// Copyright (c) 2004 by Digital Mars
// All Rights Reserved
// written by Walter Bright and Matthew Wilson (Synesis Software Pty Ltd.)
// www.digitalmars.com
// www.synesis.com.au/software

/**
 * Read and write memory mapped files.
 * Macros:
 *	WIKI=Phobos/StdMmfile
 */

module std.mmfile;

private import std.file;
private import std.c.stdio;
private import std.c.stdlib;
private import std.path;
private import std.string;

//debug = MMFILE;

version (Win32)
{
	private import std.c.windows.windows;
	private import std.utf;
	
	private uint dwVersion;
	
	static this()
	{	// http://msdn.microsoft.com/library/default.asp?url=/library/en-us/sysinfo/base/getversion.asp
		dwVersion = GetVersion();
	}
}
else version (linux)
{
	private import std.c.linux.linux;
}
else
{
	static assert(0);
}

/**
 * MmFile objects control the memory mapped file resource.
 */
class MmFile
{
    /**
     * The mode the memory mapped file is opened with.
     */
    enum Mode
    {	Read,		/// read existing file
	ReadWriteNew,	/// delete existing file, write new file
	ReadWrite,	/// read/write existing file, create if not existing
	ReadCopyOnWrite, /// read/write existing file, copy on write
    }
    
    /**
     * Open memory mapped file filename for reading.
     * File is closed when the object instance is deleted.
     * Throws:
     *	std.file.FileException
     */
    this(char[] filename)
    {
		this(filename, Mode.Read, 0, null);
    }
    
    /**
     * Open memory mapped file filename in mode.
     * File is closed when the object instance is deleted.
     * Params:
     *	filename = name of the file.
     *		If null, an anonymous file mapping is created.
     *	mode = access mode defined above.
     *	size =  the size of the file. If 0, it is taken to be the
     *		size of the existing file.
     *	address = the preferred address to map the file to,
     *		although the system is not required to honor it.
     *		If null, the system selects the most convenient address.
     *	window = preferred block size of the amount of data to map at one time
     *		with 0 meaning map the entire file. The window size must be a
     *		multiple of the memory allocation page size. 
     * Throws:
     *	std.file.FileException
     */
    this(char[] filename, Mode mode, ulong size, void* address,
			size_t window = 0)
    {
		this.filename = filename;
		this.mMode = mode;
		this.window = window;
		this.address = address;
	
		version (Win32)
		{
			void* p;
			uint dwDesiredAccess2;
			uint dwShareMode;
			uint dwCreationDisposition;
			uint flProtect;
	    
			if (dwVersion & 0x80000000 && (dwVersion & 0xFF) == 3)
			{
			    throw new FileException(filename,
				"Win32s does not implement mm files");
			}
	    
			switch (mode)
			{
			    case Mode.Read:
				dwDesiredAccess2 = GENERIC_READ;
				dwShareMode = FILE_SHARE_READ;
				dwCreationDisposition = OPEN_EXISTING;
				flProtect = PAGE_READONLY;
				dwDesiredAccess = FILE_MAP_READ;
				break;

			    case Mode.ReadWriteNew:
				assert(size != 0);
				dwDesiredAccess2 = GENERIC_READ | GENERIC_WRITE;
				dwShareMode = FILE_SHARE_READ | FILE_SHARE_WRITE;
				dwCreationDisposition = CREATE_ALWAYS;
				flProtect = PAGE_READWRITE;
				dwDesiredAccess = FILE_MAP_WRITE;
				break;

			    case Mode.ReadWrite:
				dwDesiredAccess2 = GENERIC_READ | GENERIC_WRITE;
				dwShareMode = FILE_SHARE_READ | FILE_SHARE_WRITE;
				dwCreationDisposition = OPEN_ALWAYS;
				flProtect = PAGE_READWRITE;
				dwDesiredAccess = FILE_MAP_WRITE;
				break;

			    case Mode.ReadCopyOnWrite:
				if (dwVersion & 0x80000000)
				{
				    throw new FileException(filename,
					"Win9x does not implement copy on write");
				}
				dwDesiredAccess2 = GENERIC_READ | GENERIC_WRITE;
				dwShareMode = FILE_SHARE_READ | FILE_SHARE_WRITE;
				dwCreationDisposition = OPEN_EXISTING;
				flProtect = PAGE_WRITECOPY;
				dwDesiredAccess = FILE_MAP_COPY;
				break;

			    default:
				assert(0);
			}
		
			if (useWfuncs)
			{
				wchar* namez = std.utf.toUTF16z(filename);
				hFile = CreateFileW(namez,
						dwDesiredAccess2,
						dwShareMode,
						null,
						dwCreationDisposition,
						FILE_ATTRIBUTE_NORMAL,
						cast(HANDLE)null);
			}
			else
			{
				char* namez = std.file.toMBSz(filename);
				hFile = CreateFileA(namez,
						dwDesiredAccess2,
						dwShareMode,
						null,
						dwCreationDisposition,
						FILE_ATTRIBUTE_NORMAL,
						cast(HANDLE)null);
			}
			if (hFile == INVALID_HANDLE_VALUE)
				goto err1;
		
			int hi = cast(int)(size>>32);
			hFileMap = CreateFileMappingA(hFile, null, flProtect, hi, cast(uint)size, null);
			if (hFileMap == null)               // mapping failed
				goto err1;
		
			if (size == 0)
			{
				uint sizehi;
				uint sizelow = GetFileSize(hFile,&sizehi);
				size = (cast(ulong)sizehi << 32) + sizelow;
			}
			this.size = size;
		
			size_t initial_map = (window && 2*window<size)? 2*window : cast(size_t)size;
			p = MapViewOfFileEx(hFileMap, dwDesiredAccess, 0, 0, initial_map, address);
			if (!p) goto err1;
			data = p[0 .. initial_map];
		
			debug (MMFILE) printf("MmFile.this(): p = %p, size = %d\n", p, size);
			return;
		
			err1:
			if (hFileMap != null)
				CloseHandle(hFileMap);
			hFileMap = null;
		
			if (hFile != INVALID_HANDLE_VALUE)
				CloseHandle(hFile);
			hFile = INVALID_HANDLE_VALUE;
		
			errNo();
		}
		else version (linux)
		{
			char* namez = toStringz(filename);
			void* p;
			int oflag;
			int fmode;
	
			switch (mode)
			{
				case Mode.Read:
					flags = MAP_SHARED;
					prot = PROT_READ;
					oflag = O_RDONLY;
					fmode = 0;
					break;
	
				case Mode.ReadWriteNew:
					assert(size != 0);
					flags = MAP_SHARED;
					prot = PROT_READ | PROT_WRITE;
					oflag = O_CREAT | O_RDWR | O_TRUNC;
					fmode = 0660;
					break;
	
				case Mode.ReadWrite:
					flags = MAP_SHARED;
					prot = PROT_READ | PROT_WRITE;
					oflag = O_CREAT | O_RDWR;
					fmode = 0660;
					break;
	
				case Mode.ReadCopyOnWrite:
					flags = MAP_PRIVATE;
					prot = PROT_READ | PROT_WRITE;
					oflag = O_RDWR;
					fmode = 0;
					break;

				default:
					assert(0);
			}
	
			if (filename.length)
			{	
				struct_stat statbuf;
	
				fd = std.c.linux.linux.open(namez, oflag, fmode);
				if (fd == -1)
				{
					// printf("\topen error, errno = %d\n",getErrno());
					errNo();
				}
	
				if (std.c.linux.linux.fstat(fd, &statbuf))
				{
					//printf("\tfstat error, errno = %d\n",getErrno());
					std.c.linux.linux.close(fd);
					errNo();
				}
	
				if (prot & PROT_WRITE && size > statbuf.st_size)
				{
					// Need to make the file size bytes big
					std.c.linux.linux.lseek(fd, cast(int)(size - 1), SEEK_SET);
					char c = 0;
					std.c.linux.linux.write(fd, &c, 1);
				}
				else if (prot & PROT_READ && size == 0)
					size = statbuf.st_size;
			}
			else
			{
				fd = -1;
				flags |= MAP_ANONYMOUS;
			}
			this.size = size;
			size_t initial_map = (window && 2*window<size)? 2*window : cast(size_t)size;
			p = mmap(address, initial_map, prot, flags, fd, 0);
			if (p == MAP_FAILED) {
			  if (fd != -1)
			    std.c.linux.linux.close(fd);
			  errNo();
			}

			data = p[0 .. initial_map];
		}
		else
		{
			static assert(0);
		}
	}

	/**
	 * Flushes pending output and closes the memory mapped file.
	 */
	~this()
	{
		debug (MMFILE) printf("MmFile.~this()\n");
		unmap();
		version (Win32)
		{
			if (hFileMap != null && CloseHandle(hFileMap) != TRUE)
				errNo();
			hFileMap = null;

			if (hFile != INVALID_HANDLE_VALUE && CloseHandle(hFile) != TRUE)
				errNo();
			hFile = INVALID_HANDLE_VALUE;
		}
		else version (linux)
		{
			if (fd != -1 && std.c.linux.linux.close(fd) == -1)
				errNo();
			fd = -1;
		}
		else
		{
			static assert(0);
		}
		data = null;
	}

	/* Flush any pending output.
	*/
	void flush()
	{
		debug (MMFILE) printf("MmFile.flush()\n");
		version (Win32)
		{
			FlushViewOfFile(data.ptr, data.length);
		}
		else version (linux)
		{
			int i;

			i = msync(cast(void*)data, data.length, MS_SYNC);	// sys/mman.h
			if (i != 0)
				errNo();
		}
		else
		{
			static assert(0);
		}
	}

	/**
	 * Gives size in bytes of the memory mapped file.
	 */
	ulong length()
	{
		debug (MMFILE) printf("MmFile.length()\n");
		return size;
	}

	/**
	 * Read-only property returning the file mode.
	 */
	Mode mode()
	{
		debug (MMFILE) printf("MmFile.mode()\n");
		return mMode;
	}

	/**
	 * Returns entire file contents as an array.
	 */
	void[] opSlice()
	{
		debug (MMFILE) printf("MmFile.opSlice()\n");
		return opSlice(0,size);
	}

	/**
	 * Returns slice of file contents as an array.
	 */
	void[] opSlice(ulong i1, ulong i2)
	{
		debug (MMFILE) printf("MmFile.opSlice(%lld, %lld)\n", i1, i2);
		ensureMapped(i1,i2);
		size_t off1 = cast(size_t)(i1-start);
		size_t off2 = cast(size_t)(i2-start);
		return data[off1 .. off2];
	}

	/**
	 * Returns byte at index i in file.
	 */
	ubyte opIndex(ulong i)
	{
		debug (MMFILE) printf("MmFile.opIndex(%lld)\n", i);
		ensureMapped(i);
		size_t off = cast(size_t)(i-start);
		return (cast(ubyte[])data)[off];
	}

	/**
	 * Sets and returns byte at index i in file to value.
	 */
	ubyte opIndexAssign(ubyte value, ulong i)
	{
		debug (MMFILE) printf("MmFile.opIndex(%lld, %d)\n", i, value);
		ensureMapped(i);
		size_t off = cast(size_t)(i-start);
		return (cast(ubyte[])data)[off] = value;
	}


	// return true if the given position is currently mapped
	private int mapped(ulong i) 
	{
		debug (MMFILE) printf("MmFile.mapped(%lld, %lld, %d)\n", i,start, 
				data.length);
		return i >= start && i < start+data.length;
	}

	// unmap the current range
	private void unmap() 
	{
		debug (MMFILE) printf("MmFile.unmap()\n");
		version(Windows) {
			/* Note that under Windows 95, UnmapViewOfFile() seems to return
			* random values, not TRUE or FALSE.
			*/
			if (data && UnmapViewOfFile(data.ptr) == FALSE &&
				(dwVersion & 0x80000000) == 0)
				errNo();
		} else {
			if (data && munmap(cast(void*)data, data.length) != 0)
				errNo();
		}
		data = null;
	}

	// map range
	private void map(ulong start, size_t len) 
	{
		debug (MMFILE) printf("MmFile.map(%lld, %d)\n", start, len);
		void* p;
		if (start+len > size)
			len = cast(size_t)(size-start);
		version(Windows) {
			uint hi = cast(uint)(start>>32);
			p = MapViewOfFileEx(hFileMap, dwDesiredAccess, hi, cast(uint)start, len, address);
			if (!p) errNo();
		} else {
			p = mmap(address, len, prot, flags, fd, cast(int)start);
			if (p == MAP_FAILED) errNo();
		}
		data = p[0 .. len];
		this.start = start;
	}

	// ensure a given position is mapped
	private void ensureMapped(ulong i) 
	{
		debug (MMFILE) printf("MmFile.ensureMapped(%lld)\n", i);
		if (!mapped(i)) {
			unmap();
			if (window == 0) {
				map(0,cast(size_t)size);
			} else {
				ulong block = i/window;
				if (block == 0)
					map(0,2*window);
				else 
					map(window*(block-1),3*window);
			}
		}
	}

	// ensure a given range is mapped
	private void ensureMapped(ulong i, ulong j) 
	{
		debug (MMFILE) printf("MmFile.ensureMapped(%lld, %lld)\n", i, j);
		if (!mapped(i) || !mapped(j-1)) {
			unmap();
			if (window == 0) {
				map(0,cast(size_t)size);
			} else {
				ulong iblock = i/window;
				ulong jblock = (j-1)/window;
				if (iblock == 0) {
					map(0,cast(size_t)(window*(jblock+2)));
				} else {
					map(window*(iblock-1),cast(size_t)(window*(jblock-iblock+3)));
				}
			}
		}
	}

	private:
	char[] filename;
	void[] data;
	ulong  start;
	size_t window;
	ulong  size;
	Mode   mMode;
	void*  address;

	version (Win32)
	{
		HANDLE hFile = INVALID_HANDLE_VALUE;
		HANDLE hFileMap = null;
		uint dwDesiredAccess;
	}
	else version (linux)
	{
		int fd;
		int prot;
		int flags;
		int fmode;
	}
	else
	{
		static assert(0);
	}

	// Report error, where errno gives the error number
	void errNo()
	{
		version (Win32)
		{
			throw new FileException(filename, GetLastError());
		}
		else version (linux)
		{
			throw new FileException(filename, getErrno());
		}
		else
		{
			static assert(0);
		}
	}
}

unittest {
	const size_t K = 1024;
	size_t win = 64*K; // assume the page size is 64K
	version(Win32) {
		/+ these aren't defined in std.c.windows.windows so let's use the default
         SYSTEM_INFO sysinfo;
         GetSystemInfo(&sysinfo);
         win = sysinfo.dwAllocationGranularity;
		+/
	} else version (linux) {
		// getpagesize() is not defined in the unix D headers so use the guess
	}
	MmFile mf = new MmFile("testing.txt",MmFile.Mode.ReadWriteNew,100*K,null,win);
	ubyte[] str = cast(ubyte[])"1234567890";
	ubyte[] data = cast(ubyte[])mf[0 .. 10];
	data[] = str[];
	assert( mf[0 .. 10] == str );
	data = cast(ubyte[])mf[50 .. 60];
	data[] = str[];
	assert( mf[50 .. 60] == str );
	ubyte[] data2 = cast(ubyte[])mf[20*K .. 60*K];
	assert( data2.length == 40*K );
	assert( data2[length-1] == 0 );
	mf[100*K-1] = cast(ubyte)'b';
	data2 = cast(ubyte[])mf[21*K .. 100*K];
	assert( data2.length == 79*K );
	assert( data2[length-1] == 'b' );
	delete mf;
	std.file.remove("testing.txt");
}
