/* * Copyright (C) 2016 The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ #pragma once #include <stdint.h> #include <stdlib.h> // Set TRACE_CHECKSUMHELPER to 1 to debug creation/destruction of GLprotocol // instances. #define TRACE_CHECKSUMHELPER 0 #if TRACE_CHECKSUMHELPER #define LOG_CHECKSUMHELPER(x...) fprintf(stderr, x) #else #define LOG_CHECKSUMHELPER(x...) #endif namespace android { namespace base { class Stream; } } // namespace android // ChecksumCalculator adds checksum as an array of bytes to GL pipe communication, which // size depends on the protocol version. Each pipe should use one ChecksumCalculator. // It can: // (1) take a list of buffers one by one and compute their checksum string, // in this case the checksum should be as the data in those buffers are // concatenated; // (2) compute the checksum of the buffer list, then either write them into // a buffer provided by user, or compare it against a checksum provided // by user // (3) support different checksum version in future. // // For backward compatibility, checksum version 0 behaves the same as there is // no checksum (i.e., checksumByteSize returns 0, validate always returns true, // addBuffer and writeCheckSum does nothing). // // Notice that to detect package lost, ChecksumCalculator also keeps track of how // many times it generates/validates checksums, and might use it as part of the // checksum. // // To evaluate checksums from a list of data buffers buf1, buf2... Please call // addBuffer(buf1, buf1len), addBuffer(buf2, buf2len) ... in order. // Then if the checksum needs to be encoded into a buffer, one needs to allocate // a checksum buffer with size checksumByteSize(), and call // writeChecksum(checksumBuffer) to write the checksum to the buffer. // If the checksum needs to be validated against an existing one, one needs to // call validate(existChecksum, existChecksumLen). // // The checksum generator and validator must be set to the same version, and // the validator must check ALL checksums in the order they are generated, // otherwise the validation function will return false. // // It is allowed to change the checksum version between calculating two // checksums. This is designed for backward compatibility reason. // // Example 1, encoding and decoding: // // bool testChecksum(void* buf, size_t bufLen) { // // encoding message // ChecksumCalculator encoder; // encoder.setVersion(1); // encoder.addBuffer(buf, bufLen); // std::vector<unsigned char> message(bufLen + encoder.checksumByteSize()); // memcpy(&message[0], buf, bufLen); // encoder.writeChecksum(&message[0] + bufLen, encoder.checksumByteSize()); // // // decoding message // ChecksumCalculator decoder; // decoder.setVersion(1); // decoder.addBuffer(&message[0], bufLen); // return decoder.validate(&message[0] + bufLen, decoder.checksumByteSize()); // } // The return value is true. // // Example 2, decoding will fail if the order of messages is wrong: // // bool testChecksumOrder(void* buf1, size_t bufLen1, // void* buf2, size_t bufLen2) { // // encoding messages // ChecksumCalculator encoder; // encoder.setVersion(1); // // std::vector<unsigned char> message1(bufLen1 + encoder.checksumByteSize()); // std::vector<unsigned char> message2(bufLen2 + encoder.checksumByteSize()); // // encoder.addBuffer(buf1, bufLen1); // std::vector<unsigned char> message1(bufLen1 + encoder.checksumByteSize()); // memcpy(&message1[0], buf1, bufLen1); // encoder.writeChecksum(&message1[0] + bufLen1, encoder.checksumByteSize()); // // encoder.addBuffer(buf2, bufLen2); // std::vector<unsigned char> message2(bufLen2 + encoder.checksumByteSize()); // memcpy(&message2[0], buf2, bufLen2); // encoder.writeChecksum(&message2[0] + bufLen2, encoder.checksumByteSize()); // // // decoding messages // ChecksumCalculator decoder; // decoder.setVersion(1); // decoder.addBuffer(&message2[0], bufLen2); // // returns false because the decoding order is not consistent with // // encoding order // if (!decoder.validate(&message2[0]+bufLen2, decoder.checksumByteSize())) { // return false; // } // // decoder.addBuffer(&message1[0], bufLen1); // if (!decoder.validate(&message1[0]+bufLen1, decoder.checksumByteSize())) { // return false; // } // // return false; // } class ChecksumCalculator { public: static constexpr size_t kMaxChecksumLength = 8; // Get and set current checksum version uint32_t getVersion() const { return m_version; } // Call setVersion to set a checksum version. It should be called before // addBuffer(), writeChecksum() and validate(). And it should be called // exact once per rendering thread if both host and guest support checksum. // It won't be called if either host or guest does not support checksum. bool setVersion(uint32_t version); // Maximum supported checksum version static uint32_t getMaxVersion(); // A version string that looks like "ANDROID_EMU_CHECKSUM_HELPER_v1" // Used multiple times when the guest queries the maximum supported version // from the host. // The library owns the returned pointer. The returned pointer will be // deconstructed when unloading library. static const char* getMaxVersionStr(); static const char* getMaxVersionStrPrefix(); // Size of checksum in the current version size_t checksumByteSize() const { return m_checksumSize; } // Update the current checksum value from the data // at |buf| of |bufLen| bytes. Once all buffers // have been added, call writeChecksum() to store // the final checksum value and reset its state. void addBuffer(const void* buf, size_t bufLen); // Write the checksum from the list of buffers to outputChecksum // Will reset the list of buffers by calling resetChecksum. // Return false if the buffer is not long enough // Please query buffer size from checksumByteSize() bool writeChecksum(void* outputChecksum, size_t outputChecksumLen); // Restore the states for computing checksums. // Automatically called at the end of writeChecksum and validate. // Can also be used to abandon the current checksum being calculated. // Notes: it doesn't update the internal read / write counter void resetChecksum(); // Calculate the checksum from the list of buffers and // compare it with the checksum encoded in expectedChecksum // Will reset the list of buffers by calling resetChecksum. bool validate(const void* expectedChecksum, size_t expectedChecksumLen); private: static constexpr size_t kVersion1ChecksumSize = 8; // 2 x uint32_t static_assert(kVersion1ChecksumSize <= kMaxChecksumLength, "Invalid ChecksumCalculator::kMaxChecksumLength value"); static constexpr size_t checksumByteSize(uint32_t version) { return version == 1 ? kVersion1ChecksumSize : 0; } uint32_t m_version = 0; uint32_t m_checksumSize = checksumByteSize(0); // A temporary state used to compute the total length of a list of buffers, // if addBuffer is called. uint32_t m_numRead = 0; uint32_t m_numWrite = 0; // m_isEncodingChecksum is true when between addBuffer and writeChecksum bool m_isEncodingChecksum = false; // Compute a 32bit checksum // Used in protocol v1 uint32_t computeV1Checksum() const; // The buffer used in protocol version 1 to compute checksum. uint32_t m_v1BufferTotalLength = 0; };