1 /*
2 * Copyright (C) 2020 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 "zip_cd_entry_map.h"
18
ComputeHash(std::string_view name)19 static uint32_t ComputeHash(std::string_view name) {
20 return static_cast<uint32_t>(std::hash<std::string_view>{}(name));
21 }
22
23 template <typename ZipStringOffset>
ToStringView(ZipStringOffset & entry,const uint8_t * start)24 const std::string_view ToStringView(ZipStringOffset& entry, const uint8_t *start) {
25 auto name = reinterpret_cast<const char*>(start + entry.name_offset);
26 return std::string_view{name, entry.name_length};
27 }
28
29 // Convert a ZipEntry to a hash table index, verifying that it's in a valid range.
30 template <typename ZipStringOffset>
GetCdEntryOffset(std::string_view name,const uint8_t * start) const31 std::pair<ZipError, uint64_t> CdEntryMapZip32<ZipStringOffset>::GetCdEntryOffset(
32 std::string_view name, const uint8_t* start) const {
33 const uint32_t hash = ComputeHash(name);
34
35 // NOTE: (hash_table_size - 1) is guaranteed to be non-negative.
36 uint32_t ent = hash & (hash_table_size_ - 1);
37 while (hash_table_[ent].name_offset != 0) {
38 if (ToStringView(hash_table_[ent], start) == name) {
39 return {kSuccess, static_cast<uint64_t>(hash_table_[ent].name_offset)};
40 }
41 ent = (ent + 1) & (hash_table_size_ - 1);
42 }
43
44 ALOGV("Zip: Unable to find entry %.*s", static_cast<int>(name.size()), name.data());
45 return {kEntryNotFound, 0};
46 }
47
48 template <typename ZipStringOffset>
AddToMap(std::string_view name,const uint8_t * start)49 ZipError CdEntryMapZip32<ZipStringOffset>::AddToMap(std::string_view name, const uint8_t* start) {
50 const uint64_t hash = ComputeHash(name);
51 uint32_t ent = hash & (hash_table_size_ - 1);
52
53 /*
54 * We over-allocated the table, so we're guaranteed to find an empty slot.
55 * Further, we guarantee that the hashtable size is not 0.
56 */
57 while (hash_table_[ent].name_offset != 0) {
58 if (ToStringView(hash_table_[ent], start) == name) {
59 // We've found a duplicate entry. We don't accept duplicates.
60 ALOGW("Zip: Found duplicate entry %.*s", static_cast<int>(name.size()), name.data());
61 return kDuplicateEntry;
62 }
63 ent = (ent + 1) & (hash_table_size_ - 1);
64 }
65
66 // `name` has already been validated before entry.
67 const char* start_char = reinterpret_cast<const char*>(start);
68 hash_table_[ent].name_offset = static_cast<uint32_t>(name.data() - start_char);
69 hash_table_[ent].name_length = static_cast<uint16_t>(name.size());
70 return kSuccess;
71 }
72
73 template <typename ZipStringOffset>
ResetIteration()74 void CdEntryMapZip32<ZipStringOffset>::ResetIteration() {
75 current_position_ = 0;
76 }
77
78 template <typename ZipStringOffset>
Next(const uint8_t * cd_start)79 std::pair<std::string_view, uint64_t> CdEntryMapZip32<ZipStringOffset>::Next(
80 const uint8_t* cd_start) {
81 while (current_position_ < hash_table_size_) {
82 const auto& entry = hash_table_[current_position_];
83 current_position_ += 1;
84
85 if (entry.name_offset != 0) {
86 return {ToStringView(entry, cd_start), static_cast<uint64_t>(entry.name_offset)};
87 }
88 }
89 // We have reached the end of the hash table.
90 return {};
91 }
92
AddToMap(std::string_view name,const uint8_t * start)93 ZipError CdEntryMapZip64::AddToMap(std::string_view name, const uint8_t* start) {
94 const auto [it, added] =
95 entry_table_.insert({name, name.data() - reinterpret_cast<const char*>(start)});
96 if (!added) {
97 ALOGW("Zip: Found duplicate entry %.*s", static_cast<int>(name.size()), name.data());
98 return kDuplicateEntry;
99 }
100 return kSuccess;
101 }
102
GetCdEntryOffset(std::string_view name,const uint8_t *) const103 std::pair<ZipError, uint64_t> CdEntryMapZip64::GetCdEntryOffset(std::string_view name,
104 const uint8_t* /*cd_start*/) const {
105 const auto it = entry_table_.find(name);
106 if (it == entry_table_.end()) {
107 ALOGV("Zip: Could not find entry %.*s", static_cast<int>(name.size()), name.data());
108 return {kEntryNotFound, 0};
109 }
110
111 return {kSuccess, it->second};
112 }
113
ResetIteration()114 void CdEntryMapZip64::ResetIteration() {
115 iterator_ = entry_table_.begin();
116 }
117
Next(const uint8_t *)118 std::pair<std::string_view, uint64_t> CdEntryMapZip64::Next(const uint8_t* /*cd_start*/) {
119 if (iterator_ == entry_table_.end()) {
120 return {};
121 }
122
123 return *iterator_++;
124 }
125
Create(uint64_t num_entries,size_t cd_length,uint16_t max_file_name_length)126 std::unique_ptr<CdEntryMapInterface> CdEntryMapInterface::Create(uint64_t num_entries,
127 size_t cd_length, uint16_t max_file_name_length) {
128 using T = std::unique_ptr<CdEntryMapInterface>;
129 if (num_entries > UINT16_MAX)
130 return T(new CdEntryMapZip64());
131
132 uint16_t num_entries_ = static_cast<uint16_t>(num_entries);
133 if (cd_length > ZipStringOffset20::offset_max ||
134 max_file_name_length > ZipStringOffset20::length_max) {
135 return T(new CdEntryMapZip32<ZipStringOffset32>(num_entries_));
136 }
137 return T(new CdEntryMapZip32<ZipStringOffset20>(num_entries_));
138 }
139