summaryrefslogtreecommitdiff
path: root/src/chunk.c
blob: c61afebfdaa56c3eef10310332549cac63e0bd35 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
#include "first.h"

/**
 * the network chunk-API
 *
 *
 */

#include "chunk.h"
#include "fdevent.h"
#include "log.h"

#include <sys/types.h>
#include <sys/stat.h>
#include "sys-mmap.h"

#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>

#include <errno.h>
#include <string.h>

/* default 1MB, upper limit 128MB */
#define DEFAULT_TEMPFILE_SIZE (1 * 1024 * 1024)
#define MAX_TEMPFILE_SIZE (128 * 1024 * 1024)

static size_t chunk_buf_sz = 4096;
static chunk *chunks;
static chunk *chunk_buffers;
static array *chunkqueue_default_tempdirs = NULL;
static unsigned int chunkqueue_default_tempfile_size = DEFAULT_TEMPFILE_SIZE;

void chunkqueue_set_chunk_size (size_t sz)
{
    chunk_buf_sz = sz > 0 ? ((sz + 1023) & ~1023uL) : 4096;
}

void chunkqueue_set_tempdirs_default_reset (void)
{
    chunkqueue_default_tempdirs = NULL;
    chunkqueue_default_tempfile_size = DEFAULT_TEMPFILE_SIZE;
}

chunkqueue *chunkqueue_init(void) {
	chunkqueue *cq;

	cq = calloc(1, sizeof(*cq));
	force_assert(NULL != cq);

	cq->first = NULL;
	cq->last = NULL;

	cq->tempdirs              = chunkqueue_default_tempdirs;
	cq->upload_temp_file_size = chunkqueue_default_tempfile_size;

	return cq;
}

static chunk *chunk_init(size_t sz) {
	chunk *c;

	c = calloc(1, sizeof(*c));
	force_assert(NULL != c);

	c->type = MEM_CHUNK;
	c->mem = buffer_init();
	c->file.start = c->file.length = c->file.mmap.offset = 0;
	c->file.fd = -1;
	c->file.mmap.start = MAP_FAILED;
	c->file.mmap.length = 0;
	c->file.is_temp = 0;
	c->offset = 0;
	c->next = NULL;

	buffer_string_prepare_copy(c->mem, sz-1);

	return c;
}

static void chunk_reset_file_chunk(chunk *c) {
	if (c->file.is_temp && !buffer_string_is_empty(c->mem)) {
		unlink(c->mem->ptr);
	}
	if (c->file.fd != -1) {
		close(c->file.fd);
		c->file.fd = -1;
	}
	if (MAP_FAILED != c->file.mmap.start) {
		munmap(c->file.mmap.start, c->file.mmap.length);
		c->file.mmap.start = MAP_FAILED;
	}
	c->file.start = c->file.length = c->file.mmap.offset = 0;
	c->file.mmap.length = 0;
	c->file.is_temp = 0;
	c->type = MEM_CHUNK;
}

static void chunk_reset(chunk *c) {
	if (c->type == FILE_CHUNK) chunk_reset_file_chunk(c);

	buffer_clear(c->mem);
	c->offset = 0;
}

static void chunk_free(chunk *c) {
	if (c->type == FILE_CHUNK) chunk_reset_file_chunk(c);
	buffer_free(c->mem);
	free(c);
}

buffer * chunk_buffer_acquire(void) {
    chunk *c;
    buffer *b;
    if (chunks) {
        c = chunks;
        chunks = c->next;
    }
    else {
        c = chunk_init(chunk_buf_sz);
    }
    c->next = chunk_buffers;
    chunk_buffers = c;
    b = c->mem;
    c->mem = NULL;
    return b;
}

void chunk_buffer_release(buffer *b) {
    if (NULL == b) return;
    if (b->size >= chunk_buf_sz && chunk_buffers) {
        chunk *c = chunk_buffers;
        chunk_buffers = c->next;
        c->mem = b;
        c->next = chunks;
        chunks = c;
        buffer_clear(b);
    }
    else {
        buffer_free(b);
    }
}

static chunk * chunk_acquire(void) {
    if (chunks) {
        chunk *c = chunks;
        chunks = c->next;
        return c;
    }
    else {
        return chunk_init(chunk_buf_sz);
    }
}

static void chunk_release(chunk *c) {
    if (c->mem->size >= chunk_buf_sz) {
        chunk_reset(c);
        c->next = chunks;
        chunks = c;
    }
    else {
        chunk_free(c);
    }
}

void chunkqueue_chunk_pool_clear(void)
{
    for (chunk *next, *c = chunks; c; c = next) {
        next = c->next;
        chunk_free(c);
    }
    chunks = NULL;
}

void chunkqueue_chunk_pool_free(void)
{
    chunkqueue_chunk_pool_clear();
    for (chunk *next, *c = chunk_buffers; c; c = next) {
        next = c->next;
        c->mem = buffer_init(); /*(chunk_reset() expects c->mem != NULL)*/
        chunk_free(c);
    }
    chunk_buffers = NULL;
}

static off_t chunk_remaining_length(const chunk *c) {
	off_t len = 0;
	switch (c->type) {
	case MEM_CHUNK:
		len = buffer_string_length(c->mem);
		break;
	case FILE_CHUNK:
		len = c->file.length;
		break;
	default:
		force_assert(c->type == MEM_CHUNK || c->type == FILE_CHUNK);
		break;
	}
	force_assert(c->offset <= len);
	return len - c->offset;
}

void chunkqueue_free(chunkqueue *cq) {
	chunk *c, *pc;

	if (NULL == cq) return;

	for (c = cq->first; c; ) {
		pc = c;
		c = c->next;
		chunk_release(pc);
	}

	free(cq);
}

static void chunkqueue_prepend_chunk(chunkqueue *cq, chunk *c) {
	c->next = cq->first;
	cq->first = c;

	if (NULL == cq->last) {
		cq->last = c;
	}
}

static void chunkqueue_append_chunk(chunkqueue *cq, chunk *c) {
	c->next = NULL;
	if (cq->last) {
		cq->last->next = c;
	}
	cq->last = c;

	if (NULL == cq->first) {
		cq->first = c;
	}
}

static chunk * chunkqueue_prepend_mem_chunk(chunkqueue *cq) {
    chunk *c = chunk_acquire();
    chunkqueue_prepend_chunk(cq, c);
    return c;
}

static chunk * chunkqueue_append_mem_chunk(chunkqueue *cq) {
    chunk *c = chunk_acquire();
    chunkqueue_append_chunk(cq, c);
    return c;
}

static chunk * chunkqueue_append_file_chunk(chunkqueue *cq, buffer *fn, off_t offset, off_t len) {
    chunk *c = chunk_acquire();
    chunkqueue_append_chunk(cq, c);
    c->type = FILE_CHUNK;
    c->file.start = offset;
    c->file.length = len;
    cq->bytes_in += len;
    buffer_copy_buffer(c->mem, fn);
    return c;
}

void chunkqueue_reset(chunkqueue *cq) {
	chunk *cur = cq->first;

	cq->first = cq->last = NULL;

	while (NULL != cur) {
		chunk *next = cur->next;
		chunk_release(cur);
		cur = next;
	}

	cq->bytes_in = 0;
	cq->bytes_out = 0;
	cq->tempdir_idx = 0;
}

void chunkqueue_append_file_fd(chunkqueue *cq, buffer *fn, int fd, off_t offset, off_t len) {
    if (len > 0) {
        (chunkqueue_append_file_chunk(cq, fn, offset, len))->file.fd = fd;
    }
    else {
        close(fd);
    }
}

void chunkqueue_append_file(chunkqueue *cq, buffer *fn, off_t offset, off_t len) {
    if (len > 0) {
        chunkqueue_append_file_chunk(cq, fn, offset, len);
    }
}


static int chunkqueue_append_mem_extend_chunk(chunkqueue *cq, const char *mem, size_t len) {
	chunk *c = cq->last;
	if (0 == len) return 1;
	if (c != NULL && c->type == MEM_CHUNK
	    && buffer_string_space(c->mem) >= len) {
		buffer_append_string_len(c->mem, mem, len);
		cq->bytes_in += len;
		return 1;
	}
	return 0;
}


void chunkqueue_append_buffer(chunkqueue *cq, buffer *mem) {
	chunk *c;
	size_t len = buffer_string_length(mem);
	if (len < 256 && chunkqueue_append_mem_extend_chunk(cq, mem->ptr, len)) return;

	c = chunkqueue_append_mem_chunk(cq);
	cq->bytes_in += len;
	buffer_move(c->mem, mem);
}


void chunkqueue_append_mem(chunkqueue *cq, const char * mem, size_t len) {
	chunk *c;
	if (len < chunk_buf_sz && chunkqueue_append_mem_extend_chunk(cq, mem, len))
		return;

	c = chunkqueue_append_mem_chunk(cq);
	cq->bytes_in += len;
	buffer_copy_string_len(c->mem, mem, len);
}


void chunkqueue_append_mem_min(chunkqueue *cq, const char * mem, size_t len) {
	chunk *c;
	if (len < chunk_buf_sz && chunkqueue_append_mem_extend_chunk(cq, mem, len))
		return;

	c = chunk_init(len+1);
	chunkqueue_append_chunk(cq, c);
	cq->bytes_in += len;
	buffer_copy_string_len(c->mem, mem, len);
}


void chunkqueue_append_chunkqueue(chunkqueue *cq, chunkqueue *src) {
	if (src == NULL || NULL == src->first) return;

	if (NULL == cq->first) {
		cq->first = src->first;
	} else {
		cq->last->next = src->first;
	}
	cq->last = src->last;
	cq->bytes_in += (src->bytes_in - src->bytes_out);

	src->first = NULL;
	src->last = NULL;
	src->bytes_out = src->bytes_in;
}


__attribute_cold__
static void chunkqueue_buffer_open_resize(chunk *c, size_t sz) {
	chunk * const n = chunk_init((sz + 4095) & ~4095uL);
	buffer * const b = c->mem;
	c->mem = n->mem;
	n->mem = b;
	chunk_release(n);
}


buffer * chunkqueue_prepend_buffer_open_sz(chunkqueue *cq, size_t sz) {
	chunk * const c = chunkqueue_prepend_mem_chunk(cq);
	if (buffer_string_space(c->mem) < sz) {
		chunkqueue_buffer_open_resize(c, sz);
	}
	return c->mem;
}


buffer * chunkqueue_prepend_buffer_open(chunkqueue *cq) {
	chunk *c = chunkqueue_prepend_mem_chunk(cq);
	return c->mem;
}


void chunkqueue_prepend_buffer_commit(chunkqueue *cq) {
	cq->bytes_in += buffer_string_length(cq->first->mem);
}


buffer * chunkqueue_append_buffer_open_sz(chunkqueue *cq, size_t sz) {
	chunk * const c = chunkqueue_append_mem_chunk(cq);
	if (buffer_string_space(c->mem) < sz) {
		chunkqueue_buffer_open_resize(c, sz);
	}
	return c->mem;
}


buffer * chunkqueue_append_buffer_open(chunkqueue *cq) {
	chunk *c = chunkqueue_append_mem_chunk(cq);
	return c->mem;
}


void chunkqueue_append_buffer_commit(chunkqueue *cq) {
	cq->bytes_in += buffer_string_length(cq->last->mem);
}


static void chunkqueue_remove_empty_chunks(chunkqueue *cq);


char * chunkqueue_get_memory(chunkqueue *cq, size_t *len) {
	size_t sz = *len ? *len : (chunk_buf_sz >> 1);
	buffer *b;
	chunk *c = cq->last;
	if (NULL != c && MEM_CHUNK == c->type) {
		/* return pointer into existing buffer if large enough */
		size_t avail = buffer_string_space(c->mem);
		if (avail >= sz) {
			*len = avail;
			b = c->mem;
			return b->ptr + buffer_string_length(b);
		}
	}

	/* allocate new chunk */
	b = chunkqueue_append_buffer_open_sz(cq, sz);
	*len = buffer_string_space(b);
	return b->ptr;
}

void chunkqueue_use_memory(chunkqueue *cq, size_t len) {
	buffer *b;

	force_assert(NULL != cq);
	force_assert(NULL != cq->last && MEM_CHUNK == cq->last->type);
	b = cq->last->mem;

	if (len > 0) {
		buffer_commit(b, len);
		cq->bytes_in += len;
	} else if (buffer_string_is_empty(b)) {
		/* scan chunkqueue to remove empty last chunk
		 * (generally not expecting a deep queue) */
		chunkqueue_remove_empty_chunks(cq);
	}
}

void chunkqueue_set_tempdirs_default (array *tempdirs, unsigned int upload_temp_file_size) {
	chunkqueue_default_tempdirs = tempdirs;
	chunkqueue_default_tempfile_size
		= (0 == upload_temp_file_size)                ? DEFAULT_TEMPFILE_SIZE
		: (upload_temp_file_size > MAX_TEMPFILE_SIZE) ? MAX_TEMPFILE_SIZE
		                                              : upload_temp_file_size;
}

#if 0
void chunkqueue_set_tempdirs(chunkqueue *cq, array *tempdirs, unsigned int upload_temp_file_size) {
	force_assert(NULL != cq);
	cq->tempdirs = tempdirs;
	cq->upload_temp_file_size
		= (0 == upload_temp_file_size)                ? DEFAULT_TEMPFILE_SIZE
		: (upload_temp_file_size > MAX_TEMPFILE_SIZE) ? MAX_TEMPFILE_SIZE
		                                              : upload_temp_file_size;
	cq->tempdir_idx = 0;
}
#endif

void chunkqueue_steal(chunkqueue *dest, chunkqueue *src, off_t len) {
	while (len > 0) {
		chunk *c = src->first;
		off_t clen = 0, use;

		if (NULL == c) break;

		clen = chunk_remaining_length(c);
		if (0 == clen) {
			/* drop empty chunk */
			src->first = c->next;
			if (c == src->last) src->last = NULL;
			chunk_release(c);
			continue;
		}

		use = len >= clen ? clen : len;
		len -= use;

		if (use == clen) {
			/* move complete chunk */
			src->first = c->next;
			if (c == src->last) src->last = NULL;

			chunkqueue_append_chunk(dest, c);
			dest->bytes_in += use;
		} else {
			/* partial chunk with length "use" */

			switch (c->type) {
			case MEM_CHUNK:
				chunkqueue_append_mem(dest, c->mem->ptr + c->offset, use);
				break;
			case FILE_CHUNK:
				/* tempfile flag is in "last" chunk after the split */
				chunkqueue_append_file(dest, c->mem, c->file.start + c->offset, use);
				break;
			}

			c->offset += use;
			force_assert(0 == len);
		}

		src->bytes_out += use;
	}
}

static chunk *chunkqueue_get_append_tempfile(server *srv, chunkqueue *cq) {
	chunk *c;
	buffer *template = buffer_init_string("/var/tmp/lighttpd-upload-XXXXXX");
	int fd = -1;

	if (cq->tempdirs && cq->tempdirs->used) {
		/* we have several tempdirs, only if all of them fail we jump out */

		for (errno = EIO; cq->tempdir_idx < cq->tempdirs->used; ++cq->tempdir_idx) {
			data_string *ds = (data_string *)cq->tempdirs->data[cq->tempdir_idx];

			buffer_copy_buffer(template, ds->value);
			buffer_append_path_len(template, CONST_STR_LEN("lighttpd-upload-XXXXXX"));

		      #ifdef __COVERITY__
			/* POSIX-2008 requires mkstemp create file with 0600 perms */
			umask(0600);
		      #endif
			/* coverity[secure_temp : FALSE] */
			if (-1 != (fd = mkstemp(template->ptr))) break;
		}
	} else {
	      #ifdef __COVERITY__
		/* POSIX-2008 requires mkstemp create file with 0600 perms */
		umask(0600);
	      #endif
		/* coverity[secure_temp : FALSE] */
		fd = mkstemp(template->ptr);
	}

	if (fd < 0) {
		/* (report only the last error to mkstemp()
		 *  if multiple temp dirs attempted) */
		log_error_write(srv, __FILE__, __LINE__, "sbs",
				"opening temp-file failed:",
				template, strerror(errno));
		buffer_free(template);
		return NULL;
	}

	if (0 != fcntl(fd, F_SETFL, fcntl(fd, F_GETFL, 0) | O_APPEND)) {
		/* (should not happen; fd is regular file) */
		log_error_write(srv, __FILE__, __LINE__, "sbs",
				"fcntl():", template, strerror(errno));
		close(fd);
		buffer_free(template);
		return NULL;
	}
	fdevent_setfd_cloexec(fd);

	c = chunkqueue_append_file_chunk(cq, template, 0, 0);
	c->file.fd = fd;
	c->file.is_temp = 1;

	buffer_free(template);

	return c;
}

int chunkqueue_append_mem_to_tempfile(server *srv, chunkqueue *dest, const char *mem, size_t len) {
	chunk *dst_c;
	ssize_t written;

	do {
		/*
		 * if the last chunk is
		 * - smaller than dest->upload_temp_file_size
		 * - not read yet (offset == 0)
		 * -> append to it (so it might actually become larger than dest->upload_temp_file_size)
		 * otherwise
		 * -> create a new chunk
		 *
		 * */

		dst_c = dest->last;
		if (NULL != dst_c
			&& FILE_CHUNK == dst_c->type
			&& dst_c->file.is_temp
			&& dst_c->file.fd >= 0
			&& 0 == dst_c->offset) {
			/* ok, take the last chunk for our job */

			if (dst_c->file.length >= (off_t)dest->upload_temp_file_size) {
				/* the chunk is too large now, close it */
				int rc = close(dst_c->file.fd);
				dst_c->file.fd = -1;
				if (0 != rc) {
					log_error_write(srv, __FILE__, __LINE__, "sbss",
						"close() temp-file", dst_c->mem, "failed:",
						strerror(errno));
					return -1;
				}
				dst_c = NULL;
			}
		} else {
			dst_c = NULL;
		}

		if (NULL == dst_c && NULL == (dst_c = chunkqueue_get_append_tempfile(srv, dest))) {
			return -1;
		}
	      #ifdef __COVERITY__
		if (dst_c->file.fd < 0) return -1;
	      #endif

		/* (dst_c->file.fd >= 0) */
		/* coverity[negative_returns : FALSE] */
		written = write(dst_c->file.fd, mem, len);

		if ((size_t) written == len) {
			dst_c->file.length += len;
			dest->bytes_in += len;

			return 0;
		} else if (written >= 0) {
			/*(assume EINTR if partial write and retry write();
			 * retry write() might fail with ENOSPC if no more space on volume)*/
			dest->bytes_in += written;
			mem += written;
			len -= (size_t)written;
			dst_c->file.length += (size_t)written;
			/* continue; retry */
		} else if (errno == EINTR) {
			/* continue; retry */
		} else {
			int retry = (errno == ENOSPC && dest->tempdirs && ++dest->tempdir_idx < dest->tempdirs->used);
			if (!retry) {
				log_error_write(srv, __FILE__, __LINE__, "sbs",
						"write() temp-file", dst_c->mem, "failed:",
						strerror(errno));
			}

			if (0 == chunk_remaining_length(dst_c)) {
				/*(remove empty chunk and unlink tempfile)*/
				chunkqueue_remove_empty_chunks(dest);
			} else {/*(close tempfile; avoid later attempts to append)*/
				int rc = close(dst_c->file.fd);
				dst_c->file.fd = -1;
				if (0 != rc) {
					log_error_write(srv, __FILE__, __LINE__, "sbss",
						"close() temp-file", dst_c->mem, "failed:",
						strerror(errno));
					return -1;
				}
			}
			if (!retry) break; /* return -1; */

			/* continue; retry */
		}

	} while (dst_c);

	return -1;
}

int chunkqueue_steal_with_tempfiles(server *srv, chunkqueue *dest, chunkqueue *src, off_t len) {
	while (len > 0) {
		chunk *c = src->first;
		off_t clen = 0, use;

		if (NULL == c) break;

		clen = chunk_remaining_length(c);
		if (0 == clen) {
			/* drop empty chunk */
			src->first = c->next;
			if (c == src->last) src->last = NULL;
			chunk_release(c);
			continue;
		}

		use = (len >= clen) ? clen : len;
		len -= use;

		switch (c->type) {
		case FILE_CHUNK:
			if (use == clen) {
				/* move complete chunk */
				src->first = c->next;
				if (c == src->last) src->last = NULL;
				chunkqueue_append_chunk(dest, c);
				dest->bytes_in += use;
			} else {
				/* partial chunk with length "use" */
				/* tempfile flag is in "last" chunk after the split */
				chunkqueue_append_file(dest, c->mem, c->file.start + c->offset, use);

				c->offset += use;
				force_assert(0 == len);
			}
			break;

		case MEM_CHUNK:
			/* store "use" bytes from memory chunk in tempfile */
			if (0 != chunkqueue_append_mem_to_tempfile(srv, dest, c->mem->ptr + c->offset, use)) {
				return -1;
			}

			if (use == clen) {
				/* finished chunk */
				src->first = c->next;
				if (c == src->last) src->last = NULL;
				chunk_release(c);
			} else {
				/* partial chunk */
				c->offset += use;
				force_assert(0 == len);
			}
			break;
		}

		src->bytes_out += use;
	}

	return 0;
}

off_t chunkqueue_length(chunkqueue *cq) {
	off_t len = 0;
	chunk *c;

	for (c = cq->first; c; c = c->next) {
		len += chunk_remaining_length(c);
	}

	return len;
}

void chunkqueue_mark_written(chunkqueue *cq, off_t len) {
	off_t written = len;
	chunk *c;
	force_assert(len >= 0);

	for (c = cq->first; NULL != c; c = cq->first) {
		off_t c_len = chunk_remaining_length(c);

		if (0 == written && 0 != c_len) break; /* no more finished chunks */

		if (written >= c_len) { /* chunk got finished */
			c->offset += c_len;
			written -= c_len;

			cq->first = c->next;
			if (c == cq->last) cq->last = NULL;
			chunk_release(c);
		} else { /* partial chunk */
			c->offset += written;
			written = 0;
			break; /* chunk not finished */
		}
	}

	force_assert(0 == written);
	cq->bytes_out += len;
}

void chunkqueue_remove_finished_chunks(chunkqueue *cq) {
	chunk *c;

	for (c = cq->first; c; c = cq->first) {
		if (0 != chunk_remaining_length(c)) break; /* not finished yet */

		cq->first = c->next;
		if (c == cq->last) cq->last = NULL;
		chunk_release(c);
	}
}

static void chunkqueue_remove_empty_chunks(chunkqueue *cq) {
	chunk *c;
	chunkqueue_remove_finished_chunks(cq);
	if (chunkqueue_is_empty(cq)) return;

	for (c = cq->first; c && c->next; c = c->next) {
		if (0 == chunk_remaining_length(c->next)) {
			chunk *empty = c->next;
			c->next = empty->next;
			if (empty == cq->last) cq->last = c;
			chunk_release(empty);
		}
	}
}

int chunkqueue_open_file_chunk(server *srv, chunkqueue *cq) {
	chunk* const c = cq->first;
	off_t offset, toSend;
	struct stat st;

	force_assert(NULL != c);
	force_assert(FILE_CHUNK == c->type);
	force_assert(c->offset >= 0 && c->offset <= c->file.length);

	offset = c->file.start + c->offset;
	toSend = c->file.length - c->offset;

	if (-1 == c->file.fd) {
		/* (permit symlinks; should already have been checked.  However, TOC-TOU remains) */
		if (-1 == (c->file.fd = fdevent_open_cloexec(c->mem->ptr, 1, O_RDONLY, 0))) {
			log_error_write(srv, __FILE__, __LINE__, "ssb", "open failed:", strerror(errno), c->mem);
			return -1;
		}
	}

	/*(skip file size checks if file is temp file created by lighttpd)*/
	if (c->file.is_temp) return 0;

	if (-1 == fstat(c->file.fd, &st)) {
		log_error_write(srv, __FILE__, __LINE__, "ss", "fstat failed:", strerror(errno));
		return -1;
	}

	if (offset > st.st_size || toSend > st.st_size || offset > st.st_size - toSend) {
		log_error_write(srv, __FILE__, __LINE__, "sb", "file shrunk:", c->mem);
		return -1;
	}

	return 0;
}