Merge branch 't/flac'
[paraslash.git] / buffer_tree.c
1 /*
2 * Copyright (C) 2009-2011 Andre Noll <maan@systemlinux.org>
3 *
4 * Licensed under the GPL v2. For licencing details see COPYING.
5 */
6
7 /** \file buffer_tree.c Buffer tree and buffer pool implementations. */
8 #include <regex.h>
9 #include <stdbool.h>
10
11 #include "para.h"
12 #include "list.h"
13 #include "string.h"
14 #include "buffer_tree.h"
15 #include "error.h"
16 #include "sched.h"
17
18 /* whead = NULL means area full */
19 struct btr_pool {
20 char *name;
21 char *area_start;
22 char *area_end;
23 char *rhead;
24 char *whead;
25 };
26
27 struct btr_buffer {
28 char *buf;
29 size_t size;
30 /** The number of references to this buffer. */
31 int refcount;
32 /* NULL means no buffer pool but a malloced buffer. */
33 struct btr_pool *pool;
34 };
35
36 struct btr_buffer_reference {
37 struct btr_buffer *btrb;
38 size_t consumed;
39 /* Each buffer reference belongs to the buffer queue list of some buffer tree node. */
40 struct list_head node;
41 size_t wrap_count;
42 };
43
44 struct btr_node {
45 char *name;
46 struct btr_node *parent;
47 /* The position of this btr node in the buffer tree. */
48 struct list_head node;
49 /* The children nodes of this btr node are linked together in a list. */
50 struct list_head children;
51 /* Time of first data transfer. */
52 struct timeval start;
53 /**
54 * The input queue is a list of references to btr buffers. Each item on
55 * the list represents an input buffer which has not been completely
56 * used by this btr node.
57 */
58 struct list_head input_queue;
59 btr_command_handler execute;
60 void *context;
61 };
62
63 /**
64 * Create a new buffer pool.
65 *
66 * \param name The name of the new buffer pool.
67 * \param area_size The size in bytes of the pool area.
68 *
69 * \return An opaque pointer to the newly created buffer pool. It must be
70 * passed to btr_pool_free() after it is no longer used to deallocate all
71 * resources.
72 */
73 struct btr_pool *btr_pool_new(const char *name, size_t area_size)
74 {
75 struct btr_pool *btrp;
76
77 PARA_INFO_LOG("%s, %zu bytes\n", name, area_size);
78 btrp = para_malloc(sizeof(*btrp));
79 btrp->area_start = para_malloc(area_size);
80 btrp->area_end = btrp->area_start + area_size;
81 btrp->rhead = btrp->area_start;
82 btrp->whead = btrp->area_start;
83 btrp->name = para_strdup(name);
84 return btrp;
85 }
86
87 /**
88 * Deallocate resources used by a buffer pool.
89 *
90 * \param btrp A pointer obtained via btr_pool_new().
91 */
92 void btr_pool_free(struct btr_pool *btrp)
93 {
94 if (!btrp)
95 return;
96 free(btrp->area_start);
97 free(btrp->name);
98 free(btrp);
99 }
100
101 /**
102 * Return the size of the buffer pool area.
103 *
104 * \param btrp The buffer pool.
105 *
106 * \return The same value which was passed during creation time to
107 * btr_pool_new().
108 */
109 size_t btr_pool_size(struct btr_pool *btrp)
110 {
111 return btrp->area_end - btrp->area_start;
112 }
113
114 static size_t btr_pool_filled(struct btr_pool *btrp)
115 {
116 if (!btrp->whead)
117 return btr_pool_size(btrp);
118 if (btrp->rhead <= btrp->whead)
119 return btrp->whead - btrp->rhead;
120 return btr_pool_size(btrp) - (btrp->rhead - btrp->whead);
121 }
122
123 /**
124 * Get the number of unused bytes in the buffer pool.
125 *
126 * \param btrp The pool.
127 *
128 * \return The number of bytes that can currently be allocated.
129 *
130 * Note that in general the returned number of bytes is not available as a
131 * single contiguous buffer. Use btr_pool_available() to obtain the length of
132 * the largest contiguous buffer that can currently be allocated from the
133 * buffer pool.
134 */
135 size_t btr_pool_unused(struct btr_pool *btrp)
136 {
137 return btr_pool_size(btrp) - btr_pool_filled(btrp);
138 }
139
140 /*
141 * Return maximal size available for one read. This is
142 * smaller than the value returned by btr_pool_unused().
143 */
144 static size_t btr_pool_available(struct btr_pool *btrp)
145 {
146 if (!btrp->whead)
147 return 0;
148 if (btrp->rhead <= btrp->whead)
149 return btrp->area_end - btrp->whead;
150 return btrp->rhead - btrp->whead;
151 }
152
153 /**
154 * Obtain the current write head.
155 *
156 * \param btrp The buffer pool.
157 * \param result The write head is returned here.
158 *
159 * \return The maximal amount of bytes that may be written to the returned
160 * buffer.
161 */
162 size_t btr_pool_get_buffer(struct btr_pool *btrp, char **result)
163 {
164 if (result)
165 *result = btrp->whead;
166 return btr_pool_available(btrp);
167 }
168
169 /**
170 * Get references to buffers pointing to free space of the buffer pool area.
171 *
172 * \param btrp The buffer pool.
173 * \param iov The scatter array.
174 *
175 * \return Zero if the buffer pool is full, one if the free space of the buffer
176 * pool area is available as a single contiguous buffer, two if the free space
177 * consists of two buffers. If this function returns the value n, then n
178 * elements of \a iov are initialized.
179 */
180 int btr_pool_get_buffers(struct btr_pool *btrp, struct iovec iov[2])
181 {
182 size_t sz, unused;
183 char *buf;
184
185 sz = btr_pool_get_buffer(btrp, &buf);
186 if (sz == 0)
187 return 0;
188 iov[0].iov_len = sz;
189 iov[0].iov_base = buf;
190 unused = btr_pool_unused(btrp);
191 if (sz == unused)
192 return 1;
193 iov[1].iov_len = unused - sz;
194 iov[1].iov_base = btrp->area_start;
195 return 2;
196 }
197
198 /**
199 * Mark a part of the buffer pool area as allocated.
200 *
201 * \param btrp The buffer pool.
202 * \param size The amount of bytes to be allocated.
203 *
204 * This is usually called after the caller wrote to the buffer obtained by
205 * btr_pool_get_buffer().
206 */
207 static void btr_pool_allocate(struct btr_pool *btrp, size_t size)
208 {
209 char *end;
210
211 if (size == 0)
212 return;
213 assert(size <= btr_pool_available(btrp));
214 end = btrp->whead + size;
215 assert(end <= btrp->area_end);
216
217 if (end == btrp->area_end) {
218 PARA_DEBUG_LOG("%s: end of pool area reached\n", btrp->name);
219 end = btrp->area_start;
220 }
221 if (end == btrp->rhead) {
222 PARA_DEBUG_LOG("%s btrp buffer full\n", btrp->name);
223 end = NULL; /* buffer full */
224 }
225 btrp->whead = end;
226 }
227
228 static void btr_pool_deallocate(struct btr_pool *btrp, size_t size)
229 {
230 char *end = btrp->rhead + size;
231
232 if (size == 0)
233 return;
234 assert(end <= btrp->area_end);
235 assert(size <= btr_pool_filled(btrp));
236 if (end == btrp->area_end)
237 end = btrp->area_start;
238 if (!btrp->whead)
239 btrp->whead = btrp->rhead;
240 btrp->rhead = end;
241 if (btrp->rhead == btrp->whead)
242 btrp->rhead = btrp->whead = btrp->area_start;
243 }
244
245 #define FOR_EACH_CHILD(_tn, _btrn) list_for_each_entry((_tn), \
246 &((_btrn)->children), node)
247 #define FOR_EACH_CHILD_SAFE(_tn, _tmp, _btrn) \
248 list_for_each_entry_safe((_tn), (_tmp), &((_btrn)->children), node)
249
250 #define FOR_EACH_BUFFER_REF(_br, _btrn) \
251 list_for_each_entry((_br), &(_btrn)->input_queue, node)
252 #define FOR_EACH_BUFFER_REF_SAFE(_br, _tmp, _btrn) \
253 list_for_each_entry_safe((_br), (_tmp), &(_btrn)->input_queue, node)
254
255 /**
256 * Create a new buffer tree node.
257 *
258 * \param bnd Specifies how to create the new node.
259 *
260 * \return A pointer to the newly allocated node.
261 *
262 * This function always succeeds (or calls exit()). The returned pointer must
263 * be freed using btr_free_node() after the node has been removed from the
264 * buffer tree via btr_remove_node().
265 */
266 struct btr_node *btr_new_node(struct btr_node_description *bnd)
267 {
268 struct btr_node *btrn = para_malloc(sizeof(*btrn));
269
270 btrn->name = para_strdup(bnd->name);
271 btrn->parent = bnd->parent;
272 btrn->execute = bnd->handler;
273 btrn->context = bnd->context;
274 btrn->start.tv_sec = 0;
275 btrn->start.tv_usec = 0;
276 INIT_LIST_HEAD(&btrn->children);
277 INIT_LIST_HEAD(&btrn->input_queue);
278 if (!bnd->child) {
279 if (bnd->parent) {
280 list_add_tail(&btrn->node, &bnd->parent->children);
281 PARA_INFO_LOG("new leaf node: %s (child of %s)\n",
282 bnd->name, bnd->parent->name);
283 } else
284 PARA_INFO_LOG("added %s as btr root\n", bnd->name);
285 goto out;
286 }
287 if (!bnd->parent) {
288 assert(!bnd->child->parent);
289 PARA_INFO_LOG("new root: %s (was %s)\n",
290 bnd->name, bnd->child->name);
291 btrn->parent = NULL;
292 list_add_tail(&bnd->child->node, &btrn->children);
293 /* link it in */
294 bnd->child->parent = btrn;
295 goto out;
296 }
297 PARA_EMERG_LOG("inserting internal nodes not yet supported.\n");
298 exit(EXIT_FAILURE);
299 assert(bnd->child->parent == bnd->parent);
300 out:
301 return btrn;
302 }
303
304 /*
305 * Allocate a new btr buffer.
306 *
307 * The freshly allocated buffer will have a zero refcount and will
308 * not be associated with a btr pool.
309 */
310 static struct btr_buffer *new_btrb(char *buf, size_t size)
311 {
312 struct btr_buffer *btrb = para_calloc(sizeof(*btrb));
313
314 btrb->buf = buf;
315 btrb->size = size;
316 return btrb;
317 }
318
319 static void dealloc_buffer(struct btr_buffer *btrb)
320 {
321 if (btrb->pool)
322 btr_pool_deallocate(btrb->pool, btrb->size);
323 else
324 free(btrb->buf);
325 }
326
327 static struct btr_buffer_reference *get_first_input_br(struct btr_node *btrn)
328 {
329 if (list_empty(&btrn->input_queue))
330 return NULL;
331 return list_first_entry(&btrn->input_queue,
332 struct btr_buffer_reference, node);
333 }
334
335 /*
336 * Deallocate the reference, release the resources if refcount drops to zero.
337 */
338 static void btr_drop_buffer_reference(struct btr_buffer_reference *br)
339 {
340 struct btr_buffer *btrb = br->btrb;
341
342 list_del(&br->node);
343 free(br);
344 btrb->refcount--;
345 if (btrb->refcount == 0) {
346 dealloc_buffer(btrb);
347 free(btrb);
348 }
349 }
350
351 static void add_btrb_to_children(struct btr_buffer *btrb,
352 struct btr_node *btrn, size_t consumed)
353 {
354 struct btr_node *ch;
355
356 if (btrn->start.tv_sec == 0)
357 btrn->start = *now;
358 FOR_EACH_CHILD(ch, btrn) {
359 struct btr_buffer_reference *br = para_calloc(sizeof(*br));
360 br->btrb = btrb;
361 br->consumed = consumed;
362 list_add_tail(&br->node, &ch->input_queue);
363 btrb->refcount++;
364 if (ch->start.tv_sec == 0)
365 ch->start = *now;
366 }
367 }
368
369 /**
370 * Insert a malloced buffer into the buffer tree.
371 *
372 * \param buf The buffer to insert.
373 * \param size The size of \a buf in bytes.
374 * \param btrn Position in the buffer tree to create the output.
375 *
376 * This creates references to \a buf and adds these references to each child of
377 * \a btrn. The buffer will be freed using standard free() once no buffer tree
378 * node is referencing it any more.
379 *
380 * Note that this function must not be used if \a buf was obtained from a
381 * buffer pool. Use btr_add_output_pool() in this case.
382 */
383 void btr_add_output(char *buf, size_t size, struct btr_node *btrn)
384 {
385 struct btr_buffer *btrb;
386
387 assert(size != 0);
388 if (list_empty(&btrn->children)) {
389 free(buf);
390 return;
391 }
392 btrb = new_btrb(buf, size);
393 add_btrb_to_children(btrb, btrn, 0);
394 }
395
396 /**
397 * Feed data to child nodes of a buffer tree node.
398 *
399 * \param btrp The buffer pool.
400 * \param size The number of bytes to be allocated and fed to each child.
401 * \param btrn The node whose children are to be fed.
402 *
403 * This function allocates the amount of bytes from the buffer pool area,
404 * starting at the current value of the write head, and creates buffer
405 * references to the resulting part of the buffer pool area, one for each child
406 * of \a btrn. The references are then fed into the input queue of each child.
407 */
408 void btr_add_output_pool(struct btr_pool *btrp, size_t size,
409 struct btr_node *btrn)
410 {
411 struct btr_buffer *btrb;
412 char *buf;
413 size_t avail;
414
415 assert(size != 0);
416 if (list_empty(&btrn->children))
417 return;
418 avail = btr_pool_get_buffer(btrp, &buf);
419 assert(avail >= size);
420 btr_pool_allocate(btrp, size);
421 btrb = new_btrb(buf, size);
422 btrb->pool = btrp;
423 add_btrb_to_children(btrb, btrn, 0);
424 }
425
426 /**
427 * Copy data to write head of a buffer pool and feed it to all children nodes.
428 *
429 * \param src The source buffer.
430 * \param n The size of the source buffer in bytes.
431 * \param btrp The destination buffer pool.
432 * \param btrn Add the data as output of this node.
433 *
434 * This is expensive. The caller must make sure the data fits into the buffer
435 * pool area.
436 */
437 void btr_copy(const void *src, size_t n, struct btr_pool *btrp,
438 struct btr_node *btrn)
439 {
440 char *buf;
441 size_t sz, copy;
442
443 if (n == 0)
444 return;
445 assert(n <= btr_pool_unused(btrp));
446 sz = btr_pool_get_buffer(btrp, &buf);
447 copy = PARA_MIN(sz, n);
448 memcpy(buf, src, copy);
449 btr_add_output_pool(btrp, copy, btrn);
450 if (copy == n)
451 return;
452 sz = btr_pool_get_buffer(btrp, &buf);
453 assert(sz >= n - copy);
454 memcpy(buf, src + copy, n - copy);
455 btr_add_output_pool(btrp, n - copy, btrn);
456 }
457
458 static void btr_pushdown_br(struct btr_buffer_reference *br, struct btr_node *btrn)
459 {
460 add_btrb_to_children(br->btrb, btrn, br->consumed);
461 btr_drop_buffer_reference(br);
462 }
463
464 /**
465 * Feed all buffer references of the input queue through the output channel.
466 *
467 * \param btrn The node whose buffer references should be pushed down.
468 *
469 * This function is useful for filters that do not change the contents of the
470 * buffers at all, like the wav filter or the amp filter if no amplification
471 * was specified. This function is rather cheap.
472 *
473 * \sa \ref btr_pushdown_one().
474 */
475 void btr_pushdown(struct btr_node *btrn)
476 {
477 struct btr_buffer_reference *br, *tmp;
478
479 FOR_EACH_BUFFER_REF_SAFE(br, tmp, btrn)
480 btr_pushdown_br(br, btrn);
481 }
482
483 /**
484 * Feed the next buffer of the input queue through the output channel.
485 *
486 * \param btrn The node whose first input queue buffer should be pushed down.
487 *
488 * This works like \ref btr_pushdown() but pushes down only one buffer
489 * reference.
490 */
491 void btr_pushdown_one(struct btr_node *btrn)
492 {
493 struct btr_buffer_reference *br;
494
495 if (list_empty(&btrn->input_queue))
496 return;
497 br = list_first_entry(&btrn->input_queue, struct btr_buffer_reference, node);
498 btr_pushdown_br(br, btrn);
499 }
500
501 /*
502 * Find out whether a node is a leaf node.
503 *
504 * \param btrn The node to check.
505 *
506 * \return True if this node has no children. False otherwise.
507 */
508 static bool btr_no_children(struct btr_node *btrn)
509 {
510 return list_empty(&btrn->children);
511 }
512
513 /**
514 * Find out whether a node is an orphan node.
515 *
516 * \param btrn The buffer tree node.
517 *
518 * \return True if \a btrn has no parent.
519 *
520 * This function will always return true for the root node. However in case
521 * nodes have been removed from the tree, other nodes may become orphans too.
522 */
523 bool btr_no_parent(struct btr_node *btrn)
524 {
525 return !btrn->parent;
526 }
527
528 /**
529 * Find out whether it is OK to change an input buffer.
530 *
531 * \param btrn The buffer tree node to check.
532 *
533 * This is used by filters that produce exactly the same amount of output as
534 * there is input. The amp filter which multiplies each sample by some number
535 * is an example of such a filter. If there are no other nodes in the buffer
536 * tree that read the same input stream (i.e. if \a btrn has no siblings), a
537 * node may modify its input buffer directly and push down the modified buffer
538 * to its children, thereby avoiding to allocate a possibly large additional
539 * buffer.
540 *
541 * Since the buffer tree may change at any time, this function should be called
542 * during each post_select call.
543 *
544 * \return True if \a btrn has no siblings.
545 */
546 bool btr_inplace_ok(struct btr_node *btrn)
547 {
548 if (!btrn->parent)
549 return true;
550 return list_is_singular(&btrn->parent->children);
551 }
552
553 static inline size_t br_available_bytes(struct btr_buffer_reference *br)
554 {
555 return br->btrb->size - br->consumed;
556 }
557
558 static size_t btr_get_buffer_by_reference(struct btr_buffer_reference *br, char **buf)
559 {
560 if (buf)
561 *buf = br->btrb->buf + br->consumed;
562 return br_available_bytes(br);
563 }
564
565 /**
566 * Obtain the next buffer of the input queue, omitting data.
567 *
568 * \param btrn The node whose input queue is to be queried.
569 * \param omit Number of bytes to be omitted.
570 * \param bufp Result pointer.
571 *
572 * If a buffer tree node needs more input data but can not consume the data it
573 * already has (because it might be needed again later) this function can be
574 * used instead of btr_next_buffer() to get a reference to the buffer obtained
575 * by skipping the given number of bytes. Skipped input bytes are not consumed.
576 *
577 * With a zero \a omit argument, this function is equivalent to \ref
578 * btr_next_buffer().
579 *
580 * \return Number of bytes in \a bufp. If there are less than or equal to \a
581 * omit many bytes available in the input queue of the buffer tree node pointed
582 * to by \a btrn, the function returns zero and the value of \a bufp is
583 * undefined.
584 */
585 size_t btr_next_buffer_omit(struct btr_node *btrn, size_t omit, char **bufp)
586 {
587 struct btr_buffer_reference *br;
588 size_t wrap_count, sz, rv = 0;
589 char *buf, *result = NULL;
590
591 br = get_first_input_br(btrn);
592 if (!br)
593 return 0;
594 wrap_count = br->wrap_count;
595 if (wrap_count > 0) { /* we have a wrap buffer */
596 sz = btr_get_buffer_by_reference(br, &buf);
597 if (sz > omit) { /* and it's big enough */
598 result = buf + omit;
599 rv = sz - omit;
600 /*
601 * Wrap buffers are allocated by malloc(), so the next
602 * buffer ref will not align nicely, so we return the
603 * tail of the wrap buffer.
604 */
605 goto out;
606 }
607 /*
608 * The next wrap_count bytes exist twice, in the wrap buffer
609 * and as a buffer reference in the buffer tree pool.
610 */
611 omit += wrap_count;
612 }
613 /*
614 * For buffer tree pools, the buffers in the list align, i.e. the next
615 * buffer in the list starts directly at the end of its predecessor. In
616 * this case we merge adjacent buffers and return one larger buffer
617 * instead.
618 */
619 FOR_EACH_BUFFER_REF(br, btrn) {
620 sz = btr_get_buffer_by_reference(br, &buf);
621 if (result) {
622 if (result + rv != buf)
623 goto out;
624 rv += sz;
625 } else if (sz > omit) {
626 result = buf + omit;
627 rv = sz - omit;
628 } else
629 omit -= sz;
630 }
631 if (!result)
632 return 0;
633 out:
634 if (bufp)
635 *bufp = result;
636 return rv;
637 }
638
639 /**
640 * Obtain the next buffer of the input queue of a buffer tree node.
641 *
642 * \param btrn The node whose input queue is to be queried.
643 * \param bufp Result pointer.
644 *
645 * \return The number of bytes that can be read from buf.
646 *
647 * The call of this function is is equivalent to calling \ref
648 * btr_next_buffer_omit() with an \a omit value of zero.
649 */
650 size_t btr_next_buffer(struct btr_node *btrn, char **bufp)
651 {
652 return btr_next_buffer_omit(btrn, 0, bufp);
653 }
654
655 /**
656 * Deallocate the given number of bytes from the input queue.
657 *
658 * \param btrn The buffer tree node.
659 * \param numbytes The number of bytes to be deallocated.
660 *
661 * This function must be used to get rid of existing buffer references in the
662 * node's input queue. If no references to a buffer remain, the underlying
663 * buffers are either freed (in the non-buffer pool case) or the read head of
664 * the buffer pool is being advanced.
665 *
666 * Note that \a numbytes may be smaller than the buffer size. In this case the
667 * buffer is not deallocated and subsequent calls to btr_next_buffer() return
668 * the remaining part of the buffer.
669 */
670 void btr_consume(struct btr_node *btrn, size_t numbytes)
671 {
672 struct btr_buffer_reference *br, *tmp;
673 size_t sz;
674
675 if (numbytes == 0)
676 return;
677 br = get_first_input_br(btrn);
678 assert(br);
679
680 if (br->wrap_count == 0) {
681 /*
682 * No wrap buffer. Drop buffer references whose buffer
683 * has been fully used. */
684 FOR_EACH_BUFFER_REF_SAFE(br, tmp, btrn) {
685 if (br->consumed + numbytes <= br->btrb->size) {
686 br->consumed += numbytes;
687 if (br->consumed == br->btrb->size)
688 btr_drop_buffer_reference(br);
689 return;
690 }
691 numbytes -= br->btrb->size - br->consumed;
692 btr_drop_buffer_reference(br);
693 }
694 assert(false);
695 }
696 /*
697 * We have a wrap buffer, consume from it. If in total, i.e. including
698 * previous calls to brt_consume(), less than wrap_count has been
699 * consumed, there's nothing more we can do.
700 *
701 * Otherwise we drop the wrap buffer and consume from subsequent
702 * buffers of the input queue the correct amount of bytes. This is the
703 * total number of bytes that have been consumed from the wrap buffer.
704 */
705 PARA_DEBUG_LOG("consuming %zu/%zu bytes from wrap buffer\n", numbytes,
706 br_available_bytes(br));
707
708 assert(numbytes <= br_available_bytes(br));
709 if (br->consumed + numbytes < br->wrap_count) {
710 br->consumed += numbytes;
711 return;
712 }
713 PARA_DEBUG_LOG("dropping wrap buffer (%zu bytes)\n", br->btrb->size);
714 /* get rid of the wrap buffer */
715 sz = br->consumed + numbytes;
716 btr_drop_buffer_reference(br);
717 return btr_consume(btrn, sz);
718 }
719
720 /**
721 * Clear the input queue of a buffer tree node.
722 *
723 * \param btrn The node whose input queue should be cleared.
724 */
725 void btr_drain(struct btr_node *btrn)
726 {
727 struct btr_buffer_reference *br, *tmp;
728
729 FOR_EACH_BUFFER_REF_SAFE(br, tmp, btrn)
730 btr_drop_buffer_reference(br);
731 }
732
733 /**
734 * Free all resources allocated by btr_new_node().
735 *
736 * \param btrn Pointer to a btr node obtained by \ref btr_new_node().
737 *
738 * Like free(3), it is OK to call this with a \p NULL pointer argument.
739 */
740 void btr_free_node(struct btr_node *btrn)
741 {
742 if (!btrn)
743 return;
744 free(btrn->name);
745 free(btrn);
746 }
747
748 /**
749 * Remove a node from a buffer tree.
750 *
751 * \param btrn The node to remove.
752 *
753 * This makes all child nodes of \a btrn orphans and removes \a btrn from the
754 * list of children of its parent. Moreover, the input queue of \a btrn is
755 * flushed if it is not empty.
756 *
757 * \sa \ref btr_splice_out_node.
758 */
759 void btr_remove_node(struct btr_node *btrn)
760 {
761 struct btr_node *ch;
762
763 if (!btrn)
764 return;
765 PARA_NOTICE_LOG("removing btr node %s from buffer tree\n", btrn->name);
766 FOR_EACH_CHILD(ch, btrn)
767 ch->parent = NULL;
768 btr_drain(btrn);
769 if (btrn->parent)
770 list_del(&btrn->node);
771 }
772
773 /**
774 * Return the amount of available input bytes of a buffer tree node.
775 *
776 * \param btrn The node whose input size should be computed.
777 *
778 * \return The total number of bytes available in the node's input
779 * queue.
780 *
781 * This simply iterates over all buffer references in the input queue and
782 * returns the sum of the sizes of all references.
783 */
784 size_t btr_get_input_queue_size(struct btr_node *btrn)
785 {
786 struct btr_buffer_reference *br;
787 size_t size = 0, wrap_consumed = 0;
788
789 FOR_EACH_BUFFER_REF(br, btrn) {
790 if (br->wrap_count != 0) {
791 wrap_consumed = br->consumed;
792 continue;
793 }
794 size += br_available_bytes(br);
795 }
796 assert(wrap_consumed <= size);
797 size -= wrap_consumed;
798 return size;
799 }
800
801 /**
802 * Remove a node from the buffer tree, reconnecting parent and children.
803 *
804 * \param btrn The node to splice out.
805 *
806 * This function is used by buffer tree nodes that do not exist during the
807 * whole lifetime of the buffer tree. Unlike btr_remove_node(), calling
808 * btr_splice_out_node() does not split the tree into disconnected components
809 * but reconnects the buffer tree by making all child nodes of \a btrn children
810 * of the parent of \a btrn.
811 */
812 void btr_splice_out_node(struct btr_node *btrn)
813 {
814 struct btr_node *ch, *tmp;
815
816 assert(btrn);
817 PARA_NOTICE_LOG("splicing out %s\n", btrn->name);
818 btr_pushdown(btrn);
819 if (btrn->parent)
820 list_del(&btrn->node);
821 FOR_EACH_CHILD_SAFE(ch, tmp, btrn) {
822 PARA_INFO_LOG("parent(%s): %s\n", ch->name,
823 btrn->parent? btrn->parent->name : "NULL");
824 ch->parent = btrn->parent;
825 if (btrn->parent)
826 list_move(&ch->node, &btrn->parent->children);
827 }
828 assert(list_empty(&btrn->children));
829 }
830
831 /**
832 * Return number of queued output bytes of a buffer tree node.
833 *
834 * \param btrn The node whose output queue size should be computed.
835 *
836 * \return This function iterates over all children of the given node and
837 * returns the size of the largest input queue.
838 */
839 size_t btr_get_output_queue_size(struct btr_node *btrn)
840 {
841 size_t max_size = 0;
842 struct btr_node *ch;
843
844 FOR_EACH_CHILD(ch, btrn) {
845 size_t size = btr_get_input_queue_size(ch);
846 max_size = PARA_MAX(max_size, size);
847 }
848 return max_size;
849 }
850
851 /**
852 * Execute a inter-node command on a parent node.
853 *
854 * \param btrn The node to start looking.
855 * \param command The command to execute.
856 * \param value_result Additional arguments and result value.
857 *
858 * This function traverses the buffer tree upwards and looks for parent nodes
859 * of \a btrn that understands \a command. On the first such node the command
860 * is executed, and the result is stored in \a value_result.
861 *
862 * \return \p -ENOTSUP if no parent node of \a btrn understands \a command.
863 * Otherwise the return value of the command handler is returned.
864 */
865 int btr_exec_up(struct btr_node *btrn, const char *command, char **value_result)
866 {
867 int ret;
868
869 for (; btrn; btrn = btrn->parent) {
870 struct btr_node *parent = btrn->parent;
871 if (!parent)
872 return -ERRNO_TO_PARA_ERROR(ENOTSUP);
873 if (!parent->execute)
874 continue;
875 PARA_INFO_LOG("parent: %s, cmd: %s\n", parent->name, command);
876 ret = parent->execute(parent, command, value_result);
877 if (ret == -ERRNO_TO_PARA_ERROR(ENOTSUP))
878 continue;
879 if (ret < 0)
880 return ret;
881 if (value_result && *value_result)
882 PARA_NOTICE_LOG("%s(%s): %s\n", command, parent->name,
883 *value_result);
884 return 1;
885 }
886 return -ERRNO_TO_PARA_ERROR(ENOTSUP);
887 }
888
889 /**
890 * Obtain the context of a buffer node tree.
891 *
892 * \param btrn The node whose output queue size should be computed.
893 *
894 * \return A pointer to the \a context address specified at node creation time.
895 *
896 * \sa btr_new_node(), struct \ref btr_node_description.
897 */
898 void *btr_context(struct btr_node *btrn)
899 {
900 return btrn->context;
901 }
902
903 static bool need_buffer_pool_merge(struct btr_node *btrn)
904 {
905 struct btr_buffer_reference *br = get_first_input_br(btrn);
906
907 if (!br)
908 return false;
909 if (br->wrap_count != 0)
910 return true;
911 if (br->btrb->pool)
912 return true;
913 return false;
914 }
915
916 static void merge_input_pool(struct btr_node *btrn, size_t dest_size)
917 {
918 struct btr_buffer_reference *br, *wbr = NULL;
919 int num_refs; /* including wrap buffer */
920 char *buf, *buf1 = NULL, *buf2 = NULL;
921 size_t sz, sz1 = 0, sz2 = 0, wb_consumed = 0;
922
923 br = get_first_input_br(btrn);
924 if (!br || br_available_bytes(br) >= dest_size)
925 return;
926 num_refs = 0;
927 FOR_EACH_BUFFER_REF(br, btrn) {
928 num_refs++;
929 sz = btr_get_buffer_by_reference(br, &buf);
930 if (sz == 0)
931 break;
932 if (br->wrap_count != 0) {
933 assert(!wbr);
934 assert(num_refs == 1);
935 wbr = br;
936 if (sz >= dest_size)
937 return;
938 wb_consumed = br->consumed;
939 continue;
940 }
941 if (!buf1) {
942 buf1 = buf;
943 sz1 = sz;
944 goto next;
945 }
946 if (buf1 + sz1 == buf) {
947 sz1 += sz;
948 goto next;
949 }
950 if (!buf2) {
951 buf2 = buf;
952 sz2 = sz;
953 goto next;
954 }
955 assert(buf2 + sz2 == buf);
956 sz2 += sz;
957 next:
958 if (sz1 + sz2 >= dest_size + wb_consumed)
959 break;
960 }
961 if (!buf2) /* nothing to do */
962 return;
963 assert(buf1 && sz2 > 0);
964 /*
965 * If the second buffer is large, we only take the first part of it to
966 * avoid having to memcpy() huge buffers.
967 */
968 sz2 = PARA_MIN(sz2, (size_t)(64 * 1024));
969 if (!wbr) {
970 /* Make a new wrap buffer combining buf1 and buf2. */
971 sz = sz1 + sz2;
972 buf = para_malloc(sz);
973 PARA_DEBUG_LOG("merging input buffers: (%p:%zu, %p:%zu) -> %p:%zu\n",
974 buf1, sz1, buf2, sz2, buf, sz);
975 memcpy(buf, buf1, sz1);
976 memcpy(buf + sz1, buf2, sz2);
977 br = para_calloc(sizeof(*br));
978 br->btrb = new_btrb(buf, sz);
979 br->btrb->refcount = 1;
980 br->consumed = 0;
981 /* This is a wrap buffer */
982 br->wrap_count = sz1;
983 para_list_add(&br->node, &btrn->input_queue);
984 return;
985 }
986 /*
987 * We already have a wrap buffer, but it is too small. It might be
988 * partially used.
989 */
990 if (wbr->wrap_count == sz1 && wbr->btrb->size >= sz1 + sz2) /* nothing we can do about it */
991 return;
992 sz = sz1 + sz2 - wbr->btrb->size; /* amount of new data */
993 PARA_DEBUG_LOG("increasing wrap buffer %zu -> %zu\n", wbr->btrb->size,
994 wbr->btrb->size + sz);
995 wbr->btrb->size += sz;
996 wbr->btrb->buf = para_realloc(wbr->btrb->buf, wbr->btrb->size);
997 /* copy the new data to the end of the reallocated buffer */
998 assert(sz2 >= sz);
999 memcpy(wbr->btrb->buf + wbr->btrb->size - sz, buf2 + sz2 - sz, sz);
1000 }
1001
1002 /**
1003 * Merge the first two input buffers into one.
1004 *
1005 * This is a quite expensive operation.
1006 *
1007 * \return The number of buffers that have been available (zero, one or two).
1008 */
1009 static int merge_input(struct btr_node *btrn)
1010 {
1011 struct btr_buffer_reference *brs[2], *br;
1012 char *bufs[2], *buf;
1013 size_t szs[2], sz;
1014 int i;
1015
1016 if (list_empty(&btrn->input_queue))
1017 return 0;
1018 if (list_is_singular(&btrn->input_queue))
1019 return 1;
1020 i = 0;
1021 /* get references to the first two buffers */
1022 FOR_EACH_BUFFER_REF(br, btrn) {
1023 brs[i] = br;
1024 szs[i] = btr_get_buffer_by_reference(brs[i], bufs + i);
1025 i++;
1026 if (i == 2)
1027 break;
1028 }
1029 assert(i == 2);
1030 /* make a new btrb that combines the two buffers and a br to it. */
1031 sz = szs[0] + szs[1];
1032 buf = para_malloc(sz);
1033 PARA_DEBUG_LOG("%s: memory merging input buffers: (%zu, %zu) -> %zu\n",
1034 btrn->name, szs[0], szs[1], sz);
1035 memcpy(buf, bufs[0], szs[0]);
1036 memcpy(buf + szs[0], bufs[1], szs[1]);
1037
1038 br = para_calloc(sizeof(*br));
1039 br->btrb = new_btrb(buf, sz);
1040 br->btrb->refcount = 1;
1041
1042 /* replace the first two refs by the new one */
1043 btr_drop_buffer_reference(brs[0]);
1044 btr_drop_buffer_reference(brs[1]);
1045 para_list_add(&br->node, &btrn->input_queue);
1046 return 2;
1047 }
1048
1049 /**
1050 * Combine input queue buffers.
1051 *
1052 * \param btrn The buffer tree node whose input should be merged.
1053 * \param dest_size Stop merging if a buffer of at least this size exists.
1054 *
1055 * Used to combine as many buffers as needed into a single buffer whose size is
1056 * at least \a dest_size. This function is rather cheap in case the parent node
1057 * uses buffer pools and rather expensive otherwise.
1058 *
1059 * Note that if less than \a dest_size bytes are available in total, this
1060 * function does nothing and subsequent calls to btr_next_buffer() will still
1061 * return a buffer size less than \a dest_size.
1062 */
1063 void btr_merge(struct btr_node *btrn, size_t dest_size)
1064 {
1065 if (need_buffer_pool_merge(btrn))
1066 return merge_input_pool(btrn, dest_size);
1067 for (;;) {
1068 char *buf;
1069 size_t len = btr_next_buffer(btrn, &buf);
1070 if (len >= dest_size)
1071 return;
1072 PARA_DEBUG_LOG("input size = %zu < %zu = dest\n", len, dest_size);
1073 if (merge_input(btrn) < 2)
1074 return;
1075 }
1076 }
1077
1078 static bool btr_eof(struct btr_node *btrn)
1079 {
1080 char *buf;
1081 size_t len = btr_next_buffer(btrn, &buf);
1082
1083 return (len == 0 && btr_no_parent(btrn));
1084 }
1085
1086 static void log_tree_recursively(struct btr_node *btrn, int loglevel, int depth)
1087 {
1088 struct btr_node *ch;
1089 const char spaces[] = " ", *space = spaces + 16 - depth;
1090
1091 if (depth > 16)
1092 return;
1093 para_log(loglevel, "%s%s\n", space, btrn->name);
1094 FOR_EACH_CHILD(ch, btrn)
1095 log_tree_recursively(ch, loglevel, depth + 1);
1096 }
1097
1098 /**
1099 * Write the current buffer (sub-)tree to the log.
1100 *
1101 * \param btrn Start logging at this node.
1102 * \param loglevel Set severity with which the tree should be logged.
1103 */
1104 void btr_log_tree(struct btr_node *btrn, int loglevel)
1105 {
1106 return log_tree_recursively(btrn, loglevel, 0);
1107 }
1108
1109 /**
1110 * Find the node with the given name in the buffer tree.
1111 *
1112 * \param name The name of the node to search.
1113 * \param root Where to start the search.
1114 *
1115 * \return A pointer to the node with the given name on success. If \a name is
1116 * \p NULL, the function returns \a root. If there is no node with the given
1117 * name, \p NULL is returned.
1118 */
1119 struct btr_node *btr_search_node(const char *name, struct btr_node *root)
1120 {
1121 struct btr_node *ch;
1122
1123 if (!name)
1124 return root;
1125 if (!strcmp(root->name, name))
1126 return root;
1127 FOR_EACH_CHILD(ch, root) {
1128 struct btr_node *result = btr_search_node(name, ch);
1129 if (result)
1130 return result;
1131 }
1132 return NULL;
1133 }
1134
1135 /** 640K ought to be enough for everybody ;) */
1136 #define BTRN_MAX_PENDING (96 * 1024)
1137
1138 /**
1139 * Return the current state of a buffer tree node.
1140 *
1141 * \param btrn The node whose state should be queried.
1142 * \param min_iqs The minimal input queue size.
1143 * \param type The supposed type of \a btrn.
1144 *
1145 * Most users of the buffer tree subsystem call this function from both
1146 * their pre_select and the post_select methods.
1147 *
1148 * \return Negative if an error condition was detected, zero if there
1149 * is nothing to do and positive otherwise.
1150 *
1151 * Examples:
1152 *
1153 * - If a non-root node has no parent and an empty input queue, the function
1154 * returns \p -E_BTR_EOF. Similarly, if a non-leaf node has no children, \p
1155 * -E_BTR_NO_CHILD is returned.
1156 *
1157 * - If less than \a min_iqs many bytes are available in the input queue and no
1158 * EOF condition was detected, the function returns zero.
1159 *
1160 * - If there's plenty of data left in the input queue of the children of \a
1161 * btrn, the function also returns zero in order to bound the memory usage of
1162 * the buffer tree.
1163 */
1164 int btr_node_status(struct btr_node *btrn, size_t min_iqs,
1165 enum btr_node_type type)
1166 {
1167 size_t iqs;
1168
1169 assert(btrn);
1170 if (type != BTR_NT_LEAF) {
1171 if (btr_no_children(btrn))
1172 return -E_BTR_NO_CHILD;
1173 if (btr_get_output_queue_size(btrn) > BTRN_MAX_PENDING)
1174 return 0;
1175 }
1176 if (type != BTR_NT_ROOT) {
1177 if (btr_eof(btrn))
1178 return -E_BTR_EOF;
1179 iqs = btr_get_input_queue_size(btrn);
1180 if (iqs == 0) /* we have a parent, because not eof */
1181 return 0;
1182 if (iqs < min_iqs && !btr_no_parent(btrn))
1183 return 0;
1184 }
1185 return 1;
1186 }
1187
1188 /**
1189 * Get the time of the first I/O for a buffer tree node.
1190 *
1191 * \param btrn The node whose I/O time should be obtained.
1192 * \param tv Result pointer.
1193 *
1194 * Mainly useful for the time display of para_audiod.
1195 */
1196 void btr_get_node_start(struct btr_node *btrn, struct timeval *tv)
1197 {
1198 *tv = btrn->start;
1199 }