Added interpretation of the '%' conversion specifier which acts as an

escape sequence printing a literal '%'.
Added the 'X' conversion specifier which differs from the 'x' specifier
in that resulting letters are converted to uppercase.
Added interpretation of the '#' alt flag which now causes the '0x'
prefix to be added to every hex conversion.

2 files changed, 46 insertions, 19 deletions

diff --git a/kernel/kmain.c b/kernel/kmain.c
index 793ca17..e31782c 100644
--- a/kernel/kmain.c
+++ b/kernel/kmain.c
@@ -8,5 +8,8 @@ void kmain(void) {
   printf("Kernel booting...\n");
   printf("Kernel booted!\n");
 
-  printf("Number: %04x\n", 0x18C);
+  printf("Number: %s %04x\n", "test", 0x18C);
+  printf("Number: %s %04X\n", "test", 0x18C);
+  printf("Number: %s %#04x\n", "test", 0x18C);
+  printf("Number: %s %#04X\n", "test", 0x18C);
 }
diff --git a/kernel/vsprintf.c b/kernel/vsprintf.c
index 93a2ada..4fdb2c4 100644
--- a/kernel/vsprintf.c
+++ b/kernel/vsprintf.c
@@ -2,23 +2,35 @@
 #include <stdint.h>
 
 enum TYPE {
-  TYPE_INT    = 1,
-  TYPE_UINT   = 2,
-  TYPE_HEX    = 3,
-  TYPE_STRING = 4
+  TYPE_INT      = 1,
+  TYPE_UINT     = 2,
+  TYPE_HEX      = 3,
+  TYPE_STRING   = 4,
+  TYPE_PERCENT  = 5
 };
 
 enum FLAGS {
   FL_ZERO     = 1, /* zero padded */
+  FL_ALT      = 2, /* alternate form (effect is type dependent) */
+  FL_UPPER    = 4  /* uppercase */
 };
 
 static void hex(char **str, char flags, int fwidth, int size, int x) {
   int i, y, len;
   char c;
-  char *s = "0x";
+  char *prefl = "0x";
+  char *prefu = "0X";
 
-  while(*s)
-    *(*str)++ = *s++;
+  /* print the prefix, if the alt flag is set */
+  if(flags & FL_ALT) {
+    if(flags & FL_UPPER) {
+      while(*prefu)
+        *(*str)++ = *prefu++;
+    } else {
+      while(*prefl)
+        *(*str)++ = *prefl++;
+    }
+  }
 
   /* calculate the number of digits */
   len = 0;
@@ -40,8 +52,11 @@ static void hex(char **str, char flags, int fwidth, int size, int x) {
   /* actually print the digits */
   for(i = 0; i < sizeof(x) << 1; i++) {
     c = ((unsigned int) x >> 28) + '0';
-    if(c > '9')
-      c += 7;
+    if(c > '9') {
+      c += 0x27;
+      if(flags & FL_UPPER)
+        c -= 0x20;
+    }
 
     if(c != '0')
       *(*str)++ = c;
@@ -70,37 +85,43 @@ int vsprintf(char *str, char *fmt, va_list ap) {
     fmt++;
     while(1) {
       switch(*fmt) {
+        case '#':
+          flags |= FL_ALT;
+          break;
+        case '%':
+          type = TYPE_PERCENT;
+          goto done;
         case 's':
-          if(type)
-            goto done;
           type = TYPE_STRING;
-          break;
+          goto done;
         case 'x':
-          if(type)
-            goto done;
           type = TYPE_HEX;
-          break;
+          goto done;
+        case 'X':
+          type = TYPE_HEX;
+          flags |= FL_UPPER;
+          goto done;
         default:
           /* the first zero enables zero-padding */
           if(*fmt == '0' && !fwidth) {
             flags |= FL_ZERO;
-            goto next;;
+            goto next;
           }
 
           /* subsequent numbers indicate field width */
           if(*fmt >= '0' && *fmt <= '9') {
             fwidth = (fwidth * 10) + (*fmt - '0');
-            goto next;;
+            goto next;
           }
 
           goto done;
-          break;
       }
 next:
       fmt++;
     }
 
 done:
+    fmt++;
 
     switch(type) {
       case TYPE_STRING:
@@ -112,6 +133,9 @@ done:
         x = va_arg(ap, int);
         hex(&str, flags, fwidth, 4, x);
         break;
+      case TYPE_PERCENT:
+        *str++ = '%';
+        break;
     }
   }