src/misc/block.c

   1 /*****************************************************************************
   2  * block.c: Data blocks management functions
   3  *****************************************************************************
   4  * Copyright (C) 2003-2004 VLC authors and VideoLAN
   5  * Copyright (C) 2007-2009 Rémi Denis-Courmont
   6  *
   7  * Authors: Laurent Aimar <fenrir@videolan.org>
   8  *
   9  * This program is free software; you can redistribute it and/or modify it
  10  * under the terms of the GNU Lesser General Public License as published by
  11  * the Free Software Foundation; either version 2.1 of the License, or
  12  * (at your option) any later version.
  13  *
  14  * This program is distributed in the hope that it will be useful,
  15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  17  * GNU Lesser General Public License for more details.
  18  *
  19  * You should have received a copy of the GNU Lesser General Public License
  20  * along with this program; if not, write to the Free Software Foundation,
  21  * Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
  22  *****************************************************************************/
  23
  24 #ifdef HAVE_CONFIG_H
  25 # include "config.h"
  26 #endif
  27
  28 #include <sys/stat.h>
  29 #include <assert.h>
  30 #include <errno.h>
  31 #include <unistd.h>
  32 #include <fcntl.h>
  33
  34 #include <vlc_common.h>
  35 #include <vlc_block.h>
  36 #include <vlc_fs.h>
  37
  38 #ifndef NDEBUG
  39 static void BlockNoRelease( block_t *b )
  40 {
  41     fprintf( stderr, "block %p has no release callback! This is a bug!\n",
  42              (void *) b );
  43     abort();
  44 }
  45
  46 static void block_Check (block_t *block)
  47 {
  48     while (block != NULL)
  49     {
  50         unsigned char *start = block->p_start;
  51         unsigned char *end = block->p_start + block->i_size;
  52         unsigned char *bufstart = block->p_buffer;
  53         unsigned char *bufend = block->p_buffer + block->i_buffer;
  54
  55         assert (block->pf_release != BlockNoRelease);
  56         assert (start <= end);
  57         assert (bufstart <= bufend);
  58         assert (bufstart >= start);
  59         assert (bufend <= end);
  60
  61         block = block->p_next;
  62     }
  63 }
  64
  65 static void block_Invalidate (block_t *block)
  66 {
  67     block->p_next = NULL;
  68     block_Check (block);
  69     block->pf_release = BlockNoRelease;
  70 }
  71 #else
  72 # define block_Check(b) ((void)(b))
  73 # define block_Invalidate(b) ((void)(b))
  74 #endif
  75
  76 void block_Init( block_t *restrict b, void *buf, size_t size )
  77 {
  78     /* Fill all fields to their default */
  79     b->p_next = NULL;
  80     b->p_buffer = buf;
  81     b->i_buffer = size;
  82     b->p_start = buf;
  83     b->i_size = size;
  84     b->i_flags = 0;
  85     b->i_nb_samples = 0;
  86     b->i_pts =
  87     b->i_dts = VLC_TS_INVALID;
  88     b->i_length = 0;
  89 #ifndef NDEBUG
  90     b->pf_release = BlockNoRelease;
  91 #endif
  92 }
  93
  94 static void block_generic_Release (block_t *block)
  95 {
  96     /* That is always true for blocks allocated with block_Alloc(). */
  97     assert (block->p_start == (unsigned char *)(block + 1));
  98     block_Invalidate (block);
  99     free (block);
 100 }
 101
 102 static void BlockMetaCopy( block_t *restrict out, const block_t *in )
 103 {
 104     out->p_next    = in->p_next;
 105     out->i_nb_samples = in->i_nb_samples;
 106     out->i_dts     = in->i_dts;
 107     out->i_pts     = in->i_pts;
 108     out->i_flags   = in->i_flags;
 109     out->i_length  = in->i_length;
 110 }
 111
 112 /** Initial memory alignment of data block.
 113  * @note This must be a multiple of sizeof(void*) and a power of two.
 114  * libavcodec AVX optimizations require at least 32-bytes. */
 115 #define BLOCK_ALIGN        32
 116
 117 /** Initial reserved header and footer size. */
 118 #define BLOCK_PADDING      32
 119
 120 block_t *block_Alloc (size_t size)
 121 {
 122     /* 2 * BLOCK_PADDING: pre + post padding */
 123     const size_t alloc = sizeof (block_t) + BLOCK_ALIGN + (2 * BLOCK_PADDING)
 124                        + size;
 125     if (unlikely(alloc <= size))
 126         return NULL;
 127
 128     block_t *b = malloc (alloc);
 129     if (unlikely(b == NULL))
 130         return NULL;
 131
 132     block_Init (b, b + 1, alloc - sizeof (*b));
 133     static_assert ((BLOCK_PADDING % BLOCK_ALIGN) == 0,
 134                    "BLOCK_PADDING must be a multiple of BLOCK_ALIGN");
 135     b->p_buffer += BLOCK_PADDING + BLOCK_ALIGN - 1;
 136     b->p_buffer = (void *)(((uintptr_t)b->p_buffer) & ~(BLOCK_ALIGN - 1));
 137     b->i_buffer = size;
 138     b->pf_release = block_generic_Release;
 139     return b;
 140 }
 141
 142 block_t *block_TryRealloc (block_t *p_block, ssize_t i_prebody, size_t i_body)
 143 {
 144     block_Check( p_block );
 145
 146     /* Corner case: empty block requested */
 147     if( i_prebody <= 0 && i_body <= (size_t)(-i_prebody) )
 148         i_prebody = i_body = 0;
 149
 150     assert( p_block->p_start <= p_block->p_buffer );
 151     assert( p_block->p_start + p_block->i_size
 152                                     >= p_block->p_buffer + p_block->i_buffer );
 153
 154     /* First, shrink payload */
 155
 156     /* Pull payload start */
 157     if( i_prebody < 0 )
 158     {
 159         if( p_block->i_buffer >= (size_t)-i_prebody )
 160         {
 161             p_block->p_buffer -= i_prebody;
 162             p_block->i_buffer += i_prebody;
 163         }
 164         else /* Discard current payload entirely */
 165             p_block->i_buffer = 0;
 166         i_body += i_prebody;
 167         i_prebody = 0;
 168     }
 169
 170     /* Trim payload end */
 171     if( p_block->i_buffer > i_body )
 172         p_block->i_buffer = i_body;
 173
 174     size_t requested = i_prebody + i_body;
 175
 176     if( p_block->i_buffer == 0 )
 177     {   /* Corner case: nothing to preserve */
 178         if( requested <= p_block->i_size )
 179         {   /* Enough room: recycle buffer */
 180             size_t extra = p_block->i_size - requested;
 181
 182             p_block->p_buffer = p_block->p_start + (extra / 2);
 183             p_block->i_buffer = requested;
 184             return p_block;
 185         }
 186
 187         /* Not enough room: allocate a new buffer */
 188         block_t *p_rea = block_Alloc( requested );
 189         if( p_rea == NULL )
 190             return NULL;
 191
 192         BlockMetaCopy( p_rea, p_block );
 193         block_Release( p_block );
 194         return p_rea;
 195     }
 196
 197     uint8_t *p_start = p_block->p_start;
 198     uint8_t *p_end = p_start + p_block->i_size;
 199
 200     /* Second, reallocate the buffer if we lack space. */
 201     assert( i_prebody >= 0 );
 202     if( (size_t)(p_block->p_buffer - p_start) < (size_t)i_prebody
 203      || (size_t)(p_end - p_block->p_buffer) < i_body )
 204     {
 205         block_t *p_rea = block_Alloc( requested );
 206         if( p_rea == NULL )
 207             return NULL;
 208
 209         memcpy( p_rea->p_buffer + i_prebody, p_block->p_buffer,
 210                 p_block->i_buffer );
 211         BlockMetaCopy( p_rea, p_block );
 212         block_Release( p_block );
 213         return p_rea;
 214     }
 215
 216     /* Third, expand payload */
 217
 218     /* Push payload start */
 219     if( i_prebody > 0 )
 220     {
 221         p_block->p_buffer -= i_prebody;
 222         p_block->i_buffer += i_prebody;
 223         i_body += i_prebody;
 224         i_prebody = 0;
 225     }
 226
 227     /* Expand payload to requested size */
 228     p_block->i_buffer = i_body;
 229
 230     return p_block;
 231 }
 232
 233 block_t *block_Realloc (block_t *block, ssize_t prebody, size_t body)
 234 {
 235     block_t *rea = block_TryRealloc (block, prebody, body);
 236     if (rea == NULL)
 237         block_Release(block);
 238     return rea;
 239 }
 240
 241 static void block_heap_Release (block_t *block)
 242 {
 243     block_Invalidate (block);
 244     free (block->p_start);
 245     free (block);
 246 }
 247
 248 block_t *block_heap_Alloc (void *addr, size_t length)
 249 {
 250     block_t *block = malloc (sizeof (*block));
 251     if (block == NULL)
 252     {
 253         free (addr);
 254         return NULL;
 255     }
 256
 257     block_Init (block, addr, length);
 258     block->pf_release = block_heap_Release;
 259     return block;
 260 }
 261
 262 #ifdef HAVE_MMAP
 263 # include <sys/mman.h>
 264
 265 static void block_mmap_Release (block_t *block)
 266 {
 267     block_Invalidate (block);
 268     munmap (block->p_start, block->i_size);
 269     free (block);
 270 }
 271
 272 block_t *block_mmap_Alloc (void *addr, size_t length)
 273 {
 274     if (addr == MAP_FAILED)
 275         return NULL;
 276
 277     long page_mask = sysconf(_SC_PAGESIZE) - 1;
 278     size_t left = ((uintptr_t)addr) & page_mask;
 279     size_t right = (-length) & page_mask;
 280
 281     block_t *block = malloc (sizeof (*block));
 282     if (block == NULL)
 283     {
 284         munmap (addr, length);
 285         return NULL;
 286     }
 287
 288     block_Init (block, ((char *)addr) - left, left + length + right);
 289     block->p_buffer = addr;
 290     block->i_buffer = length;
 291     block->pf_release = block_mmap_Release;
 292     return block;
 293 }
 294 #else
 295 block_t *block_mmap_Alloc (void *addr, size_t length)
 296 {
 297     (void)addr; (void)length; return NULL;
 298 }
 299 #endif
 300
 301 #ifdef HAVE_SYS_SHM_H
 302 # include <sys/shm.h>
 303
 304 typedef struct block_shm_t
 305 {
 306     block_t     self;
 307     void       *base_addr;
 308 } block_shm_t;
 309
 310 static void block_shm_Release (block_t *block)
 311 {
 312     block_shm_t *p_sys = (block_shm_t *)block;
 313
 314     shmdt (p_sys->base_addr);
 315     free (p_sys);
 316 }
 317
 318 block_t *block_shm_Alloc (void *addr, size_t length)
 319 {
 320     block_shm_t *block = malloc (sizeof (*block));
 321     if (unlikely(block == NULL))
 322     {
 323         shmdt (addr);
 324         return NULL;
 325     }
 326
 327     block_Init (&block->self, (uint8_t *)addr, length);
 328     block->self.pf_release = block_shm_Release;
 329     block->base_addr = addr;
 330     return &block->self;
 331 }
 332 #else
 333 block_t *block_shm_Alloc (void *addr, size_t length)
 334 {
 335     (void) addr; (void) length;
 336     abort ();
 337 }
 338 #endif
 339
 340
 341 #ifdef _WIN32
 342 # include <io.h>
 343
 344 static
 345 ssize_t pread (int fd, void *buf, size_t count, off_t offset)
 346 {
 347     HANDLE handle = (HANDLE)(intptr_t)_get_osfhandle (fd);
 348     if (handle == INVALID_HANDLE_VALUE)
 349         return -1;
 350
 351     OVERLAPPED olap = {.Offset = offset, .OffsetHigh = (offset >> 32)};
 352     DWORD written;
 353     /* This braindead API will override the file pointer even if we specify
 354      * an explicit read offset... So do not expect this to mix well with
 355      * regular read() calls. */
 356     if (ReadFile (handle, buf, count, &written, &olap))
 357         return written;
 358     return -1;
 359 }
 360 #endif
 361
 362 block_t *block_File(int fd, bool write)
 363 {
 364     size_t length;
 365     struct stat st;
 366
 367     /* First, get the file size */
 368     if (fstat (fd, &st))
 369         return NULL;
 370
 371     /* st_size is meaningful for regular files, shared memory and typed memory.
 372      * It's also meaning for symlinks, but that's not possible with fstat().
 373      * In other cases, it's undefined, and we should really not go further. */
 374 #ifndef S_TYPEISSHM
 375 # define S_TYPEISSHM( buf ) (0)
 376 #endif
 377     if (S_ISDIR (st.st_mode))
 378     {
 379         errno = EISDIR;
 380         return NULL;
 381     }
 382     if (!S_ISREG (st.st_mode) && !S_TYPEISSHM (&st))
 383     {
 384         errno = ESPIPE;
 385         return NULL;
 386     }
 387
 388     /* Prevent an integer overflow in mmap() and malloc() */
 389     if ((uintmax_t)st.st_size >= SIZE_MAX)
 390     {
 391         errno = ENOMEM;
 392         return NULL;
 393     }
 394     length = (size_t)st.st_size;
 395
 396 #ifdef HAVE_MMAP
 397     if (length > 0)
 398     {
 399         int prot = PROT_READ | (write ? PROT_WRITE : 0);
 400         int flags = write ? MAP_PRIVATE : MAP_SHARED;
 401         void *addr = mmap(NULL, length, prot, flags, fd, 0);
 402
 403         if (addr != MAP_FAILED)
 404             return block_mmap_Alloc (addr, length);
 405     }
 406 #endif
 407
 408     /* If mmap() is not implemented by the OS _or_ the filesystem... */
 409     block_t *block = block_Alloc (length);
 410     if (block == NULL)
 411         return NULL;
 412     block_cleanup_push (block);
 413
 414     for (size_t i = 0; i < length;)
 415     {
 416         ssize_t len = pread (fd, block->p_buffer + i, length - i, i);
 417         if (len == -1)
 418         {
 419             block_Release (block);
 420             block = NULL;
 421             break;
 422         }
 423         i += len;
 424     }
 425     vlc_cleanup_pop ();
 426     return block;
 427 }
 428
 429 block_t *block_FilePath(const char *path, bool write)
 430 {
 431     /* NOTE: Writeable shared mappings are not supported here. So there are no
 432      * needs to open the file for writing (even if the mapping is writable). */
 433     int fd = vlc_open (path, O_RDONLY);
 434     if (fd == -1)
 435         return NULL;
 436
 437     block_t *block = block_File(fd, write);
 438     vlc_close (fd);
 439     return block;
 440 }