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libc: add memchr(), strnlen(), strdup(), and rename memclr() to bzero()

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This commit is contained in:
apio 2022-10-15 12:18:37 +02:00
parent 523e88e5a9
commit 94a6336e4d
2 changed files with 37 additions and 44 deletions
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13
libs/libc/include/string.h
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@ -15,12 +15,18 @@ extern "C"
/* Sets n bytes of buf to c, cast to a character. */
void* memset(void* buf, int c, size_t n);
/* Clears n bytes of buf. */
void* memclr(void* buf, size_t n);
/* Searches for the character c in n bytes of buf. */
void* memchr(const void* buf, int c, size_t n);
/* Returns a heap-allocated copy of the string str. Should be freed when it is not used anymore. */
char* strdup(const char* str);
/* Returns the length of the string str. */
size_t strlen(const char* str);
/* Returns the length of the string str, while examining at most max bytes of str. */
size_t strnlen(const char* str, size_t max);
/* Copies the string src into dest. This function is unsafe, use strncpy instead. */
__lc_deprecated("strcpy is unsafe and should not be used; use strncpy instead") char* strcpy(char* dest,
const char* src);
@ -41,6 +47,9 @@ extern "C"
/* Returns the error string associated with the error number err. */
char* strerror(int err);
/* Clears n bytes of buf. */
void* bzero(void* buf, size_t n);
#ifdef __cplusplus
}
#endif

68
libs/libc/src/string.cpp
View File

@ -1,5 +1,5 @@
#include <errno.h>
#include <luna.h>
#include <stdlib.h>
#include <string.h>
extern "C"
@ -16,6 +16,23 @@ extern "C"
return buf;
}
void* memchr(const void* buf, int c, size_t n)
{
const char* s = (const char*)buf;
for (; n && *s != (char)c; s++, n--)
;
if (n) return (void*)(const_cast<char*>(s));
return NULL;
}
char* strdup(const char* str)
{
size_t len = strlen(str);
char* dest = (char*)malloc(len + 1);
if (!dest) return dest;
return (char*)memcpy(dest, str, len + 1);
}
size_t strlen(const char* str)
{
const char* i = str;
@ -24,6 +41,12 @@ extern "C"
return (i - str);
}
size_t strnlen(const char* str, size_t max)
{
char* p = (char*)memchr(str, 0, max);
return p ? p - str : max;
}
char* strcpy(char* dest, const char* src)
{
memcpy(dest, src, strlen(src) + 1);
@ -68,48 +91,9 @@ extern "C"
return NULL;
}
void* memclr(void* buf, size_t n)
void* bzero(void* buf, size_t n)
{
// "i" is our counter of how many bytes we've cleared
size_t i;
// find out if "m_start" is aligned on a SSE_XMM_SIZE boundary
if ((size_t)buf & (15))
{
i = 0;
// we need to clear byte-by-byte until "m_start" is aligned on an SSE_XMM_SIZE boundary
// ... and lets make sure we don't copy 'too' many bytes (i < m_count)
while (((size_t)buf + i) & (15) && i < n)
{
asm("stosb;" ::"D"((size_t)buf + i), "a"(0));
i++;
}
}
else
{
// if "m_start" was aligned, set our count to 0
i = 0;
}
// clear 64-byte chunks of memory (4 16-byte operations)
for (; i + 64 <= n; i += 64)
{
asm volatile(" pxor %%xmm0, %%xmm0; " // set XMM0 to 0
" movdqa %%xmm0, 0(%0); " // move 16 bytes from XMM0 to %0 + 0
" movdqa %%xmm0, 16(%0); "
" movdqa %%xmm0, 32(%0); "
" movdqa %%xmm0, 48(%0); " ::"r"((size_t)buf + i));
}
// copy the remaining bytes (if any)
asm(" rep stosb; " ::"a"((size_t)(0)), "D"(((size_t)buf) + i), "c"(n - i));
// "i" will contain the total amount of bytes that were actually transfered
i += n - i;
// we return "m_start" + the amount of bytes that were transfered
return (void*)(((size_t)buf) + i);
return memset(buf, 0, n);
}
#pragma GCC push_options