From 4aa74dbe2a35a45668b33d688f17b680c2232572 Mon Sep 17 00:00:00 2001
From: EmulatedSeasons <89668582+EmulatedSeasons@users.noreply.github.com>
Date: Sun, 5 May 2024 01:08:00 -0400
Subject: improved makefile somewhat

---
 libc/printf.c | 191 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 191 insertions(+)
 create mode 100644 libc/printf.c

(limited to 'libc/printf.c')

diff --git a/libc/printf.c b/libc/printf.c
new file mode 100644
index 0000000..72a4749
--- /dev/null
+++ b/libc/printf.c
@@ -0,0 +1,191 @@
+#include <limits.h>
+#include <stdbool.h>
+#include <stdarg.h>
+#include <stdio.h>
+#include <string.h>
+#include <stdint.h>
+
+static bool print(const char* data, size_t length) {
+	const unsigned char* bytes = (const unsigned char*) data;
+	for (size_t i = 0; i < length; i++)
+		if (putchar(bytes[i]) == EOF)
+			return false;
+	return true;
+}
+
+// for %d and %x.
+static const char* itoa(unsigned int num, char* str, unsigned int base) {
+	int cou = 0; // nt
+
+    if (num == 0) { // 0
+		str[cou] = '0';
+		str[++cou] = '\0';
+		return str;
+	}
+
+	while (num)
+	{
+		unsigned int rem = (num % base);
+		// brings the number up to ascii 0 + the digit
+		if (rem > 9) {
+			str[cou] = rem + '7'; // 7 = 55 + 10(A) = 65
+		} else {
+			str[cou] = rem + '0';
+		}
+		num /= base;
+		++cou;
+	}
+	
+	// reverse the string
+	for (int i = 0; i < cou; i++) {
+		char temp = str[i];
+		str[i] = str[cou - i - 1]; 
+		str[cou - 1] = temp;
+	}
+
+	str[cou] = '\0';
+	return str;
+}
+
+// have no idea if there's a better way to do this. for %lx
+static const char* itoa_u64(unsigned long long num, char* str, int base) {
+	int cou = 0; // nt
+
+    if (num == 0) { // 0
+		str[cou] = '0';
+		str[++cou] = '\0';
+		return str;
+	}
+
+	while (num)
+	{
+		unsigned long long rem = num % base;
+		// brings the number up to ascii 0 + the digit
+		if (rem > 9) {
+			str[cou] = rem + '7'; // 7 = 55 + 10(A) = 65
+		} else {
+			str[cou] = rem + '0';
+		}
+		num /= base;
+		++cou;
+	}
+	
+	// reverse the string
+	for (int i = 0; i < cou; i++) {
+		char temp = str[i];
+		str[i] = str[cou - i - 1]; 
+		str[cou - 1] = temp;
+	}
+
+	str[cou] = '\0';
+	return str;
+}
+
+int printf(const char* restrict format, ...) {
+	va_list parameters;
+	va_start(parameters, format);
+ 
+	int written = 0;
+
+	while (*format != '\0') {
+		size_t maxrem = INT_MAX - written;
+ 
+		if (format[0] != '%' || format[1] == '%') {
+			if (format[0] == '%')
+				format++;
+			size_t amount = 1;
+			while (format[amount] && format[amount] != '%')
+				amount++;
+			if (maxrem < amount) {
+				// TODO: Set errno to EOVERFLOW.
+				return -1;
+			}
+			if (!print(format, amount))
+				return -1;
+			format += amount;
+			written += amount;
+			continue;
+		}
+
+		const char* format_begun_at = format++;
+
+		if (*format == 'c') {
+			format++;
+			char c = (char) va_arg(parameters, int /* char promotes to int */);
+			if (!maxrem) {
+				// TODO: Set errno to EOVERFLOW.
+				return -1;
+			}
+			if (!print(&c, sizeof(c)))
+				return -1;
+			written++;
+		} else if (*format == 'd') {
+			format++;
+			char str[20]; // probably a long enough buffer
+			unsigned int d = va_arg(parameters, unsigned int);
+			itoa(d, str, 10);
+			size_t len = strlen(str);
+			if (maxrem < len) {
+				// TODO: Set errno to EOVERFLOW.
+				return -1;
+			}
+			if (!print(str, len))
+				return -1;
+			written += len;
+		} else if (*format == 'x') {
+			format++;
+			char str[20]; // probably a long enough buffer
+			unsigned int d = va_arg(parameters, unsigned int);
+			itoa(d, str, 16);
+			size_t len = strlen(str);
+			if (maxrem < len) {
+				// TODO: Set errno to EOVERFLOW.
+				return -1;
+			}
+			if (!print(str, len))
+				return -1;
+			written += len;
+		} else if (*format == 'l') { // for %lx and others that start with l
+			format++;
+			if (*format == 'x') {
+				format++;
+				char str[20]; // probably a long enough buffer
+				unsigned long long d = va_arg(parameters, unsigned long long);
+				itoa_u64(d, str, 16);
+				size_t len = strlen(str);
+				if (maxrem < len) {
+					// TODO: Set errno to EOVERFLOW.
+					return -1;
+				}
+				if (!print(str, len))
+					return -1;
+				written += len;
+			}
+		} else if (*format == 's') {
+			format++;
+			const char* str = va_arg(parameters, const char*);
+			size_t len = strlen(str);
+			if (maxrem < len) {
+				// TODO: Set errno to EOVERFLOW.
+				return -1;
+			}
+			if (!print(str, len))
+				return -1;
+			written += len;
+		} else {
+			format = format_begun_at;
+			size_t len = strlen(format);
+			if (maxrem < len) {
+				// TODO: Set errno to EOVERFLOW.
+				return -1;
+			}
+			if (!print(format, len))
+				return -1;
+			written += len;
+			format += len;
+		}
+	}
+
+	va_end(parameters);
+	return written;
+}
\ No newline at end of file
-- 
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