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 #pragma once 18 19 #include <stdint.h> 20 #include <stdlib.h> 21 22 // Set TRACE_CHECKSUMHELPER to 1 to debug creation/destruction of GLprotocol 23 // instances. 24 #define TRACE_CHECKSUMHELPER 0 25 26 #if TRACE_CHECKSUMHELPER 27 #define LOG_CHECKSUMHELPER(x...) fprintf(stderr, x) 28 #else 29 #define LOG_CHECKSUMHELPER(x...) 30 #endif 31 32 namespace android { 33 namespace base { 34 class Stream; 35 } 36 } // namespace android 37 38 // ChecksumCalculator adds checksum as an array of bytes to GL pipe communication, which 39 // size depends on the protocol version. Each pipe should use one ChecksumCalculator. 40 // It can: 41 // (1) take a list of buffers one by one and compute their checksum string, 42 // in this case the checksum should be as the data in those buffers are 43 // concatenated; 44 // (2) compute the checksum of the buffer list, then either write them into 45 // a buffer provided by user, or compare it against a checksum provided 46 // by user 47 // (3) support different checksum version in future. 48 // 49 // For backward compatibility, checksum version 0 behaves the same as there is 50 // no checksum (i.e., checksumByteSize returns 0, validate always returns true, 51 // addBuffer and writeCheckSum does nothing). 52 // 53 // Notice that to detect package lost, ChecksumCalculator also keeps track of how 54 // many times it generates/validates checksums, and might use it as part of the 55 // checksum. 56 // 57 // To evaluate checksums from a list of data buffers buf1, buf2... Please call 58 // addBuffer(buf1, buf1len), addBuffer(buf2, buf2len) ... in order. 59 // Then if the checksum needs to be encoded into a buffer, one needs to allocate 60 // a checksum buffer with size checksumByteSize(), and call 61 // writeChecksum(checksumBuffer) to write the checksum to the buffer. 62 // If the checksum needs to be validated against an existing one, one needs to 63 // call validate(existChecksum, existChecksumLen). 64 // 65 // The checksum generator and validator must be set to the same version, and 66 // the validator must check ALL checksums in the order they are generated, 67 // otherwise the validation function will return false. 68 // 69 // It is allowed to change the checksum version between calculating two 70 // checksums. This is designed for backward compatibility reason. 71 // 72 // Example 1, encoding and decoding: 73 // 74 // bool testChecksum(void* buf, size_t bufLen) { 75 // // encoding message 76 // ChecksumCalculator encoder; 77 // encoder.setVersion(1); 78 // encoder.addBuffer(buf, bufLen); 79 // std::vector<unsigned char> message(bufLen + encoder.checksumByteSize()); 80 // memcpy(&message[0], buf, bufLen); 81 // encoder.writeChecksum(&message[0] + bufLen, encoder.checksumByteSize()); 82 // 83 // // decoding message 84 // ChecksumCalculator decoder; 85 // decoder.setVersion(1); 86 // decoder.addBuffer(&message[0], bufLen); 87 // return decoder.validate(&message[0] + bufLen, decoder.checksumByteSize()); 88 // } 89 // The return value is true. 90 // 91 // Example 2, decoding will fail if the order of messages is wrong: 92 // 93 // bool testChecksumOrder(void* buf1, size_t bufLen1, 94 // void* buf2, size_t bufLen2) { 95 // // encoding messages 96 // ChecksumCalculator encoder; 97 // encoder.setVersion(1); 98 // 99 // std::vector<unsigned char> message1(bufLen1 + encoder.checksumByteSize()); 100 // std::vector<unsigned char> message2(bufLen2 + encoder.checksumByteSize()); 101 // 102 // encoder.addBuffer(buf1, bufLen1); 103 // std::vector<unsigned char> message1(bufLen1 + encoder.checksumByteSize()); 104 // memcpy(&message1[0], buf1, bufLen1); 105 // encoder.writeChecksum(&message1[0] + bufLen1, encoder.checksumByteSize()); 106 // 107 // encoder.addBuffer(buf2, bufLen2); 108 // std::vector<unsigned char> message2(bufLen2 + encoder.checksumByteSize()); 109 // memcpy(&message2[0], buf2, bufLen2); 110 // encoder.writeChecksum(&message2[0] + bufLen2, encoder.checksumByteSize()); 111 // 112 // // decoding messages 113 // ChecksumCalculator decoder; 114 // decoder.setVersion(1); 115 // decoder.addBuffer(&message2[0], bufLen2); 116 // // returns false because the decoding order is not consistent with 117 // // encoding order 118 // if (!decoder.validate(&message2[0]+bufLen2, decoder.checksumByteSize())) { 119 // return false; 120 // } 121 // 122 // decoder.addBuffer(&message1[0], bufLen1); 123 // if (!decoder.validate(&message1[0]+bufLen1, decoder.checksumByteSize())) { 124 // return false; 125 // } 126 // 127 // return false; 128 // } 129 130 class ChecksumCalculator { 131 public: 132 static constexpr size_t kMaxChecksumLength = 8; 133 134 // Get and set current checksum version getVersion()135 uint32_t getVersion() const { 136 return m_version; 137 } 138 // Call setVersion to set a checksum version. It should be called before 139 // addBuffer(), writeChecksum() and validate(). And it should be called 140 // exact once per rendering thread if both host and guest support checksum. 141 // It won't be called if either host or guest does not support checksum. 142 bool setVersion(uint32_t version); 143 144 // Maximum supported checksum version 145 static uint32_t getMaxVersion(); 146 // A version string that looks like "ANDROID_EMU_CHECKSUM_HELPER_v1" 147 // Used multiple times when the guest queries the maximum supported version 148 // from the host. 149 // The library owns the returned pointer. The returned pointer will be 150 // deconstructed when unloading library. 151 static const char* getMaxVersionStr(); 152 static const char* getMaxVersionStrPrefix(); 153 154 // Size of checksum in the current version checksumByteSize()155 size_t checksumByteSize() const { 156 return m_checksumSize; 157 } 158 159 // Update the current checksum value from the data 160 // at |buf| of |bufLen| bytes. Once all buffers 161 // have been added, call writeChecksum() to store 162 // the final checksum value and reset its state. 163 void addBuffer(const void* buf, size_t bufLen); 164 // Write the checksum from the list of buffers to outputChecksum 165 // Will reset the list of buffers by calling resetChecksum. 166 // Return false if the buffer is not long enough 167 // Please query buffer size from checksumByteSize() 168 bool writeChecksum(void* outputChecksum, size_t outputChecksumLen); 169 // Restore the states for computing checksums. 170 // Automatically called at the end of writeChecksum and validate. 171 // Can also be used to abandon the current checksum being calculated. 172 // Notes: it doesn't update the internal read / write counter 173 void resetChecksum(); 174 175 // Calculate the checksum from the list of buffers and 176 // compare it with the checksum encoded in expectedChecksum 177 // Will reset the list of buffers by calling resetChecksum. 178 bool validate(const void* expectedChecksum, size_t expectedChecksumLen); 179 180 private: 181 static constexpr size_t kVersion1ChecksumSize = 8; // 2 x uint32_t 182 183 static_assert(kVersion1ChecksumSize <= kMaxChecksumLength, 184 "Invalid ChecksumCalculator::kMaxChecksumLength value"); 185 checksumByteSize(uint32_t version)186 static constexpr size_t checksumByteSize(uint32_t version) { 187 return version == 1 ? kVersion1ChecksumSize : 0; 188 } 189 190 uint32_t m_version = 0; 191 uint32_t m_checksumSize = checksumByteSize(0); 192 // A temporary state used to compute the total length of a list of buffers, 193 // if addBuffer is called. 194 uint32_t m_numRead = 0; 195 uint32_t m_numWrite = 0; 196 // m_isEncodingChecksum is true when between addBuffer and writeChecksum 197 bool m_isEncodingChecksum = false; 198 199 // Compute a 32bit checksum 200 // Used in protocol v1 201 uint32_t computeV1Checksum() const; 202 // The buffer used in protocol version 1 to compute checksum. 203 uint32_t m_v1BufferTotalLength = 0; 204 }; 205