Parse format string

Author: gr8justus

_printf.c

@@ -16,28 +16,33 @@
 
 int _printf(const char *format, ...)
 {
-	int char_count = 0;
+	int char_count = 0, fmt_status;
 	va_list ap;
 
-	va_start(ap, format);
 
 	if (format == NULL)
 	{
 		write(2, "Cannot print null\n", 19);
-		va_end(ap);
-		return (-1);
+		return (0);
 	}
+	fmt_status = parse_format(format);
 
-	while (*format)
+	if (fmt_status == 1)
 	{
-		if (*format == '%')
-			char_count += p_func(ap, *++format);
-		else
-			char_count += write(1, format, 1);
+		va_start(ap, format);
+		while (*format)
+		{
+			if (*format == '%')
+				char_count += p_func(ap, *++format);
+			else
+				char_count += write(1, format, 1);
 
-		++format;
+			++format;
+		}
+		va_end(ap);
 	}
-	va_end(ap);
+	else
+		write(1, "Invalid format specifier\n", 26);
 	return (char_count);
 }
 
@@ -74,8 +79,6 @@ int p_func(va_list ap, char specifier)
 		case '%':
 			char_count += write(1, "%", 1);
 			break;
-		default:
-			break;
 	}
 	va_end(ap);
 	return (char_count);

main.h

@@ -1,6 +1,7 @@
 #ifndef MAIN_H
 #define MAIN_H
 #include <stdarg.h>
+#include <string.h>
 #define ABS(x) ((x) < 0 ? -(x) : (x))
 #define MIN(x, y) (((x) < (y)) ? (x) : (y))
 #define MAX_BYTE_SIZE 30
@@ -10,7 +11,7 @@ int print_char(va_list);
 int print_string(va_list);
 int p_func(va_list, char);
 void print_error(char *);
-
+int parse_format(const char *);
 
 void *alloc(size_t);
 char *int_to_string(int);

parser.c

@@ -0,0 +1,36 @@
+#include "main.h"
+
+/**
+ * parse_format - parse format string
+ * @fmt: Format string to parse
+ * Description: Determines if the format string
+ * contains valid format specifiers.
+ * Return: 1 (valid) or 0 (invalid).
+ */
+int parse_format(const char *fmt)
+{	int i = 0, ret_val = 1, len = strlen(fmt) - 1;
+
+	while (i <= len)
+	{
+		if (fmt[i] == '%')
+		{
+			if (i + 1 > len) /* fmt[i] is the last char of *fmt */
+			{
+				ret_val = 0;
+				break;
+			}
+			/* char fmt[i] does not denote allowed specifier */
+			if (fmt[i + 1] != 'c' && fmt[i + 1] != 's' && fmt[i +
+					1] != '%' && fmt[i + 1] != 'd' && fmt[i
+					+ 1] != 'i')
+			{
+				ret_val = 0;
+				break;
+			}
+			i += 2; /* skip determined fmt specifier */
+		}
+		else
+			i++;
+	}
+	return (ret_val);
+}

print_digits.c

@@ -2,6 +2,7 @@
 #include <unistd.h>
 #include "main.h"
 #include <stdlib.h>
+#include <limits.h>
 
 /**
   * print_decimal - Auxilliary Function
@@ -19,11 +20,6 @@ int print_decimal(va_list ap)
 	int num = va_arg(ap, int);
 	char *number_string;
 
-	if (!num)
-	{
-		write(2, "Error", 6);
-		return (-1);
-	}
 	if (num < 0)
 	{
 		write(1, "-", 1);