summaryrefslogtreecommitdiff
path: root/src/saveload/oldloader.cpp
blob: 74a1466da6efd4f816456cada7520c7b42d2c894 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
/*
 * 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 "../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>

#include "../safeguards.h"

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 well if you have many zeros behind each other */

	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)
{
	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, (uint)(size_t)chunk->ptr + _bump_assert_value);
						if (ls->total_read != (size_t)chunk->ptr + _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 nullptr, we are just skipping data */
				if (base == nullptr && chunk->ptr == nullptr) continue;

				/* Chunk refers to a struct member, get address in base. */
				if (chunk->ptr == nullptr) ptr = (byte *)chunk->offset(base);

				/* 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 != nullptr) 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 null-terminated in savegame, but it's better to be sure
	StrMakeValidInPlace(temp, last);

	return ret;
}

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

	SavegameType type = SGT_TTO;

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

	if (title != nullptr) {
		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;
		}
		strecpy(title, temp, last);
	}

	return type;
}

typedef bool LoadOldMainProc(LoadgameState *ls);

bool LoadOldSaveGame(const std::string &file)
{
	LoadgameState ls;

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

	InitLoading(&ls);

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

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

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

	LoadOldMainProc *proc = nullptr;

	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 != nullptr && 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 = PM_PAUSED_SAVELOAD;

	return true;
}

void GetOldSaveGameName(const std::string &file, char *title, const char *last)
{
	FILE *f = FioFOpenFile(file, "rb", NO_DIRECTORY);

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

	DetermineOldSavegameType(f, title, last);

	fclose(f);
}