Implement missing 'space' formatting flag

This flag causes space (padding) to be reserved for the sign even if the
number is positive. It is basically the same as the 'plus' flag except that
a space is displayed instead of a plus sign. The 'plus' flag takes precedence.

src/library.js

@@ -1974,6 +1974,7 @@ LibraryManager.library = {
         var flagLeftAlign = false;
         var flagAlternative = false;
         var flagZeroPad = false;
+        var flagPadSign = false;
         flagsLoop: while (1) {
           switch (next) {
             case {{{ charCode('+') }}}:
@@ -1992,6 +1993,9 @@ LibraryManager.library = {
                 flagZeroPad = true;
                 break;
               }
+            case {{{ charCode(' ') }}}:
+              flagPadSign = true;
+              break;
             default:
               break flagsLoop;
           }
@@ -2158,8 +2162,12 @@ LibraryManager.library = {
             }
 
             // Add sign if needed
-            if (flagAlwaysSigned && currArg >= 0) {
+            if (currArg >= 0) {
-              prefix = '+' + prefix;
+              if (flagAlwaysSigned) {
+                prefix = '+' + prefix;
+              } else if (flagPadSign) {
+                prefix = ' ' + prefix;
+              }
             }
 
             // Move sign to prefix so we zero-pad after the sign
@@ -2250,8 +2258,12 @@ LibraryManager.library = {
               if (next == {{{ charCode('E') }}}) argText = argText.toUpperCase();
 
               // Add sign.
-              if (flagAlwaysSigned && currArg >= 0) {
+              if (currArg >= 0) {
-                argText = '+' + argText;
+                if (flagAlwaysSigned) {
+                  argText = '+' + argText;
+                } else if (flagPadSign) {
+                  argText = ' ' + argText;
+                }
               }
             }
 

tests/printf/output.txt

@@ -6,9 +6,12 @@ Decimals: 1977 650000 12 4
 Preceding with blanks:       1977      -1977
 Preceding with zeros: 0000001977 -000001977
 Force sign: +1977 -1977  +1977  -1977
+Force sign or space:  1977 -1977   1977  -1977
+Sign overrides space: +1977 -1977  +1977  -1977
 Some different radixes: 100 64 144 0x64 0144
 floats: 3.14 +3e+00 3.141600E+00 00003.14
 negative floats: -3.14 -3e+00 -3.141600E+00 -0003.14
+Force sign or space:  3.14 -3.14   3.14  -3.14
 Width trick:    10
 A string %
 Null string:  (null)

tests/printf/output_i64_1.txt

@@ -6,9 +6,12 @@ Decimals: 1977 650000 12 4
 Preceding with blanks:       1977      -1977
 Preceding with zeros: 0000001977 -000001977
 Force sign: +1977 -1977  +1977  -1977
+Force sign or space:  1977 -1977   1977  -1977
+Sign overrides space: +1977 -1977  +1977  -1977
 Some different radixes: 100 64 144 0x64 0144
 floats: 3.14 +3e+00 3.141600E+00 00003.14
 negative floats: -3.14 -3e+00 -3.141600E+00 -0003.14
+Force sign or space:  3.14 -3.14   3.14  -3.14
 Width trick:    10
 A string %
 Null string:  (null)

tests/printf/test.c

@@ -11,9 +11,12 @@ int main() {
   printf("Preceding with blanks: %10d %10d\n", 1977, -1977);
   printf("Preceding with zeros: %010d %010d\n", 1977, -1977);
   printf("Force sign: %+d %+d %+6d %+6d\n", 1977, -1977, 1977, -1977);
+  printf("Force sign or space: % d % d % 6d % 6d\n", 1977, -1977, 1977, -1977);
+  printf("Sign overrides space: % +d % +d % +6d % +6d\n", 1977, -1977, 1977, -1977);
   printf("Some different radixes: %d %x %o %#x %#o\n", 100, 100, 100, 100, 100);
   printf("floats: %4.2f %+.0e %E %08.2f\n", 3.1416, 3.1416, 3.1416, 3.1416);
   printf("negative floats: %4.2f %+.0e %E %08.2f\n", -3.1416, -3.1416, -3.1416, -3.1416);
+  printf("Force sign or space: % .2f % .2f % 6.2f % 6.2f\n", 3.1416, -3.1416, 3.1416, -3.1416);
   printf("Width trick: %*d\n", 5, 10);
   printf("%s %%\n", "A string");
   printf("Null string: %7s\n", NULL);