Add debug output and a few elementary stdlib functions.

1 files changed, 105 insertions, 0 deletions

diff --git a/kernel/lib/printf.c b/kernel/lib/printf.c
new file mode 100644
index 0000000..fdf474d
--- /dev/null
+++ b/kernel/lib/printf.c
@@ -0,0 +1,105 @@
+#include <printf.h>
+#include <stdarg.h>
+
+int snprintf(char * buff, size_t len, const char *format, ...) {
+	va_list ap;
+
+	va_start(ap, format);
+	len = vsnprintf(buff, len, format, ap);
+	va_end(ap);
+
+	return len;
+}
+
+int vsnprintf(char *buff, size_t len, const char* format, va_list ap){
+	size_t i, result;
+
+	if (!buff || !format)
+		return -1;
+
+#define PUTCHAR(thechar) \
+	do { \
+		if (result < len-1) \
+		*buff++ = (thechar);  \
+		result++; \
+	} while (0)
+
+	result = 0;
+	for(i = 0; format[i] != '\0' ; i++) {
+		if (format[i] == '%') {
+			i++;
+			switch(format[i]) {
+				case '%':
+					PUTCHAR('%');
+					break;
+
+				case 'i':;
+				case 'd': {
+					 int integer = va_arg(ap,int);
+					 int cpt2 = 0;
+					 char buff_int[16];
+
+					 if (integer<0)
+						 PUTCHAR('-');
+
+					 do {
+						 int m10 = integer%10;
+						 m10 = (m10 < 0)? -m10:m10;
+						 buff_int[cpt2++] = (char)('0'+ m10);
+						 integer = integer/10;
+					 } while(integer != 0);
+
+					 for(cpt2 = cpt2 - 1; cpt2 >= 0; cpt2--)
+						 PUTCHAR(buff_int[cpt2]);
+
+					 break;
+				}
+				case 'c': {
+					 int value = va_arg(ap,int);
+					 PUTCHAR((char)value);
+					 break;
+				}
+				case 's': {
+					 char *string = va_arg(ap,char *);
+					 if (!string)
+						 string = "(null)";
+					 for(; *string != '\0' ; string++)
+						 PUTCHAR(*string);
+					 break;
+				}
+				case 'x': {
+					 unsigned int hexa = va_arg(ap,int);
+					 unsigned int nb;
+					 int j, had_nonzero = 0;
+					 for(j = 0; j < 8; j++)
+					 {
+						 nb = (unsigned int)(hexa << (j*4));
+						 nb = (nb >> 28) & 0xf;
+						 // Skip the leading zeros
+						 if (nb == 0) {
+							 if (had_nonzero)
+								 PUTCHAR('0');
+						 } else {
+							 had_nonzero = 1;
+							 if (nb < 10)
+								 PUTCHAR('0'+nb);
+							 else
+								 PUTCHAR('a'+(nb-10));
+						 }
+					 }
+					 if (!had_nonzero)
+						 PUTCHAR('0');
+					 break;
+				}
+				default:
+					 PUTCHAR('%');
+					 PUTCHAR(format[i]);
+			}
+		} else {
+			PUTCHAR(format[i]);
+		}
+	}
+
+	*buff = '\0';
+	return result;
+}