ft_printf - Architecture Documentation

Project Overview

A custom implementation of the C standard library's printf() function. It formats and prints output to standard output, supporting multiple format specifiers.

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Design Architecture

Entry Point

ft_printf(format, ...)

• Main function accepting format string and variadic arguments
• Returns total character count printed

Processing Flow

ft_printf()
    ↓
    Format String Parser (scan for '%' specifiers)
    ↓
    format_specifier() (static helper)
    ↓
    va_list argument extractor
    ↓
    Specific Output Functions (based on specifier)
    ↓
    ft_putchar_fd() (base output function)

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Function Hierarchy

Level 1: Main Entry Point

• ft_printf(const char *format, ...) - Parses format string, routes specifiers, accumulates output count

Level 2: Dispatcher

• format_specifier(char, va_list*) - Routes to appropriate output function based on specifier type

Level 3: Output Functions (Output Handlers)

Direct Output (writes 1 character)

• ft_putchar_fd(char c) - Base function, writes single character to stdout

String Output

• ft_putstr_fd(char *c) - Writes entire string; handles NULL with "(null)"
  • Calls: ft_putchar_fd() for each character

Numeric Output

• ft_putnbr_fd(int n) - Converts signed integer to decimal; handles negative

  • Calls: ft_putchar_fd() for each digit (recursive decomposition)

• ft_putnbr_u_fd(unsigned int n) - Converts unsigned integer to decimal

  • Calls: ft_putchar_fd() for each digit (recursive decomposition)

Hexadecimal Output

• print_hex_l(unsigned long nbr) - Converts to lowercase hex (0-9, a-f)

  • Calls: ft_putchar_fd() for each hex digit (recursive decomposition)

• print_hex_u(unsigned long nbr) - Converts to uppercase hex (0-9, A-F)

  • Calls: ft_putchar_fd() for each hex digit (recursive decomposition)

Pointer Output

• print_pointer(void *ptr) - Formats pointer address as "0x..." in hex
  • Calls: ft_putstr_fd() and print_hex_l()

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Supported Format Specifiers

Specifier	Type	Handler Function
%c	Character	ft_putchar_fd()
%s	String	ft_putstr_fd()
%p	Pointer	print_pointer()
%d / %i	Signed Integer	ft_putnbr_fd()
%u	Unsigned Integer	ft_putnbr_u_fd()
%x	Hex (lowercase)	print_hex_l()
%X	Hex (uppercase)	print_hex_u()
%%	Literal %	ft_putchar_fd('%')

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Data Flow Example

Input: ft_printf("Hello %d %x\n", 42, 255)

ft_printf("Hello %d %x\n", 42, 255)
    ↓ Parse "Hello " → ft_putchar_fd() × 6
    ↓ Detect '%d' → format_specifier('d', &args)
    ↓ va_arg(args, int) → 42
    ↓ ft_putnbr_fd(42) → recursively outputs "42" (3 chars)
    ↓ Parse " " → ft_putchar_fd() × 1
    ↓ Detect '%x' → format_specifier('x', &args)
    ↓ va_arg(args, unsigned int) → 255
    ↓ print_hex_l(255) → recursively outputs "ff" (2 chars)
    ↓ Parse "\n" → ft_putchar_fd() × 1
    ↓ Return 13 (total characters printed)

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Key Implementation Details

• Base Function: All output ultimately calls ft_putchar_fd() using write(1, &ch, 1)
• Return Values: Each function returns count of characters written (for accumulation)
• Recursion: Number-to-string conversion uses recursion to process digits from most-significant to least
• NULL Handling: String function handles NULL pointers with "(null)"; pointer function uses "(nil)"