Files @ r15577:a61e44bed2f3
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Location: cpp/openttd-patchpack/source/src/saveload/oldloader.cpp

rubidium
(svn r20247) -Fix: when it is known the loading an old savegame is going to fail, bail out immediately (using an exception) instead of going on until e.g. the expected number of byte is read
/* $Id$ */

/*
 * This file is part of OpenTTD.
 * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
 * OpenTTD 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 General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
 */

/** @file oldloader.cpp Functions for handling of TTO/TTD/TTDP savegames. */

#include "../stdafx.h"
#include "../openttd.h"
#include "../debug.h"
#include "../strings_type.h"
#include "../string_func.h"
#include "../settings_type.h"
#include "../fileio_func.h"

#include "table/strings.h"

#include "saveload_internal.h"
#include "oldloader.h"

#include <exception>

static const int TTO_HEADER_SIZE = 41;
static const int TTD_HEADER_SIZE = 49;

uint32 _bump_assert_value;

static inline OldChunkType GetOldChunkType(OldChunkType type)     {return (OldChunkType)GB(type, 0, 4);}
static inline OldChunkType GetOldChunkVarType(OldChunkType type)  {return (OldChunkType)(GB(type, 8, 8) << 8);}
static inline OldChunkType GetOldChunkFileType(OldChunkType type) {return (OldChunkType)(GB(type, 16, 8) << 16);}

static inline byte CalcOldVarLen(OldChunkType type)
{
	static const byte type_mem_size[] = {0, 1, 1, 2, 2, 4, 4, 8};
	byte length = GB(type, 8, 8);
	assert(length != 0 && length < lengthof(type_mem_size));
	return type_mem_size[length];
}

/**
 *
 * Reads a byte from a file (do not call yourself, use ReadByte())
 *
 */
static byte ReadByteFromFile(LoadgameState *ls)
{
	/* To avoid slow reads, we read BUFFER_SIZE of bytes per time
	and just return a byte per time */
	if (ls->buffer_cur >= ls->buffer_count) {

		/* Read some new bytes from the file */
		int count = (int)fread(ls->buffer, 1, BUFFER_SIZE, ls->file);

		/* We tried to read, but there is nothing in the file anymore.. */
		if (count == 0) {
			DEBUG(oldloader, 0, "Read past end of file, loading failed");
			throw std::exception();
		}

		ls->buffer_count = count;
		ls->buffer_cur   = 0;
	}

	return ls->buffer[ls->buffer_cur++];
}

/**
 *
 * Reads a byte from the buffer and decompress if needed
 *
 */
byte ReadByte(LoadgameState *ls)
{
	/* Old savegames have a nice compression algorithm (RLE)
	which means that we have a chunk, which starts with a length
	byte. If that byte is negative, we have to repeat the next byte
	that many times ( + 1). Else, we need to read that amount of bytes.
	Works pretty good if you have many zero's behind eachother */

	if (ls->chunk_size == 0) {
		/* Read new chunk */
		int8 new_byte = ReadByteFromFile(ls);

		if (new_byte < 0) {
			/* Repeat next char for new_byte times */
			ls->decoding    = true;
			ls->decode_char = ReadByteFromFile(ls);
			ls->chunk_size  = -new_byte + 1;
		} else {
			ls->decoding    = false;
			ls->chunk_size  = new_byte + 1;
		}
	}

	ls->total_read++;
	ls->chunk_size--;

	return ls->decoding ? ls->decode_char : ReadByteFromFile(ls);
}

/**
 *
 * Loads a chunk from the old savegame
 *
 */
bool LoadChunk(LoadgameState *ls, void *base, const OldChunks *chunks)
{
	byte *base_ptr = (byte*)base;

	for (const OldChunks *chunk = chunks; chunk->type != OC_END; chunk++) {
		if (((chunk->type & OC_TTD) && _savegame_type == SGT_TTO) ||
				((chunk->type & OC_TTO) && _savegame_type != SGT_TTO)) {
			/* TTD(P)-only chunk, but TTO savegame || TTO-only chunk, but TTD/TTDP savegame */
			continue;
		}

		byte *ptr = (byte*)chunk->ptr;
		if (chunk->type & OC_DEREFERENCE_POINTER) ptr = *(byte**)ptr;

		for (uint i = 0; i < chunk->amount; i++) {
			/* Handle simple types */
			if (GetOldChunkType(chunk->type) != 0) {
				switch (GetOldChunkType(chunk->type)) {
					/* Just read the byte and forget about it */
					case OC_NULL: ReadByte(ls); break;

					case OC_CHUNK:
						/* Call function, with 'i' as parameter to tell which item we
						 * are going to read */
						if (!chunk->proc(ls, i)) return false;
						break;

					case OC_ASSERT:
						DEBUG(oldloader, 4, "Assert point: 0x%X / 0x%X", ls->total_read, chunk->offset + _bump_assert_value);
						if (ls->total_read != chunk->offset + _bump_assert_value) throw std::exception();
					default: break;
				}
			} else {
				uint64 res = 0;

				/* Reading from the file: bits 16 to 23 have the FILE type */
				switch (GetOldChunkFileType(chunk->type)) {
					case OC_FILE_I8:  res = (int8)ReadByte(ls); break;
					case OC_FILE_U8:  res = ReadByte(ls); break;
					case OC_FILE_I16: res = (int16)ReadUint16(ls); break;
					case OC_FILE_U16: res = ReadUint16(ls); break;
					case OC_FILE_I32: res = (int32)ReadUint32(ls); break;
					case OC_FILE_U32: res = ReadUint32(ls); break;
					default: NOT_REACHED();
				}

				/* When both pointers are NULL, we are just skipping data */
				if (base_ptr == NULL && chunk->ptr == NULL) continue;

				/* Writing to the var: bits 8 to 15 have the VAR type */
				if (chunk->ptr == NULL) ptr = base_ptr + chunk->offset;

				/* Write the data */
				switch (GetOldChunkVarType(chunk->type)) {
					case OC_VAR_I8: *(int8  *)ptr = GB(res, 0, 8); break;
					case OC_VAR_U8: *(uint8 *)ptr = GB(res, 0, 8); break;
					case OC_VAR_I16:*(int16 *)ptr = GB(res, 0, 16); break;
					case OC_VAR_U16:*(uint16*)ptr = GB(res, 0, 16); break;
					case OC_VAR_I32:*(int32 *)ptr = res; break;
					case OC_VAR_U32:*(uint32*)ptr = res; break;
					case OC_VAR_I64:*(int64 *)ptr = res; break;
					case OC_VAR_U64:*(uint64*)ptr = res; break;
					default: NOT_REACHED();
				}

				/* Increase pointer base for arrays when looping */
				if (chunk->amount > 1 && chunk->ptr != NULL) ptr += CalcOldVarLen(chunk->type);
			}
		}
	}

	return true;
}

/**
 *
 * Initialize some data before reading
 *
 */
static void InitLoading(LoadgameState *ls)
{
	ls->chunk_size   = 0;
	ls->total_read   = 0;

	ls->decoding     = false;
	ls->decode_char  = 0;

	ls->buffer_cur   = 0;
	ls->buffer_count = 0;
	memset(ls->buffer, 0, BUFFER_SIZE);

	_bump_assert_value = 0;

	_settings_game.construction.freeform_edges = false; // disable so we can convert map array (SetTileType is still used)
}

/**
 * Verifies the title has a valid checksum
 * @param title title and checksum
 * @param len   the length of the title to read/checksum
 * @return true iff the title is valid
 * @note the title (incl. checksum) has to be at least 41/49 (HEADER_SIZE) bytes long!
 */
static bool VerifyOldNameChecksum(char *title, uint len)
{
	uint16 sum = 0;
	for (uint i = 0; i < len - 2; i++) {
		sum += title[i];
		sum = ROL(sum, 1);
	}

	sum ^= 0xAAAA; // computed checksum

	uint16 sum2 = title[len - 2]; // checksum in file
	SB(sum2, 8, 8, title[len - 1]);

	return sum == sum2;
}

static inline bool CheckOldSavegameType(FILE *f, char *temp, const char *last, uint len)
{
	assert(last - temp + 1 >= (int)len);

	if (fread(temp, 1, len, f) != len) {
		temp[0] = '\0'; // if reading failed, make the name empty
		return false;
	}

	bool ret = VerifyOldNameChecksum(temp, len);
	temp[len - 2] = '\0'; // name is nul-terminated in savegame, but it's better to be sure
	str_validate(temp, last);

	return ret;
}

static SavegameType DetermineOldSavegameType(FILE *f, char *title, const char *last)
{
	assert_compile(TTD_HEADER_SIZE >= TTO_HEADER_SIZE);
	char temp[TTD_HEADER_SIZE];

	SavegameType type = SGT_TTO;

	/* Can't fseek to 0 as in tar files that is not correct */
	long pos = ftell(f);
	if (!CheckOldSavegameType(f, temp, lastof(temp), TTO_HEADER_SIZE)) {
		type = SGT_TTD;
		fseek(f, pos, SEEK_SET);
		if (!CheckOldSavegameType(f, temp, lastof(temp), TTD_HEADER_SIZE)) {
			type = SGT_INVALID;
		}
	}

	if (title != NULL) {
		switch (type) {
			case SGT_TTO: title = strecpy(title, "(TTO) ", last);    break;
			case SGT_TTD: title = strecpy(title, "(TTD) ", last);    break;
			default:      title = strecpy(title, "(broken) ", last); break;
		}
		title = strecpy(title, temp, last);
	}

	return type;
}

typedef bool LoadOldMainProc(LoadgameState *ls);

bool LoadOldSaveGame(const char *file)
{
	LoadgameState ls;

	DEBUG(oldloader, 3, "Trying to load a TTD(Patch) savegame");

	InitLoading(&ls);

	/* Open file */
	ls.file = FioFOpenFile(file, "rb");

	if (ls.file == NULL) {
		DEBUG(oldloader, 0, "Cannot open file '%s'", file);
		return false;
	}

	SavegameType type = DetermineOldSavegameType(ls.file, NULL, NULL);

	LoadOldMainProc *proc = NULL;

	switch (type) {
		case SGT_TTO: proc = &LoadTTOMain; break;
		case SGT_TTD: proc = &LoadTTDMain; break;
		default: break;
	}

	_savegame_type = type;

	bool game_loaded;
	try {
		game_loaded = proc != NULL && proc(&ls);
	} catch (...) {
		game_loaded = false;
	}

	if (!game_loaded) {
		SetSaveLoadError(STR_GAME_SAVELOAD_ERROR_DATA_INTEGRITY_CHECK_FAILED);
		fclose(ls.file);
		return false;
	}

	_pause_mode = 2;

	return true;
}

void GetOldSaveGameName(const char *file, char *title, const char *last)
{
	FILE *f = FioFOpenFile(file, "rb");

	if (f == NULL) {
		*title = '\0';
		return;
	}

	DetermineOldSavegameType(f, title, last);

	fclose(f);
}