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Commit9b0fe4e

Browse files
Jan WieckJan Wieck
Jan Wieck
authored and
Jan Wieck
committed
Fixed memory allocation problems when compressing multi-MB
items. Lookup history is now a double linked list, used ina wrap-around style.Jan
1 parent6a00a7e commit9b0fe4e

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1 file changed

+35
-28
lines changed

1 file changed

+35
-28
lines changed

‎src/backend/utils/adt/pg_lzcompress.c‎

Lines changed: 35 additions & 28 deletions
Original file line numberDiff line numberDiff line change
@@ -1,7 +1,7 @@
11
/* ----------
22
* pg_lzcompress.c -
33
*
4-
* $Header: /cvsroot/pgsql/src/backend/utils/adt/pg_lzcompress.c,v 1.7 2000/07/06 21:02:07 wieck Exp $
4+
* $Header: /cvsroot/pgsql/src/backend/utils/adt/pg_lzcompress.c,v 1.8 2000/07/20 14:23:28 wieck Exp $
55
*
66
*This is an implementation of LZ compression for PostgreSQL.
77
*It uses a simple history table and generates 2-3 byte tags
@@ -185,9 +185,9 @@
185185
* Local definitions
186186
* ----------
187187
*/
188-
#definePGLZ_HISTORY_SIZE8192
188+
#definePGLZ_HISTORY_LISTS8192
189189
#definePGLZ_HISTORY_MASK0x1fff
190-
#definePGLZ_HISTORY_PREALLOC8192
190+
#definePGLZ_HISTORY_SIZE4096
191191
#definePGLZ_MAX_MATCH273
192192

193193

@@ -200,6 +200,7 @@
200200
typedefstructPGLZ_HistEntry
201201
{
202202
structPGLZ_HistEntry*next;
203+
structPGLZ_HistEntry*prev;
203204
char*pos;
204205
}PGLZ_HistEntry;
205206

@@ -209,7 +210,7 @@ typedef struct PGLZ_HistEntry
209210
* ----------
210211
*/
211212
staticPGLZ_Strategystrategy_default_data= {
212-
256,/* Data chunks smaller 256 bytes arenott
213+
256,/* Data chunks smaller 256 bytes arenot
213214
* compressed */
214215
6144,/* Data chunks greater equal 6K force
215216
* compression */
@@ -247,6 +248,12 @@ static PGLZ_Strategy strategy_never_data = {
247248
};
248249
PGLZ_Strategy*PGLZ_strategy_never=&strategy_never_data;
249250

251+
/* ----------
252+
* Global arrays for history
253+
* ----------
254+
*/
255+
staticPGLZ_HistEntry*hist_start[PGLZ_HISTORY_LISTS];
256+
staticPGLZ_HistEntryhist_entries[PGLZ_HISTORY_SIZE];
250257

251258

252259
/* ----------
@@ -276,11 +283,26 @@ PGLZ_Strategy *PGLZ_strategy_never = &strategy_never_data;
276283
*Adds a new entry to the history table.
277284
* ----------
278285
*/
279-
#definepglz_hist_add(_hs,_hn,_s,_e) {\
286+
#definepglz_hist_add(_hs,_he,_hn,_s,_e) {\
280287
int __hindex = pglz_hist_idx((_s),(_e));\
281-
(_hn)->next = (_hs)[__hindex];\
282-
(_hn)->pos= (_s);\
283-
(_hs)[__hindex] = (_hn)++;\
288+
if ((_he)[(_hn)].prev == NULL) {\
289+
(_hs)[__hindex] = (_he)[(_hn)].next;\
290+
} else {\
291+
(_he)[(_hn)].prev->next = (_he)[(_hn)].next;\
292+
}\
293+
if ((_he)[(_hn)].next != NULL) {\
294+
(_he)[(_hn)].next->prev = (_he)[(_hn)].prev;\
295+
}\
296+
(_he)[(_hn)].next = (_hs)[__hindex];\
297+
(_he)[(_hn)].prev = NULL;\
298+
(_he)[(_hn)].pos = (_s);\
299+
if ((_hs)[__hindex] != NULL) {\
300+
(_hs)[__hindex]->prev = &((_he)[(_hn)]);\
301+
}\
302+
(_hs)[__hindex] = &((_he)[(_hn)]);\
303+
if (++(_hn) >= PGLZ_HISTORY_SIZE) {\
304+
(_hn) = 0;\
305+
}\
284306
}
285307

286308

@@ -454,10 +476,7 @@ pglz_find_match(PGLZ_HistEntry **hstart, char *input, char *end,
454476
int
455477
pglz_compress(char*source,intslen,PGLZ_Header*dest,PGLZ_Strategy*strategy)
456478
{
457-
PGLZ_HistEntry*hist_start[PGLZ_HISTORY_SIZE];
458-
PGLZ_HistEntry*hist_alloc;
459-
PGLZ_HistEntryhist_prealloc[PGLZ_HISTORY_PREALLOC];
460-
PGLZ_HistEntry*hist_next;
479+
inthist_next=0;
461480

462481
unsignedchar*bp= ((unsignedchar*)dest)+sizeof(PGLZ_Header);
463482
unsignedchar*bstart=bp;
@@ -524,17 +543,12 @@ pglz_compress(char *source, int slen, PGLZ_Header *dest, PGLZ_Strategy *strategy
524543

525544
/* ----------
526545
* Initialize the history tables. For inputs smaller than
527-
*PGLZ_HISTORY_PREALLOC, we already have a big enough history
546+
*PGLZ_HISTORY_SIZE, we already have a big enough history
528547
* table on the stack frame.
529548
* ----------
530549
*/
531550
memset((void*)hist_start,0,sizeof(hist_start));
532-
if (slen+1 <=PGLZ_HISTORY_PREALLOC)
533-
hist_alloc=hist_prealloc;
534-
else
535-
hist_alloc= (PGLZ_HistEntry*)
536-
palloc(sizeof(PGLZ_HistEntry)* (slen+1));
537-
hist_next=hist_alloc;
551+
memset((void*)hist_entries,0,sizeof(hist_entries));
538552

539553
/* ----------
540554
* Compute the maximum result size allowed by the strategy.
@@ -588,7 +602,7 @@ pglz_compress(char *source, int slen, PGLZ_Header *dest, PGLZ_Strategy *strategy
588602
pglz_out_tag(ctrlp,ctrlb,ctrl,bp,match_len,match_off);
589603
while (match_len--)
590604
{
591-
pglz_hist_add(hist_start,hist_next,dp,dend);
605+
pglz_hist_add(hist_start,hist_entries,hist_next,dp,dend);
592606
dp++;/* Do not do this ++ in the line above!*/
593607
/* The macro would do it four times - Jan.*/
594608
}
@@ -600,19 +614,12 @@ pglz_compress(char *source, int slen, PGLZ_Header *dest, PGLZ_Strategy *strategy
600614
* ----------
601615
*/
602616
pglz_out_literal(ctrlp,ctrlb,ctrl,bp,*dp);
603-
pglz_hist_add(hist_start,hist_next,dp,dend);
617+
pglz_hist_add(hist_start,hist_entries,hist_next,dp,dend);
604618
dp++;/* Do not do this ++ in the line above!*/
605619
/* The macro would do it four times - Jan.*/
606620
}
607621
}
608622

609-
/* ----------
610-
* Get rid of the history (if allocated)
611-
* ----------
612-
*/
613-
if (hist_alloc!=hist_prealloc)
614-
pfree((void*)hist_alloc);
615-
616623
/* ----------
617624
* If we are still in compressing mode, write out the last
618625
* control byte and determine if the compression gained the

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