util/FifoBuffer: C++ version of the fifo_buffer library

src/util/FifoBuffer.hxx

@@ -0,0 +1,132 @@
+/*
+ * Copyright (C) 2003-2010 Max Kellermann <max@duempel.org>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the
+ * distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
+ * FOUNDATION OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef FIFO_BUFFER_HPP
+#define FIFO_BUFFER_HPP
+
+#include "WritableBuffer.hxx"
+
+#include <utility>
+#include <algorithm>
+
+#include <assert.h>
+#include <stddef.h>
+
+/**
+ * A first-in-first-out buffer: you can append data at the end, and
+ * read data from the beginning.  This class automatically shifts the
+ * buffer as needed.  It is not thread safe.
+ */
+template<class T, size_t size>
+class FifoBuffer {
+public:
+  typedef size_t size_type;
+
+public:
+  typedef WritableBuffer<T> Range;
+
+protected:
+  size_type head, tail;
+  T data[size];
+
+public:
+  constexpr
+  FifoBuffer():head(0), tail(0) {}
+
+protected:
+  void Shift() {
+    if (head == 0)
+      return;
+
+    assert(head <= size);
+    assert(tail <= size);
+    assert(tail >= head);
+
+    std::move(data + head, data + tail, data);
+
+    tail -= head;
+    head = 0;
+  }
+
+public:
+  void Clear() {
+    head = tail = 0;
+  }
+
+  bool IsEmpty() const {
+    return head == tail;
+  }
+
+  bool IsFull() const {
+    return head == 0 && tail == size;
+  }
+
+  /**
+   * Prepares writing.  Returns a buffer range which may be written.
+   * When you are finished, call append().
+   */
+  Range Write() {
+    Shift();
+    return Range(data + tail, size - tail);
+  }
+
+  /**
+   * Expands the tail of the buffer, after data has been written to
+   * the buffer returned by write().
+   */
+  void Append(size_type n) {
+    assert(tail <= size);
+    assert(n <= size);
+    assert(tail + n <= size);
+
+    tail += n;
+  }
+
+  /**
+   * Return a buffer range which may be read.  The buffer pointer is
+   * writable, to allow modifications while parsing.
+   */
+  Range Read() {
+    return Range(data + head, tail - head);
+  }
+
+  /**
+   * Marks a chunk as consumed.
+   */
+  void Consume(size_type n) {
+    assert(tail <= size);
+    assert(head <= tail);
+    assert(n <= tail);
+    assert(head + n <= tail);
+
+    head += n;
+  }
+};
+
+#endif

src/util/WritableBuffer.hxx

@@ -0,0 +1,87 @@
+/*
+ * Copyright (C) 2013 Max Kellermann <max@duempel.org>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the
+ * distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
+ * FOUNDATION OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef WRITABLE_BUFFER_HPP
+#define WRITABLE_BUFFER_HPP
+
+#include "Compiler.h"
+
+#include <stddef.h>
+
+/**
+ * A reference to a memory area that is writable.
+ *
+ * @see ConstBuffer
+ */
+template<typename T>
+struct WritableBuffer {
+  typedef size_t size_type;
+  typedef T *pointer_type;
+  typedef const T *const_pointer_type;
+  typedef pointer_type iterator;
+  typedef const_pointer_type const_iterator;
+
+  pointer_type data;
+  size_type size;
+
+  WritableBuffer() = default;
+
+  constexpr WritableBuffer(pointer_type _data, size_type _size)
+    :data(_data), size(_size) {}
+
+  constexpr static WritableBuffer Null() {
+    return { nullptr, 0 };
+  }
+
+  constexpr bool IsNull() const {
+    return data == nullptr;
+  }
+
+  constexpr bool IsEmpty() const {
+    return size == 0;
+  }
+
+  constexpr iterator begin() const {
+    return data;
+  }
+
+  constexpr iterator end() const {
+    return data + size;
+  }
+
+  constexpr const_iterator cbegin() const {
+    return data;
+  }
+
+  constexpr const_iterator cend() const {
+    return data + size;
+  }
+};
+
+#endif