source: trunk/kernel/kern/mwmr.c @ 15

/*
 * kern/mwmr.c - a basic FIFO buffer
 * 
 * Copyright (c) 2007,2008,2009,2010,2011,2012 Ghassan Almaless
 * Copyright (c) 2011,2012 UPMC Sorbonne Universites
 *
 * This file is part of ALMOS-kernel.
 *
 * ALMOS-kernel 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; version 2.0 of the License.
 *
 * ALMOS-kernel 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 ALMOS-kernel; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include <errno.h>
#include <mwmr.h>
#include <kmem.h>
#include <thread.h>
#include <spinlock.h>

struct fifomwmr_s
{
        spinlock_t lock;
        uint_t isAtomic;
        uint_t status;
        uint_t read_ptr;
        uint_t write_ptr;
        char *data;
        uint_t item;
        uint_t length;
};

struct fifomwmr_s* mwmr_init(int item, int length, int isAtomic)
{
        kmem_req_t req;
        struct fifomwmr_s *fifo;
        char *data;

        req.type  = KMEM_GENERIC;
        req.size  = sizeof(*fifo);
        req.flags = AF_BOOT | AF_ZERO;
  
        if((fifo = kmem_alloc(&req)) == NULL)
                return NULL;
  
        req.size = sizeof (unsigned int) * item * length;

        if((data = kmem_alloc(&req)) == NULL)
        {
                printk(WARNING, "WARNING: mwmr_init: MEMORY SHORTAGE\n");
                req.ptr = fifo;
                kmem_free(&req);
                return NULL;
        }

        spinlock_init(&fifo->lock, "MWMR");
        fifo->isAtomic = isAtomic;
        fifo->item     = item;
        fifo->length   = length * item;
        fifo->data     = data;
  
        return fifo;
}

int mwmr_read(struct fifomwmr_s *fifo, void *buffer, size_t size)
{
        register int rnum;                    // number of words to read
        register char *src;
        register int i, size1, size2;
        register char *buff = (char *) buffer;

        if (size == 0)
                return 0;

        if(fifo->isAtomic)
                spinlock_lock(&fifo->lock);

        rnum = (size > fifo->status) ? fifo->status : size;

        if (rnum)
        {
                src = fifo->data + fifo->read_ptr;
                if ((fifo->read_ptr + rnum) <= fifo->length)
                        for (i = 0; i < rnum; i++)
                                buff[i] = src[i];
                else
                {
                        size1 = fifo->length - fifo->read_ptr;
                        size2 = rnum - size1;

                        for (i = 0; i < size1; i++)
                                buff[i] = src[i];

                        for (i = 0; i < size2; i++)
                                buff[size1 + i] = *(fifo->data + i);
                }

                fifo->status  -= rnum;
                fifo->read_ptr = (fifo->read_ptr + rnum) % fifo->length;
        }

        if(fifo->isAtomic)
                spinlock_unlock(&fifo->lock);

        return rnum;
}

int mwmr_write(struct fifomwmr_s *fifo, void *buffer, size_t size)
{
        register int free_space;
        register int wnum;                    // number of words to write
        register char *dest;
        register int i, size1, size2;
        register char *buff = (char *) buffer;

        if (size == 0)
                return 0;

        if(fifo->isAtomic)
                spinlock_lock (&fifo->lock);

        free_space = fifo->length - fifo->status;
        wnum       = (size > free_space) ? free_space : size;

        if (wnum)
        {
                dest = (fifo->data + fifo->write_ptr);

                if ((fifo->write_ptr + wnum) <= fifo->length)
                        for (i = 0; i < wnum; i++)
                                dest[i] = buff[i];
                else
                {
                        size1 = fifo->length - fifo->write_ptr;
                        size2 = wnum - size1;

                        for (i = 0; i < size1; i++)
                                dest[i] = buff[i];

                        for (i = 0; i < size2; i++)
                                *(fifo->data + i) = buff[size1 + i];
                }

                fifo->status += wnum;
                fifo->write_ptr = (fifo->write_ptr + wnum) % fifo->length;
        }

        if(fifo->isAtomic)
                spinlock_unlock(&fifo->lock);

        return wnum;
}

void mwmr_destroy(struct fifomwmr_s *fifo)
{
        kmem_req_t req;
  
        if(fifo == NULL) return;

        req.type = KMEM_GENERIC;
        req.ptr  = fifo->data;
        kmem_free(&req);
  
        req.ptr  = fifo;
        kmem_free(&req);
}