/****************************************************************************
 * Data Buffer for the Real-time BBC Codec/Modem                            *
 ****************************************************************************
 * William L. Bahn                                                          *
 * Academy Center for Information Security                                  *
 * Department of Computer Science                                           *
 * United States Air Force Academy                                          *
 * USAFA, CO 80840                                                          *
 ****************************************************************************
 * FILE:............ buffer.c                                               *
 * DATE CREATED:.... 01 SEP 07                                              *
 * DATE MODIFIED:... 01 SEP 07                                              *
 ****************************************************************************
 *
 * REVISION HISTORY
 *
 ****************************************************************************
 *
 * DESCRIPTION
 *
 * The data buffer and its programmer interface is described in buffer.h.
 *
 ****************************************************************************
 */

//------------------------------------------------------------------------
// REQUIRED INCLUDES
//------------------------------------------------------------------------

#include <stdlib.h> // malloc(), free()
#include <string.h> // memset()

#include "buffer.h"

//------------------------------------------------------------------------
// STRUCTURE DEFINITIONS
//------------------------------------------------------------------------

// NOTE: Normally the structure definition would be in the *.c file to make 
// the structure members inaccessible to outside functions except through
// public function calls. But for the real-time code it has been decided 
// to make the structure members directly visible to the functions that
// manipulate them.

//------------------------------------------------------------------------
// PRIMITIVE FUNCTION DEFINITIONS
//------------------------------------------------------------------------

//------------------------------------------------------------------------
// PRIVATE FUNCTION DEFINITIONS
//------------------------------------------------------------------------

//------------------------------------------------------------------------
// PUBLIC FUNCTION DEFINITIONS
//------------------------------------------------------------------------

BUFFER *BUFFER_Del(BUFFER *p)
{
	if (p)
	{
		if (p->buffer) { free (p->buffer); p->buffer = NULL;  }
	}
	return NULL;
}

BUFFER *BUFFER_New(CONFIG *c, DWORD *errcode)
{
	BUFFER *p;
	DWORD err;

	p = NULL;
	err = 0;

	if (!err)
	{
		p = (BUFFER *) malloc(sizeof(BUFFER));
		if (!p)
			err |= 1 << 1;
	}

	if (!err)
	{
		p->minsize = (size_t) (c->bufferbytes_per_packet * c->buffer_packets);
		p->size = 1;
		while ((0 != p->size)&&(p->size < p->minsize))
			p->size <<= 1;
		if (0 == p->size)
			err |= 1 << 2;
	}

	if (!err)
	{
		// Allocate buffer memory
		p->buffer = (BYTE *) malloc(p->size*sizeof(BYTE));
		if (!p->buffer)
			err |= 1 << 3;

		// Initialize buffer state

		// Common to TX and RX
		p->buffermask = p->size - 1;
		p->scope = c->bufferbytes_per_packet;
		p->read = 0;
		p->write = 0;
		p->overflows = 0;

		// TX and RX specific
		if (c->scheduler_TX_notRX)
		{
			p->margin = p->size - p->scope;
			p->ready = 0;
			p->empty = 0; // Not used
		}
		else
		{
			p->margin = -((SDWORD)p->scope);
			p->ready = 0; // Not used
			p->empty = p->size;
		}
	}

	// Clear entire buffer
	if (!err)
		memset(p->buffer, 0, p->size);

	if (err)
		p = BUFFER_Del(p);

	if (c->diagnostics)
	{
		// Diagnostic Report
		printf("------------------------------------------\n");
		printf("PACKET BUFFER\n");
		printf("  Creation:............... %s\n", ((err)? "FAILED":"SUCCEEDED"));
		printf("  Location:............... %p\n", (void *) p);
		printf("  Minimum buffer size:.... %lu bytes\n", (unsigned long) p->minsize);
		printf("  Buffer size:............ %lu bytes\n", (unsigned long) p->size);
		printf("  Buffer location:........ %p\n", (void *) p->buffer);
		printf("  Packet size in buffer:.. %lu bytes\n", (unsigned long) p->scope);
		printf("  read:................... %lu bytes\n", (unsigned long) p->read);
		printf("  write:.................. %lu bytes\n", (unsigned long) p->write);
		printf("  empty:.................. %lu bytes\n", (unsigned long) p->empty);
		printf("  ready:.................. %lu bytes\n", (unsigned long) p->ready);
		printf("  margin:................. %li bytes\n", (long) p->margin);
		printf("  overflows:.............. %lu bytes\n", (unsigned long) p->overflows);
		printf("------------------------------------------\n");
	}

	*errcode = err;
	return p;
}

//------------------------------------------------------------------------