From 5a0f7888f368330fa80e5cd648a576c0a4eb04f7 Mon Sep 17 00:00:00 2001
From: Stefan Boberg <stefan@boberg.org>
Date: Fri, 30 Jun 2023 10:36:27 +0200
Subject: * added file sharing control to BasicFile (required to implement
 lockfiles) * added delete-on-close support to BasicFile * added
 BasicFile::ReadRange()

---
 src/zenutil/basicfile.cpp               | 55 +++++++++++++++++++++++++--------
 src/zenutil/include/zenutil/basicfile.h | 24 ++++++++++----
 2 files changed, 60 insertions(+), 19 deletions(-)

diff --git a/src/zenutil/basicfile.cpp b/src/zenutil/basicfile.cpp
index 22acc346f..f91a54222 100644
--- a/src/zenutil/basicfile.cpp
+++ b/src/zenutil/basicfile.cpp
@@ -36,15 +36,17 @@ BasicFile::Open(const std::filesystem::path& FileName, Mode Mode)
 
 	if (Ec)
 	{
-		throw std::system_error(Ec, fmt::format("failed to open file '{}'", FileName));
+		throw std::system_error(Ec, fmt::format("failed to open file '{}', mode: {:x}", FileName, uint32_t(Mode)));
 	}
 }
 
 void
-BasicFile::Open(const std::filesystem::path& FileName, Mode Mode, std::error_code& Ec)
+BasicFile::Open(const std::filesystem::path& FileName, Mode InMode, std::error_code& Ec)
 {
 	Ec.clear();
 
+	Mode Mode = InMode & Mode::kModeMask;
+
 #if ZEN_PLATFORM_WINDOWS
 	DWORD dwCreationDisposition = 0;
 	DWORD dwDesiredAccess		= 0;
@@ -72,17 +74,18 @@ BasicFile::Open(const std::filesystem::path& FileName, Mode Mode, std::error_cod
 			break;
 	}
 
-	const DWORD dwShareMode			 = FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE;
-	const DWORD dwFlagsAndAttributes = FILE_ATTRIBUTE_NORMAL;
-	HANDLE		hTemplateFile		 = nullptr;
-
-	HANDLE FileHandle = CreateFile(FileName.c_str(),
-								   dwDesiredAccess,
-								   dwShareMode,
-								   /* lpSecurityAttributes */ nullptr,
-								   dwCreationDisposition,
-								   dwFlagsAndAttributes,
-								   hTemplateFile);
+	const DWORD dwShareMode = FILE_SHARE_READ | (EnumHasAllFlags(InMode, Mode::kPreventWrite) ? 0 : FILE_SHARE_WRITE) |
+							  (EnumHasAllFlags(InMode, Mode::kPreventDelete) ? 0 : FILE_SHARE_DELETE);
+	const DWORD dwFlagsAndAttributes =
+		FILE_ATTRIBUTE_NORMAL | (EnumHasAllFlags(InMode, Mode::kDeleteOnClose) ? FILE_FLAG_DELETE_ON_CLOSE : 0);
+	const HANDLE hTemplateFile = nullptr;
+	const HANDLE FileHandle	   = CreateFile(FileName.c_str(),
+											dwDesiredAccess,
+											dwShareMode,
+											/* lpSecurityAttributes */ nullptr,
+											dwCreationDisposition,
+											dwFlagsAndAttributes,
+											hTemplateFile);
 
 	if (FileHandle == INVALID_HANDLE_VALUE)
 	{
@@ -139,6 +142,12 @@ BasicFile::Close()
 	}
 }
 
+IoBuffer
+BasicFile::ReadRange(uint64_t FileOffset, uint64_t ByteCount)
+{
+	return IoBufferBuilder::MakeFromFileHandle(m_FileHandle, FileOffset, ByteCount);
+}
+
 void
 BasicFile::Read(void* Data, uint64_t BytesToRead, uint64_t FileOffset)
 {
@@ -220,6 +229,26 @@ BasicFile::StreamByteRange(uint64_t FileOffset, uint64_t Size, std::function<voi
 	}
 }
 
+uint64_t
+BasicFile::Write(CompositeBuffer Data, uint64_t FileOffset, std::error_code& Ec)
+{
+	uint64_t WrittenBytes = 0;
+	for (const SharedBuffer& Buffer : Data.GetSegments())
+	{
+		MemoryView BlockView = Buffer.GetView();
+		Write(BlockView, FileOffset, Ec);
+
+		if (Ec)
+		{
+			return WrittenBytes;
+		}
+
+		WrittenBytes += BlockView.GetSize();
+	}
+
+	return WrittenBytes;
+}
+
 void
 BasicFile::Write(MemoryView Data, uint64_t FileOffset, std::error_code& Ec)
 {
diff --git a/src/zenutil/include/zenutil/basicfile.h b/src/zenutil/include/zenutil/basicfile.h
index 877df0f92..1c5a31c5c 100644
--- a/src/zenutil/include/zenutil/basicfile.h
+++ b/src/zenutil/include/zenutil/basicfile.h
@@ -2,6 +2,10 @@
 
 #pragma once
 
+#include <zencore/zencore.h>
+
+#include <zencore/compositebuffer.h>
+#include <zencore/enumflags.h>
 #include <zencore/iobuffer.h>
 
 #include <filesystem>
@@ -36,25 +40,31 @@ public:
 		kTruncate = 2,	// Opens (or creates) a file for read and write and sets the size to zero
 		kDelete	  = 3,	// Opens (or creates) a file for read and write allowing .DeleteFile file disposition to be set
 		kTruncateDelete =
-			4  // Opens (or creates) a file for read and write and sets the size to zero allowing .DeleteFile file disposition to be set
+			4,	// Opens (or creates) a file for read and write and sets the size to zero allowing .DeleteFile file disposition to be set
+		kModeMask	   = 0x0007,
+		kPreventDelete = 0x1000'0000,  // Do not open with delete sharing mode (prevent other processes from deleting file while open)
+		kPreventWrite  = 0x2000'0000,  // Do not open with write sharing mode (prevent other processes from writing to file while open)
+		kDeleteOnClose = 0x4000'0000,  // File should be deleted when the last handle is closed
 	};
 
 	void	 Open(const std::filesystem::path& FileName, Mode Mode);
 	void	 Open(const std::filesystem::path& FileName, Mode Mode, std::error_code& Ec);
 	void	 Close();
 	void	 Read(void* Data, uint64_t Size, uint64_t FileOffset);
+	IoBuffer ReadRange(uint64_t FileOffset, uint64_t ByteCount);
 	void	 StreamFile(std::function<void(const void* Data, uint64_t Size)>&& ChunkFun);
 	void	 StreamByteRange(uint64_t FileOffset, uint64_t Size, std::function<void(const void* Data, uint64_t Size)>&& ChunkFun);
 	void	 Write(MemoryView Data, uint64_t FileOffset);
 	void	 Write(MemoryView Data, uint64_t FileOffset, std::error_code& Ec);
+	uint64_t Write(CompositeBuffer Data, uint64_t FileOffset, std::error_code& Ec);
 	void	 Write(const void* Data, uint64_t Size, uint64_t FileOffset);
 	void	 Write(const void* Data, uint64_t Size, uint64_t FileOffset, std::error_code& Ec);
 	void	 Flush();
-	uint64_t FileSize();
-	void	 SetFileSize(uint64_t FileSize);
-	IoBuffer ReadAll();
-	void	 WriteAll(IoBuffer Data, std::error_code& Ec);
-	void*	 Detach();
+	[[nodiscard]] uint64_t FileSize();
+	void				   SetFileSize(uint64_t FileSize);
+	IoBuffer			   ReadAll();
+	void				   WriteAll(IoBuffer Data, std::error_code& Ec);
+	void*				   Detach();
 
 	inline void* Handle() { return m_FileHandle; }
 
@@ -63,6 +73,8 @@ protected:
 private:
 };
 
+ENUM_CLASS_FLAGS(BasicFile::Mode);
+
 /**
  * Simple abstraction for a temporary file
  *
-- 
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