Differential updates for components.

extensions/common/crx_file.cc

Index: extensions/common/crx_file.cc
diff --git a/extensions/common/crx_file.cc b/extensions/common/crx_file.cc
index 4f50962a5df65be3b789f4d95ac1dc0c2265e0f5..73e7f7b73d6b778f6f59286882726aa005ebf38b 100644
--- a/extensions/common/crx_file.cc
+++ b/extensions/common/crx_file.cc
@@ -11,6 +11,9 @@ namespace {
 // 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 @@ static const uint32 kMaxSignatureSize = 1 << 16;
 
 // The magic string embedded in the header.
 const char kCrxFileHeaderMagic[] = "Cr24";
+const char kCrxDiffFileHeaderMagic[] = "CrOD";

[cpu_(ooo_6.6-7.5), 2013/06/14 23:05:49]

in what ways is the differential crx different from a non-differential one?

Also can you add a section to the design doc about the differential updates? I
gave Sorin edit access to it.

[waffles, 2013/06/15 00:01:37]

There are two major format differences:
1. CrOD instead of Cr24 in the file header.
2. No manifest.json file (commands.json instead).

We wanted to be able to distinguish a patchfile from a normal CRX because normal
extension CRXs should do something sane when you click-and-drag the file intro
Chrome to install it. I'd prefer we had something in the header of a "diff file"
to indicate that it's something that this operation can't be done with - that
way you don't have to unzip it to figure out what it is.

 
 scoped_ptr<CrxFile> CrxFile::Parse(const CrxFile::Header& header,
                                    CrxFile::Error* error) {
@@ -45,12 +49,21 @@ scoped_ptr<CrxFile> CrxFile::Create(const uint32 key_size,
 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;