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30 
31 // Author: kenton@google.com (Kenton Varda)
32 //  Based on original Protocol Buffers design by
33 //  Sanjay Ghemawat, Jeff Dean, and others.
34 //
35 // This file contains common implementations of the interfaces defined in
36 // zero_copy_stream.h which are only included in the full (non-lite)
37 // protobuf library.  These implementations include Unix file descriptors
38 // and C++ iostreams.  See also:  zero_copy_stream_impl_lite.h
39 
40 #ifndef GOOGLE_PROTOBUF_IO_ZERO_COPY_STREAM_IMPL_H__
41 #define GOOGLE_PROTOBUF_IO_ZERO_COPY_STREAM_IMPL_H__
42 
43 #include <string>
44 #include <iosfwd>
45 #include <google/protobuf/io/zero_copy_stream.h>
46 #include <google/protobuf/io/zero_copy_stream_impl_lite.h>
47 #include <google/protobuf/stubs/common.h>
48 
49 
50 namespace google {
51 namespace protobuf {
52 namespace io {
53 
54 
55 // ===================================================================
56 
57 // A ZeroCopyInputStream which reads from a file descriptor.
58 //
59 // FileInputStream is preferred over using an ifstream with IstreamInputStream.
60 // The latter will introduce an extra layer of buffering, harming performance.
61 // Also, it's conceivable that FileInputStream could someday be enhanced
62 // to use zero-copy file descriptors on OSs which support them.
63 class LIBPROTOBUF_EXPORT FileInputStream : public ZeroCopyInputStream {
64  public:
65   // Creates a stream that reads from the given Unix file descriptor.
66   // If a block_size is given, it specifies the number of bytes that
67   // should be read and returned with each call to Next().  Otherwise,
68   // a reasonable default is used.
69   explicit FileInputStream(int file_descriptor, int block_size = -1);
70   ~FileInputStream();
71 
72   // Flushes any buffers and closes the underlying file.  Returns false if
73   // an error occurs during the process; use GetErrno() to examine the error.
74   // Even if an error occurs, the file descriptor is closed when this returns.
75   bool Close();
76 
77   // By default, the file descriptor is not closed when the stream is
78   // destroyed.  Call SetCloseOnDelete(true) to change that.  WARNING:
79   // This leaves no way for the caller to detect if close() fails.  If
80   // detecting close() errors is important to you, you should arrange
81   // to close the descriptor yourself.
SetCloseOnDelete(bool value)82   void SetCloseOnDelete(bool value) { copying_input_.SetCloseOnDelete(value); }
83 
84   // If an I/O error has occurred on this file descriptor, this is the
85   // errno from that error.  Otherwise, this is zero.  Once an error
86   // occurs, the stream is broken and all subsequent operations will
87   // fail.
GetErrno()88   int GetErrno() { return copying_input_.GetErrno(); }
89 
90   // implements ZeroCopyInputStream ----------------------------------
91   bool Next(const void** data, int* size);
92   void BackUp(int count);
93   bool Skip(int count);
94   int64 ByteCount() const;
95 
96  private:
97   class LIBPROTOBUF_EXPORT CopyingFileInputStream : public CopyingInputStream {
98    public:
99     CopyingFileInputStream(int file_descriptor);
100     ~CopyingFileInputStream();
101 
102     bool Close();
SetCloseOnDelete(bool value)103     void SetCloseOnDelete(bool value) { close_on_delete_ = value; }
GetErrno()104     int GetErrno() { return errno_; }
105 
106     // implements CopyingInputStream ---------------------------------
107     int Read(void* buffer, int size);
108     int Skip(int count);
109 
110    private:
111     // The file descriptor.
112     const int file_;
113     bool close_on_delete_;
114     bool is_closed_;
115 
116     // The errno of the I/O error, if one has occurred.  Otherwise, zero.
117     int errno_;
118 
119     // Did we try to seek once and fail?  If so, we assume this file descriptor
120     // doesn't support seeking and won't try again.
121     bool previous_seek_failed_;
122 
123     GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(CopyingFileInputStream);
124   };
125 
126   CopyingFileInputStream copying_input_;
127   CopyingInputStreamAdaptor impl_;
128 
129   GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(FileInputStream);
130 };
131 
132 // ===================================================================
133 
134 // A ZeroCopyOutputStream which writes to a file descriptor.
135 //
136 // FileOutputStream is preferred over using an ofstream with
137 // OstreamOutputStream.  The latter will introduce an extra layer of buffering,
138 // harming performance.  Also, it's conceivable that FileOutputStream could
139 // someday be enhanced to use zero-copy file descriptors on OSs which
140 // support them.
141 class LIBPROTOBUF_EXPORT FileOutputStream : public ZeroCopyOutputStream {
142  public:
143   // Creates a stream that writes to the given Unix file descriptor.
144   // If a block_size is given, it specifies the size of the buffers
145   // that should be returned by Next().  Otherwise, a reasonable default
146   // is used.
147   explicit FileOutputStream(int file_descriptor, int block_size = -1);
148   ~FileOutputStream();
149 
150   // Flushes any buffers and closes the underlying file.  Returns false if
151   // an error occurs during the process; use GetErrno() to examine the error.
152   // Even if an error occurs, the file descriptor is closed when this returns.
153   bool Close();
154 
155   // Flushes FileOutputStream's buffers but does not close the
156   // underlying file. No special measures are taken to ensure that
157   // underlying operating system file object is synchronized to disk.
158   bool Flush();
159 
160   // By default, the file descriptor is not closed when the stream is
161   // destroyed.  Call SetCloseOnDelete(true) to change that.  WARNING:
162   // This leaves no way for the caller to detect if close() fails.  If
163   // detecting close() errors is important to you, you should arrange
164   // to close the descriptor yourself.
SetCloseOnDelete(bool value)165   void SetCloseOnDelete(bool value) { copying_output_.SetCloseOnDelete(value); }
166 
167   // If an I/O error has occurred on this file descriptor, this is the
168   // errno from that error.  Otherwise, this is zero.  Once an error
169   // occurs, the stream is broken and all subsequent operations will
170   // fail.
GetErrno()171   int GetErrno() { return copying_output_.GetErrno(); }
172 
173   // implements ZeroCopyOutputStream ---------------------------------
174   bool Next(void** data, int* size);
175   void BackUp(int count);
176   int64 ByteCount() const;
177 
178  private:
179   class LIBPROTOBUF_EXPORT CopyingFileOutputStream : public CopyingOutputStream {
180    public:
181     CopyingFileOutputStream(int file_descriptor);
182     ~CopyingFileOutputStream();
183 
184     bool Close();
SetCloseOnDelete(bool value)185     void SetCloseOnDelete(bool value) { close_on_delete_ = value; }
GetErrno()186     int GetErrno() { return errno_; }
187 
188     // implements CopyingOutputStream --------------------------------
189     bool Write(const void* buffer, int size);
190 
191    private:
192     // The file descriptor.
193     const int file_;
194     bool close_on_delete_;
195     bool is_closed_;
196 
197     // The errno of the I/O error, if one has occurred.  Otherwise, zero.
198     int errno_;
199 
200     GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(CopyingFileOutputStream);
201   };
202 
203   CopyingFileOutputStream copying_output_;
204   CopyingOutputStreamAdaptor impl_;
205 
206   GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(FileOutputStream);
207 };
208 
209 // ===================================================================
210 
211 // A ZeroCopyInputStream which reads from a C++ istream.
212 //
213 // Note that for reading files (or anything represented by a file descriptor),
214 // FileInputStream is more efficient.
215 class LIBPROTOBUF_EXPORT IstreamInputStream : public ZeroCopyInputStream {
216  public:
217   // Creates a stream that reads from the given C++ istream.
218   // If a block_size is given, it specifies the number of bytes that
219   // should be read and returned with each call to Next().  Otherwise,
220   // a reasonable default is used.
221   explicit IstreamInputStream(istream* stream, int block_size = -1);
222   ~IstreamInputStream();
223 
224   // implements ZeroCopyInputStream ----------------------------------
225   bool Next(const void** data, int* size);
226   void BackUp(int count);
227   bool Skip(int count);
228   int64 ByteCount() const;
229 
230  private:
231   class LIBPROTOBUF_EXPORT CopyingIstreamInputStream : public CopyingInputStream {
232    public:
233     CopyingIstreamInputStream(istream* input);
234     ~CopyingIstreamInputStream();
235 
236     // implements CopyingInputStream ---------------------------------
237     int Read(void* buffer, int size);
238     // (We use the default implementation of Skip().)
239 
240    private:
241     // The stream.
242     istream* input_;
243 
244     GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(CopyingIstreamInputStream);
245   };
246 
247   CopyingIstreamInputStream copying_input_;
248   CopyingInputStreamAdaptor impl_;
249 
250   GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(IstreamInputStream);
251 };
252 
253 // ===================================================================
254 
255 // A ZeroCopyOutputStream which writes to a C++ ostream.
256 //
257 // Note that for writing files (or anything represented by a file descriptor),
258 // FileOutputStream is more efficient.
259 class LIBPROTOBUF_EXPORT OstreamOutputStream : public ZeroCopyOutputStream {
260  public:
261   // Creates a stream that writes to the given C++ ostream.
262   // If a block_size is given, it specifies the size of the buffers
263   // that should be returned by Next().  Otherwise, a reasonable default
264   // is used.
265   explicit OstreamOutputStream(ostream* stream, int block_size = -1);
266   ~OstreamOutputStream();
267 
268   // implements ZeroCopyOutputStream ---------------------------------
269   bool Next(void** data, int* size);
270   void BackUp(int count);
271   int64 ByteCount() const;
272 
273  private:
274   class LIBPROTOBUF_EXPORT CopyingOstreamOutputStream : public CopyingOutputStream {
275    public:
276     CopyingOstreamOutputStream(ostream* output);
277     ~CopyingOstreamOutputStream();
278 
279     // implements CopyingOutputStream --------------------------------
280     bool Write(const void* buffer, int size);
281 
282    private:
283     // The stream.
284     ostream* output_;
285 
286     GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(CopyingOstreamOutputStream);
287   };
288 
289   CopyingOstreamOutputStream copying_output_;
290   CopyingOutputStreamAdaptor impl_;
291 
292   GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(OstreamOutputStream);
293 };
294 
295 // ===================================================================
296 
297 // A ZeroCopyInputStream which reads from several other streams in sequence.
298 // ConcatenatingInputStream is unable to distinguish between end-of-stream
299 // and read errors in the underlying streams, so it assumes any errors mean
300 // end-of-stream.  So, if the underlying streams fail for any other reason,
301 // ConcatenatingInputStream may do odd things.  It is suggested that you do
302 // not use ConcatenatingInputStream on streams that might produce read errors
303 // other than end-of-stream.
304 class LIBPROTOBUF_EXPORT ConcatenatingInputStream : public ZeroCopyInputStream {
305  public:
306   // All streams passed in as well as the array itself must remain valid
307   // until the ConcatenatingInputStream is destroyed.
308   ConcatenatingInputStream(ZeroCopyInputStream* const streams[], int count);
309   ~ConcatenatingInputStream();
310 
311   // implements ZeroCopyInputStream ----------------------------------
312   bool Next(const void** data, int* size);
313   void BackUp(int count);
314   bool Skip(int count);
315   int64 ByteCount() const;
316 
317 
318  private:
319   // As streams are retired, streams_ is incremented and count_ is
320   // decremented.
321   ZeroCopyInputStream* const* streams_;
322   int stream_count_;
323   int64 bytes_retired_;  // Bytes read from previous streams.
324 
325   GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(ConcatenatingInputStream);
326 };
327 
328 // ===================================================================
329 
330 // A ZeroCopyInputStream which wraps some other stream and limits it to
331 // a particular byte count.
332 class LIBPROTOBUF_EXPORT LimitingInputStream : public ZeroCopyInputStream {
333  public:
334   LimitingInputStream(ZeroCopyInputStream* input, int64 limit);
335   ~LimitingInputStream();
336 
337   // implements ZeroCopyInputStream ----------------------------------
338   bool Next(const void** data, int* size);
339   void BackUp(int count);
340   bool Skip(int count);
341   int64 ByteCount() const;
342 
343 
344  private:
345   ZeroCopyInputStream* input_;
346   int64 limit_;  // Decreases as we go, becomes negative if we overshoot.
347   int64 prior_bytes_read_;  // Bytes read on underlying stream at construction
348 
349   GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(LimitingInputStream);
350 };
351 
352 // ===================================================================
353 
354 }  // namespace io
355 }  // namespace protobuf
356 
357 }  // namespace google
358 #endif  // GOOGLE_PROTOBUF_IO_ZERO_COPY_STREAM_IMPL_H__
359