Add circular byte buffer using dynamic memory

Add the ByteBuffer class which is similar to the CircularBuffer class
but uses dynamic memory rather than template parameters and is
optimized for byte transfers. This is required for USBAudio which
needs a high performance circular buffer which can be resized at
runtime.

usb/device/utilities/ByteBuffer.cpp

@@ -0,0 +1,151 @@
+/* mbed Microcontroller Library
+ * Copyright (c) 2018-2018 ARM Limited
+ *
+ * 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
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "ByteBuffer.h"
+#include "mbed_assert.h"
+#include <string.h>
+
+ByteBuffer::ByteBuffer(uint32_t size): _head(0), _tail(0), _size(0), _buf(NULL)
+{
+    resize(_size);
+}
+
+ByteBuffer::~ByteBuffer()
+{
+    delete[] _buf;
+    _buf = 0;
+}
+
+void ByteBuffer::resize(uint32_t size)
+{
+    delete[] _buf;
+    _head = 0;
+    _tail = 0;
+    _size = size + 1;
+    _buf = new uint8_t[_size]();
+}
+
+void ByteBuffer::push(uint8_t data)
+{
+    _buf[_tail] = data;
+    _tail++;
+    if (_tail >= _size) {
+        _tail -= _size;
+    }
+    // Overflow not allowed
+    MBED_ASSERT(_head != _tail);
+}
+
+void ByteBuffer::write(uint8_t *data, uint32_t size)
+{
+    MBED_ASSERT(size <= free());
+
+    if (size == 0) {
+        return;
+    }
+
+    uint32_t new_tail = _tail + size;
+    if (new_tail >= _size) {
+        new_tail -= _size;
+    }
+
+    // Perform first memcpy
+    uint32_t until_end = _size - _tail;
+    uint32_t copy_size = until_end < size ? until_end : size;
+    memcpy(_buf + _tail, data, copy_size);
+    data += copy_size;
+    size -= copy_size;
+
+    // Perform second memcpy
+    if (size > 0) {
+        memcpy(_buf, data, size);
+    }
+
+    // Update tail
+    _tail = new_tail;
+}
+
+uint8_t ByteBuffer::pop()
+{
+    // Underflow not allowed
+    MBED_ASSERT(_head != _tail);
+    uint8_t val = _buf[_head];
+    _head++;
+    if (_head >= _size) {
+        _head -= _size;
+    }
+    return val;
+}
+
+void ByteBuffer::read(uint8_t *data, uint32_t size)
+{
+    MBED_ASSERT(size <= ByteBuffer::size());
+
+    if (size == 0) {
+        return;
+    }
+
+    uint32_t new_head = _head + size;
+    if (new_head >= _size) {
+        new_head -= _size;
+    }
+
+    // Perform first memcpy
+    uint32_t until_end = _size - _head;
+    uint32_t copy_size = until_end < size ? until_end : size;
+    memcpy(data, _buf + _head, copy_size);
+    data += copy_size;
+    size -= copy_size;
+
+    // Perform second memcpy
+    if (size > 0) {
+        memcpy(data, _buf, size);
+    }
+
+    // Update head
+    _head = new_head;
+}
+
+uint32_t ByteBuffer::size()
+{
+    uint32_t size;
+    if (_tail < _head) {
+        size = _size + _tail - _head;
+    } else {
+        size = _tail - _head;
+    }
+    return size;
+}
+
+uint32_t ByteBuffer::free()
+{
+    return _size - size() - 1;
+}
+
+bool ByteBuffer::full()
+{
+    uint32_t next = _tail + 1;
+    if (next >= _size) {
+        next -= _size;
+    }
+    return next == _head;
+}
+
+bool ByteBuffer::empty()
+{
+    return _head == _tail;
+}
+

usb/device/utilities/ByteBuffer.h

@@ -0,0 +1,119 @@
+/* mbed Microcontroller Library
+ * Copyright (c) 2018-2018 ARM Limited
+ *
+ * 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
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef BYTE_BUFFER_H
+#define BYTE_BUFFER_H
+
+#include <stdint.h>
+
+class ByteBuffer {
+public:
+
+    /**
+     * Create a byte buffer of the given size
+     *
+     * @param size Number of bytes this buffer can hold
+     */
+    ByteBuffer(uint32_t size=0);
+
+    /**
+     * Delete this byte buffer
+     */
+    ~ByteBuffer();
+
+    /**
+     * Set the size of the buffer
+     *
+     * Buffer contents are reset.
+     *
+     * @param size New buffer size
+     */
+    void resize(uint32_t size);
+
+    /**
+     * Add a single byte to this buffer
+     *
+     * There must be enough space in the buffer or the behavior is undefined.
+     *
+     * @param data byte to add
+     */
+    void push(uint8_t data);
+
+    /**
+     * Write a block of data to this ByteBuffer
+     *
+     * There must be enough space in the ByteBuffer or the behavior is undefined.
+     *
+     * @param data Block of data to write
+     * @param size Size of data to write
+     */
+    void write(uint8_t *data, uint32_t size);
+
+    /**
+     * Remove a byte from this buffer
+     *
+     * @return data byte
+     */
+    uint8_t pop();
+
+    /**
+     * Read a block of data from this ByteBuffer into a buffer pointed by 'data'
+     *
+     * There must be enough data in the ByteBuffer or the behavior is undefined.
+     *
+     * @param data Block of data to read
+     * @param size Size of data to read
+     */
+    void read(uint8_t *data, uint32_t size);
+
+    /**
+     * Return the number bytes in this byte buffer
+     *
+     * @return Number of used bytes
+     */
+    uint32_t size();
+
+    /**
+     * Return the number of additional bytes this buffer can hold
+     *
+     * @return Number of free bytes
+     */
+    uint32_t free();
+
+    /**
+     * Check if this byte buffer is full
+     *
+     * @return true if full, false otherwise
+     */
+    bool full();
+
+    /**
+     * Check if this byte buffer is empty
+     *
+     * @return true if empty, false otherwise
+     */
+    bool empty();
+
+private:
+
+    uint32_t _head;
+    uint32_t _tail;
+    uint32_t _size;
+    uint8_t *_buf;
+};
+
+
+#endif