path: root/src/saveload.cpp

/* $Id$ */

/** @file saveload.cpp
 * All actions handling saving and loading goes on in this file. The general actions
 * are as follows for saving a game (loading is analogous):
 * <ol>
 * <li>initialize the writer by creating a temporary memory-buffer for it
 * <li>go through all to-be saved elements, each 'chunk' (ChunkHandler) prefixed by a label
 * <li>use their description array (SaveLoad) to know what elements to save and in what version
 *    of the game it was active (used when loading)
 * <li>write all data byte-by-byte to the temporary buffer so it is endian-safe
 * <li>when the buffer is full; flush it to the output (eg save to file) (_sl.buf, _sl.bufp, _sl.bufe)
 * <li>repeat this until everything is done, and flush any remaining output to file
 * </ol>
 */
#include "stdafx.h"
#include "openttd.h"
#include "debug.h"
#include "station_base.h"
#include "thread.h"
#include "town.h"
#include "saveload.h"
#include "network/network.h"
#include "variables.h"
#include "window_func.h"
#include "strings_func.h"
#include "gfx_func.h"
#include "core/alloc_func.hpp"
#include "functions.h"
#include "core/endian_func.hpp"
#include "vehicle_base.h"
#include "autoreplace_base.h"
#include "statusbar_gui.h"
#include "fileio_func.h"
#include <list>
#include "gamelog.h"

#include "table/strings.h"

extern const uint16 SAVEGAME_VERSION = 102;

SavegameType _savegame_type; ///< type of savegame we are loading

uint32 _ttdp_version;     ///< version of TTDP savegame (if applicable)
uint16 _sl_version;       ///< the major savegame version identifier
byte   _sl_minor_version; ///< the minor savegame version, DO NOT USE!

typedef void WriterProc(size_t len);
typedef size_t ReaderProc();

/** The saveload struct, containing reader-writer functions, bufffer, version, etc. */
static struct {
	bool save;                           ///< are we doing a save or a load atm. True when saving
	byte need_length;                    ///< ???
	byte block_mode;                     ///< ???
	bool error;                          ///< did an error occur or not

	size_t obj_len;                      ///< the length of the current object we are busy with
	int array_index, last_array_index;   ///< in the case of an array, the current and last positions

	size_t offs_base;                    ///< the offset in number of bytes since we started writing data (eg uncompressed savegame size)

	WriterProc *write_bytes;             ///< savegame writer function
	ReaderProc *read_bytes;              ///< savegame loader function

	const ChunkHandler* const *chs;      ///< the chunk of data that is being processed atm (vehicles, signs, etc.)

	/* When saving/loading savegames, they are always saved to a temporary memory-place
	 * to be flushed to file (save) or to final place (load) when full. */
	byte *bufp, *bufe;                   ///< bufp(ointer) gives the current position in the buffer bufe(nd) gives the end of the buffer

	/* these 3 may be used by compressor/decompressors. */
	byte *buf;                           ///< pointer to temporary memory to read/write, initialized by SaveLoadFormat->initread/write
	byte *buf_ori;                       ///< pointer to the original memory location of buf, used to free it afterwards
	uint bufsize;                        ///< the size of the temporary memory *buf
	FILE *fh;                            ///< the file from which is read or written to

	void (*excpt_uninit)();              ///< the function to execute on any encountered error
	StringID error_str;                  ///< the translateable error message to show
	char *extra_msg;                     ///< the error message
} _sl;


enum NeedLengthValues {NL_NONE = 0, NL_WANTLENGTH = 1, NL_CALCLENGTH = 2};

/** Error handler, calls longjmp to simulate an exception.
 * @todo this was used to have a central place to handle errors, but it is
 * pretty ugly, and seriously interferes with any multithreaded approaches */
static void NORETURN SlError(StringID string, const char *extra_msg = NULL)
{
	_sl.error_str = string;
	free(_sl.extra_msg);
	_sl.extra_msg = (extra_msg == NULL) ? NULL : strdup(extra_msg);
	throw std::exception();
}

typedef void (*AsyncSaveFinishProc)();
static AsyncSaveFinishProc _async_save_finish = NULL;
static ThreadObject *_save_thread;

/**
 * Called by save thread to tell we finished saving.
 */
static void SetAsyncSaveFinish(AsyncSaveFinishProc proc)
{
	if (_exit_game) return;
	while (_async_save_finish != NULL) CSleep(10);

	_async_save_finish = proc;
}

/**
 * Handle async save finishes.
 */
void ProcessAsyncSaveFinish()
{
	if (_async_save_finish == NULL) return;

	_async_save_finish();

	_async_save_finish = NULL;

	if (_save_thread != NULL) {
		_save_thread->Join();
		delete _save_thread;
		_save_thread = NULL;
	}
}

/**
 * Fill the input buffer by reading from the file with the given reader
 */
static void SlReadFill()
{
	size_t len = _sl.read_bytes();
	if (len == 0) SlError(STR_GAME_SAVELOAD_ERROR_BROKEN_SAVEGAME, "Unexpected end of chunk");

	_sl.bufp = _sl.buf;
	_sl.bufe = _sl.buf + len;
	_sl.offs_base += len;
}

static inline size_t SlGetOffs() {return _sl.offs_base - (_sl.bufe - _sl.bufp);}

/** Return the size in bytes of a certain type of normal/atomic variable
 * as it appears in memory. See VarTypes
 * @param conv VarType type of variable that is used for calculating the size
 * @return Return the size of this type in bytes */
static inline byte SlCalcConvMemLen(VarType conv)
{
	static const byte conv_mem_size[] = {1, 1, 1, 2, 2, 4, 4, 8, 8, 0};
	byte length = GB(conv, 4, 4);
	assert(length < lengthof(conv_mem_size));
	return conv_mem_size[length];
}

/** Return the size in bytes of a certain type of normal/atomic variable
 * as it appears in a saved game. See VarTypes
 * @param conv VarType type of variable that is used for calculating the size
 * @return Return the size of this type in bytes */
static inline byte SlCalcConvFileLen(VarType conv)
{
	static const byte conv_file_size[] = {1, 1, 2, 2, 4, 4, 8, 8, 2};
	byte length = GB(conv, 0, 4);
	assert(length < lengthof(conv_file_size));
	return conv_file_size[length];
}

/** Return the size in bytes of a reference (pointer) */
static inline size_t SlCalcRefLen() {return CheckSavegameVersion(69) ? 2 : 4;}

/** Flush the output buffer by writing to disk with the given reader.
 * If the buffer pointer has not yet been set up, set it up now. Usually
 * only called when the buffer is full, or there is no more data to be processed
 */
static void SlWriteFill()
{
	/* flush the buffer to disk (the writer) */
	if (_sl.bufp != NULL) {
		uint len = _sl.bufp - _sl.buf;
		_sl.offs_base += len;
		if (len) _sl.write_bytes(len);
	}

	/* All the data from the buffer has been written away, rewind to the beginning
	 * to start reading in more data */
	_sl.bufp = _sl.buf;
	_sl.bufe = _sl.buf + _sl.bufsize;
}

/** Read in a single byte from file. If the temporary buffer is full,
 * flush it to its final destination
 * @return return the read byte from file
 */
static inline byte SlReadByteInternal()
{
	if (_sl.bufp == _sl.bufe) SlReadFill();
	return *_sl.bufp++;
}

/** Wrapper for SlReadByteInternal */
byte SlReadByte() {return SlReadByteInternal();}

/** Write away a single byte from memory. If the temporary buffer is full,
 * flush it to its destination (file)
 * @param b the byte that is currently written
 */
static inline void SlWriteByteInternal(byte b)
{
	if (_sl.bufp == _sl.bufe) SlWriteFill();
	*_sl.bufp++ = b;
}

/** Wrapper for SlWriteByteInternal */
void SlWriteByte(byte b) {SlWriteByteInternal(b);}

static inline int SlReadUint16()
{
	int x = SlReadByte() << 8;
	return x | SlReadByte();
}

static inline uint32 SlReadUint32()
{
	uint32 x = SlReadUint16() << 16;
	return x | SlReadUint16();
}

static inline uint64 SlReadUint64()
{
	uint32 x = SlReadUint32();
	uint32 y = SlReadUint32();
	return (uint64)x << 32 | y;
}

static inline void SlWriteUint16(uint16 v)
{
	SlWriteByte(GB(v, 8, 8));
	SlWriteByte(GB(v, 0, 8));
}

static inline void SlWriteUint32(uint32 v)
{
	SlWriteUint16(GB(v, 16, 16));
	SlWriteUint16(GB(v,  0, 16));
}

static inline void SlWriteUint64(uint64 x)
{
	SlWriteUint32((uint32)(x >> 32));
	SlWriteUint32((uint32)x);
}

/**
 * Read in the header descriptor of an object or an array.
 * If the highest bit is set (7), then the index is bigger than 127
 * elements, so use the next byte to read in the real value.
 * The actual value is then both bytes added with the first shifted
 * 8 bits to the left, and dropping the highest bit (which only indicated a big index).
 * x = ((x & 0x7F) << 8) + SlReadByte();
 * @return Return the value of the index
 */
static uint SlReadSimpleGamma()
{
	uint i = SlReadByte();
	if (HasBit(i, 7)) {
		i &= ~0x80;
		if (HasBit(i, 6)) {
			i &= ~0x40;
			if (HasBit(i, 5)) {
				i &= ~0x20;
				if (HasBit(i, 4))
					SlError(STR_GAME_SAVELOAD_ERROR_BROKEN_SAVEGAME, "Unsupported gamma");
				i = (i << 8) | SlReadByte();
			}
			i = (i << 8) | SlReadByte();
		}
		i = (i << 8) | SlReadByte();
	}
	return i;
}

/**
 * Write the header descriptor of an object or an array.
 * If the element is bigger than 127, use 2 bytes for saving
 * and use the highest byte of the first written one as a notice
 * that the length consists of 2 bytes, etc.. like this:
 * 0xxxxxxx
 * 10xxxxxx xxxxxxxx
 * 110xxxxx xxxxxxxx xxxxxxxx
 * 1110xxxx xxxxxxxx xxxxxxxx xxxxxxxx
 * @param i Index being written
 */

static void SlWriteSimpleGamma(size_t i)
{
	if (i >= (1 << 7)) {
		if (i >= (1 << 14)) {
			if (i >= (1 << 21)) {
				assert(i < (1 << 28));
				SlWriteByte((byte)(0xE0 | (i >> 24)));
				SlWriteByte((byte)(i >> 16));
			} else {
				SlWriteByte((byte)(0xC0 | (i >> 16)));
			}
			SlWriteByte((byte)(i >> 8));
		} else {
			SlWriteByte((byte)(0x80 | (i >> 8)));
		}
	}
	SlWriteByte((byte)i);
}

/** Return how many bytes used to encode a gamma value */
static inline uint SlGetGammaLength(size_t i)
{
	return 1 + (i >= (1 << 7)) + (i >= (1 << 14)) + (i >= (1 << 21));
}

static inline uint SlReadSparseIndex() {return SlReadSimpleGamma();}
static inline void SlWriteSparseIndex(uint index) {SlWriteSimpleGamma(index);}

static inline uint SlReadArrayLength() {return SlReadSimpleGamma();}
static inline void SlWriteArrayLength(size_t length) {SlWriteSimpleGamma(length);}
static inline uint SlGetArrayLength(size_t length) {return SlGetGammaLength(length);}

void SlSetArrayIndex(uint index)
{
	_sl.need_length = NL_WANTLENGTH;
	_sl.array_index = index;
}

static size_t _next_offs;

/**
 * Iterate through the elements of an array and read the whole thing
 * @return The index of the object, or -1 if we have reached the end of current block
 */
int SlIterateArray()
{
	int index;

	/* After reading in the whole array inside the loop
	 * we must have read in all the data, so we must be at end of current block. */
	if (_next_offs != 0 && SlGetOffs() != _next_offs) SlError(STR_GAME_SAVELOAD_ERROR_BROKEN_SAVEGAME, "Invalid chunk size");

	while (true) {
		uint length = SlReadArrayLength();
		if (length == 0) {
			_next_offs = 0;
			return -1;
		}

		_sl.obj_len = --length;
		_next_offs = SlGetOffs() + length;

		switch (_sl.block_mode) {
		case CH_SPARSE_ARRAY: index = (int)SlReadSparseIndex(); break;
		case CH_ARRAY:        index = _sl.array_index++; break;
		default:
			DEBUG(sl, 0, "SlIterateArray error");
			return -1; // error
		}

		if (length != 0) return index;
	}
}

/**
 * Sets the length of either a RIFF object or the number of items in an array.
 * This lets us load an object or an array of arbitrary size
 * @param length The length of the sought object/array
 */
void SlSetLength(size_t length)
{
	assert(_sl.save);

	switch (_sl.need_length) {
	case NL_WANTLENGTH:
		_sl.need_length = NL_NONE;
		switch (_sl.block_mode) {
		case CH_RIFF:
			/* Ugly encoding of >16M RIFF chunks
			 * The lower 24 bits are normal
			 * The uppermost 4 bits are bits 24:27 */
			assert(length < (1 << 28));
			SlWriteUint32((uint32)((length & 0xFFFFFF) | ((length >> 24) << 28)));
			break;
		case CH_ARRAY:
			assert(_sl.last_array_index <= _sl.array_index);
			while (++_sl.last_array_index <= _sl.array_index)
				SlWriteArrayLength(1);
			SlWriteArrayLength(length + 1);
			break;
		case CH_SPARSE_ARRAY:
			SlWriteArrayLength(length + 1 + SlGetArrayLength(_sl.array_index)); // Also include length of sparse index.
			SlWriteSparseIndex(_sl.array_index);
			break;
		default: NOT_REACHED();
		} break;
	case NL_CALCLENGTH:
		_sl.obj_len += (int)length;
		break;
	}
}

/**
 * Save/Load bytes. These do not need to be converted to Little/Big Endian
 * so directly write them or read them to/from file
 * @param ptr The source or destination of the object being manipulated
 * @param length number of bytes this fast CopyBytes lasts
 */
static void SlCopyBytes(void *ptr, size_t length)
{
	byte *p = (byte*)ptr;

	if (_sl.save) {
		for (; length != 0; length--) {SlWriteByteInternal(*p++);}
	} else {
		for (; length != 0; length--) {*p++ = SlReadByteInternal();}
	}
}

/** Read in bytes from the file/data structure but don't do
 * anything with them, discarding them in effect
 * @param length The amount of bytes that is being treated this way
 */
static inline void SlSkipBytes(size_t length)
{
	for (; length != 0; length--) SlReadByte();
}

/* Get the length of the current object */
size_t SlGetFieldLength() {return _sl.obj_len;}

/** Return a signed-long version of the value of a setting
 * @param ptr pointer to the variable
 * @param conv type of variable, can be a non-clean
 * type, eg one with other flags because it is parsed
 * @return returns the value of the pointer-setting */
int64 ReadValue(const void *ptr, VarType conv)
{
	switch (GetVarMemType(conv)) {
	case SLE_VAR_BL:  return (*(bool*)ptr != 0);
	case SLE_VAR_I8:  return *(int8*  )ptr;
	case SLE_VAR_U8:  return *(byte*  )ptr;
	case SLE_VAR_I16: return *(int16* )ptr;
	case SLE_VAR_U16: return *(uint16*)ptr;
	case SLE_VAR_I32: return *(int32* )ptr;
	case SLE_VAR_U32: return *(uint32*)ptr;
	case SLE_VAR_I64: return *(int64* )ptr;
	case SLE_VAR_U64: return *(uint64*)ptr;
	case SLE_VAR_NULL:return 0;
	default: NOT_REACHED();
	}

	/* useless, but avoids compiler warning this way */
	return 0;
}

/** Write the value of a setting
 * @param ptr pointer to the variable
 * @param conv type of variable, can be a non-clean type, eg
 *             with other flags. It is parsed upon read
 * @param val the new value being given to the variable */
void WriteValue(void *ptr, VarType conv, int64 val)
{
	switch (GetVarMemType(conv)) {
	case SLE_VAR_BL:  *(bool  *)ptr = (val != 0);  break;
	case SLE_VAR_I8:  *(int8  *)ptr = val; break;
	case SLE_VAR_U8:  *(byte  *)ptr = val; break;
	case SLE_VAR_I16: *(int16 *)ptr = val; break;
	case SLE_VAR_U16: *(uint16*)ptr = val; break;
	case SLE_VAR_I32: *(int32 *)ptr = val; break;
	case SLE_VAR_U32: *(uint32*)ptr = val; break;
	case SLE_VAR_I64: *(int64 *)ptr = val; break;
	case SLE_VAR_U64: *(uint64*)ptr = val; break;
	case SLE_VAR_NAME: *(char**)ptr = CopyFromOldName(val); break;
	case SLE_VAR_NULL: break;
	default: NOT_REACHED();
	}
}

/**
 * Handle all conversion and typechecking of variables here.
 * In the case of saving, read in the actual value from the struct
 * and then write them to file, endian safely. Loading a value
 * goes exactly the opposite way
 * @param ptr The object being filled/read
 * @param conv VarType type of the current element of the struct
 */
static void SlSaveLoadConv(void *ptr, VarType conv)
{
	int64 x = 0;

	if (_sl.save) { // SAVE values
		/* Read a value from the struct. These ARE endian safe. */
		x = ReadValue(ptr, conv);

		/* Write the value to the file and check if its value is in the desired range */
		switch (GetVarFileType(conv)) {
		case SLE_FILE_I8: assert(x >= -128 && x <= 127);     SlWriteByte(x);break;
		case SLE_FILE_U8: assert(x >= 0 && x <= 255);        SlWriteByte(x);break;
		case SLE_FILE_I16:assert(x >= -32768 && x <= 32767); SlWriteUint16(x);break;
		case SLE_FILE_STRINGID:
		case SLE_FILE_U16:assert(x >= 0 && x <= 65535);      SlWriteUint16(x);break;
		case SLE_FILE_I32:
		case SLE_FILE_U32:                                   SlWriteUint32((uint32)x);break;
		case SLE_FILE_I64:
		case SLE_FILE_U64:                                   SlWriteUint64(x);break;
		default: NOT_REACHED();
		}
	} else { // LOAD values

		/* Read a value from the file */
		switch (GetVarFileType(conv)) {
		case SLE_FILE_I8:  x = (int8  )SlReadByte();   break;
		case SLE_FILE_U8:  x = (byte  )SlReadByte();   break;
		case SLE_FILE_I16: x = (int16 )SlReadUint16(); break;
		case SLE_FILE_U16: x = (uint16)SlReadUint16(); break;
		case SLE_FILE_I32: x = (int32 )SlReadUint32(); break;
		case SLE_FILE_U32: x = (uint32)SlReadUint32(); break;
		case SLE_FILE_I64: x = (int64 )SlReadUint64(); break;
		case SLE_FILE_U64: x = (uint64)SlReadUint64(); break;
		case SLE_FILE_STRINGID: x = RemapOldStringID((uint16)SlReadUint16()); break;
		default: NOT_REACHED();
		}

		/* Write The value to the struct. These ARE endian safe. */
		WriteValue(ptr, conv, x);
	}
}

/** Calculate the net length of a string. This is in almost all cases
 * just strlen(), but if the string is not properly terminated, we'll
 * resort to the maximum length of the buffer.
 * @param ptr pointer to the stringbuffer
 * @param length maximum length of the string (buffer). If -1 we don't care
 * about a maximum length, but take string length as it is.
 * @return return the net length of the string */
static inline size_t SlCalcNetStringLen(const char *ptr, size_t length)
{
	if (ptr == NULL) return 0;
	return min(strlen(ptr), length - 1);
}

/** Calculate the gross length of the string that it
 * will occupy in the savegame. This includes the real length, returned
 * by SlCalcNetStringLen and the length that the index will occupy.
 * @param ptr pointer to the stringbuffer
 * @param length maximum length of the string (buffer size, etc.)
 * @param conv type of data been used
 * @return return the gross length of the string */
static inline size_t SlCalcStringLen(const void *ptr, size_t length, VarType conv)
{
	size_t len;
	const char *str;

	switch (GetVarMemType(conv)) {
		default: NOT_REACHED();
		case SLE_VAR_STR:
		case SLE_VAR_STRQ:
			str = *(const char**)ptr;
			len = SIZE_MAX;
			break;
		case SLE_VAR_STRB:
		case SLE_VAR_STRBQ:
			str = (const char*)ptr;
			len = length;
			break;
	}

	len = SlCalcNetStringLen(str, len);
	return len + SlGetArrayLength(len); // also include the length of the index
}

/**
 * Save/Load a string.
 * @param ptr the string being manipulated
 * @param length of the string (full length)
 * @param conv must be SLE_FILE_STRING */
static void SlString(void *ptr, size_t length, VarType conv)
{
	size_t len;

	if (_sl.save) { // SAVE string
		switch (GetVarMemType(conv)) {
			default: NOT_REACHED();
			case SLE_VAR_STRB:
			case SLE_VAR_STRBQ:
				len = SlCalcNetStringLen((char*)ptr, length);
				break;
			case SLE_VAR_STR:
			case SLE_VAR_STRQ:
				ptr = *(char**)ptr;
				len = SlCalcNetStringLen((char*)ptr, SIZE_MAX);
				break;
		}

		SlWriteArrayLength(len);
		SlCopyBytes(ptr, len);
	} else { // LOAD string
		len = SlReadArrayLength();

		switch (GetVarMemType(conv)) {
			default: NOT_REACHED();
			case SLE_VAR_STRB:
			case SLE_VAR_STRBQ:
				if (len >= length) {
					DEBUG(sl, 1, "String length in savegame is bigger than buffer, truncating");
					SlCopyBytes(ptr, length);
					SlSkipBytes(len - length);
					len = length - 1;
				} else {
					SlCopyBytes(ptr, len);
				}
				break;
			case SLE_VAR_STR:
			case SLE_VAR_STRQ: // Malloc'd string, free previous incarnation, and allocate
				free(*(char**)ptr);
				if (len == 0) {
					*(char**)ptr = NULL;
				} else {
					*(char**)ptr = MallocT<char>(len + 1); // terminating '\0'
					ptr = *(char**)ptr;
					SlCopyBytes(ptr, len);
				}
				break;
		}

		((char*)ptr)[len] = '\0'; // properly terminate the string
	}
}

/**
 * Return the size in bytes of a certain type of atomic array
 * @param length The length of the array counted in elements
 * @param conv VarType type of the variable that is used in calculating the size
 */
static inline size_t SlCalcArrayLen(size_t length, VarType conv)
{
	return SlCalcConvFileLen(conv) * length;
}

/**
 * Save/Load an array.
 * @param array The array being manipulated
 * @param length The length of the array in elements
 * @param conv VarType type of the atomic array (int, byte, uint64, etc.)
 */
void SlArray(void *array, size_t length, VarType conv)
{
	/* Automatically calculate the length? */
	if (_sl.need_length != NL_NONE) {
		SlSetLength(SlCalcArrayLen(length, conv));
		/* Determine length only? */
		if (_sl.need_length == NL_CALCLENGTH) return;
	}

	/* NOTICE - handle some buggy stuff, in really old versions everything was saved
	 * as a byte-type. So detect this, and adjust array size accordingly */
	if (!_sl.save && _sl_version == 0) {
		/* all arrays except difficulty settings */
		if (conv == SLE_INT16 || conv == SLE_UINT16 || conv == SLE_STRINGID ||
				conv == SLE_INT32 || conv == SLE_UINT32) {
			SlCopyBytes(array, length * SlCalcConvFileLen(conv));
			return;
		}
		/* used for conversion of Money 32bit->64bit */
		if (conv == (SLE_FILE_I32 | SLE_VAR_I64)) {
			for (uint i = 0; i < length; i++) {
				((int64*)array)[i] = (int32)BSWAP32(SlReadUint32());
			}
			return;
		}
	}

	/* If the size of elements is 1 byte both in file and memory, no special
	 * conversion is needed, use specialized copy-copy function to speed up things */
	if (conv == SLE_INT8 || conv == SLE_UINT8) {
		SlCopyBytes(array, length);
	} else {
		byte *a = (byte*)array;
		byte mem_size = SlCalcConvMemLen(conv);

		for (; length != 0; length --) {
			SlSaveLoadConv(a, conv);
			a += mem_size; // get size
		}
	}
}


static uint ReferenceToInt(const void* obj, SLRefType rt);
static void* IntToReference(uint index, SLRefType rt);


/**
 * Return the size in bytes of a list
 * @param list The std::list to find the size of
 */
static inline size_t SlCalcListLen(const void *list)
{
	std::list<void *> *l = (std::list<void *> *) list;

	int type_size = CheckSavegameVersion(69) ? 2 : 4;
	/* Each entry is saved as type_size bytes, plus type_size bytes are used for the length
	 * of the list */
	return l->size() * type_size + type_size;
}


/**
 * Save/Load a list.
 * @param list The list being manipulated
 * @param conv SLRefType type of the list (Vehicle *, Station *, etc)
 */
void SlList(void *list, SLRefType conv)
{
	/* Automatically calculate the length? */
	if (_sl.need_length != NL_NONE) {
		SlSetLength(SlCalcListLen(list));
		/* Determine length only? */
		if (_sl.need_length == NL_CALCLENGTH) return;
	}

	std::list<void *> *l = (std::list<void *> *) list;

	if (_sl.save) {
		SlWriteUint32((uint32)l->size());

		std::list<void *>::iterator iter;
		for (iter = l->begin(); iter != l->end(); ++iter) {
			void *ptr = *iter;
			SlWriteUint32(ReferenceToInt(ptr, conv));
		}
	} else {
		uint length = CheckSavegameVersion(69) ? SlReadUint16() : SlReadUint32();

		/* Load each reference and push to the end of the list */
		for (uint i = 0; i < length; i++) {
			void *ptr = IntToReference(CheckSavegameVersion(69) ? SlReadUint16() : SlReadUint32(), conv);
			l->push_back(ptr);
		}
	}
}


/** Are we going to save this object or not? */
static inline bool SlIsObjectValidInSavegame(const SaveLoad *sld)
{
	if (_sl_version < sld->version_from || _sl_version > sld->version_to) return false;
	if (sld->conv & SLF_SAVE_NO) return false;

	return true;
}

/** Are we going to load this variable when loading a savegame or not?
 * @note If the variable is skipped it is skipped in the savegame
 * bytestream itself as well, so there is no need to skip it somewhere else */
static inline bool SlSkipVariableOnLoad(const SaveLoad *sld)
{
	if ((sld->conv & SLF_NETWORK_NO) && !_sl.save && _networking && !_network_server) {
		SlSkipBytes(SlCalcConvMemLen(sld->conv) * sld->length);
		return true;
	}

	return false;
}

/**
 * Calculate the size of an object.
 * @param object to be measured
 * @param sld The SaveLoad description of the object so we know how to manipulate it
 * @return size of given objetc
 */
size_t SlCalcObjLength(const void *object, const SaveLoad *sld)
{
	size_t length = 0;

	/* Need to determine the length and write a length tag. */
	for (; sld->cmd != SL_END; sld++) {
		length += SlCalcObjMemberLength(object, sld);
	}
	return length;
}

size_t SlCalcObjMemberLength(const void *object, const SaveLoad *sld)
{
	assert(_sl.save);

	switch (sld->cmd) {
		case SL_VAR:
		case SL_REF:
		case SL_ARR:
		case SL_STR:
		case SL_LST:
			/* CONDITIONAL saveload types depend on the savegame version */
			if (!SlIsObjectValidInSavegame(sld)) break;

			switch (sld->cmd) {
			case SL_VAR: return SlCalcConvFileLen(sld->conv);
			case SL_REF: return SlCalcRefLen();
			case SL_ARR: return SlCalcArrayLen(sld->length, sld->conv);
			case SL_STR: return SlCalcStringLen(GetVariableAddress(object, sld), sld->length, sld->conv);
			case SL_LST: return SlCalcListLen(GetVariableAddress(object, sld));
			default: NOT_REACHED();
			}
			break;
		case SL_WRITEBYTE: return 1; // a byte is logically of size 1
		case SL_VEH_INCLUDE: return SlCalcObjLength(object, GetVehicleDescription(VEH_END));
		default: NOT_REACHED();
	}
	return 0;
}


bool SlObjectMember(void *ptr, const SaveLoad *sld)
{
	VarType conv = GB(sld->conv, 0, 8);
	switch (sld->cmd) {
	case SL_VAR:
	case SL_REF:
	case SL_ARR:
	case SL_STR:
	case SL_LST:
		/* CONDITIONAL saveload types depend on the savegame version */
		if (!SlIsObjectValidInSavegame(sld)) return false;
		if (SlSkipVariableOnLoad(sld)) return false;

		switch (sld->cmd) {
		case SL_VAR: SlSaveLoadConv(ptr, conv); break;
		case SL_REF: // Reference variable, translate
			if (_sl.save) {
				SlWriteUint32(ReferenceToInt(*(void**)ptr, (SLRefType)conv));
			} else {
				*(void**)ptr = IntToReference(CheckSavegameVersion(69) ? SlReadUint16() : SlReadUint32(), (SLRefType)conv);
			}
			break;
		case SL_ARR: SlArray(ptr, sld->length, conv); break;
		case SL_STR: SlString(ptr, sld->length, conv); break;
		case SL_LST: SlList(ptr, (SLRefType)conv); break;
		default: NOT_REACHED();
		}
		break;

	/* SL_WRITEBYTE translates a value of a variable to another one upon
	 * saving or loading.
	 * XXX - variable renaming abuse
	 * game_value: the value of the variable ingame is abused by sld->version_from
	 * file_value: the value of the variable in the savegame is abused by sld->version_to */
	case SL_WRITEBYTE:
		if (_sl.save) {
			SlWriteByte(sld->version_to);
		} else {
			*(byte*)ptr = sld->version_from;
		}
		break;

	/* SL_VEH_INCLUDE loads common code for vehicles */
	case SL_VEH_INCLUDE:
		SlObject(ptr, GetVehicleDescription(VEH_END));
		break;
	default: NOT_REACHED();
	}
	return true;
}

/**
 * Main SaveLoad function.
 * @param object The object that is being saved or loaded
 * @param sld The SaveLoad description of the object so we know how to manipulate it
 */
void SlObject(void *object, const SaveLoad *sld)
{
	/* Automatically calculate the length? */
	if (_sl.need_length != NL_NONE) {
		SlSetLength(SlCalcObjLength(object, sld));
		if (_sl.need_length == NL_CALCLENGTH) return;
	}

	for (; sld->cmd != SL_END; sld++) {
		void *ptr = sld->global ? sld->address : GetVariableAddress(object, sld);
		SlObjectMember(ptr, sld);
	}
}

/**
 * Save or Load (a list of) global variables
 * @param sldg The global variable that is being loaded or saved
 */
void SlGlobList(const SaveLoadGlobVarList *sldg)
{
	SlObject(NULL, (const SaveLoad*)sldg);
}

/**
 * Do something of which I have no idea what it is :P
 * @param proc The callback procedure that is called
 * @param arg The variable that will be used for the callback procedure
 */
void SlAutolength(AutolengthProc *proc, void *arg)
{
	size_t offs;

	assert(_sl.save);

	/* Tell it to calculate the length */
	_sl.need_length = NL_CALCLENGTH;
	_sl.obj_len = 0;
	proc(arg);

	/* Setup length */
	_sl.need_length = NL_WANTLENGTH;
	SlSetLength(_sl.obj_len);

	offs = SlGetOffs() + _sl.obj_len;

	/* And write the stuff */
	proc(arg);

	if (offs != SlGetOffs()) SlError(STR_GAME_SAVELOAD_ERROR_BROKEN_SAVEGAME, "Invalid chunk size");
}

/**
 * Load a chunk of data (eg vehicles, stations, etc.)
 * @param ch The chunkhandler that will be used for the operation
 */
static void SlLoadChunk(const ChunkHandler *ch)
{
	byte m = SlReadByte();
	size_t len;
	size_t endoffs;

	_sl.block_mode = m;
	_sl.obj_len = 0;

	switch (m) {
	case CH_ARRAY:
		_sl.array_index = 0;
		ch->load_proc();
		break;
	case CH_SPARSE_ARRAY:
		ch->load_proc();
		break;
	default:
		if ((m & 0xF) == CH_RIFF) {
			/* Read length */
			len = (SlReadByte() << 16) | ((m >> 4) << 24);
			len += SlReadUint16();
			_sl.obj_len = len;
			endoffs = SlGetOffs() + len;
			ch->load_proc();
			if (SlGetOffs() != endoffs) SlError(STR_GAME_SAVELOAD_ERROR_BROKEN_SAVEGAME, "Invalid chunk size");
		} else {
			SlError(STR_GAME_SAVELOAD_ERROR_BROKEN_SAVEGAME, "Invalid chunk type");
		}
		break;
	}
}

/* Stub Chunk handlers to only calculate length and do nothing else */
static ChunkSaveLoadProc *_tmp_proc_1;
static inline void SlStubSaveProc2(void *arg) {_tmp_proc_1();}
static void SlStubSaveProc() {SlAutolength(SlStubSaveProc2, NULL);}

/** Save a chunk of data (eg. vehicles, stations, etc.). Each chunk is
 * prefixed by an ID identifying it, followed by data, and terminator where appropiate
 * @param ch The chunkhandler that will be used for the operation
 */
static void SlSaveChunk(const ChunkHandler *ch)
{
	ChunkSaveLoadProc *proc = ch->save_proc;

	/* Don't save any chunk information if there is no save handler. */
	if (proc == NULL) return;

	SlWriteUint32(ch->id);
	DEBUG(sl, 2, "Saving chunk %c%c%c%c", ch->id >> 24, ch->id >> 16, ch->id >> 8, ch->id);

	if (ch->flags & CH_AUTO_LENGTH) {
		/* Need to calculate the length. Solve that by calling SlAutoLength in the save_proc. */
		_tmp_proc_1 = proc;
		proc = SlStubSaveProc;
	}

	_sl.block_mode = ch->flags & CH_TYPE_MASK;
	switch (ch->flags & CH_TYPE_MASK) {
	case CH_RIFF:
		_sl.need_length = NL_WANTLENGTH;
		proc();
		break;
	case CH_ARRAY:
		_sl.last_array_index = 0;
		SlWriteByte(CH_ARRAY);
		proc();
		SlWriteArrayLength(0); // Terminate arrays
		break;
	case CH_SPARSE_ARRAY:
		SlWriteByte(CH_SPARSE_ARRAY);
		proc();
		SlWriteArrayLength(0); // Terminate arrays
		break;
	default: NOT_REACHED();
	}
}

/** Save all chunks */
static void SlSaveChunks()
{
	const ChunkHandler *ch;
	const ChunkHandler* const *chsc;
	uint p;

	for (p = 0; p != CH_NUM_PRI_LEVELS; p++) {
		for (chsc = _sl.chs; (ch = *chsc++) != NULL;) {
			while (true) {
				if (((ch->flags >> CH_PRI_SHL) & (CH_NUM_PRI_LEVELS - 1)) == p)
					SlSaveChunk(ch);
				if (ch->flags & CH_LAST)
					break;
				ch++;
			}
		}
	}

	/* Terminator */
	SlWriteUint32(0);
}

/** Find the ChunkHandler that will be used for processing the found
 * chunk in the savegame or in memory
 * @param id the chunk in question
 * @return returns the appropiate chunkhandler
 */
static const ChunkHandler *SlFindChunkHandler(uint32 id)
{
	const ChunkHandler *ch;
	const ChunkHandler *const *chsc;
	for (chsc = _sl.chs; (ch = *chsc++) != NULL;) {
		for (;;) {
			if (ch->id == id) return ch;
			if (ch->flags & CH_LAST) break;
			ch++;
		}
	}
	return NULL;
}

/** Load all chunks */
static void SlLoadChunks()
{
	uint32 id;
	const ChunkHandler *ch;

	for (id = SlReadUint32(); id != 0; id = SlReadUint32()) {
		DEBUG(sl, 2, "Loading chunk %c%c%c%c", id >> 24, id >> 16, id >> 8, id);

		ch = SlFindChunkHandler(id);
		if (ch == NULL) SlError(STR_GAME_SAVELOAD_ERROR_BROKEN_SAVEGAME, "Unknown chunk type");
		SlLoadChunk(ch);
	}
}

/*******************************************
 ********** START OF LZO CODE **************
 *******************************************/
#define LZO_SIZE 8192

#include "minilzo.h"

static size_t ReadLZO()
{
	byte out[LZO_SIZE + LZO_SIZE / 64 + 16 + 3 + 8];
	uint32 tmp[2];
	uint32 size;
	uint len;

	/* Read header*/
	if (fread(tmp, sizeof(tmp), 1, _sl.fh) != 1) SlError(STR_GAME_SAVELOAD_ERROR_FILE_NOT_READABLE, "File read failed");

	/* Check if size is bad */
	((uint32*)out)[0] = size = tmp[1];

	if (_sl_version != 0) {
		tmp[0] = TO_BE32(tmp[0]);
		size = TO_BE32(size);
	}

	if (size >= sizeof(out)) SlError(STR_GAME_SAVELOAD_ERROR_BROKEN_SAVEGAME, "Inconsistent size");

	/* Read block */
	if (fread(out + sizeof(uint32), size, 1, _sl.fh) != 1) SlError(STR_GAME_SAVELOAD_ERROR_FILE_NOT_READABLE);

	/* Verify checksum */
	if (tmp[0] != lzo_adler32(0, out, size + sizeof(uint32))) SlError(STR_GAME_SAVELOAD_ERROR_BROKEN_SAVEGAME, "Bad checksum");

	/* Decompress */
	lzo1x_decompress(out + sizeof(uint32)*1, size, _sl.buf, &len, NULL);
	return len;
}

/* p contains the pointer to the buffer, len contains the pointer to the length.
 * len bytes will be written, p and l will be updated to reflect the next buffer. */
static void WriteLZO(size_t size)
{
	byte out[LZO_SIZE + LZO_SIZE / 64 + 16 + 3 + 8];
	byte wrkmem[sizeof(byte*)*4096];
	uint outlen;

	lzo1x_1_compress(_sl.buf, (lzo_uint)size, out + sizeof(uint32)*2, &outlen, wrkmem);
	((uint32*)out)[1] = TO_BE32(outlen);
	((uint32*)out)[0] = TO_BE32(lzo_adler32(0, out + sizeof(uint32), outlen + sizeof(uint32)));
	if (fwrite(out, outlen + sizeof(uint32)*2, 1, _sl.fh) != 1) SlError(STR_GAME_SAVELOAD_ERROR_FILE_NOT_WRITEABLE);
}

static bool InitLZO()
{
	_sl.bufsize = LZO_SIZE;
	_sl.buf = _sl.buf_ori = MallocT<byte>(LZO_SIZE);
	return true;
}

static void UninitLZO()
{
	free(_sl.buf_ori);
}

/*********************************************
 ******** START OF NOCOMP CODE (uncompressed)*
 *********************************************/
static size_t ReadNoComp()
{
	return fread(_sl.buf, 1, LZO_SIZE, _sl.fh);
}

static void WriteNoComp(size_t size)
{
	if (fwrite(_sl.buf, 1, size, _sl.fh) != size) SlError(STR_GAME_SAVELOAD_ERROR_FILE_NOT_WRITEABLE);
}

static bool InitNoComp()
{
	_sl.bufsize = LZO_SIZE;
	_sl.buf = _sl.buf_ori = MallocT<byte>(LZO_SIZE);
	return true;
}

static void UninitNoComp()
{
	free(_sl.buf_ori);
}

/********************************************
 ********** START OF MEMORY CODE (in ram)****
 ********************************************/

#include "table/sprites.h"
#include "gui.h"

struct ThreadedSave {
	uint count;
	byte ff_state;
	bool saveinprogress;
	CursorID cursor;
};

/* A maximum size of of 128K * 500 = 64.000KB savegames */
STATIC_OLD_POOL(Savegame, byte, 17, 500, NULL, NULL)
static ThreadedSave _ts;

static bool InitMem()
{
	_ts.count = 0;

	_Savegame_pool.CleanPool();
	_Savegame_pool.AddBlockToPool();

	/* A block from the pool is a contigious area of memory, so it is safe to write to it sequentially */
	_sl.bufsize = GetSavegamePoolSize();
	_sl.buf = GetSavegame(_ts.count);
	return true;
}

static void UnInitMem()
{
	_Savegame_pool.CleanPool();
}

static void WriteMem(size_t size)
{
	_ts.count += (uint)size;
	/* Allocate new block and new buffer-pointer */
	_Savegame_pool.AddBlockIfNeeded(_ts.count);
	_sl.buf = GetSavegame(_ts.count);
}

/********************************************
 ********** START OF ZLIB CODE **************
 ********************************************/

#if defined(WITH_ZLIB)
#include <zlib.h>

static z_stream _z;

static bool InitReadZlib()
{
	memset(&_z, 0, sizeof(_z));
	if (inflateInit(&_z) != Z_OK) return false;

	_sl.bufsize = 4096;
	_sl.buf = _sl.buf_ori = MallocT<byte>(4096 + 4096); // also contains fread buffer
	return true;
}

static size_t ReadZlib()
{
	int r;

	_z.next_out = _sl.buf;
	_z.avail_out = 4096;

	do {
		/* read more bytes from the file? */
		if (_z.avail_in == 0) {
			_z.avail_in = (uint)fread(_z.next_in = _sl.buf + 4096, 1, 4096, _sl.fh);
		}

		/* inflate the data */
		r = inflate(&_z, 0);
		if (r == Z_STREAM_END)
			break;

		if (r != Z_OK) SlError(STR_GAME_SAVELOAD_ERROR_BROKEN_INTERNAL_ERROR, "inflate() failed");
	} while (_z.avail_out);

	return 4096 - _z.avail_out;
}

static void UninitReadZlib()
{
	inflateEnd(&_z);
	free(_sl.buf_ori);
}

static bool InitWriteZlib()
{
	memset(&_z, 0, sizeof(_z));
	if (deflateInit(&_z, 6) != Z_OK) return false;

	_sl.bufsize = 4096;
	_sl.buf = _sl.buf_ori = MallocT<byte>(4096); // also contains fread buffer
	return true;
}

static void WriteZlibLoop(z_streamp z, byte *p, size_t len, int mode)
{
	byte buf[1024]; // output buffer
	int r;
	uint n;
	z->next_in = p;
	z->avail_in = (uInt)len;
	do {
		z->next_out = buf;
		z->avail_out = sizeof(buf);
		r = deflate(z, mode);
			/* bytes were emitted? */
		if ((n = sizeof(buf) - z->avail_out) != 0) {
			if (fwrite(buf, n, 1, _sl.fh) != 1) SlError(STR_GAME_SAVELOAD_ERROR_FILE_NOT_WRITEABLE);
		}
		if (r == Z_STREAM_END)
			break;
		if (r != Z_OK) SlError(STR_GAME_SAVELOAD_ERROR_BROKEN_INTERNAL_ERROR, "zlib returned error code");
	} while (z->avail_in || !z->avail_out);
}

static void WriteZlib(size_t len)
{
	WriteZlibLoop(&_z, _sl.buf, len, 0);
}

static void UninitWriteZlib()
{
	/* flush any pending output. */
	if (_sl.fh) WriteZlibLoop(&_z, NULL, 0, Z_FINISH);
	deflateEnd(&_z);
	free(_sl.buf_ori);
}

#endif /* WITH_ZLIB */

/*******************************************
 ************* END OF CODE *****************
 *******************************************/

/* these define the chunks */
extern const ChunkHandler _gamelog_chunk_handlers[];
extern const ChunkHandler _misc_chunk_handlers[];
extern const ChunkHandler _name_chunk_handlers[];
extern const ChunkHandler _cheat_chunk_handlers[] ;
extern const ChunkHandler _setting_chunk_handlers[];
extern const ChunkHandler _player_chunk_handlers[];
extern const ChunkHandler _engine_chunk_handlers[];
extern const ChunkHandler _veh_chunk_handlers[];
extern const ChunkHandler _waypoint_chunk_handlers[];
extern const ChunkHandler _depot_chunk_handlers[];
extern const ChunkHandler _order_chunk_handlers[];
extern const ChunkHandler _town_chunk_handlers[];
extern const ChunkHandler _sign_chunk_handlers[];
extern const ChunkHandler _station_chunk_handlers[];
extern const ChunkHandler _industry_chunk_handlers[];
extern const ChunkHandler _economy_chunk_handlers[];
extern const ChunkHandler _animated_tile_chunk_handlers[];
extern const ChunkHandler _newgrf_chunk_handlers[];
extern const ChunkHandler _group_chunk_handlers[];
extern const ChunkHandler _cargopacket_chunk_handlers[];
extern const ChunkHandler _autoreplace_chunk_handlers[];

static const ChunkHandler * const _chunk_handlers[] = {
	_gamelog_chunk_handlers,
	_misc_chunk_handlers,
	_name_chunk_handlers,
	_cheat_chunk_handlers,
	_setting_chunk_handlers,
	_veh_chunk_handlers,
	_waypoint_chunk_handlers,
	_depot_chunk_handlers,
	_order_chunk_handlers,
	_industry_chunk_handlers,
	_economy_chunk_handlers,
	_engine_chunk_handlers,
	_town_chunk_handlers,
	_sign_chunk_handlers,
	_station_chunk_handlers,
	_player_chunk_handlers,
	_animated_tile_chunk_handlers,
	_newgrf_chunk_handlers,
	_group_chunk_handlers,
	_cargopacket_chunk_handlers,
	_autoreplace_chunk_handlers,
	NULL,
};

/**
 * Pointers cannot be saved to a savegame, so this functions gets
 * the index of the item, and if not available, it hussles with
 * pointers (looks really bad :()
 * Remember that a NULL item has value 0, and all
 * indeces have +1, so vehicle 0 is saved as index 1.
 * @param obj The object that we want to get the index of
 * @param rt SLRefType type of the object the index is being sought of
 * @return Return the pointer converted to an index of the type pointed to
 */
static uint ReferenceToInt(const void *obj, SLRefType rt)
{
	if (obj == NULL) return 0;

	switch (rt) {
		case REF_VEHICLE_OLD: // Old vehicles we save as new onces
		case REF_VEHICLE:   return ((const  Vehicle*)obj)->index + 1;
		case REF_STATION:   return ((const  Station*)obj)->index + 1;
		case REF_TOWN:      return ((const     Town*)obj)->index + 1;
		case REF_ORDER:     return ((const    Order*)obj)->index + 1;
		case REF_ROADSTOPS: return ((const RoadStop*)obj)->index + 1;
		case REF_ENGINE_RENEWS: return ((const EngineRenew*)obj)->index + 1;
		case REF_CARGO_PACKET:  return ((const CargoPacket*)obj)->index + 1;
		default: NOT_REACHED();
	}

	return 0; // avoid compiler warning
}

/**
 * Pointers cannot be loaded from a savegame, so this function
 * gets the index from the savegame and returns the appropiate
 * pointer from the already loaded base.
 * Remember that an index of 0 is a NULL pointer so all indeces
 * are +1 so vehicle 0 is saved as 1.
 * @param index The index that is being converted to a pointer
 * @param rt SLRefType type of the object the pointer is sought of
 * @return Return the index converted to a pointer of any type
 */
static void *IntToReference(uint index, SLRefType rt)
{
	/* After version 4.3 REF_VEHICLE_OLD is saved as REF_VEHICLE,
	 * and should be loaded like that */
	if (rt == REF_VEHICLE_OLD && !CheckSavegameVersionOldStyle(4, 4)) {
		rt = REF_VEHICLE;
	}

	/* No need to look up NULL pointers, just return immediately */
	if (rt != REF_VEHICLE_OLD && index == 0) {
		return NULL;
	}

	index--; // correct for the NULL index

	switch (rt) {
		case REF_ORDER:
			if (_Order_pool.AddBlockIfNeeded(index)) return GetOrder(index);
			error("Orders: failed loading savegame: too many orders");

		case REF_VEHICLE:
			if (_Vehicle_pool.AddBlockIfNeeded(index)) return GetVehicle(index);
			error("Vehicles: failed loading savegame: too many vehicles");

		case REF_STATION:
			if (_Station_pool.AddBlockIfNeeded(index)) return GetStation(index);
			error("Stations: failed loading savegame: too many stations");

		case REF_TOWN:
			if (_Town_pool.AddBlockIfNeeded(index)) return GetTown(index);
			error("Towns: failed loading savegame: too many towns");

		case REF_ROADSTOPS:
			if (_RoadStop_pool.AddBlockIfNeeded(index)) return GetRoadStop(index);
			error("RoadStops: failed loading savegame: too many RoadStops");

		case REF_ENGINE_RENEWS:
			if (_EngineRenew_pool.AddBlockIfNeeded(index)) return GetEngineRenew(index);
			error("EngineRenews: failed loading savegame: too many EngineRenews");

		case REF_CARGO_PACKET:
			if (_CargoPacket_pool.AddBlockIfNeeded(index)) return GetCargoPacket(index);
			error("CargoPackets: failed loading savegame: too many Cargo packets");

		case REF_VEHICLE_OLD:
			/* Old vehicles were saved differently:
			 * invalid vehicle was 0xFFFF,
			 * and the index was not - 1.. correct for this */
			index++;
			if (index == INVALID_VEHICLE) return NULL;

			if (_Vehicle_pool.AddBlockIfNeeded(index)) return GetVehicle(index);
			error("Vehicles: failed loading savegame: too many vehicles");

		default: NOT_REACHED();
	}

	return NULL;
}

/** The format for a reader/writer type of a savegame */
struct SaveLoadFormat {
	const char *name;           ///< name of the compressor/decompressor (debug-only)
	uint32 tag;                 ///< the 4-letter tag by which it is identified in the savegame

	bool (*init_read)();        ///< function executed upon initalization of the loader
	ReaderProc *reader;         ///< function that loads the data from the file
	void (*uninit_read)();      ///< function executed when reading is finished

	bool (*init_write)();       ///< function executed upon intialization of the saver
	WriterProc *writer;         ///< function that saves the data to the file
	void (*uninit_write)();     ///< function executed when writing is done
};

static const SaveLoadFormat _saveload_formats[] = {
	{"memory", 0,                NULL,         NULL,       NULL,           InitMem,       WriteMem,    UnInitMem},
	{"lzo",    TO_BE32X('OTTD'), InitLZO,      ReadLZO,    UninitLZO,      InitLZO,       WriteLZO,    UninitLZO},
	{"none",   TO_BE32X('OTTN'), InitNoComp,   ReadNoComp, UninitNoComp,   InitNoComp,    WriteNoComp, UninitNoComp},
#if defined(WITH_ZLIB)
	{"zlib",   TO_BE32X('OTTZ'), InitReadZlib, ReadZlib,   UninitReadZlib, InitWriteZlib, WriteZlib,   UninitWriteZlib},
#else
	{"zlib",   TO_BE32X('OTTZ'), NULL,         NULL,       NULL,           NULL,          NULL,        NULL},
#endif
};

/**
 * Return the savegameformat of the game. Whether it was create with ZLIB compression
 * uncompressed, or another type
 * @param s Name of the savegame format. If NULL it picks the first available one
 * @return Pointer to SaveLoadFormat struct giving all characteristics of this type of savegame
 */
static const SaveLoadFormat *GetSavegameFormat(const char *s)
{
	const SaveLoadFormat *def = endof(_saveload_formats) - 1;

	/* find default savegame format, the highest one with which files can be written */
	while (!def->init_write) def--;

	if (s != NULL && s[0] != '\0') {
		const SaveLoadFormat *slf;
		for (slf = &_saveload_formats[0]; slf != endof(_saveload_formats); slf++) {
			if (slf->init_write != NULL && strcmp(s, slf->name) == 0)
				return slf;
		}

		ShowInfoF("Savegame format '%s' is not available. Reverting to '%s'.", s, def->name);
	}
	return def;
}

/* actual loader/saver function */
void InitializeGame(uint size_x, uint size_y, bool reset_date);
extern bool AfterLoadGame();
extern void SaveViewportBeforeSaveGame();
extern bool LoadOldSaveGame(const char *file);

/** Small helper function to close the to be loaded savegame an signal error */
static inline SaveOrLoadResult AbortSaveLoad()
{
	if (_sl.fh != NULL) fclose(_sl.fh);

	_sl.fh = NULL;
	return SL_ERROR;
}

/** Update the gui accordingly when starting saving
 * and set locks on saveload. Also turn off fast-forward cause with that
 * saving takes Aaaaages */
static void SaveFileStart()
{
	_ts.ff_state = _fast_forward;
	_fast_forward = 0;
	if (_cursor.sprite == SPR_CURSOR_MOUSE) SetMouseCursor(SPR_CURSOR_ZZZ, PAL_NONE);

	InvalidateWindowData(WC_STATUS_BAR, 0, SBI_SAVELOAD_START);
	_ts.saveinprogress = true;
}

/** Update the gui accordingly when saving is done and release locks
 * on saveload */
static void SaveFileDone()
{
	_fast_forward = _ts.ff_state;
	if (_cursor.sprite == SPR_CURSOR_ZZZ) SetMouseCursor(SPR_CURSOR_MOUSE, PAL_NONE);

	InvalidateWindowData(WC_STATUS_BAR, 0, SBI_SAVELOAD_FINISH);
	_ts.saveinprogress = false;
}

/** Set the error message from outside of the actual loading/saving of the game (AfterLoadGame and friends) */
void SetSaveLoadError(StringID str)
{
	_sl.error_str = str;
}

/** Get the string representation of the error message */
const char *GetSaveLoadErrorString()
{
	SetDParam(0, _sl.error_str);
	SetDParamStr(1, _sl.extra_msg);

	static char err_str[512];
	GetString(err_str, _sl.save ? STR_4007_GAME_SAVE_FAILED : STR_4009_GAME_LOAD_FAILED, lastof(err_str));
	return err_str;
}

/** Show a gui message when saving has failed */
static void SaveFileError()
{
	SetDParamStr(0, GetSaveLoadErrorString());
	ShowErrorMessage(STR_012D, STR_NULL, 0, 0);
	SaveFileDone();
}

/** We have written the whole game into memory, _Savegame_pool, now find
 * and appropiate compressor and start writing to file.
 */
static SaveOrLoadResult SaveFileToDisk(bool threaded)
{
	const SaveLoadFormat *fmt;
	uint32 hdr[2];

	_sl.excpt_uninit = NULL;
	try {
		fmt = GetSavegameFormat(_savegame_format);

		/* We have written our stuff to memory, now write it to file! */
		hdr[0] = fmt->tag;
		hdr[1] = TO_BE32(SAVEGAME_VERSION << 16);
		if (fwrite(hdr, sizeof(hdr), 1, _sl.fh) != 1) SlError(STR_GAME_SAVELOAD_ERROR_FILE_NOT_WRITEABLE);

		if (!fmt->init_write()) SlError(STR_GAME_SAVELOAD_ERROR_BROKEN_INTERNAL_ERROR, "cannot initialize compressor");

		{
			uint i;
			uint count = 1 << Savegame_POOL_BLOCK_SIZE_BITS;

			if (_ts.count != _sl.offs_base) SlError(STR_GAME_SAVELOAD_ERROR_BROKEN_SAVEGAME, "Unexpected size of chunk");
			for (i = 0; i != _Savegame_pool.GetBlockCount() - 1; i++) {
				_sl.buf = _Savegame_pool.blocks[i];
				fmt->writer(count);
			}

			/* The last block is (almost) always not fully filled, so only write away
			 * as much data as it is in there */
			_sl.buf = _Savegame_pool.blocks[i];
			fmt->writer(_ts.count - (i * count));
		}

		fmt->uninit_write();
		if (_ts.count != _sl.offs_base) SlError(STR_GAME_SAVELOAD_ERROR_BROKEN_SAVEGAME, "Unexpected size of chunk");
		GetSavegameFormat("memory")->uninit_write(); // clean the memorypool
		fclose(_sl.fh);

		if (threaded) SetAsyncSaveFinish(SaveFileDone);

		return SL_OK;
	}
	catch (...) {
		AbortSaveLoad();
		if (_sl.excpt_uninit != NULL) _sl.excpt_uninit();

		ShowInfo(GetSaveLoadErrorString());
		DEBUG(sl, 0, GetSaveLoadErrorString());

		if (threaded) {
			SetAsyncSaveFinish(SaveFileError);
		} else {
			SaveFileError();
		}
		return SL_ERROR;
	}
}

static void SaveFileToDiskThread(void *arg)
{
	SaveFileToDisk(true);
}

void WaitTillSaved()
{
	if (_save_thread == NULL) return;

	_save_thread->Join();
	delete _save_thread;
	_save_thread = NULL;
}

/**
 * Main Save or Load function where the high-level saveload functions are
 * handled. It opens the savegame, selects format and checks versions
 * @param filename The name of the savegame being created/loaded
 * @param mode Save or load. Load can also be a TTD(Patch) game. Use SL_LOAD, SL_OLD_LOAD or SL_SAVE
 * @return Return the results of the action. SL_OK, SL_ERROR or SL_REINIT ("unload" the game)
 */
SaveOrLoadResult SaveOrLoad(const char *filename, int mode, Subdirectory sb)
{
	uint32 hdr[2];
	const SaveLoadFormat *fmt;

	/* An instance of saving is already active, so don't go saving again */
	if (_ts.saveinprogress && mode == SL_SAVE) {
		/* if not an autosave, but a user action, show error message */
		if (!_do_autosave) ShowErrorMessage(INVALID_STRING_ID, STR_SAVE_STILL_IN_PROGRESS, 0, 0);
		return SL_OK;
	}
	WaitTillSaved();

	_next_offs = 0;

	/* Load a TTDLX or TTDPatch game */
	if (mode == SL_OLD_LOAD) {
		InitializeGame(256, 256, true); // set a mapsize of 256x256 for TTDPatch games or it might get confused
		GamelogReset();
		if (!LoadOldSaveGame(filename)) return SL_REINIT;
		_sl_version = 0;
		_sl_minor_version = 0;
		GamelogStartAction(GLAT_LOAD);
		if (!AfterLoadGame()) {
			GamelogStopAction();
			return SL_REINIT;
		}
		GamelogStopAction();
		return SL_OK;
	}

	_sl.excpt_uninit = NULL;
	try {
		_sl.fh = (mode == SL_SAVE) ? FioFOpenFile(filename, "wb", sb) : FioFOpenFile(filename, "rb", sb);

		/* Make it a little easier to load savegames from the console */
		if (_sl.fh == NULL && mode == SL_LOAD) _sl.fh = FioFOpenFile(filename, "rb", SAVE_DIR);
		if (_sl.fh == NULL && mode == SL_LOAD) _sl.fh = FioFOpenFile(filename, "rb", BASE_DIR);

		if (_sl.fh == NULL) {
			SlError(mode == SL_SAVE ? STR_GAME_SAVELOAD_ERROR_FILE_NOT_WRITEABLE : STR_GAME_SAVELOAD_ERROR_FILE_NOT_READABLE);
		}

		_sl.bufe = _sl.bufp = NULL;
		_sl.offs_base = 0;
		_sl.save = (mode != 0);
		_sl.chs = _chunk_handlers;

		/* General tactic is to first save the game to memory, then use an available writer
		 * to write it to file, either in threaded mode if possible, or single-threaded */
		if (mode == SL_SAVE) { /* SAVE game */
			fmt = GetSavegameFormat("memory"); // write to memory

			_sl.write_bytes = fmt->writer;
			_sl.excpt_uninit = fmt->uninit_write;
			if (!fmt->init_write()) {
				DEBUG(sl, 0, "Initializing writer '%s' failed.", fmt->name);
				return AbortSaveLoad();
			}

			_sl_version = SAVEGAME_VERSION;

			SaveViewportBeforeSaveGame();
			SlSaveChunks();
			SlWriteFill(); // flush the save buffer

			SaveFileStart();
			if (_network_server ||
						(_save_thread = ThreadObject::New(&SaveFileToDiskThread, NULL)) == NULL) {
				if (!_network_server) DEBUG(sl, 1, "Cannot create savegame thread, reverting to single-threaded mode...");

				SaveOrLoadResult result = SaveFileToDisk(false);
				SaveFileDone();

				return result;
			}
		} else { /* LOAD game */
			assert(mode == SL_LOAD);
			DebugDumpCommands("ddc:load:%s\n", filename);

			if (fread(hdr, sizeof(hdr), 1, _sl.fh) != 1) SlError(STR_GAME_SAVELOAD_ERROR_FILE_NOT_READABLE);

			/* see if we have any loader for this type. */
			for (fmt = _saveload_formats; ; fmt++) {
				/* No loader found, treat as version 0 and use LZO format */
				if (fmt == endof(_saveload_formats)) {
					DEBUG(sl, 0, "Unknown savegame type, trying to load it as the buggy format");
	#if defined(WINCE)
					/* Of course some system had not to support rewind ;) */
					fseek(_sl.fh, 0L, SEEK_SET);
					clearerr(_sl.fh);
	#else
					rewind(_sl.fh);
	#endif
					_sl_version = 0;
					_sl_minor_version = 0;
					fmt = _saveload_formats + 1; // LZO
					break;
				}

				if (fmt->tag == hdr[0]) {
					/* check version number */
					_sl_version = TO_BE32(hdr[1]) >> 16;
					/* Minor is not used anymore from version 18.0, but it is still needed
					 * in versions before that (4 cases) which can't be removed easy.
					 * Therefor it is loaded, but never saved (or, it saves a 0 in any scenario).
					 * So never EVER use this minor version again. -- TrueLight -- 22-11-2005 */
					_sl_minor_version = (TO_BE32(hdr[1]) >> 8) & 0xFF;

					DEBUG(sl, 1, "Loading savegame version %d", _sl_version);

					/* Is the version higher than the current? */
					if (_sl_version > SAVEGAME_VERSION) SlError(STR_GAME_SAVELOAD_ERROR_TOO_NEW_SAVEGAME);
					break;
				}
			}

			_sl.read_bytes = fmt->reader;
			_sl.excpt_uninit = fmt->uninit_read;

			/* loader for this savegame type is not implemented? */
			if (fmt->init_read == NULL) {
				char err_str[64];
				snprintf(err_str, lengthof(err_str), "Loader for '%s' is not available.", fmt->name);
				SlError(STR_GAME_SAVELOAD_ERROR_BROKEN_INTERNAL_ERROR, err_str);
			}

			if (!fmt->init_read()) {
				char err_str[64];
				snprintf(err_str, lengthof(err_str), "Initializing loader '%s' failed", fmt->name);
				SlError(STR_GAME_SAVELOAD_ERROR_BROKEN_INTERNAL_ERROR, err_str);
			}

			/* Old maps were hardcoded to 256x256 and thus did not contain
			 * any mapsize information. Pre-initialize to 256x256 to not to
			 * confuse old games */
			InitializeGame(256, 256, true);

			GamelogReset();

			SlLoadChunks();
			fmt->uninit_read();
			fclose(_sl.fh);

			GamelogStartAction(GLAT_LOAD);

			_savegame_type = SGT_OTTD;

			/* After loading fix up savegame for any internal changes that
			 * might've occured since then. If it fails, load back the old game */
			if (!AfterLoadGame()) {
				GamelogStopAction();
				return SL_REINIT;
			}

			GamelogStopAction();
		}

		return SL_OK;
	}
	catch (...) {
		AbortSaveLoad();

		/* deinitialize compressor. */
		if (_sl.excpt_uninit != NULL) _sl.excpt_uninit();

		/* Skip the "color" character */
		ShowInfoF(GetSaveLoadErrorString() + 3);

		/* A saver/loader exception!! reinitialize all variables to prevent crash! */
		return (mode == SL_LOAD) ? SL_REINIT : SL_ERROR;
	}
}

/** Do a save when exiting the game (patch option) _settings_client.gui.autosave_on_exit */
void DoExitSave()
{
	SaveOrLoad("exit.sav", SL_SAVE, AUTOSAVE_DIR);
}

#if 0
/**
 * Function to get the type of the savegame by looking at the file header.
 * NOTICE: Not used right now, but could be used if extensions of savegames are garbled
 * @param file Savegame to be checked
 * @return SL_OLD_LOAD or SL_LOAD of the file
 */
int GetSavegameType(char *file)
{
	const SaveLoadFormat *fmt;
	uint32 hdr;
	FILE *f;
	int mode = SL_OLD_LOAD;

	f = fopen(file, "rb");
	if (fread(&hdr, sizeof(hdr), 1, f) != 1) {
		DEBUG(sl, 0, "Savegame is obsolete or invalid format");
		mode = SL_LOAD; // don't try to get filename, just show name as it is written
	} else {
		/* see if we have any loader for this type. */
		for (fmt = _saveload_formats; fmt != endof(_saveload_formats); fmt++) {
			if (fmt->tag == hdr) {
				mode = SL_LOAD; // new type of savegame
				break;
			}
		}
	}

	fclose(f);
	return mode;
}
#endif