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+// Copyright 2011 Google Inc. All Rights Reserved.
+
+#ifndef UTIL_SNAPPY_SNAPPY_SINKSOURCE_H_
+#define UTIL_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);
+
+ 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) { }
+  virtual ~ByteArraySource();
+  virtual size_t Available() const;
+  virtual const char* Peek(size_t* len);
+  virtual void Skip(size_t n);
+ 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) { }
+  virtual ~UncheckedByteArraySink();
+  virtual void Append(const char* data, size_t n);
+  virtual char* GetAppendBuffer(size_t len, char* scratch);
+
+  // 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_;
+};
+
+
+}
+
+#endif  // UTIL_SNAPPY_SNAPPY_SINKSOURCE_H_