util/CircularBuffer: new buffer class
This commit is contained in:
Max Kellermann
parent
b10276ff98
commit
f660d30138
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@ -362,6 +362,7 @@ libutil_a_SOURCES = \
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src/util/DynamicFifoBuffer.hxx \
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src/util/ConstBuffer.hxx \
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src/util/WritableBuffer.hxx \
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src/util/CircularBuffer.hxx \
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src/util/LazyRandomEngine.cxx src/util/LazyRandomEngine.hxx \
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src/util/SliceBuffer.hxx \
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src/util/HugeAllocator.cxx src/util/HugeAllocator.hxx \
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@ -1832,6 +1833,7 @@ test_run_inotify_LDADD = \
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endif
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test_test_util_SOURCES = \
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test/TestCircularBuffer.hxx \
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test/test_util.cxx
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test_test_util_CPPFLAGS = $(AM_CPPFLAGS) $(CPPUNIT_CFLAGS) -DCPPUNIT_HAVE_RTTI=0
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test_test_util_CXXFLAGS = $(AM_CXXFLAGS) -Wno-error=deprecated-declarations
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@ -0,0 +1,165 @@
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/*
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* Copyright (C) 2014 Max Kellermann <max@duempel.org>
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* - Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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*
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* - Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the
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* distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* FOUNDATION OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
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* OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#ifndef CIRCULAR_BUFFER_HPP
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#define CIRCULAR_BUFFER_HPP
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#include "WritableBuffer.hxx"
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#include <assert.h>
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#include <stddef.h>
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/**
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* A circular buffer.
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*
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* This class does not manage buffer memory. It will not allocate or
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* free any memory, it only manages the contents of an existing
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* buffer given to the constructor.
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*
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* Everything between #head and #tail is valid data (may wrap around).
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* If both are equal, then the buffer is empty. Due to this
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* implementation detail, the buffer is empty when #size-1 items are
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* stored; the last buffer cell cannot be used.
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*/
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template<typename T>
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class CircularBuffer {
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public:
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typedef WritableBuffer<T> Range;
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typedef typename Range::pointer_type pointer_type;
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typedef typename Range::size_type size_type;
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protected:
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/**
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* The next index to be read.
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*/
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size_type head;
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/**
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* The next index to be written to.
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*/
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size_type tail;
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const size_type size;
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const pointer_type data;
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public:
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constexpr CircularBuffer(pointer_type _data, size_type _size)
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:head(0), tail(0), size(_size), data(_data) {}
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CircularBuffer(const CircularBuffer &other) = delete;
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protected:
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constexpr size_type Next(size_type i) const {
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return i + 1 == size
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? 0
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: i + 1;
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}
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public:
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void Clear() {
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head = tail = 0;
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}
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size_type GetSize() const {
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return size;
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}
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constexpr bool IsEmpty() const {
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return head == tail;
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}
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constexpr bool IsFull() const {
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return Next(tail) == head;
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}
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/**
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* Prepares writing. Returns a buffer range which may be written.
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* When you are finished, call Append().
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*/
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Range Write() {
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assert(head < size);
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assert(tail < size);
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size_type end = tail < head
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? head - 1
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/* the "head==0" is there so we don't write
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the last cell, as this situation cannot be
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represented by head/tail */
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: size - (head == 0);
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return Range(data + tail, end - tail);
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}
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/**
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* Expands the tail of the buffer, after data has been written
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* to the buffer returned by Write().
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*/
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void Append(size_type n) {
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assert(head < size);
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assert(tail < size);
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assert(n < size);
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assert(tail + n <= size);
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assert(head <= tail || tail + n < head);
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tail += n;
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if (tail == size) {
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assert(head > 0);
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tail = 0;
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}
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}
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/**
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* Return a buffer range which may be read. The buffer pointer is
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* writable, to allow modifications while parsing.
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*/
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Range Read() {
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assert(head < size);
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assert(tail < size);
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return Range(data + head, (tail < head ? size : tail) - head);
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}
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/**
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* Marks a chunk as consumed.
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*/
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void Consume(size_type n) {
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assert(head < size);
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assert(tail < size);
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assert(n < size);
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assert(head + n <= size);
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assert(tail < head || head + n <= tail);
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head += n;
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if (head == size)
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head = 0;
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}
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};
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#endif
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@ -0,0 +1,141 @@
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/*
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* Unit tests for class CircularBuffer.
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*/
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#include "config.h"
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#include "util/CircularBuffer.hxx"
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#include <cppunit/TestFixture.h>
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#include <cppunit/extensions/TestFactoryRegistry.h>
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#include <cppunit/ui/text/TestRunner.h>
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#include <cppunit/extensions/HelperMacros.h>
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#include <string.h>
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#include <stdlib.h>
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class TestCircularBuffer : public CppUnit::TestFixture {
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CPPUNIT_TEST_SUITE(TestCircularBuffer);
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CPPUNIT_TEST(TestIt);
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CPPUNIT_TEST_SUITE_END();
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public:
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void TestIt() {
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static size_t N = 8;
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int data[N];
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CircularBuffer<int> buffer(data, N);
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/* '.' = empty; 'O' = occupied; 'X' = blocked */
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/* checks on empty buffer */
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/* [.......X] */
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CPPUNIT_ASSERT_EQUAL(true, buffer.IsEmpty());
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CPPUNIT_ASSERT_EQUAL(false, buffer.IsFull());
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CPPUNIT_ASSERT_EQUAL(true, buffer.Read().IsEmpty());
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CPPUNIT_ASSERT_EQUAL(false, buffer.Write().IsEmpty());
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CPPUNIT_ASSERT_EQUAL(&data[0], buffer.Write().data);
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CPPUNIT_ASSERT_EQUAL(size_t(7), buffer.Write().size);
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/* append one element */
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/* [O......X] */
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buffer.Append(1);
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CPPUNIT_ASSERT_EQUAL(false, buffer.IsEmpty());
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CPPUNIT_ASSERT_EQUAL(false, buffer.IsFull());
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CPPUNIT_ASSERT_EQUAL(false, buffer.Read().IsEmpty());
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CPPUNIT_ASSERT_EQUAL(size_t(1), buffer.Read().size);
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CPPUNIT_ASSERT_EQUAL(&data[0], buffer.Read().data);
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CPPUNIT_ASSERT_EQUAL(false, buffer.Write().IsEmpty());
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CPPUNIT_ASSERT_EQUAL(&data[1], buffer.Write().data);
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CPPUNIT_ASSERT_EQUAL(size_t(6), buffer.Write().size);
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/* append 6 elements, buffer is now full */
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/* [OOOOOOOX] */
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buffer.Append(6);
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CPPUNIT_ASSERT_EQUAL(false, buffer.IsEmpty());
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CPPUNIT_ASSERT_EQUAL(true, buffer.IsFull());
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CPPUNIT_ASSERT_EQUAL(false, buffer.Read().IsEmpty());
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CPPUNIT_ASSERT_EQUAL(size_t(7), buffer.Read().size);
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CPPUNIT_ASSERT_EQUAL(&data[0], buffer.Read().data);
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CPPUNIT_ASSERT_EQUAL(true, buffer.Write().IsEmpty());
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/* consume [0]; can append one at [7] */
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/* [XOOOOOO.] */
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buffer.Consume(1);
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CPPUNIT_ASSERT_EQUAL(false, buffer.IsEmpty());
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CPPUNIT_ASSERT_EQUAL(false, buffer.IsFull());
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CPPUNIT_ASSERT_EQUAL(false, buffer.Read().IsEmpty());
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CPPUNIT_ASSERT_EQUAL(size_t(6), buffer.Read().size);
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CPPUNIT_ASSERT_EQUAL(&data[1], buffer.Read().data);
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CPPUNIT_ASSERT_EQUAL(false, buffer.Write().IsEmpty());
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CPPUNIT_ASSERT_EQUAL(&data[7], buffer.Write().data);
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CPPUNIT_ASSERT_EQUAL(size_t(1), buffer.Write().size);
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/* append one element; [0] is still empty but cannot
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be written to because head==1 */
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/* [XOOOOOOO] */
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buffer.Append(1);
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CPPUNIT_ASSERT_EQUAL(false, buffer.IsEmpty());
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CPPUNIT_ASSERT_EQUAL(true, buffer.IsFull());
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CPPUNIT_ASSERT_EQUAL(false, buffer.Read().IsEmpty());
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CPPUNIT_ASSERT_EQUAL(size_t(7), buffer.Read().size);
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CPPUNIT_ASSERT_EQUAL(&data[1], buffer.Read().data);
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CPPUNIT_ASSERT_EQUAL(true, buffer.Write().IsEmpty());
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/* consume [1..3]; can append [0..2] */
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/* [...XOOOO] */
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buffer.Consume(3);
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CPPUNIT_ASSERT_EQUAL(false, buffer.IsEmpty());
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CPPUNIT_ASSERT_EQUAL(false, buffer.IsFull());
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CPPUNIT_ASSERT_EQUAL(false, buffer.Read().IsEmpty());
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CPPUNIT_ASSERT_EQUAL(size_t(4), buffer.Read().size);
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CPPUNIT_ASSERT_EQUAL(&data[4], buffer.Read().data);
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CPPUNIT_ASSERT_EQUAL(false, buffer.Write().IsEmpty());
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CPPUNIT_ASSERT_EQUAL(&data[0], buffer.Write().data);
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CPPUNIT_ASSERT_EQUAL(size_t(3), buffer.Write().size);
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/* append [0..1] */
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/* [OO.XOOOO] */
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buffer.Append(2);
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CPPUNIT_ASSERT_EQUAL(false, buffer.IsEmpty());
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CPPUNIT_ASSERT_EQUAL(false, buffer.IsFull());
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CPPUNIT_ASSERT_EQUAL(false, buffer.Read().IsEmpty());
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CPPUNIT_ASSERT_EQUAL(size_t(4), buffer.Read().size);
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CPPUNIT_ASSERT_EQUAL(&data[4], buffer.Read().data);
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CPPUNIT_ASSERT_EQUAL(false, buffer.Write().IsEmpty());
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CPPUNIT_ASSERT_EQUAL(&data[2], buffer.Write().data);
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CPPUNIT_ASSERT_EQUAL(size_t(1), buffer.Write().size);
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/* append [2] */
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/* [OOOXOOOO] */
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buffer.Append(1);
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CPPUNIT_ASSERT_EQUAL(false, buffer.IsEmpty());
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CPPUNIT_ASSERT_EQUAL(true, buffer.IsFull());
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CPPUNIT_ASSERT_EQUAL(false, buffer.Read().IsEmpty());
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CPPUNIT_ASSERT_EQUAL(size_t(4), buffer.Read().size);
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CPPUNIT_ASSERT_EQUAL(&data[4], buffer.Read().data);
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CPPUNIT_ASSERT_EQUAL(true, buffer.Write().IsEmpty());
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/* consume [4..7] */
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/* [OOO....X] */
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buffer.Consume(4);
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CPPUNIT_ASSERT_EQUAL(false, buffer.IsEmpty());
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CPPUNIT_ASSERT_EQUAL(false, buffer.IsFull());
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CPPUNIT_ASSERT_EQUAL(false, buffer.Read().IsEmpty());
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CPPUNIT_ASSERT_EQUAL(size_t(3), buffer.Read().size);
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CPPUNIT_ASSERT_EQUAL(&data[0], buffer.Read().data);
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CPPUNIT_ASSERT_EQUAL(false, buffer.Write().IsEmpty());
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CPPUNIT_ASSERT_EQUAL(&data[3], buffer.Write().data);
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CPPUNIT_ASSERT_EQUAL(size_t(4), buffer.Write().size);
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/* consume [0..2]; after that, we can only write 5,
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because the CircularBuffer class doesn't have
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special code to rewind/reset an empty buffer */
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/* [..X.....] */
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buffer.Consume(3);
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CPPUNIT_ASSERT_EQUAL(true, buffer.IsEmpty());
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CPPUNIT_ASSERT_EQUAL(false, buffer.IsFull());
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CPPUNIT_ASSERT_EQUAL(true, buffer.Read().IsEmpty());
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CPPUNIT_ASSERT_EQUAL(false, buffer.Write().IsEmpty());
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CPPUNIT_ASSERT_EQUAL(&data[3], buffer.Write().data);
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CPPUNIT_ASSERT_EQUAL(size_t(5), buffer.Write().size);
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}
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};
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@ -4,6 +4,7 @@
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#include "config.h"
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#include "util/UriUtil.hxx"
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#include "TestCircularBuffer.hxx"
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#include <cppunit/TestFixture.h>
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#include <cppunit/extensions/TestFactoryRegistry.h>
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@ -50,6 +51,7 @@ public:
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};
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CPPUNIT_TEST_SUITE_REGISTRATION(UriUtilTest);
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CPPUNIT_TEST_SUITE_REGISTRATION(TestCircularBuffer);
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int
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main(gcc_unused int argc, gcc_unused char **argv)
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