[vlc] / src / misc / block.c

/*****************************************************************************
 * block.c: Data blocks management functions
 *****************************************************************************
 * Copyright (C) 2003-2004 VLC authors and VideoLAN
 * Copyright (C) 2007-2009 Rémi Denis-Courmont
 *
 * Authors: Laurent Aimar <fenrir@videolan.org>
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation; either version 2.1 of the License, or
 * (at your option) any later version.
 *
 * This program 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 Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
 *****************************************************************************/

/*****************************************************************************
 * Preamble
 *****************************************************************************/
#ifdef HAVE_CONFIG_H
# include "config.h"
#endif

#include <sys/stat.h>
#include <assert.h>
#include <errno.h>
#ifdef HAVE_UNISTD_H
# include <unistd.h>
#endif

#include <vlc_common.h>
#include <vlc_block.h>

/**
 * @section Block handling functions.
 */

#ifndef NDEBUG
static void BlockNoRelease( block_t *b )
{
    fprintf( stderr, "block %p has no release callback! This is a bug!\n", b );
    abort();
}
#endif

void block_Init( block_t *restrict b, void *buf, size_t size )
{
    /* Fill all fields to their default */
    b->p_next = NULL;
    b->p_buffer = buf;
    b->i_buffer = size;
    b->p_start = buf;
    b->i_size = size;
    b->i_flags = 0;
    b->i_nb_samples = 0;
    b->i_pts =
    b->i_dts = VLC_TS_INVALID;
    b->i_length = 0;
#ifndef NDEBUG
    b->pf_release = BlockNoRelease;
#endif
}

static void BlockRelease( block_t *p_block )
{
    free( p_block );
}

static void BlockMetaCopy( block_t *restrict out, const block_t *in )
{
    out->p_next    = in->p_next;
    out->i_nb_samples = in->i_nb_samples;
    out->i_dts     = in->i_dts;
    out->i_pts     = in->i_pts;
    out->i_flags   = in->i_flags;
    out->i_length  = in->i_length;
}

/* Memory alignment (must be a multiple of sizeof(void*) and a power of two) */
#define BLOCK_ALIGN        16
/* Initial reserved header and footer size (must be multiple of alignment) */
#define BLOCK_PADDING      32
/* Maximum size of reserved footer before we release with realloc() */
#define BLOCK_WASTE_SIZE   2048

block_t *block_Alloc (size_t size)
{
    /* 2 * BLOCK_PADDING: pre + post padding */
    const size_t alloc = sizeof (block_t) + BLOCK_ALIGN + (2 * BLOCK_PADDING)
                       + size;
    if (unlikely(alloc <= size))
        return NULL;

    block_t *b = malloc (alloc);
    if (unlikely(b == NULL))
        return NULL;

    block_Init (b, b + 1, alloc);
    static_assert ((BLOCK_PADDING % BLOCK_ALIGN) == 0,
                   "BLOCK_PADDING must be a multiple of BLOCK_ALIGN");
    b->p_buffer += BLOCK_PADDING + BLOCK_ALIGN - 1;
    b->p_buffer = (void *)(((uintptr_t)b->p_buffer) & ~(BLOCK_ALIGN - 1));
    b->i_buffer = size;
    b->pf_release = BlockRelease;
    return b;
}

block_t *block_Realloc( block_t *p_block, ssize_t i_prebody, size_t i_body )
{
    size_t requested = i_prebody + i_body;

    /* Corner case: empty block requested */
    if( i_prebody <= 0 && i_body <= (size_t)(-i_prebody) )
    {
        block_Release( p_block );
        return NULL;
    }

    assert( p_block->p_start <= p_block->p_buffer );
    assert( p_block->p_start + p_block->i_size
                                    >= p_block->p_buffer + p_block->i_buffer );

    /* Corner case: the current payload is discarded completely */
    if( i_prebody <= 0 && p_block->i_buffer <= (size_t)-i_prebody )
         p_block->i_buffer = 0; /* discard current payload */
    if( p_block->i_buffer == 0 )
    {
        if( requested <= p_block->i_size )
        {   /* Enough room: recycle buffer */
            size_t extra = p_block->i_size - requested;

            p_block->p_buffer = p_block->p_start + (extra / 2);
            p_block->i_buffer = requested;
            return p_block;
        }
        /* Not enough room: allocate a new buffer */
        block_t *p_rea = block_Alloc( requested );
        if( p_rea )
            BlockMetaCopy( p_rea, p_block );
        block_Release( p_block );
        return p_rea;
    }

    /* First, shrink payload */

    /* Pull payload start */
    if( i_prebody < 0 )
    {
        assert( p_block->i_buffer >= (size_t)-i_prebody );
        p_block->p_buffer -= i_prebody;
        p_block->i_buffer += i_prebody;
        i_body += i_prebody;
        i_prebody = 0;
    }

    /* Trim payload end */
    if( p_block->i_buffer > i_body )
        p_block->i_buffer = i_body;

    uint8_t *p_start = p_block->p_start;
    uint8_t *p_end = p_start + p_block->i_size;

    /* Second, reallocate the buffer if we lack space. This is done now to
     * minimize the payload size for memory copy. */
    assert( i_prebody >= 0 );
    if( (size_t)(p_block->p_buffer - p_start) < (size_t)i_prebody
     || (size_t)(p_end - p_block->p_buffer) < i_body )
    {
        block_t *p_rea = block_Alloc( requested );
        if( p_rea )
        {
            BlockMetaCopy( p_rea, p_block );
            p_rea->p_buffer += i_prebody;
            p_rea->i_buffer -= i_prebody;
            memcpy( p_rea->p_buffer, p_block->p_buffer, p_block->i_buffer );
        }
        block_Release( p_block );
        if( p_rea == NULL )
            return NULL;
        p_block = p_rea;
    }
    else
    /* We have a very large reserved footer now? Release some of it.
     * XXX it might not preserve the alignment of p_buffer */
    if( p_end - (p_block->p_buffer + i_body) > BLOCK_WASTE_SIZE )
    {
        block_t *p_rea = block_Alloc( requested );
        if( p_rea )
        {
            BlockMetaCopy( p_rea, p_block );
            p_rea->p_buffer += i_prebody;
            p_rea->i_buffer -= i_prebody;
            memcpy( p_rea->p_buffer, p_block->p_buffer, p_block->i_buffer );
            block_Release( p_block );
            p_block = p_rea;
        }
    }

    /* NOTE: p_start and p_end are corrupted from this point */

    /* Third, expand payload */

    /* Push payload start */
    if( i_prebody > 0 )
    {
        p_block->p_buffer -= i_prebody;
        p_block->i_buffer += i_prebody;
        i_body += i_prebody;
        i_prebody = 0;
    }

    /* Expand payload to requested size */
    p_block->i_buffer = i_body;

    return p_block;
}


static void block_heap_Release (block_t *block)
{
    free (block->p_start);
    free (block);
}

/**
 * Creates a block from a heap allocation.
 * This is provided by LibVLC so that manually heap-allocated blocks can safely
 * be deallocated even after the origin plugin has been unloaded from memory.
 *
 * When block_Release() is called, VLC will free() the specified pointer.
 *
 * @param ptr base address of the heap allocation (will be free()'d)
 * @param length bytes length of the heap allocation
 * @return NULL in case of error (ptr free()'d in that case), or a valid
 * block_t pointer.
 */
block_t *block_heap_Alloc (void *addr, size_t length)
{
    block_t *block = malloc (sizeof (*block));
    if (block == NULL)
    {
        free (addr);
        return NULL;
    }

    block_Init (block, addr, length);
    block->pf_release = block_heap_Release;
    return block;
}

#ifdef HAVE_MMAP
# include <sys/mman.h>

static void block_mmap_Release (block_t *block)
{
    munmap (block->p_start, block->i_size);
    free (block);
}

/**
 * Creates a block from a virtual address memory mapping (mmap).
 * This is provided by LibVLC so that mmap blocks can safely be deallocated
 * even after the allocating plugin has been unloaded from memory.
 *
 * @param addr base address of the mapping (as returned by mmap)
 * @param length length (bytes) of the mapping (as passed to mmap)
 * @return NULL if addr is MAP_FAILED, or an error occurred (in the later
 * case, munmap(addr, length) is invoked before returning).
 */
block_t *block_mmap_Alloc (void *addr, size_t length)
{
    if (addr == MAP_FAILED)
        return NULL;

    block_t *block = malloc (sizeof (*block));
    if (block == NULL)
    {
        munmap (addr, length);
        return NULL;
    }

    block_Init (block, addr, length);
    block->pf_release = block_mmap_Release;
    return block;
}
#else
block_t *block_mmap_Alloc (void *addr, size_t length)
{
    (void)addr; (void)length; return NULL;
}
#endif


#ifdef WIN32
# include <io.h>
# ifdef UNDER_CE
#  define _get_osfhandle(a) ((long) (a))
# endif

static
ssize_t pread (int fd, void *buf, size_t count, off_t offset)
{
    HANDLE handle = (HANDLE)(intptr_t)_get_osfhandle (fd);
    if (handle == INVALID_HANDLE_VALUE)
        return -1;

    OVERLAPPED olap; olap.Offset = offset; olap.OffsetHigh = (offset >> 32);
    DWORD written;
    /* This braindead API will override the file pointer even if we specify
     * an explicit read offset... So do not expect this to mix well with
     * regular read() calls. */
    if (ReadFile (handle, buf, count, &written, &olap))
        return written;
    return -1;
}
#elif !defined( HAVE_PREAD )
static
ssize_t pread(int fd, const void * buf, size_t size, off_t offset) {
    off_t offs0;
    ssize_t rd;
    if ((offs0 = lseek(fd, 0, SEEK_CUR)) == (off_t)-1) return -1;
    if (lseek(fd, offset, SEEK_SET) == (off_t)-1) return -1;
    rd = read(fd, (void *)buf, size);
    if (lseek(fd, offs0, SEEK_SET) == (off_t)-1) return -1;
    return rd;
}

static
ssize_t pwrite(int fd, const void * buf, size_t size, off_t offset) {
    off_t offs0;
    ssize_t wr;
    if ((offs0 = lseek(fd, 0, SEEK_CUR)) == (off_t)-1) return -1;
    if (lseek(fd, offset, SEEK_SET) == (off_t)-1) return -1;
    wr = write(fd, (void *)buf, size);
    if (lseek(fd, offs0, SEEK_SET) == (off_t)-1) return -1;
    return wr;
}
#endif

/**
 * Loads a file into a block of memory. If possible a private file mapping is
 * created. Otherwise, the file is read normally. On 32-bits platforms, this
 * function will not work for very large files, due to memory space
 * constraints. Cancellation point.
 *
 * @param fd file descriptor to load from
 * @return a new block with the file content at p_buffer, and file length at
 * i_buffer (release it with block_Release()), or NULL upon error (see errno).
 */
block_t *block_File (int fd)
{
    size_t length;
    struct stat st;

    /* First, get the file size */
    if (fstat (fd, &st))
        return NULL;

    /* st_size is meaningful for regular files, shared memory and typed memory.
     * It's also meaning for symlinks, but that's not possible with fstat().
     * In other cases, it's undefined, and we should really not go further. */
#ifndef S_TYPEISSHM
# define S_TYPEISSHM( buf ) (0)
#endif
    if (S_ISDIR (st.st_mode))
    {
        errno = EISDIR;
        return NULL;
    }
    if (!S_ISREG (st.st_mode) && !S_TYPEISSHM (&st))
    {
        errno = ESPIPE;
        return NULL;
    }

    /* Prevent an integer overflow in mmap() and malloc() */
    if (st.st_size >= SIZE_MAX)
    {
        errno = ENOMEM;
        return NULL;
    }
    length = (size_t)st.st_size;

#ifdef HAVE_MMAP
    if (length > 0)
    {
        void *addr;

        addr = mmap (NULL, length, PROT_READ|PROT_WRITE, MAP_PRIVATE, fd, 0);
        if (addr != MAP_FAILED)
            return block_mmap_Alloc (addr, length);
    }
#endif

    /* If mmap() is not implemented by the OS _or_ the filesystem... */
    block_t *block = block_Alloc (length);
    if (block == NULL)
        return NULL;
    block_cleanup_push (block);

    for (size_t i = 0; i < length;)
    {
        ssize_t len = pread (fd, block->p_buffer + i, length - i, i);
        if (len == -1)
        {
            block_Release (block);
            block = NULL;
            break;
        }
        i += len;
    }
    vlc_cleanup_pop ();
    return block;
}

/**
 * @section Thread-safe block queue functions
 */

/**
 * Internal state for block queues
 */
struct block_fifo_t
{
    vlc_mutex_t         lock;                         /* fifo data lock */
    vlc_cond_t          wait;      /**< Wait for data */
    vlc_cond_t          wait_room; /**< Wait for queue depth to shrink */

    block_t             *p_first;
    block_t             **pp_last;
    size_t              i_depth;
    size_t              i_size;
    bool          b_force_wake;
};

block_fifo_t *block_FifoNew( void )
{
    block_fifo_t *p_fifo = malloc( sizeof( block_fifo_t ) );
    if( !p_fifo )
        return NULL;

    vlc_mutex_init( &p_fifo->lock );
    vlc_cond_init( &p_fifo->wait );
    vlc_cond_init( &p_fifo->wait_room );
    p_fifo->p_first = NULL;
    p_fifo->pp_last = &p_fifo->p_first;
    p_fifo->i_depth = p_fifo->i_size = 0;
    p_fifo->b_force_wake = false;

    return p_fifo;
}

void block_FifoRelease( block_fifo_t *p_fifo )
{
    block_FifoEmpty( p_fifo );
    vlc_cond_destroy( &p_fifo->wait_room );
    vlc_cond_destroy( &p_fifo->wait );
    vlc_mutex_destroy( &p_fifo->lock );
    free( p_fifo );
}

void block_FifoEmpty( block_fifo_t *p_fifo )
{
    block_t *block;

    vlc_mutex_lock( &p_fifo->lock );
    block = p_fifo->p_first;
    if (block != NULL)
    {
        p_fifo->i_depth = p_fifo->i_size = 0;
        p_fifo->p_first = NULL;
        p_fifo->pp_last = &p_fifo->p_first;
    }
    vlc_cond_broadcast( &p_fifo->wait_room );
    vlc_mutex_unlock( &p_fifo->lock );

    while (block != NULL)
    {
        block_t *buf;

        buf = block->p_next;
        block_Release (block);
        block = buf;
    }
}

/**
 * Wait until the FIFO gets below a certain size (if needed).
 *
 * Note that if more than one thread writes to the FIFO, you cannot assume that
 * the FIFO is actually below the requested size upon return (since another
 * thread could have refilled it already). This is typically not an issue, as
 * this function is meant for (relaxed) congestion control.
 *
 * This function may be a cancellation point and it is cancel-safe.
 *
 * @param fifo queue to wait on
 * @param max_depth wait until the queue has no more than this many blocks
 *                  (use SIZE_MAX to ignore this constraint)
 * @param max_size wait until the queue has no more than this many bytes
 *                  (use SIZE_MAX to ignore this constraint)
 * @return nothing.
 */
void block_FifoPace (block_fifo_t *fifo, size_t max_depth, size_t max_size)
{
    vlc_testcancel ();

    vlc_mutex_lock (&fifo->lock);
    while ((fifo->i_depth > max_depth) || (fifo->i_size > max_size))
    {
         mutex_cleanup_push (&fifo->lock);
         vlc_cond_wait (&fifo->wait_room, &fifo->lock);
         vlc_cleanup_pop ();
    }
    vlc_mutex_unlock (&fifo->lock);
}

/**
 * Immediately queue one block at the end of a FIFO.
 * @param fifo queue
 * @param block head of a block list to queue (may be NULL)
 * @return total number of bytes appended to the queue
 */
size_t block_FifoPut( block_fifo_t *p_fifo, block_t *p_block )
{
    size_t i_size = 0, i_depth = 0;
    block_t *p_last;

    if (p_block == NULL)
        return 0;
    for (p_last = p_block; ; p_last = p_last->p_next)
    {
        i_size += p_last->i_buffer;
        i_depth++;
        if (!p_last->p_next)
            break;
    }

    vlc_mutex_lock (&p_fifo->lock);
    *p_fifo->pp_last = p_block;
    p_fifo->pp_last = &p_last->p_next;
    p_fifo->i_depth += i_depth;
    p_fifo->i_size += i_size;
    /* We queued at least one block: wake up one read-waiting thread */
    vlc_cond_signal( &p_fifo->wait );
    vlc_mutex_unlock( &p_fifo->lock );

    return i_size;
}

void block_FifoWake( block_fifo_t *p_fifo )
{
    vlc_mutex_lock( &p_fifo->lock );
    if( p_fifo->p_first == NULL )
        p_fifo->b_force_wake = true;
    vlc_cond_broadcast( &p_fifo->wait );
    vlc_mutex_unlock( &p_fifo->lock );
}

/**
 * Dequeue the first block from the FIFO. If necessary, wait until there is
 * one block in the queue. This function is (always) cancellation point.
 *
 * @return a valid block, or NULL if block_FifoWake() was called.
 */
block_t *block_FifoGet( block_fifo_t *p_fifo )
{
    block_t *b;

    vlc_testcancel( );

    vlc_mutex_lock( &p_fifo->lock );
    mutex_cleanup_push( &p_fifo->lock );

    /* Remember vlc_cond_wait() may cause spurious wakeups
     * (on both Win32 and POSIX) */
    while( ( p_fifo->p_first == NULL ) && !p_fifo->b_force_wake )
        vlc_cond_wait( &p_fifo->wait, &p_fifo->lock );

    vlc_cleanup_pop();
    b = p_fifo->p_first;

    p_fifo->b_force_wake = false;
    if( b == NULL )
    {
        /* Forced wakeup */
        vlc_mutex_unlock( &p_fifo->lock );
        return NULL;
    }

    p_fifo->p_first = b->p_next;
    p_fifo->i_depth--;
    p_fifo->i_size -= b->i_buffer;

    if( p_fifo->p_first == NULL )
    {
        p_fifo->pp_last = &p_fifo->p_first;
    }

    /* We don't know how many threads can queue new packets now. */
    vlc_cond_broadcast( &p_fifo->wait_room );
    vlc_mutex_unlock( &p_fifo->lock );

    b->p_next = NULL;
    return b;
}

/**
 * Peeks the first block in the FIFO.
 * If necessary, wait until there is one block.
 * This function is (always) a cancellation point.
 *
 * @warning This function leaves the block in the FIFO.
 * You need to protect against concurrent threads who could dequeue the block.
 * Preferrably, there should be only one thread reading from the FIFO.
 *
 * @return a valid block.
 */
block_t *block_FifoShow( block_fifo_t *p_fifo )
{
    block_t *b;

    vlc_testcancel( );

    vlc_mutex_lock( &p_fifo->lock );
    mutex_cleanup_push( &p_fifo->lock );

    while( p_fifo->p_first == NULL )
        vlc_cond_wait( &p_fifo->wait, &p_fifo->lock );

    b = p_fifo->p_first;

    vlc_cleanup_run ();
    return b;
}

/* FIXME: not thread-safe */
size_t block_FifoSize( const block_fifo_t *p_fifo )
{
    return p_fifo->i_size;
}

/* FIXME: not thread-safe */
size_t block_FifoCount( const block_fifo_t *p_fifo )
{
    return p_fifo->i_depth;
}