version-handler: Add session stat

We need to be able to inform the blob user of the readiness of blob data
and how large the contents are.

Change-Id: Ic90f6e344160b48e7e58cb009558586c7c2fab9b
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/bmc/version-handler/version_handler.cpp b/bmc/version-handler/version_handler.cpp
index 45d9b02..0b77f80 100644
--- a/bmc/version-handler/version_handler.cpp
+++ b/bmc/version-handler/version_handler.cpp
@@ -83,11 +83,7 @@
 
 bool VersionBlobHandler::stat(const std::string& path, blobs::BlobMeta* meta)
 {
-    // TODO: stat should return the blob state and in the meta data information
-    // on whether a read is successful should be contained
-    // do things like determine if systemd target is triggered
-    // then check if file can be opened for read
-    return false; /* not yet implemented */
+    return false;
 }
 
 bool VersionBlobHandler::open(uint16_t session, uint16_t flags,
@@ -151,7 +147,24 @@
 
 bool VersionBlobHandler::stat(uint16_t session, blobs::BlobMeta* meta)
 {
-    return false;
+    const auto& data = sessionInfoMap.at(session)->data;
+    if (data == nullptr)
+    {
+        meta->blobState = blobs::StateFlags::committing;
+        meta->size = 0;
+    }
+    else if (!*data)
+    {
+        meta->blobState = blobs::StateFlags::commit_error;
+        meta->size = 0;
+    }
+    else
+    {
+        meta->blobState =
+            blobs::StateFlags::committed | blobs::StateFlags::open_read;
+        meta->size = (*data)->size();
+    }
+    return true;
 }
 
 bool VersionBlobHandler::expire(uint16_t session)