//---------------------------------------------------------------------------
//
//	SCSI Target Emulator RaSCSI (*^..^*)
//	for Raspberry Pi
//
//	Copyright (C) 2022 akuker
//
//  This method of file access will use the mmap() capabilities to 'map' the
//  file into memory.
//
//  This doesn't actually copy the file into RAM, but instead maps the file
//  as virtual memory. Behind the scenes, the file is still being accessed.
//
//  The operating system will do some caching of the data to prevent direct
//  drive access for each read/write. So, instead of implementing our own
//  caching mechanism (like in disk_track_cache.h), we just rely on the
//  operating system.
//
//	[ MmapFilehandle ]
//
//---------------------------------------------------------------------------

#include "mmap_file_handle.h"
#include "shared/log.h"
#include <sys/mman.h>
#include <errno.h>
#include <unistd.h>

//===========================================================================
//
//	Direct file access that will map the file into virtual memory space
//
//===========================================================================
MmapFileHandle::MmapFileHandle(const string &path, int size, uint32_t blocks, off_t imgoff) : DiskImageHandle(path, size, blocks, imgoff)
{
	assert(blocks > 0);
	assert(imgoff >= 0);

	fd = open(path.c_str(), O_RDWR);
	if (fd < 0)
	{
		LOGWARN("Unable to open file %s. Errno:%d", path.c_str(), errno)
	}
	LOGINFO("%s opened %s", __PRETTY_FUNCTION__, path.c_str())
	struct stat sb;
	if (fstat(fd, &sb) < 0)
	{
		LOGWARN("Unable to run fstat. Errno:%d", errno)
	}
	printf("Size: %d\n", (unsigned int)sb.st_size);

	LOGINFO("%s mmap-ed file of size: %d", __PRETTY_FUNCTION__, (unsigned int)sb.st_size)

	memory_block = (const char *)mmap(NULL, sb.st_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
	int errno_val = errno;
	if (memory_block == MAP_FAILED)
	{
		LOGWARN("Unabled to memory map file %s", path.c_str());
		LOGWARN("   Errno:%d", errno_val);
		return;
	}
	initialized = true;
}

MmapFileHandle::~MmapFileHandle()
{
	munmap((void *)memory_block, sb.st_size);
	close(fd);

	// Force the OS to save any cached data to the disk
	sync();
}

bool MmapFileHandle::ReadSector(vector<uint8_t>& buf, int block)
{
	assert(sec_size != 0);
	assert(block < sec_blocks);
	assert(memory_block);

	int sector_size_bytes = (off_t)1 << sec_size;

	// Calculate offset into the image file
	off_t offset = GetTrackOffset(block);
	offset += GetSectorOffset(block);

	memcpy(buf.data(), &memory_block[offset], sector_size_bytes);

	return true;
}

bool MmapFileHandle::WriteSector(const vector<uint8_t>& buf, int block)
{
	assert(block < sec_blocks);
	assert(memory_block);

	assert((block * sec_size) <= (sb.st_size + sec_size));

	memcpy((void *)&memory_block[(block * sec_size)], buf.data(), sec_size);

	return true;
}