_printf(); Project

The _printf` function documentation.

• This documentation is an explanation of how _printf was created, and how it works.

• _printf() function is used to print the “character, string, float, integer, octal and hexadecimal values” onto the output screen.

Creating the _printf(); function.

• To create the _printf(); function, my team took the inititatiave of making a number of different files:

• File: holberto.h ---- Header file, contains the prototypes, includes all the librabries needed for this project, and it contains a typedef struct

  /**
  * format_spec - struct
  */
  typedef struct format_spec
  {
    char  *spec;
    int (*f)(va_list);
  } spec_type;
  /* f is function pointer */

• File: _printf.c ---- contains the _printf(); function.

  /* _printf Prototype */
  
  int _printf(const char *format, ...);
  
  /* ^ The _printf function ^ */

  • The function takes in a char pointer (char *format), and an ellipsis (...)

    • An ellipsis is used to represent a variable number of parameters to a function.

  • The function returns and int value.

    • In this function we created two variables and a function pointer.

    int index;

    The index variable use, is to loop through the indexes of format

    • As it loops through we are checking if format[index] == '%' if true skip to the next index. If the next index equals any of the specifiers declared (%d, %i, %, %c, %s, %r) then call the corresponding function to format. Read files format_number.c, format_number2.c, and get_specifier.c.

    int spec_count;

    int (*get_f_spec)(va_list);

    The function pointer get_f_spec.

    • get_f_spec is a function pointer to a function that takes (va_list) and returns int get_f_spec is set equal to get_specifier(format[index])

      get_specifier(); is in file: get_specifier.c

• File: get_specifier.c ---- contains the get_specifier(); function.

  int (*get_specifier(char format))(va_list);

  • In the function we created and int variable and a 2d array.

    int i;
    
    spec_type type[] = {
    	      	     {"i", get_int}, /* <--> remember the struct in the "holberton.h" file? in this case 'i' is spec (the char), and get_int takes over the function pointer ( `int (*f)(va_list);` or f )*/
        {"d", get_int}
        //there is more code
    }

    The ( i ) variable use, in the function is to increment and check for indexes of array type[] inside of a for() loop.

    • The for() loop checks if format is equal to any of the specifiers (%d, %i, %, %c, %s, %r), if true return the correspoding function.

      Example:

      • _printf("%d", 21); ----> In this example d is the specifier, and the corresponding function is get_int.

  • File: format_number.c ---- contains function:

    int get_int(va_list arg); /* for specifiers %i and %d */

  • File: format_functions.c ---- contains functions:

    int get_char(va_list arg); /* for specifier %c */

    int get_string(va_list arg); /* for specifier %s */

  • File: format_functions2.c ---- contains functions:

    int get_reverse(va_list arg); /* for specifier %r - prints reversed Ex: string -> "gnirts" */

    int get_percent(va_list __attribute__((unused)) arg); /* print the '%' sign */

    int get_hex(va_list arg); /* for %x - prints lowercase hex. */

    int get_heX(va_list arg); /* for %X - prints UPPERCASE HEX. */

    ⠀
    

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⠀
⠀ ⠀ ⠀ Author: Marcelo Martins
⠀ ⠀ ⠀ GitHub: @matxa
⠀ ⠀ ⠀ Email: matxa21@gmail.com
⠀

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