[PATCH 15/16] vc_screen: extract vcs_read_buf_header

Jiri Slaby
2020-08-18T08:57:52Z

The attribute header handling is terrible in vcs_read_buf. Separate it
to a new function and simply do memmove (of up to 4 bytes) to the start
of the con_buf -- if user seeked.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
drivers/tty/vt/vc_screen.c | 31 ++++++++++++++++++-------------
1 file changed, 18 insertions(+), 13 deletions(-)

diff --git a/drivers/tty/vt/vc_screen.c b/drivers/tty/vt/vc_screen.c
index c178a1611223..9d68c6b36ddf 100644
--- a/drivers/tty/vt/vc_screen.c
+++ b/drivers/tty/vt/vc_screen.c
@@ -297,6 +297,22 @@ static void vcs_read_buf_noattr(const struct vc_data *vc, char *con_buf,
}
}

+static unsigned int vcs_read_buf_header(const struct vc_data *vc, char *con_buf,
+ unsigned int pos, unsigned int count)
+{
+ count = min(HEADER_SIZE - pos, count);
+
+ /* clamp header values if they don't fit */
+ con_buf[0] = min(vc->vc_rows, 0xFFu);
+ con_buf[1] = min(vc->vc_cols, 0xFFu);
+ getconsxy(vc, con_buf + 2);
+
+ if (pos)
+ memmove(con_buf, con_buf + pos, count);
+
+ return count;
+}
+
static unsigned int vcs_read_buf(const struct vc_data *vc, char *con_buf,
unsigned int pos, unsigned int count, bool viewed,
unsigned int *skip)
@@ -306,22 +322,11 @@ static unsigned int vcs_read_buf(const struct vc_data *vc, char *con_buf,
unsigned int filled = count;

if (pos < HEADER_SIZE) {
- /* clamp header values if they don't fit */
- con_buf[0] = min(vc->vc_rows, 0xFFu);
- con_buf[1] = min(vc->vc_cols, 0xFFu);
- getconsxy(vc, con_buf + 2);
-
- *skip += pos;
- count += pos;
- if (count > CON_BUF_SIZE) {
- count = CON_BUF_SIZE;
- filled = count - pos;
- }
+ count -= vcs_read_buf_header(vc, con_buf, pos, count);

- /* Advance state pointers and move on. */
- count -= min(HEADER_SIZE, count);
pos = HEADER_SIZE;
con_buf += HEADER_SIZE;
+
/* If count >= 0, then pos is even... */
} else if (pos & 1) {
/*
--
2.28.0