BackupData.cpp revision 436344ae12c819f58306ceb94241a266141e1218
1/* 2 * Copyright (C) 2009 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17#define LOG_TAG "backup_data" 18 19#include <utils/BackupHelpers.h> 20#include <utils/ByteOrder.h> 21 22#include <stdio.h> 23#include <unistd.h> 24 25#include <cutils/log.h> 26 27namespace android { 28 29/* 30 * File Format (v1): 31 * 32 * All ints are stored little-endian. 33 * 34 * - An app_header_v1 struct. 35 * - The name of the package, utf-8, null terminated, padded to 4-byte boundary. 36 * - A sequence of zero or more key/value paires (entities), each with 37 * - A entity_header_v1 struct 38 * - The key, utf-8, null terminated, padded to 4-byte boundary. 39 * - The value, padded to 4 byte boundary 40 */ 41 42const static int ROUND_UP[4] = { 0, 3, 2, 1 }; 43 44static inline size_t 45round_up(size_t n) 46{ 47 return n + ROUND_UP[n % 4]; 48} 49 50static inline size_t 51padding_extra(size_t n) 52{ 53 return ROUND_UP[n % 4]; 54} 55 56BackupDataWriter::BackupDataWriter(int fd) 57 :m_fd(fd), 58 m_status(NO_ERROR), 59 m_pos(0), 60 m_entityCount(0) 61{ 62} 63 64BackupDataWriter::~BackupDataWriter() 65{ 66} 67 68// Pad out anything they've previously written to the next 4 byte boundary. 69status_t 70BackupDataWriter::write_padding_for(int n) 71{ 72 ssize_t amt; 73 ssize_t paddingSize; 74 75 paddingSize = padding_extra(n); 76 if (paddingSize > 0) { 77 uint32_t padding = 0xbcbcbcbc; 78 amt = write(m_fd, &padding, paddingSize); 79 if (amt != paddingSize) { 80 m_status = errno; 81 return m_status; 82 } 83 m_pos += amt; 84 } 85 return NO_ERROR; 86} 87 88status_t 89BackupDataWriter::WriteEntityHeader(const String8& key, size_t dataSize) 90{ 91 if (m_status != NO_ERROR) { 92 return m_status; 93 } 94 95 ssize_t amt; 96 97 amt = write_padding_for(m_pos); 98 if (amt != 0) { 99 return amt; 100 } 101 102 String8 k; 103 if (m_keyPrefix.length() > 0) { 104 k = m_keyPrefix; 105 k += ":"; 106 k += key; 107 } else { 108 k = key; 109 } 110 if (false) { 111 LOGD("Writing entity: prefix='%s' key='%s' dataSize=%d", m_keyPrefix.string(), key.string(), 112 dataSize); 113 } 114 115 entity_header_v1 header; 116 ssize_t keyLen; 117 118 keyLen = k.length(); 119 120 header.type = tolel(BACKUP_HEADER_ENTITY_V1); 121 header.keyLen = tolel(keyLen); 122 header.dataSize = tolel(dataSize); 123 124 amt = write(m_fd, &header, sizeof(entity_header_v1)); 125 if (amt != sizeof(entity_header_v1)) { 126 m_status = errno; 127 return m_status; 128 } 129 m_pos += amt; 130 131 amt = write(m_fd, k.string(), keyLen+1); 132 if (amt != keyLen+1) { 133 m_status = errno; 134 return m_status; 135 } 136 m_pos += amt; 137 138 amt = write_padding_for(keyLen+1); 139 140 m_entityCount++; 141 142 return amt; 143} 144 145status_t 146BackupDataWriter::WriteEntityData(const void* data, size_t size) 147{ 148 if (m_status != NO_ERROR) { 149 return m_status; 150 } 151 152 // We don't write padding here, because they're allowed to call this several 153 // times with smaller buffers. We write it at the end of WriteEntityHeader 154 // instead. 155 ssize_t amt = write(m_fd, data, size); 156 if (amt != (ssize_t)size) { 157 m_status = errno; 158 return m_status; 159 } 160 m_pos += amt; 161 return NO_ERROR; 162} 163 164void 165BackupDataWriter::SetKeyPrefix(const String8& keyPrefix) 166{ 167 m_keyPrefix = keyPrefix; 168} 169 170 171BackupDataReader::BackupDataReader(int fd) 172 :m_fd(fd), 173 m_done(false), 174 m_status(NO_ERROR), 175 m_pos(0), 176 m_entityCount(0) 177{ 178 memset(&m_header, 0, sizeof(m_header)); 179} 180 181BackupDataReader::~BackupDataReader() 182{ 183} 184 185status_t 186BackupDataReader::Status() 187{ 188 return m_status; 189} 190 191#define CHECK_SIZE(actual, expected) \ 192 do { \ 193 if ((actual) != (expected)) { \ 194 if ((actual) == 0) { \ 195 m_status = EIO; \ 196 m_done = true; \ 197 } else { \ 198 m_status = errno; \ 199 LOGD("CHECK_SIZE(a=%ld e=%ld) failed at line %d m_status='%s'", \ 200 long(actual), long(expected), __LINE__, strerror(m_status)); \ 201 } \ 202 return m_status; \ 203 } \ 204 } while(0) 205#define SKIP_PADDING() \ 206 do { \ 207 status_t err = skip_padding(); \ 208 if (err != NO_ERROR) { \ 209 LOGD("SKIP_PADDING FAILED at line %d", __LINE__); \ 210 m_status = err; \ 211 return err; \ 212 } \ 213 } while(0) 214 215status_t 216BackupDataReader::ReadNextHeader(bool* done, int* type) 217{ 218 *done = m_done; 219 if (m_status != NO_ERROR) { 220 return m_status; 221 } 222 223 int amt; 224 225 amt = skip_padding(); 226 if (amt == EIO) { 227 *done = m_done = true; 228 return NO_ERROR; 229 } 230 else if (amt != NO_ERROR) { 231 return amt; 232 } 233 amt = read(m_fd, &m_header, sizeof(m_header)); 234 *done = m_done = (amt == 0); 235 if (*done) { 236 return NO_ERROR; 237 } 238 CHECK_SIZE(amt, sizeof(m_header)); 239 m_pos += sizeof(m_header); 240 if (type) { 241 *type = m_header.type; 242 } 243 244 // validate and fix up the fields. 245 m_header.type = fromlel(m_header.type); 246 switch (m_header.type) 247 { 248 case BACKUP_HEADER_ENTITY_V1: 249 { 250 m_header.entity.keyLen = fromlel(m_header.entity.keyLen); 251 if (m_header.entity.keyLen <= 0) { 252 LOGD("Entity header at %d has keyLen<=0: 0x%08x\n", (int)m_pos, 253 (int)m_header.entity.keyLen); 254 m_status = EINVAL; 255 } 256 m_header.entity.dataSize = fromlel(m_header.entity.dataSize); 257 m_entityCount++; 258 259 // read the rest of the header (filename) 260 size_t size = m_header.entity.keyLen; 261 char* buf = m_key.lockBuffer(size); 262 if (buf == NULL) { 263 m_status = ENOMEM; 264 return m_status; 265 } 266 int amt = read(m_fd, buf, size+1); 267 CHECK_SIZE(amt, (int)size+1); 268 m_key.unlockBuffer(size); 269 m_pos += size+1; 270 SKIP_PADDING(); 271 m_dataEndPos = m_pos + m_header.entity.dataSize; 272 273 break; 274 } 275 default: 276 LOGD("Chunk header at %d has invalid type: 0x%08x", (int)m_pos, (int)m_header.type); 277 m_status = EINVAL; 278 } 279 280 return m_status; 281} 282 283bool 284BackupDataReader::HasEntities() 285{ 286 return m_status == NO_ERROR && m_header.type == BACKUP_HEADER_ENTITY_V1; 287} 288 289status_t 290BackupDataReader::ReadEntityHeader(String8* key, size_t* dataSize) 291{ 292 if (m_status != NO_ERROR) { 293 return m_status; 294 } 295 if (m_header.type != BACKUP_HEADER_ENTITY_V1) { 296 return EINVAL; 297 } 298 *key = m_key; 299 *dataSize = m_header.entity.dataSize; 300 return NO_ERROR; 301} 302 303status_t 304BackupDataReader::SkipEntityData() 305{ 306 if (m_status != NO_ERROR) { 307 return m_status; 308 } 309 if (m_header.type != BACKUP_HEADER_ENTITY_V1) { 310 return EINVAL; 311 } 312 if (m_header.entity.dataSize > 0) { 313 int pos = lseek(m_fd, m_dataEndPos, SEEK_SET); 314 if (pos == -1) { 315 return errno; 316 } 317 } 318 SKIP_PADDING(); 319 return NO_ERROR; 320} 321 322ssize_t 323BackupDataReader::ReadEntityData(void* data, size_t size) 324{ 325 if (m_status != NO_ERROR) { 326 return -1; 327 } 328 int remaining = m_dataEndPos - m_pos; 329 //LOGD("ReadEntityData size=%d m_pos=0x%x m_dataEndPos=0x%x remaining=%d\n", 330 // size, m_pos, m_dataEndPos, remaining); 331 if (remaining <= 0) { 332 return 0; 333 } 334 if (((int)size) > remaining) { 335 size = remaining; 336 } 337 //LOGD(" reading %d bytes", size); 338 int amt = read(m_fd, data, size); 339 if (amt < 0) { 340 m_status = errno; 341 return -1; 342 } 343 if (amt == 0) { 344 m_status = EIO; 345 m_done = true; 346 } 347 m_pos += amt; 348 return amt; 349} 350 351status_t 352BackupDataReader::skip_padding() 353{ 354 ssize_t amt; 355 ssize_t paddingSize; 356 357 paddingSize = padding_extra(m_pos); 358 if (paddingSize > 0) { 359 uint32_t padding; 360 amt = read(m_fd, &padding, paddingSize); 361 CHECK_SIZE(amt, paddingSize); 362 m_pos += amt; 363 } 364 return NO_ERROR; 365} 366 367 368} // namespace android 369