kernel_utils/string_help.c at main · podes/kernel_utils · GitHub

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#include <stddef.h>
#include <string.h>
#include <stdint.h>

#include "string_help.h"

size_t strlcpy(char *dest, const char *src, size_t size)
{
    size_t ret = strlen(src);

    if (size) {
        size_t len = (ret >= size) ? size - 1 : ret;
        memcpy(dest, src, len);
        dest[len] = '\0';
    }
    return ret;
}

#ifdef __x86_64__
#define CONFIG_ARCH_HAS_FAST_MULTIPLIER
#endif
typedef uint8_t u8;
typedef uint64_t u64;

/* code from linux kernel */
static void *check_bytes8(const u8 *start, u8 value, unsigned int bytes)
{
	while (bytes) {
		if (*start != value)
			return (void *)start;
		start++;
		bytes--;
	}
	return NULL;
}

/**
 * memchr_inv - Find an unmatching character in an area of memory.
 * @start: The memory area
 * @c: Find a character other than c
 * @bytes: The size of the area.
 *
 * returns the address of the first character other than @c, or %NULL
 * if the whole buffer contains just @c.
 */
void *dlm_memchr_inv(const void *start, int c, size_t bytes)
{
	u8 value = c;
	u64 value64;
	unsigned int words, prefix;

	if (bytes <= 16)
		return check_bytes8(start, value, bytes);

	value64 = value;
#if defined(CONFIG_ARCH_HAS_FAST_MULTIPLIER) && __SIZEOF_LONG__ == 8
	value64 *= 0x0101010101010101ULL;
#elif defined(CONFIG_ARCH_HAS_FAST_MULTIPLIER)
	value64 *= 0x01010101;
	value64 |= value64 << 32;
#else
	value64 |= value64 << 8;
	value64 |= value64 << 16;
	value64 |= value64 << 32;
#endif

	prefix = (unsigned long)start % 8;
	if (prefix) {
		u8 *r;

		prefix = 8 - prefix;
		r = check_bytes8(start, value, prefix);
		if (r)
			return r;
		start += prefix;
		bytes -= prefix;
	}

	words = bytes / 8;

	while (words) {
		if (*(u64 *)start != value64)
			return check_bytes8(start, value, 8);
		start += 8;
		words--;
	}

	return check_bytes8(start, value, bytes % 8);
}