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	Add blind-peek-head - blind - suckless command-line video editing utility
	git clone git://git.suckless.org/blind
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	---
	commit 23100155b5d0ecbf95a8d1c4fa8d02557b69de94
	parent 6ca85b3362761f24f8913314bf5cfdfa35241fef
	Author: Mattias Andrée <[email protected]>
	Date: Wed, 23 Aug 2017 00:39:26 +0200

	Add blind-peek-head

	Signed-off-by: Mattias Andrée <[email protected]>

	Diffstat:
	M Makefile \| 3 ++-
	M README \| 3 +++
	M config.mk \| 8 ++++----
	A man/blind-peek-head.1 \| 28 ++++++++++++++++++++++++++++
	M man/blind-read-head.1 \| 1 +
	M man/blind.7 \| 3 +++
	A src/blind-peek-head.c \| 152 +++++++++++++++++++++++++++++…

	7 files changed, 193 insertions(+), 5 deletions(-)
	---
	diff --git a/Makefile b/Makefile
	@@ -60,8 +60,9 @@ BIN =\
	blind-multiply-matrices\
	blind-next-frame\
	blind-norm\
	- blind-quaternion-product\
	+ blind-peek-head\
	blind-premultiply\
	+ blind-quaternion-product\
	blind-radial-gradient\
	blind-read-head\
	blind-rectangle-tessellation\
	diff --git a/README b/README
	@@ -177,6 +177,9 @@ UTILITIES
	blind-norm(1)
	Calculate the norm of colours in a video

	+ blind-peek-head
	+ Peeks the head from a video
	+
	blind-premultiply(1)
	Premultiply the alpha channel of a video

	diff --git a/config.mk b/config.mk
	@@ -13,9 +13,9 @@ KORN_SHELL = bash
	# Commands
	LN = ln -s

	-# You may want to remove -DHAVE_PRCTL, -DHAVE_EPOLL, and
	-# -DHAVE_SENDFILE from CPPFLAGS if you are not using Linux.
	+# You may want to remove -DHAVE_PRCTL, -DHAVE_EPOLL, -DHAVE_TEE,
	+# and -DHAVE_SENDFILE from CPPFLAGS if you are not using Linux.
	CFLAGS = -std=c11 -Wall -pedantic -O2
	-CPPFLAGS = -D_DEFAULT_SOURCE -D_BSD_SOURCE -D_XOPEN_SOURCE=700 -D_FILE_OFFSET_…
	- -DHAVE_PRCTL -DHAVE_EPOLL -DHAVE_SENDFILE
	+CPPFLAGS = -D_DEFAULT_SOURCE -D_BSD_SOURCE -D_XOPEN_SOURCE=700 -D_GNU_SOURCE \
	+ -D_FILE_OFFSET_BITS=64 -DHAVE_PRCTL -DHAVE_EPOLL -DHAVE_TEE -DHAVE_…
	LDFLAGS = -lm -s
	diff --git a/man/blind-peek-head.1 b/man/blind-peek-head.1
	@@ -0,0 +1,28 @@
	+.TH BLIND-PEEK-HEAD 1 blind
	+.SH NAME
	+blind-peek-head - Peeks the head from a video
	+.SH SYNOPSIS
	+.B blind-peek-head
	+.SH DESCRIPTION
	+.B blind-peek-head
	+peeks the head a video from stdin, and
	+prints it, without the magic number, to stdout.
	+The output will contain: the number of frames,
	+<space>, the width, <space>, the height, <space>,
	+and the pixel format. The output is text, and
	+thus ends with a <newline>. The state of stdin
	+will remain unchanged.
	+.SH NOTES
	+.B blind-peek-head
	+requires that stdin is a socket, a regular file,
	+or a (on Linux only) a pipe. Direct pipes and
	+datagram sockets are supported but require that
	+the entire head must be written in one write.
	+.SH SEE ALSO
	+.BR blind (7),
	+.BR blind-read-head (1),
	+.BR blind-write-head (1),
	+.BR blind-next-frame (1)
	+.SH AUTHORS
	+Mattias Andrée
	+.RI < [email protected] >
	diff --git a/man/blind-read-head.1 b/man/blind-read-head.1
	@@ -18,6 +18,7 @@ can be used to get the first, and
	any following, frame from stdin.
	.SH SEE ALSO
	.BR blind (7),
	+.BR blind-peek-head (1),
	.BR blind-write-head (1),
	.BR blind-next-frame (1)
	.SH AUTHORS
	diff --git a/man/blind.7 b/man/blind.7
	@@ -195,6 +195,9 @@ Extracts the next frame from a video
	.BR blind-norm (1)
	Calculate the norm of colours in a video
	.TP
	+.BR blind-peek-head (1)
	+Peeks the head from a video
	+.TP
	.BR blind-premultiply (1)
	Premultiply the alpha channel of a video
	.TP
	diff --git a/src/blind-peek-head.c b/src/blind-peek-head.c
	@@ -0,0 +1,152 @@
	+/* See LICENSE file for copyright and license details. */
	+#include "common.h"
	+
	+USAGE("")
	+
	+static ssize_t
	+peek_socket(char *buf, size_t n)
	+{
	+ ssize_t r = recv(STDIN_FILENO, buf, n, MSG_PEEK);
	+ if (r < 0 && errno != ENOTSOCK)
	+ eprintf("recv <stdin>:");
	+ return r;
	+}
	+
	+static ssize_t
	+peek_regular(char *buf, size_t n)
	+{
	+ ssize_t r;
	+ off_t pos = lseek(STDIN_FILENO, 0, SEEK_CUR);
	+ if (pos < 0) {
	+ if (errno != ESPIPE)
	+ eprintf("lseek <stdin>:");
	+ return -1;
	+ }
	+ r = pread(STDIN_FILENO, buf, n, pos);
	+ if (r < 0 && errno != ESPIPE)
	+ eprintf("pread <stdin>:");
	+ return r;
	+}
	+
	+#if defined(HAVE_TEE)
	+static ssize_t
	+peek_pipe(char *buf, size_t n)
	+{
	+ int rw[2];
	+ ssize_t m;
	+ size_t p;
	+ if (pipe(rw))
	+ eprintf("pipe");
	+ m = tee(STDIN_FILENO, rw[1], n, 0);
	+ if (m < 0) {
	+ if (errno != EINVAL)
	+ eprintf("tee <stdin>:");
	+ return -1;
	+ }
	+ close(rw[1]);
	+ p = ereadall(rw[0], buf, (size_t)m, "<pipe>");
	+ close(rw[0]);
	+ return (ssize_t)p;
	+}
	+#endif
	+
	+static size_t
	+peek(char *buf, size_t n)
	+{
	+ static int method = 0;
	+ ssize_t r;
	+ switch (method) {
	+ case 0:
	+ if ((r = peek_socket(buf, n)) >= 0)
	+ return (size_t)r;
	+ method++;
	+ /* fall-through */
	+ case 1:
	+ if ((r = peek_regular(buf, n)) >= 0)
	+ return (size_t)r;
	+ method++;
	+#if defined(HAVE_TEE)
	+ /* fall-through */
	+ default:
	+ if ((r = peek_pipe(buf, n)) >= 0)
	+ return (size_t)r;
	+ eprintf("can only peek pipes, sockets, and regular files\n");
	+#else
	+ eprintf("can only peek sockets and regular files\n");
	+#endif
	+ }
	+}
	+
	+int
	+main(int argc, char *argv[])
	+{
	+ char buf[STREAM_HEAD_MAX], *p;
	+ char magic[] = {'\0', 'u', 'i', 'v', 'f'};
	+ size_t i, len = 0, last_len;
	+#if defined(HAVE_EPOLL)
	+ struct epoll_event ev;
	+ int epfd, epr = 0;
	+#endif
	+
	+ UNOFLAGS(argc);
	+
	+#if defined(HAVE_EPOLL)
	+ epfd = epoll_create1(0);
	+ if (epfd < 0)
	+ eprintf("epoll_create1:");
	+
	+ memset(&ev, 0, sizeof(ev));
	+ ev.events = EPOLLIN \| EPOLLRDHUP \| EPOLLET;
	+ if (epoll_ctl(epfd, EPOLL_CTL_ADD, STDIN_FILENO, &ev))
	+ eprintf("epoll_ctl EPOLL_CTL_ADD:");
	+
	+ do {
	+ last_len = len;
	+ len = peek(buf, sizeof(buf));
	+ p = memchr(buf, '\n', len);
	+ if (p && len >= (size_t)(++p - buf) + ELEMENTSOF(magic))
	+ goto ready;
	+ } while (len > last_len && (epr = epoll_wait(epfd, &ev, 1, -1)) >= 0);
	+ if (epr < 0)
	+ eprintf("epoll_wait:");
	+#else
	+ goto beginning;
	+ do {
	+ usleep(50000);
	+ beginning:
	+ last_len = len;
	+ len = peek(buf, n);
	+ p = memchr(buf, '\n', len);
	+ if (p && len >= (size_t)(++p - buf) + ELEMENTSOF(magic))
	+ goto ready;
	+ } while (len > last_len);
	+#endif
	+ eprintf("could not read entire head\n");
	+
	+ready:
	+ len = (size_t)(p - buf);
	+ for (i = 0; i < ELEMENTSOF(magic); i++)
	+ if (p[i] != magic[i])
	+ goto bad_format;
	+ p = buf;
	+ for (i = 0; i < 3; i++) {
	+ if (!isdigit(*p))
	+ goto bad_format;
	+ while (isdigit(*p)) p++;
	+ if (*p++ != ' ')
	+ goto bad_format;
	+ }
	+ while (isalnum(p) \|\| p == ' ') {
	+ if (p[0] == ' ' && p[-1] == ' ')
	+ goto bad_format;
	+ p++;
	+ }
	+ if (p[-1] == ' ' \|\| p[0] != '\n')
	+ goto bad_format;
	+
	+ ewriteall(STDOUT_FILENO, buf, len, "<stdout>");
	+ return 0;
	+
	+bad_format:
	+ eprintf("<stdin>: file format not supported\n");
	+}