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ft_printf

ft_printf is a custom implementation of the printf function in C. This project is part of the 1337 curriculum and aims to recreate formatted output functionality while working with variadic arguments.

How Variadic Functions Work

In C, functions like printf use variadic arguments to handle a variable number of inputs. Variadic functions rely on:

  1. Registers: On many modern systems, the first few function arguments are stored in CPU registers like RDI, RSI, etc., for efficiency.
  2. Stack: If there are more arguments than available registers, the remaining arguments are stored in the stack.

Registers

  • Registers are small, fast memory locations inside the CPU.
  • In the x86-64 ABI, the first arguments are passed in registers:
    • General-purpose registers: RDI, RSI, RDX, RCX, R8, R9.
    • Floating-point registers: XMM0 to XMM7.
  • Arguments exceeding the available registers are stored in the stack.

va_list and Variadic Functions

The C standard provides tools to handle variadic arguments via <stdarg.h>:

  • va_list: Tracks where the arguments are located (registers or stack).
  • va_start: Initializes the va_list to point to the first argument.
  • va_arg: Retrieves the next argument and moves to the next.
  • va_end: Cleans up the va_list after usage.

How ft_printf Works

  1. Parse the format string:

    • Process normal text by printing it directly.
    • Handle format specifiers (e.g., %d, %s) by fetching arguments.

  2. Retrieve arguments:

    • Use va_arg to get each argument based on the format specifier.
    • Convert the arguments into strings or appropriate formats.

  3. Output the result:

    • Combine text and formatted arguments.
    • Use write to output the final result.

Supported Format Specifiers

  • %c: Print a single character.
  • %s: Print a string.
  • %d / %i: Print a decimal integer.
  • %u: Print an unsigned decimal integer.
  • %x / %X: Print a hexadecimal number (lowercase/uppercase).
  • %%: Print a literal %.include "ft_printf.h"

⚠️ Just for Educational Purposes 📚
This project is for learning and practicing C programming. Do not use it in production environments.