huntedbytheirsandSisyphus
b9f8d9bf19
Real string core and process teardown; thin read/write/close/getpid/_exit syscall wrappers; the rest follows the stub convention (documented error return, errno = ENOSYS, TODO). syscall.c is the only kernel ABI surface; crt0.S is the static entry point, kept out of libc.a. Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent) Co-authored-by: Sisyphus <[email protected]>
106 lines
2.1 KiB
C
106 lines
2.1 KiB
C
/*
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* string.c — real, minimal implementations of the memory/string core.
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*
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* Byte-at-a-time on purpose: for the sizes Null Linux deals with, and for
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* the goal of keeping the code obviously correct, word-at-a-time tricks
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* are not worth the branch soup. If profiling ever says otherwise, the
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* benchmark suite will say so (see benchmarks/).
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*/
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#include <string.h>
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size_t strlen(const char *s)
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{
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const char *p = s;
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while (*p)
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p++;
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return (size_t)(p - s);
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}
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int strcmp(const char *a, const char *b)
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{
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while (*a && *a == *b) {
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a++;
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b++;
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}
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return (unsigned char)*a - (unsigned char)*b;
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}
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int strncmp(const char *a, const char *b, size_t n)
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{
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for (; n && *a && *a == *b; n--, a++, b++)
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;
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if (n == 0)
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return 0;
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return (unsigned char)*a - (unsigned char)*b;
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}
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char *strcpy(char *dst, const char *src)
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{
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char *d = dst;
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while ((*d++ = *src++))
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;
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return dst;
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}
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char *strncpy(char *dst, const char *src, size_t n)
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{
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char *d = dst;
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while (n && *src) {
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*d++ = *src++;
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n--;
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}
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while (n--)
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*d++ = '\0';
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return dst;
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}
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void *memcpy(void *restrict dst, const void *restrict src, size_t n)
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{
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unsigned char *d = dst;
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const unsigned char *s = src;
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while (n--)
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*d++ = *s++;
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return dst;
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}
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void *memmove(void *dst, const void *src, size_t n)
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{
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unsigned char *d = dst;
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const unsigned char *s = src;
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if ((size_t)(d - s) >= n) {
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/* No overlap (or exact): copy forward. */
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while (n--)
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*d++ = *s++;
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} else {
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/* Overlap: copy backward. */
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d += n;
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s += n;
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while (n--)
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*--d = *--s;
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}
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return dst;
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}
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int memcmp(const void *a, const void *b, size_t n)
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{
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const unsigned char *x = a;
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const unsigned char *y = b;
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while (n--) {
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if (*x != *y)
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return *x - *y;
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x++;
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y++;
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}
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return 0;
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}
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void *memset(void *dst, int c, size_t n)
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{
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unsigned char *d = dst;
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while (n--)
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*d++ = (unsigned char)c;
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return dst;
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}
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