x-stdlib.h File Reference

C standard library replacements. More...

#include "x-sys.h"

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Functions
Standard Library Replacements
int	x_lib_abs (int i)
void *	x_lib_memcpy (void *p_dest, const void *p_src, size_t n)
void *	x_lib_memset (void *p_dest, int byte, size_t size)
char *	x_lib_strchr (const char *p_str, int c)
int	x_lib_strcmp (const char *p_str1, const char *p_str2)
size_t	x_lib_strlen (const char *p_str)
int	x_lib_strncmp (const char *p_str1, const char *p_str2, size_t n)
char *	x_lib_strndup (const char *p_str, size_t size)

Detailed Description

C standard library replacements.

Stand-ins for standard C library functions, for builds where the stdlib is not available (freestanding targets, embedders that supply their own runtime). When X_USE_STDLIB is defined each function is a light wrapper delegating to the real one; otherwise the self-contained implementation is used.

The C standard owns everything about these functions: the semantics, and the types in the prototypes – plain char/void/int/ size_t, never the x layer's typedefs. The x_lib_ prefix is the one deliberate difference: it lets the replacements coexist with a real libc in the same link. General-purpose helpers with their own contracts live in x-lib.h, not here.

Author

Jon Ruttan (jonru.nosp@m.ttan.nosp@m.@gmai.nosp@m.l.co.nosp@m.m)

Copyright

2021 Jon Ruttan @license MIT No Attribution (MIT-0)

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Function Documentation

x_lib_abs()

int x_lib_abs

(

int

i

)

Compute the absolute value of an integer.

Compute the absolute value of an integer.

Parameters

i	The integer value.

Returns

The absolute value of i.

x_lib_memcpy()

void * x_lib_memcpy	(	void *	p_dest,
		const void *	p_src,
		size_t	size
	)

Copy bytes from a source buffer to a destination buffer.

Copy bytes from a source buffer to a destination buffer.

Parameters

p_dest	Pointer to the destination buffer.
p_src	Pointer to the source buffer.
size	Number of bytes to copy.

Returns

Pointer to p_dest.

x_lib_memset()

void * x_lib_memset	(	void *	p_dest,
		int	byte,
		size_t	size
	)

Fill a memory region with a constant byte.

Fill a memory region with a constant byte.

Parameters

p_dest	Pointer to the destination buffer.
byte	The byte value to fill with.
size	Number of bytes to set.

Returns

Pointer to p_dest.

x_lib_strchr()

char * x_lib_strchr	(	const char *	p_str,
		int	c
	)

Locate the first occurrence of a character in a string.

Locate the first occurrence of a character in a string.

c is converted to char before comparing, and the terminating NUL is part of the string (C99 7.24.5.2): searching for '\0' returns the terminator.

Parameters

p_str	The string to search.
c	The character to find (as an int).

Returns

Pointer to the first occurrence, or NULL if not found.

x_lib_strcmp()

int x_lib_strcmp	(	const char *	p_str1,
		const char *	p_str2
	)

Compare two null-terminated strings.

Compare two null-terminated strings.

Bytes compare as unsigned char (C99 7.24.4), independent of the platform's plain-char signedness.

Parameters

p_str1	First string.
p_str2	Second string.

Returns

Negative, zero, or positive value indicating ordering.

x_lib_strlen()

size_t x_lib_strlen

(

const char *

p_str

)

Calculate the length of a null-terminated string.

Calculate the length of a null-terminated string.

Note

This function does not handle wide characters.

Parameters

p_str

The string to measure.

Returns

The length in bytes, excluding the null terminator.

x_lib_strncmp()

int x_lib_strncmp	(	const char *	p_str1,
		const char *	p_str2,
		size_t	n
	)

Compare two strings up to a maximum number of characters.

Compare two strings up to a maximum of n characters.

Bytes compare as unsigned char (C99 7.24.4); n == 0 compares nothing and returns 0.

Parameters

p_str1	First string.
p_str2	Second string.
n	Maximum number of characters to compare.

Returns

Negative, zero, or positive value indicating ordering.

x_lib_strndup()

char * x_lib_strndup	(	const char *	p_str,
		size_t	size
	)

Duplicate at most size characters of a string (POSIX.1-2008).

Duplicate at most size characters of a string.

The copy stops at the first NUL or after size characters, whichever comes first, and is always NUL-terminated; at most size source bytes are read.

Parameters

p_str	The source string.
size	Maximum number of characters to copy.

Returns

Pointer to the new string, or NULL on allocation failure.