit depth?
                 switch (bytes.Length)
                 {
                     case 1:

From 5d34c552b55d33313e41b01687b340615de6a2a3 Mon Sep 17 00:00:00 2001
From: Jason Nelson <jason@carbonmade.com>
Date: Wed, 31 Jan 2024 10:12:42 -0800
Subject: [PATCH 10/30] Eliminate allocation in PngHeader

---
 MetadataExtractor/Formats/Png/PngHeader.cs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/MetadataExtractor/Formats/Png/PngHeader.cs b/MetadataExtractor/Formats/Png/PngHeader.cs
index 4dd9db709..4cac12ccc 100644
--- a/MetadataExtractor/Formats/Png/PngHeader.cs
+++ b/MetadataExtractor/Formats/Png/PngHeader.cs
@@ -11,7 +11,7 @@ public PngHeader(byte[] bytes)
             if (bytes.Length != 13)
                 throw new PngProcessingException("PNG header chunk must have exactly 13 data bytes");
 
-            var reader = new SequentialByteArrayReader(bytes);
+            var reader = new BufferReader(bytes, isBigEndian: true);
 
             ImageWidth = reader.GetInt32();
             ImageHeight = reader.GetInt32();

From 189d66fb5387239ad25801678ecd2f73ef7f6e60 Mon Sep 17 00:00:00 2001
From: Jason Nelson <jason@carbonmade.com>
Date: Wed, 31 Jan 2024 10:16:32 -0800
Subject: [PATCH 11/30] Eliminate a few allocations in PngMetadataReader

---
 MetadataExtractor/Formats/Png/PngMetadataReader.cs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/MetadataExtractor/Formats/Png/PngMetadataReader.cs b/MetadataExtractor/Formats/Png/PngMetadataReader.cs
index 73f2802d3..21a0742a8 100644
--- a/MetadataExtractor/Formats/Png/PngMetadataReader.cs
+++ b/MetadataExtractor/Formats/Png/PngMetadataReader.cs
@@ -295,7 +295,7 @@ private static IEnumerable<Directory> ProcessChunk(PngChunk chunk)
             }
             else if (chunkType == PngChunkType.tIME)
             {
-                var reader = new SequentialByteArrayReader(bytes);
+                var reader = new BufferReader(bytes, isBigEndian: true);
                 var year = reader.GetUInt16();
                 var month = reader.GetByte();
                 int day = reader.GetByte();
@@ -316,7 +316,7 @@ private static IEnumerable<Directory> ProcessChunk(PngChunk chunk)
             }
             else if (chunkType == PngChunkType.pHYs)
             {
-                var reader = new SequentialByteArrayReader(bytes);
+                var reader = new BufferReader(bytes, isBigEndian: true);
                 var pixelsPerUnitX = reader.GetInt32();
                 var pixelsPerUnitY = reader.GetInt32();
                 var unitSpecifier = reader.GetSByte();

From 76c687e66978d590683e9f821739e37437ad1f0a Mon Sep 17 00:00:00 2001
From: Jason Nelson <jason@carbonmade.com>
Date: Wed, 31 Jan 2024 10:16:41 -0800
Subject: [PATCH 12/30] Eliminate allocation in WavFactHandler

---
 MetadataExtractor/Formats/Wav/WavFactHandler.cs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/MetadataExtractor/Formats/Wav/WavFactHandler.cs b/MetadataExtractor/Formats/Wav/WavFactHandler.cs
index dac863e59..825b155cb 100644
--- a/MetadataExtractor/Formats/Wav/WavFactHandler.cs
+++ b/MetadataExtractor/Formats/Wav/WavFactHandler.cs
@@ -25,7 +25,7 @@ public WavFactHandler(List<Directory> directories)
 
         protected override void Populate(WavFactDirectory directory, byte[] payload)
         {
-            var reader = new SequentialByteArrayReader(payload, isMotorolaByteOrder: false);
+            var reader = new BufferReader(payload, isBigEndian: false);
             directory.Set(TagSampleLength, reader.GetUInt32());
         }
     }

From 27c9846d995821e90b2c9d6d8c1bae7fa347006c Mon Sep 17 00:00:00 2001
From: Jason Nelson <jason@carbonmade.com>
Date: Wed, 31 Jan 2024 13:01:38 -0800
Subject: [PATCH 13/30] Use Assert.Debug

---
 MetadataExtractor/IO/BufferReader.cs | 25 +++++++++++--------------
 1 file changed, 11 insertions(+), 14 deletions(-)

diff --git a/MetadataExtractor/IO/BufferReader.cs b/MetadataExtractor/IO/BufferReader.cs
index 5141f1485..256c02469 100644
--- a/MetadataExtractor/IO/BufferReader.cs
+++ b/MetadataExtractor/IO/BufferReader.cs
@@ -10,20 +10,18 @@ internal ref struct BufferReader(ReadOnlySpan<byte> bytes, bool isBigEndian)
     private int _position = 0;
     private bool _isBigEndian = isBigEndian;
 
-    public long Position => _position;
+    public int Position => _position;
 
     public byte GetByte()
     {
-        if (_position >= _bytes.Length)
-            throw new IOException("End of data reached.");
+        Debug.Assert(_position >= _bytes.Length, "attempted to read past end of data");
 
         return _bytes[_position++];
     }
 
     public void GetBytes(scoped Span<byte> bytes)
     {
-        if (_position + bytes.Length > _bytes.Length)
-            throw new IOException("End of data reached.");
+        Debug.Assert(_position + bytes.Length > _bytes.Length, "attempted to read past end of data");
 
         _bytes.Slice(_position, bytes.Length).CopyTo(bytes);
         _position += bytes.Length;
@@ -31,8 +29,7 @@ public void GetBytes(scoped Span<byte> bytes)
 
     public byte[] GetBytes(int count)
     {
-        if (_position + count > _bytes.Length)
-            throw new IOException("End of data reached.");
+        Debug.Assert(_position + count > _bytes.Length, "attempted to read past end of data");
 
         var bytes = new byte[count];
 
@@ -41,15 +38,14 @@ public byte[] GetBytes(int count)
         return bytes;
     }
 
-    public int Available()
+    public int Available
     {
-        return _bytes.Length - _position;
+        get => _bytes.Length - _position;
     }
 
     public void Skip(long n)
     {
-        if (n < 0)
-            throw new ArgumentException("n must be zero or greater.");
+        Debug.Assert(n < 0, "n must be zero or greater.");
 
         if (_position + n > _bytes.Length)
             throw new IOException("End of data reached.");
@@ -59,8 +55,7 @@ public void Skip(long n)
 
     public bool TrySkip(long n)
     {
-        if (n < 0)
-            throw new ArgumentException("n must be zero or greater.");
+        Debug.Assert(n < 0, "n must be zero or greater.");
 
         _position += unchecked((int)n);
 
@@ -148,7 +143,9 @@ public string GetString(int bytesRequested, Encoding encoding)
         if (bytesRequested is 0)
             return "";
 
-        Span<byte> bytes = bytesRequested < 256 ? stackalloc byte[bytesRequested] : new byte[bytesRequested];
+        Span<byte> bytes = bytesRequested <= 256
+            ? stackalloc byte[bytesRequested]
+            : new byte[bytesRequested];
 
         GetBytes(bytes);
 

From 5bb02b133f88734ac9fbed1a13bd50f71dde52fe Mon Sep 17 00:00:00 2001
From: Jason Nelson <jason@carbonmade.com>
Date: Wed, 31 Jan 2024 13:05:09 -0800
Subject: [PATCH 14/30] Ensure BufferReader operates on buffers <= 2GB

---
 MetadataExtractor/IO/BufferReader.cs | 21 ++++++++-------------
 1 file changed, 8 insertions(+), 13 deletions(-)

diff --git a/MetadataExtractor/IO/BufferReader.cs b/MetadataExtractor/IO/BufferReader.cs
index 256c02469..36caf359e 100644
--- a/MetadataExtractor/IO/BufferReader.cs
+++ b/MetadataExtractor/IO/BufferReader.cs
@@ -38,26 +38,21 @@ public byte[] GetBytes(int count)
         return bytes;
     }
 
-    public int Available
-    {
-        get => _bytes.Length - _position;
-    }
+    public readonly int Available => _bytes.Length - _position;
 
-    public void Skip(long n)
+    public void Skip(int n)
     {
-        Debug.Assert(n < 0, "n must be zero or greater.");
-
-        if (_position + n > _bytes.Length)
-            throw new IOException("End of data reached.");
+        Debug.Assert(n < 0, "n must be zero or greater");
+        Debug.Assert(_position + n > _bytes.Length, "attempted to advance past end of data");
 
-        _position += unchecked((int)n);
+        _position += n;
     }
 
-    public bool TrySkip(long n)
+    public bool TrySkip(int n)
     {
-        Debug.Assert(n < 0, "n must be zero or greater.");
+        Debug.Assert(n < 0, "n must be zero or greater");
 
-        _position += unchecked((int)n);
+        _position += n;
 
         if (_position > _bytes.Length)
         {

From f53892bec93063bdb6d9bdfad5cf335e901ccf4d Mon Sep 17 00:00:00 2001
From: Jason Nelson <jason@carbonmade.com>
Date: Wed, 31 Jan 2024 13:05:29 -0800
Subject: [PATCH 15/30] Fix offset in BufferReader.GetBytes

---
 MetadataExtractor/IO/BufferReader.cs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/MetadataExtractor/IO/BufferReader.cs b/MetadataExtractor/IO/BufferReader.cs
index 36caf359e..afbad7bdb 100644
--- a/MetadataExtractor/IO/BufferReader.cs
+++ b/MetadataExtractor/IO/BufferReader.cs
@@ -33,7 +33,7 @@ public byte[] GetBytes(int count)
 
         var bytes = new byte[count];
 
-        _bytes.Slice(0, count).CopyTo(bytes);
+        _bytes.Slice(_position, count).CopyTo(bytes);
         _position += count;
         return bytes;
     }

From a89e1f039d70d7b0ce2a4f57562912a7e491bfe2 Mon Sep 17 00:00:00 2001
From: Jason Nelson <jason@carbonmade.com>
Date: Wed, 31 Jan 2024 13:06:11 -0800
Subject: [PATCH 16/30] Rename BufferReader.Skip -> Advance

---
 MetadataExtractor/Formats/Apple/BplistReader.cs | 2 +-
 MetadataExtractor/IO/BufferReader.cs            | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/MetadataExtractor/Formats/Apple/BplistReader.cs b/MetadataExtractor/Formats/Apple/BplistReader.cs
index 8258fc52b..e591bf2d6 100644
--- a/MetadataExtractor/Formats/Apple/BplistReader.cs
+++ b/MetadataExtractor/Formats/Apple/BplistReader.cs
@@ -94,7 +94,7 @@ Trailer ReadTrailer()
             var reader = new BufferReader(bplist.AsSpan(bplist.Length - Trailer.SizeBytes), isBigEndian: true);
 
             // Skip 5-byte unused values, 1-byte sort version.
-            reader.Skip(6);
+            reader.Advance(6);
 
             return new Trailer
             {
diff --git a/MetadataExtractor/IO/BufferReader.cs b/MetadataExtractor/IO/BufferReader.cs
index afbad7bdb..8b9e5b30e 100644
--- a/MetadataExtractor/IO/BufferReader.cs
+++ b/MetadataExtractor/IO/BufferReader.cs
@@ -40,7 +40,7 @@ public byte[] GetBytes(int count)
 
     public readonly int Available => _bytes.Length - _position;
 
-    public void Skip(int n)
+    public void Advance(int n)
     {
         Debug.Assert(n < 0, "n must be zero or greater");
         Debug.Assert(_position + n > _bytes.Length, "attempted to advance past end of data");
@@ -48,7 +48,7 @@ public void Skip(int n)
         _position += n;
     }
 
-    public bool TrySkip(int n)
+    public bool TryAdvance(int n)
     {
         Debug.Assert(n < 0, "n must be zero or greater");
 

From db65fa5c81af218adfe9e6b2645860ff2b58f76d Mon Sep 17 00:00:00 2001
From: Jason Nelson <jason@carbonmade.com>
Date: Wed, 31 Jan 2024 13:15:11 -0800
Subject: [PATCH 17/30] Fix assert order

---
 MetadataExtractor/IO/BufferReader.cs | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/MetadataExtractor/IO/BufferReader.cs b/MetadataExtractor/IO/BufferReader.cs
index 8b9e5b30e..03c0b8cfb 100644
--- a/MetadataExtractor/IO/BufferReader.cs
+++ b/MetadataExtractor/IO/BufferReader.cs
@@ -14,14 +14,14 @@ internal ref struct BufferReader(ReadOnlySpan<byte> bytes, bool isBigEndian)
 
     public byte GetByte()
     {
-        Debug.Assert(_position >= _bytes.Length, "attempted to read past end of data");
+        Debug.Assert(_position < _bytes.Length, "attempted to read past end of data");
 
         return _bytes[_position++];
     }
 
     public void GetBytes(scoped Span<byte> bytes)
     {
-        Debug.Assert(_position + bytes.Length > _bytes.Length, "attempted to read past end of data");
+        Debug.Assert(_position + bytes.Length <= _bytes.Length, "attempted to read past end of data");
 
         _bytes.Slice(_position, bytes.Length).CopyTo(bytes);
         _position += bytes.Length;
@@ -29,7 +29,7 @@ public void GetBytes(scoped Span<byte> bytes)
 
     public byte[] GetBytes(int count)
     {
-        Debug.Assert(_position + count > _bytes.Length, "attempted to read past end of data");
+        Debug.Assert(_position + count <= _bytes.Length, "attempted to read past end of data");
 
         var bytes = new byte[count];
 
@@ -42,15 +42,15 @@ public byte[] GetBytes(int count)
 
     public void Advance(int n)
     {
-        Debug.Assert(n < 0, "n must be zero or greater");
-        Debug.Assert(_position + n > _bytes.Length, "attempted to advance past end of data");
+        Debug.Assert(n >= 0, "n must be zero or greater");
+        Debug.Assert(_position + n <= _bytes.Length, "attempted to advance past end of data");
 
         _position += n;
     }
 
     public bool TryAdvance(int n)
     {
-        Debug.Assert(n < 0, "n must be zero or greater");
+        Debug.Assert(n >= 0, "n must be zero or greater");
 
         _position += n;
 

From f7ee2721636246bec12a614ad4326f442417bda5 Mon Sep 17 00:00:00 2001
From: Jason Nelson <jason@carbonmade.com>
Date: Thu, 1 Feb 2024 09:13:33 -0800
Subject: [PATCH 18/30] Verify JpegSegment sizes before reading data

---
 MetadataExtractor/Formats/Jpeg/JpegReader.cs | 58 ++++++++++++--------
 1 file changed, 34 insertions(+), 24 deletions(-)

diff --git a/MetadataExtractor/Formats/Jpeg/JpegReader.cs b/MetadataExtractor/Formats/Jpeg/JpegReader.cs
index 78499c0a1..1ea210b36 100644
--- a/MetadataExtractor/Formats/Jpeg/JpegReader.cs
+++ b/MetadataExtractor/Formats/Jpeg/JpegReader.cs
@@ -29,35 +29,45 @@ public JpegDirectory Extract(JpegSegment segment)
             // The value of TagCompressionType is determined by the segment type found
             directory.Set(JpegDirectory.TagCompressionType, (int)segment.Type - (int)JpegSegmentType.Sof0);
 
+            const int JpegHeaderSize = 1 + 2 + 2 + 1;
+
+            if (segment.Span.Length < JpegHeaderSize)
+            {
+                directory.AddError("Insufficient bytes for JPEG segment header.");
+
+                return directory;
+            }
+
             var reader = new BufferReader(segment.Span, isBigEndian: true);
 
-            try
+            directory.Set(JpegDirectory.TagDataPrecision, reader.GetByte());
+            directory.Set(JpegDirectory.TagImageHeight, reader.GetUInt16());
+            directory.Set(JpegDirectory.TagImageWidth, reader.GetUInt16());
+
+            var componentCount = reader.GetByte();
+
+            directory.Set(JpegDirectory.TagNumberOfComponents, componentCount);
+
+            const int JpegComponentSize = 1 + 1 + 1;
+
+            if (reader.Available < componentCount * JpegComponentSize)
             {
-                directory.Set(JpegDirectory.TagDataPrecision, reader.GetByte());
-                directory.Set(JpegDirectory.TagImageHeight, reader.GetUInt16());
-                directory.Set(JpegDirectory.TagImageWidth, reader.GetUInt16());
-
-                var componentCount = reader.GetByte();
-
-                directory.Set(JpegDirectory.TagNumberOfComponents, componentCount);
-
-                // For each component, there are three bytes of data:
-                // 1 - Component ID: 1 = Y, 2 = Cb, 3 = Cr, 4 = I, 5 = Q
-                // 2 - Sampling factors: bit 0-3 vertical, 4-7 horizontal
-                // 3 - Quantization table number
-
-                for (var i = 0; i < componentCount; i++)
-                {
-                    var componentId = reader.GetByte();
-                    var samplingFactorByte = reader.GetByte();
-                    var quantizationTableNumber = reader.GetByte();
-                    var component = new JpegComponent(componentId, samplingFactorByte, quantizationTableNumber);
-                    directory.Set(JpegDirectory.TagComponentData1 + i, component);
-                }
+                directory.AddError("Insufficient bytes for JPEG the requested number of JPEG components.");
+                return directory;
             }
-            catch (IOException ex)
+
+            // For each component, there are three bytes of data:
+            // 1 - Component ID: 1 = Y, 2 = Cb, 3 = Cr, 4 = I, 5 = Q
+            // 2 - Sampling factors: bit 0-3 vertical, 4-7 horizontal
+            // 3 - Quantization table number
+
+            for (var i = 0; i < componentCount; i++)
             {
-                directory.AddError(ex.Message);
+                var componentId = reader.GetByte();
+                var samplingFactorByte = reader.GetByte();
+                var quantizationTableNumber = reader.GetByte();
+                var component = new JpegComponent(componentId, samplingFactorByte, quantizationTableNumber);
+                directory.Set(JpegDirectory.TagComponentData1 + i, component);
             }
 
             return directory;

From 94eec47d53d4dbec8ff3c46f521464d47151c21b Mon Sep 17 00:00:00 2001
From: Jason Nelson <jason@carbonmade.com>
Date: Thu, 1 Feb 2024 09:15:16 -0800
Subject: [PATCH 19/30] Bring back exceptions on BufferReader

---
 MetadataExtractor/IO/BufferReader.cs | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/MetadataExtractor/IO/BufferReader.cs b/MetadataExtractor/IO/BufferReader.cs
index 03c0b8cfb..455f47b8a 100644
--- a/MetadataExtractor/IO/BufferReader.cs
+++ b/MetadataExtractor/IO/BufferReader.cs
@@ -21,7 +21,8 @@ public byte GetByte()
 
     public void GetBytes(scoped Span<byte> bytes)
     {
-        Debug.Assert(_position + bytes.Length <= _bytes.Length, "attempted to read past end of data");
+        if (_position + bytes.Length > _bytes.Length)
+            throw new IOException("End of data reached.");
 
         _bytes.Slice(_position, bytes.Length).CopyTo(bytes);
         _position += bytes.Length;
@@ -29,7 +30,8 @@ public void GetBytes(scoped Span<byte> bytes)
 
     public byte[] GetBytes(int count)
     {
-        Debug.Assert(_position + count <= _bytes.Length, "attempted to read past end of data");
+        if (_position + count > _bytes.Length)
+            throw new IOException("End of data reached.");
 
         var bytes = new byte[count];
 
@@ -43,7 +45,9 @@ public byte[] GetBytes(int count)
     public void Advance(int n)
     {
         Debug.Assert(n >= 0, "n must be zero or greater");
-        Debug.Assert(_position + n <= _bytes.Length, "attempted to advance past end of data");
+
+        if (_position + n > _bytes.Length)
+            throw new IOException("End of data reached.");
 
         _position += n;
     }

From 73143a747008e6d3f16f5f93a8773894ad1c3b73 Mon Sep 17 00:00:00 2001
From: Jason Nelson <jason@carbonmade.com>
Date: Thu, 1 Feb 2024 09:20:08 -0800
Subject: [PATCH 20/30] Fix switch statement

---
 .../OlympusCameraSettingsMakernoteDescriptor.cs           | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/MetadataExtractor/Formats/Exif/makernotes/OlympusCameraSettingsMakernoteDescriptor.cs b/MetadataExtractor/Formats/Exif/makernotes/OlympusCameraSettingsMakernoteDescriptor.cs
index ea409176e..5aef68328 100644
--- a/MetadataExtractor/Formats/Exif/makernotes/OlympusCameraSettingsMakernoteDescriptor.cs
+++ b/MetadataExtractor/Formats/Exif/makernotes/OlympusCameraSettingsMakernoteDescriptor.cs
@@ -367,10 +367,10 @@ public sealed class OlympusCameraSettingsMakernoteDescriptor(OlympusCameraSettin
 
             sb.Append(values[0] switch
             {
-                0 => sb.Append("Off"),
-                3 => sb.Append("TTL"),
-                4 => sb.Append("Auto"),
-                5 => sb.Append("Manual"),
+                0 => "Off",
+                3 => "TTL",
+                4 => "Auto",
+                5 => "Manual",
                 _ => $"Unknown ({values[0]})"
             });
 

From 945686f346ec73293f36377904cafe20ff05ccbc Mon Sep 17 00:00:00 2001
From: Jason Nelson <jason@carbonmade.com>
Date: Thu, 1 Feb 2024 09:32:24 -0800
Subject: [PATCH 21/30] Slice span to avoid extra copy in BufferReader

---
 MetadataExtractor/IO/BufferReader.cs | 30 ++++++++++++----------------
 1 file changed, 13 insertions(+), 17 deletions(-)

diff --git a/MetadataExtractor/IO/BufferReader.cs b/MetadataExtractor/IO/BufferReader.cs
index 455f47b8a..0c298cb61 100644
--- a/MetadataExtractor/IO/BufferReader.cs
+++ b/MetadataExtractor/IO/BufferReader.cs
@@ -69,14 +69,13 @@ public bool TryAdvance(int n)
 
     public sbyte GetSByte()
     {
-        return unchecked((sbyte)GetByte());
+        return unchecked((sbyte)_bytes[_position++]);
     }
 
     public ushort GetUInt16()
     {
-        Span<byte> bytes = stackalloc byte[2];
-
-        GetBytes(bytes);
+        var bytes = _bytes.Slice(_position, 2);
+        _position += 2;
 
         return _isBigEndian
             ? BinaryPrimitives.ReadUInt16BigEndian(bytes)
@@ -85,9 +84,8 @@ public ushort GetUInt16()
 
     public short GetInt16()
     {
-        Span<byte> bytes = stackalloc byte[2];
-
-        GetBytes(bytes);
+        var bytes = _bytes.Slice(_position, 2);
+        _position += 2;
 
         return _isBigEndian
             ? BinaryPrimitives.ReadInt16BigEndian(bytes)
@@ -96,9 +94,8 @@ public short GetInt16()
 
     public uint GetUInt32()
     {
-        Span<byte> bytes = stackalloc byte[4];
-
-        GetBytes(bytes);
+        var bytes = _bytes.Slice(_position, 4);
+        _position += 4;
 
         return _isBigEndian
             ? BinaryPrimitives.ReadUInt32BigEndian(bytes)
@@ -107,9 +104,8 @@ public uint GetUInt32()
 
     public int GetInt32()
     {
-        Span<byte> bytes = stackalloc byte[4];
-
-        GetBytes(bytes);
+        var bytes = _bytes.Slice(_position, 4);
+        _position += 4;
 
         return _isBigEndian
             ? BinaryPrimitives.ReadInt32BigEndian(bytes)
@@ -118,8 +114,8 @@ public int GetInt32()
 
     public long GetInt64()
     {
-        Span<byte> bytes = stackalloc byte[8];
-        GetBytes(bytes);
+        var bytes = _bytes.Slice(_position, 8);
+        _position += 8;
 
         return _isBigEndian
             ? BinaryPrimitives.ReadInt64BigEndian(bytes)
@@ -128,8 +124,8 @@ public long GetInt64()
 
     public ulong GetUInt64()
     {
-        Span<byte> bytes = stackalloc byte[8];
-        GetBytes(bytes);
+        var bytes = _bytes.Slice(_position, 8);
+        _position += 8;
 
         return _isBigEndian
             ? BinaryPrimitives.ReadUInt64BigEndian(bytes)

From 5205495c29aee25f4a1882cfd4791540284b30dd Mon Sep 17 00:00:00 2001
From: Jason Nelson <jason@carbonmade.com>
Date: Thu, 1 Feb 2024 09:50:35 -0800
Subject: [PATCH 22/30] Validate buffer length when reading PNG chunks

---
 .../Formats/Png/PngMetadataReader.cs          | 44 +++++++++++++------
 1 file changed, 31 insertions(+), 13 deletions(-)

diff --git a/MetadataExtractor/Formats/Png/PngMetadataReader.cs b/MetadataExtractor/Formats/Png/PngMetadataReader.cs
index 21a0742a8..d2bcfdee2 100644
--- a/MetadataExtractor/Formats/Png/PngMetadataReader.cs
+++ b/MetadataExtractor/Formats/Png/PngMetadataReader.cs
@@ -295,32 +295,50 @@ private static IEnumerable<Directory> ProcessChunk(PngChunk chunk)
             }
             else if (chunkType == PngChunkType.tIME)
             {
-                var reader = new BufferReader(bytes, isBigEndian: true);
-                var year = reader.GetUInt16();
-                var month = reader.GetByte();
-                int day = reader.GetByte();
-                int hour = reader.GetByte();
-                int minute = reader.GetByte();
-                int second = reader.GetByte();
                 var directory = new PngDirectory(PngChunkType.tIME);
-                if (DateUtil.IsValidDate(year, month, day) && DateUtil.IsValidTime(hour, minute, second))
+
+                if (bytes.Length < 2 + 1 + 1 + 1 + 1 + 1)
                 {
-                    var time = new DateTime(year, month, day, hour, minute, second, DateTimeKind.Unspecified);
-                    directory.Set(PngDirectory.TagLastModificationTime, time);
+                    directory.AddError("Insufficient bytes for PNG tIME chunk.");
                 }
                 else
                 {
-                    directory.AddError($"PNG tIME data describes an invalid date/time: year={year} month={month} day={day} hour={hour} minute={minute} second={second}");
+                    var reader = new BufferReader(bytes, isBigEndian: true);
+
+                    var year = reader.GetUInt16();
+                    var month = reader.GetByte();
+                    int day = reader.GetByte();
+                    int hour = reader.GetByte();
+                    int minute = reader.GetByte();
+                    int second = reader.GetByte();
+
+                    if (DateUtil.IsValidDate(year, month, day) && DateUtil.IsValidTime(hour, minute, second))
+                    {
+                        var time = new DateTime(year, month, day, hour, minute, second, DateTimeKind.Unspecified);
+                        directory.Set(PngDirectory.TagLastModificationTime, time);
+                    }
+                    else
+                    {
+                        directory.AddError($"PNG tIME data describes an invalid date/time: year={year} month={month} day={day} hour={hour} minute={minute} second={second}");
+                    }
+                    yield return directory;
                 }
-                yield return directory;
             }
             else if (chunkType == PngChunkType.pHYs)
             {
+                var directory = new PngDirectory(PngChunkType.pHYs);
+
+                if (bytes.Length < 4 + 4 + 1)
+                {
+                    directory.AddError("Insufficient bytes for PNG pHYs chunk.");
+                }
+
                 var reader = new BufferReader(bytes, isBigEndian: true);
+
                 var pixelsPerUnitX = reader.GetInt32();
                 var pixelsPerUnitY = reader.GetInt32();
                 var unitSpecifier = reader.GetSByte();
-                var directory = new PngDirectory(PngChunkType.pHYs);
+
                 directory.Set(PngDirectory.TagPixelsPerUnitX, pixelsPerUnitX);
                 directory.Set(PngDirectory.TagPixelsPerUnitY, pixelsPerUnitY);
                 directory.Set(PngDirectory.TagUnitSpecifier, unitSpecifier);

From e6d86bda5ef02802ff0557f854e249e6cb652cff Mon Sep 17 00:00:00 2001
From: Jason Nelson <jason@carbonmade.com>
Date: Fri, 2 Feb 2024 11:00:42 -0800
Subject: [PATCH 23/30] Ensure the BufferReader can't advance past the end of
 data

---
 MetadataExtractor/IO/BufferReader.cs | 19 ++++++++++---------
 1 file changed, 10 insertions(+), 9 deletions(-)

diff --git a/MetadataExtractor/IO/BufferReader.cs b/MetadataExtractor/IO/BufferReader.cs
index 0c298cb61..4b365745d 100644
--- a/MetadataExtractor/IO/BufferReader.cs
+++ b/MetadataExtractor/IO/BufferReader.cs
@@ -10,11 +10,14 @@ internal ref struct BufferReader(ReadOnlySpan<byte> bytes, bool isBigEndian)
     private int _position = 0;
     private bool _isBigEndian = isBigEndian;
 
+    public readonly int Available => _bytes.Length - _position;
+
     public int Position => _position;
 
     public byte GetByte()
     {
-        Debug.Assert(_position < _bytes.Length, "attempted to read past end of data");
+        if (_position >= _bytes.Length)
+            throw new IOException("End of data reached.");
 
         return _bytes[_position++];
     }
@@ -40,8 +43,6 @@ public byte[] GetBytes(int count)
         return bytes;
     }
 
-    public readonly int Available => _bytes.Length - _position;
-
     public void Advance(int n)
     {
         Debug.Assert(n >= 0, "n must be zero or greater");
@@ -75,7 +76,7 @@ public sbyte GetSByte()
     public ushort GetUInt16()
     {
         var bytes = _bytes.Slice(_position, 2);
-        _position += 2;
+        Advance(2);
 
         return _isBigEndian
             ? BinaryPrimitives.ReadUInt16BigEndian(bytes)
@@ -85,7 +86,7 @@ public ushort GetUInt16()
     public short GetInt16()
     {
         var bytes = _bytes.Slice(_position, 2);
-        _position += 2;
+        Advance(2);
 
         return _isBigEndian
             ? BinaryPrimitives.ReadInt16BigEndian(bytes)
@@ -95,7 +96,7 @@ public short GetInt16()
     public uint GetUInt32()
     {
         var bytes = _bytes.Slice(_position, 4);
-        _position += 4;
+        Advance(4);
 
         return _isBigEndian
             ? BinaryPrimitives.ReadUInt32BigEndian(bytes)
@@ -105,7 +106,7 @@ public uint GetUInt32()
     public int GetInt32()
     {
         var bytes = _bytes.Slice(_position, 4);
-        _position += 4;
+        Advance(4);
 
         return _isBigEndian
             ? BinaryPrimitives.ReadInt32BigEndian(bytes)
@@ -115,7 +116,7 @@ public int GetInt32()
     public long GetInt64()
     {
         var bytes = _bytes.Slice(_position, 8);
-        _position += 8;
+        Advance(8);
 
         return _isBigEndian
             ? BinaryPrimitives.ReadInt64BigEndian(bytes)
@@ -125,7 +126,7 @@ public long GetInt64()
     public ulong GetUInt64()
     {
         var bytes = _bytes.Slice(_position, 8);
-        _position += 8;
+        Advance(8);
 
         return _isBigEndian
             ? BinaryPrimitives.ReadUInt64BigEndian(bytes)

From f4437f578ca91a8c1b167f1e42966e33b9149b4f Mon Sep 17 00:00:00 2001
From: Jason Nelson <jason@carbonmade.com>
Date: Fri, 2 Feb 2024 11:04:34 -0800
Subject: [PATCH 24/30] Improve code readability in BplistReader

---
 MetadataExtractor/Formats/Apple/BplistReader.cs | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/MetadataExtractor/Formats/Apple/BplistReader.cs b/MetadataExtractor/Formats/Apple/BplistReader.cs
index e591bf2d6..0e76130b5 100644
--- a/MetadataExtractor/Formats/Apple/BplistReader.cs
+++ b/MetadataExtractor/Formats/Apple/BplistReader.cs
@@ -43,19 +43,20 @@ public static PropertyListResults Parse(byte[] bplist)
 
         Trailer trailer = ReadTrailer();
 
-        var reader = new BufferReader(bplist.AsSpan(checked((int)(trailer.OffsetTableOffset + trailer.TopObject))), isBigEndian: true);
+        int offset = checked((int)(trailer.OffsetTableOffset + trailer.TopObject));
+        var reader = new BufferReader(bplist.AsSpan(offset), isBigEndian: true);
 
         int[] offsets = new int[(int)trailer.NumObjects];
 
-        for (long i = 0; i < trailer.NumObjects; i++)
+        for (int i = 0; i < (int)trailer.NumObjects; i++)
         {
             if (trailer.OffsetIntSize == 1)
             {
-                offsets[(int)i] = reader.GetByte();
+                offsets[i] = reader.GetByte();
             }
             else if (trailer.OffsetIntSize == 2)
             {
-                offsets[(int)i] = reader.GetUInt16();
+                offsets[i] = reader.GetUInt16();
             }
         }
 

From 59f4294f9f1aefd34c79280074283de6a8fab1f6 Mon Sep 17 00:00:00 2001
From: Jason Nelson <jason@carbonmade.com>
Date: Fri, 2 Feb 2024 12:17:48 -0800
Subject: [PATCH 25/30] Fix length check in PngMetadataReader

---
 .../Formats/Png/PngMetadataReader.cs          | 20 ++++++++++---------
 1 file changed, 11 insertions(+), 9 deletions(-)

diff --git a/MetadataExtractor/Formats/Png/PngMetadataReader.cs b/MetadataExtractor/Formats/Png/PngMetadataReader.cs
index d2bcfdee2..85f31beb4 100644
--- a/MetadataExtractor/Formats/Png/PngMetadataReader.cs
+++ b/MetadataExtractor/Formats/Png/PngMetadataReader.cs
@@ -332,17 +332,19 @@ private static IEnumerable<Directory> ProcessChunk(PngChunk chunk)
                 {
                     directory.AddError("Insufficient bytes for PNG pHYs chunk.");
                 }
+                else
+                {
+                    var reader = new BufferReader(bytes, isBigEndian: true);
 
-                var reader = new BufferReader(bytes, isBigEndian: true);
-
-                var pixelsPerUnitX = reader.GetInt32();
-                var pixelsPerUnitY = reader.GetInt32();
-                var unitSpecifier = reader.GetSByte();
+                    var pixelsPerUnitX = reader.GetInt32();
+                    var pixelsPerUnitY = reader.GetInt32();
+                    var unitSpecifier = reader.GetSByte();
 
-                directory.Set(PngDirectory.TagPixelsPerUnitX, pixelsPerUnitX);
-                directory.Set(PngDirectory.TagPixelsPerUnitY, pixelsPerUnitY);
-                directory.Set(PngDirectory.TagUnitSpecifier, unitSpecifier);
-                yield return directory;
+                    directory.Set(PngDirectory.TagPixelsPerUnitX, pixelsPerUnitX);
+                    directory.Set(PngDirectory.TagPixelsPerUnitY, pixelsPerUnitY);
+                    directory.Set(PngDirectory.TagUnitSpecifier, unitSpecifier);
+                    yield return directory;
+                }
             }
             else if (chunkType.Equals(PngChunkType.sBIT))
             {

From 509973c1b42b43cc643fbe76cef7b5d24ab288a7 Mon Sep 17 00:00:00 2001
From: Drew Noakes <git@drewnoakes.com>
Date: Sun, 4 Feb 2024 22:21:52 +1100
Subject: [PATCH 26/30] Fix typo

---
 .../Exif/makernotes/OlympusCameraSettingsMakernoteDescriptor.cs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/MetadataExtractor/Formats/Exif/makernotes/OlympusCameraSettingsMakernoteDescriptor.cs b/MetadataExtractor/Formats/Exif/makernotes/OlympusCameraSettingsMakernoteDescriptor.cs
index 5aef68328..a4e7ef5cd 100644
--- a/MetadataExtractor/Formats/Exif/makernotes/OlympusCameraSettingsMakernoteDescriptor.cs
+++ b/MetadataExtractor/Formats/Exif/makernotes/OlympusCameraSettingsMakernoteDescriptor.cs
@@ -621,7 +621,7 @@ public sealed class OlympusCameraSettingsMakernoteDescriptor(OlympusCameraSettin
             if (Directory.GetObject(OlympusCameraSettingsMakernoteDirectory.TagGradation) is not short[] values || values.Length < 3)
                 return null;
 
-            var ret = (values[0], values[1], values[3]) switch
+            var ret = (values[0], values[1], values[2]) switch
             {
                 (0, 0, 0) => "n/a",
                 (-1, -1, 1) => "Low Key",

From a332d84ee5b0a408d8b3d682f78f25f175039922 Mon Sep 17 00:00:00 2001
From: Drew Noakes <git@drewnoakes.com>
Date: Sun, 4 Feb 2024 22:22:41 +1100
Subject: [PATCH 27/30] Revert change in 4CC strings

Encoding.ASCII converts non-printable characters to '?', yet 4CC may contain non-printable.
---
 .../QuickTime/QuickTimeReaderExtensions.cs    | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/MetadataExtractor/Formats/QuickTime/QuickTimeReaderExtensions.cs b/MetadataExtractor/Formats/QuickTime/QuickTimeReaderExtensions.cs
index 4bba9909e..49957c964 100644
--- a/MetadataExtractor/Formats/QuickTime/QuickTimeReaderExtensions.cs
+++ b/MetadataExtractor/Formats/QuickTime/QuickTimeReaderExtensions.cs
@@ -7,13 +7,30 @@ namespace MetadataExtractor.Formats.QuickTime
     /// </summary>
     public static class QuickTimeReaderExtensions
     {
+#if NETSTANDARD2_1
         public static string Get4ccString(this SequentialReader reader)
+#else
+        public unsafe static string Get4ccString(this SequentialReader reader)
+#endif
         {
             Span<byte> bytes = stackalloc byte[4];
+            Span<char> chars = stackalloc char[4];
 
             reader.GetBytes(bytes);
 
-            return Encoding.ASCII.GetString(bytes);
+            chars[0] = (char)bytes[0];
+            chars[1] = (char)bytes[1];
+            chars[2] = (char)bytes[2];
+            chars[3] = (char)bytes[3];
+
+#if NETSTANDARD2_1
+            return new string(chars);
+#else
+            fixed (char* c = chars)
+            {
+                return new string(c, 0, 4);
+            }
+#endif
         }
 
         public static decimal Get16BitFixedPoint(this SequentialReader reader)

From 7173e0aa97b8bf1766fcc91c2e3ae19f4556f3b8 Mon Sep 17 00:00:00 2001
From: Drew Noakes <git@drewnoakes.com>
Date: Sun, 4 Feb 2024 22:23:09 +1100
Subject: [PATCH 28/30] Make field readonly

---
 MetadataExtractor/IO/BufferReader.cs | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/MetadataExtractor/IO/BufferReader.cs b/MetadataExtractor/IO/BufferReader.cs
index 4b365745d..3900869b3 100644
--- a/MetadataExtractor/IO/BufferReader.cs
+++ b/MetadataExtractor/IO/BufferReader.cs
@@ -7,8 +7,9 @@ namespace MetadataExtractor.IO;
 internal ref struct BufferReader(ReadOnlySpan<byte> bytes, bool isBigEndian)
 {
     private readonly ReadOnlySpan<byte> _bytes = bytes;
+    private readonly bool _isBigEndian = isBigEndian;
+
     private int _position = 0;
-    private bool _isBigEndian = isBigEndian;
 
     public readonly int Available => _bytes.Length - _position;
 

From b983a8f878eb2d8b6f2fae3bac46056e94a4344c Mon Sep 17 00:00:00 2001
From: Drew Noakes <git@drewnoakes.com>
Date: Sun, 4 Feb 2024 22:23:21 +1100
Subject: [PATCH 29/30] Make property readonly

---
 MetadataExtractor/IO/BufferReader.cs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/MetadataExtractor/IO/BufferReader.cs b/MetadataExtractor/IO/BufferReader.cs
index 3900869b3..a580eb751 100644
--- a/MetadataExtractor/IO/BufferReader.cs
+++ b/MetadataExtractor/IO/BufferReader.cs
@@ -13,7 +13,7 @@ internal ref struct BufferReader(ReadOnlySpan<byte> bytes, bool isBigEndian)
 
     public readonly int Available => _bytes.Length - _position;
 
-    public int Position => _position;
+    public readonly int Position => _position;
 
     public byte GetByte()
     {

From 6c398fdc2662cfed9aef42294800a087aad3f401 Mon Sep 17 00:00:00 2001
From: Drew Noakes <git@drewnoakes.com>
Date: Sun, 4 Feb 2024 22:23:56 +1100
Subject: [PATCH 30/30] Change Advance to return a span

Use `Skip` to skip data and completely ignore it.
---
 .../Formats/Apple/BplistReader.cs             |  2 +-
 MetadataExtractor/IO/BufferReader.cs          | 56 ++++++++-----------
 2 files changed, 23 insertions(+), 35 deletions(-)

diff --git a/MetadataExtractor/Formats/Apple/BplistReader.cs b/MetadataExtractor/Formats/Apple/BplistReader.cs
index 0e76130b5..0a09d8f98 100644
--- a/MetadataExtractor/Formats/Apple/BplistReader.cs
+++ b/MetadataExtractor/Formats/Apple/BplistReader.cs
@@ -95,7 +95,7 @@ Trailer ReadTrailer()
             var reader = new BufferReader(bplist.AsSpan(bplist.Length - Trailer.SizeBytes), isBigEndian: true);
 
             // Skip 5-byte unused values, 1-byte sort version.
-            reader.Advance(6);
+            reader.Skip(5 + 1);
 
             return new Trailer
             {
diff --git a/MetadataExtractor/IO/BufferReader.cs b/MetadataExtractor/IO/BufferReader.cs
index a580eb751..0c237b67f 100644
--- a/MetadataExtractor/IO/BufferReader.cs
+++ b/MetadataExtractor/IO/BufferReader.cs
@@ -25,48 +25,41 @@ public byte GetByte()
 
     public void GetBytes(scoped Span<byte> bytes)
     {
-        if (_position + bytes.Length > _bytes.Length)
-            throw new IOException("End of data reached.");
-
-        _bytes.Slice(_position, bytes.Length).CopyTo(bytes);
-        _position += bytes.Length;
+        var buffer = Advance(bytes.Length);
+        buffer.CopyTo(bytes);
     }
 
     public byte[] GetBytes(int count)
     {
-        if (_position + count > _bytes.Length)
-            throw new IOException("End of data reached.");
-
+        var buffer = Advance(count);
         var bytes = new byte[count];
 
-        _bytes.Slice(_position, count).CopyTo(bytes);
-        _position += count;
+        buffer.CopyTo(bytes);
         return bytes;
     }
 
-    public void Advance(int n)
+    private ReadOnlySpan<byte> Advance(int count)
     {
-        Debug.Assert(n >= 0, "n must be zero or greater");
+        Debug.Assert(count >= 0, "count must be zero or greater");
 
-        if (_position + n > _bytes.Length)
+        if (_position + count > _bytes.Length)
             throw new IOException("End of data reached.");
 
-        _position += n;
+        var span = _bytes.Slice(_position, count);
+
+        _position += count;
+
+        return span;
     }
 
-    public bool TryAdvance(int n)
+    public void Skip(int count)
     {
-        Debug.Assert(n >= 0, "n must be zero or greater");
+        Debug.Assert(count >= 0, "count must be zero or greater");
 
-        _position += n;
-
-        if (_position > _bytes.Length)
-        {
-            _position = _bytes.Length;
-            return false;
-        }
+        if (_position + count > _bytes.Length)
+            throw new IOException("End of data reached.");
 
-        return true;
+        _position += count;
     }
 
     public sbyte GetSByte()
@@ -76,8 +69,7 @@ public sbyte GetSByte()
 
     public ushort GetUInt16()
     {
-        var bytes = _bytes.Slice(_position, 2);
-        Advance(2);
+        var bytes = Advance(2);
 
         return _isBigEndian
             ? BinaryPrimitives.ReadUInt16BigEndian(bytes)
@@ -86,8 +78,7 @@ public ushort GetUInt16()
 
     public short GetInt16()
     {
-        var bytes = _bytes.Slice(_position, 2);
-        Advance(2);
+        var bytes = Advance(2);
 
         return _isBigEndian
             ? BinaryPrimitives.ReadInt16BigEndian(bytes)
@@ -96,8 +87,7 @@ public short GetInt16()
 
     public uint GetUInt32()
     {
-        var bytes = _bytes.Slice(_position, 4);
-        Advance(4);
+        var bytes = Advance(4);
 
         return _isBigEndian
             ? BinaryPrimitives.ReadUInt32BigEndian(bytes)
@@ -106,8 +96,7 @@ public uint GetUInt32()
 
     public int GetInt32()
     {
-        var bytes = _bytes.Slice(_position, 4);
-        Advance(4);
+        var bytes = Advance(4);
 
         return _isBigEndian
             ? BinaryPrimitives.ReadInt32BigEndian(bytes)
@@ -116,8 +105,7 @@ public int GetInt32()
 
     public long GetInt64()
     {
-        var bytes = _bytes.Slice(_position, 8);
-        Advance(8);
+        var bytes = Advance(8);
 
         return _isBigEndian
             ? BinaryPrimitives.ReadInt64BigEndian(bytes)