1 /*
2 * Copyright (C) 2016 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 "gfxstream/guest/ChecksumCalculator.h"
18
19 #include <string.h>
20
21 namespace gfxstream {
22 namespace guest {
23
24 // Checklist when implementing new protocol:
25 // 1. update CHECKSUMHELPER_MAX_VERSION
26 // 2. update ChecksumCalculator::Sizes enum
27 // 3. update checksumByteSize()
28 // 4. update addBuffer, writeChecksum, resetChecksum, validate
29
30 // change CHECKSUMHELPER_MAX_VERSION when you want to update the protocol version
31 #define CHECKSUMHELPER_MAX_VERSION 1
32
33 // utility macros to create checksum string at compilation time
34 #define CHECKSUMHELPER_VERSION_STR_PREFIX "ANDROID_EMU_CHECKSUM_HELPER_v"
35 #define CHECKSUMHELPER_MACRO_TO_STR(x) #x
36 #define CHECKSUMHELPER_MACRO_VAL_TO_STR(x) CHECKSUMHELPER_MACRO_TO_STR(x)
37
38 static const uint32_t kMaxVersion = CHECKSUMHELPER_MAX_VERSION;
39 static const char* kMaxVersionStrPrefix = CHECKSUMHELPER_VERSION_STR_PREFIX;
40 static const char* kMaxVersionStr = CHECKSUMHELPER_VERSION_STR_PREFIX CHECKSUMHELPER_MACRO_VAL_TO_STR(CHECKSUMHELPER_MAX_VERSION);
41
42 #undef CHECKSUMHELPER_MAX_VERSION
43 #undef CHECKSUMHELPER_VERSION_STR_PREFIX
44 #undef CHECKSUMHELPER_MACRO_TO_STR
45 #undef CHECKSUMHELPER_MACRO_VAL_TO_STR
46
getMaxVersion()47 uint32_t ChecksumCalculator::getMaxVersion() {return kMaxVersion;}
getMaxVersionStr()48 const char* ChecksumCalculator::getMaxVersionStr() {return kMaxVersionStr;}
getMaxVersionStrPrefix()49 const char* ChecksumCalculator::getMaxVersionStrPrefix() {return kMaxVersionStrPrefix;}
50
setVersion(uint32_t version)51 bool ChecksumCalculator::setVersion(uint32_t version) {
52 if (version > kMaxVersion) { // unsupported version
53 LOG_CHECKSUMHELPER("%s: ChecksumCalculator Set Unsupported version Version %d\n",
54 __FUNCTION__, m_version);
55 return false;
56 }
57 if (m_isEncodingChecksum) { // setVersion is called in the middle of encoding checksums
58 LOG_CHECKSUMHELPER("%s: called between addBuffer and writeChecksum\n",
59 __FUNCTION__);
60 return false;
61 }
62 m_version = version;
63 LOG_CHECKSUMHELPER("%s: ChecksumCalculator Set Version %d\n", __FUNCTION__,
64 m_version);
65 return true;
66 }
67
checksumByteSize() const68 size_t ChecksumCalculator::checksumByteSize() const {
69 switch (m_version) {
70 case 0:
71 return 0;
72 case 1:
73 return sizeof(uint32_t) + sizeof(m_numWrite);
74 default:
75 return 0;
76 }
77 }
78
ChecksumCalculator()79 ChecksumCalculator::ChecksumCalculator()
80 : m_version(0)
81 , m_numRead(0)
82 , m_numWrite(0)
83 , m_isEncodingChecksum(false)
84 , m_v1BufferTotalLength(0)
85 {
86 }
87
addBuffer(const void *,size_t packetLen)88 void ChecksumCalculator::addBuffer(const void*, size_t packetLen) {
89 m_isEncodingChecksum = true;
90 switch (m_version) {
91 case 1:
92 m_v1BufferTotalLength += packetLen;
93 break;
94 }
95 }
96
writeChecksum(void * outputChecksum,size_t outputChecksumLen)97 bool ChecksumCalculator::writeChecksum(void* outputChecksum, size_t outputChecksumLen) {
98 if (outputChecksumLen < checksumByteSize()) return false;
99 char *checksumPtr = (char *)outputChecksum;
100 switch (m_version) {
101 case 1: { // protocol v1 is to reverse the packetLen and write it at the end
102 uint32_t val = computeV1Checksum();
103 memcpy(checksumPtr, &val, sizeof(val));
104 memcpy(checksumPtr+sizeof(val), &m_numWrite, sizeof(m_numWrite));
105 break;
106 }
107 }
108 resetChecksum();
109 m_numWrite++;
110 return true;
111 }
112
resetChecksum()113 void ChecksumCalculator::resetChecksum() {
114 switch (m_version) {
115 case 1:
116 m_v1BufferTotalLength = 0;
117 break;
118 }
119 m_isEncodingChecksum = false;
120 }
121
validate(const void * expectedChecksum,size_t expectedChecksumLen)122 bool ChecksumCalculator::validate(const void* expectedChecksum, size_t expectedChecksumLen) {
123 size_t checksumSize = checksumByteSize();
124 if (expectedChecksumLen != checksumSize) {
125 m_numRead++;
126 resetChecksum();
127 return false;
128 }
129 bool isValid;
130 switch (m_version) {
131 case 1: {
132 const uint32_t val = computeV1Checksum();
133 isValid = 0 == memcmp(&val, expectedChecksum, sizeof(val)) &&
134 0 == memcmp(&m_numRead,
135 static_cast<const char*>(expectedChecksum) +
136 sizeof(val),
137 sizeof(m_numRead));
138
139 break;
140 }
141 default:
142 isValid = true; // No checksum is a valid checksum.
143 break;
144 }
145 m_numRead++;
146 resetChecksum();
147 return isValid;
148 }
149
computeV1Checksum()150 uint32_t ChecksumCalculator::computeV1Checksum() {
151 uint32_t revLen = m_v1BufferTotalLength;
152 revLen = (revLen & 0xffff0000) >> 16 | (revLen & 0x0000ffff) << 16;
153 revLen = (revLen & 0xff00ff00) >> 8 | (revLen & 0x00ff00ff) << 8;
154 revLen = (revLen & 0xf0f0f0f0) >> 4 | (revLen & 0x0f0f0f0f) << 4;
155 revLen = (revLen & 0xcccccccc) >> 2 | (revLen & 0x33333333) << 2;
156 revLen = (revLen & 0xaaaaaaaa) >> 1 | (revLen & 0x55555555) << 1;
157 return revLen;
158 }
159
160 } // namespace guest
161 } // namespace gfxstream