c62cbf13c3bdc4b621bd891d41e1b74fe24d98fe
[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 /* Only relevant if pool is NULL. */
34 bool dont_free;
35 };
36
37 struct btr_buffer_reference {
38 struct btr_buffer *btrb;
39 size_t consumed;
40 /* Each buffer reference belongs to the buffer queue list of some buffer tree node. */
41 struct list_head node;
42 size_t wrap_count;
43 };
44
45 struct btr_node {
46 char *name;
47 struct btr_node *parent;
48 /* The position of this btr node in the buffer tree. */
49 struct list_head node;
50 /* The children nodes of this btr node are linked together in a list. */
51 struct list_head children;
52 /* Time of first data transfer. */
53 struct timeval start;
54 /**
55 * The input queue is a list of references to btr buffers. Each item on
56 * the list represents an input buffer which has not been completely
57 * used by this btr node.
58 */
59 struct list_head input_queue;
60 btr_command_handler execute;
61 void *context;
62 };
63
64 /**
65 * Create a new buffer pool.
66 *
67 * \param name The name of the new buffer pool.
68 * \param area_size The size in bytes of the pool area.
69 *
70 * \return An opaque pointer to the newly created buffer pool. It must be
71 * passed to btr_pool_free() after it is no longer used to deallocate all
72 * resources.
73 */
74 struct btr_pool *btr_pool_new(const char *name, size_t area_size)
75 {
76 struct btr_pool *btrp;
77
78 PARA_INFO_LOG("%s, %zu bytes\n", name, area_size);
79 btrp = para_malloc(sizeof(*btrp));
80 btrp->area_start = para_malloc(area_size);
81 btrp->area_end = btrp->area_start + area_size;
82 btrp->rhead = btrp->area_start;
83 btrp->whead = btrp->area_start;
84 btrp->name = para_strdup(name);
85 return btrp;
86 }
87
88 /**
89 * Deallocate resources used by a buffer pool.
90 *
91 * \param btrp A pointer obtained via btr_pool_new().
92 */
93 void btr_pool_free(struct btr_pool *btrp)
94 {
95 if (!btrp)
96 return;
97 free(btrp->area_start);
98 free(btrp->name);
99 free(btrp);
100 }
101
102 /**
103 * Return the size of the buffer pool area.
104 *
105 * \param btrp The buffer pool.
106 *
107 * \return The same value which was passed during creation time to
108 * btr_pool_new().
109 */
110 size_t btr_pool_size(struct btr_pool *btrp)
111 {
112 return btrp->area_end - btrp->area_start;
113 }
114
115 static size_t btr_pool_filled(struct btr_pool *btrp)
116 {
117 if (!btrp->whead)
118 return btr_pool_size(btrp);
119 if (btrp->rhead <= btrp->whead)
120 return btrp->whead - btrp->rhead;
121 return btr_pool_size(btrp) - (btrp->rhead - btrp->whead);
122 }
123
124 /**
125 * Get the number of unused bytes in the buffer pool.
126 *
127 * \param btrp The pool.
128 *
129 * \return The number of bytes that can currently be allocated.
130 *
131 * Note that in general the returned number of bytes is not available as a
132 * single contiguous buffer. Use btr_pool_available() to obtain the length of
133 * the largest contiguous buffer that can currently be allocated from the
134 * buffer pool.
135 */
136 size_t btr_pool_unused(struct btr_pool *btrp)
137 {
138 return btr_pool_size(btrp) - btr_pool_filled(btrp);
139 }
140
141 /*
142 * Return maximal size available for one read. This is
143 * smaller than the value returned by btr_pool_unused().
144 */
145 static size_t btr_pool_available(struct btr_pool *btrp)
146 {
147 if (!btrp->whead)
148 return 0;
149 if (btrp->rhead <= btrp->whead)
150 return btrp->area_end - btrp->whead;
151 return btrp->rhead - btrp->whead;
152 }
153
154 /**
155 * Obtain the current write head.
156 *
157 * \param btrp The buffer pool.
158 * \param result The write head is returned here.
159 *
160 * \return The maximal amount of bytes that may be written to the returned
161 * buffer.
162 */
163 size_t btr_pool_get_buffer(struct btr_pool *btrp, char **result)
164 {
165 if (result)
166 *result = btrp->whead;
167 return btr_pool_available(btrp);
168 }
169
170 /**
171 * Get references to buffers pointing to free space of the buffer pool area.
172 *
173 * \param btrp The buffer pool.
174 * \param iov The scatter array.
175 *
176 * \return Zero if the buffer pool is full, one if the free space of the buffer
177 * pool area is available as a single contiguous buffer, two if the free space
178 * consists of two buffers. If this function returns the value n, then n
179 * elements of \a iov are initialized.
180 */
181 int btr_pool_get_buffers(struct btr_pool *btrp, struct iovec iov[2])
182 {
183 size_t sz, unused;
184 char *buf;
185
186 sz = btr_pool_get_buffer(btrp, &buf);
187 if (sz == 0)
188 return 0;
189 iov[0].iov_len = sz;
190 iov[0].iov_base = buf;
191 unused = btr_pool_unused(btrp);
192 if (sz == unused)
193 return 1;
194 iov[1].iov_len = unused - sz;
195 iov[1].iov_base = btrp->area_start;
196 return 2;
197 }
198
199 /**
200 * Mark a part of the buffer pool area as allocated.
201 *
202 * \param btrp The buffer pool.
203 * \param size The amount of bytes to be allocated.
204 *
205 * This is usually called after the caller wrote to the buffer obtained by
206 * btr_pool_get_buffer().
207 */
208 static void btr_pool_allocate(struct btr_pool *btrp, size_t size)
209 {
210 char *end;
211
212 if (size == 0)
213 return;
214 assert(size <= btr_pool_available(btrp));
215 end = btrp->whead + size;
216 assert(end <= btrp->area_end);
217
218 if (end == btrp->area_end) {
219 PARA_DEBUG_LOG("%s: end of pool area reached\n", btrp->name);
220 end = btrp->area_start;
221 }
222 if (end == btrp->rhead) {
223 PARA_DEBUG_LOG("%s btrp buffer full\n", btrp->name);
224 end = NULL; /* buffer full */
225 }
226 btrp->whead = end;
227 }
228
229 static void btr_pool_deallocate(struct btr_pool *btrp, size_t size)
230 {
231 char *end = btrp->rhead + size;
232
233 if (size == 0)
234 return;
235 assert(end <= btrp->area_end);
236 assert(size <= btr_pool_filled(btrp));
237 if (end == btrp->area_end)
238 end = btrp->area_start;
239 if (!btrp->whead)
240 btrp->whead = btrp->rhead;
241 btrp->rhead = end;
242 if (btrp->rhead == btrp->whead)
243 btrp->rhead = btrp->whead = btrp->area_start;
244 }
245
246 #define FOR_EACH_CHILD(_tn, _btrn) list_for_each_entry((_tn), \
247 &((_btrn)->children), node)
248 #define FOR_EACH_CHILD_SAFE(_tn, _tmp, _btrn) \
249 list_for_each_entry_safe((_tn), (_tmp), &((_btrn)->children), node)
250
251 #define FOR_EACH_BUFFER_REF(_br, _btrn) \
252 list_for_each_entry((_br), &(_btrn)->input_queue, node)
253 #define FOR_EACH_BUFFER_REF_SAFE(_br, _tmp, _btrn) \
254 list_for_each_entry_safe((_br), (_tmp), &(_btrn)->input_queue, node)
255
256 /**
257 * Create a new buffer tree node.
258 *
259 * \param bnd Specifies how to create the new node.
260 *
261 * \return A pointer to the newly allocated node.
262 *
263 * This function always succeeds (or calls exit()). The returned pointer must
264 * be freed using btr_free_node() after the node has been removed from the
265 * buffer tree via btr_remove_node().
266 */
267 struct btr_node *btr_new_node(struct btr_node_description *bnd)
268 {
269 struct btr_node *btrn = para_malloc(sizeof(*btrn));
270
271 btrn->name = para_strdup(bnd->name);
272 btrn->parent = bnd->parent;
273 btrn->execute = bnd->handler;
274 btrn->context = bnd->context;
275 btrn->start.tv_sec = 0;
276 btrn->start.tv_usec = 0;
277 INIT_LIST_HEAD(&btrn->children);
278 INIT_LIST_HEAD(&btrn->input_queue);
279 if (!bnd->child) {
280 if (bnd->parent) {
281 list_add_tail(&btrn->node, &bnd->parent->children);
282 PARA_INFO_LOG("new leaf node: %s (child of %s)\n",
283 bnd->name, bnd->parent->name);
284 } else
285 PARA_INFO_LOG("added %s as btr root\n", bnd->name);
286 goto out;
287 }
288 if (!bnd->parent) {
289 assert(!bnd->child->parent);
290 PARA_INFO_LOG("new root: %s (was %s)\n",
291 bnd->name, bnd->child->name);
292 btrn->parent = NULL;
293 list_add_tail(&bnd->child->node, &btrn->children);
294 /* link it in */
295 bnd->child->parent = btrn;
296 goto out;
297 }
298 PARA_EMERG_LOG("inserting internal nodes not yet supported.\n");
299 exit(EXIT_FAILURE);
300 assert(bnd->child->parent == bnd->parent);
301 out:
302 return btrn;
303 }
304
305 /*
306 * Allocate a new btr buffer.
307 *
308 * The freshly allocated buffer will have a zero refcount and will
309 * not be associated with a btr pool.
310 */
311 static struct btr_buffer *new_btrb(char *buf, size_t size)
312 {
313 struct btr_buffer *btrb = para_calloc(sizeof(*btrb));
314
315 btrb->buf = buf;
316 btrb->size = size;
317 return btrb;
318 }
319
320 static void dealloc_buffer(struct btr_buffer *btrb)
321 {
322 if (btrb->pool)
323 btr_pool_deallocate(btrb->pool, btrb->size);
324 else if (!btrb->dont_free)
325 free(btrb->buf);
326 }
327
328 static struct btr_buffer_reference *get_first_input_br(struct btr_node *btrn)
329 {
330 if (list_empty(&btrn->input_queue))
331 return NULL;
332 return list_first_entry(&btrn->input_queue,
333 struct btr_buffer_reference, node);
334 }
335
336 /*
337 * Deallocate the reference, release the resources if refcount drops to zero.
338 */
339 static void btr_drop_buffer_reference(struct btr_buffer_reference *br)
340 {
341 struct btr_buffer *btrb = br->btrb;
342
343 list_del(&br->node);
344 free(br);
345 btrb->refcount--;
346 if (btrb->refcount == 0) {
347 dealloc_buffer(btrb);
348 free(btrb);
349 }
350 }
351
352 static void add_btrb_to_children(struct btr_buffer *btrb,
353 struct btr_node *btrn, size_t consumed)
354 {
355 struct btr_node *ch;
356
357 if (btrn->start.tv_sec == 0)
358 btrn->start = *now;
359 FOR_EACH_CHILD(ch, btrn) {
360 struct btr_buffer_reference *br = para_calloc(sizeof(*br));
361 br->btrb = btrb;
362 br->consumed = consumed;
363 list_add_tail(&br->node, &ch->input_queue);
364 btrb->refcount++;
365 if (ch->start.tv_sec == 0)
366 ch->start = *now;
367 }
368 }
369
370 /**
371 * Insert a malloced buffer into the buffer tree.
372 *
373 * \param buf The buffer to insert.
374 * \param size The size of \a buf in bytes.
375 * \param btrn Position in the buffer tree to create the output.
376 *
377 * This creates references to \a buf and adds these references to each child of
378 * \a btrn. The buffer will be freed using standard free() once no buffer tree
379 * node is referencing it any more.
380 *
381 * Note that this function must not be used if \a buf was obtained from a
382 * buffer pool. Use btr_add_output_pool() in this case.
383 */
384 void btr_add_output(char *buf, size_t size, struct btr_node *btrn)
385 {
386 struct btr_buffer *btrb;
387
388 assert(size != 0);
389 if (list_empty(&btrn->children)) {
390 free(buf);
391 return;
392 }
393 btrb = new_btrb(buf, size);
394 add_btrb_to_children(btrb, btrn, 0);
395 }
396
397 /**
398 * Insert a buffer into the buffer tree, non-freeing variant.
399 *
400 * \param buf See \ref btr_add_output().
401 * \param size See \ref btr_add_output().
402 * \param btrn See \ref btr_add_output().
403 *
404 * This is similar to btr_add_output() but additionally sets the \p dont_free
405 * flag on \a buf. If the refcount for the buffer drops to zero, \a buf will
406 * not be deallocated if this flag is set.
407 *
408 * The \p dont_free bit also prevents the children of \a btrn from modifying
409 * the buffer contents inplace. Specifically, \ref btr_inplace_ok() returns
410 * false if there is any buffer in the input queue with the \p dont_free bit
411 * set.
412 */
413 void btr_add_output_dont_free(const char *buf, size_t size, struct btr_node *btrn)
414 {
415 struct btr_buffer *btrb;
416
417 assert(size != 0);
418 if (list_empty(&btrn->children))
419 return;
420 btrb = new_btrb((char *)buf, size);
421 btrb->dont_free = true;
422 add_btrb_to_children(btrb, btrn, 0);
423 }
424
425 /**
426 * Feed data to child nodes of a buffer tree node.
427 *
428 * \param btrp The buffer pool.
429 * \param size The number of bytes to be allocated and fed to each child.
430 * \param btrn The node whose children are to be fed.
431 *
432 * This function allocates the amount of bytes from the buffer pool area,
433 * starting at the current value of the write head, and creates buffer
434 * references to the resulting part of the buffer pool area, one for each child
435 * of \a btrn. The references are then fed into the input queue of each child.
436 */
437 void btr_add_output_pool(struct btr_pool *btrp, size_t size,
438 struct btr_node *btrn)
439 {
440 struct btr_buffer *btrb;
441 char *buf;
442 size_t avail;
443
444 assert(size != 0);
445 if (list_empty(&btrn->children))
446 return;
447 avail = btr_pool_get_buffer(btrp, &buf);
448 assert(avail >= size);
449 btr_pool_allocate(btrp, size);
450 btrb = new_btrb(buf, size);
451 btrb->pool = btrp;
452 add_btrb_to_children(btrb, btrn, 0);
453 }
454
455 /**
456 * Copy data to write head of a buffer pool and feed it to all children nodes.
457 *
458 * \param src The source buffer.
459 * \param n The size of the source buffer in bytes.
460 * \param btrp The destination buffer pool.
461 * \param btrn Add the data as output of this node.
462 *
463 * This is expensive. The caller must make sure the data fits into the buffer
464 * pool area.
465 */
466 void btr_copy(const void *src, size_t n, struct btr_pool *btrp,
467 struct btr_node *btrn)
468 {
469 char *buf;
470 size_t sz, copy;
471
472 if (n == 0)
473 return;
474 assert(n <= btr_pool_unused(btrp));
475 sz = btr_pool_get_buffer(btrp, &buf);
476 copy = PARA_MIN(sz, n);
477 memcpy(buf, src, copy);
478 btr_add_output_pool(btrp, copy, btrn);
479 if (copy == n)
480 return;
481 sz = btr_pool_get_buffer(btrp, &buf);
482 assert(sz >= n - copy);
483 memcpy(buf, src + copy, n - copy);
484 btr_add_output_pool(btrp, n - copy, btrn);
485 }
486
487 static void btr_pushdown_br(struct btr_buffer_reference *br, struct btr_node *btrn)
488 {
489 add_btrb_to_children(br->btrb, btrn, br->consumed);
490 btr_drop_buffer_reference(br);
491 }
492
493 /**
494 * Feed all buffer references of the input queue through the output channel.
495 *
496 * \param btrn The node whose buffer references should be pushed down.
497 *
498 * This function is useful for filters that do not change the contents of the
499 * buffers at all, like the wav filter or the amp filter if no amplification
500 * was specified. This function is rather cheap.
501 *
502 * \sa \ref btr_pushdown_one().
503 */
504 void btr_pushdown(struct btr_node *btrn)
505 {
506 struct btr_buffer_reference *br, *tmp;
507
508 FOR_EACH_BUFFER_REF_SAFE(br, tmp, btrn)
509 btr_pushdown_br(br, btrn);
510 }
511
512 /**
513 * Feed the next buffer of the input queue through the output channel.
514 *
515 * \param btrn The node whose first input queue buffer should be pushed down.
516 *
517 * This works like \ref btr_pushdown() but pushes down only one buffer
518 * reference.
519 */
520 void btr_pushdown_one(struct btr_node *btrn)
521 {
522 struct btr_buffer_reference *br;
523
524 if (list_empty(&btrn->input_queue))
525 return;
526 br = list_first_entry(&btrn->input_queue, struct btr_buffer_reference, node);
527 btr_pushdown_br(br, btrn);
528 }
529
530 /*
531 * Find out whether a node is a leaf node.
532 *
533 * \param btrn The node to check.
534 *
535 * \return True if this node has no children. False otherwise.
536 */
537 static bool btr_no_children(struct btr_node *btrn)
538 {
539 return list_empty(&btrn->children);
540 }
541
542 /**
543 * Find out whether a node is an orphan node.
544 *
545 * \param btrn The buffer tree node.
546 *
547 * \return True if \a btrn has no parent.
548 *
549 * This function will always return true for the root node. However in case
550 * nodes have been removed from the tree, other nodes may become orphans too.
551 */
552 bool btr_no_parent(struct btr_node *btrn)
553 {
554 return !btrn->parent;
555 }
556
557 /**
558 * Find out whether it is OK to change an input buffer.
559 *
560 * \param btrn The buffer tree node to check.
561 *
562 * This is used by filters that produce exactly the same amount of output as
563 * there is input. The amp filter which multiplies each sample by some number
564 * is an example of such a filter. If there are no other nodes in the buffer
565 * tree that read the same input stream (i.e. if \a btrn has no siblings), a
566 * node may modify its input buffer directly and push down the modified buffer
567 * to its children, thereby avoiding to allocate a possibly large additional
568 * buffer.
569 *
570 * Since the buffer tree may change at any time, this function should be called
571 * during each post_select call.
572 *
573 * \return True if \a btrn has no siblings.
574 */
575 bool btr_inplace_ok(struct btr_node *btrn)
576 {
577 struct btr_buffer_reference *br;
578 FOR_EACH_BUFFER_REF(br, btrn) {
579 struct btr_buffer *btrb = br->btrb;
580 if (btrb->refcount > 1)
581 return false;
582 if (btrb->dont_free == true)
583 return false;
584 }
585 return true;
586 }
587
588 static inline size_t br_available_bytes(struct btr_buffer_reference *br)
589 {
590 return br->btrb->size - br->consumed;
591 }
592
593 static size_t btr_get_buffer_by_reference(struct btr_buffer_reference *br, char **buf)
594 {
595 if (buf)
596 *buf = br->btrb->buf + br->consumed;
597 return br_available_bytes(br);
598 }
599
600 /**
601 * Obtain the next buffer of the input queue, omitting data.
602 *
603 * \param btrn The node whose input queue is to be queried.
604 * \param omit Number of bytes to be omitted.
605 * \param bufp Result pointer.
606 *
607 * If a buffer tree node needs more input data but can not consume the data it
608 * already has (because it might be needed again later) this function can be
609 * used instead of btr_next_buffer() to get a reference to the buffer obtained
610 * by skipping the given number of bytes. Skipped input bytes are not consumed.
611 *
612 * With a zero \a omit argument, this function is equivalent to \ref
613 * btr_next_buffer().
614 *
615 * \return Number of bytes in \a bufp. If there are less than or equal to \a
616 * omit many bytes available in the input queue of the buffer tree node pointed
617 * to by \a btrn, the function returns zero and the value of \a bufp is
618 * undefined.
619 */
620 size_t btr_next_buffer_omit(struct btr_node *btrn, size_t omit, char **bufp)
621 {
622 struct btr_buffer_reference *br;
623 size_t wrap_count, sz, rv = 0;
624 char *buf, *result = NULL;
625
626 br = get_first_input_br(btrn);
627 if (!br)
628 return 0;
629 wrap_count = br->wrap_count;
630 if (wrap_count > 0) { /* we have a wrap buffer */
631 sz = btr_get_buffer_by_reference(br, &buf);
632 if (sz > omit) { /* and it's big enough */
633 result = buf + omit;
634 rv = sz - omit;
635 /*
636 * Wrap buffers are allocated by malloc(), so the next
637 * buffer ref will not align nicely, so we return the
638 * tail of the wrap buffer.
639 */
640 goto out;
641 }
642 /*
643 * The next wrap_count bytes exist twice, in the wrap buffer
644 * and as a buffer reference in the buffer tree pool.
645 */
646 omit += wrap_count;
647 }
648 /*
649 * For buffer tree pools, the buffers in the list align, i.e. the next
650 * buffer in the list starts directly at the end of its predecessor. In
651 * this case we merge adjacent buffers and return one larger buffer
652 * instead.
653 */
654 FOR_EACH_BUFFER_REF(br, btrn) {
655 sz = btr_get_buffer_by_reference(br, &buf);
656 if (result) {
657 if (result + rv != buf)
658 goto out;
659 rv += sz;
660 } else if (sz > omit) {
661 result = buf + omit;
662 rv = sz - omit;
663 } else
664 omit -= sz;
665 }
666 if (!result)
667 return 0;
668 out:
669 if (bufp)
670 *bufp = result;
671 return rv;
672 }
673
674 /**
675 * Obtain the next buffer of the input queue of a buffer tree node.
676 *
677 * \param btrn The node whose input queue is to be queried.
678 * \param bufp Result pointer.
679 *
680 * \return The number of bytes that can be read from buf.
681 *
682 * The call of this function is is equivalent to calling \ref
683 * btr_next_buffer_omit() with an \a omit value of zero.
684 */
685 size_t btr_next_buffer(struct btr_node *btrn, char **bufp)
686 {
687 return btr_next_buffer_omit(btrn, 0, bufp);
688 }
689
690 /**
691 * Deallocate the given number of bytes from the input queue.
692 *
693 * \param btrn The buffer tree node.
694 * \param numbytes The number of bytes to be deallocated.
695 *
696 * This function must be used to get rid of existing buffer references in the
697 * node's input queue. If no references to a buffer remain, the underlying
698 * buffers are either freed (in the non-buffer pool case) or the read head of
699 * the buffer pool is being advanced.
700 *
701 * Note that \a numbytes may be smaller than the buffer size. In this case the
702 * buffer is not deallocated and subsequent calls to btr_next_buffer() return
703 * the remaining part of the buffer.
704 */
705 void btr_consume(struct btr_node *btrn, size_t numbytes)
706 {
707 struct btr_buffer_reference *br, *tmp;
708 size_t sz;
709
710 if (numbytes == 0)
711 return;
712 br = get_first_input_br(btrn);
713 assert(br);
714
715 if (br->wrap_count == 0) {
716 /*
717 * No wrap buffer. Drop buffer references whose buffer
718 * has been fully used. */
719 FOR_EACH_BUFFER_REF_SAFE(br, tmp, btrn) {
720 if (br->consumed + numbytes <= br->btrb->size) {
721 br->consumed += numbytes;
722 if (br->consumed == br->btrb->size)
723 btr_drop_buffer_reference(br);
724 return;
725 }
726 numbytes -= br->btrb->size - br->consumed;
727 btr_drop_buffer_reference(br);
728 }
729 assert(false);
730 }
731 /*
732 * We have a wrap buffer, consume from it. If in total, i.e. including
733 * previous calls to brt_consume(), less than wrap_count has been
734 * consumed, there's nothing more we can do.
735 *
736 * Otherwise we drop the wrap buffer and consume from subsequent
737 * buffers of the input queue the correct amount of bytes. This is the
738 * total number of bytes that have been consumed from the wrap buffer.
739 */
740 PARA_DEBUG_LOG("consuming %zu/%zu bytes from wrap buffer\n", numbytes,
741 br_available_bytes(br));
742
743 assert(numbytes <= br_available_bytes(br));
744 if (br->consumed + numbytes < br->wrap_count) {
745 br->consumed += numbytes;
746 return;
747 }
748 PARA_DEBUG_LOG("dropping wrap buffer (%zu bytes)\n", br->btrb->size);
749 /* get rid of the wrap buffer */
750 sz = br->consumed + numbytes;
751 btr_drop_buffer_reference(br);
752 return btr_consume(btrn, sz);
753 }
754
755 /**
756 * Clear the input queue of a buffer tree node.
757 *
758 * \param btrn The node whose input queue should be cleared.
759 */
760 void btr_drain(struct btr_node *btrn)
761 {
762 struct btr_buffer_reference *br, *tmp;
763
764 FOR_EACH_BUFFER_REF_SAFE(br, tmp, btrn)
765 btr_drop_buffer_reference(br);
766 }
767
768 /**
769 * Remove a node from a buffer tree.
770 *
771 * \param btrnp Determines the node to remove.
772 *
773 * This orphans all children of the node given by \a btrnp and removes this
774 * node from the child list of its parent. Moreover, the input queue is flushed
775 * and the node pointer given by \a btrp is set to \p NULL.
776 *
777 * \sa \ref btr_splice_out_node.
778 */
779 void btr_remove_node(struct btr_node **btrnp)
780 {
781 struct btr_node *ch;
782 struct btr_node *btrn;
783
784 if (!btrnp)
785 return;
786 btrn = *btrnp;
787 if (!btrn)
788 goto out;
789 PARA_INFO_LOG("removing btr node %s from buffer tree\n", btrn->name);
790 FOR_EACH_CHILD(ch, btrn)
791 ch->parent = NULL;
792 btr_drain(btrn);
793 if (btrn->parent)
794 list_del(&btrn->node);
795 free(btrn->name);
796 free(btrn);
797 out:
798 *btrnp = NULL;
799 }
800
801 /**
802 * Return the amount of available input bytes of a buffer tree node.
803 *
804 * \param btrn The node whose input size should be computed.
805 *
806 * \return The total number of bytes available in the node's input
807 * queue.
808 *
809 * This simply iterates over all buffer references in the input queue and
810 * returns the sum of the sizes of all references.
811 */
812 size_t btr_get_input_queue_size(struct btr_node *btrn)
813 {
814 struct btr_buffer_reference *br;
815 size_t size = 0, wrap_consumed = 0;
816
817 FOR_EACH_BUFFER_REF(br, btrn) {
818 if (br->wrap_count != 0) {
819 wrap_consumed = br->consumed;
820 continue;
821 }
822 size += br_available_bytes(br);
823 }
824 assert(wrap_consumed <= size);
825 size -= wrap_consumed;
826 return size;
827 }
828
829 /**
830 * Remove a node from the buffer tree, reconnecting parent and children.
831 *
832 * \param btrn The node to splice out.
833 *
834 * This function is used by buffer tree nodes that do not exist during the
835 * whole lifetime of the buffer tree. Unlike btr_remove_node(), calling
836 * btr_splice_out_node() does not split the tree into disconnected components
837 * but reconnects the buffer tree by making all child nodes of \a btrn children
838 * of the parent of \a btrn.
839 */
840 void btr_splice_out_node(struct btr_node *btrn)
841 {
842 struct btr_node *ch, *tmp;
843
844 assert(btrn);
845 PARA_NOTICE_LOG("splicing out %s\n", btrn->name);
846 btr_pushdown(btrn);
847 if (btrn->parent)
848 list_del(&btrn->node);
849 FOR_EACH_CHILD_SAFE(ch, tmp, btrn) {
850 PARA_INFO_LOG("parent(%s): %s\n", ch->name,
851 btrn->parent? btrn->parent->name : "NULL");
852 ch->parent = btrn->parent;
853 if (btrn->parent)
854 list_move(&ch->node, &btrn->parent->children);
855 }
856 assert(list_empty(&btrn->children));
857 btrn->parent = NULL;
858 }
859
860 /**
861 * Return number of queued output bytes of a buffer tree node.
862 *
863 * \param btrn The node whose output queue size should be computed.
864 *
865 * \return This function iterates over all children of the given node and
866 * returns the size of the largest input queue.
867 */
868 size_t btr_get_output_queue_size(struct btr_node *btrn)
869 {
870 size_t max_size = 0;
871 struct btr_node *ch;
872
873 FOR_EACH_CHILD(ch, btrn) {
874 size_t size = btr_get_input_queue_size(ch);
875 max_size = PARA_MAX(max_size, size);
876 }
877 return max_size;
878 }
879
880 /**
881 * Execute a inter-node command on a parent node.
882 *
883 * \param btrn The node to start looking.
884 * \param command The command to execute.
885 * \param value_result Additional arguments and result value.
886 *
887 * This function traverses the buffer tree upwards and looks for parent nodes
888 * of \a btrn that understands \a command. On the first such node the command
889 * is executed, and the result is stored in \a value_result.
890 *
891 * \return \p -ENOTSUP if no parent node of \a btrn understands \a command.
892 * Otherwise the return value of the command handler is returned.
893 */
894 int btr_exec_up(struct btr_node *btrn, const char *command, char **value_result)
895 {
896 int ret;
897
898 for (; btrn; btrn = btrn->parent) {
899 struct btr_node *parent = btrn->parent;
900 if (!parent)
901 return -ERRNO_TO_PARA_ERROR(ENOTSUP);
902 if (!parent->execute)
903 continue;
904 PARA_INFO_LOG("parent: %s, cmd: %s\n", parent->name, command);
905 ret = parent->execute(parent, command, value_result);
906 if (ret == -ERRNO_TO_PARA_ERROR(ENOTSUP))
907 continue;
908 if (ret < 0)
909 return ret;
910 if (value_result && *value_result)
911 PARA_INFO_LOG("%s(%s): %s\n", command, parent->name,
912 *value_result);
913 return 1;
914 }
915 return -ERRNO_TO_PARA_ERROR(ENOTSUP);
916 }
917
918 /**
919 * Obtain the context of a buffer node tree.
920 *
921 * \param btrn The node whose output queue size should be computed.
922 *
923 * \return A pointer to the \a context address specified at node creation time.
924 *
925 * \sa btr_new_node(), struct \ref btr_node_description.
926 */
927 void *btr_context(struct btr_node *btrn)
928 {
929 return btrn->context;
930 }
931
932 static bool need_buffer_pool_merge(struct btr_node *btrn)
933 {
934 struct btr_buffer_reference *br = get_first_input_br(btrn);
935
936 if (!br)
937 return false;
938 if (br->wrap_count != 0)
939 return true;
940 if (br->btrb->pool)
941 return true;
942 return false;
943 }
944
945 static void merge_input_pool(struct btr_node *btrn, size_t dest_size)
946 {
947 struct btr_buffer_reference *br, *wbr = NULL;
948 int num_refs; /* including wrap buffer */
949 char *buf, *buf1 = NULL, *buf2 = NULL;
950 size_t sz, sz1 = 0, sz2 = 0, wb_consumed = 0;
951
952 br = get_first_input_br(btrn);
953 if (!br || br_available_bytes(br) >= dest_size)
954 return;
955 num_refs = 0;
956 FOR_EACH_BUFFER_REF(br, btrn) {
957 num_refs++;
958 sz = btr_get_buffer_by_reference(br, &buf);
959 if (sz == 0)
960 break;
961 if (br->wrap_count != 0) {
962 assert(!wbr);
963 assert(num_refs == 1);
964 wbr = br;
965 if (sz >= dest_size)
966 return;
967 wb_consumed = br->consumed;
968 continue;
969 }
970 if (!buf1) {
971 buf1 = buf;
972 sz1 = sz;
973 goto next;
974 }
975 if (buf1 + sz1 == buf) {
976 sz1 += sz;
977 goto next;
978 }
979 if (!buf2) {
980 buf2 = buf;
981 sz2 = sz;
982 goto next;
983 }
984 assert(buf2 + sz2 == buf);
985 sz2 += sz;
986 next:
987 if (sz1 + sz2 >= dest_size + wb_consumed)
988 break;
989 }
990 if (!buf2) /* nothing to do */
991 return;
992 assert(buf1 && sz2 > 0);
993 /*
994 * If the second buffer is large, we only take the first part of it to
995 * avoid having to memcpy() huge buffers.
996 */
997 sz2 = PARA_MIN(sz2, (size_t)(64 * 1024));
998 if (!wbr) {
999 /* Make a new wrap buffer combining buf1 and buf2. */
1000 sz = sz1 + sz2;
1001 buf = para_malloc(sz);
1002 PARA_DEBUG_LOG("merging input buffers: (%p:%zu, %p:%zu) -> %p:%zu\n",
1003 buf1, sz1, buf2, sz2, buf, sz);
1004 memcpy(buf, buf1, sz1);
1005 memcpy(buf + sz1, buf2, sz2);
1006 br = para_calloc(sizeof(*br));
1007 br->btrb = new_btrb(buf, sz);
1008 br->btrb->refcount = 1;
1009 br->consumed = 0;
1010 /* This is a wrap buffer */
1011 br->wrap_count = sz1;
1012 para_list_add(&br->node, &btrn->input_queue);
1013 return;
1014 }
1015 /*
1016 * We already have a wrap buffer, but it is too small. It might be
1017 * partially used.
1018 */
1019 if (wbr->wrap_count == sz1 && wbr->btrb->size >= sz1 + sz2) /* nothing we can do about it */
1020 return;
1021 sz = sz1 + sz2 - wbr->btrb->size; /* amount of new data */
1022 PARA_DEBUG_LOG("increasing wrap buffer %zu -> %zu\n", wbr->btrb->size,
1023 wbr->btrb->size + sz);
1024 wbr->btrb->size += sz;
1025 wbr->btrb->buf = para_realloc(wbr->btrb->buf, wbr->btrb->size);
1026 /* copy the new data to the end of the reallocated buffer */
1027 assert(sz2 >= sz);
1028 memcpy(wbr->btrb->buf + wbr->btrb->size - sz, buf2 + sz2 - sz, sz);
1029 }
1030
1031 /**
1032 * Merge the first two input buffers into one.
1033 *
1034 * This is a quite expensive operation.
1035 *
1036 * \return The number of buffers that have been available (zero, one or two).
1037 */
1038 static int merge_input(struct btr_node *btrn)
1039 {
1040 struct btr_buffer_reference *brs[2], *br;
1041 char *bufs[2], *buf;
1042 size_t szs[2], sz;
1043 int i;
1044
1045 if (list_empty(&btrn->input_queue))
1046 return 0;
1047 if (list_is_singular(&btrn->input_queue))
1048 return 1;
1049 i = 0;
1050 /* get references to the first two buffers */
1051 FOR_EACH_BUFFER_REF(br, btrn) {
1052 brs[i] = br;
1053 szs[i] = btr_get_buffer_by_reference(brs[i], bufs + i);
1054 i++;
1055 if (i == 2)
1056 break;
1057 }
1058 assert(i == 2);
1059 /* make a new btrb that combines the two buffers and a br to it. */
1060 sz = szs[0] + szs[1];
1061 buf = para_malloc(sz);
1062 PARA_DEBUG_LOG("%s: memory merging input buffers: (%zu, %zu) -> %zu\n",
1063 btrn->name, szs[0], szs[1], sz);
1064 memcpy(buf, bufs[0], szs[0]);
1065 memcpy(buf + szs[0], bufs[1], szs[1]);
1066
1067 br = para_calloc(sizeof(*br));
1068 br->btrb = new_btrb(buf, sz);
1069 br->btrb->refcount = 1;
1070
1071 /* replace the first two refs by the new one */
1072 btr_drop_buffer_reference(brs[0]);
1073 btr_drop_buffer_reference(brs[1]);
1074 para_list_add(&br->node, &btrn->input_queue);
1075 return 2;
1076 }
1077
1078 /**
1079 * Combine input queue buffers.
1080 *
1081 * \param btrn The buffer tree node whose input should be merged.
1082 * \param dest_size Stop merging if a buffer of at least this size exists.
1083 *
1084 * Used to combine as many buffers as needed into a single buffer whose size is
1085 * at least \a dest_size. This function is rather cheap in case the parent node
1086 * uses buffer pools and rather expensive otherwise.
1087 *
1088 * Note that if less than \a dest_size bytes are available in total, this
1089 * function does nothing and subsequent calls to btr_next_buffer() will still
1090 * return a buffer size less than \a dest_size.
1091 */
1092 void btr_merge(struct btr_node *btrn, size_t dest_size)
1093 {
1094 if (need_buffer_pool_merge(btrn))
1095 return merge_input_pool(btrn, dest_size);
1096 for (;;) {
1097 char *buf;
1098 size_t len = btr_next_buffer(btrn, &buf);
1099 if (len >= dest_size)
1100 return;
1101 PARA_DEBUG_LOG("input size = %zu < %zu = dest\n", len, dest_size);
1102 if (merge_input(btrn) < 2)
1103 return;
1104 }
1105 }
1106
1107 static bool btr_eof(struct btr_node *btrn)
1108 {
1109 char *buf;
1110 size_t len = btr_next_buffer(btrn, &buf);
1111
1112 return (len == 0 && btr_no_parent(btrn));
1113 }
1114
1115 static void log_tree_recursively(struct btr_node *btrn, int loglevel, int depth)
1116 {
1117 struct btr_node *ch;
1118 const char spaces[] = " ", *space = spaces + 16 - depth;
1119
1120 if (depth > 16)
1121 return;
1122 para_log(loglevel, "%s%s\n", space, btrn->name);
1123 FOR_EACH_CHILD(ch, btrn)
1124 log_tree_recursively(ch, loglevel, depth + 1);
1125 }
1126
1127 /**
1128 * Write the current buffer (sub-)tree to the log.
1129 *
1130 * \param btrn Start logging at this node.
1131 * \param loglevel Set severity with which the tree should be logged.
1132 */
1133 void btr_log_tree(struct btr_node *btrn, int loglevel)
1134 {
1135 return log_tree_recursively(btrn, loglevel, 0);
1136 }
1137
1138 /**
1139 * Find the node with the given name in the buffer tree.
1140 *
1141 * \param name The name of the node to search.
1142 * \param root Where to start the search.
1143 *
1144 * \return A pointer to the node with the given name on success. If \a name is
1145 * \p NULL, the function returns \a root. If there is no node with the given
1146 * name, \p NULL is returned.
1147 */
1148 struct btr_node *btr_search_node(const char *name, struct btr_node *root)
1149 {
1150 struct btr_node *ch;
1151
1152 if (!name)
1153 return root;
1154 if (!strcmp(root->name, name))
1155 return root;
1156 FOR_EACH_CHILD(ch, root) {
1157 struct btr_node *result = btr_search_node(name, ch);
1158 if (result)
1159 return result;
1160 }
1161 return NULL;
1162 }
1163
1164 /** 640K ought to be enough for everybody ;) */
1165 #define BTRN_MAX_PENDING (96 * 1024)
1166
1167 /**
1168 * Return the current state of a buffer tree node.
1169 *
1170 * \param btrn The node whose state should be queried.
1171 * \param min_iqs The minimal input queue size.
1172 * \param type The supposed type of \a btrn.
1173 *
1174 * Most users of the buffer tree subsystem call this function from both
1175 * their pre_select and the post_select methods.
1176 *
1177 * \return Negative if an error condition was detected, zero if there
1178 * is nothing to do and positive otherwise.
1179 *
1180 * Examples:
1181 *
1182 * - If a non-root node has no parent and an empty input queue, the function
1183 * returns \p -E_BTR_EOF. Similarly, if a non-leaf node has no children, \p
1184 * -E_BTR_NO_CHILD is returned.
1185 *
1186 * - If less than \a min_iqs many bytes are available in the input queue and no
1187 * EOF condition was detected, the function returns zero.
1188 *
1189 * - If there's plenty of data left in the input queue of the children of \a
1190 * btrn, the function also returns zero in order to bound the memory usage of
1191 * the buffer tree.
1192 */
1193 int btr_node_status(struct btr_node *btrn, size_t min_iqs,
1194 enum btr_node_type type)
1195 {
1196 size_t iqs;
1197
1198 assert(btrn);
1199 if (type != BTR_NT_LEAF) {
1200 if (btr_no_children(btrn))
1201 return -E_BTR_NO_CHILD;
1202 if (btr_get_output_queue_size(btrn) > BTRN_MAX_PENDING)
1203 return 0;
1204 }
1205 if (type != BTR_NT_ROOT) {
1206 if (btr_eof(btrn))
1207 return -E_BTR_EOF;
1208 iqs = btr_get_input_queue_size(btrn);
1209 if (iqs == 0) /* we have a parent, because not eof */
1210 return 0;
1211 if (iqs < min_iqs && !btr_no_parent(btrn))
1212 return 0;
1213 }
1214 return 1;
1215 }
1216
1217 /**
1218 * Get the time of the first I/O for a buffer tree node.
1219 *
1220 * \param btrn The node whose I/O time should be obtained.
1221 * \param tv Result pointer.
1222 *
1223 * Mainly useful for the time display of para_audiod.
1224 */
1225 void btr_get_node_start(struct btr_node *btrn, struct timeval *tv)
1226 {
1227 *tv = btrn->start;
1228 }