Changes from Version 1 of FindingFirstLetterWithAsmExample/D2

Author:

Andrej08 (IP: 78.2.39.16)

Timestamp:

09/07/10 02:36:40 (14 years ago)

Comment:

--

FindingFirstLetterWithAsmExample/D2

@@ +1 @@
+= Asm code for finding first occurrence of letter in string =
+
+''Part of'' TutorialIntermediate
+
+== Description ==
+
+More or less equivalent to std.string.find. (also similar to C-RTL for strchr except finds count offset rather than char*). 
+
+Demonstrates reference of local char[] variable, repne, scasb, etc.
+
+== Example ==
+
+{{{
+#!d
+/*
+ *  Copyright (C) 2004 by Digital Mars, www.digitalmars.com
+ *  Written by Lynn Allan
+ *  This software is provided 'as-is' by a rusty asm-486 programmer.
+ *  Released to public domain.
+ *
+ * Compile with: dmd test.d (uses dmd ver 2.046)
+ */
+
+import std.stdio;
+import std.string;
+
+void main()
+{
+    string searchString = "The quick brown fox jumped over the lazy dog.";
+    //                     00000000001111111111222222222233333333334444
+    //                     01234567890123456789012345678901234567890123
+    immutable(char)* pss = &searchString[0]; // searchString[0];
+    uint foundOffset = indexOf(searchString, 'z');
+    uint zCode = 'z';
+    uint len = searchString.length;
+    writefln("z found at: %s", foundOffset);
+    uint xCode = 'x';
+    foundOffset = indexOf(searchString, 'x');
+    len = searchString.length;
+    writefln("x found at: %s", foundOffset);
+
+    asm 
+    {
+        cld;
+        mov   ECX,len;
+        mov   EAX,zCode;
+        mov   EDI,pss;
+        repne;
+        scasb;
+        mov   EBX,len;
+        sub   EBX,ECX;
+        dec   EBX;
+        mov   foundOffset,EBX;
+    }
+    writefln("z found at: %s", foundOffset);
+    assert(foundOffset == 38);
+
+    asm 
+    {
+        cld;
+        mov   ECX,len;
+        mov   EAX,xCode;
+        mov   EDI,pss;
+        repne;
+        scasb;
+        mov   EBX,len;
+        sub   EBX,ECX;
+        dec   EBX;
+        mov   foundOffset,EBX;
+    }
+    writefln("x found at: %s", foundOffset);
+    assert(foundOffset == 18);
+}
+
+
+}}}