line editing: add an option to emit ESC [ 6 n and use results

This makes line editing able to recognize case when
cursor was not at the beginning of the line. It may also
be adapted later to find out display size (serial line users
would love it).

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 10 insertions, 3 deletions

diff --git a/include/libbb.h b/include/libbb.h
index bae7efb00..788140d14 100644
--- a/include/libbb.h
+++ b/include/libbb.h
@@ -962,16 +962,23 @@ enum {
         KEYCODE_FUN11    = -22,
         KEYCODE_FUN12    = -23,
 #endif
-        /* How long the longest ESC sequence we know? */
-        KEYCODE_BUFFER_SIZE = 4
+        KEYCODE_CURSOR_POS = -0x100,
+        /* How long is the longest ESC sequence we know?
+         * We want it big enough to be able to contain
+         * cursor position sequence "ESC [ 9999 ; 9999 R"
+         */
+        KEYCODE_BUFFER_SIZE = 16
 };
 /* Note: fd may be in blocking or non-blocking mode, both make sense.
  * For one, less uses non-blocking mode.
  * Only the first read syscall inside read_key may block indefinitely
  * (unless fd is in non-blocking mode),
  * subsequent reads will time out after a few milliseconds.
+ * Return of -1 means EOF or error (errno == 0 on EOF).
+ * buffer[0] is used as a counter of buffered chars and must be 0
+ * on first call.
  */
-int read_key(int fd, smalluint *nbuffered, char *buffer) FAST_FUNC;
+int64_t read_key(int fd, char *buffer) FAST_FUNC;
 
 
 /* Networking */