Implement initial Sai2 support

.clang-format

@@ -1,5 +1,5 @@
 ---
-Language: Cpp
+Language:        Cpp
 AccessModifierOffset: -4
 AlignAfterOpenBracket: BlockIndent
 AlignConsecutiveAssignments: true
@@ -21,19 +21,19 @@ BinPackArguments: true
 BinPackParameters: true
 BitFieldColonSpacing: Both
 BreakBeforeBraces: Custom
-BraceWrapping:
-  AfterCaseLabel: true
-  AfterClass: true
+BraceWrapping:   
+  AfterCaseLabel:  true
+  AfterClass:      true
   AfterControlStatement: true
-  AfterEnum: true
-  AfterFunction: true
-  AfterNamespace: true
+  AfterEnum:       true
+  AfterFunction:   true
+  AfterNamespace:  true
   AfterObjCDeclaration: true
-  AfterStruct: true
-  AfterUnion: true
-  BeforeCatch: true
-  BeforeElse: true
-  IndentBraces: false
+  AfterStruct:     true
+  AfterUnion:      true
+  BeforeCatch:     true
+  BeforeElse:      true
+  IndentBraces:    false
   SplitEmptyFunction: true
   SplitEmptyRecord: true
   SplitEmptyNamespace: true
@@ -42,22 +42,22 @@ BreakBeforeInheritanceComma: false
 BreakBeforeTernaryOperators: true
 BreakConstructorInitializers: BeforeColon
 BreakStringLiterals: true
-ColumnLimit: 100
+ColumnLimit:     80
 CompactNamespaces: false
 ConstructorInitializerAllOnOneLineOrOnePerLine: false
 ConstructorInitializerIndentWidth: 4
 ContinuationIndentWidth: 4
 Cpp11BracedListStyle: true
 DerivePointerAlignment: false
-DisableFormat: false
+DisableFormat:   false
 ExperimentalAutoDetectBinPacking: false
 FixNamespaceComments: true
 IndentCaseLabels: false
-IndentWidth: 4
+IndentWidth:     4
 IndentWrappedFunctionNames: true
 KeepEmptyLinesAtTheStartOfBlocks: true
-MacroBlockBegin: ""
-MacroBlockEnd: ""
+MacroBlockBegin: ''
+MacroBlockEnd:   ''
 MaxEmptyLinesToKeep: 1
 NamespaceIndentation: None
 PenaltyBreakAssignment: 4
@@ -68,21 +68,22 @@ PenaltyBreakString: 1000
 PenaltyExcessCharacter: 1000000
 PenaltyReturnTypeOnItsOwnLine: 60
 PointerAlignment: Left
-ReflowComments: true
-SortIncludes: true
+ReflowComments:  true
+SortIncludes:    true
 SortUsingDeclarations: true
 SpaceAfterCStyleCast: false
 SpaceAfterTemplateKeyword: false
 SpaceBeforeAssignmentOperators: true
 SpaceBeforeParens: Never
 SpaceInEmptyParentheses: false
 SpacesBeforeTrailingComments: 1
-SpacesInAngles: false
+SpacesInAngles:  false
 SpacesInContainerLiterals: true
 SpacesInCStyleCastParentheses: false
 SpacesInParentheses: false
 SpacesInConditionalStatement: true
 SpacesInSquareBrackets: false
-Standard: c++20
-TabWidth: 4
-UseTab: ForContinuationAndIndentation
+Standard:        c++20
+TabWidth:        4
+UseTab:          ForContinuationAndIndentation
+...

CMakeLists.txt

@@ -82,6 +82,7 @@ add_library(
 	source/ifstreambuf.cpp
 	source/keys.cpp
 	source/sai.cpp
+	source/sai2.cpp
 	source/virtualfileentry.cpp
 	source/virtualfilesystem.cpp
 	source/virtualpage.cpp
@@ -93,15 +94,28 @@ target_include_directories(
 )
 
 if( MASTER_PROJECT )
-	### Decryption sample
+	### Thumbnail-Sai1 sample
 	add_executable(
-		Thumbnail
-		samples/Thumbnail.cpp
+		Thumbnail-Sai1
+		samples/Thumbnail-Sai1.cpp
 		samples/stb_image_write.c
 	)
+	target_link_libraries(
+		Thumbnail-Sai1
+		PRIVATE
+		sai
+	)
 
+
+	### Thumbnail-Sai2 sample
+	add_executable(
+		Thumbnail-Sai2
+		samples/Thumbnail-Sai2.cpp
+		samples/stb_image_write.c
+		samples/stb_image.c
+	)
 	target_link_libraries(
-		Thumbnail
+		Thumbnail-Sai2
 		PRIVATE
 		sai
 	)

include/sai.hpp

@@ -3,7 +3,6 @@
 
 #pragma once
 #include <array>
-#include <bit>
 #include <cstddef>
 #include <cstdint>
 #include <ctime>
@@ -15,26 +14,10 @@
 #include <span>
 #include <tuple>
 
-namespace sai
-{
+#include "util.hpp"
 
-template<std::endian Endianness = std::endian::big, std::size_t N>
-inline constexpr std::uint32_t Tag(const char (&TagString)[N])
+namespace sai
 {
-	static_assert(N == 5, "Tag must be 4 characters");
-	if constexpr( Endianness == std::endian::big )
-	{
-		return (
-			(TagString[3] << 0) | (TagString[2] << 8) | (TagString[1] << 16) | (TagString[0] << 24)
-		);
-	}
-	else
-	{
-		return (
-			(TagString[3] << 24) | (TagString[2] << 16) | (TagString[1] << 8) | (TagString[0] << 0)
-		);
-	}
-}
 
 enum class LayerType
 {

include/sai2.hpp

@@ -0,0 +1,154 @@
+// SPDX-FileCopyrightText: Copyright (c) 2025 Wunkolo
+// SPDX-License-Identifier: MIT
+
+#pragma once
+
+#include <array>
+#include <cstdint>
+#include <functional>
+#include <span>
+
+#include "util.hpp"
+
+namespace sai2
+{
+using namespace sai;
+
+struct CanvasHeader
+{
+	// "SAI-CANVAS-TYPE0"
+	std::array<char, 16> Identifier;
+
+	std::uint8_t Flags0;
+
+	// & 0x7 seems to indicate if thumbnail has transparency
+	std::uint8_t CanvasBackgroundFlags;
+
+	std::uint8_t Flags2;
+	std::uint8_t Flags3;
+
+	std::uint32_t Width;
+	std::uint32_t Height;
+	std::uint32_t PrintingResolution;
+	std::uint32_t TableCount;
+	std::uint32_t SelectedLayer;
+	std::uint64_t UnknownA;
+	std::uint64_t UnknownB;
+	std::uint32_t CanvasBackgroundColor;
+
+	// "norm"/"vivd"/"deep"/"mult"/"ver1"
+	std::uint32_t LayerEffectColor;
+};
+static_assert(sizeof(CanvasHeader) == 64);
+
+enum class CanvasDataType : std::uint32_t
+{
+	// History data
+	History = TagLE("hist"),
+
+	// jpeg-encoded thumbnails
+	ThumbnailLossy = TagLE("thum"),
+	// delta-compressed thumbnails
+	ThumbnailLossless = TagLE("intg"),
+
+	// Layer descriptor
+	Layer = TagLE("layr"),
+	// Standalone mask not associated with a layer
+	// such as with the selection-pen(the "blue" mask)
+	Mask = TagLE("mask"),
+	// Layer data
+	LayerPixels   = TagLE("lpix"),
+	FPixels       = TagLE("fpix"), // Folder pixels?
+	MaskPixels    = TagLE("mpix"),
+	LayerLinework = TagLE("liwk"),
+	Shape         = TagLE("shap"),
+	// Rulers/guides
+	Perspective = TagLE("pers"),
+	Text        = TagLE("text"),
+	Grid        = TagLE("grid"),
+	Symmetry    = TagLE("symm"),
+};
+
+struct CanvasEntry
+{
+	CanvasDataType Type;
+	std::uint32_t  LayerID;
+	std::uint64_t  BlobsOffset; // Absolute file offset
+};
+static_assert(sizeof(CanvasEntry) == 16);
+
+// Canvases 512x512 or larger will use the jssf format, smaller canvases will
+// use the delta-compressed format
+enum class BlobDataType : std::uint32_t
+{
+	// Raw
+	Raw = TagLE("raw\0"),
+	// Delta-compressed pixel stream with an additional "RLE" compression
+	DeltaPixelsCompressed = TagLE("dpcm"),
+	// Older image format used for thumbnails, based on JPEG
+	Jssf = TagLE("jssf"),
+};
+
+struct BlobLayr
+{
+	std::uint32_t LayerID;
+	std::uint32_t Unknown;
+	std::uint32_t UnknownOne;
+	std::uint32_t BlendingMode;
+	std::uint32_t UnknownB;
+	std::uint32_t UnknownC;
+	std::uint32_t UnknownD;
+	std::uint32_t UnknownE;
+	std::uint32_t UnknownF;
+	std::uint32_t UnknownG;
+	std::uint32_t MaskBlendingMode;
+	std::uint32_t UnknownI;
+	std::uint32_t UnknownJ;
+};
+
+struct BlobHist
+{
+	char16_t      HistIdentifier[32];
+	char8_t       HistHash[16];
+	std::uint32_t Revision;
+};
+
+// Return false to break iteration
+using CanvasDataProcT = bool(
+	const sai2::CanvasHeader& Header, const sai2::CanvasEntry& TableEntry,
+	std::span<const std::byte> Bytes
+);
+
+bool IterateCanvasData(
+	const std::span<const std::byte>     FileData,
+	const std::function<CanvasDataProcT> CanvasDataProc
+);
+
+std::size_t UnpackDeltaRLE16(
+	std::span<const std::byte> Compressed, std::span<std::int16_t> Decompressed,
+	std::uint32_t PixelCount, std::uint8_t OutputChannels,
+	std::uint8_t InputChannels
+);
+
+// This looks kind of like the "Up" png-filter seen here:
+// http://www.libpng.org/pub/png/spec/1.2/PNG-Filters.html
+uint32_t DeltaUnpackRow16Bpc(
+	uint32_t* Dest8Bpc, const std::uint32_t* PreviousRow8Bpc,
+	const std::uint64_t* DeltaEncoded16Bpc, const std::uint32_t PixelCount
+);
+
+// Extracts a JSSF table entry into a standard jpeg stream
+// Returns (Jpeg Data, Width, Height).
+// Returns (null,0,0) if an error has occurred.
+std::tuple<std::vector<std::byte>, std::uint32_t, std::uint32_t>
+	ExtractJssfToJpeg(std::span<const std::byte> JssfTableData);
+
+// Extracts a DPCM table entry into BGRA pixels
+// Returns (BGRA Data, Width, Height).
+// Returns (null,0,0) if an error has occurred.
+std::tuple<std::vector<std::byte>, std::uint32_t, std::uint32_t>
+	ExtractDpcmToBGRA(
+		const CanvasHeader& Header, std::span<const std::byte> JssfTableData
+	);
+
+} // namespace sai2

include/util.hpp

@@ -0,0 +1,41 @@
+// SPDX-FileCopyrightText: Copyright (c) 2025 Wunkolo
+// SPDX-License-Identifier: MIT
+#pragma once
+
+#include <bit>
+#include <cstdint>
+
+namespace sai
+{
+
+template<std::endian Endianness = std::endian::big, std::size_t N>
+inline constexpr std::uint32_t Tag(const char (&TagString)[N])
+{
+	static_assert(N == 5, "Tag must be 4 characters");
+	if constexpr( Endianness == std::endian::big )
+	{
+		return (
+			(TagString[3] << 0) | (TagString[2] << 8) | (TagString[1] << 16)
+			| (TagString[0] << 24)
+		);
+	}
+	else
+	{
+		return (
+			(TagString[3] << 24) | (TagString[2] << 16) | (TagString[1] << 8)
+			| (TagString[0] << 0)
+		);
+	}
+}
+
+template<std::size_t N>
+inline constexpr std::uint32_t TagLE(const char (&TagString)[N])
+{
+	return Tag<std::endian::little, N>(TagString);
+}
+template<std::size_t N>
+inline constexpr std::uint32_t TagBE(const char (&TagString)[N])
+{
+	return Tag<std::endian::big, N>(TagString);
+}
+} // namespace sai