--- /dev/null
+/*
+* 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
+
+// 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:
+ // 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;
+
+ // 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);
+protected:
+ uint32_t m_version = 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;
+private:
+ // Compute a 32bit checksum
+ // Used in protocol v1
+ uint32_t computeV1Checksum();
+ // The buffer used in protocol version 1 to compute checksum.
+ uint32_t m_v1BufferTotalLength = 0;
+};
Code Review / iec.git / blobdiff