Add OBB flags to support overlays

* Add flags field in OBB footer to support overlays.

* Remove unused 'crypto' and 'filesystem' fields in obbtool (could
  later be supported in the "flags" field of the OBB footer).

* Add notes to document OBB classes before shipping.

Change-Id: I386b43c32c5edef55210acb5d3322639c08010ba

2 files changed, 53 insertions, 14 deletions

diff --git a/include/utils/ObbFile.h b/include/utils/ObbFile.h
index d2ca82eb55..5243f50051 100644
--- a/include/utils/ObbFile.h
+++ b/include/utils/ObbFile.h
@@ -18,12 +18,16 @@
 #define OBBFILE_H_
 
 #include <stdint.h>
+#include <strings.h>
 
 #include <utils/RefBase.h>
 #include <utils/String8.h>
 
 namespace android {
 
+// OBB flags (bit 0)
+#define OBB_OVERLAY         (1 << 0)
+
 class ObbFile : public RefBase {
 protected:
     virtual ~ObbFile();
@@ -46,18 +50,38 @@ public:
         return mPackageName;
     }
 
-    int32_t getVersion() const {
-        return mVersion;
-    }
-
     void setPackageName(String8 packageName) {
         mPackageName = packageName;
     }
 
+    int32_t getVersion() const {
+        return mVersion;
+    }
+
     void setVersion(int32_t version) {
         mVersion = version;
     }
 
+    int32_t getFlags() const {
+        return mFlags;
+    }
+
+    void setFlags(int32_t flags) {
+        mFlags = flags;
+    }
+
+    bool isOverlay() {
+        return (mFlags & OBB_OVERLAY) == OBB_OVERLAY;
+    }
+
+    void setOverlay(bool overlay) {
+        if (overlay) {
+            mFlags |= OBB_OVERLAY;
+        } else {
+            mFlags &= ~OBB_OVERLAY;
+        }
+    }
+
     static inline uint32_t get4LE(const unsigned char* buf) {
         return buf[0] | (buf[1] << 8) | (buf[2] << 16) | (buf[3] << 24);
     }
@@ -76,6 +100,9 @@ private:
     /* Package version this ObbFile is associated with */
     int32_t mVersion;
 
+    /* Flags for this OBB type. */
+    int32_t mFlags;
+
     const char* mFileName;
 
     size_t mFileSize;
diff --git a/libs/utils/ObbFile.cpp b/libs/utils/ObbFile.cpp
index adedf0c5d0..e170ab88c1 100644
--- a/libs/utils/ObbFile.cpp
+++ b/libs/utils/ObbFile.cpp
@@ -29,12 +29,13 @@
 
 #define kFooterTagSize 8  /* last two 32-bit integers */
 
-#define kFooterMinSize 21 /* 32-bit signature version
-                           * 32-bit package version
-                           * 32-bit package name size
-                           * 1-character package name
-                           * 32-bit footer size
-                           * 32-bit footer marker
+#define kFooterMinSize 25 /* 32-bit signature version (4 bytes)
+                           * 32-bit package version (4 bytes)
+                           * 32-bit flags (4 bytes)
+                           * 32-bit package name size (4-bytes)
+                           * >=1-character package name (1 byte)
+                           * 32-bit footer size (4 bytes)
+                           * 32-bit footer marker (4 bytes)
                            */
 
 #define kMaxBufSize    32768 /* Maximum file read buffer */
@@ -45,8 +46,9 @@
 
 /* offsets in version 1 of the header */
 #define kPackageVersionOffset 4
-#define kPackageNameLenOffset 8
-#define kPackageNameOffset    12
+#define kFlagsOffset          8
+#define kPackageNameLenOffset 12
+#define kPackageNameOffset    16
 
 /*
  * TEMP_FAILURE_RETRY is defined by some, but not all, versions of
@@ -78,7 +80,10 @@ typedef off64_t my_off64_t;
 namespace android {
 
 ObbFile::ObbFile() :
-        mVersion(-1) {
+        mPackageName(""),
+        mVersion(-1),
+        mFlags(0)
+{
 }
 
 ObbFile::~ObbFile() {
@@ -199,6 +204,7 @@ bool ObbFile::parseObbFile(int fd)
     }
 
     mVersion = (int32_t) get4LE((unsigned char*)scanBuf + kPackageVersionOffset);
+    mFlags = (int32_t) get4LE((unsigned char*)scanBuf + kFlagsOffset);
 
     uint32_t packageNameLen = get4LE((unsigned char*)scanBuf + kPackageNameLenOffset);
     if (packageNameLen <= 0
@@ -268,6 +274,12 @@ bool ObbFile::writeTo(int fd)
         return false;
     }
 
+    put4LE(intBuf, mFlags);
+    if (write(fd, &intBuf, sizeof(uint32_t)) != (ssize_t)sizeof(uint32_t)) {
+        LOGW("couldn't write package version");
+        return false;
+    }
+
     size_t packageNameLen = mPackageName.size();
     put4LE(intBuf, packageNameLen);
     if (write(fd, &intBuf, sizeof(uint32_t)) != (ssize_t)sizeof(uint32_t)) {
@@ -280,7 +292,7 @@ bool ObbFile::writeTo(int fd)
         return false;
     }
 
-    put4LE(intBuf, 3*sizeof(uint32_t) + packageNameLen);
+    put4LE(intBuf, kPackageNameOffset + packageNameLen);
     if (write(fd, &intBuf, sizeof(uint32_t)) != (ssize_t)sizeof(uint32_t)) {
         LOGW("couldn't write footer size: %s", strerror(errno));
         return false;