#ifndef VLIBC_STRING_H
#define VLIBC_STRING_H

/*
 * vlibc — <string.h>.
 *
 * String and memory functions, gated by the active compatibility profile
 * (see include/vlibc/features.h). Levels are cumulative:
 *
 *   Level 1 (onlyposix): ISO C core — memcpy, memmove, memset, strlen, strcmp.
 *   Level 2 (muslmimic): BSD extensions — strlcpy, strlcat.
 *   Level 3 (muslext):   GNU extensions — strcasestr.
 *
 * This header includes <vlibc/features.h> itself, so the gates below always
 * see the configured VLIBC_LEVEL even when the caller included no vlibc
 * header first, and <stddef.h> for size_t.
 */

#include <vlibc/features.h>

#include <stddef.h>

#ifdef __cplusplus
extern "C" {
#endif

/* Level 1: ISO C core (always present). */

/*
 * Return the length of s, excluding the terminating NUL.
 * pure: reads memory, no side effects.
 */
__attribute__((pure)) size_t
strlen(const char *s);

/*
 * Compare the strings lhs and rhs; return negative, zero, or positive when
 * lhs is less than, equal to, or greater than rhs.
 * pure: reads memory, no side effects.
 */
__attribute__((pure)) int
strcmp(const char *lhs, const char *rhs);

/*
 * Copy n bytes from src to dst. The regions must not overlap (restrict).
 * No intent attribute: it writes memory.
 */
void *
memcpy(void *restrict dst, const void *restrict src, size_t n);

/*
 * Copy n bytes from src to dst. The regions may overlap, so the parameters
 * are deliberately not restrict.
 * No intent attribute: it writes memory.
 */
void *
memmove(void *dst, const void *src, size_t n);

/*
 * Fill n bytes at dst with c (converted to unsigned char).
 * No intent attribute: it writes memory.
 */
void *
memset(void *dst, int c, size_t n);

#if VLIBC_LEVEL >= 2
/* Level 2 (muslmimic): BSD extensions. */

/*
 * Copy at most size - 1 bytes from src to dst and NUL-terminate the result;
 * return strlen(src). No NUL is written when size is 0.
 * No intent attribute: it writes memory.
 */
size_t
strlcpy(char *dst, const char *src, size_t size);

/*
 * Append src to dst, NUL-terminating within size bytes; return the length of
 * the string that would have been created without truncation.
 * No intent attribute: it writes memory.
 */
size_t
strlcat(char *dst, const char *src, size_t size);
#endif /* VLIBC_LEVEL >= 2 */

#if VLIBC_LEVEL >= 3
/* Level 3 (muslext): GNU extensions. */

/*
 * Return a pointer to the first case-insensitive (ASCII fold) occurrence of
 * needle in haystack, or NULL if absent; an empty needle matches haystack.
 * pure: reads memory, no side effects.
 */
__attribute__((pure)) char *
strcasestr(const char *haystack, const char *needle);
#endif /* VLIBC_LEVEL >= 3 */

#ifdef __cplusplus
}
#endif

#endif /* VLIBC_STRING_H */