// Copyright 2008, Google Inc.
//
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// modification, are permitted provided that the following conditions are met:
//
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//     this list of conditions and the following disclaimer.
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#ifndef GEARS_BLOB_BLOB_INTERFACE_H__
#define GEARS_BLOB_BLOB_INTERFACE_H__

#ifdef OFFICIAL_BUILD
// The blob API has not been finalized for official builds
#else

#include "gears/base/common/common.h"
#include "gears/base/common/scoped_refptr.h"

class BlobInterface : public RefCounted {
 public:
  // Reads up to max_bytes from the blob beginning at the absolute position
  // indicated by offset, and writes the data into destination.  Multiple Reads
  // are unrelated.  Returns the number of bytes successfully read, or -1 on
  // error.  A null destination or negative offset or max_bytes will result in
  // an error.  An offset beyond the end of the stream will succeed and return 0
  // bytes.
  virtual int64 Read(uint8 *destination, int64 offset,
                     int64 max_bytes) const = 0;

  // Note that Length can be volatile, e.g. a file-backed Blob can have that
  // file's size change underneath it.
  virtual int64 Length() const = 0;

 protected:
  BlobInterface() {}
  virtual ~BlobInterface() {}

 private:
  DISALLOW_EVIL_CONSTRUCTORS(BlobInterface);
};

class EmptyBlob : public BlobInterface {
 public:
  EmptyBlob() {}

  int64 Read(uint8 *destination, int64 offset, int64 max_bytes) const {
    if (!destination || (offset < 0) || (max_bytes < 0))
      return -1;
    return 0;
  }

  int64 Length() const {
    return 0;
  }

 private:
  DISALLOW_EVIL_CONSTRUCTORS(EmptyBlob);
};

#endif  // not OFFICIAL_BUILD

#endif  // GEARS_BLOB_BLOB_INTERFACE_H__