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Commit d2ad53cf authored by Daniel Zheng's avatar Daniel Zheng
Browse files

Add CowOperationV2 

this is going to replace the current version of CowOperation and will
work with writer v2 and parser v2. This will be the on disk format of
the cow, while CowOperation will be updated to be the in memory format
of 15 bytes (implicitly will be the v3 version).

Test: m libsnapshot

Test: m libsnapshot
Change-Id: Ibd00ef014a9fc11cdf2bad97c52462db8eef9502
parent 55287774

fs_mgr/libsnapshot/include/libsnapshot/cow_format.h

+36 −0
Original line number Diff line number Diff line
@@ -143,6 +143,42 @@ struct CowOperation { 
    uint64_t source;

} __attribute__((packed));



// The on disk format of cow (currently ==  CowOperation)

struct CowOperationV2 {

    // The operation code (see the constants and structures below).

    uint8_t type;



    // If this operation reads from the data section of the COW, this contains

    // the compression type of that data (see constants below).

    uint8_t compression;



    // If this operation reads from the data section of the COW, this contains

    // the length.

    uint16_t data_length;



    // The block of data in the new image that this operation modifies.

    uint64_t new_block;



    // The value of |source| depends on the operation code.

    //

    // For copy operations, this is a block location in the source image.

    //

    // For replace operations, this is a byte offset within the COW's data

    // sections (eg, not landing within the header or metadata). It is an

    // absolute position within the image.

    //

    // For zero operations (replace with all zeroes), this is unused and must

    // be zero.

    //

    // For Label operations, this is the value of the applied label.

    //

    // For Cluster operations, this is the length of the following data region

    //

    // For Xor operations, this is the byte location in the source image.

    uint64_t source;

} __attribute__((packed));



static_assert(sizeof(CowOperationV2) == sizeof(CowOperation));

static_assert(sizeof(CowOperation) == sizeof(CowFooterOperation));



static constexpr uint8_t kCowCopyOp = 1;

fs_mgr/libsnapshot/include/libsnapshot/cow_reader.h

+0 −1
Original line number Diff line number Diff line
@@ -165,7 +165,6 @@ class CowReader final : public ICowReader { 
    void UpdateMergeOpsCompleted(int num_merge_ops) { header_.num_merge_ops += num_merge_ops; }



  private:

    bool ParseOps(std::optional<uint64_t> label);

    bool PrepMergeOps();

    uint64_t FindNumCopyops();

    uint8_t GetCompressionType(const CowOperation* op);