pulseaudio/src/pulsecore/memblockq.c

/***
  This file is part of PulseAudio.

  Copyright 2004-2006 Lennart Poettering

  PulseAudio 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.

  PulseAudio 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 Lesser General Public License
  along with PulseAudio; if not, write to the Free Software
  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
  USA.
***/

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include <pulse/xmalloc.h>

#include <pulsecore/log.h>
#include <pulsecore/mcalign.h>
#include <pulsecore/macro.h>
#include <pulsecore/flist.h>

#include "memblockq.h"

/* #define MEMBLOCKQ_DEBUG */

struct list_item {
    struct list_item *next, *prev;
    int64_t index;
    pa_memchunk chunk;
};

PA_STATIC_FLIST_DECLARE(list_items, 0, pa_xfree);

struct pa_memblockq {
    struct list_item *blocks, *blocks_tail;
    struct list_item *current_read, *current_write;
    unsigned n_blocks;
    size_t maxlength, tlength, base, prebuf, minreq, maxrewind;
    int64_t read_index, write_index;
    pa_bool_t in_prebuf;
    pa_memchunk silence;
    pa_mcalign *mcalign;
    int64_t missing, requested;
    char *name;
    pa_sample_spec sample_spec;
};

pa_memblockq* pa_memblockq_new(
        const char *name,
        int64_t idx,
        size_t maxlength,
        size_t tlength,
        const pa_sample_spec *sample_spec,
        size_t prebuf,
        size_t minreq,
        size_t maxrewind,
        pa_memchunk *silence) {

    pa_memblockq* bq;

    pa_assert(sample_spec);
    pa_assert(name);

    bq = pa_xnew0(pa_memblockq, 1);
    bq->name = pa_xstrdup(name);

    bq->sample_spec = *sample_spec;
    bq->base = pa_frame_size(sample_spec);
    bq->read_index = bq->write_index = idx;

    pa_log_debug("memblockq requested: maxlength=%lu, tlength=%lu, base=%lu, prebuf=%lu, minreq=%lu maxrewind=%lu",
                 (unsigned long) maxlength, (unsigned long) tlength, (unsigned long) bq->base, (unsigned long) prebuf, (unsigned long) minreq, (unsigned long) maxrewind);

    bq->in_prebuf = TRUE;

    pa_memblockq_set_maxlength(bq, maxlength);
    pa_memblockq_set_tlength(bq, tlength);
    pa_memblockq_set_minreq(bq, minreq);
    pa_memblockq_set_prebuf(bq, prebuf);
    pa_memblockq_set_maxrewind(bq, maxrewind);

    pa_log_debug("memblockq sanitized: maxlength=%lu, tlength=%lu, base=%lu, prebuf=%lu, minreq=%lu maxrewind=%lu",
                 (unsigned long) bq->maxlength, (unsigned long) bq->tlength, (unsigned long) bq->base, (unsigned long) bq->prebuf, (unsigned long) bq->minreq, (unsigned long) bq->maxrewind);

    if (silence) {
        bq->silence = *silence;
        pa_memblock_ref(bq->silence.memblock);
    }

    bq->mcalign = pa_mcalign_new(bq->base);

    return bq;
}

void pa_memblockq_free(pa_memblockq* bq) {
    pa_assert(bq);

    pa_memblockq_silence(bq);

    if (bq->silence.memblock)
        pa_memblock_unref(bq->silence.memblock);

    if (bq->mcalign)
        pa_mcalign_free(bq->mcalign);

    pa_xfree(bq->name);
    pa_xfree(bq);
}

static void fix_current_read(pa_memblockq *bq) {
    pa_assert(bq);

    if (PA_UNLIKELY(!bq->blocks)) {
        bq->current_read = NULL;
        return;
    }

    if (PA_UNLIKELY(!bq->current_read))
        bq->current_read = bq->blocks;

    /* Scan left */
    while (PA_UNLIKELY(bq->current_read->index > bq->read_index))

        if (bq->current_read->prev)
            bq->current_read = bq->current_read->prev;
        else
            break;

    /* Scan right */
    while (PA_LIKELY(bq->current_read != NULL) && PA_UNLIKELY(bq->current_read->index + (int64_t) bq->current_read->chunk.length <= bq->read_index))
        bq->current_read = bq->current_read->next;

    /* At this point current_read will either point at or left of the
       next block to play. It may be NULL in case everything in
       the queue was already played */
}

static void fix_current_write(pa_memblockq *bq) {
    pa_assert(bq);

    if (PA_UNLIKELY(!bq->blocks)) {
        bq->current_write = NULL;
        return;
    }

    if (PA_UNLIKELY(!bq->current_write))
        bq->current_write = bq->blocks_tail;

    /* Scan right */
    while (PA_UNLIKELY(bq->current_write->index + (int64_t) bq->current_write->chunk.length <= bq->write_index))

        if (bq->current_write->next)
            bq->current_write = bq->current_write->next;
        else
            break;

    /* Scan left */
    while (PA_LIKELY(bq->current_write != NULL) && PA_UNLIKELY(bq->current_write->index > bq->write_index))
        bq->current_write = bq->current_write->prev;

    /* At this point current_write will either point at or right of
       the next block to write data to. It may be NULL in case
       everything in the queue is still to be played */
}

static void drop_block(pa_memblockq *bq, struct list_item *q) {
    pa_assert(bq);
    pa_assert(q);

    pa_assert(bq->n_blocks >= 1);

    if (q->prev)
        q->prev->next = q->next;
    else {
        pa_assert(bq->blocks == q);
        bq->blocks = q->next;
    }

    if (q->next)
        q->next->prev = q->prev;
    else {
        pa_assert(bq->blocks_tail == q);
        bq->blocks_tail = q->prev;
    }

    if (bq->current_write == q)
        bq->current_write = q->prev;

    if (bq->current_read == q)
        bq->current_read = q->next;

    pa_memblock_unref(q->chunk.memblock);

    if (pa_flist_push(PA_STATIC_FLIST_GET(list_items), q) < 0)
        pa_xfree(q);

    bq->n_blocks--;
}

static void drop_backlog(pa_memblockq *bq) {
    int64_t boundary;
    pa_assert(bq);

    boundary = bq->read_index - (int64_t) bq->maxrewind;

    while (bq->blocks && (bq->blocks->index + (int64_t) bq->blocks->chunk.length <= boundary))
        drop_block(bq, bq->blocks);
}

static pa_bool_t can_push(pa_memblockq *bq, size_t l) {
    int64_t end;

    pa_assert(bq);

    if (bq->read_index > bq->write_index) {
        int64_t d = bq->read_index - bq->write_index;

        if ((int64_t) l > d)
            l -= (size_t) d;
        else
            return TRUE;
    }

    end = bq->blocks_tail ? bq->blocks_tail->index + (int64_t) bq->blocks_tail->chunk.length : bq->write_index;

    /* Make sure that the list doesn't get too long */
    if (bq->write_index + (int64_t) l > end)
        if (bq->write_index + (int64_t) l - bq->read_index > (int64_t) bq->maxlength)
            return FALSE;

    return TRUE;
}

static void write_index_changed(pa_memblockq *bq, int64_t old_write_index, pa_bool_t account) {
    int64_t delta;

    pa_assert(bq);

    delta = bq->write_index - old_write_index;

    if (account)
        bq->requested -= delta;
    else
        bq->missing -= delta;

#ifdef MEMBLOCKQ_DEBUG
     pa_log("[%s] pushed/seeked %lli: requested counter at %lli, account=%i", bq->name, (long long) delta, (long long) bq->requested, account);
#endif
}

static void read_index_changed(pa_memblockq *bq, int64_t old_read_index) {
    int64_t delta;

    pa_assert(bq);

    delta = bq->read_index - old_read_index;
    bq->missing += delta;

#ifdef MEMBLOCKQ_DEBUG
    pa_log("[%s] popped %lli: missing counter at %lli", bq->name, (long long) delta, (long long) bq->missing);
#endif
}

int pa_memblockq_push(pa_memblockq* bq, const pa_memchunk *uchunk) {
    struct list_item *q, *n;
    pa_memchunk chunk;
    int64_t old;

    pa_assert(bq);
    pa_assert(uchunk);
    pa_assert(uchunk->memblock);
    pa_assert(uchunk->length > 0);
    pa_assert(uchunk->index + uchunk->length <= pa_memblock_get_length(uchunk->memblock));

    if (uchunk->length % bq->base)
        return -1;

    if (!can_push(bq, uchunk->length))
        return -1;

    old = bq->write_index;
    chunk = *uchunk;

    fix_current_write(bq);
    q = bq->current_write;

    /* First we advance the q pointer right of where we want to
     * write to */

    if (q) {
        while (bq->write_index + (int64_t) chunk.length > q->index)
            if (q->next)
                q = q->next;
            else
                break;
    }

    if (!q)
        q = bq->blocks_tail;

    /* We go from back to front to look for the right place to add
     * this new entry. Drop data we will overwrite on the way */

    while (q) {

        if (bq->write_index >= q->index + (int64_t) q->chunk.length)
            /* We found the entry where we need to place the new entry immediately after */
            break;
        else if (bq->write_index + (int64_t) chunk.length <= q->index) {
            /* This entry isn't touched at all, let's skip it */
            q = q->prev;
        } else if (bq->write_index <= q->index &&
                   bq->write_index + (int64_t) chunk.length >= q->index + (int64_t) q->chunk.length) {

            /* This entry is fully replaced by the new entry, so let's drop it */

            struct list_item *p;
            p = q;
            q = q->prev;
            drop_block(bq, p);
        } else if (bq->write_index >= q->index) {
            /* The write index points into this memblock, so let's
             * truncate or split it */

            if (bq->write_index + (int64_t) chunk.length < q->index + (int64_t) q->chunk.length) {

                /* We need to save the end of this memchunk */
                struct list_item *p;
                size_t d;

                /* Create a new list entry for the end of the memchunk */
                if (!(p = pa_flist_pop(PA_STATIC_FLIST_GET(list_items))))
                    p = pa_xnew(struct list_item, 1);

                p->chunk = q->chunk;
                pa_memblock_ref(p->chunk.memblock);

                /* Calculate offset */
                d = (size_t) (bq->write_index + (int64_t) chunk.length - q->index);
                pa_assert(d > 0);

                /* Drop it from the new entry */
                p->index = q->index + (int64_t) d;
                p->chunk.length -= d;

                /* Add it to the list */
                p->prev = q;
                if ((p->next = q->next))
                    q->next->prev = p;
                else
                    bq->blocks_tail = p;
                q->next = p;

                bq->n_blocks++;
            }

            /* Truncate the chunk */
            if (!(q->chunk.length = (size_t) (bq->write_index - q->index))) {
                struct list_item *p;
                p = q;
                q = q->prev;
                drop_block(bq, p);
            }

            /* We had to truncate this block, hence we're now at the right position */
            break;
        } else {
            size_t d;

            pa_assert(bq->write_index + (int64_t)chunk.length > q->index &&
                      bq->write_index + (int64_t)chunk.length < q->index + (int64_t)q->chunk.length &&
                      bq->write_index < q->index);

            /* The job overwrites the current entry at the end, so let's drop the beginning of this entry */

            d = (size_t) (bq->write_index + (int64_t) chunk.length - q->index);
            q->index += (int64_t) d;
            q->chunk.index += d;
            q->chunk.length -= d;

            q = q->prev;
        }
    }

    if (q) {
        pa_assert(bq->write_index >=  q->index + (int64_t)q->chunk.length);
        pa_assert(!q->next || (bq->write_index + (int64_t)chunk.length <= q->next->index));

        /* Try to merge memory blocks */

        if (q->chunk.memblock == chunk.memblock &&
            q->chunk.index + q->chunk.length == chunk.index &&
            bq->write_index == q->index + (int64_t) q->chunk.length) {

            q->chunk.length += chunk.length;
            bq->write_index += (int64_t) chunk.length;
            goto finish;
        }
    } else
        pa_assert(!bq->blocks || (bq->write_index + (int64_t)chunk.length <= bq->blocks->index));

    if (!(n = pa_flist_pop(PA_STATIC_FLIST_GET(list_items))))
        n = pa_xnew(struct list_item, 1);

    n->chunk = chunk;
    pa_memblock_ref(n->chunk.memblock);
    n->index = bq->write_index;
    bq->write_index += (int64_t) n->chunk.length;

    n->next = q ? q->next : bq->blocks;
    n->prev = q;

    if (n->next)
        n->next->prev = n;
    else
        bq->blocks_tail = n;

    if (n->prev)
        n->prev->next = n;
    else
        bq->blocks = n;

    bq->n_blocks++;

finish:

    write_index_changed(bq, old, TRUE);
    return 0;
}

pa_bool_t pa_memblockq_prebuf_active(pa_memblockq *bq) {
    pa_assert(bq);

    if (bq->in_prebuf)
        return pa_memblockq_get_length(bq) < bq->prebuf;
    else
        return bq->prebuf > 0 && bq->read_index >= bq->write_index;
}

static pa_bool_t update_prebuf(pa_memblockq *bq) {
    pa_assert(bq);

    if (bq->in_prebuf) {

        if (pa_memblockq_get_length(bq) < bq->prebuf)
            return TRUE;

        bq->in_prebuf = FALSE;
        return FALSE;
    } else {

        if (bq->prebuf > 0 && bq->read_index >= bq->write_index) {
            bq->in_prebuf = TRUE;
            return TRUE;
        }

        return FALSE;
    }
}

int pa_memblockq_peek(pa_memblockq* bq, pa_memchunk *chunk) {
    int64_t d;
    pa_assert(bq);
    pa_assert(chunk);

    /* We need to pre-buffer */
    if (update_prebuf(bq))
        return -1;

    fix_current_read(bq);

    /* Do we need to spit out silence? */
    if (!bq->current_read || bq->current_read->index > bq->read_index) {
        size_t length;

        /* How much silence shall we return? */
        if (bq->current_read)
            length = (size_t) (bq->current_read->index - bq->read_index);
        else if (bq->write_index > bq->read_index)
            length = (size_t) (bq->write_index - bq->read_index);
        else
            length = 0;

        /* We need to return silence, since no data is yet available */
        if (bq->silence.memblock) {
            *chunk = bq->silence;
            pa_memblock_ref(chunk->memblock);

            if (length > 0 && length < chunk->length)
                chunk->length = length;

        } else {

            /* If the memblockq is empty, return -1, otherwise return
             * the time to sleep */
            if (length <= 0)
                return -1;

            chunk->memblock = NULL;
            chunk->length = length;
        }

        chunk->index = 0;
        return 0;
    }

    /* Ok, let's pass real data to the caller */
    *chunk = bq->current_read->chunk;
    pa_memblock_ref(chunk->memblock);

    pa_assert(bq->read_index >= bq->current_read->index);
    d = bq->read_index - bq->current_read->index;
    chunk->index += (size_t) d;
    chunk->length -= (size_t) d;

    return 0;
}

int pa_memblockq_peek_fixed_size(pa_memblockq *bq, size_t block_size, pa_memchunk *chunk) {
    pa_memchunk tchunk, rchunk;
    int64_t ri;
    struct list_item *item;

    pa_assert(bq);
    pa_assert(block_size > 0);
    pa_assert(chunk);
    pa_assert(bq->silence.memblock);

    if (pa_memblockq_peek(bq, &tchunk) < 0)
        return -1;

    if (tchunk.length >= block_size) {
        *chunk = tchunk;
        chunk->length = block_size;
        return 0;
    }

    rchunk.memblock = pa_memblock_new(pa_memblock_get_pool(tchunk.memblock), block_size);
    rchunk.index = 0;
    rchunk.length = tchunk.length;

    pa_memchunk_memcpy(&rchunk, &tchunk);
    pa_memblock_unref(tchunk.memblock);

    rchunk.index += tchunk.length;

    /* We don't need to call fix_current_read() here, since
     * pa_memblock_peek() already did that */
    item = bq->current_read;
    ri = bq->read_index + tchunk.length;

    while (rchunk.index < block_size) {

        if (!item || item->index > ri) {
            /* Do we need to append silence? */
            tchunk = bq->silence;

            if (item)
                tchunk.length = PA_MIN(tchunk.length, (size_t) (item->index - ri));

        } else {
            int64_t d;

            /* We can append real data! */
            tchunk = item->chunk;

            d = ri - item->index;
            tchunk.index += (size_t) d;
            tchunk.length -= (size_t) d;

            /* Go to next item for the next iteration */
            item = item->next;
        }

        rchunk.length = tchunk.length = PA_MIN(tchunk.length, block_size - rchunk.index);
        pa_memchunk_memcpy(&rchunk, &tchunk);

        rchunk.index += rchunk.length;
        ri += rchunk.length;
    }

    rchunk.index = 0;
    rchunk.length = block_size;

    *chunk = rchunk;
    return 0;
}

void pa_memblockq_drop(pa_memblockq *bq, size_t length) {
    int64_t old;
    pa_assert(bq);
    pa_assert(length % bq->base == 0);

    old = bq->read_index;

    while (length > 0) {

        /* Do not drop any data when we are in prebuffering mode */
        if (update_prebuf(bq))
            break;

        fix_current_read(bq);

        if (bq->current_read) {
            int64_t p, d;

            /* We go through this piece by piece to make sure we don't
             * drop more than allowed by prebuf */

            p = bq->current_read->index + (int64_t) bq->current_read->chunk.length;
            pa_assert(p >= bq->read_index);
            d = p - bq->read_index;

            if (d > (int64_t) length)
                d = (int64_t) length;

            bq->read_index += d;
            length -= (size_t) d;

        } else {

            /* The list is empty, there's nothing we could drop */
            bq->read_index += (int64_t) length;
            break;
        }
    }

    drop_backlog(bq);
    read_index_changed(bq, old);
}

void pa_memblockq_rewind(pa_memblockq *bq, size_t length) {
    int64_t old;
    pa_assert(bq);
    pa_assert(length % bq->base == 0);

    old = bq->read_index;

    /* This is kind of the inverse of pa_memblockq_drop() */

    bq->read_index -= (int64_t) length;

    read_index_changed(bq, old);
}

pa_bool_t pa_memblockq_is_readable(pa_memblockq *bq) {
    pa_assert(bq);

    if (pa_memblockq_prebuf_active(bq))
        return FALSE;

    if (pa_memblockq_get_length(bq) <= 0)
        return FALSE;

    return TRUE;
}

size_t pa_memblockq_get_length(pa_memblockq *bq) {
    pa_assert(bq);

    if (bq->write_index <= bq->read_index)
        return 0;

    return (size_t) (bq->write_index - bq->read_index);
}

size_t pa_memblockq_missing(pa_memblockq *bq) {
    size_t l;
    pa_assert(bq);

    if ((l = pa_memblockq_get_length(bq)) >= bq->tlength)
        return 0;

    l = bq->tlength - l;

    return l >= bq->minreq ? l : 0;
}

void pa_memblockq_seek(pa_memblockq *bq, int64_t offset, pa_seek_mode_t seek, pa_bool_t account) {
    int64_t old;
    pa_assert(bq);

    old = bq->write_index;

    switch (seek) {
        case PA_SEEK_RELATIVE:
            bq->write_index += offset;
            break;
        case PA_SEEK_ABSOLUTE:
            bq->write_index = offset;
            break;
        case PA_SEEK_RELATIVE_ON_READ:
            bq->write_index = bq->read_index + offset;
            break;
        case PA_SEEK_RELATIVE_END:
            bq->write_index = (bq->blocks_tail ? bq->blocks_tail->index + (int64_t) bq->blocks_tail->chunk.length : bq->read_index) + offset;
            break;
        default:
            pa_assert_not_reached();
    }

    drop_backlog(bq);
    write_index_changed(bq, old, account);
}

void pa_memblockq_flush_write(pa_memblockq *bq, pa_bool_t account) {
    int64_t old;
    pa_assert(bq);

    pa_memblockq_silence(bq);

    old = bq->write_index;
    bq->write_index = bq->read_index;

    pa_memblockq_prebuf_force(bq);
    write_index_changed(bq, old, account);
}

void pa_memblockq_flush_read(pa_memblockq *bq) {
    int64_t old;
    pa_assert(bq);

    pa_memblockq_silence(bq);

    old = bq->read_index;
    bq->read_index = bq->write_index;

    pa_memblockq_prebuf_force(bq);
    read_index_changed(bq, old);
}

size_t pa_memblockq_get_tlength(pa_memblockq *bq) {
    pa_assert(bq);

    return bq->tlength;
}

size_t pa_memblockq_get_minreq(pa_memblockq *bq) {
    pa_assert(bq);

    return bq->minreq;
}

size_t pa_memblockq_get_maxrewind(pa_memblockq *bq) {
    pa_assert(bq);

    return bq->maxrewind;
}

int64_t pa_memblockq_get_read_index(pa_memblockq *bq) {
    pa_assert(bq);

    return bq->read_index;
}

int64_t pa_memblockq_get_write_index(pa_memblockq *bq) {
    pa_assert(bq);

    return bq->write_index;
}

int pa_memblockq_push_align(pa_memblockq* bq, const pa_memchunk *chunk) {
    pa_memchunk rchunk;

    pa_assert(bq);
    pa_assert(chunk);

    if (bq->base == 1)
        return pa_memblockq_push(bq, chunk);

    if (!can_push(bq, pa_mcalign_csize(bq->mcalign, chunk->length)))
        return -1;

    pa_mcalign_push(bq->mcalign, chunk);

    while (pa_mcalign_pop(bq->mcalign, &rchunk) >= 0) {
        int r;
        r = pa_memblockq_push(bq, &rchunk);
        pa_memblock_unref(rchunk.memblock);

        if (r < 0) {
            pa_mcalign_flush(bq->mcalign);
            return -1;
        }
    }

    return 0;
}

void pa_memblockq_prebuf_disable(pa_memblockq *bq) {
    pa_assert(bq);

    bq->in_prebuf = FALSE;
}

void pa_memblockq_prebuf_force(pa_memblockq *bq) {
    pa_assert(bq);

    if (bq->prebuf > 0)
        bq->in_prebuf = TRUE;
}

size_t pa_memblockq_get_maxlength(pa_memblockq *bq) {
    pa_assert(bq);

    return bq->maxlength;
}

size_t pa_memblockq_get_prebuf(pa_memblockq *bq) {
    pa_assert(bq);

    return bq->prebuf;
}

size_t pa_memblockq_pop_missing(pa_memblockq *bq) {
    size_t l;

    pa_assert(bq);

#ifdef MEMBLOCKQ_DEBUG
    pa_log("[%s] pop: %lli", bq->name, (long long) bq->missing);
#endif

    if (bq->missing <= 0)
        return 0;

    l = (size_t) bq->missing;

    bq->requested += bq->missing;
    bq->missing = 0;

#ifdef MEMBLOCKQ_DEBUG
    pa_log("[%s] sent %lli: request counter is at %lli", bq->name, (long long) l, (long long) bq->requested);
#endif

    return l;
}

void pa_memblockq_set_maxlength(pa_memblockq *bq, size_t maxlength) {
    pa_assert(bq);

    bq->maxlength = ((maxlength+bq->base-1)/bq->base)*bq->base;

    if (bq->maxlength < bq->base)
        bq->maxlength = bq->base;

    if (bq->tlength > bq->maxlength)
        pa_memblockq_set_tlength(bq, bq->maxlength);
}

void pa_memblockq_set_tlength(pa_memblockq *bq, size_t tlength) {
    size_t old_tlength;
    pa_assert(bq);

    if (tlength <= 0 || tlength == (size_t) -1)
        tlength = bq->maxlength;

    old_tlength = bq->tlength;
    bq->tlength = ((tlength+bq->base-1)/bq->base)*bq->base;

    if (bq->tlength > bq->maxlength)
        bq->tlength = bq->maxlength;

    if (bq->minreq > bq->tlength)
        pa_memblockq_set_minreq(bq, bq->tlength);

    if (bq->prebuf > bq->tlength+bq->base-bq->minreq)
        pa_memblockq_set_prebuf(bq, bq->tlength+bq->base-bq->minreq);

    bq->missing += (int64_t) bq->tlength - (int64_t) old_tlength;
}

void pa_memblockq_set_minreq(pa_memblockq *bq, size_t minreq) {
    pa_assert(bq);

    bq->minreq = (minreq/bq->base)*bq->base;

    if (bq->minreq > bq->tlength)
        bq->minreq = bq->tlength;

    if (bq->minreq < bq->base)
        bq->minreq = bq->base;

    if (bq->prebuf > bq->tlength+bq->base-bq->minreq)
        pa_memblockq_set_prebuf(bq, bq->tlength+bq->base-bq->minreq);
}

void pa_memblockq_set_prebuf(pa_memblockq *bq, size_t prebuf) {
    pa_assert(bq);

    if (prebuf == (size_t) -1)
        prebuf = bq->tlength+bq->base-bq->minreq;

    bq->prebuf = ((prebuf+bq->base-1)/bq->base)*bq->base;

    if (prebuf > 0 && bq->prebuf < bq->base)
        bq->prebuf = bq->base;

    if (bq->prebuf > bq->tlength+bq->base-bq->minreq)
        bq->prebuf = bq->tlength+bq->base-bq->minreq;

    if (bq->prebuf <= 0 || pa_memblockq_get_length(bq) >= bq->prebuf)
        bq->in_prebuf = FALSE;
}

void pa_memblockq_set_maxrewind(pa_memblockq *bq, size_t maxrewind) {
    pa_assert(bq);

    bq->maxrewind = (maxrewind/bq->base)*bq->base;
}

void pa_memblockq_apply_attr(pa_memblockq *bq, const pa_buffer_attr *a) {
    pa_assert(bq);
    pa_assert(a);

    pa_memblockq_set_maxlength(bq, a->maxlength);
    pa_memblockq_set_tlength(bq, a->tlength);
    pa_memblockq_set_minreq(bq, a->minreq);
    pa_memblockq_set_prebuf(bq, a->prebuf);
}

void pa_memblockq_get_attr(pa_memblockq *bq, pa_buffer_attr *a) {
    pa_assert(bq);
    pa_assert(a);

    a->maxlength = (uint32_t) pa_memblockq_get_maxlength(bq);
    a->tlength = (uint32_t) pa_memblockq_get_tlength(bq);
    a->prebuf = (uint32_t) pa_memblockq_get_prebuf(bq);
    a->minreq = (uint32_t) pa_memblockq_get_minreq(bq);
}

int pa_memblockq_splice(pa_memblockq *bq, pa_memblockq *source) {

    pa_assert(bq);
    pa_assert(source);

    pa_memblockq_prebuf_disable(bq);

    for (;;) {
        pa_memchunk chunk;

        if (pa_memblockq_peek(source, &chunk) < 0)
            return 0;

        pa_assert(chunk.length > 0);

        if (chunk.memblock) {

            if (pa_memblockq_push_align(bq, &chunk) < 0) {
                pa_memblock_unref(chunk.memblock);
                return -1;
            }

            pa_memblock_unref(chunk.memblock);
        } else
            pa_memblockq_seek(bq, (int64_t) chunk.length, PA_SEEK_RELATIVE, TRUE);

        pa_memblockq_drop(bq, chunk.length);
    }
}

void pa_memblockq_willneed(pa_memblockq *bq) {
    struct list_item *q;

    pa_assert(bq);

    fix_current_read(bq);

    for (q = bq->current_read; q; q = q->next)
        pa_memchunk_will_need(&q->chunk);
}

void pa_memblockq_set_silence(pa_memblockq *bq, pa_memchunk *silence) {
    pa_assert(bq);

    if (bq->silence.memblock)
        pa_memblock_unref(bq->silence.memblock);

    if (silence) {
        bq->silence = *silence;
        pa_memblock_ref(bq->silence.memblock);
    } else
        pa_memchunk_reset(&bq->silence);
}

pa_bool_t pa_memblockq_is_empty(pa_memblockq *bq) {
    pa_assert(bq);

    return !bq->blocks;
}

void pa_memblockq_silence(pa_memblockq *bq) {
    pa_assert(bq);

    while (bq->blocks)
        drop_block(bq, bq->blocks);

    pa_assert(bq->n_blocks == 0);
}

unsigned pa_memblockq_get_nblocks(pa_memblockq *bq) {
    pa_assert(bq);

    return bq->n_blocks;
}

size_t pa_memblockq_get_base(pa_memblockq *bq) {
    pa_assert(bq);

    return bq->base;
}