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, 12 insertions, 6 deletions

diff --git a/src/io.cc b/src/io.cc
index 44970fe..99c0518 100644
--- a/src/io.cc
+++ b/src/io.cc
@@ -39,6 +39,8 @@ class BasicReader : public Reader {
         default:
           return std::unexpected(ReadError::Error);
       }
+    } else if (ret == 0 && max > 0) {
+      return std::unexpected(ReadError::Eof);
     }
     offset_ += ret;
     return ret;
@@ -60,7 +62,7 @@ class BasicReader : public Reader {
       return std::unexpected(ReadError::Error);
     }
     // Don't want skip to go past (cached) file end.
-    if (!size_.has_value() || ret > size_.value()) {
+    if (!size_.has_value() || ret >= size_.value()) {
       // When going past end, double check that it still is the end.
       off_t ret2 = lseek(fd_.get(), 0, SEEK_END);
       if (ret2 < 0) {
@@ -71,9 +73,11 @@ class BasicReader : public Reader {
         return std::unexpected(ReadError::Error);
       }
       size_ = ret2;
-      if (ret > ret2) {
+      if (ret >= ret2) {
         auto distance = ret2 - offset_;
         offset_ = ret2;
+        if (distance == 0 && max > 0)
+          return std::unexpected(ReadError::Eof);
         return distance;
       }
       // Seek back to where we should be
@@ -99,6 +103,8 @@ class MemoryReader : public Reader {
   [[nodiscard]]
   std::expected<size_t, ReadError> read(void* dst, size_t max) override {
     size_t avail = size_ - offset_;
+    if (avail == 0 && max > 0)
+      return std::unexpected(io::ReadError::Eof);
     size_t ret = std::min(max, avail);
     memcpy(dst, reinterpret_cast<char*>(ptr_) + offset_, ret);
     offset_ += ret;
@@ -147,14 +153,14 @@ class StringReader : public MemoryReader {
 
 std::expected<size_t, ReadError> Reader::repeat_read(void* dst, size_t max) {
   auto ret = read(dst, max);
-  if (!ret.has_value() || ret.value() == 0 || ret.value() == max)
+  if (!ret.has_value() || ret.value() == max)
     return ret;
 
   char* d = reinterpret_cast<char*>(dst);
   size_t offset = ret.value();
   while (true) {
     ret = read(d + offset, max - offset);
-    if (!ret.has_value() || ret.value() == 0)
+    if (!ret.has_value())
       break;
     offset += ret.value();
     if (offset == max)
@@ -165,13 +171,13 @@ std::expected<size_t, ReadError> Reader::repeat_read(void* dst, size_t max) {
 
 std::expected<size_t, ReadError> Reader::repeat_skip(size_t max) {
   auto ret = skip(max);
-  if (!ret.has_value() || ret.value() == 0 || ret.value() == max)
+  if (!ret.has_value() || ret.value() == max)
     return ret;
 
   size_t offset = ret.value();
   while (true) {
     ret = skip(max - offset);
-    if (!ret.has_value() || ret.value() == 0)
+    if (!ret.has_value())
       break;
     offset += ret.value();
     if (offset == max)