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/**
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* Relational pipes
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* Copyright © 2021 František Kučera (Frantovo.cz, GlobalCode.info)
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, version 3 of the License.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#pragma once
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#include <string>
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#include <exception>
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#include <cstring>
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#include "AbstractParser.h"
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namespace relpipe {
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namespace in {
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namespace asn1 {
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namespace lib {
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class TransactionalBuffer {
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private:
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char* buffer;
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size_t bufferSize;
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bool hasData = false;
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size_t writePosition = 0;
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// size_t writePositionCommited = 0; // TODO: transactions also on the writing side?
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size_t readPosition = 0;
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size_t readPositionCommited = 0;
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size_t availableForReading() {
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if (readPosition < writePosition) return writePosition - readPosition;
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else if (readPosition > writePosition) return bufferSize - readPosition + writePosition;
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else if (hasData) return bufferSize;
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else return 0;
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}
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size_t availableForWriting() {
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if (readPositionCommited < writePosition) return bufferSize - writePosition + readPositionCommited;
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else if (readPositionCommited > writePosition) return readPositionCommited - writePosition;
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else if (hasData) return 0;
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else return bufferSize;
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}
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public:
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/**
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* Is thrown from read() and peak() methods if there are not enough data.
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* Interrupts current update() cycle and causes rollback.
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*/
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class ReadBufferUnderflowException {
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// TODO: common super-class for exceptions, hidden implementation
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};
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/**
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* Is thrown from write() method of the buffer when there is not enough space.
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* Interrupts whole process.
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*/
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class WriteBufferOverflowException {
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};
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TransactionalBuffer(size_t initialSize = 4096) : bufferSize(initialSize) {
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// TODO: initial size + resize + hard upper limit
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buffer = (char*) malloc(bufferSize);
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}
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virtual ~TransactionalBuffer() {
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free(buffer);
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}
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void write(const char* inputBuffer, const size_t length) {
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if (length == 0) return;
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if (length > availableForWriting()) throw WriteBufferOverflowException(); // TODO: optional resize
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hasData = true;
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const size_t a = std::min(length, bufferSize - writePosition);
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const size_t b = length - a;
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// TODO: map buffer twice in the memory in order to create a continuous area and avoid the second memcpy()?
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memcpy(buffer + writePosition, inputBuffer, a);
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memcpy(buffer, inputBuffer + a, b);
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writePosition = (writePosition + length) % bufferSize;
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}
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void read(char* outputBuffer, const size_t length) {
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if (length == 0) return;
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peek(outputBuffer, length);
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readPosition = (readPosition + length) % bufferSize;
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hasData = readPosition != writePosition;
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}
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void peek(char* outputBuffer, const size_t length) {
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if (length == 0) return;
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if (length > availableForReading()) throw ReadBufferUnderflowException();
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const size_t a = std::min(length, bufferSize - readPosition);
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const size_t b = length - a;
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memcpy(outputBuffer, buffer + readPosition, a);
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memcpy(outputBuffer + a, buffer, b);
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}
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void commitRead() {
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readPositionCommited = readPosition;
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}
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void rollbackRead() {
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readPosition = readPositionCommited;
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}
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};
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}
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}
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}
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}
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