Changeset 87186 in vbox for trunk/src/VBox/Runtime/common/asm

Timestamp:

Jan 6, 2021 12:47:49 PM (4 years ago)

Author:

vboxsync

svn:sync-xref-src-repo-rev:

142117

Message:

IPRT: Added generic ASMMemFirstNonZero C implementations. bugref:9898

File:

• trunk/src/VBox/Runtime/common/asm/ASMMemFirstNonZero-generic.cpp (copied) (copied from trunk/src/VBox/Runtime/common/asm/ASMMemFirstMismatchingU8-generic.cpp ) (1 diff)

trunk/src/VBox/Runtime/common/asm/ASMMemFirstNonZero-generic.cpp

@@ -33 +33 @@
 
 
-DECLASM(void *) ASMMemFirstMismatchingU8(void const RT_FAR *pv, size_t cb, uint8_t u8) RT_NOTHROW_DEF
+DECLASM(void RT_FAR *) ASMMemFirstNonZero(void const RT_FAR *pv, size_t cb) RT_NOTHROW_DEF
 {
     uint8_t const *pb = (uint8_t const RT_FAR *)pv;
+
+    /*
+     * If we've got a large buffer to search, do it in larger units.
+     */
+    if (cb >= sizeof(size_t) * 2)
+    {
+        /* Align the pointer: */
+        while ((uintptr_t)pb & (sizeof(size_t) - 1))
+        {
+            if (RT_LIKELY(*pb == 0))
+            { /* likely */ }
+            else
+                return (void RT_FAR *)pb;
+            cb--;
+            pb++;
+        }
+
+        /* Scan in size_t sized words: */
+        while (   cb >= sizeof(size_t)
+               && *(size_t *)pb == 0)
+        {
+            pb += sizeof(size_t);
+            cb -= sizeof(size_t);
+        }
+    }
+
+    /*
+     * Search byte by byte.
+     */
     for (; cb; cb--, pb++)
-        if (RT_LIKELY(*pb == u8))
+        if (RT_LIKELY(*pb == 0))
         { /* likely */ }
         else
-            return (void *)pb;
+            return (void RT_FAR *)pb;
+
     return NULL;
 }