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