fix: writebuffer size not include the null terminating (#72)

writebuffer not include the null terminating char

Author: liuq19

include/sonic/writebuffer.h

@@ -42,7 +42,8 @@ class WriteBuffer {
    * thread-safe.
    */
   sonic_force_inline const char* ToString() const {
-    stack_.Push('\0');
+    stack_.Grow(1);
+    *(stack_.template End<char>()) = '\0';
     return stack_.Begin<char>();
   }
 

tests/writebuffer_test.cpp

@@ -89,4 +89,22 @@ TEST(WriteBuffer, ToString) {
     EXPECT_STREQ(cwb.ToString(), "c");
   }
 }
+
+TEST(WriteBuffer, StringSize) {
+  {
+    WriteBuffer wb;
+    wb.Push<char>('c');
+    auto s = std::string(wb.ToString(), wb.Size());
+    EXPECT_EQ(wb.Size(), 1);
+    EXPECT_EQ(s.size(), 1);
+    EXPECT_STREQ(s.c_str(), "c");
+  }
+  {
+    WriteBuffer wb;
+    auto s = std::string(wb.ToString(), wb.Size());
+    EXPECT_EQ(wb.Size(), 0);
+    EXPECT_EQ(s.size(), 0);
+    EXPECT_STREQ(s.c_str(), "");
+  }
+}
 }  // namespace