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bertos/struct/fifobuf.h

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+/**
+ * \file
+ * <!--
+ * This file is part of BeRTOS.
+ *
+ * Bertos is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ *
+ * As a special exception, you may use this file as part of a free software
+ * library without restriction.  Specifically, if other files instantiate
+ * templates or use macros or inline functions from this file, or you compile
+ * this file and link it with other files to produce an executable, this
+ * file does not by itself cause the resulting executable to be covered by
+ * the GNU General Public License.  This exception does not however
+ * invalidate any other reasons why the executable file might be covered by
+ * the GNU General Public License.
+ *
+ * Copyright 2003, 2004 Develer S.r.l. (http://www.develer.com/)
+ * Copyright 2001, 2008 Bernie Innocenti <bernie@codewiz.org>
+ * -->
+ *
+ * \defgroup fifobuf FIFO buffer
+ * \ingroup struct
+ * \{
+ *
+ * \brief General pourpose FIFO buffer implemented with a ring buffer
+ *
+ * \li \c begin points to the first buffer element;
+ * \li \c end points to the last buffer element (unlike the STL convention);
+ * \li \c head points to the element to be extracted next;
+ * \li \c tail points to the location following the last insertion;
+ * \li when any of the pointers advances beyond \c end, it is reset
+ *     back to \c begin.
+ *
+ * \code
+ *
+ *  +-----------------------------------+
+ *  |  empty  |   valid data   |  empty |
+ *  +-----------------------------------+
+ *  ^         ^                ^        ^
+ *  begin    head             tail     end
+ *
+ * \endcode
+ *
+ * The buffer is EMPTY when \c head and \c tail point to the same location:
+ *		\code head == tail \endcode
+ *
+ * The buffer is FULL when \c tail points to the location immediately
+ * after \c head:
+ *		\code tail == head - 1 \endcode
+ *
+ * The buffer is also FULL when \c tail points to the last buffer
+ * location and head points to the first one:
+ *		\code head == begin && tail == end \endcode
+ *
+ * \author Bernie Innocenti <bernie@codewiz.org>
+ */
+
+#ifndef STRUCT_FIFO_H
+#define STRUCT_FIFO_H
+
+#include <cpu/types.h>
+#include <cpu/irq.h>
+#include <cfg/debug.h>
+
+typedef struct FIFOBuffer
+{
+	unsigned char * volatile head;
+	unsigned char * volatile tail;
+	unsigned char *begin;
+	unsigned char *end;
+} FIFOBuffer;
+
+
+#define ASSERT_VALID_FIFO(fifo) \
+	ATOMIC( \
+		ASSERT((fifo)->head >= (fifo)->begin); \
+		ASSERT((fifo)->head <= (fifo)->end); \
+		ASSERT((fifo)->tail >= (fifo)->begin); \
+		ASSERT((fifo)->tail <= (fifo)->end); \
+	)
+
+
+/**
+ * Check whether the fifo is empty
+ *
+ * \note Calling fifo_isempty() is safe while a concurrent
+ *       execution context is calling fifo_push() or fifo_pop()
+ *       only if the CPU can atomically update a pointer
+ *       (which the AVR and other 8-bit processors can't do).
+ *
+ * \sa fifo_isempty_locked
+ */
+INLINE bool fifo_isempty(const FIFOBuffer *fb)
+{
+	//ASSERT_VALID_FIFO(fb);
+	return fb->head == fb->tail;
+}
+
+
+/**
+ * Check whether the fifo is full
+ *
+ * \note Calling fifo_isfull() is safe while a concurrent
+ *       execution context is calling fifo_pop() and the
+ *       CPU can update a pointer atomically.
+ *       It is NOT safe when the other context calls
+ *       fifo_push().
+ *       This limitation is not usually problematic in a
+ *       consumer/producer scenario because the
+ *       fifo_isfull() and fifo_push() are usually called
+ *       in the producer context.
+ */
+INLINE bool fifo_isfull(const FIFOBuffer *fb)
+{
+	//ASSERT_VALID_FIFO(fb);
+	return
+		((fb->head == fb->begin) && (fb->tail == fb->end))
+		|| (fb->tail == fb->head - 1);
+}
+
+
+/**
+ * Push a character on the fifo buffer.
+ *
+ * \note Calling \c fifo_push() on a full buffer is undefined.
+ *       The caller must make sure the buffer has at least
+ *       one free slot before calling this function.
+ *
+ * \note It is safe to call fifo_pop() and fifo_push() from
+ *       concurrent contexts, unless the CPU can't update
+ *       a pointer atomically (which the AVR and other 8-bit
+ *       processors can't do).
+ *
+ * \sa fifo_push_locked
+ */
+INLINE void fifo_push(FIFOBuffer *fb, unsigned char c)
+{
+#ifdef __MWERKS__
+#pragma interrupt called
+#endif
+	//ASSERT_VALID_FIFO(fb);
+
+	/* Write at tail position */
+	*(fb->tail) = c;
+
+	if (UNLIKELY(fb->tail == fb->end))
+		/* wrap tail around */
+		fb->tail = fb->begin;
+	else
+		/* Move tail forward */
+		fb->tail++;
+}
+
+
+/**
+ * Pop a character from the fifo buffer.
+ *
+ * \note Calling \c fifo_pop() on an empty buffer is undefined.
+ *       The caller must make sure the buffer contains at least
+ *       one character before calling this function.
+ *
+ * \note It is safe to call fifo_pop() and fifo_push() from
+ *       concurrent contexts.
+ */
+INLINE unsigned char fifo_pop(FIFOBuffer *fb)
+{
+#ifdef __MWERKS__
+#pragma interrupt called
+#endif
+	//ASSERT_VALID_FIFO(fb);
+
+	if (UNLIKELY(fb->head == fb->end))
+	{
+		/* wrap head around */
+		fb->head = fb->begin;
+		return *(fb->end);
+	}
+	else
+		/* move head forward */
+		return *(fb->head++);
+}
+
+
+/**
+ * Make the fifo empty, discarding all its current contents.
+ */
+INLINE void fifo_flush(FIFOBuffer *fb)
+{
+	//ASSERT_VALID_FIFO(fb);
+	fb->head = fb->tail;
+}
+
+
+#if CPU_REG_BITS >= CPU_BITS_PER_PTR
+
+	/*
+	 * 16/32bit CPUs that can update a pointer with a single write
+	 * operation, no need to disable interrupts.
+	 */
+	#define fifo_isempty_locked(fb) fifo_isempty((fb))
+	#define fifo_push_locked(fb, c) fifo_push((fb), (c))
+	#define fifo_pop_locked(fb)     fifo_pop((fb))
+	#define fifo_flush_locked(fb)   fifo_flush((fb))
+
+#else /* CPU_REG_BITS < CPU_BITS_PER_PTR */
+
+	/**
+	 * Similar to fifo_isempty(), but with stronger guarantees for
+	 * concurrent access between user and interrupt code.
+	 *
+	 * \note This is actually only needed for 8-bit processors.
+	 *
+	 * \sa fifo_isempty()
+	 */
+	INLINE bool fifo_isempty_locked(const FIFOBuffer *fb)
+	{
+		bool result;
+		ATOMIC(result = fifo_isempty(fb));
+		return result;
+	}
+
+
+	/**
+	 * Similar to fifo_push(), but with stronger guarantees for
+	 * concurrent access between user and interrupt code.
+	 *
+	 * \note This is actually only needed for 8-bit processors.
+	 *
+	 * \sa fifo_push()
+	 */
+	INLINE void fifo_push_locked(FIFOBuffer *fb, unsigned char c)
+	{
+		ATOMIC(fifo_push(fb, c));
+	}
+
+	/* Probably not really needed, but hard to prove. */
+	INLINE unsigned char fifo_pop_locked(FIFOBuffer *fb)
+	{
+		unsigned char c;
+		ATOMIC(c = fifo_pop(fb));
+		return c;
+	}
+
+	/**
+	 * Similar to fifo_flush(), but with stronger guarantees for
+	 * concurrent access between user and interrupt code.
+	 *
+	 * \note This is actually only needed for 8-bit processors.
+	 *
+	 * \sa fifo_flush()
+	 */
+	INLINE void fifo_flush_locked(FIFOBuffer *fb)
+	{
+		ATOMIC(fifo_flush(fb));
+	}
+
+#endif /* CPU_REG_BITS < BITS_PER_PTR */
+
+
+/**
+ * Thread safe version of fifo_isfull()
+ */
+INLINE bool fifo_isfull_locked(const FIFOBuffer *_fb)
+{
+	bool result;
+	ATOMIC(result = fifo_isfull(_fb));
+	return result;
+}
+
+
+/**
+ * FIFO Initialization.
+ */
+INLINE void fifo_init(FIFOBuffer *fb, unsigned char *buf, size_t size)
+{
+	/* FIFO buffers have a known bug with 1-byte buffers. */
+	ASSERT(size > 1);
+
+	fb->head = fb->tail = fb->begin = buf;
+	fb->end = buf + size - 1;
+}
+
+/**
+ * \return Lenght of the FIFOBuffer \a fb.
+ */
+INLINE size_t fifo_len(FIFOBuffer *fb)
+{
+	return fb->end - fb->begin;
+}
+
+
+#if 0
+
+/*
+ * UNTESTED: if uncommented, to be moved in fifobuf.c
+ */
+void fifo_pushblock(FIFOBuffer *fb, unsigned char *block, size_t len)
+{
+	size_t freelen;
+
+	/* Se c'e' spazio da tail alla fine del buffer */
+	if (fb->tail >= fb->head)
+	{
+		freelen = fb->end - fb->tail + 1;
+
+		/* C'e' abbastanza spazio per scrivere tutto il blocco? */
+		if (freelen < len)
+		{
+			/* Scrivi quello che entra fino alla fine del buffer */
+			memcpy(fb->tail, block, freelen);
+			block += freelen;
+			len -= freelen;
+			fb->tail = fb->begin;
+		}
+		else
+		{
+			/* Scrivi tutto il blocco */
+			memcpy(fb->tail, block, len);
+			fb->tail += len;
+			return;
+		}
+	}
+
+	for(;;)
+	{
+		while (!(freelen = fb->head - fb->tail - 1))
+			Delay(FIFO_POLLDELAY);
+
+		/* C'e' abbastanza spazio per scrivere tutto il blocco? */
+		if (freelen < len)
+		{
+			/* Scrivi quello che entra fino alla fine del buffer */
+			memcpy(fb->tail, block, freelen);
+			block += freelen;
+			len -= freelen;
+			fb->tail += freelen;
+		}
+		else
+		{
+			/* Scrivi tutto il blocco */
+			memcpy(fb->tail, block, len);
+			fb->tail += len;
+			return;
+		}
+	}
+}
+#endif
+
+/** \} */ /* defgroup fifobuf */
+
+#endif /* STRUCT_FIFO_H */