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/** |
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* This file is part of the CernVM File System. |
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*/ |
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#ifndef CVMFS_NETWORK_SINK_H_ |
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#define CVMFS_NETWORK_SINK_H_ |
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#include <stdint.h> |
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#include <string> |
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namespace cvmfs { |
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/** |
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* A data sink that behaves like a writable file descriptor with a custom |
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* implementation. |
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*/ |
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class Sink { |
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protected: |
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explicit Sink(bool is_owner) : is_owner_(is_owner) { } |
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public: |
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virtual ~Sink() { } |
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/** |
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* Appends data to the sink |
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* |
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* @returns on success: number of bytes written (can be less than requested) |
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* on failure: -errno. |
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*/ |
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virtual int64_t Write(const void *buf, uint64_t sz) = 0; |
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/** |
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* Truncate all written data and start over at position zero. |
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* |
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* @returns Success = 0 |
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* Failure = -errno |
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*/ |
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virtual int Reset() = 0; |
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/** |
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* Purges all resources leaving the sink in an invalid state. |
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* More aggressive version of Reset(). |
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* For some sinks and depending on owner status it might do |
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* the same as Reset(). |
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* |
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* @returns Success = 0 |
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* Failure = -errno |
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*/ |
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virtual int Purge() = 0; |
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/** |
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* @returns true if the object is correctly initialized. |
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*/ |
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virtual bool IsValid() = 0; |
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/** |
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* Release ownership of the sink's resource |
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*/ |
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void Release() { is_owner_ = false; } |
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/** |
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* Commit data to the sink |
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* @returns Success = 0 |
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* Failure = -errno |
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*/ |
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virtual int Flush() = 0; |
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/** |
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* Reserves new space in sinks that require reservation (see RequiresReserve) |
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* |
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* Successful if the requested size is smaller than already space reserved, or |
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* if the sink is the owner of the data and can allocate enough new space. |
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* |
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* @note If successful, always resets the current position to 0. |
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* |
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* Fails if |
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* 1) sink is not the owner of the data and more than the current size is |
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* requested |
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* 2) more space is requested than allowed (max_size_) |
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* |
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* @returns success = true |
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* failure = false |
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*/ |
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virtual bool Reserve(size_t size) = 0; |
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/** |
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* Returns if the specific sink type needs reservation of (data) space |
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* |
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* @returns true - reservation is needed |
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* false - no reservation is needed |
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*/ |
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virtual bool RequiresReserve() = 0; |
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/** |
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* Return a string representation describing the type of sink and its status |
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*/ |
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virtual std::string Describe() = 0; |
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protected: |
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bool is_owner_; |
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}; |
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} // namespace cvmfs |
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#endif // CVMFS_NETWORK_SINK_H_ |
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