poppler/CachedFile.h

//========================================================================
//
// CachedFile.h
//
// Caching files support.
//
// This file is licensed under the GPLv2 or later
//
// Copyright 2009 Stefan Thomas <thomas@eload24.com>
// Copyright 2010 Hib Eris <hib@hiberis.nl>
// Copyright 2010, 2018 Albert Astals Cid <aacid@kde.org>
//
//========================================================================

#ifndef CACHEDFILE_H
#define CACHEDFILE_H

#include "poppler-config.h"

#include "Object.h"
#include "Stream.h"

#include <vector>

//------------------------------------------------------------------------

#define CachedFileChunkSize 8192 // This should be a multiple of cachedStreamBufSize

class GooString;
class CachedFileLoader;

//------------------------------------------------------------------------
// CachedFile
//
// CachedFile gives FILE-like access to a document at a specified URI.
// In the constructor, you specify a CachedFileLoader that handles loading
// the data from the document. The CachedFile requests no more data then it
// needs from the CachedFileLoader.
//------------------------------------------------------------------------

class CachedFile {

friend class CachedFileWriter;

public:

  CachedFile(CachedFileLoader *cacheLoader, GooString *uri);

  CachedFile(const CachedFile &) = delete;
  CachedFile& operator=(const CachedFile &) = delete;

  unsigned int getLength() { return length; }
  long int tell();
  int seek(long int offset, int origin);
  size_t read(void * ptr, size_t unitsize, size_t count);
  size_t write(const char *ptr, size_t size, size_t fromByte);
  int cache(const std::vector<ByteRange> &ranges);

  // Reference counting.
  void incRefCnt();
  void decRefCnt();

private:

  ~CachedFile();

  enum ChunkState {
    chunkStateNew = 0,
    chunkStateLoaded
  };

  typedef struct {
    ChunkState state;
    char data[CachedFileChunkSize];
  } Chunk;

  int cache(size_t offset, size_t length);

  CachedFileLoader *loader;
  GooString *uri;

  size_t length;
  size_t streamPos;

  std::vector<Chunk> *chunks;

  int refCnt;  // reference count

};

//------------------------------------------------------------------------
// CachedFileWriter
//
// CachedFileWriter handles sequential writes to a CachedFile.
// On construction, you specify the CachedFile and the chunks of it to which data
// should be written.
//------------------------------------------------------------------------

class CachedFileWriter {

public:

  // Construct a CachedFile Writer.
  // The caller is responsible for deleting the cachedFile and chunksA.
  CachedFileWriter(CachedFile *cachedFile, std::vector<int> *chunksA);

  ~CachedFileWriter();

  // Writes size bytes from ptr to cachedFile, returns number of bytes written.
  size_t write(const char *ptr, size_t size);

private:

  CachedFile *cachedFile;
  std::vector<int> *chunks;
  std::vector<int>::iterator it;
  size_t offset;

};

//------------------------------------------------------------------------
// CachedFileLoader
//
// CachedFileLoader is an abstact class that specifies the interface for
// loadng data from an URI into a CachedFile.
//------------------------------------------------------------------------

class CachedFileLoader {

public:

  CachedFileLoader() = default;
  virtual ~CachedFileLoader() {};

  CachedFileLoader(const CachedFileLoader &) = delete;
  CachedFileLoader& operator=(const CachedFileLoader &) = delete;

  // Initializes the file load.
  // Returns the length of the file.
  // The caller is responsible for deleting uri and cachedFile.
  virtual size_t init(GooString *uri, CachedFile *cachedFile) = 0;

  // Loads specified byte ranges and passes it to the writer to store them.
  // Returns 0 on success, Anything but 0 on failure.
  // The caller is responsible for deleting the writer.
  virtual int load(const std::vector<ByteRange> &ranges, CachedFileWriter *writer) = 0;

};

//------------------------------------------------------------------------

#endif