Changeset 6b080e54 in mainline

Timestamp:

2008-12-23T16:35:31Z (16 years ago)

Author:

Jiri Svoboda <jirik.svoboda@…>

Branches:

lfn, master, serial, ticket/834-toolchain-update, topic/msim-upgrade, topic/simplify-dev-export

Children:

7a817d00

Parents:

47acd58

Message:

Faster memset() implementation in C library.

File:

• uspace/lib/libc/generic/string.c (modified) (4 diffs)

uspace/lib/libc/generic/string.c

@@ -43 +43 @@
 #include <malloc.h>
 
-/* Dummy implementation of mem/ functions */
-
-void *memset(void *s, int c, size_t n)
-{
-        char *os = s;
-        
-        while (n--)
-                *(os++) = c;
-        
-        return s;
+/** Fill memory block with a constant value. */
+void *memset(void *dest, int b, size_t n)
+{
+        char *pb;
+        unsigned long *pw;
+        size_t word_size;
+        size_t n_words;
+
+        unsigned long pattern;
+        size_t i;
+        size_t fill;
+
+        /* Fill initial segment. */
+        word_size = sizeof(unsigned long);
+        fill = word_size - ((uintptr_t) dest & (word_size - 1));
+        if (fill > n) fill = n;
+
+        pb = dest;
+
+        i = fill;
+        while (i-- != 0)
+                *pb++ = b;
+
+        /* Compute remaining size. */
+        n -= fill;
+        if (n == 0) return dest;
+
+        n_words = n / word_size;
+        n = n % word_size;
+        pw = (unsigned long *) pb;
+
+        /* Create word-sized pattern for aligned segment. */
+        pattern = 0;
+        i = word_size;
+        while (i-- != 0)
+                pattern = (pattern << 8) | (uint8_t) b;
+
+        /* Fill aligned segment. */
+        i = n_words;
+        while (i-- != 0)
+                *pw++ = pattern;
+
+        pb = (char *) pw;
+
+        /* Fill final segment. */
+        i = n;
+        while (i-- != 0)
+                *pb++ = b;
+
+        return dest;
 }
 
@@ -115 +155 @@
 
         i = fill;
-        while (i-- > 0)
+        while (i-- != 0)
                 *dstb++ = *srcb++;
 
@@ -133 +173 @@
         /* "Fast" copy. */
         i = n_words;
-        while (i-- > 0)
+        while (i-- != 0)
                 *dstw++ = *srcw++;
 
@@ -144 +184 @@
 
         i = n;
-        while (i-- > 0)
+        while (i-- != 0)
                 *dstb++ = *srcb++;