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* 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
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* 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 LOG_CHECKSUMHELPER(x...) fprintf(stderr, x)
// 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 {
enum Sizes {
kVersion1ChecksumSize = 8,
kMaxChecksumSize = kVersion1ChecksumSize
// 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);
uint32_t m_version;
// A temporary state used to compute the total length of a list of buffers,
// if addBuffer is called.
uint32_t m_numRead;
uint32_t m_numWrite;
// m_isEncodingChecksum is true when between addBuffer and writeChecksum
bool m_isEncodingChecksum;
// 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;