madebypixel02/ft_printf

[42 Madrid] Because putnbr and putstr are not enough

ft_printf | 42 Madrid

Because ft_putstr & ft_putnbr aren't enough 😜

Table of Contents

• ft_print what?
• Capabilities
• Bonus
• Limitations
• Installation
• Summary

ft_print what?

Printf is likely one of the most popular commands people see when learning a new programming language, and for a good reason. They are easy to understand and very powerful too. This is why learning to implement our own version of printf can help us better understand what happens internally when entering printf("Hello World")!

Capabilities

Our version of the printf function will be called ft_printf, and will be able to work with the following inputs:

• Specifiers

Specifier	Description
%	Prints the percent character
c	Prints a character
s	Prints a string (array of characters)
d,i	Prints an integer
p	Prints pointer address (hex starting with 0x)
u	Prints an unsigned integer
x	Prints an unsigned hexadecimal integer (lowecase a-f)
X	Prints an unsigned hexadecimal integer (uppercase A-F)

• Flags

Flag	Description
(width)	Specifies the minimum width of the printed variable (adds spaces when necessary)
(precision)	Selects the minimum number of elements of the variable that are printed (Eg. number of chars from a string)
-	Pads text to the left (adds spaces to the right)
0	Pads text with zeroes instead of spaces
.	Separates Width and Precision
*	Indicates that the Width or the Precision will be specified using an additional variable

Our ft_printf function has the following prototype:

int ft_printf(const char *str, ...);

The general idea of the function is to iterate over str and print normally until a % is read. From there, we parse the next elements until one of the Specifiers is found or until the end of the string \0 is reached, whichever comes first. The general structure of the elements we want to parse is the following:

%[Flags][Width].[Precision][Specifier]

Bonus

As of July 2021, the subject for this project has changed, and the flags -0. are now part of the bonuses. Also the * flag is gone entirely, though I have decided to keep it in my version of the code, since it took a while to implement and I wish to keep it. Other flags we need to implement in this bonus part are:

Bonus Flag	Description
#	Adds "0X" or "0x" to conversions with hexadecimal specifiers (excluding p) for values other than zero
(space)	A blank space is added provided that no sign is specified
+	Adds a plus sign in front of positive numbers

Limitations

As this is quite a straightforward approach at printf, there are a few limitations to consider, namely:

• Our ft_printf does not have buffer management, unlike the real printf
• This implementation of printf doesn't handle overflows and unexpected inputs the same way the real printf would
• Our ft_printf isn't nearly as powerful as the real prinft since many features are not included
• ft_printf relies on our personal libft library, which makes it slower in performance when compared to the original printf

Installation

In order for you to test this printf, it is recommended that you install the following dependencies:

gcc clang python-norminette make

For Linux users, it is also recommended to install valgrind (Leak checker)

• Testing the ft_printf function

git clone https://gitlab.com/madebypixel02/ft_printf.git
cd ft_printf
make

Feel free to replace your own libft inside the ft_printf folder

• Usage:

The makefile compiles all files from the src/ or srcb/ folders and saves the object files to the obj/ and objb/ folders. It then generates the output file libftprintf.a inside the bin/ folder. Here are some of the commands you can try:

make all		Compiles the libftprintf.a file
make test		Compiles ft_printf and libft with a custom main. Checks for leaks in Mac and Linux
make bonus		Compiles all bonus files instead of the mandatory ones
make norminette		Checks Norm for both printf and libft files	
make git		Stages every modified file to commit and pushes to upstream branch

• Example:

Summary

This was my second project as a 42 student in Madrid. Looking forward to the new projects coming next!

July 9th, 2021