Http cache: Fix handling of truncated entries.

- Always validate a truncated entry. Furthermore, given
that a server can say not-modified (304), followed  by
200 when actually asked for the final range, now we
validate truncated entries by asking for the next byte
that we need.

- If a server refuses to serve a byte range and instead
sends the whole resource, we just cache the response as
if nothing was stored before.

- If we receive a network error while reading from the
net, we don't discard the cached entry right away. Now
we wait until the transaction is closed, and attempt to
mark the entry as truncated.

BUG=48468
TEST=net_unittests

Review URL: http://codereview.chromium.org/6588105

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@76560 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 19 insertions, 12 deletions

diff --git a/net/http/partial_data.cc b/net/http/partial_data.cc
index 68d8048..c1f448e 100644
--- a/net/http/partial_data.cc
+++ b/net/http/partial_data.cc
@@ -111,6 +111,7 @@ PartialData::PartialData()
       final_range_(false),
       sparse_entry_(true),
       truncated_(false),
+      initial_validation_(false),
       core_(NULL),
       callback_(NULL) {
 }
@@ -153,7 +154,7 @@ void PartialData::RestoreHeaders(HttpRequestHeaders* headers) const {
               byte_range_.suffix_length() : byte_range_.last_byte_position();
 
   headers->CopyFrom(extra_headers_);
-  if (byte_range_.IsValid())
+  if (!truncated_ && byte_range_.IsValid())
     AddRangeHeader(current_range_start_, end, headers);
 }
 
@@ -178,13 +179,7 @@ int PartialData::ShouldValidateCache(disk_cache::Entry* entry,
       callback_ = callback;
       return ERR_IO_PENDING;
     }
-  } else if (truncated_) {
-    if (!current_range_start_) {
-      // Update the cached range only the first time.
-      cached_min_len_ = static_cast<int32>(byte_range_.first_byte_position());
-      cached_start_ = 0;
-    }
-  } else {
+  } else if (!truncated_) {
     if (byte_range_.HasFirstBytePosition() &&
         byte_range_.first_byte_position() >= resource_size_) {
       // The caller should take care of this condition because we should have
@@ -259,10 +254,14 @@ bool PartialData::UpdateFromStoredHeaders(const HttpResponseHeaders* headers,
       return false;
 
     truncated_ = true;
+    initial_validation_ = true;
     sparse_entry_ = false;
-    byte_range_.set_first_byte_position(entry->GetDataSize(kDataStream));
+    int current_len = entry->GetDataSize(kDataStream);
+    byte_range_.set_first_byte_position(current_len);
     resource_size_ = total_length;
-    current_range_start_ = 0;
+    current_range_start_ = current_len;
+    cached_min_len_ = current_len;
+    cached_start_ = current_len + 1;
     return true;
   }
 
@@ -284,12 +283,20 @@ bool PartialData::UpdateFromStoredHeaders(const HttpResponseHeaders* headers,
   return entry->CouldBeSparse();
 }
 
+void PartialData::SetRangeToStartDownload() {
+  DCHECK(truncated_);
+  DCHECK(!sparse_entry_);
+  current_range_start_ = 0;
+  cached_start_ = 0;
+  initial_validation_ = false;
+}
+
 bool PartialData::IsRequestedRangeOK() {
   if (byte_range_.IsValid()) {
-    if (truncated_)
-      return true;
     if (!byte_range_.ComputeBounds(resource_size_))
       return false;
+    if (truncated_)
+      return true;
 
     if (current_range_start_ < 0)
       current_range_start_ = byte_range_.first_byte_position();