From 006a196e4adbcc4ca2b537a3f926414948ea4201 Mon Sep 17 00:00:00 2001
From: Bananymous <oskari.alaranta@bananymous.com>
Date: Thu, 24 Apr 2025 01:39:49 +0300
Subject: [PATCH] LibC: optimize strpbrk, str{,c}spn, strtok{,_r}
These matches are now detected with bitmasks instead of looping over the
second string
---
userspace/libraries/LibC/string.cpp | 100 +++++++++++++---------------
1 file changed, 48 insertions(+), 52 deletions(-)
diff --git a/userspace/libraries/LibC/string.cpp b/userspace/libraries/LibC/string.cpp
index a6fea64fb4..905d136c7c 100644
--- a/userspace/libraries/LibC/string.cpp
+++ b/userspace/libraries/LibC/string.cpp
@@ -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];