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/* $Id$ */

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/** @file fileio.cpp Standard In/Out file operations */

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#include "stdafx.h"

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#include "openttd.h"

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#include "fileio.h"

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#include "functions.h"

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#include "string.h"

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#include "macros.h"

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#include "variables.h"

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#include "debug.h"

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/*************************************************/

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/* FILE IO ROUTINES ******************************/

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/*************************************************/

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#define FIO_BUFFER_SIZE 512

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#define MAX_HANDLES 64

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struct Fio {

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	byte *buffer, *buffer_end;          ///< position pointer in local buffer and last valid byte of buffer

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	uint32 pos;                         ///< current (system) position in file

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	FILE *cur_fh;                       ///< current file handle

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	FILE *handles[MAX_HANDLES];         ///< array of file handles we can have open

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	byte buffer_start[FIO_BUFFER_SIZE]; ///< local buffer when read from file

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#if defined(LIMITED_FDS)

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	uint open_handles;                  ///< current amount of open handles

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	const char *filename[MAX_HANDLES];  ///< array of filenames we (should) have open

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	uint usage_count[MAX_HANDLES];      ///< count how many times this file has been opened

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#endif /* LIMITED_FDS */

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};

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static Fio _fio;

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/* Get current position in file */

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uint32 FioGetPos()

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{

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	return _fio.pos + (_fio.buffer - _fio.buffer_start) - FIO_BUFFER_SIZE;

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}

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void FioSeekTo(uint32 pos, int mode)

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{

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	if (mode == SEEK_CUR) pos += FioGetPos();

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	_fio.buffer = _fio.buffer_end = _fio.buffer_start + FIO_BUFFER_SIZE;

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	_fio.pos = pos;

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	fseek(_fio.cur_fh, _fio.pos, SEEK_SET);

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}

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#if defined(LIMITED_FDS)

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static void FioRestoreFile(int slot)

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{

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	/* Do we still have the file open, or should we reopen it? */

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	if (_fio.handles[slot] == NULL) {

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		DEBUG(misc, 6, "Restoring file '%s' in slot '%d' from disk", _fio.filename[slot], slot);

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		FioOpenFile(slot, _fio.filename[slot]);

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	}

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	_fio.usage_count[slot]++;

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}

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#endif /* LIMITED_FDS */

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/* Seek to a file and a position */

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void FioSeekToFile(uint32 pos)

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{

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	FILE *f;

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#if defined(LIMITED_FDS)

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	/* Make sure we have this file open */

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	FioRestoreFile(pos >> 24);

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#endif /* LIMITED_FDS */

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	f = _fio.handles[pos >> 24];

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	assert(f != NULL);

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	_fio.cur_fh = f;

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	FioSeekTo(GB(pos, 0, 24), SEEK_SET);

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}

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byte FioReadByte()

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{

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	if (_fio.buffer == _fio.buffer_end) {

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		_fio.pos += FIO_BUFFER_SIZE;

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		fread(_fio.buffer = _fio.buffer_start, 1, FIO_BUFFER_SIZE, _fio.cur_fh);

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	}

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	return *_fio.buffer++;

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}

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void FioSkipBytes(int n)

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{

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	for (;;) {

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		int m = min(_fio.buffer_end - _fio.buffer, n);

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		_fio.buffer += m;

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		n -= m;

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		if (n == 0) break;

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		FioReadByte();

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		n--;

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	}

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}

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uint16 FioReadWord()

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{

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	byte b = FioReadByte();

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	return (FioReadByte() << 8) | b;

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}

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uint32 FioReadDword()

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{

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	uint b = FioReadWord();

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	return (FioReadWord() << 16) | b;

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}

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void FioReadBlock(void *ptr, uint size)

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{

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	FioSeekTo(FioGetPos(), SEEK_SET);

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	_fio.pos += size;

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	fread(ptr, 1, size, _fio.cur_fh);

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}

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static inline void FioCloseFile(int slot)

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{

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	if (_fio.handles[slot] != NULL) {

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		fclose(_fio.handles[slot]);

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		_fio.handles[slot] = NULL;

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#if defined(LIMITED_FDS)

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		_fio.open_handles--;

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#endif /* LIMITED_FDS */

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	}

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}

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void FioCloseAll()

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{

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	int i;

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	for (i = 0; i != lengthof(_fio.handles); i++)

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		FioCloseFile(i);

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}

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bool FioCheckFileExists(const char *filename)

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{

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	FILE *f = FioFOpenFile(filename);

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	if (f == NULL) return false;

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	fclose(f);

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	return true;

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}

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#if defined(LIMITED_FDS)

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static void FioFreeHandle()

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{

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	/* If we are about to open a file that will exceed the limit, close a file */

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	if (_fio.open_handles + 1 == LIMITED_FDS) {

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		uint i, count;

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		int slot;

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		count = UINT_MAX;

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		slot = -1;

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		/* Find the file that is used the least */

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		for (i = 0; i < lengthof(_fio.handles); i++) {

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			if (_fio.handles[i] != NULL && _fio.usage_count[i] < count) {

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				count = _fio.usage_count[i];

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				slot  = i;

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			}

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		}

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		assert(slot != -1);

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		DEBUG(misc, 6, "Closing filehandler '%s' in slot '%d' because of fd-limit", _fio.filename[slot], slot);

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		FioCloseFile(slot);

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	}

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}

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#endif /* LIMITED_FDS */

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FILE *FioFOpenFile(const char *filename)

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{

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	FILE *f;

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	char buf[MAX_PATH];

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	snprintf(buf, lengthof(buf), "%s%s", _paths.data_dir, filename);

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	f = fopen(buf, "rb");

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#if !defined(WIN32)

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	if (f == NULL) {

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		strtolower(buf + strlen(_paths.data_dir) - 1);

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		f = fopen(buf, "rb");

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#if defined SECOND_DATA_DIR

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		/* tries in the 2nd data directory */

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		if (f == NULL) {

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			snprintf(buf, lengthof(buf), "%s%s", _paths.second_data_dir, filename);

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			strtolower(buf + strlen(_paths.second_data_dir) - 1);

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			f = fopen(buf, "rb");

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		}

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#endif

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	}

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#endif

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	return f;

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}

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void FioOpenFile(int slot, const char *filename)

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{

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	FILE *f;

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#if defined(LIMITED_FDS)

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	FioFreeHandle();

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#endif /* LIMITED_FDS */

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	f = FioFOpenFile(filename);

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	if (f == NULL) error("Cannot open file '%s%s'", _paths.data_dir, filename);

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	FioCloseFile(slot); // if file was opened before, close it

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	_fio.handles[slot] = f;

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#if defined(LIMITED_FDS)

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	_fio.filename[slot] = filename;

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	_fio.usage_count[slot] = 0;

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	_fio.open_handles++;

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#endif /* LIMITED_FDS */

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	FioSeekToFile(slot << 24);

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}