Index: generic/tclTestObj.c
==================================================================
--- generic/tclTestObj.c
+++ generic/tclTestObj.c
@@ -23,10 +23,11 @@
 #else
 #   include "tclTomMath.h"
 #endif
 #include "tclStringRep.h"
 
+#include <assert.h>
 
 /*
  * Forward declarations for functions defined later in this file:
  */
 
@@ -40,10 +41,11 @@
 static Tcl_ObjCmdProc	TestindexobjCmd;
 static Tcl_ObjCmdProc	TestintobjCmd;
 static Tcl_ObjCmdProc	TestlistobjCmd;
 static Tcl_ObjCmdProc	TestobjCmd;
 static Tcl_ObjCmdProc	TeststringobjCmd;
+static Tcl_ObjCmdProc	TestbigdataCmd;
 
 #define VARPTR_KEY "TCLOBJTEST_VARPTR"
 #define NUMBER_OF_OBJECT_VARS 20
 
 static void VarPtrDeleteProc(void *clientData, TCL_UNUSED(Tcl_Interp *))
@@ -114,10 +116,12 @@
 	    NULL, NULL);
     Tcl_CreateObjCommand(interp, "testlistobj", TestlistobjCmd,
 	    NULL, NULL);
     Tcl_CreateObjCommand(interp, "testobj", TestobjCmd, NULL, NULL);
     Tcl_CreateObjCommand(interp, "teststringobj", TeststringobjCmd,
+	    NULL, NULL);
+    Tcl_CreateObjCommand(interp, "testbigdata", TestbigdataCmd,
 	    NULL, NULL);
     return TCL_OK;
 }
 
 /*
@@ -1516,10 +1520,139 @@
     }
 
     return TCL_OK;
 }
 
+/*
+ *------------------------------------------------------------------------
+ *
+ * TestbigdataCmd --
+ *
+ *    Implements the Tcl command testbigdata
+ *	testbigdata string ?LEN? ?SPLIT?
+ *      testbigdata bytearray ?LEN? ?SPLIT?
+ *    If no arguments given, returns the pattern used to generate strings.
+ *    If SPLIT is specified, the character at that position is set to "X".
+ *
+ * Results:
+ *    TCL_OK    - Success.
+ *    TCL_ERROR - Error.
+ *
+ * Side effects:
+ *    Interpreter result holds result or error message.
+ *
+ *------------------------------------------------------------------------
+ */
+static int
+TestbigdataCmd (
+    ClientData notUsed,
+    Tcl_Interp *interp,    /* Current interpreter. */
+    int objc,              /* Number of arguments. */
+    Tcl_Obj *const objv[]) /* Argument objects. */
+{
+    static const char *const subcmds[] = {
+	   "string", "bytearray", "list", NULL
+    };
+    enum options {
+	   BIGDATA_STRING, BIGDATA_BYTEARRAY, BIGDATA_LIST
+    } idx;
+    char *s;
+    unsigned char *p;
+    Tcl_WideInt i, len, split;
+    Tcl_DString ds;
+    Tcl_Obj *objPtr;
+#define PATTERN_LEN 10
+    Tcl_Obj *patternObjs[PATTERN_LEN];
+
+    if (objc < 2 || objc > 4) {
+	Tcl_WrongNumArgs(interp, 1, objv, "command ?len?");
+	return TCL_ERROR;
+    }
+    if (Tcl_GetIndexFromObj(interp, objv[1], subcmds, "option", 0,
+	    &idx) != TCL_OK) {
+	return TCL_ERROR;
+    }
+    split = -1;
+    if (objc == 2) {
+	len = PATTERN_LEN;
+    } else {
+	if (Tcl_GetWideIntFromObj(interp, objv[2], &len) != TCL_OK) {
+	    return TCL_ERROR;
+	}
+	if (objc == 4) {
+	    if (Tcl_GetWideIntFromObj(interp, objv[3], &split) != TCL_OK) {
+		return TCL_ERROR;
+	    }
+	    if (split >= len) {
+		split = len - 1; /* Last position */
+	    }
+	}
+    }
+    /* Need one byte for nul terminator */
+    Tcl_WideInt limit =
+	sizeof(Tcl_Size) == sizeof(Tcl_WideInt) ? WIDE_MAX-1 : INT_MAX-1;
+    if (len < 0 || len > limit) {
+	Tcl_SetObjResult(
+	    interp,
+	    Tcl_ObjPrintf(
+		"%s is greater than max permitted length %" TCL_LL_MODIFIER "d",
+		Tcl_GetString(objv[2]),
+		limit));
+	return TCL_ERROR;
+    }
+
+    switch (idx) {
+    case BIGDATA_STRING:
+	Tcl_DStringInit(&ds);
+	Tcl_DStringSetLength(&ds, len);/* Also stores \0 at index len+1 */
+	s = Tcl_DStringValue(&ds);
+	for (i = 0; i < len; ++i) {
+	    s[i] = '0' + (i % PATTERN_LEN);
+	}
+	if (split >= 0) {
+	    assert(split < len);
+	    s[split] = 'X';
+	}
+	Tcl_DStringResult(interp, &ds);
+	break;
+    case BIGDATA_BYTEARRAY:
+	objPtr = Tcl_NewByteArrayObj(NULL, len);
+	p = Tcl_GetByteArrayFromObj(objPtr, &len);
+	for (i = 0; i < len; ++i) {
+	    p[i] = '0' + (i % PATTERN_LEN);
+	}
+	if (split >= 0) {
+	    assert(split < len);
+	    p[split] = 'X';
+	}
+	Tcl_SetObjResult(interp, objPtr);
+	break;
+    case BIGDATA_LIST:
+	for (i = 0; i < PATTERN_LEN; ++i) {
+	    patternObjs[i] = Tcl_NewIntObj(i);
+	    Tcl_IncrRefCount(patternObjs[i]);
+	}
+	objPtr = Tcl_NewListObj(len, NULL);
+	for (i = 0; i < len; ++i) {
+	    Tcl_ListObjAppendElement(
+		interp, objPtr, patternObjs[i % PATTERN_LEN]);
+	}
+	if (split >= 0) {
+	    assert(split < len);
+	    Tcl_Obj *splitMarker = Tcl_NewStringObj("X", 1);
+	    Tcl_ListObjReplace(interp, objPtr, split, 1, 1, &splitMarker);
+	}
+	for (i = 0; i < PATTERN_LEN; ++i) {
+	    patternObjs[i] = Tcl_NewIntObj(i);
+	    Tcl_DecrRefCount(patternObjs[i]);
+	}
+	Tcl_SetObjResult(interp, objPtr);
+	break;
+    }
+    return TCL_OK;
+}
+
 /*
  *----------------------------------------------------------------------
  *
  * SetVarToObj --
  *