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avoid unnecessary allocation of empty string in common case of regexp-.../full result

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This commit is contained in:
Matthew Flatt 2010-04-15 11:26:37 -04:00
parent 249a9e38f7
commit 406a38148d
1 changed files with 25 additions and 16 deletions
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41
src/mzscheme/src/regexp.c
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@ -116,6 +116,8 @@ static unsigned char *extract_regstart(rxpos scan, int *_anch);
static int check_and_propagate_depends(void); static int check_and_propagate_depends(void);
static int merge_tables(Scheme_Hash_Table *dest, Scheme_Hash_Table *src); static int merge_tables(Scheme_Hash_Table *dest, Scheme_Hash_Table *src);
READ_ONLY static Scheme_Object *empty_byte_string;
#define FAIL(m) { regcomperror(m); return 0; } #define FAIL(m) { regcomperror(m); return 0; }
static void static void
@ -5183,25 +5185,29 @@ static Scheme_Object *gen_compare(char *name, int pos,
|| (endp[0] - minpos < last_bytes_count)) || (endp[0] - minpos < last_bytes_count))
last_bytes_count = endp[0] - minpos; last_bytes_count = endp[0] - minpos;
frompos = endp[0] - last_bytes_count; if (!last_bytes_count) {
tooffset = 0; last_bytes_str = empty_byte_string;
} else {
frompos = endp[0] - last_bytes_count;
tooffset = 0;
last_bytes_str = scheme_alloc_byte_string(last_bytes_count, 0); last_bytes_str = scheme_alloc_byte_string(last_bytes_count, 0);
if (frompos < offset) { if (frompos < offset) {
/* draw from prefix: */ /* draw from prefix: */
rxpos amt = last_bytes_count; rxpos amt = last_bytes_count;
if (frompos + last_bytes_count > offset) if (frompos + last_bytes_count > offset)
amt = offset - frompos; amt = offset - frompos;
memcpy(SCHEME_BYTE_STR_VAL(last_bytes_str) XFORM_OK_PLUS tooffset,
prefix + prefix_offset + prefix_len - (offset - frompos),
amt);
frompos += amt;
tooffset += amt;
last_bytes_count -= amt;
}
memcpy(SCHEME_BYTE_STR_VAL(last_bytes_str) XFORM_OK_PLUS tooffset, memcpy(SCHEME_BYTE_STR_VAL(last_bytes_str) XFORM_OK_PLUS tooffset,
prefix + prefix_offset + prefix_len - (offset - frompos), full_s + frompos,
amt); last_bytes_count);
frompos += amt;
tooffset += amt;
last_bytes_count -= amt;
} }
memcpy(SCHEME_BYTE_STR_VAL(last_bytes_str) XFORM_OK_PLUS tooffset,
full_s + frompos,
last_bytes_count);
} }
if (pos > 1) { if (pos > 1) {
@ -5737,6 +5743,9 @@ void scheme_regexp_initialize(Scheme_Env *env)
GC_REG_TRAV(scheme_rt_regwork, mark_regwork); GC_REG_TRAV(scheme_rt_regwork, mark_regwork);
#endif #endif
REGISTER_SO(empty_byte_string);
empty_byte_string = scheme_alloc_byte_string(0, 0);
GLOBAL_PRIM_W_ARITY("byte-regexp", make_regexp, 1, 1, env); GLOBAL_PRIM_W_ARITY("byte-regexp", make_regexp, 1, 1, env);
GLOBAL_PRIM_W_ARITY("regexp", make_utf8_regexp, 1, 1, env); GLOBAL_PRIM_W_ARITY("regexp", make_utf8_regexp, 1, 1, env);
GLOBAL_PRIM_W_ARITY("byte-pregexp", make_pregexp, 1, 1, env); GLOBAL_PRIM_W_ARITY("byte-pregexp", make_pregexp, 1, 1, env);