Change io::Reader and company to return ReadError::Eof instead of 0.

It's debatable if Eof should be considered an error or not.
But it is pretty clear it generally is a special response that
needs special handling, so easier to keep with the unexpected lot.

Also keeps better at higher abstraction levels, such as the line
reader.

1 files changed, 7 insertions, 2 deletions

diff --git a/src/uio.cc b/src/uio.cc
index 9fc22c1..da943a2 100644
--- a/src/uio.cc
+++ b/src/uio.cc
@@ -50,6 +50,11 @@ class UnicodeReader : public io::Reader {
             return std::unexpected(io::ReadError::InvalidData);
           break;
         case u::ReadError::End:
+          if (in_eof_) {
+            // Only return eof if we have no bytes to output.
+            if (u_buffer_wptr_ == u_buffer_)
+              return std::unexpected(io::ReadError::Eof);
+          }
           break;
         case u::ReadError::Incomplete:
           if (in_eof_) {
@@ -106,8 +111,8 @@ class UnicodeReader : public io::Reader {
       auto got = in_->read(wptr, in_avail_);
       if (got.has_value()) {
         byte_buffer_->commit(got.value());
-        if (got.value() == 0)
-          in_eof_ = true;
+      } else if (got.error() == io::ReadError::Eof) {
+        in_eof_ = true;
       } else {
         return got.error();
       }