read_cache.c

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/*
 * Copyright (C) 2000 Rich Wareham <richwareham@users.sourceforge.net>
 *               2001-2004 the dvdnav project
 *
 * This file is part of libdvdnav, a DVD navigation library.
 *
 * libdvdnav 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; either version 2 of the License, or
 * (at your option) any later version.
 *
 * libdvdnav 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 this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA
 *
 * $Id: read_cache.c,v 1.12 2004/03/16 11:43:38 mroi Exp $
 *
 */
/*
 * There was a multithreaded read ahead cache in here for some time, but
 * it had only been used for a short time. If you want to have a look at it,
 * search the CVS attic.
 */

#include "config.h"

#include "dvdnav_internal.h"
#include "dvdnav.h"
#include "read_cache.h"

#include <time.h>
#ifndef _WIN32
#include <sys/time.h>
#endif

#define READ_CACHE_CHUNKS 10

/* all cache chunks must be memory aligned to allow use of raw devices */
#define ALIGNMENT 2048

#define READ_AHEAD_SIZE_MIN 4
#define READ_AHEAD_SIZE_MAX 512

typedef struct read_cache_chunk_s {
  uint8_t     *cache_buffer;
  uint8_t     *cache_buffer_base;  /* used in malloc and free for alignment */
  int32_t      cache_start_sector; /* -1 means cache invalid */
  int32_t      cache_read_count;   /* this many sectors are already read */
  size_t       cache_block_count;  /* this many sectors will go in this chunk */
  size_t       cache_malloc_size;
  int          cache_valid;
  int          usage_count;  /* counts how many buffers where issued from this chunk */
} read_cache_chunk_t;

struct read_cache_s {
  read_cache_chunk_t  chunk[READ_CACHE_CHUNKS];
  int                 current;
  int                 freeing;  /* is set to one when we are about to dispose the cache */
  uint32_t            read_ahead_size;
  int                 read_ahead_incr;
  int                 last_sector;
  pthread_mutex_t     lock;

  /* Bit of strange cross-linking going on here :) -- Gotta love C :) */
  dvdnav_t           *dvd_self;
};

/*
#define READ_CACHE_TRACE 0
*/

#ifdef __GNUC__
# if READ_CACHE_TRACE
#  define dprintf(fmt, args...) fprintf(MSG_OUT, "libdvdnav: %s: "fmt,  __func__ , ## args)
# else
#  define dprintf(fmt, args...) /* Nowt */
# endif
#else
# if READ_CACHE_TRACE
#  define dprintf(fmt, ...) fprintf(MSG_OUT, "libdvdnav: %s: "fmt,  __func__ , __VA_ARGS__)
# else
#ifdef _MSC_VER
#  define dprintf(fmt, str) /* Nowt */
#else
#  define dprintf(fmt, ...) /* Nowt */
#endif /* _MSC_VER */
# endif
#endif


read_cache_t *dvdnav_read_cache_new(dvdnav_t* dvd_self) {
  read_cache_t *self;
  int i;

  self = (read_cache_t *)malloc(sizeof(read_cache_t));

  if(self) {
    self->current = 0;
    self->freeing = 0;
    self->dvd_self = dvd_self;
    self->last_sector = 0;
    self->read_ahead_size = READ_AHEAD_SIZE_MIN;
    self->read_ahead_incr = 0;
    pthread_mutex_init(&self->lock, NULL);
    dvdnav_read_cache_clear(self);
    for (i = 0; i < READ_CACHE_CHUNKS; i++) {
      self->chunk[i].cache_buffer = NULL;
      self->chunk[i].usage_count = 0;
    }
  }

  return self;
}

void dvdnav_read_cache_free(read_cache_t* self) {
  dvdnav_t *tmp;
  int i;

  pthread_mutex_lock(&self->lock);
  self->freeing = 1;
  for (i = 0; i < READ_CACHE_CHUNKS; i++)
    if (self->chunk[i].cache_buffer && self->chunk[i].usage_count == 0) {
      free(self->chunk[i].cache_buffer_base);
      self->chunk[i].cache_buffer = NULL;
    }
  pthread_mutex_unlock(&self->lock);

  for (i = 0; i < READ_CACHE_CHUNKS; i++)
    if (self->chunk[i].cache_buffer) return;

  /* all buffers returned, free everything */
  tmp = self->dvd_self;
  pthread_mutex_destroy(&self->lock);
  free(self);
  free(tmp);
}

/* This function MUST be called whenever self->file changes. */
void dvdnav_read_cache_clear(read_cache_t *self) {
  int i;

  if(!self)
   return;

  pthread_mutex_lock(&self->lock);
  for (i = 0; i < READ_CACHE_CHUNKS; i++)
    self->chunk[i].cache_valid = 0;
  pthread_mutex_unlock(&self->lock);
}

/* This function is called just after reading the NAV packet. */
void dvdnav_pre_cache_blocks(read_cache_t *self, int sector, size_t block_count) {
  int i, use;

  if(!self)
    return;

  if(!self->dvd_self->use_read_ahead)
    return;

  pthread_mutex_lock(&self->lock);

  /* find a free cache chunk that best fits the required size */
  use = -1;
  for (i = 0; i < READ_CACHE_CHUNKS; i++)
    if (self->chunk[i].usage_count == 0 && self->chunk[i].cache_buffer &&
        self->chunk[i].cache_malloc_size >= block_count &&
        (use == -1 || self->chunk[use].cache_malloc_size > self->chunk[i].cache_malloc_size))
      use = i;

  if (use == -1) {
    /* we haven't found a cache chunk, so we try to reallocate an existing one */
    for (i = 0; i < READ_CACHE_CHUNKS; i++)
      if (self->chunk[i].usage_count == 0 && self->chunk[i].cache_buffer &&
          (use == -1 || self->chunk[use].cache_malloc_size < self->chunk[i].cache_malloc_size))
        use = i;
    if (use >= 0) {
      self->chunk[use].cache_buffer_base = realloc(self->chunk[use].cache_buffer_base,
        block_count * DVD_VIDEO_LB_LEN + ALIGNMENT);
      self->chunk[use].cache_buffer =
        (uint8_t *)(((uintptr_t)self->chunk[use].cache_buffer_base & ~((uintptr_t)(ALIGNMENT - 1))) + ALIGNMENT);
      dprintf("pre_cache DVD read realloc happened\n");
      self->chunk[use].cache_malloc_size = block_count;
    } else {
      /* we still haven't found a cache chunk, let's allocate a new one */
      for (i = 0; i < READ_CACHE_CHUNKS; i++)
        if (!self->chunk[i].cache_buffer) {
          use = i;
          break;
        }
      if (use >= 0) {
        /* We start with a sensible figure for the first malloc of 500 blocks.
         * Some DVDs I have seen venture to 450 blocks.
         * This is so that fewer realloc's happen if at all.
         */
        self->chunk[i].cache_buffer_base =
          malloc((block_count > 500 ? block_count : 500) * DVD_VIDEO_LB_LEN + ALIGNMENT);
        self->chunk[i].cache_buffer =
          (uint8_t *)(((uintptr_t)self->chunk[i].cache_buffer_base & ~((uintptr_t)(ALIGNMENT - 1))) + ALIGNMENT);
        self->chunk[i].cache_malloc_size = block_count > 500 ? block_count : 500;
        dprintf("pre_cache DVD read malloc %d blocks\n",
          (block_count > 500 ? block_count : 500 ));
      }
    }
  }

  if (use >= 0) {
    self->chunk[use].cache_start_sector = sector;
    self->chunk[use].cache_block_count = block_count;
    self->chunk[use].cache_read_count = 0;
    self->chunk[use].cache_valid = 1;
    self->current = use;
  } else {
    dprintf("pre_caching was impossible, no cache chunk available\n");
  }
  pthread_mutex_unlock(&self->lock);
}

int dvdnav_read_cache_block(read_cache_t *self, int sector, size_t block_count, uint8_t **buf) {
  int i, use;
  int start;
  int size;
  int incr;
  uint8_t *read_ahead_buf;
  int32_t res;

  if(!self)
    return 0;

  use = -1;

  if(self->dvd_self->use_read_ahead) {
    /* first check, if sector is in current chunk */
    read_cache_chunk_t cur = self->chunk[self->current];
    if (cur.cache_valid && sector >= cur.cache_start_sector &&
        sector <= (cur.cache_start_sector + cur.cache_read_count) &&
        sector + block_count <= cur.cache_start_sector + cur.cache_block_count)
      use = self->current;
    else
      for (i = 0; i < READ_CACHE_CHUNKS; i++)
        if (self->chunk[i].cache_valid &&
            sector >= self->chunk[i].cache_start_sector &&
            sector <= (self->chunk[i].cache_start_sector + self->chunk[i].cache_read_count) &&
            sector + block_count <= self->chunk[i].cache_start_sector + self->chunk[i].cache_block_count)
            use = i;
  }

  if (use >= 0) {
    read_cache_chunk_t *chunk;
    
    /* Increment read-ahead size if sector follows the last sector */
    if (sector == (self->last_sector + 1)) {
      if (self->read_ahead_incr < READ_AHEAD_SIZE_MAX)
        self->read_ahead_incr++;
    } else {
      self->read_ahead_size = READ_AHEAD_SIZE_MIN;
      self->read_ahead_incr = 0;
    }
    self->last_sector = sector;

    /* The following resources need to be protected by a mutex :
     *   self->chunk[*].cache_buffer
     *   self->chunk[*].cache_malloc_size
     *   self->chunk[*].usage_count
     */
    pthread_mutex_lock(&self->lock);
    chunk = &self->chunk[use];
    read_ahead_buf = chunk->cache_buffer + chunk->cache_read_count * DVD_VIDEO_LB_LEN;
    *buf = chunk->cache_buffer + (sector - chunk->cache_start_sector) * DVD_VIDEO_LB_LEN;
    chunk->usage_count++;
    pthread_mutex_unlock(&self->lock);

    dprintf("libdvdnav: sector=%d, start_sector=%d, last_sector=%d\n", sector, chunk->cache_start_sector, chunk->cache_start_sector + chunk->cache_block_count);

    /* read_ahead_size */
    incr = self->read_ahead_incr >> 1;
    if ((self->read_ahead_size + incr) > READ_AHEAD_SIZE_MAX) {
      self->read_ahead_size = READ_AHEAD_SIZE_MAX;
    } else {
      self->read_ahead_size += incr;
    }

    /* real read size */
    start = chunk->cache_start_sector + chunk->cache_read_count;
    if (chunk->cache_read_count + self->read_ahead_size > chunk->cache_block_count) {
      size = chunk->cache_block_count - chunk->cache_read_count;
    } else {
      size = self->read_ahead_size;
      /* ensure that the sector we want will be read */
      if (sector >= chunk->cache_start_sector + chunk->cache_read_count + size)
        size = sector - chunk->cache_start_sector - chunk->cache_read_count;
    }
    dprintf("libdvdnav: read_ahead_size=%d, size=%d\n", self->read_ahead_size, size);

    if (size)
      chunk->cache_read_count += DVDReadBlocks(self->dvd_self->file,
                                               start,
                                               size,
                                               read_ahead_buf);

    res = DVD_VIDEO_LB_LEN * block_count;

  } else {

    if (self->dvd_self->use_read_ahead)
      dprintf("cache miss on sector %d\n", sector);

    res = DVDReadBlocks(self->dvd_self->file,
                        sector,
                        block_count,
                        *buf) * DVD_VIDEO_LB_LEN;
  }

  return res;

}

dvdnav_status_t dvdnav_free_cache_block(dvdnav_t *self, unsigned char *buf) {
  read_cache_t *cache;
  int i;

  if (!self)
    return DVDNAV_STATUS_ERR;

  cache = self->cache;
  if (!cache)
    return DVDNAV_STATUS_ERR;

  pthread_mutex_lock(&cache->lock);
  for (i = 0; i < READ_CACHE_CHUNKS; i++) {
    if (cache->chunk[i].cache_buffer && buf >= cache->chunk[i].cache_buffer &&
        buf < cache->chunk[i].cache_buffer + cache->chunk[i].cache_malloc_size * DVD_VIDEO_LB_LEN) {
      cache->chunk[i].usage_count--;
    }
  }
  pthread_mutex_unlock(&cache->lock);

  if (cache->freeing)
    /* when we want to dispose the cache, try freeing it now */
    dvdnav_read_cache_free(cache);

  return DVDNAV_STATUS_OK;
}

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