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LibC: optimize strpbrk, str{,c}spn, strtok{,_r} 

These matches are now detected with bitmasks instead of looping over the
second string
This commit is contained in:
Bananymous 2025-04-24 01:39:49 +03:00
parent 418678466c
commit 006a196e4a
1 changed files with 48 additions and 52 deletions
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100
userspace/libraries/LibC/string.cpp
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@ -282,38 +282,40 @@ char* strstr(const char* haystack, const char* needle)
return nullptr;
}
size_t strcspn(const char* s1, const char* s2)
{
size_t i = 0;
for (; s1[i]; i++)
for (size_t j = 0; s2[j]; j++)
if (s1[i] == s2[j])
return i;
return i;
}
#define CHAR_UCHAR(ch) \
static_cast<unsigned char>(ch)
#define CHAR_BITMASK(str) \
uint32_t bitmask[0x100 / 32] {}; \
for (size_t i = 0; str[i]; i++) \
bitmask[CHAR_UCHAR(str[i]) / 32] |= (1 << (CHAR_UCHAR(str[i]) % 32))
#define CHAR_BITMASK_TEST(ch) \
(bitmask[CHAR_UCHAR(ch) / 32] & (1 << (CHAR_UCHAR(ch) % 32)))
char* strpbrk(const char* s1, const char* s2)
{
CHAR_BITMASK(s2);
for (size_t i = 0; s1[i]; i++)
for (size_t j = 0; s2[j]; j++)
if (s1[i] == s2[j])
return const_cast<char*>(s1 + i);
if (CHAR_BITMASK_TEST(s1[i]))
return const_cast<char*>(&s1[i]);
return nullptr;
}
size_t strspn(const char* s1, const char* s2)
{
size_t i = 0;
for (; s1[i]; i++)
{
bool found = false;
for (size_t j = 0; s2[j] && !found; j++)
if (s1[i] == s2[j])
found = true;
if (!found)
break;
}
return i;
CHAR_BITMASK(s2);
for (size_t i = 0;; i++)
if (s1[i] == '\0' || !CHAR_BITMASK_TEST(s1[i]))
return i;
}
size_t strcspn(const char* s1, const char* s2)
{
CHAR_BITMASK(s2);
for (size_t i = 0;; i++)
if (s1[i] == '\0' || CHAR_BITMASK_TEST(s1[i]))
return i;
}
char* strtok(char* __restrict s, const char* __restrict sep)
@ -324,49 +326,43 @@ char* strtok(char* __restrict s, const char* __restrict sep)
char* strtok_r(char* __restrict str, const char* __restrict sep, char** __restrict state)
{
CHAR_BITMASK(sep);
if (str)
{
while (*str)
{
bool found = false;
for (size_t i = 0; sep[i] && !found; i++)
if (*str == sep[i])
found = true;
if (!found)
break;
str++;
}
if (!*str)
{
*state = nullptr;
return nullptr;
}
*state = str;
}
if (!*state)
if (*state == nullptr)
return nullptr;
str = *state;
for (; *str; str++)
if (!CHAR_BITMASK_TEST(*str))
break;
if (*str == '\0')
{
*state = nullptr;
return nullptr;
}
for (size_t i = 0; str[i]; i++)
{
for (size_t j = 0; sep[j]; j++)
{
if (str[i] == sep[j])
{
str[i] = '\0';
*state = str + i + 1;
return str;
}
}
if (!CHAR_BITMASK_TEST(str[i]))
continue;
str[i] = '\0';
*state = str + i + 1;
return str;
}
*state = nullptr;
return str;
}
#undef CHAR_UCHAR
#undef CHAR_BITMASK
#undef CHAR_BITMASK_TEST
char* strsignal(int signum)
{
static char buffer[128];