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	blind-reverse.c - blind - suckless command-line video editing utility
	git clone git://git.suckless.org/blind
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	blind-reverse.c (2377B)
	---
	1 /* See LICENSE file for copyright and license details. */
	2 #include "common.h"
	3
	4 USAGE("[-i] file")
	5
	6 static void
	7 to_stdout(struct stream *stream)
	8 {
	9 size_t ptr, end, n;
	10 char buf[BUFSIZ];
	11
	12 while (stream->frames--) {
	13 ptr = stream->frames * stream->frame_size + stream->head…
	14 end = ptr + stream->frame_size;
	15 while (ptr < end) {
	16 if (!(n = epread(stream->fd, buf, MIN(sizeof(buf…
	17 (off_t)ptr, stream->file)))
	18 eprintf("%s: file is shorter than expect…
	19 ptr += n;
	20 ewriteall(STDOUT_FILENO, buf, n, "<stdout>");
	21 }
	22 }
	23 }
	24
	25 static void
	26 elseek_set(int fd, off_t offset, const char *fname)
	27 {
	28 off_t r = elseek(fd, offset, SEEK_SET, fname);
	29 if (r != offset)
	30 eprintf("%s: file is shorter than expected\n", fname);
	31 }
	32
	33 static void
	34 epread_frame(struct stream stream, char buf, off_t off)
	35 {
	36 stream->ptr = stream->xptr = 0;
	37 elseek_set(stream->fd, off, stream->file);
	38 eread_frame(stream, buf);
	39 }
	40
	41 static void
	42 epwrite_frame(struct stream stream, char buf, off_t off)
	43 {
	44 elseek_set(stream->fd, off, stream->file);
	45 ewriteall(stream->fd, buf, stream->frame_size, stream->file);
	46 }
	47
	48 static void
	49 in_place(struct stream *stream)
	50 {
	51 size_t f, fm = stream->frames - 1;
	52 off_t pa, pb;
	53 char bufa, bufb;
	54
	55 bufa = emalloc(stream->frame_size);
	56 bufb = emalloc(stream->frame_size);
	57
	58 for (f = 0; f < stream->frames >> 1; f++) {
	59 pa = (off_t)f * (off_t)(stream->frame_size) + (of…
	60 pb = (off_t)(fm - f) * (off_t)(stream->frame_size) + (of…
	61
	62 epread_frame(stream, bufa, pa);
	63 epread_frame(stream, bufb, pb);
	64
	65 epwrite_frame(stream, bufa, pb);
	66 epwrite_frame(stream, bufb, pa);
	67 }
	68
	69 free(bufa);
	70 free(bufb);
	71 }
	72
	73 int
	74 main(int argc, char *argv[])
	75 {
	76 struct stream stream;
	77 int inplace = 0;
	78
	79 ARGBEGIN {
	80 case 'i':
	81 inplace = 1;
	82 break;
	83 default:
	84 usage();
	85 } ARGEND;
	86
	87 if (argc != 1)
	88 usage();
	89
	90 stream.file = argv[0];
	91 stream.fd = eopen(stream.file, inplace ? O_RDWR : O_RDONLY);
	92 einit_stream(&stream);
	93 if (!inplace) {
	94 fprint_stream_head(stdout, &stream);
	95 efflush(stdout, "<stdout>");
	96 }
	97 echeck_dimensions(&stream, WIDTH \| HEIGHT, NULL);
	98 if (stream.frames * stream.frame_size > (size_t)SSIZE_MAX - stre…
	99 eprintf("%s: video is too large\n", stream.file);
	100
	101 fadvise_random(stream.fd, 0, 0);
	102
	103 (inplace ? in_place : to_stdout)(&stream);
	104 close(stream.fd);
	105 return 0;
	106 }