Differential updates for components.

extensions/common/crx_file.cc

Index: extensions/common/crx_file.cc
===================================================================
--- extensions/common/crx_file.cc	(revision 201835)
+++ extensions/common/crx_file.cc	(working copy)
@@ -11,6 +11,9 @@
 // The current version of the crx format.
 static const uint32 kCurrentVersion = 2;
 
+// The current version of the crx diff format.
+static const uint32 kCurrentDiffVersion = 0;
+
 // The maximum size the crx parser will tolerate for a public key.
 static const uint32 kMaxPublicKeySize = 1 << 16;
 
@@ -21,6 +24,7 @@
 
 // The magic string embedded in the header.
 const char kCrxFileHeaderMagic[] = "Cr24";
+const char kCrxDiffFileHeaderMagic[] = "CrOD";
 
 scoped_ptr<CrxFile> CrxFile::Parse(const CrxFile::Header& header,
                                    CrxFile::Error* error) {
@@ -45,12 +49,21 @@
 CrxFile::CrxFile(const Header& header) : header_(header) {
 }
 
+bool CrxFile::HeaderIsDelta(const CrxFile::Header& header) {
+  return !strncmp(kCrxDiffFileHeaderMagic, header.magic, sizeof(header.magic));
+}
+
 bool CrxFile::HeaderIsValid(const CrxFile::Header& header,
                             CrxFile::Error* error) {
   bool valid = false;
-  if (strncmp(kCrxFileHeaderMagic, header.magic, sizeof(header.magic)))
+  bool diffCrx = false;
+  if (!strncmp(kCrxDiffFileHeaderMagic, header.magic, sizeof(header.magic)))
+    diffCrx = true;
+  if (strncmp(kCrxFileHeaderMagic, header.magic, sizeof(header.magic)) &&
+      !diffCrx)
     *error = kWrongMagic;
-  else if (header.version != kCurrentVersion)
+  else if (header.version != kCurrentVersion
+      && !(diffCrx && header.version == kCurrentDiffVersion))
     *error = kInvalidVersion;
   else if (header.key_size > kMaxPublicKeySize)
     *error = kInvalidKeyTooLarge;