BackupData.cpp revision 8d72569e3b85a352afe0fe1125b784d2ac13cde1
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 (true) { 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 } else { \ 197 m_status = errno; \ 198 } \ 199 LOGD("CHECK_SIZE failed with at line %d m_status='%s'", __LINE__, strerror(m_status)); \ 200 return m_status; \ 201 } \ 202 } while(0) 203#define SKIP_PADDING() \ 204 do { \ 205 status_t err = skip_padding(); \ 206 if (err != NO_ERROR) { \ 207 LOGD("SKIP_PADDING FAILED at line %d", __LINE__); \ 208 m_status = err; \ 209 return err; \ 210 } \ 211 } while(0) 212 213status_t 214BackupDataReader::ReadNextHeader(bool* done, int* type) 215{ 216 *done = m_done; 217 if (m_status != NO_ERROR) { 218 return m_status; 219 } 220 221 int amt; 222 223 amt = skip_padding(); 224 if (amt == EIO) { 225 *done = true; 226 return NO_ERROR; 227 } 228 else if (amt != NO_ERROR) { 229 return amt; 230 } 231 amt = read(m_fd, &m_header, sizeof(m_header)); 232 *done = m_done = (amt == 0); 233 if (*done) { 234 return NO_ERROR; 235 } 236 CHECK_SIZE(amt, sizeof(m_header)); 237 m_pos += sizeof(m_header); 238 if (type) { 239 *type = m_header.type; 240 } 241 242 // validate and fix up the fields. 243 m_header.type = fromlel(m_header.type); 244 switch (m_header.type) 245 { 246 case BACKUP_HEADER_ENTITY_V1: 247 { 248 m_header.entity.keyLen = fromlel(m_header.entity.keyLen); 249 if (m_header.entity.keyLen <= 0) { 250 LOGD("Entity header at %d has keyLen<=0: 0x%08x\n", (int)m_pos, 251 (int)m_header.entity.keyLen); 252 m_status = EINVAL; 253 } 254 m_header.entity.dataSize = fromlel(m_header.entity.dataSize); 255 m_entityCount++; 256 257 // read the rest of the header (filename) 258 size_t size = m_header.entity.keyLen; 259 char* buf = m_key.lockBuffer(size); 260 if (buf == NULL) { 261 m_status = ENOMEM; 262 return m_status; 263 } 264 int amt = read(m_fd, buf, size+1); 265 CHECK_SIZE(amt, (int)size+1); 266 m_key.unlockBuffer(size); 267 m_pos += size+1; 268 SKIP_PADDING(); 269 m_dataEndPos = m_pos + m_header.entity.dataSize; 270 271 break; 272 } 273 default: 274 LOGD("Chunk header at %d has invalid type: 0x%08x", (int)m_pos, (int)m_header.type); 275 m_status = EINVAL; 276 } 277 278 return m_status; 279} 280 281bool 282BackupDataReader::HasEntities() 283{ 284 return m_status == NO_ERROR && m_header.type == BACKUP_HEADER_ENTITY_V1; 285} 286 287status_t 288BackupDataReader::ReadEntityHeader(String8* key, size_t* dataSize) 289{ 290 if (m_status != NO_ERROR) { 291 return m_status; 292 } 293 if (m_header.type != BACKUP_HEADER_ENTITY_V1) { 294 return EINVAL; 295 } 296 *key = m_key; 297 *dataSize = m_header.entity.dataSize; 298 return NO_ERROR; 299} 300 301status_t 302BackupDataReader::SkipEntityData() 303{ 304 if (m_status != NO_ERROR) { 305 return m_status; 306 } 307 if (m_header.type != BACKUP_HEADER_ENTITY_V1) { 308 return EINVAL; 309 } 310 if (m_header.entity.dataSize > 0) { 311 int pos = lseek(m_fd, m_dataEndPos, SEEK_SET); 312 if (pos == -1) { 313 return errno; 314 } 315 } 316 SKIP_PADDING(); 317 return NO_ERROR; 318} 319 320ssize_t 321BackupDataReader::ReadEntityData(void* data, size_t size) 322{ 323 if (m_status != NO_ERROR) { 324 return -1; 325 } 326 int remaining = m_dataEndPos - m_pos; 327 //LOGD("ReadEntityData size=%d m_pos=0x%x m_dataEndPos=0x%x remaining=%d\n", 328 // size, m_pos, m_dataEndPos, remaining); 329 if (remaining <= 0) { 330 return 0; 331 } 332 if (((int)size) > remaining) { 333 size = remaining; 334 } 335 //LOGD(" reading %d bytes", size); 336 int amt = read(m_fd, data, size); 337 if (amt < 0) { 338 m_status = errno; 339 return -1; 340 } 341 m_pos += amt; 342 return amt; 343} 344 345status_t 346BackupDataReader::skip_padding() 347{ 348 ssize_t amt; 349 ssize_t paddingSize; 350 351 paddingSize = padding_extra(m_pos); 352 if (paddingSize > 0) { 353 uint32_t padding; 354 amt = read(m_fd, &padding, paddingSize); 355 CHECK_SIZE(amt, paddingSize); 356 m_pos += amt; 357 } 358 return NO_ERROR; 359} 360 361 362} // namespace android 363