/****************************************************************************
 * mm/mm_gran/mm_graninfo.c
 *
 * SPDX-License-Identifier: Apache-2.0
 *
 * 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 <assert.h>
#include <errno.h>

#include <nuttx/mm/gran.h>

#include "mm_gran/mm_gran.h"

#ifdef CONFIG_GRAN

/****************************************************************************
 * Private Data
 ****************************************************************************/

struct nibble_info_s
{
  uint16_t nfree   : 4; /* Total bits free in a nibble */
  uint16_t nlsfree : 4; /* Total contiguous LS bits free */
  uint16_t nmsfree : 4; /* Total contiguous MS bits free */
  uint16_t mxfree  : 4; /* Largest internal contiguous bits free */
};

struct valinfo_s
{
  uint8_t nfree;        /* Total bits free in the byte/hword */
  uint8_t nlsfree;      /* Total contiguous LS bits free */
  uint8_t nmsfree;      /* Total contiguous MS bits free */
  uint8_t mxfree;       /* Largest internal contiguous bits free */
};

/****************************************************************************
 * Private Data
 ****************************************************************************/

static const struct nibble_info_s g_0bit_info[1] =
{
  {               /*  0 xxxx */
    0, 0, 0, 0
  }
};

static const struct nibble_info_s g_1bit_info[2] =
{
  {               /*  0 xxx0 */
    1, 1, 0, 0
  },
  {               /*  1 xxx1 */
    0, 0, 0, 0
  }
};

static const struct nibble_info_s g_2bit_info[4] =
{
  {               /*  0 xx00 */
    2, 2, 0, 0
  },
  {               /*  1 xx01 */
    1, 0, 1, 0
  },
  {               /*  2 xx10 */
    1, 1, 0, 0
  },
  {               /*  3 xx11 */
    0, 0, 0, 0
  }
};

static const struct nibble_info_s g_3bit_info[8] =
{
  {               /*  0 x000 */
    3, 3, 0, 0
  },
  {               /*  1 x001 */
    2, 0, 2, 0
  },
  {               /*  2 x010 */
    2, 1, 1, 0
  },
  {               /*  3 x011 */
    1, 0, 1, 0
  },
  {               /*  4 x100 */
    2, 2, 0, 0
  },
  {               /*  5 x101 */
    1, 0, 0, 1
  },
  {               /*  6 x110 */
    1, 1, 0, 0
  },
  {               /*  7 x111 */
    0, 0, 0, 0
  }
};

static const struct nibble_info_s g_4bit_info[16] =
{
  {               /*  0 0000 */
    4, 4, 0, 0
  },
  {               /*  1 0001 */
    3, 0, 3, 0
  },
  {               /*  2 0010 */
    3, 1, 2, 0
  },
  {               /*  3 0011 */
    2, 0, 2, 0
  },
  {               /*  4 0100 */
    3, 2, 1, 0
  },
  {               /*  5 0101 */
    2, 0, 1, 1
  },
  {               /*  6 0110 */
    2, 1, 1, 0
  },
  {               /*  7 0111 */
    1, 0, 1, 0
  },
  {               /*  8 1000 */
    3, 3, 0, 0
  },
  {               /*  9 1001 */
    2, 0, 0, 2
  },
  {               /* 10 1010 */
    2, 1, 0, 1
  },
  {               /* 11 1011 */
    1, 0, 0, 1
  },
  {               /* 12 1100 */
    2, 2, 0, 0
  },
  {               /* 13 1101 */
    1, 0, 0, 1
  },
  {               /* 14 1110 */
    1, 1, 0, 0
  },
  {               /* 15 1111 */
    0, 0, 0, 0
  }
};

static const struct nibble_info_s *g_info_table[5] =
{
  g_0bit_info,
  g_1bit_info,
  g_2bit_info,
  g_3bit_info,
  g_4bit_info
};

/****************************************************************************
 * Private Functions
 ****************************************************************************/

/****************************************************************************
 * Name: gran_nibble_info
 *
 * Description:
 *   Return information for a 4-bit value from the GAT.
 *
 * Input Parameters:
 *   value - The 4-bit value
 *   info  - The location to return the hword info
 *   nbits - Number of valid bits in value
 *
 * Returned Value:
 *   None
 *
 ****************************************************************************/

static void gran_nibble_info(uint8_t value, FAR struct valinfo_s *info,
                             unsigned int nbits)
{
  FAR const struct nibble_info_s *table = g_info_table[nbits];
  FAR const struct nibble_info_s *nibinfo;
  uint8_t mask;

  /* Look up the table entry */

  mask          = ((1 << nbits) - 1);
  value        &= mask;
  nibinfo       = &table[value];

  /* Return expanded values */

  info->nfree   = nibinfo->nfree;
  info->nlsfree = nibinfo->nlsfree;
  info->nmsfree = nibinfo->nmsfree;
  info->mxfree  = nibinfo->mxfree;
}

/****************************************************************************
 * Name: gran_info_combine
 *
 * Description:
 *   Combine new MS bit information with existing LS bit information.
 *
 * Input Parameters:
 *   msinfo - The new MS bit information
 *   msbits - Number of bits in MS piece
 *   lsinfo - The existing LS bit information
 *
 * Returned Value:
 *   None
 *
 ****************************************************************************/

static void gran_info_combine(FAR const struct valinfo_s *msinfo,
                              unsigned int msbits,
                              FAR struct valinfo_s *lsinfo,
                              unsigned int lsbits)
{
  unsigned int midfree;

  /* Is there a region of free space isolated in the middle of the two
   * pieces?
   */

  if (lsinfo->nlsfree < lsbits && msinfo->nlsfree < msbits)
    {
      /* Yes... combine the MS free bits from the LS piece with the
       * LS free bits from the MS piece.
       */

      midfree = lsinfo->nmsfree + msinfo->nlsfree;
    }
  else
    {
      midfree = 0;
    }

  /* Update the total number of free bits in the combined pieces */

  lsinfo->nfree += msinfo->nfree;

  /* Figure out how many MS bits will now be free.  First, is the MS piece
   * all free?
   */

  if (msinfo->nlsfree == msbits)
    {
      /* Yes.. is the LS piece also all free bits? */

      if (lsinfo->nlsfree == lsbits)
        {
          /* Yes.. the there are no MS free bits (only LS) */

          lsinfo->nmsfree = 0;
        }
      else
        {
          /* No.. then combine all of the bits from the MS piece with the
           * MS bits of the LS piece.
           */

          lsinfo->nmsfree += msbits;
        }
    }
  else
    {
      /* No.. then just replace the MS bits of the LS piece with the MS
       * bits from the new MS piece.
       */

      lsinfo->nmsfree = msinfo->nmsfree;
    }

  /* Figure out how many LS bits will now be free.  First, is the LS piece
   * all free?
   */

  if (lsinfo->nlsfree == lsbits)
    {
      /* Yes.. then combine all of the bits from the LS piece with the
       * LS bits of the MS piece.
       */

      lsinfo->nlsfree += msinfo->nlsfree;
    }

  /* Now, what is the longest internal sequence of the free bits?  It might
   * be original sequence of free bits in the LS piece.  Or it might the
   * section of middle bits that got above.
   */

  if (midfree > lsinfo->mxfree)
    {
      lsinfo->mxfree = midfree;
    }

  /* Or it might the section of middle bits in the new MS piece */

  if (msinfo->mxfree > lsinfo->mxfree)
    {
      lsinfo->mxfree = msinfo->mxfree;
    }
}

/****************************************************************************
 * Name: gran_byte_info
 *
 * Description:
 *   Return information a 8-bit value from the GAT.
 *
 * Input Parameters:
 *   value - The 16-bit value
 *   info  - The location to return the hword info
 *   nbits - Number of valid bits in value
 *
 * Returned Value:
 *   None
 *
 ****************************************************************************/

static void gran_byte_info(uint8_t value, FAR struct valinfo_s *info,
                           unsigned int nbits)
{
  uint8_t mask;

  if (nbits < 8)
    {
      mask   = ((1 << nbits) - 1);
      value &= mask;
    }
  else
    {
      mask = 0xff;
    }

  /* Handle special cases */

  if (value == 0)
    {
      /* All free */

      info->nfree   = nbits;
      info->nlsfree = nbits;
      info->nmsfree = 0;
      info->mxfree  = 0;
    }
  else if (value == mask)
    {
      /* All allocated */

      info->nfree   = 0;
      info->nlsfree = 0;
      info->nmsfree = 0;
      info->mxfree  = 0;
    }
  else
    {
      /* Some allocated */

      gran_nibble_info(value & 0x0f, info, nbits > 4 ? 4 : nbits);
      if (nbits > 4)
        {
          struct valinfo_s msinfo;
          unsigned int msbits = nbits - 4;

          gran_nibble_info(value >> 4, &msinfo, msbits);
          gran_info_combine(&msinfo, msbits, info, 4);
        }
    }
}

/****************************************************************************
 * Name: gran_hword_info
 *
 * Description:
 *   Return information a 16-bit value from the GAT.
 *
 * Input Parameters:
 *   value - The 16-bit value
 *   info  - The location to return the hword info
 *   nbits - Number of valid bits in value
 *
 * Returned Value:
 *   None
 *
 ****************************************************************************/

static void gran_hword_info(uint16_t value, FAR struct valinfo_s *info,
                            unsigned int nbits)
{
  uint16_t mask;

  if (nbits < 16)
    {
      mask   = ((1 << nbits) - 1);
      value &= mask;
    }
  else
    {
      mask = 0xffff;
    }

  /* Handle special cases */

  if (value == 0)
    {
      /* All free */

      info->nfree   = nbits;
      info->nlsfree = nbits;
      info->nmsfree = 0;
      info->mxfree  = 0;
    }
  else if (value == mask)
    {
      /* All allocated */

      info->nfree   = 0;
      info->nlsfree = 0;
      info->nmsfree = 0;
      info->mxfree  = 0;
    }
  else
    {
      /* Some allocated */

      gran_byte_info((uint8_t)(value & 0xff), info, nbits > 8 ? 8 : nbits);
      if (nbits > 8)
        {
          struct valinfo_s msinfo;
          unsigned int msbits = nbits - 8;

          gran_byte_info((uint8_t)(value >> 8), &msinfo, msbits);
          gran_info_combine(&msinfo, msbits, info, 8);
        }
    }
}

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

/****************************************************************************
 * Name: gran_info
 *
 * Description:
 *   Return information about the granule heap.
 *
 * Input Parameters:
 *   handle - The handle previously returned by gran_initialize
 *   info   - Memory location to return the gran allocator info.
 *
 * Returned Value:
 *   Zero (OK) is returned on success; a negated errno value is return on
 *   any failure.
 *
 ****************************************************************************/

void gran_info(GRAN_HANDLE handle, FAR struct graninfo_s *info)
{
  FAR struct gran_s *priv = (FAR struct gran_s *)handle;
  uint32_t mask;
  uint32_t value;
  uint16_t mxfree;
  unsigned int nbits;
  unsigned int granidx;
  unsigned int gatidx;
  int ret;

  DEBUGASSERT(priv != NULL && info != NULL);

  info->log2gran   = priv->log2gran;
  info->ngranules  = priv->ngranules;
  info->nfree      = 0;
  info->mxfree     = 0;
  mxfree           = 0;

  /* Get exclusive access to the GAT */

  ret = gran_enter_critical(priv);
  if (ret < 0)
    {
      /* Should happen only on task cancellation */

      DEBUGASSERT(ret == -ECANCELED);
      return;
    }

  /* Traverse the granule allocation  */

  for (granidx = 0; granidx < priv->ngranules; granidx += 32)
    {
      /* Get the GAT index associated with the granule table entry */

      gatidx = granidx >> 5;
      value  = priv->gat[gatidx];

      /* The final entry is a special case */

      if ((granidx + 32) > priv->ngranules)
        {
          nbits  = priv->ngranules - granidx;
          mask   = ((1ul << nbits) - 1);
          value  &= mask;
        }
      else
        {
          nbits  = 32;
          mask   = 0xffffffff;
        }

      /* Handle the 32-bit cases */

      if (value == mask)
        {
          /* All allocated.  This will terminate any sequence of free
           * granules.
           */

          if (mxfree > info->mxfree)
            {
              info->mxfree = mxfree;
            }

          mxfree = 0;
        }
      else if (value == 0x00000000)
        {
          /* All free */

          info->nfree += nbits;
          mxfree      += nbits;
        }
      else
        {
          struct valinfo_s hwinfo;

          /* Some allocated */

          gran_hword_info((uint16_t)(value & 0xffff), &hwinfo,
                          nbits > 16 ? 16 : nbits);
          if (nbits > 16)
            {
              struct valinfo_s msinfo;
              unsigned int msbits = nbits - 16;

              gran_hword_info((uint16_t)(value >> 16), &msinfo, msbits);
              gran_info_combine(&msinfo, msbits, &hwinfo, 16);
            }

          /* Update the running free sequence of granules */

          if (hwinfo.nlsfree > 0)
            {
              mxfree += hwinfo.nlsfree;
            }

          /* If the entire word is not free, then update the maxfree free
           * sequence.
           */

          if (hwinfo.nlsfree < nbits)
            {
              /* Is the sequence internally free bits in the 32-bit value
               * longer than the running free sequence?
               */

              if (hwinfo.mxfree > mxfree)
                {
                  mxfree = hwinfo.mxfree;
                }

              /* Is the running free sequence longer than the last sequence
               * that we saw?
               */

              if (mxfree > info->mxfree)
                {
                  info->mxfree = mxfree;
                }

              /* Then restart with the free MS granules */

              mxfree = hwinfo.nmsfree;
            }

          /* Update the total number of free granules */

          info->nfree += hwinfo.nfree;
        }
    }

  /* Check if the last, unterminated sequence of free granules was
   * the longest
   */

  if (mxfree > info->mxfree)
    {
      info->mxfree = mxfree;
    }

  gran_leave_critical(priv);
}

#endif /* CONFIG_GRAN */