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Fixed memory allocation problems when compressing multi-MB

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items. Lookup history is now a double linked list, used in
a wrap-around style.

Jan
This commit is contained in:
Jan Wieck 2000-07-20 14:23:28 +00:00
parent 6a00a7eb72
commit 9b0fe4eee2
1 changed files with 35 additions and 28 deletions

63
src/backend/utils/adt/pg_lzcompress.c
View File

@ -1,7 +1,7 @@
/* ----------
* pg_lzcompress.c -
*
* $Header: /cvsroot/pgsql/src/backend/utils/adt/pg_lzcompress.c,v 1.7 2000/07/06 21:02:07 wieck Exp $
* $Header: /cvsroot/pgsql/src/backend/utils/adt/pg_lzcompress.c,v 1.8 2000/07/20 14:23:28 wieck Exp $
*
* This is an implementation of LZ compression for PostgreSQL.
* It uses a simple history table and generates 2-3 byte tags
@ -185,9 +185,9 @@
* Local definitions
* ----------
*/
#define PGLZ_HISTORY_SIZE 8192
#define PGLZ_HISTORY_LISTS 8192
#define PGLZ_HISTORY_MASK 0x1fff
#define PGLZ_HISTORY_PREALLOC 8192
#define PGLZ_HISTORY_SIZE 4096
#define PGLZ_MAX_MATCH 273
@ -200,6 +200,7 @@
typedef struct PGLZ_HistEntry
{
struct PGLZ_HistEntry *next;
struct PGLZ_HistEntry *prev;
char *pos;
} PGLZ_HistEntry;
@ -209,7 +210,7 @@ typedef struct PGLZ_HistEntry
* ----------
*/
static PGLZ_Strategy strategy_default_data = {
256, /* Data chunks smaller 256 bytes are nott
256, /* Data chunks smaller 256 bytes are not
* compressed */
6144, /* Data chunks greater equal 6K force
* compression */
@ -247,6 +248,12 @@ static PGLZ_Strategy strategy_never_data = {
};
PGLZ_Strategy *PGLZ_strategy_never = &strategy_never_data;
/* ----------
* Global arrays for history
* ----------
*/
static PGLZ_HistEntry *hist_start[PGLZ_HISTORY_LISTS];
static PGLZ_HistEntry hist_entries[PGLZ_HISTORY_SIZE];
/* ----------
@ -276,11 +283,26 @@ PGLZ_Strategy *PGLZ_strategy_never = &strategy_never_data;
* Adds a new entry to the history table.
* ----------
*/
#define pglz_hist_add(_hs,_hn,_s,_e) { \
#define pglz_hist_add(_hs,_he,_hn,_s,_e) { \
int __hindex = pglz_hist_idx((_s),(_e)); \
(_hn)->next = (_hs)[__hindex]; \
(_hn)->pos = (_s); \
(_hs)[__hindex] = (_hn)++; \
if ((_he)[(_hn)].prev == NULL) { \
(_hs)[__hindex] = (_he)[(_hn)].next; \
} else { \
(_he)[(_hn)].prev->next = (_he)[(_hn)].next; \
} \
if ((_he)[(_hn)].next != NULL) { \
(_he)[(_hn)].next->prev = (_he)[(_hn)].prev; \
} \
(_he)[(_hn)].next = (_hs)[__hindex]; \
(_he)[(_hn)].prev = NULL; \
(_he)[(_hn)].pos = (_s); \
if ((_hs)[__hindex] != NULL) { \
(_hs)[__hindex]->prev = &((_he)[(_hn)]); \
} \
(_hs)[__hindex] = &((_he)[(_hn)]); \
if (++(_hn) >= PGLZ_HISTORY_SIZE) { \
(_hn) = 0; \
} \
}
@ -454,10 +476,7 @@ pglz_find_match(PGLZ_HistEntry **hstart, char *input, char *end,
int
pglz_compress(char *source, int slen, PGLZ_Header *dest, PGLZ_Strategy *strategy)
{
PGLZ_HistEntry *hist_start[PGLZ_HISTORY_SIZE];
PGLZ_HistEntry *hist_alloc;
PGLZ_HistEntry hist_prealloc[PGLZ_HISTORY_PREALLOC];
PGLZ_HistEntry *hist_next;
int hist_next = 0;
unsigned char *bp = ((unsigned char *) dest) + sizeof(PGLZ_Header);
unsigned char *bstart = bp;
@ -524,17 +543,12 @@ pglz_compress(char *source, int slen, PGLZ_Header *dest, PGLZ_Strategy *strategy
/* ----------
* Initialize the history tables. For inputs smaller than
* PGLZ_HISTORY_PREALLOC, we already have a big enough history
* PGLZ_HISTORY_SIZE, we already have a big enough history
* table on the stack frame.
* ----------
*/
memset((void *) hist_start, 0, sizeof(hist_start));
if (slen + 1 <= PGLZ_HISTORY_PREALLOC)
hist_alloc = hist_prealloc;
else
hist_alloc = (PGLZ_HistEntry *)
palloc(sizeof(PGLZ_HistEntry) * (slen + 1));
hist_next = hist_alloc;
memset((void *) hist_entries, 0, sizeof(hist_entries));
/* ----------
* 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
pglz_out_tag(ctrlp, ctrlb, ctrl, bp, match_len, match_off);
while (match_len--)
{
pglz_hist_add(hist_start, hist_next, dp, dend);
pglz_hist_add(hist_start, hist_entries, hist_next, dp, dend);
dp++; /* Do not do this ++ in the line above! */
/* The macro would do it four times - Jan. */
}
@ -600,19 +614,12 @@ pglz_compress(char *source, int slen, PGLZ_Header *dest, PGLZ_Strategy *strategy
* ----------
*/
pglz_out_literal(ctrlp, ctrlb, ctrl, bp, *dp);
pglz_hist_add(hist_start, hist_next, dp, dend);
pglz_hist_add(hist_start, hist_entries, hist_next, dp, dend);
dp++; /* Do not do this ++ in the line above! */
/* The macro would do it four times - Jan. */
}
}
/* ----------
* Get rid of the history (if allocated)
* ----------
*/
if (hist_alloc != hist_prealloc)
pfree((void *) hist_alloc);
/* ----------
* If we are still in compressing mode, write out the last
* control byte and determine if the compression gained the