Add first structure and start work on format specifier parser

.gitignore

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+build/*
+*.o
+*.d
+*.user
+.cache/*
+.vscode/*

CMakeLists.txt

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+cmake_minimum_required(VERSION 3.0)
+project(simple-printf)
+
+aux_source_directory("src" SOURCES)
+add_library(${PROJECT_NAME} STATIC ${SOURCES})
+target_include_directories(${PROJECT_NAME} PUBLIC include)
+
+

include/simple-printf/simple-printf.h

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+#ifndef _SIMPLE_PRINTF_H_
+#define _SIMPLE_PRINTF_H_
+
+#include <stddef.h>
+
+#ifndef SIMPLE_PRINTF_ATTR_FORMAT
+#   if ((__GNUC__ > 3) || ((__GNUC__ == 3) && (__GNUC_MINOR__ >= 3)))
+#       define SIMPLE_PRINTF_ATTR_FORMAT(fmt, args) __attribute__((__format__(__printf__, fmt, args)))
+#   else
+#       define SIMPLE_PRINTF_ATTR_FORMAT(fmt, args)
+#   endif
+#else
+#   define SIMPLE_PRINTF_ATTR_FORMAT(fmt, args)
+#endif
+
+/**
+ * @brief Simple implementation of snprintf
+ * 
+ * Supports the following format specifiers:
+ * %d, %i, %s, %u, %z, %c, %x, %X
+ * @param[out] dest Buffer to write result to
+ * @param dest_size Size of @p dest in bytes
+ * @param[in] fmt Format string
+ * @return Number of written bytes. Not including the null terminator.
+ * @return negative in case of an error
+ * @note The resulting output in @p dest will always be null terminated.
+ */
+int simple_snprintf(char *dest, size_t dest_size, const char *fmt, ...) SIMPLE_PRINTF_ATTR_FORMAT(3, 4);
+
+#endif /* _SIMPLE_PRINTF_H_ */

src/simple-printf.c

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+#include <simple-printf/simple-printf.h>
+#include <stddef.h>
+#include <stdbool.h>
+
+enum format_specifier_type {
+	FMT_INVALID = 0,
+	FMT_INTEGER,
+	FMT_UNSIGNED,
+	FMT_STRING,
+	FMT_HEXUINT_CAPITALIZED,
+	FMT_HEXUNIT,
+	FMT_CHAR,
+	FMT_SIZE,
+	FMT_PERCENT,
+};
+
+struct format_specifier {
+	enum format_specifier_type specifier;
+	size_t length; /**< @brief lenght of formatted output.*/
+	bool zero_pad; 
+	size_t length_of_provided_specifier;
+};
+
+static void parse_format_specifier(const char *start, struct format_specifier *result)
+{
+	size_t fmt_len = 1ull;
+	bool keep_parsing = true;
+	bool is_in_number = false;
+	const char *number;
+	size_t num_len = 0;
+	
+	result->specifier = FMT_INVALID;
+	result->zero_pad = 0;
+	result->length_of_provided_specifier = 0;
+	result->length = 0;
+	if (!start)
+		return;
+
+	/* Check if specifier starts with % */
+	if (*start != '%')
+		return;
+
+	start++;
+	while (keep_parsing) {
+		/* Parse the format specifier*/
+		switch (*start) {
+		case '0':
+			if (fmt_len == 1) {
+				result->zero_pad = 1;
+				break;
+			} 
+			/* Fallthru */		
+		case '1':
+		case '2':
+		case '3':
+		case '4':
+		case '5':
+		case '6':
+		case '7':
+		case '8':
+		case '9':
+			/* Number */
+			if (!is_in_number) {
+				/* Start of number */
+				is_in_number = true;
+				number = start;
+				num_len = 0;
+			} else {
+				/* Continue parsing number */
+				num_len++;
+			}
+			break;
+		case 'c':
+			result->specifier = FMT_CHAR;
+			keep_parsing = false;
+			break;
+		case 'z':
+			result->specifier = FMT_SIZE;
+			keep_parsing = false;
+			break;
+		case 'x':
+			result->specifier = FMT_HEXUNIT;
+			keep_parsing = false;
+			break;
+		case 'X':
+			result->specifier = FMT_HEXUINT_CAPITALIZED;
+			keep_parsing = false;
+			break;
+		case 's':
+			result->specifier = FMT_STRING;
+			keep_parsing = false;
+			break;
+		case 'u':
+			result->specifier = FMT_UNSIGNED;
+			keep_parsing = false;
+			break;
+		case 'i': /* Falltrhu */
+		case 'd':
+			result->specifier = FMT_INTEGER;
+			keep_parsing = false;
+			break;
+		case '%':
+			if (fmt_len == 1) {
+				result->specifier = FMT_PERCENT;
+			}
+			keep_parsing = false;
+		default:
+			/* Unrecognized stuff. Abort */
+			keep_parsing = false;
+			break;
+		}
+
+		if (keep_parsing == false) {
+			/* End reached. Check the number */
+			
+		}
+
+		start++;
+		fmt_len++;
+	}
+}
+
+int simple_snprintf(char *dest, size_t dest_size, const char *fmt, ...)
+{
+	int ret = -1;
+	
+	if (!dest || !dest_size || !fmt) {
+		/* Parameter error */
+		return -1000;
+	}
+
+	return ret;
+}
+