feat: printf statement written in c (as minprintf) without using stdi…

…o.h li… (TheAlgorithms#820)

* printf statement written in c (as minprintf) without using stdio.h library.

* Added proper documentation in minprintf.h

* Modified and more Documented code.

* Requested changes commited

* Referance links added

* updating DIRECTORY.md

* Renamed the file

* updating DIRECTORY.md

* Test file added

* updating DIRECTORY.md

* Requested changes commited

* Requested changes commited

Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com>

DIRECTORY.md

@@ -101,7 +101,9 @@
 ## Developer Tools
   * [Malloc Dbg](https://github.com/TheAlgorithms/C/blob/master/developer_tools/malloc_dbg.c)
   * [Malloc Dbg](https://github.com/TheAlgorithms/C/blob/master/developer_tools/malloc_dbg.h)
+  * [Min Printf](https://github.com/TheAlgorithms/C/blob/master/developer_tools/min_printf.h)
   * [Test Malloc Dbg](https://github.com/TheAlgorithms/C/blob/master/developer_tools/test_malloc_dbg.c)
+  * [Test Min Printf](https://github.com/TheAlgorithms/C/blob/master/developer_tools/test_min_printf.c)
 
 ## Exercism
   * Acronym

developer_tools/min_printf.h

@@ -0,0 +1,352 @@
+/**
+ * @file
+ * @brief Implementation of a [function](https://www.geeksforgeeks.org/variable-length-argument-c) similar to `printf`
+ * @details
+ * `printf` statement rewritten (as `min_printf`) in C without using the `stdio.h` library 
+ * Syntax of `min_printf` is same as `printf`
+ * Currently min_printf handles:
+ * 	Integers, Doubles, floats, characters and strings
+ * The format specifiers and escape sequence is the same as for `printf`
+ * User can also specify the width and precision if required, just like in the case of `printf`
+ * How to use it:
+ * 	- First include min_printf.h in your code
+ * 	- Then type `min_printf()`, and pass required parameters to it
+ * 	- As already specified, it's syntax is same as printf 
+ * @author [Jaskarn Singh](https://github.com/Jaskarn7)
+*/
+
+#ifndef MIN_PRINTF_H
+#define MIN_PRINTF_H
+
+#include <stdlib.h> /// for `malloc` and `free` functions
+#include <unistd.h> /// for `write` function
+#include <stdarg.h> /// for `va_start` and `va_arg` functions
+
+#define INT_MAX_LENGTH 10       /// used as standard length of string to store integers
+#define PRECISION_FOR_FLOAT 8   /// default precision for float or double if not specified
+
+/**
+ * @brief struct used to store character in certain times
+*/
+typedef struct buffer {
+	char buffr_char; // Character will be stored in this variable
+	int buf_size; // Checks if character is present in buffr_char or not, 0 if no and 1 if yes
+} Buffer;
+
+/**
+ * @details 
+ * This function return ten to the power a(The parameter specified to it) like:
+ * 		if the parameter specified is 4 i.e. -> power_of_ten(4) is called then
+ * 		this function will return ten to the power four (10000);
+ * @param a The power of ten which is to be returned
+ * @return Ten to the power a
+ */
+int power_of_ten(int a)
+{
+	int n = 1; ///< This number will be returned as ten to power of a
+	for (int i = 1; i <= a; ++i)
+		n *= 10 ;
+	return n;
+}
+
+/**
+ * @brief Checks if a character is a number
+ * @param c character to be checked if it's a number or not
+ * @return `true`(1) if the character is a number 
+ * @return `false`(0) if the character is NOT a number
+*/
+int is_number(char *c)
+{
+	return (*c >= '0' && *c <= '9') ? 1 : 0;
+}
+
+/**
+ * @brief Returns specific required next character
+ * @param p pointer to a format string of `min_printf()`
+ * @param buffer struct for checking if buffr_char character is present or not
+ * @return character inside `buffer->buffr_char`, if `buffer->buf_size` is one
+ * @return character at which p is pointing, if `buffer->buf_size` is zero
+ */
+char get_ch(char *p, Buffer *buffer)
+{
+	if (buffer->buf_size) {
+		buffer->buf_size = 0; ///< Since character is used, this sets `buffer->buf_size` to zero
+		return buffer->buffr_char; // Returns character inside buffer->buffr_char
+	}
+	return *p++;
+}
+
+/**
+ * @brief Stores character to the `buffer->buffr_char`
+ * @param c character to be stored in the `buffer->buffr_char`
+ * @param buffer struct where character will be stored
+*/
+void unget_ch(char *c, Buffer *buffer)
+{
+	buffer->buffr_char = *c;	// Character initializes inside buffer->buffr_char
+	buffer->buf_size = 1; // Sets bufsize to one as new character is stored in buffr_char
+}
+
+
+/**
+ * @brief Calculates the number of digits in a number
+ * @param n number whose digits are to be counted
+ * @return number of digits in n
+*/
+int get_number_of_digits(int n)
+{
+	int digits = 0; // Stores encountered number of digits
+	while (n > 0) {
+		++digits; // Since number still contains a digit, so increment digit variable
+		n /= 10; // Removes last digit from number
+	}
+	return digits;
+}
+
+/**
+ * @brief Prints one character on screen
+ * @param s character to be printed on the screen
+*/
+void put_char(char s)
+{
+	/* buf used for storing character to be printed in an array (+1 for '\0')*/
+	char *buf = (char *) malloc(sizeof(char) + 1); 
+	*buf = s;
+	*(buf + 1) = '\0';
+	write(1, buf, 1);
+	free(buf);
+}
+
+/**
+ * @brief Reverses a string using [two pointer algorithm](https://www.geeksforgeeks.org/program-reverse-array-using-pointers/?ref=rp)
+ * @param p pointer to the string which is to be reversed
+*/
+void reverse_str(char *p)
+{
+	char *l = p; // Points to first character of p
+	char *h = p; // Will be used to point to last character of p
+	char temp; // Temporarily stores a character, Used in swapping
+
+	while (*h != '\0') 
+		++h;
+	--h; // Now h point to last valid character of string 
+
+	/* Swap character which lower and higher are pointing until lower < higher. At that point string will be reversed.*/
+	while (l < h) {
+		temp = *l;
+		*l = *h;
+		*h = temp;
+		++l; // Increment lower to next character
+		--h; // Decrement higher to previous character from current character
+	}
+}
+
+/**
+ * @details
+ * The algorithm here is to first convert the number into 
+ * string and then reverse it be passing it to reverse_str function
+ * and then printing on the screen
+ * @param n Number to be printed
+ * @param width Total characters to be printed (Prints ' ' if (size < width)
+ * @param precision Total character of number to be printed (prints 0 before number if size of number < precision)
+ * 
+*/
+void print_int_value(int n, int width, int precision)
+{
+	char *p = (char *) malloc(INT_MAX_LENGTH * sizeof(char) + 1); /* +1 for '\0' */
+	char *s = p; // Temporary pointer
+	int size = 0; //!< Used to store number of digits in number
+
+	while (n > 0) {
+		*s++ = n % 10 + '0'; // Converts last digit of number to character and store it in p
+		++size; // Increment size variable as one more digit is occured
+		n /= 10; // Removes the last digit from the number n as we have successfully stored it in p
+	}
+	*s = '\0';
+
+	s = p; // Again point back s to starting of p
+
+	reverse_str(p);
+
+	/*!
+	 * The next two conditions check weather it is required to 
+	 * add blanks before printing the number (ie: width)and is it specified how many
+	 * zeros to be printed before the number is printed (ie: precision)
+	*/
+	if (width > 0 && size < width)
+		for (int i = 0; i < (width - precision); ++i) 
+			put_char(' ');
+
+	if (precision > 0 && precision > size)
+		for (int i = 0; i < (precision - size); ++i)
+			put_char('0');
+
+	/* Prints the number.*/
+	while (*s != '\0')
+		put_char(*s++);
+
+	free(p);
+}
+
+/**
+* @brief The algorithm here is also the same as the `print_int_value` function
+ *
+ * @details
+ * First, the digits before decimal is printed by converting the double 
+ * to int. Then after printed a `.`, the double number is subtracted with
+ * the integer value of the number, leaving us with 0 before the decimal.
+ * Then, we multiply the number with 10 raised to the power precision (
+ * precision means how many digits to be printed after the decimal.)
+ * By default, the precision is 8 if it is not specified.
+ * Then, the remaining number is printed on the screen.
+ * @param dval double number to be printed
+ * @param width similar to width parameter of print_int_value()
+ * @param precision tells the number of digits to be printed after the decimal (By default it is 8)
+ */
+void print_double_value(double dval, int width, int precision)
+{
+	int ndigits = get_number_of_digits((int) dval); // Store number of digits before decimal in dval
+	int reqd_blanks = width - (precision + 1) - ndigits; // Blanks to be printed before printing dval, just to cover the width
+
+	print_int_value((int) dval, reqd_blanks, 0); // Prints the part before decimal
+
+	put_char('.'); // Print decimal
+
+	/*Deletes digits before decimal and makes them zero. For example:
+		if dval = 1923.79022, them this will make dval = 0.79022
+	*/
+	dval = dval - (int) dval;
+
+	dval *= power_of_ten(precision); // Brings precision number of digits after decimal to before decimal
+
+	print_int_value((int) dval, 0, precision); // Prints the remaining number
+}
+
+/**
+ * @details
+* First size of the string is calculated to check whether
+* width and precision are to be taken into account or not.
+* Then, the string is printed in accordingly.
+* @param p pointer to string to be printed
+* @param width if (width > sizeof string) then, blanks will be printed before sting to cover up the width
+* @param precision total characters of the string to be printed (prints the whole string if 0 or greater than size of string)
+*/
+void print_string(char *p, int width, int precision)
+{
+	int size = 0; // Stores number of character in string
+	char *s = p; // Temporary pointer
+
+	/* Calculates size of string p*/
+	while (*s != '\0') { 
+		++size;
+		++s;
+	}
+
+	s = p; // Point s to starting of p
+
+	/* Checks how many characters to be printed.
+		if precision is defined then size variable is changed to precision so that only precision
+		number of characters were printed.
+	*/
+	if (precision != 0 && precision < size)
+		size = precision;
+
+	/* Prints blanks to cover the width if required*/
+	for (int i = 0; i < (width - size); ++i)
+		put_char(' ');
+
+	/* Print the string.*/
+	for (int i = 0; i < size; ++i)
+		put_char(*s++);
+
+}
+
+/**
+* @brief Takes width and precision specified from the format of the string
+* @param p pointer of the format string
+* @param width variable in which width will be stored
+* @param precision variable in which precision will be stored
+* @return character pointer to the current pointer of string p (used to update value of p)
+*/
+char *get_width_and_precision(char *p, Buffer *buffer, int *width, int *precision)
+{
+	/* Skip % if p is pointing to it.*/
+	if (*p == '%')
+		++p;
+
+	/* Calculates the width specified. */
+	while (*p != '.' && is_number(p)) 
+		*width = *width * 10 + (*p++ - '0');
+
+	/* Calculates the precision specified.*/
+	if (*p == '.' /* Since a precision is always specified after a '.'. */) { 
+		while (is_number(++p))
+			*precision = *precision * 10 + (*p - '0'); 
+		unget_ch(p, buffer); // The non number will be stored in `buffer->buffr`
+	}
+	return p;
+}
+
+/**
+ * min_printf is the function same as printf
+ * @param fmt format of string
+ * @param ... arguments passed according to the format
+*/
+void min_printf(char *fmt, ...)
+{
+	va_list ap; // Points to each unnamed arg in turn
+	char *p, *sval; // p will be used to point to fmt and sval will store string value
+	char cval; // Stores character value
+	int ival; // For integer values
+	double dval; // For double or float values
+	va_start(ap, fmt); // Makes ap points to first unnames argument
+
+	/* Initializing the buffer for storing character. */
+	Buffer *buffer = (Buffer *) malloc(sizeof(Buffer));
+	buffer->buf_size = 0; // Initially set buffer size to zero as no character is inserted
+
+	for (p = fmt; *p != '\0'; ++p) {
+
+		/* If p != '%' then the character is printed to screen. */
+		if (*p != '%') {
+			put_char(*p);
+			continue;
+		}
+
+		int width = 0; // Stores width specified
+		int precision = 0; // Stores precision specified
+
+		/* Updates values of width, precision and p. */
+		p = get_width_and_precision(p, buffer, &width, &precision); 
+
+		/* Checks format of next argument.*/
+		switch (get_ch(p, buffer)) {
+			case 'd': // Integer
+				ival = va_arg(ap, int);
+				print_int_value(ival, width, precision);
+				break;
+			case 'c': // Character
+				cval = va_arg(ap, int);
+				put_char(cval);
+				break;
+			case 'f': // Float or Double
+				dval = va_arg(ap, double);
+
+				// If precision is not specified then default value is applied
+				if (precision == 0)
+					precision = PRECISION_FOR_FLOAT;
+				print_double_value(dval, width, precision);
+				break;
+			case 's': // String pointer
+				sval = va_arg(ap, char *);
+				print_string(sval, width, precision);
+				break;
+			default:
+				put_char(*p);
+				break;
+		}
+	}
+	va_end(ap);
+}
+
+#endif /* MIN_PRINTF_H */