string.h File Reference

Minimal string and memory manipulation functions for bare-metal AArch64. More...

#include <stddef.h>

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Functions
void *	memcpy (void *dest, const void *src, size_t size)
	Copies size bytes from memory area src to memory area dest.
int	memcmp (const void *str1, const void *str2, size_t size)
	Compares the first size bytes of memory areas str1 and str2.
void *	memchr (const void *str, int chr, size_t size)
	Scans memory for a specific character.
void *	memmove (void *dest, const void *src, size_t size)
	Copies size bytes from memory area src to memory area dest.
void *	memset (void *s_ptr, int val, size_t size)
	Fills the first size bytes of the memory area pointed to by s_ptr with the constant byte val.
int	memset_s (void *dest, size_t destsz, int byte, size_t count)
	Bounds-checked fill of dest with a constant byte.
char *	strchr (const char *str, int chr)
	Locate the first occurrence of a character in a string.
char *	strrchr (const char *str, int chr)
	Locates the last occurrence of a character in a string.
size_t	strlen (const char *str)
	Calculates the length of a string.
size_t	strnlen (const char *str, size_t maxlen)
	Calculates the length of a string up to a specified maximum.
unsigned long	strtoul (const char *nptr, char **endptr, int base)
	Convert a string to an unsigned long integer.
int	strcmp (const char *lhs, const char *rhs)
	Compare two null-terminated strings.

Detailed Description

Minimal string and memory manipulation functions for bare-metal AArch64.

Provides essential string and memory helpers used by the kernel and linked external libraries in a freestanding runtime environment.

Author

Abhin Parekadan Jose

Date

2026-05-16

Function Documentation

memchr()

void * memchr	(	const void *	str,
		int	chr,
		size_t	size
	)

Scans memory for a specific character.

Searches the first size bytes of the memory area pointed to by str for the first occurrence of chr.

Parameters

str	Pointer to the memory area.
chr	The character to search for (interpreted as an unsigned char).
size	The number of bytes to analyze.

Returns

A pointer to the matching byte, or NULL if the character is not found.

memcmp()

int memcmp	(	const void *	str1,
		const void *	str2,
		size_t	size
	)

Compares the first size bytes of memory areas str1 and str2.

Parameters

str1	Pointer to the first memory block.
str2	Pointer to the second memory block.
size	Number of bytes to compare.

Returns

An integer less than, equal to, or greater than zero if str1 is found, respectively, to be less than, to match, or be greater than str2.

memcpy()

void * memcpy	(	void *	dest,
		const void *	src,
		size_t	size
	)

Copies size bytes from memory area src to memory area dest.

Note

The memory areas must not overlap. Use memmove() if they do.

Parameters

dest	Pointer to the destination array.
src	Pointer to the source of data to be copied.
size	Number of bytes to copy.

Returns

A pointer to the destination dest.

memmove()

void * memmove	(	void *	dest,
		const void *	src,
		size_t	size
	)

Copies size bytes from memory area src to memory area dest.

Note

The memory areas may overlap: copying takes place as though the bytes in src are first copied into a temporary array that does not overlap src or dest.

Parameters

dest	Pointer to the destination array.
src	Pointer to the source of data to be copied.
size	Number of bytes to copy.

Returns

A pointer to the destination dest.

memset()

void * memset	(	void *	s_ptr,
		int	val,
		size_t	size
	)

Fills the first size bytes of the memory area pointed to by s_ptr with the constant byte val.

Parameters

s_ptr	Pointer to the memory area to fill.
val	The byte value to set.
size	Number of bytes to be set to the value.

Returns

A pointer to the memory area s_ptr.

memset_s()

int memset_s	(	void *	dest,
		size_t	destsz,
		int	byte,
		size_t	count
	)

Bounds-checked fill of dest with a constant byte.

Writes count copies of byte into dest after validating that the write fits within destsz. The operation is rejected if dest is NULL, destsz is zero, or count exceeds destsz.

Parameters

dest	Pointer to the memory area to fill.
destsz	Size of the destination buffer, in bytes.
byte	The byte value to write.
count	Number of bytes to set.

Returns

0 on success, or -1 if the arguments fail validation.

strchr()

char * strchr	(	const char *	str,
		int	chr
	)

Locate the first occurrence of a character in a string.

Parameters

str	The string to search.
chr	The character to look for (passed as int, converted to char).

Returns

A pointer to the matched character, or NULL if not found.

strcmp()

int strcmp	(	const char *	lhs,
		const char *	rhs
	)

Compare two null-terminated strings.

Parameters

lhs	The first string to compare.
rhs	The second string to compare.

Returns

• 0 if the strings are equal.
• A negative value if lhs is less than rhs.
• A positive value if lhs is greater than rhs.

strlen()

size_t strlen

(

const char *

str

)

Calculates the length of a string.

Scans the string str until the terminating null byte ('\0') is found.

Parameters

str	Pointer to the null-terminated string.

Returns

The number of characters in the string, excluding the null byte.

strnlen()

size_t strnlen	(	const char *	str,
		size_t	maxlen
	)

Calculates the length of a string up to a specified maximum.

Similar to strlen(), but scans at most maxlen bytes.

Parameters

str	Pointer to the string.
maxlen	The maximum number of bytes to examine.

Returns

The number of characters in the string if less than maxlen; otherwise, maxlen.

strrchr()

char * strrchr	(	const char *	str,
		int	chr
	)

Locates the last occurrence of a character in a string.

Scans the string str to find the last occurrence of character chr.

Parameters

str	Pointer to the null-terminated string.
chr	The character to search for.

Returns

A pointer to the last occurrence of the character, or NULL if not found.

strtoul()

unsigned long strtoul	(	const char *	nptr,
		char **	endptr,
		int	base
	)

Convert a string to an unsigned long integer.

Parameters

nptr	The string containing the representation of the number.
endptr	Pointer to the character that stopped the scan.
base	The radix to use (e.g., 10 for decimal, 16 for hex).

Returns

The converted value.