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-rw-r--r--src/scrotty.c91
1 files changed, 77 insertions, 14 deletions
diff --git a/src/scrotty.c b/src/scrotty.c
index 6552abf..850e448 100644
--- a/src/scrotty.c
+++ b/src/scrotty.c
@@ -37,7 +37,17 @@
#endif
+
#define LIST_0_9(P) P"0\n", P"1\n", P"2\n", P"3\n", P"4\n", P"5\n", P"6\n", P"7\n", P"8\n", P"9\n"
+
+/**
+ * [0, 255]-integer-to-text convertion lookup table for faster conversion from
+ * raw framebuffer data to the PNM format. The values have a whitespace at the
+ * end for even faster conversion.
+ * Lines should not be longer than 70 (although most programs will probably
+ * work even if there are longer lines), therefore the selected whitespace
+ * is LF (new line).
+ */
static const char* inttable[] =
{
LIST_0_9(""), LIST_0_9("1"), LIST_0_9("2"), LIST_0_9("3"), LIST_0_9("4"),
@@ -51,6 +61,14 @@ static const char* inttable[] =
};
+/**
+ * Create an PNM-file that is sent to `convert` for convertion to a compressed format
+ *
+ * @param fbname The framebuffer device
+ * @param fbno The number of the framebuffer
+ * @param fd The file descriptor connected to `convert`'s stdin
+ * @return Zero on success, -1 on error
+ */
static int save_pnm(const char* fbpath, int fbno, int fd)
{
char buf[PATH_MAX];
@@ -58,40 +76,55 @@ static int save_pnm(const char* fbpath, int fbno, int fd)
int saved_errno, sizefd, fbfd, r, g, b;
ssize_t got, off;
+ /* Open the file with the framebuffer's dimensions. */
sprintf(buf, SYSDIR "/class/graphics/fb%i/virtual_size", fbno);
if (sizefd = open(buf, O_RDONLY), sizefd < 0)
return -1;
+ /* Get the dimensions of the framebuffer. */
if (got = read(sizefd, buf, sizeof(buf) / sizeof(char) - 1), got < 0)
return saved_errno = errno, close(sizefd), errno = saved_errno, -1;
close(sizefd);
+ /* The read content is formated as `%{1},%{2}\n`, we want it do be `%{1} %{2}\n\0`. */
buf[got] = '\0';
*strchr(buf, ',') = ' ';
- fbfd = open(fbpath, O_RDONLY);
- if (fbfd < 0)
+ /* Open the framebuffer device for reading. */
+ if (fbfd = open(fbpath, O_RDONLY), fbfd < 0)
return -1;
-
+
+ /* Create a FILE*, for writing, for the image file. */
file = fdopen(fd, "w");
if (file == NULL)
return saved_errno = errno, close(fbfd), errno = saved_errno, -1;
+
+ /* The PNM image should begin with `P3\n%{width} %{height}\n%{colour max=255}\n`.
+ ('\n' and ' ' can be exchanged at will.) */
fprintf(file, "P3\n%s255\n", buf);
+ /* Convert raw framebuffer data into an PNM image. */
for (off = 0;;)
{
+ /* Read data from the framebuffer, we may have up to 3 bytes buffered. */
got = read(fbfd, buf + off, sizeof(buf) - off * sizeof(char));
if (got < 0)
return saved_errno = errno, fclose(file), close(fbfd), errno = saved_errno, -1;
if (got += off, got == 0)
break;
+ /* Convert read pixels. */
for (off = 0; off < got; off += 4)
{
+ /* A pixel in the framebuffer is formatted as `%{blue}%{green}%{red}%{x}` in binary. */
r = buf[off + 2] & 255;
g = buf[off + 1] & 255;
b = buf[off + 0] & 255;
+ /* A pixel in the PNM image is formatted as `%{red} %{green} %{blue} ` in text. */
fprintf(file, "%s%s%s", inttable[r], inttable[g], inttable[b]);
}
+
+ /* If we read a whole number of pixels, reset the buffer, otherwise,
+ move the unconverted bytes to the beginning of the buffer. */
if (off != got)
{
off -= 4;
@@ -102,6 +135,7 @@ static int save_pnm(const char* fbpath, int fbno, int fd)
off = 0;
}
+ /* Close files and return successfully. */
fflush(file);
fclose(file);
close(fbfd);
@@ -109,51 +143,76 @@ static int save_pnm(const char* fbpath, int fbno, int fd)
}
+/**
+ * Create an image of a framebuffer
+ *
+ * @param fbname The framebuffer device
+ * @param imgname The pathname of the output image
+ * @param fbno The number of the framebuffer
+ * @param execname `argv[0]` from `main`
+ * @return Zero on success, -1 on error
+ */
static int save(const char* fbpath, const char* imgpath, int fbno, const char* execname)
{
int pipe_rw[2];
pid_t pid, reaped;
int saved_errno, status;
+ /* Create a pipe that for sending data into the `convert` program. */
if (pipe(pipe_rw) < 0)
return -1;
-
+
+ /* Fork the process, the child will exec. `convert`. */
if (pid = fork(), pid == -1)
return saved_errno = errno, close(pipe_rw[0]), close(pipe_rw[1]), errno = saved_errno, -1;
-
+
+ /* Child process: */
if (pid == 0)
{
+ /* Close the write-end of the pipe. */
close(pipe_rw[1]);
+ /* Turn the read-end of the into stdin. */
if (pipe_rw[0] != STDIN_FILENO)
{
close(STDIN_FILENO);
dup2(pipe_rw[0], STDIN_FILENO);
close(pipe_rw[0]);
}
+ /* Exec. `convert` to convert the PNM-image we create to a compressed image. */
execlp("convert", "convert", DEVDIR "/stdin", imgpath, NULL);
perror(execname);
exit(1);
}
+ /* Parent process: */
+
+ /* Close the read-end of the pipe. */
close(pipe_rw[0]);
+ /* Create a PNM-image of the framebuffer. */
if (save_pnm(fbpath, fbno, pipe_rw[1]) < 0)
return saved_errno = errno, close(pipe_rw[1]), errno = saved_errno, -1;
+ /* Close the write-end of the pipe. */
close(pipe_rw[1]);
-
- reaped = 0;
- while (reaped != pid)
- {
- reaped = waitpid(pid, &status, 0);
- if (reaped < 0)
- return -1;
- }
-
+
+ /* Wait for `convert` to exit. */
+ for (reaped = 0; reaped != pid;)
+ if (reaped = waitpid(pid, &status, 0), reaped < 0)
+ return -1;
+
+ /* Return successfully if and only if `convert` did. */
return status == 0 ? 0 : -1;
}
+/**
+ * Take a screenshow of all framebuffers
+ *
+ * @param argc The number of elements in `argv`
+ * @param argv Command line arguments
+ * @return Zero on and only on success
+ */
int main(int argc, char* argv[])
{
char fbpath[PATH_MAX];
@@ -162,12 +221,15 @@ int main(int argc, char* argv[])
(void) argc;
+ /* The a screenshot of each framebuffer. */
for (fbno = 0;; fbno++)
{
+ /* Get pathname for framebuffer, and stop if we have read all existing ones. */
sprintf(fbpath, DEVDIR "/fb%i", fbno);
if (access(fbpath, F_OK))
break;
+ /* Get output pathname. */
sprintf(imgpath, "fb%i.png", fbno);
if (access(imgpath, F_OK) == 0)
for (i = 2;; i++)
@@ -177,6 +239,7 @@ int main(int argc, char* argv[])
break;
}
+ /* Take a screenshot of the current framebuffer. */
if (save(fbpath, imgpath, fbno, *argv) < 0)
return perror(*argv), 1;
fprintf(stderr, "Saved framebuffer %i to %s\n", fbno, imgpath);