cache.c

ATMEL单片机可用的文件系统源代码

/***********************************************************************/
/*                                                                     */
/*   Module:  cache.c                                                  */
/*   Release: 2004.5                                                   */
/*   Version: 2004.2                                                   */
/*   Purpose: Cache interface for the file systems                     */
/*                                                                     */
/*---------------------------------------------------------------------*/
/*                                                                     */
/*               Copyright 2004, Blunk Microsystems                    */
/*                      ALL RIGHTS RESERVED                            */
/*                                                                     */
/*   Licensees have the non-exclusive right to use, modify, or extract */
/*   this computer program for software development at a single site.  */
/*   This program may be resold or disseminated in executable format   */
/*   only. The source code may not be redistributed or resold.         */
/*                                                                     */
/***********************************************************************/
#include "posixfsp.h"
#include "../include/cache.h"

/***********************************************************************/
/* Local Function Definitions                                          */
/***********************************************************************/

/***********************************************************************/
/* remove_from_replacer: Remove specified entry from cache LRU list    */
/*                                                                     */
/*      Inputs: entry = pointer to cache entry                         */
/*              C = cache to which LRU list belongs                    */
/*                                                                     */
/***********************************************************************/
static void remove_from_replacer(CacheEntry *entry, Cache *C)
{
  /*-------------------------------------------------------------------*/
  /* Adjust the double linked list (LRU) by taking the entry out.      */
  /*-------------------------------------------------------------------*/
  if (entry->prev_lru)
    entry->prev_lru->next_lru = entry->next_lru;
  else
    C->lru_head = entry->next_lru;

  if (entry->next_lru)
    entry->next_lru->prev_lru = entry->prev_lru;
  else
    C->lru_tail = entry->prev_lru;

  /*-------------------------------------------------------------------*/
  /* Null out the pointers for the taken out entry.                    */
  /*-------------------------------------------------------------------*/
  entry->prev_lru = entry->next_lru = NULL;
}

/***********************************************************************/
/* put_into_tail: Add an entry to the end of the linked list           */
/*                                                                     */
/*      Inputs: entry = pointer to cache entry to be added             */
/*              C = cache to which the list belongs                    */
/*                                                                     */
/***********************************************************************/
static void put_into_tail(CacheEntry *entry, Cache *C)
{
  /*-------------------------------------------------------------------*/
  /* Set next to NULL since entry will be last entry, and prev to what */
  /* tail of list was before.                                          */
  /*-------------------------------------------------------------------*/
  entry->next_lru = NULL;
  entry->prev_lru = C->lru_tail;

  /*-------------------------------------------------------------------*/
  /* If the list was not empty, set the next of tail to new entry,     */
  /* else, because list was empty, set also head of list to new entry. */
  /*-------------------------------------------------------------------*/
  if (C->lru_tail)
    C->lru_tail->next_lru = entry;
  else
    C->lru_head = entry;

  /*-------------------------------------------------------------------*/
  /* Set tail of list to new entry.                                    */
  /*-------------------------------------------------------------------*/
  C->lru_tail = entry;
}

/***********************************************************************/
/*        hash: Hash based on the sector number                        */
/*                                                                     */
/*      Inputs: sector_number = value on which hash is done            */
/*              size = size of the table                               */
/*                                                                     */
/*     Returns: Index into the hash table where value gets hashed      */
/*                                                                     */
/***********************************************************************/
static int hash(int sector_number, int size)
{
  return (19823 * sector_number + 321043) % size;
}

/***********************************************************************/
/* Global Function Definitions                                         */
/***********************************************************************/

/***********************************************************************/
/*   InitCache: Initialize and allocate memory for the specified cache */
/*                                                                     */
/*      Inputs: C = cache to be initialized                            */
/*              pool_size = number of sectors in the cache             */
/*              writef = write sector function                         */
/*              readf = read sector function                           */
/*              sect_sz = sector size for file system                  */
/*              temp_sects = number of temporary sectors               */
/*              alignment = memory alignment                           */
/*                                                                     */
/*     Returns: Beginning of pool on success, 0 on failure             */
/*                                                                     */
/***********************************************************************/
ui32 InitCache(Cache *C, int pool_size, MedWFunc writef, MedRFunc readf,
               int sect_sz, int temp_sects, int alignment)
{
  ui32 *sectors;

  /*-------------------------------------------------------------------*/
  /* Set the write and read functions for the cache.                   */
  /*-------------------------------------------------------------------*/
  C->write = writef;
  C->read = readf;

  /*-------------------------------------------------------------------*/
  /* Set the number of sectors in cache.                               */
  /*-------------------------------------------------------------------*/
  C->pool_size = pool_size;

  /*-------------------------------------------------------------------*/
  /* Allocate memory for the pool and hash table.                      */
  /*-------------------------------------------------------------------*/
  C->pool = calloc((size_t)C->pool_size * sizeof(CacheEntry), (size_t)1);
  if (C->pool == NULL)
    return 0;
  C->hash_tbl = calloc((size_t)C->pool_size * sizeof(CacheEntry *),
                       (size_t)1);
  if (C->hash_tbl == NULL)
  {
    free(C->pool);
    return 0;
  }

  /*-------------------------------------------------------------------*/
  /* Allocate memory for all the sectors. This is where data goes.     */
  /* Also, allocate extra sectors for use by file sys. internals.      */
  /* Pointers to extra sectors will be set in file system init routine.*/
  /*-------------------------------------------------------------------*/
  sectors = calloc((size_t)(sect_sz * (C->pool_size + temp_sects) /
                            alignment), (size_t)alignment);
  if (sectors == NULL)
  {
    free(C->pool);
    free(C->hash_tbl);
    return 0;
  }

  /*-------------------------------------------------------------------*/
  /* Initialize the pool for the cache.                                */
  /*-------------------------------------------------------------------*/
  C->pool[0].sector = (ui8 *)sectors;
  ReinitCache(C, sect_sz);

  return (ui32)sectors;
}

/***********************************************************************/
/* ReinitCache: Re-initialize the cache                                */
/*                                                                     */
/*      Inputs: C = cache to be reinitialized                          */
/*              sect_sz = sector size for file system                  */
/*                                                                     */
/***********************************************************************/
void ReinitCache(Cache *C, int sect_sz)
{
  int i;
  ui8 *mem = C->pool[0].sector;

  /*-------------------------------------------------------------------*/
  /* Loop to initialize each entry in the cache.                       */
  /*-------------------------------------------------------------------*/
  for (i = 0; i < C->pool_size; ++i)
  {
    /*-----------------------------------------------------------------*/
    /* Assign a sector chunk of the preallocated memory.               */
    /*-----------------------------------------------------------------*/
    C->pool[i].sector = mem;
    mem += sect_sz;

    /*-----------------------------------------------------------------*/
    /* Set the entry in the pool to have an invalid sector number, -1, */
    /* not dirty, 0 pin count, no hash location and file_ptr.          */
    /*-----------------------------------------------------------------*/
    C->pool[i].sect_num = -1;
    C->pool[i].dirty = CLEAN;
    C->pool[i].pin_cnt = 0;
    C->pool[i].hash_loc = NULL;
    C->pool[i].file_ptr = NULL;

    /*-----------------------------------------------------------------*/
    /* If the first entry in pool, set its prev_lru to NULL.           */
    /*-----------------------------------------------------------------*/
    if (!i)
    {
      C->pool[i].prev_lru = NULL;
      if (C->pool_size == 1)
        C->pool[i].next_lru = NULL;
      else
        C->pool[i].next_lru = &C->pool[i + 1];
    }

    /*-----------------------------------------------------------------*/
    /* Else if last entry in pool, set its next_lru to NULL.           */
    /*-----------------------------------------------------------------*/
    else if (i == (C->pool_size - 1))
    {
      C->pool[i].prev_lru = &C->pool[i - 1];
      C->pool[i].next_lru = NULL;
    }

    /*-----------------------------------------------------------------*/
    /* Else set prev_lru to previous and next_lru to next entry.       */
    /*-----------------------------------------------------------------*/
    else
    {
      C->pool[i].prev_lru = &C->pool[i - 1];
      C->pool[i].next_lru = &C->pool[i + 1];
    }

    /*-----------------------------------------------------------------*/
    /* Initialize also the hash table entry.                           */
    /*-----------------------------------------------------------------*/
    C->pool[i].next_hash = C->pool[i].prev_hash = NULL;
    C->pool[i].hash_loc = NULL;
    C->hash_tbl[i] = NULL;
  }

  /*-------------------------------------------------------------------*/
  /* Set the dirty flags.                                              */
  /*-------------------------------------------------------------------*/
  C->dirty_old = C->dirty_new = FALSE;

  /*-------------------------------------------------------------------*/
  /* Initialize the current sector being worked on.                    */
  /*-------------------------------------------------------------------*/
  C->sector_number = -1;