I implemented a width field

Makefile

@@ -1,4 +1,6 @@
 CFLAGS = --std=c99 -O2 -pedantic -Wall -Wextra -Wshadow
+CFLAGS += -Wstrict-prototypes -Wmissing-prototypes -Wundef
+CFLAGS += -Wpointer-arith -Wcast-align -Wcast-qual -Wredundant-decls
 
 %_check: %.out %.gold
 	cmp $^

README.md

@@ -8,7 +8,7 @@ Motivation
 
 I was recently working on an embedded project with a STM32 MCU.
 The chip had 32kB of flash memory - that's heaps for a microcontroller!
-How surprised I was when the linker suddelnly failed saying that
+How surprised I was when the linker suddenly failed saying that
 the program is too big and won't fit! How come?!
 
 It's just some USB, I2C, GPIO, a few timers ... and snprintf()
@@ -88,12 +88,13 @@ All rights reserved.
 
 Redistribution and use in source and binary forms, with or without
 modification, are permitted provided that the following conditions are met:
+
     * Redistributions of source code must retain the above copyright
       notice, this list of conditions and the following disclaimer.
     * Redistributions in binary form must reproduce the above copyright
       notice, this list of conditions and the following disclaimer in the
       documentation and/or other materials provided with the distribution.
-    * Neither the name of the auhor nor the names of its contributors
+    * Neither the name of the author nor the names of its contributors
       may be used to endorse or promote products derived from this software
       without specific prior written permission.
 

mini-printf.c

@@ -53,11 +53,11 @@ mini_strlen(const char *s)
 
 static unsigned int
 mini_itoa(int value, unsigned int radix, unsigned int uppercase, unsigned int unsig,
-	 char *buffer, unsigned int zero_pad)
+	 char *buffer, unsigned int zero_pad, unsigned int width)
 {
-	char	*pbuffer = buffer;
-	int	negative = 0;
-	unsigned int	i, len;
+	char *pbuffer = buffer;
+	int negative = 0;
+	unsigned int i, len;
 
 	/* No support for unusual radixes. */
 	if (radix > 16)
@@ -81,6 +81,9 @@ mini_itoa(int value, unsigned int radix, unsigned int uppercase, unsigned int un
 	if (negative)
 		*(pbuffer++) = '-';
 
+	for (i = (pbuffer - buffer); i < width; i++)
+		*(pbuffer++) = ' ';
+
 	*(pbuffer) = '\0';
 
 	/* ... now we reverse it (could do it recursively but will
@@ -137,18 +140,30 @@ mini_vsnprintf(char *buffer, unsigned int buffer_len, const char *fmt, va_list v
 	b.pbuffer = buffer;
 	b.buffer_len = buffer_len;
 
+	if (buffer_len > 0) *buffer = 0;
+
 	while ((ch=*(fmt++))) {
 		if ((unsigned int)((b.pbuffer - b.buffer) + 1) >= b.buffer_len)
 			break;
 		if (ch!='%')
 			_putc(ch, &b);
 		else {
-			char zero_pad = 0;
+			unsigned int zero_pad = 0;
 			char *ptr;
 			unsigned int len;
+			unsigned int width = 0;
 
-			ch=*(fmt++);
+			ch=*(fmt++);  // step over the %
 
+			/* Format width */
+			if (ch>'0' && ch<='9') {
+				width = ch-'0';
+				while (ch=*(fmt++), ch>='0' && ch<='9') {
+					width = width*10 +  ch - '0';
+				}
+				if (ch == '\0')
+					goto end;
+			}
 			/* Zero padding requested */
 			if (ch=='0') {
 				ch=*(fmt++);
@@ -165,13 +180,15 @@ mini_vsnprintf(char *buffer, unsigned int buffer_len, const char *fmt, va_list v
 
 				case 'u':
 				case 'd':
-					len = mini_itoa(va_arg(va, unsigned int), 10, 0, (ch=='u'), bf, zero_pad);
+					if (width > sizeof bf) width = sizeof bf;  /* prevent buffer overflow */
+					len = mini_itoa(va_arg(va, unsigned int), 10, 0, (ch=='u'), bf, zero_pad, width);
 					_puts(bf, len, &b);
 					break;
 
 				case 'x':
 				case 'X':
-					len = mini_itoa(va_arg(va, unsigned int), 16, (ch=='X'), 1, bf, zero_pad);
+					if (width > sizeof bf) width = sizeof bf;  /* prevent buffer overflow */
+					len = mini_itoa(va_arg(va, unsigned int), 16, (ch=='X'), 1, bf, zero_pad, width);
 					_puts(bf, len, &b);
 					break;
 
@@ -181,7 +198,11 @@ mini_vsnprintf(char *buffer, unsigned int buffer_len, const char *fmt, va_list v
 
 				case 's' :
 					ptr = va_arg(va, char*);
-					_puts(ptr, mini_strlen(ptr), &b);
+					{
+						unsigned l = mini_strlen(ptr);
+						for (unsigned ix=l; ix<width; ix++) _putc(' ', &b);
+						_puts(ptr, l, &b);
+					}
 					break;
 
 				default:

test1.c

@@ -1,18 +1,39 @@
 #include <stdio.h>
+#ifndef _LIBC_REVERT
 #include "mini-printf.h"
+#define snprintf mini_snprintf
+#endif
 
 int main(void)
 {
 	char buff[30];
-	mini_snprintf(buff, sizeof buff, "testing %d %d %07d", 1, 2, 3);
+	snprintf(buff, sizeof buff, "testing %d %d %07d", 1, 2, 3);
 	puts(buff);
-	mini_snprintf(buff, sizeof buff, "faster %s %ccheaper%c", "and", 34, 34);
+	snprintf(buff, sizeof buff, "faster %s %ccheaper%c", "and", 34, 34);
 	puts(buff);
-	mini_snprintf(buff, sizeof buff, "%x %% %X", 0xdeadf00d, 0xdeadf00d);
+	snprintf(buff, sizeof buff, "%x %% %X", 0xdeadf00d, 0xdeadf00d);
 	puts(buff);
-	mini_snprintf(buff, sizeof buff, "%09d%09d%09d%09d%09d", 1, 2, 3, 4, 5);
+	snprintf(buff, sizeof buff, "%09d%09d%09d%09d%09d", 1, 2, 3, 4, 5);
 	puts(buff);
-	mini_snprintf(buff, sizeof buff, "%d %u %d %u", 50, 50, -50, -50);
+	snprintf(buff, sizeof buff, "%d %u %d %u", 50, 50, -50, -50);
+	puts(buff);
+	snprintf(buff, sizeof buff, "%0");
+	puts(buff);
+	snprintf(buff, sizeof buff, "a%0");
+	puts(buff);
+	snprintf(buff, sizeof buff, "%");
+	puts(buff);
+	snprintf(buff, sizeof buff, "b%");
+	puts(buff);
+	snprintf(buff, 0, "%s", "hello");
+	puts(buff);
+	snprintf(buff, sizeof buff, "");
+	puts(buff);
+	snprintf(buff, sizeof buff, "(%6d) (%12d)", 78, 78);
+	puts(buff);
+	snprintf(buff, sizeof buff, "(%s) (%12s) (%s)", "a", "b", "xcccccccccccccccx");
+	puts(buff);
+	snprintf(buff, sizeof buff, "(%s)", "xcccccccccccccccx");
 	puts(buff);
 	return 0;
 }

test1.gold

@@ -3,3 +3,12 @@ faster and "cheaper"
 deadf00d % DEADF00D
 00000000100000000200000000300
 50 50 -50 4294967246
+
+a
+
+b
+b
+
+(    78) (          78)
+(a) (           b) (xcccccccc
+(xcccccccccccccccx)