xnu-792.25.20.tar.gz

[apple/xnu.git] / osfmk / i386 / bcopy.s

diff --git a/osfmk/i386/bcopy.s b/osfmk/i386/bcopy.s
index b592689e8b266762a547c643c48d091a30622dbc..fe9b9b883b4b7f874def98dea8d0d86a2dd9c0ce 100644 (file)
--- a/osfmk/i386/bcopy.s
+++ b/osfmk/i386/bcopy.s
@@ -109,3 +109,54 @@ ENTRY(bcopy16)
        popl    %edi
        ret     
 
+       
+ /*
+  * Based on NetBSD's bcopy.S from their libc.
+  * bcopy(src, dst, cnt)
+  *  ws@tools.de     (Wolfgang Solfrank, TooLs GmbH) +49-228-985800
+  */
+ENTRY(bcopy)
+               pushl   %esi
+               pushl   %edi
+               movl    12(%esp),%esi
+               movl    16(%esp),%edi
+               movl    20(%esp),%ecx
+
+               movl    %edi,%edx
+               subl    %esi,%edx
+               cmpl    %ecx,%edx                       /* overlapping && src < dst? */
+                       movl    %ecx,%edx
+               jb      1f
+
+               shrl    $2,%ecx                         /* copy by 32-bit words */
+               cld                                     /* nope, copy forwards */
+               rep
+               movsl
+               movl    %edx,%ecx
+               andl    $3,%ecx                         /* any bytes left? */
+               rep
+               movsb
+               popl    %edi
+               popl    %esi
+               ret
+
+
+1:
+               addl    %ecx,%edi                       /* copy backwards */
+               addl    %ecx,%esi
+               decl    %edi
+               decl    %esi
+               andl    $3,%ecx                         /* any fractional bytes? */
+               std
+               rep
+               movsb
+               movl    %edx,%ecx                   /* copy remainder by 32-bit words */
+               shrl    $2,%ecx
+               subl    $3,%esi
+               subl    $3,%edi
+               rep
+               movsl
+               popl    %edi
+               popl    %esi
+               cld
+               ret