cbor: have one Read function wrap the other.

This is a trivial matter but makes a bit more sense when I make the
inner Read call a little more complex in the next change.

Change-Id: Ie1c19e8760a598cf36914e634037c519e7f78d72
Reviewed-on: https://chromium-review.googlesource.com/990194Reviewed-by: Balazs Engedy <engedy@chromium.org>
Commit-Queue: Adam Langley <agl@chromium.org>
Cr-Commit-Position: refs/heads/master@{#547569}

components/cbor/cbor_reader.cc

@@ -66,17 +66,16 @@ CBORReader::~CBORReader() {}
 base::Optional<CBORValue> CBORReader::Read(base::span<uint8_t const> data,
                                            DecoderError* error_code_out,
                                            int max_nesting_level) {
-  CBORReader reader(data.cbegin(), data.cend());
-  base::Optional<CBORValue> decoded_cbor =
-      reader.DecodeCompleteDataItem(max_nesting_level);
-
-  if (decoded_cbor)
-    reader.CheckExtraneousData();
-  if (error_code_out)
-    *error_code_out = reader.GetErrorCode();
+  size_t num_bytes_consumed;
+  auto decoded_cbor =
+      Read(data, &num_bytes_consumed, error_code_out, max_nesting_level);
 
-  if (reader.GetErrorCode() != DecoderError::CBOR_NO_ERROR)
+  if (decoded_cbor && num_bytes_consumed != data.size()) {
+    if (error_code_out)
+      *error_code_out = DecoderError::EXTRANEOUS_DATA;
     return base::nullopt;
+  }
+
   return decoded_cbor;
 }
 
@@ -340,11 +339,6 @@ bool CBORReader::CheckMinimalEncoding(uint8_t additional_bytes,
   return true;
 }
 
-void CBORReader::CheckExtraneousData() {
-  if (it_ != end_)
-    error_code_ = DecoderError::EXTRANEOUS_DATA;
-}
-
 bool CBORReader::HasValidUTF8Format(const std::string& string_data) {
   if (!base::IsStringUTF8(string_data)) {
     error_code_ = DecoderError::INVALID_UTF8;

components/cbor/cbor_reader.h

@@ -140,7 +140,6 @@ class CBOR_EXPORT CBORReader {
   base::Optional<CBORValue> ReadMapContent(const DataItemHeader& header,
                                            int max_nesting_level);
   bool CanConsume(uint64_t bytes);
-  void CheckExtraneousData();
   bool HasValidUTF8Format(const std::string& string_data);
   bool CheckOutOfOrderKey(const CBORValue& new_key, CBORValue::MapValue* map);
   bool CheckMinimalEncoding(uint8_t additional_bytes, uint64_t uint_data);