nuttx/drivers/bch/bchlib_write.c

/****************************************************************************
 * drivers/bch/bchlib_write.c
 *
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.  The
 * ASF licenses this file to you 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.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <nuttx/config.h>

#include <sys/types.h>
#include <stdint.h>
#include <stdbool.h>
#include <string.h>
#include <errno.h>
#include <assert.h>
#include <debug.h>

#include <nuttx/fs/fs.h>

#include "bch.h"

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/****************************************************************************
 * Name: bchlib_write
 *
 * Description:
 *   Write to the block device set-up by bchlib_setup as if it were a
 *   character device.
 *
 ****************************************************************************/

ssize_t bchlib_write(FAR void *handle, FAR const char *buffer, size_t offset,
        size_t len)
{
  FAR struct bchlib_s *bch = (FAR struct bchlib_s *)handle;
  size_t   nsectors;
  size_t   sector;
  uint16_t sectoffset;
  size_t   nbytes;
  size_t   byteswritten;
  int      ret;

  /* Get rid of this special case right away */

  if (len < 1)
    {
      return 0;
    }

  /* Convert the file position into a sector number and offset. */

  sector     = offset / bch->sectsize;
  sectoffset = offset - sector * bch->sectsize;

  if (sector >= bch->nsectors)
    {
      return -EFBIG;
    }

  /* Write the initial partial sector */

  byteswritten = 0;
  if (sectoffset > 0)
    {
      /* Read the full sector into the sector buffer */

      bchlib_readsector(bch, sector);

      /* Copy the tail end of the sector from the user buffer */

      if (sectoffset + len > bch->sectsize)
        {
          nbytes = bch->sectsize - sectoffset;
        }
      else
        {
          nbytes = len;
        }

      memcpy(&bch->buffer[sectoffset], buffer, nbytes);
      bch->dirty = true;

      /* Adjust pointers and counts */

      sector++;

      if (sector >= bch->nsectors)
        {
          return nbytes;
        }

      byteswritten  = nbytes;
      buffer       += nbytes;
      len          -= nbytes;
    }

  /* Then write all of the full sectors following the partial sector
   * directly from the user buffer.
   */

  if (len >= bch->sectsize)
    {
      nsectors = len / bch->sectsize;
      if (sector + nsectors > bch->nsectors)
        {
          nsectors = bch->nsectors - sector;
        }

      /* Flush the dirty sector to keep the sector sequence */

      ret = bchlib_flushsector(bch);
      if (ret < 0)
        {
          ferr("ERROR: Flush failed: %d\n", ret);
          return ret;
        }

      /* Write the contiguous sectors */

      ret = bch->inode->u.i_bops->write(bch->inode, (FAR uint8_t *)buffer,
                                        sector, nsectors);
      if (ret < 0)
        {
          ferr("ERROR: Write failed: %d\n", ret);
          return ret;
        }

      /* Adjust pointers and counts */

      sector       += nsectors;
      nbytes        = nsectors * bch->sectsize;
      byteswritten += nbytes;

      if (sector >= bch->nsectors)
        {
          return byteswritten;
        }

      buffer    += nbytes;
      len       -= nbytes;
    }

  /* Then write any partial final sector */

  if (len > 0)
    {
      /* Read the sector into the sector buffer */

      bchlib_readsector(bch, sector);

      /* Copy the head end of the sector from the user buffer */

      memcpy(bch->buffer, buffer, len);
      bch->dirty = true;

      /* Adjust counts */

      byteswritten += len;
    }

  return byteswritten;
}