#include <errno.h>
#include <fcntl.h>
#include <mlvalues.h>
#include <fail.h>
#include "unixsupport.h"
#include <stdio.h>

#ifndef INVALID_SET_FILE_POINTER
#define INVALID_SET_FILE_POINTER (-1)
#endif

/* Sets handle h to a position based on gohere */
/* output, if set, is changed to the new location */
static void set_file_pointer(HANDLE h, LARGE_INTEGER gohere, PLARGE_INTEGER output, DWORD method)
{
	LONG high = gohere.HighPart;
	DWORD ret = SetFilePointer(h, gohere.LowPart, &high, method);
	if(ret == INVALID_SET_FILE_POINTER)
	{
		DWORD err = GetLastError();
		if(err != NO_ERROR)
		{
			win32_maperr(err);
			uerror("lockf", Nothing);
		}
	}
	if(output != NULL) {
		output->LowPart = ret;
		output->HighPart = high;
	}
}

CAMLprim void unix_lockf(value fd, value cmd, value span)
{
	CAMLparam3(fd, cmd, span);
	int lock_ret;
	OVERLAPPED overlap;
	long l_len;
	HANDLE h;
	OSVERSIONINFO version;
	LARGE_INTEGER cur_position;
	LARGE_INTEGER beg_position;
	LARGE_INTEGER zero;
	LARGE_INTEGER lock_len;

	version.dwOSVersionInfoSize = sizeof(OSVERSIONINFO);
	if(GetVersionEx(&version) == 0)
	{
		invalid_argument("lockf only supported on WIN32_NT platforms: could not determine current platform.");
	}
	if(version.dwPlatformId != VER_PLATFORM_WIN32_NT)
	{
		invalid_argument("lockf only supported on WIN32_NT platforms");
	}

	h = Handle_val(fd);

	l_len = Long_val(span);

	cur_position.HighPart = 0;
	cur_position.LowPart  = 0;
	beg_position.HighPart = 0;
	beg_position.LowPart  = 0;
	zero.HighPart = 0;
	zero.LowPart  = 0;
	lock_len.HighPart = 0;
	lock_len.LowPart  = 0;

	/* No matter what, we need the current position in the file */
	set_file_pointer(h, zero, &cur_position, FILE_CURRENT);

	if(l_len == 0)
	{
		/* Lock from cur to infinity */
		lock_len.HighPart = 4294967295;
		lock_len.LowPart  = 4294967295;

		overlap.OffsetHigh = cur_position.HighPart;
		overlap.Offset     = cur_position.LowPart ;
		overlap.hEvent     = 0;
	}
	else if(l_len > 0)
	{
		/* positive file offset */
		lock_len.HighPart = 0;
		lock_len.LowPart  = l_len;
		overlap.OffsetHigh = cur_position.HighPart;
		overlap.Offset     = cur_position.LowPart ;
	}
	else
	{
		/* Negative file offset */
		lock_len.LowPart = -l_len;
		if(l_len > cur_position.LowPart && cur_position.HighPart == 0) {
			errno = EINVAL;
			uerror("lockf", Nothing);
		}
		beg_position.QuadPart = cur_position.QuadPart - lock_len.QuadPart;

		overlap.OffsetHigh = beg_position.HighPart;
		overlap.Offset     = beg_position.LowPart ;
	}

	switch(Int_val(cmd))
	{
		case 0: /* F_ULOCK - unlock */
			lock_ret = UnlockFileEx(h, 0, lock_len.LowPart, lock_len.HighPart, &overlap);
			if(lock_ret == 0)
				errno = EACCES;
			break;
		case 1: /* F_LOCK - blocking write lock */
			enter_blocking_section();
			lock_ret = LockFileEx(h, LOCKFILE_EXCLUSIVE_LOCK, 0, lock_len.LowPart, lock_len.HighPart, &overlap);
			leave_blocking_section();
			if(lock_ret == 0)
				errno = EACCES;
			break;
		case 2: /* F_TLOCK - non-blocking write lock */
			lock_ret = LockFileEx(h, LOCKFILE_FAIL_IMMEDIATELY | LOCKFILE_EXCLUSIVE_LOCK, 0, lock_len.LowPart, lock_len.HighPart, &overlap);
			if(lock_ret == 0)
				errno = EACCES;
			break;
		case 3: /* F_TEST - check whether a write lock can be obtained */
			lock_ret = LockFileEx(h, LOCKFILE_FAIL_IMMEDIATELY | LOCKFILE_EXCLUSIVE_LOCK, 0, lock_len.LowPart, lock_len.HighPart, &overlap);
			if(lock_ret == 0)
				errno = EACCES;
			else
				UnlockFileEx(h, 0, lock_len.LowPart, lock_len.HighPart, &overlap);
			break;
		case 4: /* F_RLOCK - blocking read lock */
			enter_blocking_section();
			lock_ret = LockFileEx(h, 0, 0, lock_len.LowPart, lock_len.HighPart, &overlap);
			leave_blocking_section();
			if(lock_ret == 0)
				errno = EACCES;
			break;
		case 5: /* F_TRLOCK - non-blocking read lock */
			lock_ret = LockFileEx(h, LOCKFILE_FAIL_IMMEDIATELY, 0, lock_len.LowPart, lock_len.HighPart, &overlap);
			if(lock_ret == 0)
				errno = EACCES;
			break;
		default:
			errno = EINVAL;
	}
	if(lock_ret == 0)
		uerror("lockf", Nothing);
	CAMLreturn0;
}