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gzip: code shrink

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function                                             old     new   delta
fill_window_if_needed                                  -     238    +238
deflate                                              924     907     -17
pack_gzip                                            809     790     -19
fill_window                                          216       -    -216
------------------------------------------------------------------------------
(add/remove: 1/1 grow/shrink: 0/2 up/down: 238/-252)          Total: -14 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko 2018-01-30 18:15:39 +01:00
parent c6d2a26fac
commit 9c499a5af4
1 changed files with 15 additions and 13 deletions
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26
archival/gzip.c
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@ -312,25 +312,24 @@ struct globals {
#define nice_match (G1.nice_match) #define nice_match (G1.nice_match)
#endif #endif
lng block_start;
/* window position at the beginning of the current output block. Gets /* window position at the beginning of the current output block. Gets
* negative when the window is moved backwards. * negative when the window is moved backwards.
*/ */
lng block_start;
unsigned ins_h; /* hash index of string to be inserted */ unsigned ins_h; /* hash index of string to be inserted */
#define H_SHIFT ((HASH_BITS+MIN_MATCH-1) / MIN_MATCH)
/* Number of bits by which ins_h and del_h must be shifted at each /* Number of bits by which ins_h and del_h must be shifted at each
* input step. It must be such that after MIN_MATCH steps, the oldest * input step. It must be such that after MIN_MATCH steps, the oldest
* byte no longer takes part in the hash key, that is: * byte no longer takes part in the hash key, that is:
* H_SHIFT * MIN_MATCH >= HASH_BITS * H_SHIFT * MIN_MATCH >= HASH_BITS
*/ */
#define H_SHIFT ((HASH_BITS+MIN_MATCH-1) / MIN_MATCH)
unsigned prev_length;
/* Length of the best match at previous step. Matches not greater than this /* Length of the best match at previous step. Matches not greater than this
* are discarded. This is used in the lazy match evaluation. * are discarded. This is used in the lazy match evaluation.
*/ */
unsigned prev_length;
unsigned strstart; /* start of string to insert */ unsigned strstart; /* start of string to insert */
unsigned match_start; /* start of matching string */ unsigned match_start; /* start of matching string */
@ -347,18 +346,17 @@ struct globals {
unsigned insize; /* valid bytes in l_buf */ unsigned insize; /* valid bytes in l_buf */
#endif #endif
unsigned outcnt; /* bytes in output buffer */ unsigned outcnt; /* bytes in output buffer */
smallint eofile; /* flag set at end of input file */ smallint eofile; /* flag set at end of input file */
/* =========================================================================== /* ===========================================================================
* Local data used by the "bit string" routines. * Local data used by the "bit string" routines.
*/ */
unsigned short bi_buf;
/* Output buffer. bits are inserted starting at the bottom (least significant /* Output buffer. bits are inserted starting at the bottom (least significant
* bits). * bits).
*/ */
unsigned short bi_buf;
#undef BUF_SIZE #undef BUF_SIZE
#define BUF_SIZE (8 * sizeof(G1.bi_buf)) #define BUF_SIZE (8 * sizeof(G1.bi_buf))
@ -662,6 +660,12 @@ static void fill_window(void)
} }
} }
} }
/* Both users fill window with the same loop: */
static void fill_window_if_needed(void)
{
while (G1.lookahead < MIN_LOOKAHEAD && !G1.eofile)
fill_window();
}
/* =========================================================================== /* ===========================================================================
@ -1894,8 +1898,7 @@ static NOINLINE ulg deflate(void)
* for the next match, plus MIN_MATCH bytes to insert the * for the next match, plus MIN_MATCH bytes to insert the
* string following the next match. * string following the next match.
*/ */
while (G1.lookahead < MIN_LOOKAHEAD && !G1.eofile) fill_window_if_needed();
fill_window();
} }
if (match_available) if (match_available)
ct_tally(0, G1.window[G1.strstart - 1]); ct_tally(0, G1.window[G1.strstart - 1]);
@ -1948,8 +1951,7 @@ static void lm_init(ush * flagsp)
/* Make sure that we always have enough lookahead. This is important /* Make sure that we always have enough lookahead. This is important
* if input comes from a device such as a tty. * if input comes from a device such as a tty.
*/ */
while (G1.lookahead < MIN_LOOKAHEAD && !G1.eofile) fill_window_if_needed();
fill_window();
//G1.ins_h = 0; // globals are zeroed in pack_gzip() //G1.ins_h = 0; // globals are zeroed in pack_gzip()
for (j = 0; j < MIN_MATCH - 1; j++) for (j = 0; j < MIN_MATCH - 1; j++)