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1 /*
2  * A C++ I/O streams interface to the zlib gz* functions
3  *
4  * by Ludwig Schwardt <schwardt@sun.ac.za>
5  * original version by Kevin Ruland <kevin@rodin.wustl.edu>
6  *
7  * This version is standard-compliant and compatible with gcc 3.x.
8  */
9 
10 #include "zfstream.h"
11 #include <cstring>          // for strcpy, strcat, strlen (mode strings)
12 #include <cstdio>           // for BUFSIZ
13 
14 // Internal buffer sizes (default and "unbuffered" versions)
15 #define BIGBUFSIZE BUFSIZ
16 #define SMALLBUFSIZE 1
17 
18 /*****************************************************************************/
19 
20 // Default constructor
gzfilebuf()21 gzfilebuf::gzfilebuf()
22 : file(NULL), io_mode(std::ios_base::openmode(0)), own_fd(false),
23   buffer(NULL), buffer_size(BIGBUFSIZE), own_buffer(true)
24 {
25   // No buffers to start with
26   this->disable_buffer();
27 }
28 
29 // Destructor
~gzfilebuf()30 gzfilebuf::~gzfilebuf()
31 {
32   // Sync output buffer and close only if responsible for file
33   // (i.e. attached streams should be left open at this stage)
34   this->sync();
35   if (own_fd)
36     this->close();
37   // Make sure internal buffer is deallocated
38   this->disable_buffer();
39 }
40 
41 // Set compression level and strategy
42 int
setcompression(int comp_level,int comp_strategy)43 gzfilebuf::setcompression(int comp_level,
44                           int comp_strategy)
45 {
46   return gzsetparams(file, comp_level, comp_strategy);
47 }
48 
49 // Open gzipped file
50 gzfilebuf*
open(const char * name,std::ios_base::openmode mode)51 gzfilebuf::open(const char *name,
52                 std::ios_base::openmode mode)
53 {
54   // Fail if file already open
55   if (this->is_open())
56     return NULL;
57   // Don't support simultaneous read/write access (yet)
58   if ((mode & std::ios_base::in) && (mode & std::ios_base::out))
59     return NULL;
60 
61   // Build mode string for gzopen and check it [27.8.1.3.2]
62   char char_mode[6] = "\0\0\0\0\0";
63   if (!this->open_mode(mode, char_mode))
64     return NULL;
65 
66   // Attempt to open file
67   if ((file = gzopen(name, char_mode)) == NULL)
68     return NULL;
69 
70   // On success, allocate internal buffer and set flags
71   this->enable_buffer();
72   io_mode = mode;
73   own_fd = true;
74   return this;
75 }
76 
77 // Attach to gzipped file
78 gzfilebuf*
attach(int fd,std::ios_base::openmode mode)79 gzfilebuf::attach(int fd,
80                   std::ios_base::openmode mode)
81 {
82   // Fail if file already open
83   if (this->is_open())
84     return NULL;
85   // Don't support simultaneous read/write access (yet)
86   if ((mode & std::ios_base::in) && (mode & std::ios_base::out))
87     return NULL;
88 
89   // Build mode string for gzdopen and check it [27.8.1.3.2]
90   char char_mode[6] = "\0\0\0\0\0";
91   if (!this->open_mode(mode, char_mode))
92     return NULL;
93 
94   // Attempt to attach to file
95   if ((file = gzdopen(fd, char_mode)) == NULL)
96     return NULL;
97 
98   // On success, allocate internal buffer and set flags
99   this->enable_buffer();
100   io_mode = mode;
101   own_fd = false;
102   return this;
103 }
104 
105 // Close gzipped file
106 gzfilebuf*
close()107 gzfilebuf::close()
108 {
109   // Fail immediately if no file is open
110   if (!this->is_open())
111     return NULL;
112   // Assume success
113   gzfilebuf* retval = this;
114   // Attempt to sync and close gzipped file
115   if (this->sync() == -1)
116     retval = NULL;
117   if (gzclose(file) < 0)
118     retval = NULL;
119   // File is now gone anyway (postcondition [27.8.1.3.8])
120   file = NULL;
121   own_fd = false;
122   // Destroy internal buffer if it exists
123   this->disable_buffer();
124   return retval;
125 }
126 
127 /* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
128 
129 // Convert int open mode to mode string
130 bool
open_mode(std::ios_base::openmode mode,char * c_mode) const131 gzfilebuf::open_mode(std::ios_base::openmode mode,
132                      char* c_mode) const
133 {
134   bool testb = mode & std::ios_base::binary;
135   bool testi = mode & std::ios_base::in;
136   bool testo = mode & std::ios_base::out;
137   bool testt = mode & std::ios_base::trunc;
138   bool testa = mode & std::ios_base::app;
139 
140   // Check for valid flag combinations - see [27.8.1.3.2] (Table 92)
141   // Original zfstream hardcoded the compression level to maximum here...
142   // Double the time for less than 1% size improvement seems
143   // excessive though - keeping it at the default level
144   // To change back, just append "9" to the next three mode strings
145   if (!testi && testo && !testt && !testa)
146     strcpy(c_mode, "w");
147   if (!testi && testo && !testt && testa)
148     strcpy(c_mode, "a");
149   if (!testi && testo && testt && !testa)
150     strcpy(c_mode, "w");
151   if (testi && !testo && !testt && !testa)
152     strcpy(c_mode, "r");
153   // No read/write mode yet
154 //  if (testi && testo && !testt && !testa)
155 //    strcpy(c_mode, "r+");
156 //  if (testi && testo && testt && !testa)
157 //    strcpy(c_mode, "w+");
158 
159   // Mode string should be empty for invalid combination of flags
160   if (strlen(c_mode) == 0)
161     return false;
162   if (testb)
163     strcat(c_mode, "b");
164   return true;
165 }
166 
167 // Determine number of characters in internal get buffer
168 std::streamsize
showmanyc()169 gzfilebuf::showmanyc()
170 {
171   // Calls to underflow will fail if file not opened for reading
172   if (!this->is_open() || !(io_mode & std::ios_base::in))
173     return -1;
174   // Make sure get area is in use
175   if (this->gptr() && (this->gptr() < this->egptr()))
176     return std::streamsize(this->egptr() - this->gptr());
177   else
178     return 0;
179 }
180 
181 // Fill get area from gzipped file
182 gzfilebuf::int_type
underflow()183 gzfilebuf::underflow()
184 {
185   // If something is left in the get area by chance, return it
186   // (this shouldn't normally happen, as underflow is only supposed
187   // to be called when gptr >= egptr, but it serves as error check)
188   if (this->gptr() && (this->gptr() < this->egptr()))
189     return traits_type::to_int_type(*(this->gptr()));
190 
191   // If the file hasn't been opened for reading, produce error
192   if (!this->is_open() || !(io_mode & std::ios_base::in))
193     return traits_type::eof();
194 
195   // Attempt to fill internal buffer from gzipped file
196   // (buffer must be guaranteed to exist...)
197   int bytes_read = gzread(file, buffer, buffer_size);
198   // Indicates error or EOF
199   if (bytes_read <= 0)
200   {
201     // Reset get area
202     this->setg(buffer, buffer, buffer);
203     return traits_type::eof();
204   }
205   // Make all bytes read from file available as get area
206   this->setg(buffer, buffer, buffer + bytes_read);
207 
208   // Return next character in get area
209   return traits_type::to_int_type(*(this->gptr()));
210 }
211 
212 // Write put area to gzipped file
213 gzfilebuf::int_type
overflow(int_type c)214 gzfilebuf::overflow(int_type c)
215 {
216   // Determine whether put area is in use
217   if (this->pbase())
218   {
219     // Double-check pointer range
220     if (this->pptr() > this->epptr() || this->pptr() < this->pbase())
221       return traits_type::eof();
222     // Add extra character to buffer if not EOF
223     if (!traits_type::eq_int_type(c, traits_type::eof()))
224     {
225       *(this->pptr()) = traits_type::to_char_type(c);
226       this->pbump(1);
227     }
228     // Number of characters to write to file
229     int bytes_to_write = this->pptr() - this->pbase();
230     // Overflow doesn't fail if nothing is to be written
231     if (bytes_to_write > 0)
232     {
233       // If the file hasn't been opened for writing, produce error
234       if (!this->is_open() || !(io_mode & std::ios_base::out))
235         return traits_type::eof();
236       // If gzipped file won't accept all bytes written to it, fail
237       if (gzwrite(file, this->pbase(), bytes_to_write) != bytes_to_write)
238         return traits_type::eof();
239       // Reset next pointer to point to pbase on success
240       this->pbump(-bytes_to_write);
241     }
242   }
243   // Write extra character to file if not EOF
244   else if (!traits_type::eq_int_type(c, traits_type::eof()))
245   {
246     // If the file hasn't been opened for writing, produce error
247     if (!this->is_open() || !(io_mode & std::ios_base::out))
248       return traits_type::eof();
249     // Impromptu char buffer (allows "unbuffered" output)
250     char_type last_char = traits_type::to_char_type(c);
251     // If gzipped file won't accept this character, fail
252     if (gzwrite(file, &last_char, 1) != 1)
253       return traits_type::eof();
254   }
255 
256   // If you got here, you have succeeded (even if c was EOF)
257   // The return value should therefore be non-EOF
258   if (traits_type::eq_int_type(c, traits_type::eof()))
259     return traits_type::not_eof(c);
260   else
261     return c;
262 }
263 
264 // Assign new buffer
265 std::streambuf*
setbuf(char_type * p,std::streamsize n)266 gzfilebuf::setbuf(char_type* p,
267                   std::streamsize n)
268 {
269   // First make sure stuff is sync'ed, for safety
270   if (this->sync() == -1)
271     return NULL;
272   // If buffering is turned off on purpose via setbuf(0,0), still allocate one...
273   // "Unbuffered" only really refers to put [27.8.1.4.10], while get needs at
274   // least a buffer of size 1 (very inefficient though, therefore make it bigger?)
275   // This follows from [27.5.2.4.3]/12 (gptr needs to point at something, it seems)
276   if (!p || !n)
277   {
278     // Replace existing buffer (if any) with small internal buffer
279     this->disable_buffer();
280     buffer = NULL;
281     buffer_size = 0;
282     own_buffer = true;
283     this->enable_buffer();
284   }
285   else
286   {
287     // Replace existing buffer (if any) with external buffer
288     this->disable_buffer();
289     buffer = p;
290     buffer_size = n;
291     own_buffer = false;
292     this->enable_buffer();
293   }
294   return this;
295 }
296 
297 // Write put area to gzipped file (i.e. ensures that put area is empty)
298 int
sync()299 gzfilebuf::sync()
300 {
301   return traits_type::eq_int_type(this->overflow(), traits_type::eof()) ? -1 : 0;
302 }
303 
304 /* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
305 
306 // Allocate internal buffer
307 void
enable_buffer()308 gzfilebuf::enable_buffer()
309 {
310   // If internal buffer required, allocate one
311   if (own_buffer && !buffer)
312   {
313     // Check for buffered vs. "unbuffered"
314     if (buffer_size > 0)
315     {
316       // Allocate internal buffer
317       buffer = new char_type[buffer_size];
318       // Get area starts empty and will be expanded by underflow as need arises
319       this->setg(buffer, buffer, buffer);
320       // Setup entire internal buffer as put area.
321       // The one-past-end pointer actually points to the last element of the buffer,
322       // so that overflow(c) can safely add the extra character c to the sequence.
323       // These pointers remain in place for the duration of the buffer
324       this->setp(buffer, buffer + buffer_size - 1);
325     }
326     else
327     {
328       // Even in "unbuffered" case, (small?) get buffer is still required
329       buffer_size = SMALLBUFSIZE;
330       buffer = new char_type[buffer_size];
331       this->setg(buffer, buffer, buffer);
332       // "Unbuffered" means no put buffer
333       this->setp(0, 0);
334     }
335   }
336   else
337   {
338     // If buffer already allocated, reset buffer pointers just to make sure no
339     // stale chars are lying around
340     this->setg(buffer, buffer, buffer);
341     this->setp(buffer, buffer + buffer_size - 1);
342   }
343 }
344 
345 // Destroy internal buffer
346 void
disable_buffer()347 gzfilebuf::disable_buffer()
348 {
349   // If internal buffer exists, deallocate it
350   if (own_buffer && buffer)
351   {
352     // Preserve unbuffered status by zeroing size
353     if (!this->pbase())
354       buffer_size = 0;
355     delete[] buffer;
356     buffer = NULL;
357     this->setg(0, 0, 0);
358     this->setp(0, 0);
359   }
360   else
361   {
362     // Reset buffer pointers to initial state if external buffer exists
363     this->setg(buffer, buffer, buffer);
364     if (buffer)
365       this->setp(buffer, buffer + buffer_size - 1);
366     else
367       this->setp(0, 0);
368   }
369 }
370 
371 /*****************************************************************************/
372 
373 // Default constructor initializes stream buffer
gzifstream()374 gzifstream::gzifstream()
375 : std::istream(NULL), sb()
376 { this->init(&sb); }
377 
378 // Initialize stream buffer and open file
gzifstream(const char * name,std::ios_base::openmode mode)379 gzifstream::gzifstream(const char* name,
380                        std::ios_base::openmode mode)
381 : std::istream(NULL), sb()
382 {
383   this->init(&sb);
384   this->open(name, mode);
385 }
386 
387 // Initialize stream buffer and attach to file
gzifstream(int fd,std::ios_base::openmode mode)388 gzifstream::gzifstream(int fd,
389                        std::ios_base::openmode mode)
390 : std::istream(NULL), sb()
391 {
392   this->init(&sb);
393   this->attach(fd, mode);
394 }
395 
396 // Open file and go into fail() state if unsuccessful
397 void
open(const char * name,std::ios_base::openmode mode)398 gzifstream::open(const char* name,
399                  std::ios_base::openmode mode)
400 {
401   if (!sb.open(name, mode | std::ios_base::in))
402     this->setstate(std::ios_base::failbit);
403   else
404     this->clear();
405 }
406 
407 // Attach to file and go into fail() state if unsuccessful
408 void
attach(int fd,std::ios_base::openmode mode)409 gzifstream::attach(int fd,
410                    std::ios_base::openmode mode)
411 {
412   if (!sb.attach(fd, mode | std::ios_base::in))
413     this->setstate(std::ios_base::failbit);
414   else
415     this->clear();
416 }
417 
418 // Close file
419 void
close()420 gzifstream::close()
421 {
422   if (!sb.close())
423     this->setstate(std::ios_base::failbit);
424 }
425 
426 /*****************************************************************************/
427 
428 // Default constructor initializes stream buffer
gzofstream()429 gzofstream::gzofstream()
430 : std::ostream(NULL), sb()
431 { this->init(&sb); }
432 
433 // Initialize stream buffer and open file
gzofstream(const char * name,std::ios_base::openmode mode)434 gzofstream::gzofstream(const char* name,
435                        std::ios_base::openmode mode)
436 : std::ostream(NULL), sb()
437 {
438   this->init(&sb);
439   this->open(name, mode);
440 }
441 
442 // Initialize stream buffer and attach to file
gzofstream(int fd,std::ios_base::openmode mode)443 gzofstream::gzofstream(int fd,
444                        std::ios_base::openmode mode)
445 : std::ostream(NULL), sb()
446 {
447   this->init(&sb);
448   this->attach(fd, mode);
449 }
450 
451 // Open file and go into fail() state if unsuccessful
452 void
open(const char * name,std::ios_base::openmode mode)453 gzofstream::open(const char* name,
454                  std::ios_base::openmode mode)
455 {
456   if (!sb.open(name, mode | std::ios_base::out))
457     this->setstate(std::ios_base::failbit);
458   else
459     this->clear();
460 }
461 
462 // Attach to file and go into fail() state if unsuccessful
463 void
attach(int fd,std::ios_base::openmode mode)464 gzofstream::attach(int fd,
465                    std::ios_base::openmode mode)
466 {
467   if (!sb.attach(fd, mode | std::ios_base::out))
468     this->setstate(std::ios_base::failbit);
469   else
470     this->clear();
471 }
472 
473 // Close file
474 void
close()475 gzofstream::close()
476 {
477   if (!sb.close())
478     this->setstate(std::ios_base::failbit);
479 }
480