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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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