First draft refactoring the [string first] functionality.

1 files changed, 84 insertions, 0 deletions

diff --git a/generic/tclStringObj.c b/generic/tclStringObj.c
index b486106..6e1529c 100644
--- a/generic/tclStringObj.c
+++ b/generic/tclStringObj.c
@@ -2841,6 +2841,90 @@ TclStringCatObjv(
 /*
  *---------------------------------------------------------------------------
  *
+ * TclStringFind --
+ *
+ *	Implements the [string first] operation.
+ *
+ * Results:
+ *	If needle is found as a substring of haystack, the index of the
+ *	first instance of such a find is returned.  If needle is not present
+ *	as a substring of haystack, -1 is returned.
+ *
+ * Side effects:
+ *	needle and haystack may have their Tcl_ObjType changed.
+ *
+ *---------------------------------------------------------------------------
+ */
+
+int
+TclStringFind(
+    Tcl_Obj *needle,
+    Tcl_Obj *haystack,
+    unsigned int start)
+{
+    int ln, lh;
+
+    if (TclIsPureByteArray(needle) && TclIsPureByteArray(haystack)) {
+	unsigned char *end, *try, *bh;
+	unsigned char *bn = Tcl_GetByteArrayFromObj(needle, &ln);
+
+	if (ln == 0) {
+	    /*
+	     * 	We don't find empty substrings.  Bizarre!
+	     *
+	     * 	TODO: When we one day make this a true substring
+	     * 	finder, change this to "return 0"
+	     */
+	    return -1;
+	}
+
+	bh = Tcl_GetByteArrayFromObj(haystack, &lh);
+	end = bh + lh;
+
+	try = bh + start;
+	while (try + ln <= end) {
+	    try = memchr(try, bn[0], end - try);
+
+	    if (try == NULL) {
+		return -1;
+	    }
+	    if (0 == memcmp(try+1, bn+1, ln-1)) {
+		return (try - bh);
+	    }
+	    try++;
+	}
+	return -1;
+    }
+
+    /* TODO: Detect and optimize case with single byte chars only */
+
+    {
+	Tcl_UniChar *try, *end, *uh;
+	Tcl_UniChar *un = Tcl_GetUnicodeFromObj(needle, &ln);
+
+	if (ln == 0) {
+	    /* See above */
+	    return -1;
+	}
+
+	uh = Tcl_GetUnicodeFromObj(haystack, &lh);
+	end = uh + lh;
+
+	try = uh + start;
+	while (try + ln <= end) {
+	    if ((*try == *un)
+		    && (0 == memcmp(try+1, un+1, (ln-1)*sizeof(Tcl_UniChar)))) {
+		return (try - uh);
+	    }
+	    try++;
+	}
+	return -1;
+    }
+}
+
+/*
+ *---------------------------------------------------------------------------
+ *
  * TclStringObjReverse --
  *
  *	Implements the [string reverse] operation.