Unify the error checking of crypto::Encryptor and add WARN_UNUSED_RESULT to prevent misuse.

crypto/encryptor.cc

Index: crypto/encryptor.cc
diff --git a/crypto/encryptor.cc b/crypto/encryptor.cc
index 763dc2c1cb54764ab2428054f9585616f6decdde..69c8f2c7cb1ba330d8df53220ed348a563a4108f 100644
--- a/crypto/encryptor.cc
+++ b/crypto/encryptor.cc
@@ -94,7 +94,8 @@ bool Encryptor::GenerateCounterMask(size_t plaintext_len,
 
   const size_t kBlockLength = counter_->GetLengthInBytes();
   size_t blocks = (plaintext_len + kBlockLength - 1) / kBlockLength;
-  CHECK(blocks);
+  if (blocks == 0)
+    return false;

[wtc, 2011/12/15 02:03:58]

Should we also mark the GenerateCounterMask method with
WARN_UNUSED_RESULT?

It seems that we should support the encryption of nothing.
Does this failure return prevent us from supporting that?

[Ryan Sleevi, 2011/12/15 02:18:16]

Yes. It matches the previous CHECK, but empty plaintext in CTR mode is treated
as a failure.

[wtc, 2011/12/15 22:04:14]

Thanks for the explanation.  This is fine.

 
   *mask_len = blocks * kBlockLength;