1 /*
2 * Copyright (C) 2021 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 #include "lz4_legacy.h"
18
19 #include <fcntl.h>
20 #include <sys/stat.h>
21
22 #include <vector>
23
24 #include <android-base/file.h>
25 #include <android-base/result.h>
26 #include <android-base/unique_fd.h>
27 #include <lz4.h>
28 #include <storage_literals/storage_literals.h>
29
30 using android::base::ErrnoError;
31 using android::base::Error;
32 using android::base::ReadFully;
33 using android::base::unique_fd;
34 using android::base::WriteFully;
35 using android::storage_literals::operator""_MiB;
36
37 namespace android {
38
Lz4DecompressLegacy(const char * input,const char * output)39 android::base::Result<void> Lz4DecompressLegacy(const char* input,
40 const char* output) {
41 constexpr uint32_t lz4_legacy_magic = 0x184C2102;
42 constexpr auto lz4_legacy_block_size = 8_MiB;
43
44 unique_fd ifd(TEMP_FAILURE_RETRY(open(input, O_RDONLY | O_CLOEXEC)));
45 unique_fd ofd(TEMP_FAILURE_RETRY(
46 open(output, O_WRONLY | O_CREAT | O_CLOEXEC | O_TRUNC, 0640)));
47
48 uint32_t magic;
49 if (!ReadFully(ifd, &magic, sizeof(magic))) {
50 return ErrnoError() << "read magic";
51 }
52 // Android is little-endian. No need to convert magic.
53 if (magic != lz4_legacy_magic) {
54 return Error() << "magic is " << std::hex << magic << " but expected "
55 << lz4_legacy_magic;
56 }
57
58 std::vector<char> ibuf(LZ4_compressBound(lz4_legacy_block_size));
59 std::vector<char> obuf(lz4_legacy_block_size);
60
61 while (true) {
62 uint32_t block_size;
63 ssize_t read_bytes =
64 TEMP_FAILURE_RETRY(read(ifd.get(), &block_size, sizeof(block_size)));
65 if (read_bytes == 0) break;
66 if (read_bytes < 0) {
67 return ErrnoError() << "read block size";
68 }
69 if (static_cast<size_t>(read_bytes) != sizeof(block_size)) {
70 return Error() << "Cannot read " << sizeof(block_size)
71 << " bytes for block size";
72 }
73
74 // Android is little-endian. No need to convert block_size.
75 if (block_size == lz4_legacy_magic) {
76 return Error() << "Found another lz4 compressed stream";
77 }
78 if (block_size > ibuf.size()) {
79 return Error() << "Block size is " << block_size
80 << " but compress bound is " << ibuf.size();
81 }
82
83 if (!ReadFully(ifd, ibuf.data(), block_size)) {
84 return ErrnoError() << "read " << block_size << " bytes";
85 }
86
87 int decoded_size =
88 LZ4_decompress_safe(ibuf.data(), obuf.data(), block_size, obuf.size());
89 if (decoded_size < 0) {
90 return Error() << "LZ4_decompress_safe returns " << decoded_size;
91 }
92
93 if (!WriteFully(ofd, obuf.data(), decoded_size)) {
94 return ErrnoError() << "write " << decoded_size << " bytes";
95 }
96 }
97
98 return {};
99 }
100 } // namespace android
101