Use If-Range instead of If-Match/If-Unmodified-Since for partial requests.
If-Range can shortcut partial resumption requests by having the server
respond with the entire entity if there's a validator mismatch. This
cuts down resumptions by one roundtrip.
The If-Range has been in use by HttpCacheTransaction successfully and it
is not believed that availability of support is a concern.
[email protected],[email protected],[email protected],[email protected],[email protected]
BUG=7648
Review URL: https://codereview.chromium.org/1444253003
Cr-Commit-Position: refs/heads/master@{#362771}
diff --git a/content/browser/download/download_manager_impl.cc b/content/browser/download/download_manager_impl.cc
index 6a98bc2..95ce596 100644
--- a/content/browser/download/download_manager_impl.cc
+++ b/content/browser/download/download_manager_impl.cc
@@ -88,20 +88,21 @@
// We shouldn't be asked to continue if we don't have a verifier.
DCHECK(params->offset() == 0 || has_etag || has_last_modified);
- if (params->offset() > 0) {
+ if (params->offset() > 0 && (has_etag || has_last_modified)) {
request->SetExtraRequestHeaderByName(
"Range",
base::StringPrintf("bytes=%" PRId64 "-", params->offset()),
true);
- if (has_last_modified) {
- request->SetExtraRequestHeaderByName("If-Unmodified-Since",
- params->last_modified(),
- true);
- }
- if (has_etag) {
- request->SetExtraRequestHeaderByName("If-Match", params->etag(), true);
- }
+ // In accordance with RFC 2616 Section 14.27, use If-Range to specify that
+ // the server return the entire entity if the validator doesn't match.
+ // Last-Modified can be used in the absence of ETag as a validator if the
+ // response headers satisfied the HttpUtil::HasStrongValidators() predicate.
+ //
+ // This function assumes that HasStrongValidators() was true and that the
+ // ETag and Last-Modified header values supplied are valid.
+ request->SetExtraRequestHeaderByName(
+ "If-Range", has_etag ? params->etag() : params->last_modified(), true);
}
for (DownloadUrlParameters::RequestHeadersType::const_iterator iter
