[PATCH rtems6 v2] libmisc/shell: Fix timeout getting terminal size

dufault at hda.com dufault at hda.com
Wed Jan 24 09:01:33 UTC 2024


From: Peter Dufault <dufault at hda.com>

- Fix detection of timeout in rtems_shell_term_wait_for().

- Use the "termios" VTIME inter-character timeout.
  The previous version depends on the BSP clock tick and can be long.

- Add debugging regarding terminal size sequences.

Updates #4763
---
 cpukit/libmisc/shell/shell.c | 103 +++++++++++++++++++++++++------------------
 1 file changed, 59 insertions(+), 44 deletions(-)

diff --git a/cpukit/libmisc/shell/shell.c b/cpukit/libmisc/shell/shell.c
index 9cefc80..6a9e11e 100644
--- a/cpukit/libmisc/shell/shell.c
+++ b/cpukit/libmisc/shell/shell.c
@@ -40,14 +40,19 @@
 #include <assert.h>
 
 #define SHELL_STD_DEBUG 0
+#define SHELL_WINSIZE_DEBUG 0
 
-#if SHELL_STD_DEBUG
 #include <rtems/bspIo.h>
+#define shell_std_debug_(EN, ...)                                                \
+  do {                                                                           \
+    if (EN) { printk("shell[%08x]: ", rtems_task_self()); printk(__VA_ARGS__); } \
+  } while (0)
+
 #define shell_std_debug(...) \
-  do { printk("shell[%08x]: ", rtems_task_self()); printk(__VA_ARGS__); } while (0)
-#else
-#define shell_std_debug(...)
-#endif
+  shell_std_debug_(SHELL_STD_DEBUG, __VA_ARGS__)
+
+#define shell_winsize_debug(...) \
+  shell_std_debug_(SHELL_WINSIZE_DEBUG, __VA_ARGS__)
 
 #define SHELL_MAGIC rtems_build_name('S', 'E', 'N', 'V')
 
@@ -805,28 +810,35 @@ void rtems_shell_print_env(
 }
 #endif
 
+/* Window size detection knob.
+ * VTIME timeout in .1 seconds.  No way to set without editing.
+ */
+static const int rtems_shell_winsize_vtime = 1;
+
 /*
  * Wait for the string to return or timeout.
  */
-static bool rtems_shell_term_wait_for(const int fd, const char* str, const int timeout)
+static bool rtems_shell_term_wait_for(const int fd, const char* str)
 {
-  int msec = timeout;
   int i = 0;
-  while (msec-- > 0 && str[i] != '\0') {
+  while (str[i] != '\0') {
     char ch[2];
-    if (read(fd, &ch[0], 1) == 1) {
-      fflush(stdout);
+    ssize_t n;
+    if ((n = read(fd, &ch[0], 1)) == 1) {
       if (ch[0] != str[i++]) {
+        shell_winsize_debug("Wrong char at char %d.\n", i);
         return false;
       }
-      msec = timeout;
     } else {
-      usleep(1000);
+      shell_winsize_debug(
+        "%s reading char %d.\n",
+        (n == 0) ? "Timeout" : "Error", i
+      );
+      return false;
     }
   }
-  if (msec == 0) {
-    return false;
-  }
+
+  shell_winsize_debug("Matched string.\n");
   return true;
 }
 
@@ -836,41 +848,43 @@ static bool rtems_shell_term_wait_for(const int fd, const char* str, const int t
 static int rtems_shell_term_buffer_until(const int fd,
                                          char* buf,
                                          const int size,
-                                         const char* end,
-                                         const int timeout)
+                                         const char* end)
 {
-  int msec = timeout;
   int i = 0;
   int e = 0;
   memset(&buf[0], 0, size);
-  while (msec-- > 0 && i < size && end[e] != '\0') {
+  while (i < size && end[e] != '\0') {
     char ch[2];
-    if (read(fd, &ch[0], 1) == 1) {
-      fflush(stdout);
+    ssize_t n;
+    if ( (n = read(fd, &ch[0], 1)) == 1) {
       buf[i++] = ch[0];
       if (ch[0] == end[e]) {
         e++;
       } else {
+        shell_winsize_debug("Reset search for end string.\n");
         e = 0;
       }
-      msec = timeout;
     } else {
-      usleep(1000);
+      /* There is an error or timeout. */
+      shell_winsize_debug(
+         "%s looking for end string \"%s\". Read \"%s\".\n",
+         (n == 0) ? "Timeout" : "Error",
+         end, buf
+      );
+      return -1;
     }
   }
-  if (msec == 0 || end[e] != '\0') {
-    return -1;
-  }
-  i -= e;
+  i -= e;   /* Toss away the matched end. */
   if (i < size) {
     buf[i] = '\0';
   }
+  shell_winsize_debug("Found end string \"%s\".\n", end);
   return i;
 }
 
 /*
- * Determine if the terminal has the row and column values
- * swapped
+ * Determine if this is a version of the "tmux" terminal emulator with
+ * the row and column values swapped
  *
  * https://github.com/tmux/tmux/issues/3457
  *
@@ -878,19 +892,19 @@ static int rtems_shell_term_buffer_until(const int fd,
  * in the time it takes to get the fix into code so see if tmux is
  * running and which version and work around the bug.
  *
- * The terminal device needs to have VMIN=0, and VTIME=0
+ * The terminal device needs to have VMIN=0, and VTIME set to the
+ * desired timeout in .1 seconds.
  */
-static bool rtems_shell_term_row_column_swapped(const int fd, const int timeout) {
+static bool rtems_shell_term_row_column_swapped(const int fd, const int fout) {
   char buf[64];
   memset(&buf[0], 0, sizeof(buf));
   /*
    * CSI > Ps q
    *    Ps = 0   =>   DCS > | text ST
    */
-  fputs("\033[>0q", stdout);
-  fflush(stdout);
-  if (rtems_shell_term_wait_for(fd, "\033P>|", timeout)) {
-    int len = rtems_shell_term_buffer_until(fd, buf, sizeof(buf), "\033\\", timeout);
+  write(fout, "\033[>0q", 5);
+  if (rtems_shell_term_wait_for(fd, "\033P>|")) {
+    int len = rtems_shell_term_buffer_until(fd, buf, sizeof(buf), "\033\\");
     if (len > 0) {
       if (memcmp(buf, "tmux ", 5) == 0) {
         static const char* bad_versions[] = {
@@ -916,8 +930,8 @@ static bool rtems_shell_term_row_column_swapped(const int fd, const int timeout)
 static void rtems_shell_winsize( void )
 {
   const int fd = fileno(stdin);
+  const int fout = fileno(stdout);
   struct winsize ws;
-  const int timeout = 150;
   char buf[64];
   bool ok = false;
   int lines = 0;
@@ -933,18 +947,19 @@ static void rtems_shell_winsize( void )
     if (tcgetattr(fd, &cterm) >= 0) {
       struct termios term = cterm;
       term.c_cc[VMIN] = 0;
-      term.c_cc[VTIME] = 0;
-      if (tcsetattr (fd, TCSADRAIN, &term) >= 0) {
+      term.c_cc[VTIME] = rtems_shell_winsize_vtime;
+      if (tcsetattr (fd, TCSAFLUSH, &term) >= 0) {
         memset(&buf[0], 0, sizeof(buf));
         /*
          * https://invisible-island.net/xterm/ctlseqs/ctlseqs.html#h3-Miscellaneous
          *
          * CSI 1 8 t
          */
-        fputs("\033[18t", stdout);
-        fflush(stdout);
-        if (rtems_shell_term_wait_for(fd, "\033[8;", timeout)) {
-          int len = rtems_shell_term_buffer_until(fd, buf, sizeof(buf), ";", timeout);
+        if (
+          write(fout, "\033[18t", 5) == 5 &&
+          rtems_shell_term_wait_for(fd, "\033[8;")
+        ) {
+          int len = rtems_shell_term_buffer_until(fd, buf, sizeof(buf), ";");
           if (len > 0) {
             int i;
             lines = 0;
@@ -953,7 +968,7 @@ static void rtems_shell_winsize( void )
               lines *= 10;
               lines += buf[i++] - '0';
             }
-            len = rtems_shell_term_buffer_until(fd, buf, sizeof(buf), "t", timeout);
+            len = rtems_shell_term_buffer_until(fd, buf, sizeof(buf), "t");
             if (len > 0) {
               cols = 0;
               i = 0;
@@ -966,7 +981,7 @@ static void rtems_shell_winsize( void )
           }
         }
       }
-      if (rtems_shell_term_row_column_swapped(fd, timeout)) {
+      if (ok && rtems_shell_term_row_column_swapped(fd, fout)) {
         int tmp = lines;
         lines = cols;
         cols = tmp;
-- 
1.8.3.1



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