/* map and unmap files in various ways
 * 
 * Copyright: Nicos Dessipris
 * Wriiten on: 13/02/1990
 * Updated on:
 * 10/5/93 J.Cupitt
 *	- im_mapfilerw() added
 * 13/12/94 JC
 *	- ANSIfied
 * 5/7/99 JC
 *	- better error if unable to map rw
 * 31/3/02 JC
 *	- better mmap() fails error
 * 19/9/02 JC
 * 	- added im__mmap()/im__munmap() with windows versions
 * 5/1/04 Lev Serebryakov
 * 	- patched for freebsd compatibility
 * 5/2/04 JC
 *	- now records length as well as base, so we unmap the right amount of
 *	  memory even if files change behind our back
 * 1/1/10
 * 	- set NOCACHE if we can ... helps OS X performance a lot
 * 25/3/11
 * 	- move to vips_ namespace
 */

/*

    This file is part of VIPS.
    
    VIPS is free software; you can redistribute it and/or modify
    it under the terms of the GNU Lesser General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
    02110-1301  USA

 */

/*

    These files are distributed with VIPS - http://www.vips.ecs.soton.ac.uk

 */

/* 
#define DEBUG
 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif /*HAVE_CONFIG_H*/
#include <vips/intl.h>

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <assert.h>

#include <sys/types.h>
#ifdef HAVE_SYS_MMAN_H
#include <sys/mman.h>
#endif /*HAVE_SYS_MMAN_H*/
#ifdef HAVE_SYS_FILE_H
#include <sys/file.h>
#endif /*HAVE_SYS_FILE_H*/
#include <sys/stat.h>
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif /*HAVE_UNISTD_H*/
#ifdef OS_WIN32 
#ifndef S_ISREG
#define S_ISREG(m) (!!(m & _S_IFREG))
#endif
#endif /*OS_WIN32*/

#include <vips/vips.h>

#ifdef OS_WIN32
#include <windows.h>
#endif /*OS_WIN32*/

void *
vips__mmap( int fd, int writeable, size_t length, gint64 offset )
{
	void *baseaddr;

#ifdef DEBUG
	printf( "vips__mmap: length = 0x%zx, offset = 0x%lx\n", 
		length, offset );
#endif /*DEBUG*/

#ifdef OS_WIN32
{
	HANDLE hFile = (HANDLE) _get_osfhandle( fd );

	DWORD flProtect;
	DWORD dwDesiredAccess;

        HANDLE hMMFile;

	ULARGE_INTEGER quad;
	DWORD dwFileOffsetHigh;
	DWORD dwFileOffsetLow;

	if( writeable ) {
		flProtect = PAGE_READWRITE;
		dwDesiredAccess = FILE_MAP_WRITE;
	}
	else {
		flProtect = PAGE_READONLY;
		dwDesiredAccess = FILE_MAP_READ;
	}

	quad.QuadPart = offset;
	dwFileOffsetLow = quad.LowPart;
	dwFileOffsetHigh = quad.HighPart;

        if( !(hMMFile = CreateFileMapping( hFile,
		NULL, flProtect, 0, 0, NULL )) ) {
                vips_error_system( GetLastError(), "vips_mapfile", 
			"%s", _( "unable to CreateFileMapping" ) );
		printf( "CreateFileMapping failed: %s\n", vips_error_buffer() );
                return( NULL );
        }

        if( !(baseaddr = (char *)MapViewOfFile( hMMFile, dwDesiredAccess, 
		dwFileOffsetHigh, dwFileOffsetLow, length )) ) {
                vips_error_system( GetLastError(), "vips_mapfile",
			"%s", _( "unable to MapViewOfFile" ) );
		printf( "MapViewOfFile failed: %s\n", vips_error_buffer() );
		CloseHandle( hMMFile );
                return( NULL );
        }

	/* Can close mapping now ... view stays until UnmapViewOfFile().

		FIXME ... is this a performance problem?

	 */
	CloseHandle( hMMFile );
}
#else /*!OS_WIN32*/
{
	int prot;
	int flags;

	if( writeable ) 
		prot = PROT_WRITE;
	else 
		prot = PROT_READ;

	flags = MAP_SHARED;

	/* OS X caches mmapped files very aggressively if this flags is not
	 * set. Scanning a large file without this flag will cause every other
	 * process to get swapped out and kill performance.
	 */
#ifdef MAP_NOCACHE
	flags |= MAP_NOCACHE;
#endif /*MAP_NOCACHE*/

	/* Casting gint64 to off_t should be safe, even on *nixes without
	 * LARGEFILE.
	 */

	baseaddr = mmap( 0, length, prot, flags, fd, (off_t) offset );
	if( baseaddr == MAP_FAILED ) { 
		vips_error_system( errno, "vips_mapfile", 
			"%s", _( "unable to mmap" ) );
		vips_warn( "vips_mapfile", _( "map failed (%s), "
			"running very low on system resources, "
			"expect a crash soon" ), strerror( errno ) );
		return( NULL ); 
	}
}
#endif /*OS_WIN32*/

	return( baseaddr );
}

int
vips__munmap( const void *start, size_t length )
{
#ifdef OS_WIN32
	if( !UnmapViewOfFile( (void *) start ) ) {
		vips_error_system( GetLastError(), "vips_mapfile",
			"%s", _( "unable to UnmapViewOfFile" ) );
		return( -1 );
	}
#else /*!OS_WIN32*/
	if( munmap( (void *) start, length ) < 0 ) {
		vips_error_system( errno, "vips_mapfile", 
			"%s", _( "unable to munmap file" ) );
		return( -1 );
	}
#endif /*OS_WIN32*/

	return( 0 );
}

int
vips_mapfile( VipsImage *im )
{
	struct stat st;
	mode_t m;

	assert( !im->baseaddr );

	/* Check the size of the file; if it is less than 64 bytes, then flag
	 * an error, we won't be able to read the vips header without a segv.
	 */
	g_assert( im->file_length > 0 );
	if( im->file_length < 64 ) {
		vips_error( "vips_mapfile", 
			"%s", _( "file is less than 64 bytes" ) );
		return( -1 ); 
	}
	if( fstat( im->fd, &st ) == -1 ) {
		vips_error( "vips_mapfile", 
			"%s", _( "unable to get file status" ) );
		return( -1 );
	}
	m = (mode_t) st.st_mode;
	if( !S_ISREG( m ) ) {
		vips_error( "vips_mapfile", 
			"%s", _( "not a regular file" ) ); 
		return( -1 ); 
	}

	if( !(im->baseaddr = vips__mmap( im->fd, 0, im->file_length, 0 )) )
		return( -1 );

	im->length = im->file_length;

	return( 0 );
}

/* As above, but map read/write.
 */
int
vips_mapfilerw( VipsImage *im )
{
	struct stat st;
	mode_t m;

	assert( !im->baseaddr );

	/* Check the size of the file if it is less than 64 bytes return
	 * make also sure that it is a regular file
	 */
	g_assert( im->file_length > 0 );
	if( fstat( im->fd, &st ) == -1 ) {
		vips_error( "vips_mapfilerw", 
			"%s", _( "unable to get file status" ) );
		return( -1 );
	}
	m = (mode_t) st.st_mode;
	if( im->file_length < 64 || !S_ISREG( m ) ) {
		vips_error( "vips_mapfile", 
			"%s", _( "unable to read data" ) ); 
		return( -1 ); 
	}

	if( !(im->baseaddr = vips__mmap( im->fd, 1, im->file_length, 0 )) )
		return( -1 );

	im->length = im->file_length;

	return( 0 );
}

/* From im_rwcheck() ... image needs to be a completely mapped read-only file, 
 * we try to remap it read-write. 
 */
int
vips_remapfilerw( VipsImage *image )
{
	void *baseaddr;

#ifdef OS_WIN32
{
	HANDLE hFile = (HANDLE) _get_osfhandle( image->fd );
        HANDLE hMMFile;

        if( !(hMMFile = CreateFileMapping( hFile,
		NULL, PAGE_READWRITE, 0, 0, NULL )) ) {
                vips_error_system( GetLastError(), "vips_mapfile", 
			"%s", _( "unable to CreateFileMapping" ) );
                return( -1 );
        }

	if( !UnmapViewOfFile( image->baseaddr ) ) {
		vips_error_system( GetLastError(), "vips_mapfile", 
			"%s", _( "unable to UnmapViewOfFile" ) );
		return( -1 );
	}
        if( !(baseaddr = (char *)MapViewOfFileEx( hMMFile, FILE_MAP_WRITE, 
		0, 0, 0, image->baseaddr )) ) {
                vips_error_system( GetLastError(), "vips_mapfile",
			"%s", _( "unable to MapViewOfFile" ) );
		CloseHandle( hMMFile );
                return( -1 );
        }

	/* Can close mapping now ... view stays until UnmapViewOfFile().

		FIXME ... is this a performance problem?

	 */
	CloseHandle( hMMFile );
}
#else /*!OS_WIN32*/
{
	assert( image->dtype == VIPS_IMAGE_MMAPIN );

	baseaddr = mmap( image->baseaddr, image->length,
		PROT_READ | PROT_WRITE, MAP_SHARED | MAP_FIXED, 
		image->fd, 0 );
	if( baseaddr == (void *)-1 ) { 
		vips_error( "vips_mapfile", _( "unable to mmap: \"%s\" - %s" ),
			image->filename, strerror( errno ) );
		return( -1 ); 
	}
}
#endif /*OS_WIN32*/

	image->dtype = VIPS_IMAGE_MMAPINRW;

	if( baseaddr != image->baseaddr ) {
		vips_error( "vips_mapfile", _( "unable to mmap \"%s\" to same "
			"address" ), image->filename );
		image->baseaddr = baseaddr;
		return( -1 ); 
	}

	return( 0 );
}