string.md

String and Memory Utilities

This document covers the freestanding string and memory functions implemented by the kernel. The code is in c_files/src/string.c with declarations in c_files/includes/string.h.

Overview

Since the kernel runs without the C standard library (-nostdlib -nostdinc), commonly-used string and memory functions must be provided manually. These implementations follow standard C semantics where possible.

String Functions

Function	Signature	Description
strlen	unsigned int strlen(const char *str)	Returns the length of a NUL-terminated string (not counting the terminator).
strcpy	char *strcpy(char *dest, const char *src)	Copies src to dest including the NUL terminator. Returns dest.
strncpy	char *strncpy(char *dest, const char *src, unsigned int n)	Copies up to n characters from src to dest. Pads with NUL bytes if src is shorter than n.
strcat	char *strcat(char *dest, const char *src)	Appends src to the end of dest. Returns dest.
strncat	char *strncat(char *dest, const char *src, unsigned int n)	Appends at most n characters from src to dest and NUL-terminates.
strcmp	int strcmp(const char *str1, const char *str2)	Compares two strings lexicographically. Returns 0 if equal, negative if str1 < str2, positive otherwise.
strncmp	int strncmp(const char *str1, const char *str2, unsigned int n)	Like strcmp but compares at most n characters.

Memory Functions

Function	Signature	Description
memset	void *memset(void *dest, int val, unsigned int n)	Fills n bytes of dest with the byte value val.
memcpy	void *memcpy(void *dest, const void *src, unsigned int n)	Copies n bytes from src to dest. Regions must not overlap.
memcmp	int memcmp(const void *ptr1, const void *ptr2, unsigned int n)	Compares n bytes. Returns 0 if identical.

Conversion Functions

Function	Signature	Description
atoi	int atoi(const char *str)	Converts a decimal string to an integer. Supports a leading - sign. Stops at the first non-digit character.
itoa	char *itoa(int value, char *str, int base)	Converts an integer to a string in the given base (2–36). Handles negative values for base 10. Digits above 9 use lowercase letters.

Formatted Output

Function	Signature	Description
sprintf	int sprintf(char *str, const char *format, ...)	Writes formatted output to a string buffer. Returns the number of characters written (excluding NUL).

sprintf Format Specifiers

Specifier	Argument	Output
%c	int (promoted char)	Single character
%d	int	Signed decimal
%x	int	Hexadecimal (lowercase, no 0x prefix)
%s	char*	String (prints (null) for NULL)
%%	—	Literal %

Notes

• All functions use unsigned int for sizes instead of size_t since no standard headers are available.
• sprintf uses GCC's __builtin_va_list for variadic arguments.
• itoa reverses the digit string in-place after generation to produce the correct order.