Add specs for memcpy bugs.

(cherry picked from commit f63f261)

Author: aardvark179

spec/ruby/optional/capi/ext/string_spec.c

@@ -284,6 +284,26 @@ VALUE string_spec_RSTRING_PTR_iterate(VALUE self, VALUE str) {
   return Qnil;
 }
 
+VALUE string_spec_RSTRING_PTR_iterate_uint32(VALUE self, VALUE str) {
+  int i;
+  uint32_t* ptr;
+  int l = RSTRING_LEN(str) / sizeof(uint32_t);
+
+  ptr = (uint32_t *)RSTRING_PTR(str);
+  for(i = 0; i < l; i++) {
+    rb_yield(UINT2NUM(ptr[i]));
+  }
+  return Qnil;
+}
+
+VALUE string_spec_RSTRING_PTR_short_memcpy(VALUE self, VALUE str) {
+  // Short memcpy operations may be optimised by the compiler to a single write.
+  if (RSTRING_LEN(str) >= 8) {
+    memcpy(RSTRING_PTR(str), "Infinity", 8);
+  }
+  return str;
+}
+
 VALUE string_spec_RSTRING_PTR_assign(VALUE self, VALUE str, VALUE chr) {
   int i;
   char c;
@@ -477,6 +497,8 @@ void Init_string_spec(void) {
   rb_define_method(cls, "RSTRING_LEN", string_spec_RSTRING_LEN, 1);
   rb_define_method(cls, "RSTRING_LENINT", string_spec_RSTRING_LENINT, 1);
   rb_define_method(cls, "RSTRING_PTR_iterate", string_spec_RSTRING_PTR_iterate, 1);
+  rb_define_method(cls, "RSTRING_PTR_iterate_uint32", string_spec_RSTRING_PTR_iterate_uint32, 1);
+  rb_define_method(cls, "RSTRING_PTR_short_memcpy", string_spec_RSTRING_PTR_short_memcpy, 1);
   rb_define_method(cls, "RSTRING_PTR_assign", string_spec_RSTRING_PTR_assign, 2);
   rb_define_method(cls, "RSTRING_PTR_set", string_spec_RSTRING_PTR_set, 3);
   rb_define_method(cls, "RSTRING_PTR_after_funcall", string_spec_RSTRING_PTR_after_funcall, 2);

spec/ruby/optional/capi/string_spec.rb

@@ -513,6 +513,24 @@ def inspect
       end
       chars.should == [55, 48, 227, 131, 145, 227, 130, 175]
     end
+
+    it "returns a pointer which can be cast and used as another type" do
+      s = "70パク".
+        encode(Encoding::UTF_16LE).
+        force_encoding(Encoding::UTF_16LE).
+        encode(Encoding::UTF_8)
+
+      ints = []
+      @s.RSTRING_PTR_iterate_uint32(s) do |i|
+        ints << i
+      end
+      ints.should == s.unpack('LL')
+    end
+
+    it "allows a short memcpy to the string which may be converted to a single write operation by the compiler" do
+      str = "        "
+      @s.RSTRING_PTR_short_memcpy(str).should == "Infinity"
+    end
   end
 
   describe "RSTRING_LEN" do