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 <androidfw/BackupHelpers.h>
20#include <utils/ByteOrder.h>
21
22#include <stdio.h>
23#include <string.h>
24#include <unistd.h>
25
26#include <cutils/log.h>
27
28namespace android {
29
30static const bool kIsDebug = false;
31
32/*
33 * File Format (v1):
34 *
35 * All ints are stored little-endian.
36 *
37 *  - An app_header_v1 struct.
38 *  - The name of the package, utf-8, null terminated, padded to 4-byte boundary.
39 *  - A sequence of zero or more key/value paires (entities), each with
40 *      - A entity_header_v1 struct
41 *      - The key, utf-8, null terminated, padded to 4-byte boundary.
42 *      - The value, padded to 4 byte boundary
43 */
44
45const static int ROUND_UP[4] = { 0, 3, 2, 1 };
46
47static inline size_t
48padding_extra(size_t n)
49{
50    return ROUND_UP[n % 4];
51}
52
53BackupDataWriter::BackupDataWriter(int fd)
54    :m_fd(fd),
55     m_status(NO_ERROR),
56     m_entityCount(0)
57{
58    m_pos = (ssize_t) lseek(fd, 0, SEEK_CUR);
59    if (kIsDebug) ALOGI("BackupDataWriter(%d) @ %ld", fd, (long)m_pos);
60}
61
62BackupDataWriter::~BackupDataWriter()
63{
64}
65
66// Pad out anything they've previously written to the next 4 byte boundary.
67status_t
68BackupDataWriter::write_padding_for(int n)
69{
70    ssize_t amt;
71    ssize_t paddingSize;
72
73    paddingSize = padding_extra(n);
74    if (paddingSize > 0) {
75        uint32_t padding = 0xbcbcbcbc;
76        if (kIsDebug) ALOGI("writing %zd padding bytes for %d", paddingSize, n);
77        amt = write(m_fd, &padding, paddingSize);
78        if (amt != paddingSize) {
79            m_status = errno;
80            return m_status;
81        }
82        m_pos += amt;
83    }
84    return NO_ERROR;
85}
86
87status_t
88BackupDataWriter::WriteEntityHeader(const String8& key, size_t dataSize)
89{
90    if (m_status != NO_ERROR) {
91        return m_status;
92    }
93
94    ssize_t amt;
95
96    amt = write_padding_for(m_pos);
97    if (amt != 0) {
98        return amt;
99    }
100
101    String8 k;
102    if (m_keyPrefix.length() > 0) {
103        k = m_keyPrefix;
104        k += ":";
105        k += key;
106    } else {
107        k = key;
108    }
109    if (kIsDebug) {
110        ALOGD("Writing header: prefix='%s' key='%s' dataSize=%zu", m_keyPrefix.string(),
111                key.string(), dataSize);
112    }
113
114    entity_header_v1 header;
115    ssize_t keyLen;
116
117    keyLen = k.length();
118
119    header.type = tolel(BACKUP_HEADER_ENTITY_V1);
120    header.keyLen = tolel(keyLen);
121    header.dataSize = tolel(dataSize);
122
123    if (kIsDebug) ALOGI("writing entity header, %zu bytes", sizeof(entity_header_v1));
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    if (kIsDebug) ALOGI("writing entity header key, %zd bytes", keyLen+1);
132    amt = write(m_fd, k.string(), keyLen+1);
133    if (amt != keyLen+1) {
134        m_status = errno;
135        return m_status;
136    }
137    m_pos += amt;
138
139    amt = write_padding_for(keyLen+1);
140
141    m_entityCount++;
142
143    return amt;
144}
145
146status_t
147BackupDataWriter::WriteEntityData(const void* data, size_t size)
148{
149    if (kIsDebug) ALOGD("Writing data: size=%lu", (unsigned long) size);
150
151    if (m_status != NO_ERROR) {
152        if (kIsDebug) {
153            ALOGD("Not writing data - stream in error state %d (%s)", m_status, strerror(m_status));
154        }
155        return m_status;
156    }
157
158    // We don't write padding here, because they're allowed to call this several
159    // times with smaller buffers.  We write it at the end of WriteEntityHeader
160    // instead.
161    ssize_t amt = write(m_fd, data, size);
162    if (amt != (ssize_t)size) {
163        m_status = errno;
164        if (kIsDebug) ALOGD("write returned error %d (%s)", m_status, strerror(m_status));
165        return m_status;
166    }
167    m_pos += amt;
168    return NO_ERROR;
169}
170
171void
172BackupDataWriter::SetKeyPrefix(const String8& keyPrefix)
173{
174    m_keyPrefix = keyPrefix;
175}
176
177
178BackupDataReader::BackupDataReader(int fd)
179    :m_fd(fd),
180     m_done(false),
181     m_status(NO_ERROR),
182     m_entityCount(0)
183{
184    memset(&m_header, 0, sizeof(m_header));
185    m_pos = (ssize_t) lseek(fd, 0, SEEK_CUR);
186    if (kIsDebug) ALOGI("BackupDataReader(%d) @ %ld", fd, (long)m_pos);
187}
188
189BackupDataReader::~BackupDataReader()
190{
191}
192
193status_t
194BackupDataReader::Status()
195{
196    return m_status;
197}
198
199#define CHECK_SIZE(actual, expected) \
200    do { \
201        if ((actual) != (expected)) { \
202            if ((actual) == 0) { \
203                m_status = EIO; \
204                m_done = true; \
205            } else { \
206                m_status = errno; \
207                ALOGD("CHECK_SIZE(a=%ld e=%ld) failed at line %d m_status='%s'", \
208                    long(actual), long(expected), __LINE__, strerror(m_status)); \
209            } \
210            return m_status; \
211        } \
212    } while(0)
213#define SKIP_PADDING() \
214    do { \
215        status_t err = skip_padding(); \
216        if (err != NO_ERROR) { \
217            ALOGD("SKIP_PADDING FAILED at line %d", __LINE__); \
218            m_status = err; \
219            return err; \
220        } \
221    } while(0)
222
223status_t
224BackupDataReader::ReadNextHeader(bool* done, int* type)
225{
226    *done = m_done;
227    if (m_status != NO_ERROR) {
228        return m_status;
229    }
230
231    int amt;
232
233    amt = skip_padding();
234    if (amt == EIO) {
235        *done = m_done = true;
236        return NO_ERROR;
237    }
238    else if (amt != NO_ERROR) {
239        return amt;
240    }
241    amt = read(m_fd, &m_header, sizeof(m_header));
242    *done = m_done = (amt == 0);
243    if (*done) {
244        return NO_ERROR;
245    }
246    CHECK_SIZE(amt, sizeof(m_header));
247    m_pos += sizeof(m_header);
248    if (type) {
249        *type = m_header.type;
250    }
251
252    // validate and fix up the fields.
253    m_header.type = fromlel(m_header.type);
254    switch (m_header.type)
255    {
256        case BACKUP_HEADER_ENTITY_V1:
257        {
258            m_header.entity.keyLen = fromlel(m_header.entity.keyLen);
259            if (m_header.entity.keyLen <= 0) {
260                ALOGD("Entity header at %d has keyLen<=0: 0x%08x\n", (int)m_pos,
261                        (int)m_header.entity.keyLen);
262                m_status = EINVAL;
263            }
264            m_header.entity.dataSize = fromlel(m_header.entity.dataSize);
265            m_entityCount++;
266
267            // read the rest of the header (filename)
268            size_t size = m_header.entity.keyLen;
269            char* buf = m_key.lockBuffer(size);
270            if (buf == NULL) {
271                m_status = ENOMEM;
272                return m_status;
273            }
274            int amt = read(m_fd, buf, size+1);
275            CHECK_SIZE(amt, (int)size+1);
276            m_key.unlockBuffer(size);
277            m_pos += size+1;
278            SKIP_PADDING();
279            m_dataEndPos = m_pos + m_header.entity.dataSize;
280
281            break;
282        }
283        default:
284            ALOGD("Chunk header at %d has invalid type: 0x%08x",
285                    (int)(m_pos - sizeof(m_header)), (int)m_header.type);
286            m_status = EINVAL;
287    }
288
289    return m_status;
290}
291
292bool
293BackupDataReader::HasEntities()
294{
295    return m_status == NO_ERROR && m_header.type == BACKUP_HEADER_ENTITY_V1;
296}
297
298status_t
299BackupDataReader::ReadEntityHeader(String8* key, size_t* dataSize)
300{
301    if (m_status != NO_ERROR) {
302        return m_status;
303    }
304    if (m_header.type != BACKUP_HEADER_ENTITY_V1) {
305        return EINVAL;
306    }
307    *key = m_key;
308    *dataSize = m_header.entity.dataSize;
309    return NO_ERROR;
310}
311
312status_t
313BackupDataReader::SkipEntityData()
314{
315    if (m_status != NO_ERROR) {
316        return m_status;
317    }
318    if (m_header.type != BACKUP_HEADER_ENTITY_V1) {
319        return EINVAL;
320    }
321    if (m_header.entity.dataSize > 0) {
322        int pos = lseek(m_fd, m_dataEndPos, SEEK_SET);
323        if (pos == -1) {
324            return errno;
325        }
326        m_pos = pos;
327    }
328    SKIP_PADDING();
329    return NO_ERROR;
330}
331
332ssize_t
333BackupDataReader::ReadEntityData(void* data, size_t size)
334{
335    if (m_status != NO_ERROR) {
336        return -1;
337    }
338    int remaining = m_dataEndPos - m_pos;
339    if (kIsDebug) {
340        ALOGD("ReadEntityData size=%zu m_pos=0x%zx m_dataEndPos=0x%zx remaining=%d\n",
341                size, m_pos, m_dataEndPos, remaining);
342    }
343    if (remaining <= 0) {
344        return 0;
345    }
346    if (((int)size) > remaining) {
347        size = remaining;
348    }
349    if (kIsDebug) {
350        ALOGD("   reading %zu bytes", size);
351    }
352    int amt = read(m_fd, data, size);
353    if (amt < 0) {
354        m_status = errno;
355        return -1;
356    }
357    if (amt == 0) {
358        m_status = EIO;
359        m_done = true;
360    }
361    m_pos += amt;
362    return amt;
363}
364
365status_t
366BackupDataReader::skip_padding()
367{
368    ssize_t amt;
369    ssize_t paddingSize;
370
371    paddingSize = padding_extra(m_pos);
372    if (paddingSize > 0) {
373        uint32_t padding;
374        amt = read(m_fd, &padding, paddingSize);
375        CHECK_SIZE(amt, paddingSize);
376        m_pos += amt;
377    }
378    return NO_ERROR;
379}
380
381
382} // namespace android
383