ft_mem* and ft_strlen optimization

1 files changed, 37 insertions, 7 deletions

diff --git a/src/mem/ft_memchr.c b/src/mem/ft_memchr.c
index 4fd8689..54780fe 100644
--- a/src/mem/ft_memchr.c
+++ b/src/mem/ft_memchr.c
@@ -12,15 +12,45 @@
 
 #include "libft.h"
 
+/*
+** Determining if a long word contain byte n
+**
+** xor all bytes with n, then check for zero byte like in ft_strlen.
+*/
+
+#define HIMAGIC 0x8080808080808080L
+#define LOMAGIC 0x0101010101010101L
+
 void	*ft_memchr(const void *s, int c, size_t n)
 {
-	size_t		i;
-	t_ftbyte	*cast_s;
+	uint64_t	buf;
+	uint64_t	lw;
 
-	cast_s = (t_ftbyte*)s;
-	i = -1;
-	while (++i < n)
-		if (cast_s[i] == (unsigned char)c)
-			return (cast_s + i);
+	c = (uint8_t)c;
+	while (((uint64_t)s & 0b111) != 0)
+	{
+		n--;
+		if (*(uint8_t*)s == (uint8_t)c)
+			return ((uint8_t*)s);
+		s++;
+	}
+	buf = (uint64_t)c | (uint64_t)c << 8 | (uint64_t)c << 16
+		| (uint64_t)c << 24 | (uint64_t)c << 32 | (uint64_t)c << 40
+		| (uint64_t)c << 48 | (uint64_t)c << 56;
+	while (n >= 8)
+	{
+		lw = *(uint64_t*)s ^ buf;
+		if ((lw - LOMAGIC) & ~lw & HIMAGIC)
+			break;
+		n -= 8;
+		s += 8;
+	}
+	while (n > 0)
+	{
+		if (*(uint8_t*)s == (uint8_t)c)
+			return ((uint8_t*)s);
+		n--;
+		s++;
+	}
 	return (NULL);
 }