Allow 0-valued string fields

io/fields.cc

@@ -64,16 +64,6 @@ class VisitorBase : public IFieldsVisitor {
     }
     return true;
   }
-
-  bool CheckStringU32(uint32_t u32, uint32_t i, uint32_t num_u32) {
-    // Although strings are zero-padded to u32, an entire u32 should not be
-    // zero.
-    if (HWY_UNLIKELY(u32 == 0)) {
-      NotifyInvalid("Invalid characters %x at %u of %u\n", u32, i, num_u32);
-      return false;
-    }
-    return true;
-  }
 };
 
 class PrintVisitor : public VisitorBase {
@@ -170,7 +160,6 @@ class ReadVisitor : public VisitorBase {
     for (uint32_t i = 0; i < num_u32; ++i) {
       uint32_t u32;
       operator()(u32);
-      (void)CheckStringU32(u32, i, num_u32);
       hwy::CopyBytes(&u32, value.data() + i * k4, k4);
     }
 
@@ -278,7 +267,6 @@ class WriteVisitor : public VisitorBase {
     for (uint32_t i = 0; i < num_whole_u32; ++i) {
       uint32_t u32 = 0;
       hwy::CopyBytes(value.data() + i * k4, &u32, k4);
-      if (HWY_UNLIKELY(!CheckStringU32(u32, i, num_u32))) return;
       storage_.push_back(u32);
     }
 
@@ -292,7 +280,6 @@ class WriteVisitor : public VisitorBase {
         const uint32_t next = static_cast<uint32_t>(static_cast<uint8_t>(c));
         u32 += next << (i * 8);
       }
-      if (HWY_UNLIKELY(!CheckStringU32(u32, num_whole_u32, num_u32))) return;
       storage_.push_back(u32);
     }
   }

io/fields_test.cc

@@ -280,9 +280,6 @@ TEST(FieldsTest, TestInvalidFloat) {
 // Refuse to write invalid strings.
 TEST(FieldsTest, TestInvalidString) {
   NewFields new_fields;
-  // Four zero bytes
-  new_fields.new_str.assign(4, '\0');
-  EXPECT_TRUE(new_fields.Write().empty());
 
   // Too long
   new_fields.new_str.assign(257, 'a');