1// Protocol Buffers - Google's data interchange format
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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
44#include <iosfwd>
45#include <string>
46
47#include <google/protobuf/stubs/common.h>
48#include <google/protobuf/io/zero_copy_stream.h>
49#include <google/protobuf/io/zero_copy_stream_impl_lite.h>
50
51// Must be included last.
52#include <google/protobuf/port_def.inc>
53
54namespace google {
55namespace protobuf {
56namespace io {
57
58// ===================================================================
59
60// A ZeroCopyInputStream which reads from a file descriptor.
61//
62// FileInputStream is preferred over using an ifstream with IstreamInputStream.
63// The latter will introduce an extra layer of buffering, harming performance.
64// Also, it's conceivable that FileInputStream could someday be enhanced
65// to use zero-copy file descriptors on OSs which support them.
66class PROTOBUF_EXPORT FileInputStream PROTOBUF_FUTURE_FINAL
67 : public ZeroCopyInputStream {
68 public:
69 // Creates a stream that reads from the given Unix file descriptor.
70 // If a block_size is given, it specifies the number of bytes that
71 // should be read and returned with each call to Next(). Otherwise,
72 // a reasonable default is used.
73 explicit FileInputStream(int file_descriptor, int block_size = -1);
74
75 // Flushes any buffers and closes the underlying file. Returns false if
76 // an error occurs during the process; use GetErrno() to examine the error.
77 // Even if an error occurs, the file descriptor is closed when this returns.
78 bool Close();
79
80 // By default, the file descriptor is not closed when the stream is
81 // destroyed. Call SetCloseOnDelete(true) to change that. WARNING:
82 // This leaves no way for the caller to detect if close() fails. If
83 // detecting close() errors is important to you, you should arrange
84 // to close the descriptor yourself.
85 void SetCloseOnDelete(bool value) { copying_input_.SetCloseOnDelete(value); }
86
87 // If an I/O error has occurred on this file descriptor, this is the
88 // errno from that error. Otherwise, this is zero. Once an error
89 // occurs, the stream is broken and all subsequent operations will
90 // fail.
91 int GetErrno() const { return copying_input_.GetErrno(); }
92
93 // implements ZeroCopyInputStream ----------------------------------
94 bool Next(const void** data, int* size) override;
95 void BackUp(int count) override;
96 bool Skip(int count) override;
97 int64_t ByteCount() const override;
98
99 private:
100 class PROTOBUF_EXPORT CopyingFileInputStream PROTOBUF_FUTURE_FINAL
101 : public CopyingInputStream {
102 public:
103 CopyingFileInputStream(int file_descriptor);
104 ~CopyingFileInputStream() override;
105
106 bool Close();
107 void SetCloseOnDelete(bool value) { close_on_delete_ = value; }
108 int GetErrno() const { return errno_; }
109
110 // implements CopyingInputStream ---------------------------------
111 int Read(void* buffer, int size) override;
112 int Skip(int count) override;
113
114 private:
115 // The file descriptor.
116 const int file_;
117 bool close_on_delete_;
118 bool is_closed_;
119
120 // The errno of the I/O error, if one has occurred. Otherwise, zero.
121 int errno_;
122
123 // Did we try to seek once and fail? If so, we assume this file descriptor
124 // doesn't support seeking and won't try again.
125 bool previous_seek_failed_;
126
127 GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(CopyingFileInputStream);
128 };
129
130 CopyingFileInputStream copying_input_;
131 CopyingInputStreamAdaptor impl_;
132
133 GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(FileInputStream);
134};
135
136// ===================================================================
137
138// A ZeroCopyOutputStream which writes to a file descriptor.
139//
140// FileOutputStream is preferred over using an ofstream with
141// OstreamOutputStream. The latter will introduce an extra layer of buffering,
142// harming performance. Also, it's conceivable that FileOutputStream could
143// someday be enhanced to use zero-copy file descriptors on OSs which
144// support them.
145class PROTOBUF_EXPORT FileOutputStream PROTOBUF_FUTURE_FINAL
146 : public CopyingOutputStreamAdaptor {
147 public:
148 // Creates a stream that writes to the given Unix file descriptor.
149 // If a block_size is given, it specifies the size of the buffers
150 // that should be returned by Next(). Otherwise, a reasonable default
151 // is used.
152 explicit FileOutputStream(int file_descriptor, int block_size = -1);
153
154 ~FileOutputStream() override;
155
156 // Flushes any buffers and closes the underlying file. Returns false if
157 // an error occurs during the process; use GetErrno() to examine the error.
158 // Even if an error occurs, the file descriptor is closed when this returns.
159 bool Close();
160
161 // By default, the file descriptor is not closed when the stream is
162 // destroyed. Call SetCloseOnDelete(true) to change that. WARNING:
163 // This leaves no way for the caller to detect if close() fails. If
164 // detecting close() errors is important to you, you should arrange
165 // to close the descriptor yourself.
166 void SetCloseOnDelete(bool value) { copying_output_.SetCloseOnDelete(value); }
167
168 // If an I/O error has occurred on this file descriptor, this is the
169 // errno from that error. Otherwise, this is zero. Once an error
170 // occurs, the stream is broken and all subsequent operations will
171 // fail.
172 int GetErrno() const { return copying_output_.GetErrno(); }
173
174 private:
175 class PROTOBUF_EXPORT CopyingFileOutputStream PROTOBUF_FUTURE_FINAL
176 : public CopyingOutputStream {
177 public:
178 CopyingFileOutputStream(int file_descriptor);
179 ~CopyingFileOutputStream() override;
180
181 bool Close();
182 void SetCloseOnDelete(bool value) { close_on_delete_ = value; }
183 int GetErrno() const { return errno_; }
184
185 // implements CopyingOutputStream --------------------------------
186 bool Write(const void* buffer, int size) override;
187
188 private:
189 // The file descriptor.
190 const int file_;
191 bool close_on_delete_;
192 bool is_closed_;
193
194 // The errno of the I/O error, if one has occurred. Otherwise, zero.
195 int errno_;
196
197 GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(CopyingFileOutputStream);
198 };
199
200 CopyingFileOutputStream copying_output_;
201
202 GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(FileOutputStream);
203};
204
205// ===================================================================
206
207// A ZeroCopyInputStream which reads from a C++ istream.
208//
209// Note that for reading files (or anything represented by a file descriptor),
210// FileInputStream is more efficient.
211class PROTOBUF_EXPORT IstreamInputStream PROTOBUF_FUTURE_FINAL
212 : public ZeroCopyInputStream {
213 public:
214 // Creates a stream that reads from the given C++ istream.
215 // If a block_size is given, it specifies the number of bytes that
216 // should be read and returned with each call to Next(). Otherwise,
217 // a reasonable default is used.
218 explicit IstreamInputStream(std::istream* stream, int block_size = -1);
219
220 // implements ZeroCopyInputStream ----------------------------------
221 bool Next(const void** data, int* size) override;
222 void BackUp(int count) override;
223 bool Skip(int count) override;
224 int64_t ByteCount() const override;
225
226 private:
227 class PROTOBUF_EXPORT CopyingIstreamInputStream PROTOBUF_FUTURE_FINAL
228 : public CopyingInputStream {
229 public:
230 CopyingIstreamInputStream(std::istream* input);
231 ~CopyingIstreamInputStream() override;
232
233 // implements CopyingInputStream ---------------------------------
234 int Read(void* buffer, int size) override;
235 // (We use the default implementation of Skip().)
236
237 private:
238 // The stream.
239 std::istream* input_;
240
241 GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(CopyingIstreamInputStream);
242 };
243
244 CopyingIstreamInputStream copying_input_;
245 CopyingInputStreamAdaptor impl_;
246
247 GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(IstreamInputStream);
248};
249
250// ===================================================================
251
252// A ZeroCopyOutputStream which writes to a C++ ostream.
253//
254// Note that for writing files (or anything represented by a file descriptor),
255// FileOutputStream is more efficient.
256class PROTOBUF_EXPORT OstreamOutputStream PROTOBUF_FUTURE_FINAL
257 : public ZeroCopyOutputStream {
258 public:
259 // Creates a stream that writes to the given C++ ostream.
260 // If a block_size is given, it specifies the size of the buffers
261 // that should be returned by Next(). Otherwise, a reasonable default
262 // is used.
263 explicit OstreamOutputStream(std::ostream* stream, int block_size = -1);
264 ~OstreamOutputStream() override;
265
266 // implements ZeroCopyOutputStream ---------------------------------
267 bool Next(void** data, int* size) override;
268 void BackUp(int count) override;
269 int64_t ByteCount() const override;
270
271 private:
272 class PROTOBUF_EXPORT CopyingOstreamOutputStream PROTOBUF_FUTURE_FINAL
273 : public CopyingOutputStream {
274 public:
275 CopyingOstreamOutputStream(std::ostream* output);
276 ~CopyingOstreamOutputStream() override;
277
278 // implements CopyingOutputStream --------------------------------
279 bool Write(const void* buffer, int size) override;
280
281 private:
282 // The stream.
283 std::ostream* output_;
284
285 GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(CopyingOstreamOutputStream);
286 };
287
288 CopyingOstreamOutputStream copying_output_;
289 CopyingOutputStreamAdaptor impl_;
290
291 GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(OstreamOutputStream);
292};
293
294// ===================================================================
295
296// A ZeroCopyInputStream which reads from several other streams in sequence.
297// ConcatenatingInputStream is unable to distinguish between end-of-stream
298// and read errors in the underlying streams, so it assumes any errors mean
299// end-of-stream. So, if the underlying streams fail for any other reason,
300// ConcatenatingInputStream may do odd things. It is suggested that you do
301// not use ConcatenatingInputStream on streams that might produce read errors
302// other than end-of-stream.
303class PROTOBUF_EXPORT ConcatenatingInputStream PROTOBUF_FUTURE_FINAL
304 : 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() override = default;
310
311 // implements ZeroCopyInputStream ----------------------------------
312 bool Next(const void** data, int* size) override;
313 void BackUp(int count) override;
314 bool Skip(int count) override;
315 int64_t ByteCount() const override;
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_t bytes_retired_; // Bytes read from previous streams.
324
325 GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(ConcatenatingInputStream);
326};
327
328// ===================================================================
329
330} // namespace io
331} // namespace protobuf
332} // namespace google
333
334#include <google/protobuf/port_undef.inc>
335
336#endif // GOOGLE_PROTOBUF_IO_ZERO_COPY_STREAM_IMPL_H__
337