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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_
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