From d2617fbb0b9d382241f72a8dd8294656477a9067 Mon Sep 17 00:00:00 2001
From: Renaud Fivet <renaud.fivet@gmail.com>
Date: Thu, 17 Dec 2020 11:03:48 +0800
Subject: [PATCH] zero padding and uppercase/lowercase for hexadecimal.

---
 printf.c | 38 +++++++++++++++++++++++++++-----------
 1 file changed, 27 insertions(+), 11 deletions(-)

diff --git a/printf.c b/printf.c
index bd42702..8deb74d 100644
--- a/printf.c
+++ b/printf.c
@@ -5,18 +5,25 @@
 #include <stdio.h>
 #include "system.h" /* kputc(), kputs() */
 
-static int kputu( unsigned u, unsigned d) {
+static int kputu( unsigned u, unsigned d, int padlen, char fmt) {
     char s[ 12] ;                   /* room for 11 octal digit + EOS */
     char *p = &s[ sizeof s - 1] ;   /* point to last byte */
 
     *p = 0 ;                        /* null terminated string */
+    fmt = fmt & 0x20 ;              /* set uppercase bit */
     do {
         unsigned r = u % d ;
         u /= d ;
-        *--p = "0123456789ABCDEF"[ r] ;
+        *--p = "0123456789ABCDEF"[ r] | fmt ;
+        padlen -= 1 ;
     } while( u) ;
 
-    return kputs( p) ;
+    while( padlen-- > 0) {
+        kputc( '0') ;
+        u += 1 ;        /* use u to calculate output length */
+    }
+
+    return u + kputs( p) ;
 }
 
 static int kputi( int i) {
@@ -26,7 +33,7 @@ static int kputi( int i) {
         kputc( '-') ;
     }
 
-    return flag + kputu( i, 10) ;
+    return flag + kputu( i, 10, 0, 'u') ;
 }
 
 int printf( const char *fmt, ...) {
@@ -38,23 +45,31 @@ int printf( const char *fmt, ...) {
     while( ( c = *fmt++) != 0)
         if( c != '%') {
             cnt += 1 ; kputc( c) ;
-        } else if( ( c = *fmt++) == 0) {
-            cnt += 1 ; kputc( '%') ;
-            break ;
-        } else
+        } else {
+            int len = 0 ;
+
+            c = *fmt++ ;
+            while( c >= '0' && c <= '9') {
+                len = len * 10 + ( c - '0') ;
+                c = *fmt++ ;
+            }
+
+            if( c == 0)
+                break ;
+
             switch( c) {
             case 'c':
                 cnt += 1 ; kputc( va_arg( ap, int /* char */)) ;
                 break ;
             case 'o':
-                cnt += kputu( va_arg( ap, unsigned), 8) ;
+                cnt += kputu( va_arg( ap, unsigned), 8, len, c) ;
                 break ;
             case 'u':
-                cnt += kputu( va_arg( ap, unsigned), 10) ;
+                cnt += kputu( va_arg( ap, unsigned), 10, len, c) ;
                 break ;
             case 'x':
             case 'X':
-                cnt += kputu( va_arg( ap, unsigned), 16) ;
+                cnt += kputu( va_arg( ap, unsigned), 16, len, c) ;
                 break ;
             case 'i':
             case 'd':
@@ -69,6 +84,7 @@ int printf( const char *fmt, ...) {
             case '%':
                 cnt += 1 ; kputc( c) ;
             }
+        }
 
     va_end( ap) ;
     return cnt ;