Merge branch 't/doc'
[paraslash.git] / buffer_tree.c
1 /*
2 * Copyright (C) 2009-2012 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
10 #include "para.h"
11 #include "list.h"
12 #include "string.h"
13 #include "buffer_tree.h"
14 #include "error.h"
15 #include "sched.h"
16
17 /* whead = NULL means area full */
18 struct btr_pool {
19 char *name;
20 char *area_start;
21 char *area_end;
22 char *rhead;
23 char *whead;
24 };
25
26 struct btr_buffer {
27 char *buf;
28 size_t size;
29 /** The number of references to this buffer. */
30 int refcount;
31 /* NULL means no buffer pool but a malloced buffer. */
32 struct btr_pool *pool;
33 };
34
35 struct btr_buffer_reference {
36 struct btr_buffer *btrb;
37 size_t consumed;
38 /* Each buffer reference belongs to the buffer queue list of some buffer tree node. */
39 struct list_head node;
40 size_t wrap_count;
41 };
42
43 struct btr_node {
44 char *name;
45 struct btr_node *parent;
46 /* The position of this btr node in the buffer tree. */
47 struct list_head node;
48 /* The children nodes of this btr node are linked together in a list. */
49 struct list_head children;
50 /* Time of first data transfer. */
51 struct timeval start;
52 /**
53 * The input queue is a list of references to btr buffers. Each item on
54 * the list represents an input buffer which has not been completely
55 * used by this btr node.
56 */
57 struct list_head input_queue;
58 btr_command_handler execute;
59 void *context;
60 };
61
62 /**
63 * Create a new buffer pool.
64 *
65 * \param name The name of the new buffer pool.
66 * \param area_size The size in bytes of the pool area.
67 *
68 * \return An opaque pointer to the newly created buffer pool. It must be
69 * passed to btr_pool_free() after it is no longer used to deallocate all
70 * resources.
71 */
72 struct btr_pool *btr_pool_new(const char *name, size_t area_size)
73 {
74 struct btr_pool *btrp;
75
76 PARA_INFO_LOG("%s, %zu bytes\n", name, area_size);
77 btrp = para_malloc(sizeof(*btrp));
78 btrp->area_start = para_malloc(area_size);
79 btrp->area_end = btrp->area_start + area_size;
80 btrp->rhead = btrp->area_start;
81 btrp->whead = btrp->area_start;
82 btrp->name = para_strdup(name);
83 return btrp;
84 }
85
86 /**
87 * Deallocate resources used by a buffer pool.
88 *
89 * \param btrp A pointer obtained via btr_pool_new().
90 */
91 void btr_pool_free(struct btr_pool *btrp)
92 {
93 if (!btrp)
94 return;
95 free(btrp->area_start);
96 free(btrp->name);
97 free(btrp);
98 }
99
100 /**
101 * Return the size of the buffer pool area.
102 *
103 * \param btrp The buffer pool.
104 *
105 * \return The same value which was passed during creation time to
106 * btr_pool_new().
107 */
108 size_t btr_pool_size(struct btr_pool *btrp)
109 {
110 return btrp->area_end - btrp->area_start;
111 }
112
113 static size_t btr_pool_filled(struct btr_pool *btrp)
114 {
115 if (!btrp->whead)
116 return btr_pool_size(btrp);
117 if (btrp->rhead <= btrp->whead)
118 return btrp->whead - btrp->rhead;
119 return btr_pool_size(btrp) - (btrp->rhead - btrp->whead);
120 }
121
122 /**
123 * Get the number of unused bytes in the buffer pool.
124 *
125 * \param btrp The pool.
126 *
127 * \return The number of bytes that can currently be allocated.
128 *
129 * Note that in general the returned number of bytes is not available as a
130 * single contiguous buffer. Use btr_pool_available() to obtain the length of
131 * the largest contiguous buffer that can currently be allocated from the
132 * buffer pool.
133 */
134 size_t btr_pool_unused(struct btr_pool *btrp)
135 {
136 return btr_pool_size(btrp) - btr_pool_filled(btrp);
137 }
138
139 /*
140 * Return maximal size available for one read. This is
141 * smaller than the value returned by btr_pool_unused().
142 */
143 static size_t btr_pool_available(struct btr_pool *btrp)
144 {
145 if (!btrp->whead)
146 return 0;
147 if (btrp->rhead <= btrp->whead)
148 return btrp->area_end - btrp->whead;
149 return btrp->rhead - btrp->whead;
150 }
151
152 /**
153 * Obtain the current write head.
154 *
155 * \param btrp The buffer pool.
156 * \param result The write head is returned here.
157 *
158 * \return The maximal amount of bytes that may be written to the returned
159 * buffer.
160 */
161 size_t btr_pool_get_buffer(struct btr_pool *btrp, char **result)
162 {
163 if (result)
164 *result = btrp->whead;
165 return btr_pool_available(btrp);
166 }
167
168 /**
169 * Get references to buffers pointing to free space of the buffer pool area.
170 *
171 * \param btrp The buffer pool.
172 * \param iov The scatter array.
173 *
174 * \return Zero if the buffer pool is full, one if the free space of the buffer
175 * pool area is available as a single contiguous buffer, two if the free space
176 * consists of two buffers. If this function returns the value n, then n
177 * elements of \a iov are initialized.
178 */
179 int btr_pool_get_buffers(struct btr_pool *btrp, struct iovec iov[2])
180 {
181 size_t sz, unused;
182 char *buf;
183
184 sz = btr_pool_get_buffer(btrp, &buf);
185 if (sz == 0)
186 return 0;
187 iov[0].iov_len = sz;
188 iov[0].iov_base = buf;
189 unused = btr_pool_unused(btrp);
190 if (sz == unused)
191 return 1;
192 iov[1].iov_len = unused - sz;
193 iov[1].iov_base = btrp->area_start;
194 return 2;
195 }
196
197 /**
198 * Mark a part of the buffer pool area as allocated.
199 *
200 * \param btrp The buffer pool.
201 * \param size The amount of bytes to be allocated.
202 *
203 * This is usually called after the caller wrote to the buffer obtained by
204 * btr_pool_get_buffer().
205 */
206 static void btr_pool_allocate(struct btr_pool *btrp, size_t size)
207 {
208 char *end;
209
210 if (size == 0)
211 return;
212 assert(size <= btr_pool_available(btrp));
213 end = btrp->whead + size;
214 assert(end <= btrp->area_end);
215
216 if (end == btrp->area_end) {
217 PARA_DEBUG_LOG("%s: end of pool area reached\n", btrp->name);
218 end = btrp->area_start;
219 }
220 if (end == btrp->rhead) {
221 PARA_DEBUG_LOG("%s btrp buffer full\n", btrp->name);
222 end = NULL; /* buffer full */
223 }
224 btrp->whead = end;
225 }
226
227 static void btr_pool_deallocate(struct btr_pool *btrp, size_t size)
228 {
229 char *end = btrp->rhead + size;
230
231 if (size == 0)
232 return;
233 assert(end <= btrp->area_end);
234 assert(size <= btr_pool_filled(btrp));
235 if (end == btrp->area_end)
236 end = btrp->area_start;
237 if (!btrp->whead)
238 btrp->whead = btrp->rhead;
239 btrp->rhead = end;
240 if (btrp->rhead == btrp->whead)
241 btrp->rhead = btrp->whead = btrp->area_start;
242 }
243
244 #define FOR_EACH_CHILD(_tn, _btrn) list_for_each_entry((_tn), \
245 &((_btrn)->children), node)
246 #define FOR_EACH_CHILD_SAFE(_tn, _tmp, _btrn) \
247 list_for_each_entry_safe((_tn), (_tmp), &((_btrn)->children), node)
248
249 #define FOR_EACH_BUFFER_REF(_br, _btrn) \
250 list_for_each_entry((_br), &(_btrn)->input_queue, node)
251 #define FOR_EACH_BUFFER_REF_SAFE(_br, _tmp, _btrn) \
252 list_for_each_entry_safe((_br), (_tmp), &(_btrn)->input_queue, node)
253
254 /**
255 * Create a new buffer tree node.
256 *
257 * \param bnd Specifies how to create the new node.
258 *
259 * \return A pointer to the newly allocated node.
260 *
261 * This function always succeeds (or calls exit()). The returned pointer must
262 * be freed using btr_free_node() after the node has been removed from the
263 * buffer tree via btr_remove_node().
264 */
265 struct btr_node *btr_new_node(struct btr_node_description *bnd)
266 {
267 struct btr_node *btrn = para_malloc(sizeof(*btrn));
268
269 btrn->name = para_strdup(bnd->name);
270 btrn->parent = bnd->parent;
271 btrn->execute = bnd->handler;
272 btrn->context = bnd->context;
273 btrn->start.tv_sec = 0;
274 btrn->start.tv_usec = 0;
275 INIT_LIST_HEAD(&btrn->children);
276 INIT_LIST_HEAD(&btrn->input_queue);
277 if (!bnd->child) {
278 if (bnd->parent) {
279 list_add_tail(&btrn->node, &bnd->parent->children);
280 PARA_INFO_LOG("new leaf node: %s (child of %s)\n",
281 bnd->name, bnd->parent->name);
282 } else
283 PARA_INFO_LOG("added %s as btr root\n", bnd->name);
284 goto out;
285 }
286 if (!bnd->parent) {
287 assert(!bnd->child->parent);
288 PARA_INFO_LOG("new root: %s (was %s)\n",
289 bnd->name, bnd->child->name);
290 btrn->parent = NULL;
291 list_add_tail(&bnd->child->node, &btrn->children);
292 /* link it in */
293 bnd->child->parent = btrn;
294 goto out;
295 }
296 PARA_EMERG_LOG("inserting internal nodes not yet supported.\n");
297 exit(EXIT_FAILURE);
298 assert(bnd->child->parent == bnd->parent);
299 out:
300 return btrn;
301 }
302
303 /*
304 * Allocate a new btr buffer.
305 *
306 * The freshly allocated buffer will have a zero refcount and will
307 * not be associated with a btr pool.
308 */
309 static struct btr_buffer *new_btrb(char *buf, size_t size)
310 {
311 struct btr_buffer *btrb = para_calloc(sizeof(*btrb));
312
313 btrb->buf = buf;
314 btrb->size = size;
315 return btrb;
316 }
317
318 static void dealloc_buffer(struct btr_buffer *btrb)
319 {
320 if (btrb->pool)
321 btr_pool_deallocate(btrb->pool, btrb->size);
322 else
323 free(btrb->buf);
324 }
325
326 static struct btr_buffer_reference *get_first_input_br(struct btr_node *btrn)
327 {
328 if (list_empty(&btrn->input_queue))
329 return NULL;
330 return list_first_entry(&btrn->input_queue,
331 struct btr_buffer_reference, node);
332 }
333
334 /*
335 * Deallocate the reference, release the resources if refcount drops to zero.
336 */
337 static void btr_drop_buffer_reference(struct btr_buffer_reference *br)
338 {
339 struct btr_buffer *btrb = br->btrb;
340
341 list_del(&br->node);
342 free(br);
343 btrb->refcount--;
344 if (btrb->refcount == 0) {
345 dealloc_buffer(btrb);
346 free(btrb);
347 }
348 }
349
350 static void add_btrb_to_children(struct btr_buffer *btrb,
351 struct btr_node *btrn, size_t consumed)
352 {
353 struct btr_node *ch;
354
355 if (btrn->start.tv_sec == 0)
356 btrn->start = *now;
357 FOR_EACH_CHILD(ch, btrn) {
358 struct btr_buffer_reference *br = para_calloc(sizeof(*br));
359 br->btrb = btrb;
360 br->consumed = consumed;
361 list_add_tail(&br->node, &ch->input_queue);
362 btrb->refcount++;
363 if (ch->start.tv_sec == 0)
364 ch->start = *now;
365 }
366 }
367
368 /**
369 * Insert a malloced buffer into the buffer tree.
370 *
371 * \param buf The buffer to insert.
372 * \param size The size of \a buf in bytes.
373 * \param btrn Position in the buffer tree to create the output.
374 *
375 * This creates references to \a buf and adds these references to each child of
376 * \a btrn. The buffer will be freed using standard free() once no buffer tree
377 * node is referencing it any more.
378 *
379 * Note that this function must not be used if \a buf was obtained from a
380 * buffer pool. Use btr_add_output_pool() in this case.
381 */
382 void btr_add_output(char *buf, size_t size, struct btr_node *btrn)
383 {
384 struct btr_buffer *btrb;
385
386 assert(size != 0);
387 if (list_empty(&btrn->children)) {
388 free(buf);
389 return;
390 }
391 btrb = new_btrb(buf, size);
392 add_btrb_to_children(btrb, btrn, 0);
393 }
394
395 /**
396 * Feed data to child nodes of a buffer tree node.
397 *
398 * \param btrp The buffer pool.
399 * \param size The number of bytes to be allocated and fed to each child.
400 * \param btrn The node whose children are to be fed.
401 *
402 * This function allocates the amount of bytes from the buffer pool area,
403 * starting at the current value of the write head, and creates buffer
404 * references to the resulting part of the buffer pool area, one for each child
405 * of \a btrn. The references are then fed into the input queue of each child.
406 */
407 void btr_add_output_pool(struct btr_pool *btrp, size_t size,
408 struct btr_node *btrn)
409 {
410 struct btr_buffer *btrb;
411 char *buf;
412 size_t avail;
413
414 assert(size != 0);
415 if (list_empty(&btrn->children))
416 return;
417 avail = btr_pool_get_buffer(btrp, &buf);
418 assert(avail >= size);
419 btr_pool_allocate(btrp, size);
420 btrb = new_btrb(buf, size);
421 btrb->pool = btrp;
422 add_btrb_to_children(btrb, btrn, 0);
423 }
424
425 /**
426 * Copy data to write head of a buffer pool and feed it to all children nodes.
427 *
428 * \param src The source buffer.
429 * \param n The size of the source buffer in bytes.
430 * \param btrp The destination buffer pool.
431 * \param btrn Add the data as output of this node.
432 *
433 * This is expensive. The caller must make sure the data fits into the buffer
434 * pool area.
435 */
436 void btr_copy(const void *src, size_t n, struct btr_pool *btrp,
437 struct btr_node *btrn)
438 {
439 char *buf;
440 size_t sz, copy;
441
442 if (n == 0)
443 return;
444 assert(n <= btr_pool_unused(btrp));
445 sz = btr_pool_get_buffer(btrp, &buf);
446 copy = PARA_MIN(sz, n);
447 memcpy(buf, src, copy);
448 btr_add_output_pool(btrp, copy, btrn);
449 if (copy == n)
450 return;
451 sz = btr_pool_get_buffer(btrp, &buf);
452 assert(sz >= n - copy);
453 memcpy(buf, src + copy, n - copy);
454 btr_add_output_pool(btrp, n - copy, btrn);
455 }
456
457 static void btr_pushdown_br(struct btr_buffer_reference *br, struct btr_node *btrn)
458 {
459 add_btrb_to_children(br->btrb, btrn, br->consumed);
460 btr_drop_buffer_reference(br);
461 }
462
463 /**
464 * Feed all buffer references of the input queue through the output channel.
465 *
466 * \param btrn The node whose buffer references should be pushed down.
467 *
468 * This function is useful for filters that do not change the contents of the
469 * buffers at all, like the wav filter or the amp filter if no amplification
470 * was specified. This function is rather cheap.
471 *
472 * \sa \ref btr_pushdown_one().
473 */
474 void btr_pushdown(struct btr_node *btrn)
475 {
476 struct btr_buffer_reference *br, *tmp;
477
478 FOR_EACH_BUFFER_REF_SAFE(br, tmp, btrn)
479 btr_pushdown_br(br, btrn);
480 }
481
482 /**
483 * Feed the next buffer of the input queue through the output channel.
484 *
485 * \param btrn The node whose first input queue buffer should be pushed down.
486 *
487 * This works like \ref btr_pushdown() but pushes down only one buffer
488 * reference.
489 */
490 void btr_pushdown_one(struct btr_node *btrn)
491 {
492 struct btr_buffer_reference *br;
493
494 if (list_empty(&btrn->input_queue))
495 return;
496 br = list_first_entry(&btrn->input_queue, struct btr_buffer_reference, node);
497 btr_pushdown_br(br, btrn);
498 }
499
500 /*
501 * Find out whether a node is a leaf node.
502 *
503 * \param btrn The node to check.
504 *
505 * \return True if this node has no children. False otherwise.
506 */
507 static bool btr_no_children(struct btr_node *btrn)
508 {
509 return list_empty(&btrn->children);
510 }
511
512 /**
513 * Find out whether a node is an orphan node.
514 *
515 * \param btrn The buffer tree node.
516 *
517 * \return True if \a btrn has no parent.
518 *
519 * This function will always return true for the root node. However in case
520 * nodes have been removed from the tree, other nodes may become orphans too.
521 */
522 bool btr_no_parent(struct btr_node *btrn)
523 {
524 return !btrn->parent;
525 }
526
527 /**
528 * Find out whether it is OK to change an input buffer.
529 *
530 * \param btrn The buffer tree node to check.
531 *
532 * This is used by filters that produce exactly the same amount of output as
533 * there is input. The amp filter which multiplies each sample by some number
534 * is an example of such a filter. If there are no other nodes in the buffer
535 * tree that read the same input stream (i.e. if \a btrn has no siblings), a
536 * node may modify its input buffer directly and push down the modified buffer
537 * to its children, thereby avoiding to allocate a possibly large additional
538 * buffer.
539 *
540 * Since the buffer tree may change at any time, this function should be called
541 * during each post_select call.
542 *
543 * \return True if \a btrn has no siblings.
544 */
545 bool btr_inplace_ok(struct btr_node *btrn)
546 {
547 if (!btrn->parent)
548 return true;
549 return list_is_singular(&btrn->parent->children);
550 }
551
552 static inline size_t br_available_bytes(struct btr_buffer_reference *br)
553 {
554 return br->btrb->size - br->consumed;
555 }
556
557 static size_t btr_get_buffer_by_reference(struct btr_buffer_reference *br, char **buf)
558 {
559 if (buf)
560 *buf = br->btrb->buf + br->consumed;
561 return br_available_bytes(br);
562 }
563
564 /**
565 * Obtain the next buffer of the input queue, omitting data.
566 *
567 * \param btrn The node whose input queue is to be queried.
568 * \param omit Number of bytes to be omitted.
569 * \param bufp Result pointer.
570 *
571 * If a buffer tree node needs more input data but can not consume the data it
572 * already has (because it might be needed again later) this function can be
573 * used instead of btr_next_buffer() to get a reference to the buffer obtained
574 * by skipping the given number of bytes. Skipped input bytes are not consumed.
575 *
576 * With a zero \a omit argument, this function is equivalent to \ref
577 * btr_next_buffer().
578 *
579 * \return Number of bytes in \a bufp. If there are less than or equal to \a
580 * omit many bytes available in the input queue of the buffer tree node pointed
581 * to by \a btrn, the function returns zero and the value of \a bufp is
582 * undefined.
583 */
584 size_t btr_next_buffer_omit(struct btr_node *btrn, size_t omit, char **bufp)
585 {
586 struct btr_buffer_reference *br;
587 size_t wrap_count, sz, rv = 0;
588 char *buf, *result = NULL;
589
590 br = get_first_input_br(btrn);
591 if (!br)
592 return 0;
593 wrap_count = br->wrap_count;
594 if (wrap_count > 0) { /* we have a wrap buffer */
595 sz = btr_get_buffer_by_reference(br, &buf);
596 if (sz > omit) { /* and it's big enough */
597 result = buf + omit;
598 rv = sz - omit;
599 /*
600 * Wrap buffers are allocated by malloc(), so the next
601 * buffer ref will not align nicely, so we return the
602 * tail of the wrap buffer.
603 */
604 goto out;
605 }
606 /*
607 * The next wrap_count bytes exist twice, in the wrap buffer
608 * and as a buffer reference in the buffer tree pool.
609 */
610 omit += wrap_count;
611 }
612 /*
613 * For buffer tree pools, the buffers in the list align, i.e. the next
614 * buffer in the list starts directly at the end of its predecessor. In
615 * this case we merge adjacent buffers and return one larger buffer
616 * instead.
617 */
618 FOR_EACH_BUFFER_REF(br, btrn) {
619 sz = btr_get_buffer_by_reference(br, &buf);
620 if (result) {
621 if (result + rv != buf)
622 goto out;
623 rv += sz;
624 } else if (sz > omit) {
625 result = buf + omit;
626 rv = sz - omit;
627 } else
628 omit -= sz;
629 }
630 if (!result)
631 return 0;
632 out:
633 if (bufp)
634 *bufp = result;
635 return rv;
636 }
637
638 /**
639 * Obtain the next buffer of the input queue of a buffer tree node.
640 *
641 * \param btrn The node whose input queue is to be queried.
642 * \param bufp Result pointer.
643 *
644 * \return The number of bytes that can be read from buf.
645 *
646 * The call of this function is is equivalent to calling \ref
647 * btr_next_buffer_omit() with an \a omit value of zero.
648 */
649 size_t btr_next_buffer(struct btr_node *btrn, char **bufp)
650 {
651 return btr_next_buffer_omit(btrn, 0, bufp);
652 }
653
654 /**
655 * Deallocate the given number of bytes from the input queue.
656 *
657 * \param btrn The buffer tree node.
658 * \param numbytes The number of bytes to be deallocated.
659 *
660 * This function must be used to get rid of existing buffer references in the
661 * node's input queue. If no references to a buffer remain, the underlying
662 * buffers are either freed (in the non-buffer pool case) or the read head of
663 * the buffer pool is being advanced.
664 *
665 * Note that \a numbytes may be smaller than the buffer size. In this case the
666 * buffer is not deallocated and subsequent calls to btr_next_buffer() return
667 * the remaining part of the buffer.
668 */
669 void btr_consume(struct btr_node *btrn, size_t numbytes)
670 {
671 struct btr_buffer_reference *br, *tmp;
672 size_t sz;
673
674 if (numbytes == 0)
675 return;
676 br = get_first_input_br(btrn);
677 assert(br);
678
679 if (br->wrap_count == 0) {
680 /*
681 * No wrap buffer. Drop buffer references whose buffer
682 * has been fully used. */
683 FOR_EACH_BUFFER_REF_SAFE(br, tmp, btrn) {
684 if (br->consumed + numbytes <= br->btrb->size) {
685 br->consumed += numbytes;
686 if (br->consumed == br->btrb->size)
687 btr_drop_buffer_reference(br);
688 return;
689 }
690 numbytes -= br->btrb->size - br->consumed;
691 btr_drop_buffer_reference(br);
692 }
693 assert(false);
694 }
695 /*
696 * We have a wrap buffer, consume from it. If in total, i.e. including
697 * previous calls to brt_consume(), less than wrap_count has been
698 * consumed, there's nothing more we can do.
699 *
700 * Otherwise we drop the wrap buffer and consume from subsequent
701 * buffers of the input queue the correct amount of bytes. This is the
702 * total number of bytes that have been consumed from the wrap buffer.
703 */
704 PARA_DEBUG_LOG("consuming %zu/%zu bytes from wrap buffer\n", numbytes,
705 br_available_bytes(br));
706
707 assert(numbytes <= br_available_bytes(br));
708 if (br->consumed + numbytes < br->wrap_count) {
709 br->consumed += numbytes;
710 return;
711 }
712 PARA_DEBUG_LOG("dropping wrap buffer (%zu bytes)\n", br->btrb->size);
713 /* get rid of the wrap buffer */
714 sz = br->consumed + numbytes;
715 btr_drop_buffer_reference(br);
716 return btr_consume(btrn, sz);
717 }
718
719 /**
720 * Clear the input queue of a buffer tree node.
721 *
722 * \param btrn The node whose input queue should be cleared.
723 */
724 void btr_drain(struct btr_node *btrn)
725 {
726 struct btr_buffer_reference *br, *tmp;
727
728 FOR_EACH_BUFFER_REF_SAFE(br, tmp, btrn)
729 btr_drop_buffer_reference(br);
730 }
731
732 /**
733 * Free all resources allocated by btr_new_node().
734 *
735 * \param btrn Pointer to a btr node obtained by \ref btr_new_node().
736 *
737 * Like free(3), it is OK to call this with a \p NULL pointer argument.
738 */
739 void btr_free_node(struct btr_node *btrn)
740 {
741 if (!btrn)
742 return;
743 free(btrn->name);
744 free(btrn);
745 }
746
747 /**
748 * Remove a node from a buffer tree.
749 *
750 * \param btrn The node to remove.
751 *
752 * This makes all child nodes of \a btrn orphans and removes \a btrn from the
753 * list of children of its parent. Moreover, the input queue of \a btrn is
754 * flushed if it is not empty.
755 *
756 * \sa \ref btr_splice_out_node.
757 */
758 void btr_remove_node(struct btr_node *btrn)
759 {
760 struct btr_node *ch;
761
762 if (!btrn)
763 return;
764 PARA_INFO_LOG("removing btr node %s from buffer tree\n", btrn->name);
765 FOR_EACH_CHILD(ch, btrn)
766 ch->parent = NULL;
767 btr_drain(btrn);
768 if (btrn->parent)
769 list_del(&btrn->node);
770 }
771
772 /**
773 * Return the amount of available input bytes of a buffer tree node.
774 *
775 * \param btrn The node whose input size should be computed.
776 *
777 * \return The total number of bytes available in the node's input
778 * queue.
779 *
780 * This simply iterates over all buffer references in the input queue and
781 * returns the sum of the sizes of all references.
782 */
783 size_t btr_get_input_queue_size(struct btr_node *btrn)
784 {
785 struct btr_buffer_reference *br;
786 size_t size = 0, wrap_consumed = 0;
787
788 FOR_EACH_BUFFER_REF(br, btrn) {
789 if (br->wrap_count != 0) {
790 wrap_consumed = br->consumed;
791 continue;
792 }
793 size += br_available_bytes(br);
794 }
795 assert(wrap_consumed <= size);
796 size -= wrap_consumed;
797 return size;
798 }
799
800 /**
801 * Remove a node from the buffer tree, reconnecting parent and children.
802 *
803 * \param btrn The node to splice out.
804 *
805 * This function is used by buffer tree nodes that do not exist during the
806 * whole lifetime of the buffer tree. Unlike btr_remove_node(), calling
807 * btr_splice_out_node() does not split the tree into disconnected components
808 * but reconnects the buffer tree by making all child nodes of \a btrn children
809 * of the parent of \a btrn.
810 */
811 void btr_splice_out_node(struct btr_node *btrn)
812 {
813 struct btr_node *ch, *tmp;
814
815 assert(btrn);
816 PARA_NOTICE_LOG("splicing out %s\n", btrn->name);
817 btr_pushdown(btrn);
818 if (btrn->parent)
819 list_del(&btrn->node);
820 FOR_EACH_CHILD_SAFE(ch, tmp, btrn) {
821 PARA_INFO_LOG("parent(%s): %s\n", ch->name,
822 btrn->parent? btrn->parent->name : "NULL");
823 ch->parent = btrn->parent;
824 if (btrn->parent)
825 list_move(&ch->node, &btrn->parent->children);
826 }
827 assert(list_empty(&btrn->children));
828 btrn->parent = NULL;
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_INFO_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 }