modules/access/mmap.c

   1 /*****************************************************************************
   2  * mmap.c: memory-mapped file input
   3  *****************************************************************************
   4  * Copyright © 2007-2008 Rémi Denis-Courmont
   5  * $Id$
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License as published by
   9  * the Free Software Foundation; either version 2 of the License, or
  10  * (at your option) any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program; if not, write to the Free Software
  19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
  20  *****************************************************************************/
  21
  22 #ifdef HAVE_CONFIG_H
  23 # include <config.h>
  24 #endif
  25
  26 #include <vlc_common.h>
  27 #include <vlc_plugin.h>
  28 #include <vlc_access.h>
  29 #include <vlc_input.h>
  30 #include <vlc_fs.h>
  31 #include <vlc_dialog.h>
  32
  33 #include <assert.h>
  34
  35 #include <sys/types.h>
  36 #include <unistd.h>
  37 #include <fcntl.h>
  38 #include <sys/stat.h>
  39 #include <sys/mman.h>
  40
  41 #define FILE_MMAP_TEXT N_("Use file memory mapping")
  42 #define FILE_MMAP_LONGTEXT N_( \
  43     "Try to use memory mapping to read files and block devices." )
  44
  45 #ifndef NDEBUG
  46 /*# define MMAP_DEBUG 1*/
  47 #endif
  48
  49 static int Open (vlc_object_t *);
  50 static void Close (vlc_object_t *);
  51
  52 vlc_module_begin ()
  53     set_shortname (N_("MMap"))
  54     set_description (N_("Memory-mapped file input"))
  55     set_category (CAT_INPUT)
  56     set_subcategory (SUBCAT_INPUT_ACCESS)
  57     set_capability ("access", 52)
  58     add_shortcut ("file")
  59     set_callbacks (Open, Close)
  60 #ifdef __APPLE__
  61     add_bool ("file-mmap", true, NULL,
  62               FILE_MMAP_TEXT, FILE_MMAP_LONGTEXT, true)
  63 #else
  64     add_bool ("file-mmap", false, NULL,
  65               FILE_MMAP_TEXT, FILE_MMAP_LONGTEXT, true)
  66 #endif
  67 vlc_module_end ()
  68
  69 static block_t *Block (access_t *);
  70 static int Seek (access_t *, uint64_t);
  71 static int Control (access_t *, int, va_list);
  72
  73 struct access_sys_t
  74 {
  75     size_t page_size;
  76     size_t mtu;
  77     int    fd;
  78 };
  79
  80 #define MMAP_SIZE (1 << 20)
  81
  82 static int Open (vlc_object_t *p_this)
  83 {
  84     access_t *p_access = (access_t *)p_this;
  85     access_sys_t *p_sys;
  86     const char *path = p_access->psz_filepath;
  87     int fd;
  88
  89     assert ((INT64_C(1) << 63) == ((off_t)(INT64_C(1) << 63)));
  90
  91     if (!var_InheritBool (p_this, "file-mmap"))
  92         return VLC_EGENERIC; /* disabled */
  93
  94     STANDARD_BLOCK_ACCESS_INIT;
  95
  96     msg_Dbg (p_access, "opening file %s", path);
  97     fd = vlc_open (path, O_RDONLY | O_NOCTTY);
  98
  99     if (fd == -1)
 100     {
 101         msg_Warn (p_access, "cannot open %s: %m", path);
 102         goto error;
 103     }
 104
 105     /* mmap() is only safe for regular and block special files.
 106      * For other types, it may be some idiosyncrasic interface (e.g. packet
 107      * sockets are a good example), if it works at all. */
 108     struct stat st;
 109
 110     if (fstat (fd, &st))
 111     {
 112         msg_Err (p_access, "cannot stat %s: %m", path);
 113         goto error;
 114     }
 115
 116     if (!S_ISREG (st.st_mode) && !S_ISBLK (st.st_mode))
 117     {
 118         msg_Dbg (p_access, "skipping non-regular file %s", path);
 119         goto error;
 120     }
 121
 122 #if defined(HAVE_FCNTL_H)
 123     /* We'd rather use any available memory for reading ahead
 124      * than for caching what we've already mmap'ed */
 125 # if defined(F_RDAHEAD)
 126     fcntl (fd, F_RDAHEAD, 1);
 127 # endif
 128 # if defined(F_NOCACHE)
 129     fcntl (fd, F_NOCACHE, 1);
 130 # endif
 131 #endif
 132
 133     /* Autodetect mmap() support */
 134     if (st.st_size > 0)
 135     {
 136         void *addr = mmap (NULL, 1, PROT_READ|PROT_WRITE, MAP_PRIVATE, fd, 0);
 137         if (addr != MAP_FAILED)
 138             munmap (addr, 1);
 139         else
 140             goto error;
 141     }
 142
 143     p_sys->page_size = sysconf (_SC_PAGE_SIZE);
 144     p_sys->mtu = MMAP_SIZE;
 145     if (p_sys->mtu < p_sys->page_size)
 146         p_sys->mtu = p_sys->page_size;
 147     p_sys->fd = fd;
 148
 149     p_access->info.i_size = st.st_size;
 150 #ifdef HAVE_POSIX_FADVISE
 151     posix_fadvise (fd, 0, 0, POSIX_FADV_SEQUENTIAL);
 152 #endif
 153
 154     return VLC_SUCCESS;
 155
 156 error:
 157     if (fd != -1)
 158         close (fd);
 159     free (p_sys);
 160     return VLC_EGENERIC;
 161 }
 162
 163
 164 static void Close (vlc_object_t * p_this)
 165 {
 166     access_t *p_access = (access_t *)p_this;
 167     access_sys_t *p_sys = p_access->p_sys;
 168
 169     close (p_sys->fd); /* don't care about error when only reading */
 170     free (p_sys);
 171 }
 172
 173 static block_t *Block (access_t *p_access)
 174 {
 175     access_sys_t *p_sys = p_access->p_sys;
 176
 177     /* Check if file size changed... */
 178     struct stat st;
 179
 180     if ((fstat (p_sys->fd, &st) == 0)
 181      && (st.st_size != p_access->info.i_size))
 182     {
 183         p_access->info.i_size = st.st_size;
 184         p_access->info.i_update |= INPUT_UPDATE_SIZE;
 185     }
 186
 187     if (p_access->info.i_pos >= p_access->info.i_size)
 188     {
 189         /* We are at end of file */
 190         p_access->info.b_eof = true;
 191         msg_Dbg (p_access, "at end of memory mapped file");
 192         return NULL;
 193     }
 194
 195 #ifdef MMAP_DEBUG
 196     uint64_t dbgpos = lseek (p_sys->fd, 0, SEEK_CUR);
 197     if (dbgpos != p_access->info.i_pos)
 198         msg_Err (p_access, "position: 0x%016"PRIx64" instead of 0x%016"PRIx64,
 199                  p_access->info.i_pos, dbgpos);
 200 #endif
 201
 202     const uintptr_t page_mask = p_sys->page_size - 1;
 203     /* Start the mapping on a page boundary: */
 204     off_t  outer_offset = p_access->info.i_pos & ~(off_t)page_mask;
 205     /* Skip useless bytes at the beginning of the first page: */
 206     size_t inner_offset = p_access->info.i_pos & page_mask;
 207     /* Map no more bytes than remain: */
 208     size_t length = p_sys->mtu;
 209     if (outer_offset + length > p_access->info.i_size)
 210         length = p_access->info.i_size - outer_offset;
 211
 212     assert (outer_offset <= p_access->info.i_pos);          /* and */
 213     assert (p_access->info.i_pos < p_access->info.i_size); /* imply */
 214     assert (outer_offset < p_access->info.i_size);         /* imply */
 215     assert (length > 0);
 216
 217     /* NOTE: We use PROT_WRITE and MAP_PRIVATE so that the block can be
 218      * modified down the chain, without messing up with the underlying
 219      * original file. This does NOT need open write permission. */
 220     void *addr = mmap (NULL, length, PROT_READ|PROT_WRITE, MAP_PRIVATE
 221 #ifdef MAP_NO_CACHE
 222                        | MAP_NOCACHE
 223 #endif
 224                        , p_sys->fd, outer_offset);
 225     if (addr == MAP_FAILED)
 226     {
 227         msg_Err (p_access, "memory mapping failed (%m)");
 228         dialog_Fatal (p_access, _("File reading failed"), "%s",
 229                         _("VLC could not read the file."));
 230         goto fatal;
 231     }
 232 #ifdef HAVE_POSIX_MADVISE
 233     posix_madvise (addr, length, POSIX_MADV_SEQUENTIAL);
 234 #endif
 235
 236     block_t *block = block_mmap_Alloc (addr, length);
 237     if (block == NULL)
 238         goto fatal;
 239
 240     block->p_buffer += inner_offset;
 241     block->i_buffer -= inner_offset;
 242
 243 #ifdef MMAP_DEBUG
 244     msg_Dbg (p_access, "mapped 0x%zx bytes at %p from offset 0x%"PRIx64,
 245              length, addr, (uint64_t)outer_offset);
 246
 247     /* Compare normal I/O with memory mapping */
 248     char *buf = malloc (block->i_buffer);
 249     ssize_t i_read = read (p_sys->fd, buf, block->i_buffer);
 250
 251     if (i_read != (ssize_t)block->i_buffer)
 252         msg_Err (p_access, "read %zd instead of %zu bytes", i_read,
 253                  block->i_buffer);
 254     if (memcmp (buf, block->p_buffer, block->i_buffer))
 255         msg_Err (p_access, "inconsistent data buffer");
 256     free (buf);
 257 #endif
 258
 259     p_access->info.i_pos = outer_offset + length;
 260     return block;
 261
 262 fatal:
 263     p_access->info.b_eof = true;
 264     return NULL;
 265 }
 266
 267
 268 static int Seek (access_t *p_access, uint64_t i_pos)
 269 {
 270 #ifdef MMAP_DEBUG
 271     lseek (p_access->p_sys->fd, i_pos, SEEK_SET);
 272 #endif
 273
 274     p_access->info.i_pos = i_pos;
 275     p_access->info.b_eof = false;
 276     return VLC_SUCCESS;
 277 }
 278
 279
 280 static int Control (access_t *p_access, int query, va_list args)
 281 {
 282     switch (query)
 283     {
 284         case ACCESS_CAN_SEEK:
 285         case ACCESS_CAN_FASTSEEK:
 286         case ACCESS_CAN_PAUSE:
 287         case ACCESS_CAN_CONTROL_PACE:
 288             *va_arg(args, bool *) = true;
 289             return VLC_SUCCESS;
 290
 291         case ACCESS_GET_PTS_DELAY:
 292         {
 293             int64_t delay_ms = var_CreateGetInteger (p_access, "file-caching");
 294             *va_arg(args, int64_t *) = delay_ms * INT64_C (1000);
 295             return VLC_SUCCESS;
 296         }
 297
 298         case ACCESS_GET_TITLE_INFO:
 299         case ACCESS_GET_META:
 300             break;
 301
 302         case ACCESS_SET_PAUSE_STATE:
 303             return VLC_SUCCESS;
 304
 305         case ACCESS_SET_TITLE:
 306         case ACCESS_SET_SEEKPOINT:
 307         case ACCESS_SET_PRIVATE_ID_STATE:
 308         case ACCESS_SET_PRIVATE_ID_CA:
 309         case ACCESS_GET_PRIVATE_ID_STATE:
 310         case ACCESS_GET_CONTENT_TYPE:
 311             break;
 312
 313         default:
 314             msg_Warn (p_access, "unimplemented query %d in control", query);
 315     }
 316
 317     return VLC_EGENERIC;
 318 }