141 lines
5.0 KiB
C++
141 lines
5.0 KiB
C++
/*
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* Copyright (C) 2016 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include "ChecksumCalculator.h"
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#include <string>
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#include <vector>
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#include <assert.h>
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#include <string.h>
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// Checklist when implementing new protocol:
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// 1. update CHECKSUMHELPER_MAX_VERSION
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// 2. update checksumByteSize()
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// 3. update addBuffer, writeChecksum, resetChecksum, validate
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// change CHECKSUMHELPER_MAX_VERSION when you want to update the protocol version
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#define CHECKSUMHELPER_MAX_VERSION 1
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// utility macros to create checksum string at compilation time
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#define CHECKSUMHELPER_VERSION_STR_PREFIX "ANDROID_EMU_CHECKSUM_HELPER_v"
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#define CHECKSUMHELPER_MACRO_TO_STR(x) #x
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#define CHECKSUMHELPER_MACRO_VAL_TO_STR(x) CHECKSUMHELPER_MACRO_TO_STR(x)
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static const uint32_t kMaxVersion = CHECKSUMHELPER_MAX_VERSION;
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static const char* kMaxVersionStrPrefix = CHECKSUMHELPER_VERSION_STR_PREFIX;
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static const char* kMaxVersionStr = CHECKSUMHELPER_VERSION_STR_PREFIX CHECKSUMHELPER_MACRO_VAL_TO_STR(CHECKSUMHELPER_MAX_VERSION);
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#undef CHECKSUMHELPER_MAX_VERSION
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#undef CHECKSUMHELPER_VERSION_STR_PREFIX
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#undef CHECKSUMHELPER_MACRO_TO_STR
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#undef CHECKSUMHELPER_MACRO_VAL_TO_STR
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uint32_t ChecksumCalculator::getMaxVersion() {return kMaxVersion;}
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const char* ChecksumCalculator::getMaxVersionStr() {return kMaxVersionStr;}
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const char* ChecksumCalculator::getMaxVersionStrPrefix() {return kMaxVersionStrPrefix;}
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bool ChecksumCalculator::setVersion(uint32_t version) {
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if (version > kMaxVersion) { // unsupported version
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LOG_CHECKSUMHELPER("%s: ChecksumCalculator Set Unsupported version Version %d\n",
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__FUNCTION__, m_version);
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return false;
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}
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if (m_isEncodingChecksum) { // setVersion is called in the middle of encoding checksums
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LOG_CHECKSUMHELPER("%s: called between addBuffer and writeChecksum\n",
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__FUNCTION__);
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return false;
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}
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m_version = version;
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m_checksumSize = checksumByteSize(version);
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LOG_CHECKSUMHELPER("%s: ChecksumCalculator Set Version %d\n", __FUNCTION__,
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m_version);
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return true;
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}
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void ChecksumCalculator::addBuffer(const void* buf, size_t packetLen) {
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m_isEncodingChecksum = true;
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switch (m_version) {
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case 1:
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m_v1BufferTotalLength += packetLen;
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break;
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}
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}
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bool ChecksumCalculator::writeChecksum(void* outputChecksum, size_t outputChecksumLen) {
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if (outputChecksumLen < checksumByteSize()) return false;
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char *checksumPtr = (char *)outputChecksum;
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switch (m_version) {
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case 1: { // protocol v1 is to reverse the packetLen and write it at the end
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uint32_t val = computeV1Checksum();
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memcpy(checksumPtr, &val, sizeof(val));
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memcpy(checksumPtr+sizeof(val), &m_numWrite, sizeof(m_numWrite));
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break;
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}
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}
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resetChecksum();
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m_numWrite++;
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return true;
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}
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void ChecksumCalculator::resetChecksum() {
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switch (m_version) {
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case 1:
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m_v1BufferTotalLength = 0;
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break;
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}
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m_isEncodingChecksum = false;
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}
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bool ChecksumCalculator::validate(const void* expectedChecksum,
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size_t expectedChecksumLen) {
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const size_t checksumSize = checksumByteSize();
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if (expectedChecksumLen != checksumSize) {
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m_numRead++;
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resetChecksum();
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return false;
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}
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bool isValid;
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switch (m_version) {
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case 1: {
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const uint32_t val = computeV1Checksum();
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assert(checksumSize == sizeof(val) + sizeof(m_numRead));
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isValid = 0 == memcmp(&val, expectedChecksum, sizeof(val)) &&
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0 == memcmp(&m_numRead,
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static_cast<const char*>(expectedChecksum) +
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sizeof(val),
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sizeof(m_numRead));
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break;
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}
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default:
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isValid = true; // No checksum is a valid checksum.
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break;
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}
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m_numRead++;
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resetChecksum();
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return isValid;
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}
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uint32_t ChecksumCalculator::computeV1Checksum() const {
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uint32_t revLen = m_v1BufferTotalLength;
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revLen = (revLen & 0xffff0000) >> 16 | (revLen & 0x0000ffff) << 16;
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revLen = (revLen & 0xff00ff00) >> 8 | (revLen & 0x00ff00ff) << 8;
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revLen = (revLen & 0xf0f0f0f0) >> 4 | (revLen & 0x0f0f0f0f) << 4;
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revLen = (revLen & 0xcccccccc) >> 2 | (revLen & 0x33333333) << 2;
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revLen = (revLen & 0xaaaaaaaa) >> 1 | (revLen & 0x55555555) << 1;
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return revLen;
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}
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