g.USBamp_Linux/GUSBamp_Driver/Queue.h

#pragma once

#if defined TARGET_HAS_ThirdPartyGUSBampCAPI_Linux

#include <stdint.h>
#include <string.h>

#ifndef MIN
#define MIN(a, b) (((a) < (b)) ? (a) : (b))
#endif

#ifndef MAX
#define MAX(a, b) (((a) > (b)) ? (a) : (b))
#endif

template <class T>
class Queue
{
	T* buffer = nullptr;
	int head  = 0, tail = 0, size = 0;

public:
	Queue() { }

	Queue(T* array, const int len)
	{
		size   = len;
		buffer = array;
	}

	void SetBuffer(T* array, const int len)
	{
		size   = len;
		head   = tail = 0;
		buffer = array;
	}

	int Get(T* elements, int len)
	{
		// Trim the length if necessary to only as large as the number of available elements in the buffer
		len = MIN(len, Avail());

		int nonwrapped    = MIN((size - tail), len);
		const int wrapped = len - nonwrapped;

		// memcpy the data starting at the head all the way up to the last element *(storage - 1)
		memcpy(elements, (buffer + tail), nonwrapped * sizeof(T));

		// If there's still data to copy memcpy whatever remains, starting at the first element *(begin) until the end of data. The first step will have ensured
		// that we don't crash into the tail during this process.
		memcpy((elements + nonwrapped), buffer, wrapped * sizeof(T));

		// Recalculate head
		tail = (tail + nonwrapped + wrapped) % size;

		return len;
	}

	// Returns the number of bytes actually placed in the array
	int Put(const T* elements, int len)
	{
		// Trim the length if necessary to only as large as the nuber of free elements in the buffer
		len = MIN(len, Free());

		// Figure out how much to append to the end of the buffer and how much will overlap onto the start
		int nonwrapped    = MIN((size - head), len);
		const int wrapped = len - nonwrapped;

		// memcpy the data starting at the head all the way up to the last element *(storage - 1)
		memcpy((buffer + head), elements, nonwrapped * sizeof(T));

		// If there's still data to copy memcpy whatever remains onto the beginning of the array
		memcpy(buffer, (elements + nonwrapped), wrapped * sizeof(T));

		// Re-recalculate head
		head = (head + nonwrapped + wrapped) % size;

		return len;
	}

	// Expand the size of queue without actually modifying any of the contents - useful for copying directly onto the queu buffer
	int Pad(int len)
	{
		// Trim the length if necessary to only as large as the nuber of free elements in the buffer
		len = MIN(len, Free());

		// Figure out how much to append to the end of the buffer and how much will overlap onto the start
		const int nonwrapped = MIN((size - head), len), wrapped = len - nonwrapped;

		// Re-recalculate head
		head = (head + nonwrapped + wrapped) % size;

		return len;
	}

	// Removes the oldest entry from the Queue
	void Pop() { if (Avail()) tail = (tail + 1) % size; }

	// Returns the oldest element in the array (the one added before any other)
	T& Tail() { return buffer[tail]; }

	// Returns the newest element in the array (the one added after every other)
	T& Head() { return buffer[(head + size - 1) % size]; }

	T& operator[](int n) { return buffer[tail + n % size]; }

	void Clear() { head = tail = 0; }

	int Avail() const { return (size + head - tail) % size; }

	int Free() const { return (size - 1 - Avail()); }

	// Gets the number of free elements that can be stored contiguously
	int FreeContiguous() { return head < tail ? tail - head - 1 : MIN(size - head, Free()); }

	// Gets a pointer to the next free address in the buffer
	T* NextFreeAddress() { return buffer + head; }
};

#endif // TARGET_HAS_ThirdPartyGUSBampCAPI_Linux