From d144ab9af005a6731753747bdfe00953753c195a Mon Sep 17 00:00:00 2001
From: Oluwatobi Oladoye <oladoyeolamide@gmail.com>
Date: Sun, 12 Nov 2023 22:30:37 +0000
Subject: [PATCH] Parse format string

Additions:
- parse_format function
- handle_percent function
- code refactoring
- stop va_list iteration

Removal
- print_error source code
---
 _printf.c        | 29 ++++++++++---------
 main.h           |  8 ++++--
 parser.c         | 72 ++++++++++++++++++++++++++++++++++++++++++++++++
 print_literals.c |  1 -
 4 files changed, 92 insertions(+), 18 deletions(-)
 create mode 100644 parser.c

diff --git a/_printf.c b/_printf.c
index 86177f3..b68567d 100644
--- a/_printf.c
+++ b/_printf.c
@@ -1,5 +1,3 @@
-#include <unistd.h>
-#include <stdarg.h>
 #include "main.h"
 
 /**
@@ -11,24 +9,26 @@
   */
 int _printf(const char *format, ...)
 {
-	int char_count = 0;
+	int char_count = 0, fmt_status;
 	va_list ap;
 
-	va_start(ap, format);
-
 	if (!(*format))
-		write(1, "User input is needed", 21);
+		return (char_count);
+	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);
-
-		++format;
+		va_start(ap, format);
+		while (*format)
+		{
+			if (*format == '%')
+				char_count += p_func(ap, *++format);
+			else
+				char_count += write(1, format, 1);
+			++format;
+		}
+		va_end(ap);
 	}
-
 	return (char_count);
 }
 
@@ -55,6 +55,5 @@ int p_func(va_list ap, char specifier)
 			char_count += write(1, "%", 1);
 			break;
 	}
-
 	return (char_count);
 }
diff --git a/main.h b/main.h
index 4d68fee..9bd144f 100644
--- a/main.h
+++ b/main.h
@@ -1,11 +1,15 @@
 #ifndef MAIN_H
 #define MAIN_H
+
+#include <unistd.h>
 #include <stdarg.h>
+#include <string.h>
 
 int _printf(const char *format, ...);
+int parse_format(const char *);
+int handle_percent(char, char);
+int p_func(va_list, char);
 int print_char(va_list);
 int print_string(va_list);
-int p_func(va_list, char);
-void print_error(char *);
 
 #endif
diff --git a/parser.c b/parser.c
new file mode 100644
index 0000000..b8d479d
--- /dev/null
+++ b/parser.c
@@ -0,0 +1,72 @@
+#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, 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]
+					!= '%')
+			{
+				ret_val = 0;
+				break;
+			}
+			if (fmt[i + 1] == '%') /* % was escaped */
+			{
+				/* Returns (0) when last char is % */
+				if ((i + 2) == len && fmt[i + 2] == '%')
+				{
+					ret_val = 0;
+					break;
+				}
+				/*Fast forward check to determine next-2 chars*/
+				if ((i + 2) < len)
+				{
+					ret_val = (handle_percent(fmt[i + 2], fmt[i
+								+ 3]));
+					if (ret_val == 0)
+						break;
+				}
+			}
+			i += 2; /* skip determined fmt specifier */
+		}
+		else
+		{
+			ret_val = 1;
+			i++;
+		}
+	}
+	return (ret_val);
+}
+
+/**
+ * handle_percent - fast forward check
+ * @nxt2: Third char of *fmt
+ * @nxt3: Fourth char of *fmt
+ * Description: Fast forward check the next
+ * two chars of %.
+ * Return: 1 (valid) or 0 (invalid)
+ */
+int handle_percent(char nxt2, char nxt3)
+{
+	if (nxt2 == '%')
+		if (nxt3 != 'c' && nxt3 != 's' && nxt3 != '%')
+			return (0);
+	return (1);
+}
diff --git a/print_literals.c b/print_literals.c
index 4970d60..77a77bb 100644
--- a/print_literals.c
+++ b/print_literals.c
@@ -1,4 +1,3 @@
-#include <unistd.h>
 #include "main.h"
 
 /**