SERVER-4312 add meta-C, meta-L and meta-U to mongo shell

Added meta-C (capitalize word), meta-L (lowercase word) and
meta-U (uppercase word) readline features to the shell.  Changed
the InputBuffer struct to a class, most members are now private.
Merged some common code for ctrl-R and ctrl-S keystrokes when
already in search mode.

third_party/linenoise/linenoise.cpp

@@ -341,21 +341,22 @@ class KillRing {
 
 };
 
-struct InputBuffer {
+class InputBuffer {
     char*       buf;
     int         buflen;
     int         len;
     int         pos;
 
+    void clearScreen( PromptInfo& pi );
+    int incrementalHistorySearch( PromptInfo& pi, int startChar );
+    int completeLine( PromptInfo& pi );
+    void refreshLine( PromptBase& pi );
+
+public:
     InputBuffer( char* buffer, int bufferLen ) : buf( buffer ), buflen( bufferLen - 1 ), len( 0 ), pos( 0 ) {
         buf[0] = 0;
     }
-
     int getInputLine( PromptInfo& pi );
-    void refreshLine( PromptBase& pi );
-    int completeLine( PromptInfo& pi );
-    void clearScreen( PromptInfo& pi );
-    int incrementalHistorySearch( PromptInfo& pi, int startChar );
 
 };
 
@@ -1359,25 +1360,17 @@ int InputBuffer::incrementalHistorySearch( PromptInfo& pi, int startChar ) {
 
         // these characters stay in search mode and update the display
         case ctrlChar( 'S' ):
-            if ( dp.direction == -1 ) {
-                dp.direction = 1;
-                dp.updateSearchPrompt();
-            }
-            else {
-                searchAgain = true;
-            }
-            break;
-
         case ctrlChar( 'R' ):
             if ( dp.searchTextLen == 0 ) {  // if no current search text, recall previous text
                 dp.updateSearchText( previousSearchText.c_str() );
             }
-            if ( dp.direction == 1 ) {
-                dp.direction = -1;
-                dp.updateSearchPrompt();
+            if ( ( dp.direction ==  1 && c == ctrlChar( 'R' ) ) ||
+                 ( dp.direction == -1 && c == ctrlChar( 'S' ) ) ) {
+                dp.direction = 0 - dp.direction;    // reverse direction
+                dp.updateSearchPrompt();            // change the prompt
             }
             else {
-                searchAgain = true;
+                searchAgain = true;                 // same direction, search again
             }
             break;
 
@@ -1587,6 +1580,23 @@ int InputBuffer::getInputLine( PromptInfo& pi ) {
             if ( write( 1, "^C", 2 ) == -1 ) return -1;    // Display the ^C we got
             return -1;
 
+        case META + 'c':        // meta-C, give word initial Cap
+        case META + 'C':
+            killRing.lastAction = KillRing::actionOther;
+            if ( pos < len ) {
+                while ( pos < len && !isalnum( buf[pos] ) ) {
+                    ++pos;
+                }
+                if ( pos < len && buf[pos] >= 'a' && buf[pos] <= 'z' ) {
+                    buf[pos] += 'A' - 'a';
+                }
+                while ( pos < len && isalnum( buf[pos] ) ) {
+                    ++pos;
+                }
+                refreshLine( pi );
+            }
+            break;
+
         // ctrl-D, delete the character under the cursor
         // on an empty line, exit the shell
         case ctrlChar( 'D' ):
@@ -1704,6 +1714,23 @@ int InputBuffer::getInputLine( PromptInfo& pi ) {
             clearScreen( pi );
             break;
 
+        case META + 'l':        // meta-L, lowercase word
+        case META + 'L':
+            killRing.lastAction = KillRing::actionOther;
+            if ( pos < len ) {
+                while ( pos < len && !isalnum( buf[pos] ) ) {
+                    ++pos;
+                }
+                while ( pos < len && isalnum( buf[pos] ) ) {
+                    if ( buf[pos] >= 'A' && buf[pos] <= 'Z' ) {
+                        buf[pos] += 'a' - 'A';
+                    }
+                    ++pos;
+                }
+                refreshLine( pi );
+            }
+            break;
+
         case ctrlChar( 'N' ):   // ctrl-N, recall next line in history
         case ctrlChar( 'P' ):   // ctrl-P, recall previous line in history
         case DOWN_ARROW_KEY:
@@ -1763,6 +1790,23 @@ int InputBuffer::getInputLine( PromptInfo& pi ) {
             killRing.lastAction = KillRing::actionKill;
             break;
 
+        case META + 'u':        // meta-U, uppercase word
+        case META + 'U':
+            killRing.lastAction = KillRing::actionOther;
+            if ( pos < len ) {
+                while ( pos < len && !isalnum( buf[pos] ) ) {
+                    ++pos;
+                }
+                while ( pos < len && isalnum( buf[pos] ) ) {
+                    if ( buf[pos] >= 'a' && buf[pos] <= 'z' ) {
+                        buf[pos] += 'A' - 'a';
+                    }
+                    ++pos;
+                }
+                refreshLine( pi );
+            }
+            break;
+
         // ctrl-W, kill to whitespace (not word) to left of cursor
         case ctrlChar( 'W' ):
             if ( pos > 0 ) {