From 888ad352eb41b656d271183b563142472ad712ad Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Beat=20K=C3=BCng?= <beat-kueng@gmx.net>
Date: Sat, 11 Aug 2018 13:14:41 +0000
Subject: [PATCH] Merged in bkueng/nuttx-apps (pull request #150)

nsh: add inverted logic support in the form of 'if ! <cmd>'

Approved-by: GregoryN <gnutt@nuttx.org>
---
 nshlib/README.txt  |  2 +-
 nshlib/nsh.h       |  3 ++-
 nshlib/nsh_parse.c | 20 +++++++++++++++++++-
 3 files changed, 22 insertions(+), 3 deletions(-)

diff --git a/nshlib/README.txt b/nshlib/README.txt
index 69aa566fd..68b5d7852 100644
--- a/nshlib/README.txt
+++ b/nshlib/README.txt
@@ -100,7 +100,7 @@ Conditional Command Execution
   command line but is primarily intended for use within NSH scripts
   (see the sh command).  The syntax is as follows:
 
-    if <cmd>
+    if [!] <cmd>
     then
       [sequence of <cmd>]
     else
diff --git a/nshlib/nsh.h b/nshlib/nsh.h
index 0a7bdd0e4..187cc5696 100644
--- a/nshlib/nsh.h
+++ b/nshlib/nsh.h
@@ -754,7 +754,8 @@ struct nsh_itef_s
 {
   uint8_t   ie_ifcond   : 1;   /* Value of command in 'if' statement */
   uint8_t   ie_disabled : 1;   /* TRUE: Unconditionally disabled */
-  uint8_t   ie_unused   : 4;
+  uint8_t   ie_inverted : 1;   /* TRUE: inverted logic ('if ! <cmd>') */
+  uint8_t   ie_unused   : 3;
   uint8_t   ie_state    : 2;   /* If-then-else state (see enum nsh_itef_e) */
 };
 #endif
diff --git a/nshlib/nsh_parse.c b/nshlib/nsh_parse.c
index f41097703..c25e9ae6d 100644
--- a/nshlib/nsh_parse.c
+++ b/nshlib/nsh_parse.c
@@ -468,7 +468,8 @@ static int nsh_saveresult(FAR struct nsh_vtbl_s *vtbl, bool result)
   if (np->np_iestate[np->np_iendx].ie_state == NSH_ITEF_IF)
     {
       np->np_fail = false;
-      np->np_iestate[np->np_iendx].ie_ifcond = result;
+      np->np_iestate[np->np_iendx].ie_ifcond =
+        np->np_iestate[np->np_iendx].ie_inverted ^ result;
       return OK;
     }
   else
@@ -1957,6 +1958,7 @@ static int nsh_itef(FAR struct nsh_vtbl_s *vtbl, FAR char **ppcmd,
   FAR struct nsh_parser_s *np = &vtbl->np;
   FAR char *cmd = *ppcmd;
   bool disabled;
+  bool inverted_result = false;
 
   if (cmd)
     {
@@ -1973,6 +1975,20 @@ static int nsh_itef(FAR struct nsh_vtbl_s *vtbl, FAR char **ppcmd,
               goto errout;
             }
 
+          /* Check for inverted logic */
+          if (strcmp(*ppcmd, "!") == 0)
+            {
+              inverted_result = true;
+
+              /* Get the next cmd */
+              *ppcmd = nsh_argument(vtbl, saveptr, memlist);
+              if (!*ppcmd)
+                {
+                  nsh_output(vtbl, g_fmtarginvalid, "if");
+                  goto errout;
+                }
+            }
+
           /* Verify that "if" is valid in this context */
 
           if (np->np_iestate[np->np_iendx].ie_state == NSH_ITEF_IF)
@@ -1996,6 +2012,7 @@ static int nsh_itef(FAR struct nsh_vtbl_s *vtbl, FAR char **ppcmd,
           np->np_iestate[np->np_iendx].ie_state    = NSH_ITEF_IF;
           np->np_iestate[np->np_iendx].ie_disabled = disabled;
           np->np_iestate[np->np_iendx].ie_ifcond   = false;
+          np->np_iestate[np->np_iendx].ie_inverted = inverted_result;
         }
 
       /* Check if the token is "then" */
@@ -2085,6 +2102,7 @@ errout:
   np->np_iestate[0].ie_state    = NSH_ITEF_NORMAL;
   np->np_iestate[0].ie_disabled = false;
   np->np_iestate[0].ie_ifcond   = false;
+  np->np_iestate[0].ie_inverted = false;
   return ERROR;
 }
 #endif