Update helper-select.i

1. added missing Py_DECREF for early-continue branch
2. PyLong_FromLong(i) instead of cast
3. added necessary comments
4.improved readability

Author: Mohataseem89

src_classic/helper-select.i

@@ -9,55 +9,98 @@
 # maintained and developed by Artifex Software, Inc. https://artifex.com.
 # ------------------------------------------------------------------------
 */
+
+
 void remove_dest_range(fz_context *ctx, pdf_document *pdf, PyObject *numbers)
 {
     fz_try(ctx) {
-        int i, j, pno, len, pagecount = pdf_count_pages(ctx, pdf);
+        int i, j, pno, len;
+        int pagecount = pdf_count_pages(ctx, pdf);
         PyObject *n1 = NULL;
         pdf_obj *target, *annots, *pageref, *o, *action, *dest;
+
         for (i = 0; i < pagecount; i++) {
-            n1 = PyLong_FromLong((long) i);
-            if (PySet_Contains(numbers, n1)) {
+
+            /* Create page index Python int */
+            n1 = PyLong_FromLong(i);
+            if (!n1) {
+                fz_throw(ctx, FZ_ERROR_GENERIC, "Out of memory in PyLong_FromLong");
+            }
+
+            int contains = PySet_Contains(numbers, n1);
+            if (contains == -1) {
+                Py_DECREF(n1);
+                fz_throw(ctx, FZ_ERROR_GENERIC, "PySet_Contains failed");
+            }
+
+            if (contains) {
                 Py_DECREF(n1);
                 continue;
             }
             Py_DECREF(n1);
 
             pageref = pdf_lookup_page_obj(ctx, pdf, i);
             annots = pdf_dict_get(ctx, pageref, PDF_NAME(Annots));
-            if (!annots) continue;
+            if (!annots) {
+                continue;
+            }
+
             len = pdf_array_len(ctx, annots);
-            for (j = len - 1; j >= 0; j -= 1) {
+
+            /* Iterate backwards to safely delete array entries */
+            for (j = len - 1; j >= 0; j--) {
+
                 o = pdf_array_get(ctx, annots, j);
-                if (!pdf_name_eq(ctx, pdf_dict_get(ctx, o, PDF_NAME(Subtype)), PDF_NAME(Link))) {
+
+                if (!pdf_name_eq(ctx,
+                                 pdf_dict_get(ctx, o, PDF_NAME(Subtype)),
+                                 PDF_NAME(Link))) {
                     continue;
                 }
+
                 action = pdf_dict_get(ctx, o, PDF_NAME(A));
-                dest =  pdf_dict_get(ctx, o, PDF_NAME(Dest));
+                dest   = pdf_dict_get(ctx, o, PDF_NAME(Dest));
+
                 if (action) {
-                    if (!pdf_name_eq(ctx, pdf_dict_get(ctx, action,
-                        PDF_NAME(S)), PDF_NAME(GoTo)))
+                    if (!pdf_name_eq(ctx,
+                                     pdf_dict_get(ctx, action, PDF_NAME(S)),
+                                     PDF_NAME(GoTo))) {
                         continue;
+                    }
                     dest = pdf_dict_get(ctx, action, PDF_NAME(D));
                 }
+
                 pno = -1;
                 if (pdf_is_array(ctx, dest)) {
                     target = pdf_array_get(ctx, dest, 0);
                     pno = pdf_lookup_page_number(ctx, pdf, target);
+
+                } else if (pdf_is_string(ctx, dest)) {
+                    fz_location loc = fz_resolve_link(ctx, &pdf->super,
+                                         pdf_to_text_string(ctx, dest),
+                                         NULL, NULL);
+                    pno = loc.page;
                 }
-                else if (pdf_is_string(ctx, dest)) {
-                    fz_location location = fz_resolve_link(ctx, &pdf->super,
-                                            pdf_to_text_string(ctx, dest),
-                                            NULL, NULL);
-                    pno = location.page;
+
+                if (pno < 0) {
+                    continue; /* could not resolve link target */
                 }
-                if (pno < 0) { // page number lookup did not work
-                    continue;
+
+                n1 = PyLong_FromLong(pno);
+                if (!n1) {
+                    fz_throw(ctx, FZ_ERROR_GENERIC, "Out of memory in PyLong_FromLong");
+                }
+
+                contains = PySet_Contains(numbers, n1);
+                if (contains == -1) {
+                    Py_DECREF(n1);
+                    fz_throw(ctx, FZ_ERROR_GENERIC, "PySet_Contains failed");
                 }
-                n1 = PyLong_FromLong((long) pno);
-                if (PySet_Contains(numbers, n1)) {
+
+                if (contains) {
                     pdf_array_delete(ctx, annots, j);
                 }
+
                 Py_DECREF(n1);
             }
         }