Gzoref/printf

printf

C

_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. */

⠀

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