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 // Copyright 2011 Google Inc. All Rights Reserved.
 //
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 // notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 // copyright notice, this list of conditions and the following disclaimer
 // in the documentation and/or other materials provided with the
 // distribution.
 //     * Neither the name of Google Inc. nor the names of its
 // contributors may be used to endorse or promote products derived from
 // this software without specific prior written permission.
 //
 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 #ifndef THIRD_PARTY_SNAPPY_SNAPPY_SINKSOURCE_H_
 #define THIRD_PARTY_SNAPPY_SNAPPY_SINKSOURCE_H_
 
 #include <stddef.h>
 
 namespace snappy {
 
 // A Sink is an interface that consumes a sequence of bytes.
 class Sink {
  public:
   Sink() { }
   virtual ~Sink();
 
   // Append "bytes[0,n-1]" to this.
   virtual void Append(const char* bytes, size_t n) = 0;
 
   // Returns a writable buffer of the specified length for appending.
   // May return a pointer to the caller-owned scratch buffer which
   // must have at least the indicated length.  The returned buffer is
   // only valid until the next operation on this Sink.
   //
   // After writing at most "length" bytes, call Append() with the
   // pointer returned from this function and the number of bytes
   // written.  Many Append() implementations will avoid copying
   // bytes if this function returned an internal buffer.
   //
   // If a non-scratch buffer is returned, the caller may only pass a
   // prefix of it to Append().  That is, it is not correct to pass an
   // interior pointer of the returned array to Append().
   //
   // The default implementation always returns the scratch buffer.
   virtual char* GetAppendBuffer(size_t length, char* scratch);
 
   // For higher performance, Sink implementations can provide custom
   // AppendAndTakeOwnership() and GetAppendBufferVariable() methods.
   // These methods can reduce the number of copies done during
   // compression/decompression.
 
   // Append "bytes[0,n-1] to the sink. Takes ownership of "bytes"
   // and calls the deleter function as (*deleter)(deleter_arg, bytes, n)
   // to free the buffer. deleter function must be non NULL.
   //
   // The default implementation just calls Append and frees "bytes".
   // Other implementations may avoid a copy while appending the buffer.
   virtual void AppendAndTakeOwnership(
       char* bytes, size_t n, void (*deleter)(void*, const char*, size_t),
       void *deleter_arg);
 
   // Returns a writable buffer for appending and writes the buffer's capacity to
   // *allocated_size. Guarantees *allocated_size >= min_size.
   // May return a pointer to the caller-owned scratch buffer which must have
   // scratch_size >= min_size.
   //
   // The returned buffer is only valid until the next operation
   // on this ByteSink.
   //
   // After writing at most *allocated_size bytes, call Append() with the
   // pointer returned from this function and the number of bytes written.
   // Many Append() implementations will avoid copying bytes if this function
   // returned an internal buffer.
   //
   // If the sink implementation allocates or reallocates an internal buffer,
   // it should use the desired_size_hint if appropriate. If a caller cannot
   // provide a reasonable guess at the desired capacity, it should set
   // desired_size_hint = 0.
   //
   // If a non-scratch buffer is returned, the caller may only pass
   // a prefix to it to Append(). That is, it is not correct to pass an
   // interior pointer to Append().
   //
   // The default implementation always returns the scratch buffer.
   virtual char* GetAppendBufferVariable(
       size_t min_size, size_t desired_size_hint, char* scratch,
       size_t scratch_size, size_t* allocated_size);
 
  private:
   // No copying
   Sink(const Sink&);
   void operator=(const Sink&);
 };
 
 // A Source is an interface that yields a sequence of bytes
 class Source {
  public:
   Source() { }
   virtual ~Source();
 
   // Return the number of bytes left to read from the source
   virtual size_t Available() const = 0;
 
   // Peek at the next flat region of the source.  Does not reposition
   // the source.  The returned region is empty iff Available()==0.
   //
   // Returns a pointer to the beginning of the region and store its
   // length in *len.
   //
   // The returned region is valid until the next call to Skip() or
   // until this object is destroyed, whichever occurs first.
   //
   // The returned region may be larger than Available() (for example
   // if this ByteSource is a view on a substring of a larger source).
   // The caller is responsible for ensuring that it only reads the
   // Available() bytes.
   virtual const char* Peek(size_t* len) = 0;
 
   // Skip the next n bytes.  Invalidates any buffer returned by
   // a previous call to Peek().
   // REQUIRES: Available() >= n
   virtual void Skip(size_t n) = 0;
 
  private:
   // No copying
   Source(const Source&);
   void operator=(const Source&);
 };
 
 // A Source implementation that yields the contents of a flat array
 class ByteArraySource : public Source {
  public:
   ByteArraySource(const char* p, size_t n) : ptr_(p), left_(n) { }
   ~ByteArraySource() override;
   size_t Available() const override;
   const char* Peek(size_t* len) override;
   void Skip(size_t n) override;
  private:
   const char* ptr_;
   size_t left_;
 };
 
 // A Sink implementation that writes to a flat array without any bound checks.
 class UncheckedByteArraySink : public Sink {
  public:
   explicit UncheckedByteArraySink(char* dest) : dest_(dest) { }
   ~UncheckedByteArraySink() override;
   void Append(const char* data, size_t n) override;
   char* GetAppendBuffer(size_t len, char* scratch) override;
   char* GetAppendBufferVariable(
       size_t min_size, size_t desired_size_hint, char* scratch,
       size_t scratch_size, size_t* allocated_size) override;
   void AppendAndTakeOwnership(
       char* bytes, size_t n, void (*deleter)(void*, const char*, size_t),
       void *deleter_arg) override;
 
   // Return the current output pointer so that a caller can see how
   // many bytes were produced.
   // Note: this is not a Sink method.
   char* CurrentDestination() const { return dest_; }
  private:
   char* dest_;
 };
 
 }  // namespace snappy
 
 #endif  // THIRD_PARTY_SNAPPY_SNAPPY_SINKSOURCE_H_

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