Merge pull request #1205 from herwinw/io_read_0_bytes

spec/core/io/read_spec.rb

@@ -295,9 +295,7 @@
   end
 
   it "consumes zero bytes when reading zero bytes" do
-    NATFIXME 'Empty string when reading zero bytes', exception: SpecFailedException do
-      @io.read(0).should == ''
-    end
+    @io.read(0).should == ''
     @io.pos.should == 0
 
     NATFIXME 'Implement IO#getc', exception: NoMethodError, message: "undefined method `getc'" do

src/io_object.cpp

@@ -178,31 +178,37 @@ Value IoObject::write_file(Env *env, Value filename, Value string) {
 
 Value IoObject::read(Env *env, Value count_value) const {
     raise_if_closed(env);
-    size_t bytes_read;
+    ssize_t bytes_read;
     if (count_value && !count_value->is_nil()) {
         count_value->assert_type(env, Object::Type::Integer, "Integer");
         int count = count_value->as_integer()->to_nat_int_t();
         if (count < 0)
             env->raise("ArgumentError", "negative length {} given", count);
         char *buf = new char[count + 1];
+        auto buf_cleanup = Defer([&]() { delete[] buf; });
         bytes_read = ::read(m_fileno, buf, count);
-        if (bytes_read == 0) {
-            delete[] buf;
+        if (bytes_read < 0) {
+            env->raise_errno();
+        } else if (bytes_read == 0) {
+            if (count == 0)
+                return new StringObject {};
             return NilObject::the();
         } else {
-            Value result = new StringObject { buf, bytes_read };
-            delete[] buf;
+            Value result = new StringObject { buf, static_cast<size_t>(bytes_read) };
             return result;
         }
     }
     char buf[NAT_READ_BYTES + 1];
     bytes_read = ::read(m_fileno, buf, NAT_READ_BYTES);
-    if (bytes_read == 0) {
+    if (bytes_read < 0) {
+        env->raise_errno();
+    } else if (bytes_read == 0) {
         return new StringObject { "" };
     }
-    StringObject *str = new StringObject { buf, bytes_read };
+    StringObject *str = new StringObject { buf, static_cast<size_t>(bytes_read) };
     while (1) {
         bytes_read = ::read(m_fileno, buf, NAT_READ_BYTES);
+        if (bytes_read < 0) env->raise_errno();
         if (bytes_read == 0) break;
         buf[bytes_read] = 0;
         str->append(buf, bytes_read);