File : tree_io.adb
1 ------------------------------------------------------------------------------
2 -- --
3 -- GNAT COMPILER COMPONENTS --
4 -- --
5 -- T R E E _ I O --
6 -- --
7 -- B o d y --
8 -- --
9 -- Copyright (C) 1992-2014, Free Software Foundation, Inc. --
10 -- --
11 -- GNAT is free software; you can redistribute it and/or modify it under --
12 -- terms of the GNU General Public License as published by the Free Soft- --
13 -- ware Foundation; either version 3, or (at your option) any later ver- --
14 -- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
15 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
16 -- or FITNESS FOR A PARTICULAR PURPOSE. --
17 -- --
18 -- --
19 -- --
20 -- --
21 -- --
22 -- You should have received a copy of the GNU General Public License and --
23 -- a copy of the GCC Runtime Library Exception along with this program; --
24 -- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
25 -- <http://www.gnu.org/licenses/>. --
26 -- --
27 -- GNAT was originally developed by the GNAT team at New York University. --
28 -- Extensive contributions were provided by Ada Core Technologies Inc. --
29 -- --
30 ------------------------------------------------------------------------------
31
32 with Debug; use Debug;
33 with Output; use Output;
34 with Unchecked_Conversion;
35
36 package body Tree_IO is
37 Debug_Flag_Tree : Boolean := False;
38 -- Debug flag for debug output from tree read/write
39
40 -------------------------------------------
41 -- Compression Scheme Used for Tree File --
42 -------------------------------------------
43
44 -- We don't just write the data directly, but instead do a mild form
45 -- of compression, since we expect lots of compressible zeroes and
46 -- blanks. The compression scheme is as follows:
47
48 -- 00nnnnnn followed by nnnnnn bytes (non compressed data)
49 -- 01nnnnnn indicates nnnnnn binary zero bytes
50 -- 10nnnnnn indicates nnnnnn ASCII space bytes
51 -- 11nnnnnn bbbbbbbb indicates nnnnnnnn occurrences of byte bbbbbbbb
52
53 -- Since we expect many zeroes in trees, and many spaces in sources,
54 -- this compression should be reasonably efficient. We can put in
55 -- something better later on.
56
57 -- Note that this compression applies to the Write_Tree_Data and
58 -- Read_Tree_Data calls, not to the calls to read and write single
59 -- scalar values, which are written in memory format without any
60 -- compression.
61
62 C_Noncomp : constant := 2#00_000000#;
63 C_Zeros : constant := 2#01_000000#;
64 C_Spaces : constant := 2#10_000000#;
65 C_Repeat : constant := 2#11_000000#;
66 -- Codes for compression sequences
67
68 Max_Count : constant := 63;
69 -- Maximum data length for one compression sequence
70
71 -- The above compression scheme applies only to data written with the
72 -- Tree_Write routine and read with Tree_Read. Data written using the
73 -- Tree_Write_Char or Tree_Write_Int routines and read using the
74 -- corresponding input routines is not compressed.
75
76 type Int_Bytes is array (1 .. 4) of Byte;
77 for Int_Bytes'Size use 32;
78
79 function To_Int_Bytes is new Unchecked_Conversion (Int, Int_Bytes);
80 function To_Int is new Unchecked_Conversion (Int_Bytes, Int);
81
82 ----------------------
83 -- Global Variables --
84 ----------------------
85
86 Tree_FD : File_Descriptor;
87 -- File descriptor for tree
88
89 Buflen : constant Int := 8_192;
90 -- Length of buffer for read and write file data
91
92 Buf : array (Pos range 1 .. Buflen) of Byte;
93 -- Read/write file data buffer
94
95 Bufn : Nat;
96 -- Number of bytes read/written from/to buffer
97
98 Buft : Nat;
99 -- Total number of bytes in input buffer containing valid data. Used only
100 -- for input operations. There is data left to be processed in the buffer
101 -- if Buft > Bufn. A value of zero for Buft means that the buffer is empty.
102
103 -----------------------
104 -- Local Subprograms --
105 -----------------------
106
107 procedure Read_Buffer;
108 -- Reads data into buffer, setting Bufn appropriately
109
110 function Read_Byte return Byte;
111 pragma Inline (Read_Byte);
112 -- Returns next byte from input file, raises Tree_Format_Error if none left
113
114 procedure Write_Buffer;
115 -- Writes out current buffer contents
116
117 procedure Write_Byte (B : Byte);
118 pragma Inline (Write_Byte);
119 -- Write one byte to output buffer, checking for buffer-full condition
120
121 -----------------
122 -- Read_Buffer --
123 -----------------
124
125 procedure Read_Buffer is
126 begin
127 Buft := Int (Read (Tree_FD, Buf (1)'Address, Integer (Buflen)));
128
129 if Buft = 0 then
130 raise Tree_Format_Error;
131 else
132 Bufn := 0;
133 end if;
134 end Read_Buffer;
135
136 ---------------
137 -- Read_Byte --
138 ---------------
139
140 function Read_Byte return Byte is
141 begin
142 if Bufn = Buft then
143 Read_Buffer;
144 end if;
145
146 Bufn := Bufn + 1;
147 return Buf (Bufn);
148 end Read_Byte;
149
150 --------------------
151 -- Tree_Read_Bool --
152 --------------------
153
154 procedure Tree_Read_Bool (B : out Boolean) is
155 begin
156 B := Boolean'Val (Read_Byte);
157
158 if Debug_Flag_Tree then
159 if B then
160 Write_Str ("True");
161 else
162 Write_Str ("False");
163 end if;
164
165 Write_Eol;
166 end if;
167 end Tree_Read_Bool;
168
169 --------------------
170 -- Tree_Read_Char --
171 --------------------
172
173 procedure Tree_Read_Char (C : out Character) is
174 begin
175 C := Character'Val (Read_Byte);
176
177 if Debug_Flag_Tree then
178 Write_Str ("==> transmitting Character = ");
179 Write_Char (C);
180 Write_Eol;
181 end if;
182 end Tree_Read_Char;
183
184 --------------------
185 -- Tree_Read_Data --
186 --------------------
187
188 procedure Tree_Read_Data (Addr : Address; Length : Int) is
189
190 type S is array (Pos) of Byte;
191 -- This is a big array, for which we have to suppress the warning
192
193 type SP is access all S;
194
195 function To_SP is new Unchecked_Conversion (Address, SP);
196
197 Data : constant SP := To_SP (Addr);
198 -- Data buffer to be read as an indexable array of bytes
199
200 OP : Pos := 1;
201 -- Pointer to next byte of data buffer to be read into
202
203 B : Byte;
204 C : Byte;
205 L : Int;
206
207 begin
208 if Debug_Flag_Tree then
209 Write_Str ("==> transmitting ");
210 Write_Int (Length);
211 Write_Str (" data bytes");
212 Write_Eol;
213 end if;
214
215 -- Verify data length
216
217 Tree_Read_Int (L);
218
219 if L /= Length then
220 Write_Str ("==> transmitting, expected ");
221 Write_Int (Length);
222 Write_Str (" bytes, found length = ");
223 Write_Int (L);
224 Write_Eol;
225 raise Tree_Format_Error;
226 end if;
227
228 -- Loop to read data
229
230 while OP <= Length loop
231
232 -- Get compression control character
233
234 B := Read_Byte;
235 C := B and 2#00_111111#;
236 B := B and 2#11_000000#;
237
238 -- Non-repeat case
239
240 if B = C_Noncomp then
241 if Debug_Flag_Tree then
242 Write_Str ("==> uncompressed: ");
243 Write_Int (Int (C));
244 Write_Str (", starting at ");
245 Write_Int (OP);
246 Write_Eol;
247 end if;
248
249 for J in 1 .. C loop
250 Data (OP) := Read_Byte;
251 OP := OP + 1;
252 end loop;
253
254 -- Repeated zeroes
255
256 elsif B = C_Zeros then
257 if Debug_Flag_Tree then
258 Write_Str ("==> zeroes: ");
259 Write_Int (Int (C));
260 Write_Str (", starting at ");
261 Write_Int (OP);
262 Write_Eol;
263 end if;
264
265 for J in 1 .. C loop
266 Data (OP) := 0;
267 OP := OP + 1;
268 end loop;
269
270 -- Repeated spaces
271
272 elsif B = C_Spaces then
273 if Debug_Flag_Tree then
274 Write_Str ("==> spaces: ");
275 Write_Int (Int (C));
276 Write_Str (", starting at ");
277 Write_Int (OP);
278 Write_Eol;
279 end if;
280
281 for J in 1 .. C loop
282 Data (OP) := Character'Pos (' ');
283 OP := OP + 1;
284 end loop;
285
286 -- Specified repeated character
287
288 else -- B = C_Repeat
289 B := Read_Byte;
290
291 if Debug_Flag_Tree then
292 Write_Str ("==> other char: ");
293 Write_Int (Int (C));
294 Write_Str (" (");
295 Write_Int (Int (B));
296 Write_Char (')');
297 Write_Str (", starting at ");
298 Write_Int (OP);
299 Write_Eol;
300 end if;
301
302 for J in 1 .. C loop
303 Data (OP) := B;
304 OP := OP + 1;
305 end loop;
306 end if;
307 end loop;
308
309 -- At end of loop, data item must be exactly filled
310
311 if OP /= Length + 1 then
312 raise Tree_Format_Error;
313 end if;
314
315 end Tree_Read_Data;
316
317 --------------------------
318 -- Tree_Read_Initialize --
319 --------------------------
320
321 procedure Tree_Read_Initialize (Desc : File_Descriptor) is
322 begin
323 Buft := 0;
324 Bufn := 0;
325 Tree_FD := Desc;
326 Debug_Flag_Tree := Debug_Flag_5;
327 end Tree_Read_Initialize;
328
329 -------------------
330 -- Tree_Read_Int --
331 -------------------
332
333 procedure Tree_Read_Int (N : out Int) is
334 N_Bytes : Int_Bytes;
335
336 begin
337 for J in 1 .. 4 loop
338 N_Bytes (J) := Read_Byte;
339 end loop;
340
341 N := To_Int (N_Bytes);
342
343 if Debug_Flag_Tree then
344 Write_Str ("==> transmitting Int = ");
345 Write_Int (N);
346 Write_Eol;
347 end if;
348 end Tree_Read_Int;
349
350 -------------------
351 -- Tree_Read_Str --
352 -------------------
353
354 procedure Tree_Read_Str (S : out String_Ptr) is
355 N : Nat;
356
357 begin
358 Tree_Read_Int (N);
359 S := new String (1 .. Natural (N));
360 Tree_Read_Data (S.all (1)'Address, N);
361 end Tree_Read_Str;
362
363 -------------------------
364 -- Tree_Read_Terminate --
365 -------------------------
366
367 procedure Tree_Read_Terminate is
368 begin
369 -- Must be at end of input buffer, so we should get Tree_Format_Error
370 -- if we try to read one more byte, if not, we have a format error.
371
372 declare
373 B : Byte;
374 pragma Warnings (Off, B);
375
376 begin
377 B := Read_Byte;
378
379 exception
380 when Tree_Format_Error => return;
381 end;
382
383 raise Tree_Format_Error;
384 end Tree_Read_Terminate;
385
386 ---------------------
387 -- Tree_Write_Bool --
388 ---------------------
389
390 procedure Tree_Write_Bool (B : Boolean) is
391 begin
392 if Debug_Flag_Tree then
393 Write_Str ("==> transmitting Boolean = ");
394
395 if B then
396 Write_Str ("True");
397 else
398 Write_Str ("False");
399 end if;
400
401 Write_Eol;
402 end if;
403
404 Write_Byte (Boolean'Pos (B));
405 end Tree_Write_Bool;
406
407 ---------------------
408 -- Tree_Write_Char --
409 ---------------------
410
411 procedure Tree_Write_Char (C : Character) is
412 begin
413 if Debug_Flag_Tree then
414 Write_Str ("==> transmitting Character = ");
415 Write_Char (C);
416 Write_Eol;
417 end if;
418
419 Write_Byte (Character'Pos (C));
420 end Tree_Write_Char;
421
422 ---------------------
423 -- Tree_Write_Data --
424 ---------------------
425
426 procedure Tree_Write_Data (Addr : Address; Length : Int) is
427
428 type S is array (Pos) of Byte;
429 -- This is a big array, for which we have to suppress the warning
430
431 type SP is access all S;
432
433 function To_SP is new Unchecked_Conversion (Address, SP);
434
435 Data : constant SP := To_SP (Addr);
436 -- Pointer to data to be written, converted to array type
437
438 IP : Pos := 1;
439 -- Input buffer pointer, next byte to be processed
440
441 NC : Nat range 0 .. Max_Count := 0;
442 -- Number of bytes of non-compressible sequence
443
444 C : Byte;
445
446 procedure Write_Non_Compressed_Sequence;
447 -- Output currently collected sequence of non-compressible data
448
449 -----------------------------------
450 -- Write_Non_Compressed_Sequence --
451 -----------------------------------
452
453 procedure Write_Non_Compressed_Sequence is
454 begin
455 if NC > 0 then
456 Write_Byte (C_Noncomp + Byte (NC));
457
458 if Debug_Flag_Tree then
459 Write_Str ("==> uncompressed: ");
460 Write_Int (NC);
461 Write_Str (", starting at ");
462 Write_Int (IP - NC);
463 Write_Eol;
464 end if;
465
466 for J in reverse 1 .. NC loop
467 Write_Byte (Data (IP - J));
468 end loop;
469
470 NC := 0;
471 end if;
472 end Write_Non_Compressed_Sequence;
473
474 -- Start of processing for Tree_Write_Data
475
476 begin
477 if Debug_Flag_Tree then
478 Write_Str ("==> transmitting ");
479 Write_Int (Length);
480 Write_Str (" data bytes");
481 Write_Eol;
482 end if;
483
484 -- We write the count at the start, so that we can check it on
485 -- the corresponding read to make sure that reads and writes match
486
487 Tree_Write_Int (Length);
488
489 -- Conversion loop
490 -- IP is index of next input character
491 -- NC is number of non-compressible bytes saved up
492
493 loop
494 -- If input is completely processed, then we are all done
495
496 if IP > Length then
497 Write_Non_Compressed_Sequence;
498 return;
499 end if;
500
501 -- Test for compressible sequence, must be at least three identical
502 -- bytes in a row to be worthwhile compressing.
503
504 if IP + 2 <= Length
505 and then Data (IP) = Data (IP + 1)
506 and then Data (IP) = Data (IP + 2)
507 then
508 Write_Non_Compressed_Sequence;
509
510 -- Count length of new compression sequence
511
512 C := 3;
513 IP := IP + 3;
514
515 while IP < Length
516 and then Data (IP) = Data (IP - 1)
517 and then C < Max_Count
518 loop
519 C := C + 1;
520 IP := IP + 1;
521 end loop;
522
523 -- Output compression sequence
524
525 if Data (IP - 1) = 0 then
526 if Debug_Flag_Tree then
527 Write_Str ("==> zeroes: ");
528 Write_Int (Int (C));
529 Write_Str (", starting at ");
530 Write_Int (IP - Int (C));
531 Write_Eol;
532 end if;
533
534 Write_Byte (C_Zeros + C);
535
536 elsif Data (IP - 1) = Character'Pos (' ') then
537 if Debug_Flag_Tree then
538 Write_Str ("==> spaces: ");
539 Write_Int (Int (C));
540 Write_Str (", starting at ");
541 Write_Int (IP - Int (C));
542 Write_Eol;
543 end if;
544
545 Write_Byte (C_Spaces + C);
546
547 else
548 if Debug_Flag_Tree then
549 Write_Str ("==> other char: ");
550 Write_Int (Int (C));
551 Write_Str (" (");
552 Write_Int (Int (Data (IP - 1)));
553 Write_Char (')');
554 Write_Str (", starting at ");
555 Write_Int (IP - Int (C));
556 Write_Eol;
557 end if;
558
559 Write_Byte (C_Repeat + C);
560 Write_Byte (Data (IP - 1));
561 end if;
562
563 -- No compression possible here
564
565 else
566 -- Output non-compressed sequence if at maximum length
567
568 if NC = Max_Count then
569 Write_Non_Compressed_Sequence;
570 end if;
571
572 NC := NC + 1;
573 IP := IP + 1;
574 end if;
575 end loop;
576
577 end Tree_Write_Data;
578
579 ---------------------------
580 -- Tree_Write_Initialize --
581 ---------------------------
582
583 procedure Tree_Write_Initialize (Desc : File_Descriptor) is
584 begin
585 Bufn := 0;
586 Tree_FD := Desc;
587 Set_Standard_Error;
588 Debug_Flag_Tree := Debug_Flag_5;
589 end Tree_Write_Initialize;
590
591 --------------------
592 -- Tree_Write_Int --
593 --------------------
594
595 procedure Tree_Write_Int (N : Int) is
596 N_Bytes : constant Int_Bytes := To_Int_Bytes (N);
597
598 begin
599 if Debug_Flag_Tree then
600 Write_Str ("==> transmitting Int = ");
601 Write_Int (N);
602 Write_Eol;
603 end if;
604
605 for J in 1 .. 4 loop
606 Write_Byte (N_Bytes (J));
607 end loop;
608 end Tree_Write_Int;
609
610 --------------------
611 -- Tree_Write_Str --
612 --------------------
613
614 procedure Tree_Write_Str (S : String_Ptr) is
615 begin
616 Tree_Write_Int (S'Length);
617 Tree_Write_Data (S (1)'Address, S'Length);
618 end Tree_Write_Str;
619
620 --------------------------
621 -- Tree_Write_Terminate --
622 --------------------------
623
624 procedure Tree_Write_Terminate is
625 begin
626 if Bufn > 0 then
627 Write_Buffer;
628 end if;
629 end Tree_Write_Terminate;
630
631 ------------------
632 -- Write_Buffer --
633 ------------------
634
635 procedure Write_Buffer is
636 begin
637 if Integer (Bufn) = Write (Tree_FD, Buf'Address, Integer (Bufn)) then
638 Bufn := 0;
639
640 else
641 Set_Standard_Error;
642 Write_Str ("fatal error: disk full");
643 OS_Exit (2);
644 end if;
645 end Write_Buffer;
646
647 ----------------
648 -- Write_Byte --
649 ----------------
650
651 procedure Write_Byte (B : Byte) is
652 begin
653 Bufn := Bufn + 1;
654 Buf (Bufn) := B;
655
656 if Bufn = Buflen then
657 Write_Buffer;
658 end if;
659 end Write_Byte;
660
661 end Tree_IO;