pdfviewer: add macros to automatically check number and type of parameters

experimental/PdfViewer/SkPdfRenderer.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkCanvas.h"
 #include "SkDevice.h"
 #include "SkForceLinking.h"
@@ skipping 53 matching lines @@
  * - encapsulate native in the pdf api so the skpdf does not know anything about native ... in progress
  * - load gs/ especially smask and already known prop (skp) ... in progress
  * - wrapper on classes for customizations? e.g.
  * SkPdfPageObjectVanila - has only the basic loaders/getters
  * SkPdfPageObject : public SkPdfPageObjectVanila, extends, and I can add customizations here
  * need to find a nice object model for all this with constructors and factories
  * - deal with inheritable automatically ?
  * - deal with specific type in spec directly, add all dictionary types to known types
 */
 
+#define EXPECT_OPERANDS(pdfContext,n) \
+    bool __failed = pdfContext->fObjectStack.count() < n; \
+    SkDEBUGCODE(int __cnt = n);
+
+#define POP_OBJ(pdfContext,name) \
+    SkDEBUGCODE(__cnt--); \
+    SkASSERT(__cnt >= 0); \
+    SkPdfNativeObject* name = NULL; \
+    __failed = __failed || pdfContext->fObjectStack.count() == 0; \
+    if (pdfContext->fObjectStack.count() > 0) { \
+        name = pdfContext->fObjectStack.top(); \
+        pdfContext->fObjectStack.pop(); \
+    }
+
+#define POP_NUMBER(pdfContext,name) \
+    SkDEBUGCODE(__cnt--); \
+    SkASSERT(__cnt >= 0); \
+    double name = 0; \
+    __failed = __failed || pdfContext->fObjectStack.count() == 0; \
+    if (pdfContext->fObjectStack.count() > 0) { \
+        SkPdfNativeObject* tmp = pdfContext->fObjectStack.top(); \
+        pdfContext->fObjectStack.pop(); \
+        if (!tmp || !tmp->isNumber()) { \
+            __failed = true;\
+        } else { \
+            name = tmp->numberValue(); \
+        } \
+    }
+
+#define POP_INTEGER(pdfContext,name) \
+    SkDEBUGCODE(__cnt--); \
+    SkASSERT(__cnt >= 0); \
+    int64_t name = 0; \
+    __failed = __failed || pdfContext->fObjectStack.count() == 0; \
+    if (pdfContext->fObjectStack.count() > 0) { \
+        SkPdfNativeObject* tmp = pdfContext->fObjectStack.top(); \
+        pdfContext->fObjectStack.pop(); \
+        if (!tmp || !tmp->isInteger()) { \
+            __failed = true;\
+        } else { \
+            name = tmp->intValue(); \
+        } \
+    }
+
+#define POP_NUMBER_INTO(pdfContext,var) \
+    SkDEBUGCODE(__cnt--); \
+    SkASSERT(__cnt >= 0); \
+    __failed = __failed || pdfContext->fObjectStack.count() == 0; \
+    if (pdfContext->fObjectStack.count() > 0) { \
+        SkPdfNativeObject* tmp = pdfContext->fObjectStack.top(); \
+        pdfContext->fObjectStack.pop(); \
+        if (!tmp || !tmp->isNumber()) { \
+            __failed = true;\
+        } else { \
+            var = tmp->numberValue(); \
+        } \
+    }
+
+
+#define POP_NAME(pdfContext,name) \
+    SkDEBUGCODE(__cnt--); \
+    SkASSERT(__cnt >= 0); \
+    SkPdfNativeObject* name = NULL; \
+    __failed = __failed || pdfContext->fObjectStack.count() == 0; \
+    if (pdfContext->fObjectStack.count() > 0) { \
+        SkPdfNativeObject* tmp = pdfContext->fObjectStack.top(); \
+        pdfContext->fObjectStack.pop(); \
+        if (!tmp || !tmp->isName()) { \
+            __failed = true;\
+        } else { \
+            name = tmp; \
+        } \
+    }
+
+#define POP_STRING(pdfContext,name) \
+    SkDEBUGCODE(__cnt--); \
+    SkASSERT(__cnt >= 0); \
+    SkPdfNativeObject* name = NULL; \
+    __failed = __failed || pdfContext->fObjectStack.count() == 0; \
+    if (pdfContext->fObjectStack.count() > 0) { \
+        SkPdfNativeObject* tmp = pdfContext->fObjectStack.top(); \
+        pdfContext->fObjectStack.pop(); \
+        if (!tmp || !tmp->isAnyString()) { \
+            __failed = true;\
+        } else { \
+            name = tmp; \
+        } \
+    }
+
+#define POP_ARRAY(pdfContext,name) \
+    SkDEBUGCODE(__cnt--); \
+    SkASSERT(__cnt >= 0); \
+    SkPdfArray* name = NULL; \
+    __failed = __failed || pdfContext->fObjectStack.count() == 0; \
+    if (pdfContext->fObjectStack.count() > 0) { \
+        SkPdfNativeObject* tmp = pdfContext->fObjectStack.top(); \
+        pdfContext->fObjectStack.pop(); \
+        if (!tmp || !tmp->isArray()) { \
+            __failed = true;\
+        } else { \
+            name = (SkPdfArray*)tmp; \
+        } \
+    }
+
+// TODO(edisonn): ability to turn on asserts for known good files
+// log error - add name of function? location in file?
+#define CHECK_PARAMETERS() \
+    SkASSERT(__cnt == 0); \
+    if (__failed) return kIgnoreError_SkPdfResult;
+
 NotOwnedString strings_DeviceRGB;
 NotOwnedString strings_DeviceCMYK;
 
 class StringsInit {
 public:
     StringsInit() {
         NotOwnedString::init(&strings_DeviceRGB, "DeviceRGB");
         NotOwnedString::init(&strings_DeviceCMYK, "DeviceCMYK");
     }
 };
@@ skipping 880 matching lines @@
     }
 
     // TODO(edisonn): should we restore the variable stack at the same state?
     // There could be operands left, that could be consumed by a parent tokenizer when we pop.
     canvas->restore();
     PdfOp_Q(pdfContext, canvas, NULL);
     return kPartial_SkPdfResult;
 }
 
 SkPdfResult PdfOp_q(SkPdfContext* pdfContext, SkCanvas* canvas, PdfTokenLooper** looper) {
+    // TODO(edisonn): create a new stack of parameters, so once we start a q,
+    // it is not possible to see under the previous q?
     pdfContext->fStateStack.push(pdfContext->fGraphicsState);
     canvas->save();
     return kOK_SkPdfResult;
 }
 
 SkPdfResult PdfOp_Q(SkPdfContext* pdfContext, SkCanvas* canvas, PdfTokenLooper** looper) {
     pdfContext->fGraphicsState = pdfContext->fStateStack.top();
     pdfContext->fStateStack.pop();
     canvas->restore();
     return kOK_SkPdfResult;
 }
 
 static SkPdfResult PdfOp_cm(SkPdfContext* pdfContext, SkCanvas* canvas, PdfTokenLooper** looper) {
-    double array[6];
-    for (int i = 0 ; i < 6 ; i++) {
-        array[5 - i] = pdfContext->fObjectStack.top()->numberValue();
-        pdfContext->fObjectStack.pop();
-    }
+    EXPECT_OPERANDS(pdfContext, 6);
+    POP_NUMBER(pdfContext, f);
+    POP_NUMBER(pdfContext, e);
+    POP_NUMBER(pdfContext, d);
+    POP_NUMBER(pdfContext, c);
+    POP_NUMBER(pdfContext, b);
+    POP_NUMBER(pdfContext, a);
+    CHECK_PARAMETERS();
+    double array[6] = {a, b, c, d, e, f};
 
     // a b
     // c d
     // e f
 
     // 0 1
     // 2 3
     // 4 5
 
     // sx ky
@@ skipping 12 matching lines @@
     SkTraceMatrix(pdfContext->fGraphicsState.fCTM, "cm");
 #endif
 
     return kOK_SkPdfResult;
 }
 
 //leading TL Set the text leading, Tl
 //, to leading, which is a number expressed in unscaled text
 //space units. Text leading is used only by the T*, ', and " operators. Initial value: 0.
 static SkPdfResult PdfOp_TL(SkPdfContext* pdfContext, SkCanvas* canvas, PdfTokenLooper** looper) {
-    double ty = pdfContext->fObjectStack.top()->numberValue();   pdfContext->fObjectStack.pop();
+    EXPECT_OPERANDS(pdfContext, 1)
+    POP_NUMBER(pdfContext, ty);
+    CHECK_PARAMETERS();
 
     pdfContext->fGraphicsState.fTextLeading = ty;
 
     return kOK_SkPdfResult;
 }
 
 static SkPdfResult PdfOp_Td(SkPdfContext* pdfContext, SkCanvas* canvas, PdfTokenLooper** looper) {
-#ifdef PDF_TRACE
-    printf("stack size = %i\n", (int)pdfContext->fObjectStack.size());
-#endif
-    double ty = pdfContext->fObjectStack.top()->numberValue(); pdfContext->fObjectStack.pop();
-    double tx = pdfContext->fObjectStack.top()->numberValue(); pdfContext->fObjectStack.pop();
+    EXPECT_OPERANDS(pdfContext, 2);
+    POP_NUMBER(pdfContext, ty);
+    POP_NUMBER(pdfContext, tx);
+    CHECK_PARAMETERS();
 
     double array[6] = {1, 0, 0, 1, tx, -ty};
     SkMatrix matrix = SkMatrixFromPdfMatrix(array);
 
     pdfContext->fGraphicsState.fMatrixTm.preConcat(matrix);
     pdfContext->fGraphicsState.fMatrixTlm.preConcat(matrix);
 
     return kPartial_SkPdfResult;
 }
 
 static SkPdfResult PdfOp_TD(SkPdfContext* pdfContext, SkCanvas* canvas, PdfTokenLooper** looper) {
-    double ty = pdfContext->fObjectStack.top()->numberValue(); pdfContext->fObjectStack.pop();
-    double tx = pdfContext->fObjectStack.top()->numberValue(); pdfContext->fObjectStack.pop();
+    EXPECT_OPERANDS(pdfContext, 2)
+    POP_NUMBER(pdfContext, ty);
+    POP_NUMBER(pdfContext, tx);
+    CHECK_PARAMETERS();
 
     // TODO(edisonn): Create factory methods or constructors so native is hidden
     SkPdfReal* _ty = pdfContext->fPdfDoc->createReal(-ty);
     pdfContext->fObjectStack.push(_ty);
 
     PdfOp_TL(pdfContext, canvas, looper);
 
     SkPdfReal* vtx = pdfContext->fPdfDoc->createReal(tx);
     pdfContext->fObjectStack.push(vtx);
 
     SkPdfReal* vty = pdfContext->fPdfDoc->createReal(ty);
     pdfContext->fObjectStack.push(vty);
 
     SkPdfResult ret = PdfOp_Td(pdfContext, canvas, looper);
 
     // TODO(edisonn): delete all the objects after rendering was complete, in this way pdf is rendered faster
     // and the cleanup can happen while the user looks at the image
 
     return ret;
 }
 
 static SkPdfResult PdfOp_Tm(SkPdfContext* pdfContext, SkCanvas* canvas, PdfTokenLooper** looper) {
-    double f = pdfContext->fObjectStack.top()->numberValue(); pdfContext->fObjectStack.pop();
-    double e = pdfContext->fObjectStack.top()->numberValue(); pdfContext->fObjectStack.pop();
-    double d = pdfContext->fObjectStack.top()->numberValue(); pdfContext->fObjectStack.pop();
-    double c = pdfContext->fObjectStack.top()->numberValue(); pdfContext->fObjectStack.pop();
-    double b = pdfContext->fObjectStack.top()->numberValue(); pdfContext->fObjectStack.pop();
-    double a = pdfContext->fObjectStack.top()->numberValue(); pdfContext->fObjectStack.pop();
+    EXPECT_OPERANDS(pdfContext, 6);
+    POP_NUMBER(pdfContext, f);
+    POP_NUMBER(pdfContext, e);
+    POP_NUMBER(pdfContext, d);
+    POP_NUMBER(pdfContext, c);
+    POP_NUMBER(pdfContext, b);
+    POP_NUMBER(pdfContext, a);
+    CHECK_PARAMETERS();
 
     double array[6];
     array[0] = a;
     array[1] = b;
     array[2] = c;
     array[3] = d;
     array[4] = e;
     array[5] = f;
 
     SkMatrix matrix = SkMatrixFromPdfMatrix(array);
@@ skipping 21 matching lines @@
 
     return ret;
 }
 
 static SkPdfResult PdfOp_m(SkPdfContext* pdfContext, SkCanvas* canvas, PdfTokenLooper** looper) {
     if (pdfContext->fGraphicsState.fPathClosed) {
         pdfContext->fGraphicsState.fPath.reset();
         pdfContext->fGraphicsState.fPathClosed = false;
     }
 
-    pdfContext->fGraphicsState.fCurPosY = pdfContext->fObjectStack.top()->numberValue();    pdfContext->fObjectStack.pop();
-    pdfContext->fGraphicsState.fCurPosX = pdfContext->fObjectStack.top()->numberValue();    pdfContext->fObjectStack.pop();
+    EXPECT_OPERANDS(pdfContext, 2);
+    POP_NUMBER(pdfContext, y);
+    POP_NUMBER(pdfContext, x);
+    CHECK_PARAMETERS();
+
+    pdfContext->fGraphicsState.fCurPosY = y;
+    pdfContext->fGraphicsState.fCurPosX = x;
 
     pdfContext->fGraphicsState.fPath.moveTo(SkDoubleToScalar(pdfContext->fGraphicsState.fCurPosX),
-                                          SkDoubleToScalar(pdfContext->fGraphicsState.fCurPosY));
+                                            SkDoubleToScalar(pdfContext->fGraphicsState.fCurPosY));
 
     return kOK_SkPdfResult;
 }
 
 static SkPdfResult PdfOp_l(SkPdfContext* pdfContext, SkCanvas* canvas, PdfTokenLooper** looper) {
     if (pdfContext->fGraphicsState.fPathClosed) {
         pdfContext->fGraphicsState.fPath.reset();
         pdfContext->fGraphicsState.fPathClosed = false;
     }
 
-    pdfContext->fGraphicsState.fCurPosY = pdfContext->fObjectStack.top()->numberValue();    pdfContext->fObjectStack.pop();
-    pdfContext->fGraphicsState.fCurPosX = pdfContext->fObjectStack.top()->numberValue();    pdfContext->fObjectStack.pop();
+    EXPECT_OPERANDS(pdfContext, 2);
+    POP_NUMBER(pdfContext, y);
+    POP_NUMBER(pdfContext, x);
+    CHECK_PARAMETERS();
+
+    pdfContext->fGraphicsState.fCurPosY = y;
+    pdfContext->fGraphicsState.fCurPosX = x;
 
     pdfContext->fGraphicsState.fPath.lineTo(SkDoubleToScalar(pdfContext->fGraphicsState.fCurPosX),
-                                          SkDoubleToScalar(pdfContext->fGraphicsState.fCurPosY));
+                                            SkDoubleToScalar(pdfContext->fGraphicsState.fCurPosY));
 
     return kOK_SkPdfResult;
 }
 
 static SkPdfResult PdfOp_c(SkPdfContext* pdfContext, SkCanvas* canvas, PdfTokenLooper** looper) {
     if (pdfContext->fGraphicsState.fPathClosed) {
         pdfContext->fGraphicsState.fPath.reset();
         pdfContext->fGraphicsState.fPathClosed = false;
     }
 
-    double y3 = pdfContext->fObjectStack.top()->numberValue();    pdfContext->fObjectStack.pop();
-    double x3 = pdfContext->fObjectStack.top()->numberValue();    pdfContext->fObjectStack.pop();
-    double y2 = pdfContext->fObjectStack.top()->numberValue();    pdfContext->fObjectStack.pop();
-    double x2 = pdfContext->fObjectStack.top()->numberValue();    pdfContext->fObjectStack.pop();
-    double y1 = pdfContext->fObjectStack.top()->numberValue();    pdfContext->fObjectStack.pop();
-    double x1 = pdfContext->fObjectStack.top()->numberValue();    pdfContext->fObjectStack.pop();
+    EXPECT_OPERANDS(pdfContext, 6);
+    POP_NUMBER(pdfContext, y3);
+    POP_NUMBER(pdfContext, x3);
+    POP_NUMBER(pdfContext, y2);
+    POP_NUMBER(pdfContext, x2);
+    POP_NUMBER(pdfContext, y1);
+    POP_NUMBER(pdfContext, x1);
+    CHECK_PARAMETERS();
 
     pdfContext->fGraphicsState.fPath.cubicTo(SkDoubleToScalar(x1), SkDoubleToScalar(y1),
-                                            SkDoubleToScalar(x2), SkDoubleToScalar(y2),
-                                            SkDoubleToScalar(x3), SkDoubleToScalar(y3));
+                                             SkDoubleToScalar(x2), SkDoubleToScalar(y2),
+                                             SkDoubleToScalar(x3), SkDoubleToScalar(y3));
 
     pdfContext->fGraphicsState.fCurPosX = x3;
     pdfContext->fGraphicsState.fCurPosY = y3;
 
     return kOK_SkPdfResult;
 }
 
 static SkPdfResult PdfOp_v(SkPdfContext* pdfContext, SkCanvas* canvas, PdfTokenLooper** looper) {
     if (pdfContext->fGraphicsState.fPathClosed) {
         pdfContext->fGraphicsState.fPath.reset();
         pdfContext->fGraphicsState.fPathClosed = false;
     }
 
-    double y3 = pdfContext->fObjectStack.top()->numberValue();    pdfContext->fObjectStack.pop();
-    double x3 = pdfContext->fObjectStack.top()->numberValue();    pdfContext->fObjectStack.pop();
-    double y2 = pdfContext->fObjectStack.top()->numberValue();    pdfContext->fObjectStack.pop();
-    double x2 = pdfContext->fObjectStack.top()->numberValue();    pdfContext->fObjectStack.pop();
+    EXPECT_OPERANDS(pdfContext, 4);
+    POP_NUMBER(pdfContext, y3);
+    POP_NUMBER(pdfContext, x3);
+    POP_NUMBER(pdfContext, y2);
+    POP_NUMBER(pdfContext, x2);
+    CHECK_PARAMETERS();
+
     double y1 = pdfContext->fGraphicsState.fCurPosY;
     double x1 = pdfContext->fGraphicsState.fCurPosX;
 
     pdfContext->fGraphicsState.fPath.cubicTo(SkDoubleToScalar(x1), SkDoubleToScalar(y1),
-                                            SkDoubleToScalar(x2), SkDoubleToScalar(y2),
-                                            SkDoubleToScalar(x3), SkDoubleToScalar(y3));
+                                             SkDoubleToScalar(x2), SkDoubleToScalar(y2),
+                                             SkDoubleToScalar(x3), SkDoubleToScalar(y3));
 
     pdfContext->fGraphicsState.fCurPosX = x3;
     pdfContext->fGraphicsState.fCurPosY = y3;
 
     return kOK_SkPdfResult;
 }
 
 static SkPdfResult PdfOp_y(SkPdfContext* pdfContext, SkCanvas* canvas, PdfTokenLooper** looper) {
     if (pdfContext->fGraphicsState.fPathClosed) {
         pdfContext->fGraphicsState.fPath.reset();
         pdfContext->fGraphicsState.fPathClosed = false;
     }
 
-    double y3 = pdfContext->fObjectStack.top()->numberValue();    pdfContext->fObjectStack.pop();
-    double x3 = pdfContext->fObjectStack.top()->numberValue();    pdfContext->fObjectStack.pop();
+    EXPECT_OPERANDS(pdfContext, 4);
+    POP_NUMBER(pdfContext, y3);
+    POP_NUMBER(pdfContext, x3);
+    POP_NUMBER(pdfContext, y1);
+    POP_NUMBER(pdfContext, x1);
+    CHECK_PARAMETERS();
+
     double y2 = pdfContext->fGraphicsState.fCurPosY;
     double x2 = pdfContext->fGraphicsState.fCurPosX;
-    double y1 = pdfContext->fObjectStack.top()->numberValue();    pdfContext->fObjectStack.pop();
-    double x1 = pdfContext->fObjectStack.top()->numberValue();    pdfContext->fObjectStack.pop();
 
     pdfContext->fGraphicsState.fPath.cubicTo(SkDoubleToScalar(x1), SkDoubleToScalar(y1),
-                                            SkDoubleToScalar(x2), SkDoubleToScalar(y2),
-                                            SkDoubleToScalar(x3), SkDoubleToScalar(y3));
+                                             SkDoubleToScalar(x2), SkDoubleToScalar(y2),
+                                             SkDoubleToScalar(x3), SkDoubleToScalar(y3));
 
     pdfContext->fGraphicsState.fCurPosX = x3;
     pdfContext->fGraphicsState.fCurPosY = y3;
 
     return kOK_SkPdfResult;
 }
 
 static SkPdfResult PdfOp_re(SkPdfContext* pdfContext, SkCanvas* canvas, PdfTokenLooper** looper) {
     if (pdfContext->fGraphicsState.fPathClosed) {
         pdfContext->fGraphicsState.fPath.reset();
         pdfContext->fGraphicsState.fPathClosed = false;
     }
 
-    double height = pdfContext->fObjectStack.top()->numberValue();      pdfContext->fObjectStack.pop();
-    double width = pdfContext->fObjectStack.top()->numberValue();       pdfContext->fObjectStack.pop();
-    double y = pdfContext->fObjectStack.top()->numberValue();           pdfContext->fObjectStack.pop();
-    double x = pdfContext->fObjectStack.top()->numberValue();           pdfContext->fObjectStack.pop();
+    EXPECT_OPERANDS(pdfContext, 4);
+    POP_NUMBER(pdfContext, height);
+    POP_NUMBER(pdfContext, width);
+    POP_NUMBER(pdfContext, y);
+    POP_NUMBER(pdfContext, x);
+    CHECK_PARAMETERS();
 
     pdfContext->fGraphicsState.fPath.addRect(SkDoubleToScalar(x), SkDoubleToScalar(y),
-                                           SkDoubleToScalar(x + width), SkDoubleToScalar(y + height));
+                                             SkDoubleToScalar(x + width), SkDoubleToScalar(y + height));
 
     pdfContext->fGraphicsState.fCurPosX = x;
     pdfContext->fGraphicsState.fCurPosY = y + height;
 
     return kOK_SkPdfResult;
 }
 
 static SkPdfResult PdfOp_h(SkPdfContext* pdfContext, SkCanvas* canvas, PdfTokenLooper** looper) {
     pdfContext->fGraphicsState.fPath.close();
     return kOK_SkPdfResult;
@@ skipping 227 matching lines @@
     pdfContext->fGraphicsState.fCurFontSize = fontSize;
     return kOK_SkPdfResult;
 }
 
 //font size Tf Set the text font, Tf
 //, to font and the text font size, Tfs, to size. font is the name of a
 //font resource in the Fontsubdictionary of the current resource dictionary; size is
 //a number representing a scale factor. There is no initial value for either font or
 //size; they must be specified explicitly using Tf before any text is shown.
 static SkPdfResult PdfOp_Tf(SkPdfContext* pdfContext, SkCanvas* canvas, PdfTokenLooper** looper) {
-    double fontSize = pdfContext->fObjectStack.top()->numberValue();     pdfContext->fObjectStack.pop();
-    SkPdfNativeObject* fontName = pdfContext->fObjectStack.top();                           pdfContext->fObjectStack.pop();
+    EXPECT_OPERANDS(pdfContext, 2);
+    POP_NUMBER(pdfContext, fontSize);
+    POP_NAME(pdfContext, fontName);
+    CHECK_PARAMETERS();
+
     return skpdfGraphicsStateApplyFontCore(pdfContext, fontName, fontSize);
 }
 
 static SkPdfResult PdfOp_Tj(SkPdfContext* pdfContext, SkCanvas* canvas, PdfTokenLooper** looper) {
+    EXPECT_OPERANDS(pdfContext, 1);
+    POP_STRING(pdfContext, str);
+    CHECK_PARAMETERS();
+
     if (!pdfContext->fGraphicsState.fTextBlock) {
         // TODO(edisonn): try to recover and draw it any way?
         return kIgnoreError_SkPdfResult;
     }
 
-    SkPdfResult ret = DrawText(pdfContext,
-                             pdfContext->fObjectStack.top(),
-                             canvas);
-    pdfContext->fObjectStack.pop();
+    SkPdfResult ret = DrawText(pdfContext, str, canvas);
 
     return ret;
 }
 
 static SkPdfResult PdfOp_quote(SkPdfContext* pdfContext, SkCanvas* canvas, PdfTokenLooper** looper) {
     if (!pdfContext->fGraphicsState.fTextBlock) {
         // TODO(edisonn): try to recover and draw it any way?
         return kIgnoreError_SkPdfResult;
     }
 
     PdfOp_T_star(pdfContext, canvas, looper);
     // Do not pop, and push, just transfer the param to Tj
     return PdfOp_Tj(pdfContext, canvas, looper);
 }
 
 static SkPdfResult PdfOp_doublequote(SkPdfContext* pdfContext, SkCanvas* canvas, PdfTokenLooper** looper) {
     if (!pdfContext->fGraphicsState.fTextBlock) {
         // TODO(edisonn): try to recover and draw it any way?
         return kIgnoreError_SkPdfResult;
     }
 
-    SkPdfNativeObject* str = pdfContext->fObjectStack.top();       pdfContext->fObjectStack.pop();
-    SkPdfNativeObject* ac = pdfContext->fObjectStack.top();        pdfContext->fObjectStack.pop();
-    SkPdfNativeObject* aw = pdfContext->fObjectStack.top();        pdfContext->fObjectStack.pop();
+    EXPECT_OPERANDS(pdfContext, 3);
+    POP_OBJ(pdfContext, str);
+    POP_OBJ(pdfContext, ac);
+    POP_OBJ(pdfContext, aw);
+    CHECK_PARAMETERS();
 
     pdfContext->fObjectStack.push(aw);
     PdfOp_Tw(pdfContext, canvas, looper);
 
     pdfContext->fObjectStack.push(ac);
     PdfOp_Tc(pdfContext, canvas, looper);
 
     pdfContext->fObjectStack.push(str);
     PdfOp_quote(pdfContext, canvas, looper);
 
     return kPartial_SkPdfResult;
 }
 
 static SkPdfResult PdfOp_TJ(SkPdfContext* pdfContext, SkCanvas* canvas, PdfTokenLooper** looper) {
+    EXPECT_OPERANDS(pdfContext, 1);
+    POP_ARRAY(pdfContext, array);
+    CHECK_PARAMETERS();
+
     if (!pdfContext->fGraphicsState.fTextBlock) {
         // TODO(edisonn): try to recover and draw it any way?
         return kIgnoreError_SkPdfResult;
     }
 
-    SkPdfArray* array = (SkPdfArray*)pdfContext->fObjectStack.top();
-    pdfContext->fObjectStack.pop();
-
     if (!array->isArray()) {
         return kIgnoreError_SkPdfResult;
     }
 
     for( int i=0; i<static_cast<int>(array->size()); i++ )
     {
         if( (*array)[i]->isAnyString()) {
             SkPdfNativeObject* obj = (*array)[i];
-            DrawText(pdfContext,
-                     obj,
-                     canvas);
+            DrawText(pdfContext, obj, canvas);
         } else if ((*array)[i]->isNumber()) {
             double dx = (*array)[i]->numberValue();
             SkMatrix matrix;
             matrix.setAll(SkDoubleToScalar(1),
                           SkDoubleToScalar(0),
                           // TODO(edisonn): use writing mode, vertical/horizontal.
                           SkDoubleToScalar(-dx),  // amount is substracted!!!
                           SkDoubleToScalar(0),
                           SkDoubleToScalar(1),
                           SkDoubleToScalar(0),
                           SkDoubleToScalar(0),
                           SkDoubleToScalar(0),
                           SkDoubleToScalar(1));
 
             pdfContext->fGraphicsState.fMatrixTm.preConcat(matrix);
         }
     }
     return kPartial_SkPdfResult;  // TODO(edisonn): Implement fully DrawText before returing OK.
 }
 
 static SkPdfResult PdfOp_CS_cs(SkPdfContext* pdfContext, SkCanvas* canvas, SkPdfColorOperator* colorOperator) {
-    SkPdfNativeObject* name = pdfContext->fObjectStack.top();    pdfContext->fObjectStack.pop();
+    EXPECT_OPERANDS(pdfContext, 1);
+    POP_NAME(pdfContext, name);
+    CHECK_PARAMETERS();
 
     //Next, get the ColorSpace Dictionary from the Resource Dictionary:
     SkPdfDictionary* colorSpaceResource = pdfContext->fGraphicsState.fResources->ColorSpace(pdfContext->fPdfDoc);
 
     SkPdfNativeObject* colorSpace = colorSpaceResource ? pdfContext->fPdfDoc->resolveReference(colorSpaceResource->get(name)) : name;
 
     if (colorSpace == NULL) {
         colorOperator->fColorSpace = name->strRef();
     } else {
 #ifdef PDF_TRACE
@@ skipping 47 matching lines @@
 
     bool doubles = true;
     if (colorOperator->fColorSpace.equals("Indexed")) {
         doubles = false;
     }
 
 #ifdef PDF_TRACE
     printf("color space = %s, N = %i\n", colorOperator->fColorSpace.fBuffer, n);
 #endif
 
+    EXPECT_OPERANDS(pdfContext, n);
+
     for (int i = n - 1; i >= 0 ; i--) {
         if (doubles) {
-            c[i] = pdfContext->fObjectStack.top()->numberValue();         pdfContext->fObjectStack.pop();
+            POP_NUMBER_INTO(pdfContext, c[i]);
 //        } else {
 //            v[i] = pdfContext->fObjectStack.top()->intValue();        pdfContext->fObjectStack.pop();
         }
     }
+    CHECK_PARAMETERS();
 
     // TODO(edisonn): Now, set that color. Only DeviceRGB supported.
     // TODO(edisonn): do possible field values to enum at parsing time!
     // TODO(edisonn): support also abreviations /DeviceRGB == /RGB
     if (colorOperator->fColorSpace.equals("DeviceRGB") || colorOperator->fColorSpace.equals("RGB")) {
         colorOperator->setRGBColor(SkColorSetRGB((U8CPU)(255*c[0]), (U8CPU)(255*c[1]), (U8CPU)(255*c[2])));
     }
     return kPartial_SkPdfResult;
 }
 
 static SkPdfResult PdfOp_SC(SkPdfContext* pdfContext, SkCanvas* canvas, PdfTokenLooper** looper) {
     return PdfOp_SC_sc(pdfContext, canvas, &pdfContext->fGraphicsState.fStroking);
 }
 
 static SkPdfResult PdfOp_sc(SkPdfContext* pdfContext, SkCanvas* canvas, PdfTokenLooper** looper) {
     return PdfOp_SC_sc(pdfContext, canvas, &pdfContext->fGraphicsState.fNonStroking);
 }
 
 static SkPdfResult PdfOp_SCN_scn(SkPdfContext* pdfContext, SkCanvas* canvas, SkPdfColorOperator* colorOperator) {
-    if (pdfContext->fObjectStack.top()->isName()) {
+    if (pdfContext->fObjectStack.count() > 0 && pdfContext->fObjectStack.top()->isName()) {
         SkPdfNativeObject* name = pdfContext->fObjectStack.top();    pdfContext->fObjectStack.pop();
 
         //Next, get the ExtGState Dictionary from the Resource Dictionary:
         SkPdfDictionary* patternResources = pdfContext->fGraphicsState.fResources->Pattern(pdfContext->fPdfDoc);
 
         if (patternResources == NULL) {
 #ifdef PDF_TRACE
             printf("ExtGState is NULL!\n");
 #endif
             return kIgnoreError_SkPdfResult;
@@ skipping 10 matching lines @@
 
 static SkPdfResult PdfOp_SCN(SkPdfContext* pdfContext, SkCanvas* canvas, PdfTokenLooper** looper) {
     return PdfOp_SCN_scn(pdfContext, canvas, &pdfContext->fGraphicsState.fStroking);
 }
 
 static SkPdfResult PdfOp_scn(SkPdfContext* pdfContext, SkCanvas* canvas, PdfTokenLooper** looper) {
     return PdfOp_SCN_scn(pdfContext, canvas, &pdfContext->fGraphicsState.fNonStroking);
 }
 
 static SkPdfResult PdfOp_G_g(SkPdfContext* pdfContext, SkCanvas* canvas, SkPdfColorOperator* colorOperator) {
-    /*double gray = */pdfContext->fObjectStack.top()->numberValue();     pdfContext->fObjectStack.pop();
-    return kNYI_SkPdfResult;
+    EXPECT_OPERANDS(pdfContext, 1);
+    POP_NUMBER(pdfContext, gray);
+    CHECK_PARAMETERS();
+
+    colorOperator->fColorSpace = strings_DeviceRGB;  // TODO(edisonn): HACK - it should be device gray, but not suported right now
+    colorOperator->setRGBColor(SkColorSetRGB((U8CPU)(255*gray), (U8CPU)(255*gray), (U8CPU)(255*gray)));
+
+    return kPartial_SkPdfResult;
 }
 
 static SkPdfResult PdfOp_G(SkPdfContext* pdfContext, SkCanvas* canvas, PdfTokenLooper** looper) {
     return PdfOp_G_g(pdfContext, canvas, &pdfContext->fGraphicsState.fStroking);
 }
 
 static SkPdfResult PdfOp_g(SkPdfContext* pdfContext, SkCanvas* canvas, PdfTokenLooper** looper) {
     return PdfOp_G_g(pdfContext, canvas, &pdfContext->fGraphicsState.fNonStroking);
 }
 
 static SkPdfResult PdfOp_RG_rg(SkPdfContext* pdfContext, SkCanvas* canvas, SkPdfColorOperator* colorOperator) {
-    double b = pdfContext->fObjectStack.top()->numberValue();     pdfContext->fObjectStack.pop();
-    double g = pdfContext->fObjectStack.top()->numberValue();     pdfContext->fObjectStack.pop();
-    double r = pdfContext->fObjectStack.top()->numberValue();     pdfContext->fObjectStack.pop();
+    EXPECT_OPERANDS(pdfContext, 3);
+    POP_NUMBER(pdfContext, b);
+    POP_NUMBER(pdfContext, g);
+    POP_NUMBER(pdfContext, r);
+    CHECK_PARAMETERS();
 
     colorOperator->fColorSpace = strings_DeviceRGB;
     colorOperator->setRGBColor(SkColorSetRGB((U8CPU)(255*r), (U8CPU)(255*g), (U8CPU)(255*b)));
     return kOK_SkPdfResult;
 }
 
 static SkPdfResult PdfOp_RG(SkPdfContext* pdfContext, SkCanvas* canvas, PdfTokenLooper** looper) {
     return PdfOp_RG_rg(pdfContext, canvas, &pdfContext->fGraphicsState.fStroking);
 }
 
 static SkPdfResult PdfOp_rg(SkPdfContext* pdfContext, SkCanvas* canvas, PdfTokenLooper** looper) {
     return PdfOp_RG_rg(pdfContext, canvas, &pdfContext->fGraphicsState.fNonStroking);
 }
 
 static SkPdfResult PdfOp_K_k(SkPdfContext* pdfContext, SkCanvas* canvas, SkPdfColorOperator* colorOperator) {
     // TODO(edisonn): spec has some rules about overprint, implement them.
-    /*double k = */pdfContext->fObjectStack.top()->numberValue();     pdfContext->fObjectStack.pop();
-    /*double y = */pdfContext->fObjectStack.top()->numberValue();     pdfContext->fObjectStack.pop();
-    /*double m = */pdfContext->fObjectStack.top()->numberValue();     pdfContext->fObjectStack.pop();
-    /*double c = */pdfContext->fObjectStack.top()->numberValue();     pdfContext->fObjectStack.pop();
+    EXPECT_OPERANDS(pdfContext, 4);
+    POP_NUMBER(pdfContext, k);
+    POP_NUMBER(pdfContext, y);
+    POP_NUMBER(pdfContext, m);
+    POP_NUMBER(pdfContext, c);
+    CHECK_PARAMETERS();
 
-    colorOperator->fColorSpace = strings_DeviceCMYK;
+    // TODO(edisonn): silly way to remove compiler warning
+    if (k + y + m + c == 0) {
+        return kNYI_SkPdfResult;
+    }
+
+    //colorOperator->fColorSpace = strings_DeviceCMYK;
     // TODO(edisonn): Set color.
     return kNYI_SkPdfResult;
 }
 
 static SkPdfResult PdfOp_K(SkPdfContext* pdfContext, SkCanvas* canvas, PdfTokenLooper** looper) {
     return PdfOp_K_k(pdfContext, canvas, &pdfContext->fGraphicsState.fStroking);
 }
 
 static SkPdfResult PdfOp_k(SkPdfContext* pdfContext, SkCanvas* canvas, PdfTokenLooper** looper) {
     return PdfOp_K_k(pdfContext, canvas, &pdfContext->fGraphicsState.fNonStroking);
@@ skipping 142 matching lines @@
     if (!fontAndSize || fontAndSize->isArray() || fontAndSize->size() != 2 || !fontAndSize->objAtAIndex(0)->isName() || !fontAndSize->objAtAIndex(1)->isNumber()) {
         // TODO(edisonn): report error/warning
         return;
     }
     skpdfGraphicsStateApplyFontCore(pdfContext, fontAndSize->objAtAIndex(0), fontAndSize->objAtAIndex(1)->numberValue());
 }
 
 
 //lineWidth w Set the line width in the graphics state (see “Line Width” on page 152).
 static SkPdfResult PdfOp_w(SkPdfContext* pdfContext, SkCanvas* canvas, PdfTokenLooper** looper) {
-    double lw = pdfContext->fObjectStack.top()->numberValue();    pdfContext->fObjectStack.pop();
+    EXPECT_OPERANDS(pdfContext, 1);
+    POP_NUMBER(pdfContext, lw);
+    CHECK_PARAMETERS();
+
     return skpdfGraphicsStateApplyLW(pdfContext, lw);
 }
 
 //lineCap J Set the line cap style in the graphics state (see “Line Cap Style” on page 153).
 static SkPdfResult PdfOp_J(SkPdfContext* pdfContext, SkCanvas* canvas, PdfTokenLooper** looper) {
     // TODO(edisonn): round/ceil to int?
-    int lc = (int)pdfContext->fObjectStack.top()->numberValue();    pdfContext->fObjectStack.pop();
-    return skpdfGraphicsStateApplyLC(pdfContext, lc);
+    EXPECT_OPERANDS(pdfContext, 1);
+    POP_NUMBER(pdfContext, lc);
+    CHECK_PARAMETERS();
+
+    return skpdfGraphicsStateApplyLC(pdfContext, (int)lc);
 }
 
 //lineJoin j Set the line join style in the graphics state (see “Line Join Style” on page 153).
 static SkPdfResult PdfOp_j(SkPdfContext* pdfContext, SkCanvas* canvas, PdfTokenLooper** looper) {
     // TODO(edisonn): round/ceil to int?
-    int lj = (int)pdfContext->fObjectStack.top()->numberValue();    pdfContext->fObjectStack.pop();
-    return skpdfGraphicsStateApplyLJ(pdfContext, lj);
+    EXPECT_OPERANDS(pdfContext, 1);
+    POP_NUMBER(pdfContext, lj);
+    CHECK_PARAMETERS();
+
+    return skpdfGraphicsStateApplyLJ(pdfContext, (int)lj);
 }
 
 //miterLimit M Set the miter limit in the graphics state (see “Miter Limit” on page 153).
 static SkPdfResult PdfOp_M(SkPdfContext* pdfContext, SkCanvas* canvas, PdfTokenLooper** looper) {
-    double ml = pdfContext->fObjectStack.top()->numberValue();    pdfContext->fObjectStack.pop();
+    EXPECT_OPERANDS(pdfContext, 1);
+    POP_NUMBER(pdfContext, ml);
+    CHECK_PARAMETERS();
     return skpdfGraphicsStateApplyML(pdfContext, ml);
 }
 
 //dashArray dashPhase d Set the line dash pattern in the graphics state (see “Line Dash Pattern” on
 //page 155).
 static SkPdfResult PdfOp_d(SkPdfContext* pdfContext, SkCanvas* canvas, PdfTokenLooper** looper) {
-    SkPdfNativeObject* phase = pdfContext->fObjectStack.top();          pdfContext->fObjectStack.pop();
-    SkPdfNativeObject* array = pdfContext->fObjectStack.top();          pdfContext->fObjectStack.pop();
+    EXPECT_OPERANDS(pdfContext, 2);
+    POP_OBJ(pdfContext, phase);
+    POP_ARRAY(pdfContext, array);
+    CHECK_PARAMETERS();
 
-    if (!array->isArray()) {
-        return kIgnoreError_SkPdfResult;
-    }
-
-    return skpdfGraphicsStateApplyD(pdfContext, (SkPdfArray*)array, phase);
+    return skpdfGraphicsStateApplyD(pdfContext, array, phase);
 }
 
 //intent ri (PDF 1.1) Set the color rendering intent in the graphics state (see “Rendering Intents” on page 197).
 static SkPdfResult PdfOp_ri(SkPdfContext* pdfContext, SkCanvas* canvas, PdfTokenLooper** looper) {
     pdfContext->fObjectStack.pop();
 
     return kNYI_SkPdfResult;
 }
 
 //flatness i Set the flatness tolerance in the graphics state (see Section 6.5.1, “Flatness
 //Tolerance”). flatness is a number in the range 0 to 100; a value of 0 speci-
 //fies the output device’s default flatness tolerance.
 static SkPdfResult PdfOp_i(SkPdfContext* pdfContext, SkCanvas* canvas, PdfTokenLooper** looper) {
-    pdfContext->fObjectStack.pop();
+    EXPECT_OPERANDS(pdfContext, 1);
+    POP_NUMBER(pdfContext, flatness);
+    CHECK_PARAMETERS();
+
+    if (flatness < 0 || flatness > 100) {
+        return kError_SkPdfResult;
+    }
 
     return kNYI_SkPdfResult;
 }
 
 SkTDict<SkXfermode::Mode> gPdfBlendModes(20);
 
 class InitBlendModes {
 public:
     InitBlendModes() {
         // TODO(edisonn): use the python code generator?
@@ skipping 109 matching lines @@
 }
 
 static void skpdfGraphicsStateApplyAIS(SkPdfContext* pdfContext, bool alphaSource) {
     pdfContext->fGraphicsState.fAlphaSource = alphaSource;
 }
 
 
 //dictName gs (PDF 1.2) Set the specified parameters in the graphics state. dictName is
 //the name of a graphics state parameter dictionary in the ExtGState subdictionary of the current resource dictionary (see the next section).
 static SkPdfResult PdfOp_gs(SkPdfContext* pdfContext, SkCanvas* canvas, PdfTokenLooper** looper) {
-    SkPdfNativeObject* name = pdfContext->fObjectStack.top();    pdfContext->fObjectStack.pop();
+    EXPECT_OPERANDS(pdfContext, 1);
+    POP_NAME(pdfContext, name);
+    CHECK_PARAMETERS();
 
 #ifdef PDF_TRACE
     SkString str;
 #endif
 
     //Next, get the ExtGState Dictionary from the Resource Dictionary:
     SkPdfDictionary* extGStateDictionary = pdfContext->fGraphicsState.fResources->ExtGState(pdfContext->fPdfDoc);
 
     if (extGStateDictionary == NULL) {
 #ifdef PDF_TRACE
@@ skipping 70 matching lines @@
         skpdfGraphicsStateApplyAIS(pdfContext, gs->AIS(pdfContext->fPdfDoc));
     }
 
     return kOK_SkPdfResult;
 }
 
 //charSpace Tc Set the character spacing, Tc
 //, to charSpace, which is a number expressed in unscaled text space units. Character spacing is used by the Tj, TJ, and ' operators.
 //Initial value: 0.
 SkPdfResult PdfOp_Tc(SkPdfContext* pdfContext, SkCanvas* canvas, PdfTokenLooper** looper) {
-    double charSpace = pdfContext->fObjectStack.top()->numberValue();     pdfContext->fObjectStack.pop();
+    EXPECT_OPERANDS(pdfContext, 1);
+    POP_NUMBER(pdfContext, charSpace);
+    CHECK_PARAMETERS();
+
     pdfContext->fGraphicsState.fCharSpace = charSpace;
 
     return kOK_SkPdfResult;
 }
 
 //wordSpace Tw Set the word spacing, T
 //w
 //, to wordSpace, which is a number expressed in unscaled
 //text space units. Word spacing is used by the Tj, TJ, and ' operators. Initial
 //value: 0.
 SkPdfResult PdfOp_Tw(SkPdfContext* pdfContext, SkCanvas* canvas, PdfTokenLooper** looper) {
-    double wordSpace = pdfContext->fObjectStack.top()->numberValue();     pdfContext->fObjectStack.pop();
+    EXPECT_OPERANDS(pdfContext, 1);
+    POP_NUMBER(pdfContext, wordSpace);
+    CHECK_PARAMETERS();
+
     pdfContext->fGraphicsState.fWordSpace = wordSpace;
 
     return kOK_SkPdfResult;
 }
 
 //scale Tz Set the horizontal scaling, Th
 //, to (scale ˜ 100). scale is a number specifying the
 //percentage of the normal width. Initial value: 100 (normal width).
 static SkPdfResult PdfOp_Tz(SkPdfContext* pdfContext, SkCanvas* canvas, PdfTokenLooper** looper) {
-    /*double scale = */pdfContext->fObjectStack.top()->numberValue();     pdfContext->fObjectStack.pop();
+    EXPECT_OPERANDS(pdfContext, 1);
+    POP_NUMBER(pdfContext, scale);
+    CHECK_PARAMETERS();
+
+    if (scale < 0) {
+        return kError_SkPdfResult;
+    }
 
     return kNYI_SkPdfResult;
 }
 
 //render Tr Set the text rendering mode, T
 //mode, to render, which is an integer. Initial value: 0.
 static SkPdfResult PdfOp_Tr(SkPdfContext* pdfContext, SkCanvas* canvas, PdfTokenLooper** looper) {
-    /*double render = */pdfContext->fObjectStack.top()->numberValue();     pdfContext->fObjectStack.pop();
+    EXPECT_OPERANDS(pdfContext, 1);
+    POP_INTEGER(pdfContext, mode);
+    CHECK_PARAMETERS();
+
+    if (mode < 0) {  // TODO(edisonn): function/enums with supported modes
+        return kError_SkPdfResult;
+    }
 
     return kNYI_SkPdfResult;
 }
 //rise Ts Set the text rise, Trise, to rise, which is a number expressed in unscaled text space
 //units. Initial value: 0.
 static SkPdfResult PdfOp_Ts(SkPdfContext* pdfContext, SkCanvas* canvas, PdfTokenLooper** looper) {
-    /*double rise = */pdfContext->fObjectStack.top()->numberValue();     pdfContext->fObjectStack.pop();
+    EXPECT_OPERANDS(pdfContext, 1);
+    POP_NUMBER(pdfContext, rise);
+    CHECK_PARAMETERS();
+
+    if (rise < 0) {
+        return kNYI_SkPdfResult;
+    }
 
     return kNYI_SkPdfResult;
 }
 
 //wx wy d0
 static SkPdfResult PdfOp_d0(SkPdfContext* pdfContext, SkCanvas* canvas, PdfTokenLooper** looper) {
-    pdfContext->fObjectStack.pop();
-    pdfContext->fObjectStack.pop();
+    EXPECT_OPERANDS(pdfContext, 2);
+    POP_NUMBER(pdfContext, wy);
+    POP_NUMBER(pdfContext, wx);
+    CHECK_PARAMETERS();
+
+    if (wx < 0 || wy < 0) {
+        return kError_SkPdfResult;
+    }
 
     return kNYI_SkPdfResult;
 }
 
 //wx wy llx lly urx ury d1
 static SkPdfResult PdfOp_d1(SkPdfContext* pdfContext, SkCanvas* canvas, PdfTokenLooper** looper) {
-    pdfContext->fObjectStack.pop();
-    pdfContext->fObjectStack.pop();
-    pdfContext->fObjectStack.pop();
-    pdfContext->fObjectStack.pop();
-    pdfContext->fObjectStack.pop();
-    pdfContext->fObjectStack.pop();
+    EXPECT_OPERANDS(pdfContext, 6);
+    POP_NUMBER(pdfContext, ury);
+    POP_NUMBER(pdfContext, urx);
+    POP_NUMBER(pdfContext, lly);
+    POP_NUMBER(pdfContext, llx);
+    POP_NUMBER(pdfContext, wy);
+    POP_NUMBER(pdfContext, wx);
+    CHECK_PARAMETERS();
+
+    if (wx + wy + llx + lly + urx + ury) {
+        return kNYI_SkPdfResult;
+    }
 
     return kNYI_SkPdfResult;
 }
 
 //name sh
 static SkPdfResult PdfOp_sh(SkPdfContext* pdfContext, SkCanvas* canvas, PdfTokenLooper** looper) {
-    pdfContext->fObjectStack.pop();
+    EXPECT_OPERANDS(pdfContext, 1);
+    POP_NAME(pdfContext, name);
+    CHECK_PARAMETERS();
+
+    if (name == NULL) {
+        return kError_SkPdfResult;
+    }
 
     return kNYI_SkPdfResult;
 }
 
 //name Do
 static SkPdfResult PdfOp_Do(SkPdfContext* pdfContext, SkCanvas* canvas, PdfTokenLooper** looper) {
-    SkPdfNativeObject* name = pdfContext->fObjectStack.top();    pdfContext->fObjectStack.pop();
+    EXPECT_OPERANDS(pdfContext, 1);
+    POP_NAME(pdfContext, name);
+    CHECK_PARAMETERS();
 
     SkPdfDictionary* xObject =  pdfContext->fGraphicsState.fResources->XObject(pdfContext->fPdfDoc);
 
     if (xObject == NULL) {
 #ifdef PDF_TRACE
         printf("XObject is NULL!\n");
 #endif
         return kIgnoreError_SkPdfResult;
     }
 
     SkPdfNativeObject* value = xObject->get(name);
     value = pdfContext->fPdfDoc->resolveReference(value);
 
 #ifdef PDF_TRACE
 //    value->ToString(str);
 //    printf("Do object value: %s\n", str);
 #endif
 
     return doXObject(pdfContext, canvas, value);
 }
 
 //tag MP Designate a marked-content point. tag is a name object indicating the role or
 //significance of the point.
 static SkPdfResult PdfOp_MP(SkPdfContext* pdfContext, SkCanvas* canvas, PdfTokenLooper** looper) {
-    pdfContext->fObjectStack.pop();
+    EXPECT_OPERANDS(pdfContext, 1);
+    POP_OBJ(pdfContext, tag);
+    CHECK_PARAMETERS();
+
+    if (tag == NULL) {
+        return kNYI_SkPdfResult;
+    }
 
     return kNYI_SkPdfResult;
 }
 
 //tag properties DP Designate a marked-content point with an associated property list. tag is a
 //name object indicating the role or significance of the point; properties is
 //either an inline dictionary containing the property list or a name object
 //associated with it in the Properties subdictionary of the current resource
 //dictionary (see Section 9.5.1, “Property Lists”).
 static SkPdfResult PdfOp_DP(SkPdfContext* pdfContext, SkCanvas* canvas, PdfTokenLooper** looper) {
-    pdfContext->fObjectStack.pop();
-    pdfContext->fObjectStack.pop();
+    EXPECT_OPERANDS(pdfContext, 2);
+    POP_OBJ(pdfContext, properties);
+    POP_OBJ(pdfContext, tag);
+    CHECK_PARAMETERS();
+
+    if (tag == NULL || properties == NULL) {
+        return kNYI_SkPdfResult;
+    }
 
     return kNYI_SkPdfResult;
 }
 
 //tag BMC Begin a marked-content sequence terminated by a balancing EMC operator.
 //tag is a name object indicating the role or significance of the sequence.
 static SkPdfResult PdfOp_BMC(SkPdfContext* pdfContext, SkCanvas* canvas, PdfTokenLooper** looper) {
-    pdfContext->fObjectStack.pop();
+    EXPECT_OPERANDS(pdfContext, 1);
+    POP_OBJ(pdfContext, tag);
+    CHECK_PARAMETERS();
+
+    if (tag == NULL) {
+        return kNYI_SkPdfResult;
+    }
 
     return kNYI_SkPdfResult;
 }
 
 //tag properties BDC Begin a marked-content sequence with an associated property list, terminated
 //by a balancing EMCoperator. tag is a name object indicating the role or significance of the sequence; propertiesis either an inline dictionary containing the
 //property list or a name object associated with it in the Properties subdictionary of the current resource dictionary (see Section 9.5.1, “Property Lists”).
 static SkPdfResult PdfOp_BDC(SkPdfContext* pdfContext, SkCanvas* canvas, PdfTokenLooper** looper) {
-    pdfContext->fObjectStack.pop();
-    pdfContext->fObjectStack.pop();
+    EXPECT_OPERANDS(pdfContext, 2);
+    POP_OBJ(pdfContext, properties);
+    POP_OBJ(pdfContext, tag);
+    CHECK_PARAMETERS();
+
+    if (tag == NULL || properties == NULL) {
+        return kNYI_SkPdfResult;
+    }
 
     return kNYI_SkPdfResult;
 }
 
 //— EMC End a marked-content sequence begun by a BMC or BDC operator.
 static SkPdfResult PdfOp_EMC(SkPdfContext* pdfContext, SkCanvas* canvas, PdfTokenLooper** looper) {
     return kNYI_SkPdfResult;
 }
 
 static void initPdfOperatorRenderes() {
@@ skipping 343 matching lines @@
 
     rect = SkRect::MakeWH(width, height);
 
     setup_bitmap(output, (int)SkScalarToDouble(width), (int)SkScalarToDouble(height));
 
     SkAutoTUnref<SkDevice> device(SkNEW_ARGS(SkDevice, (*output)));
     SkCanvas canvas(device);
 
     return renderer.renderPage(page, &canvas, rect);
 }