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hush: speed optimizations

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Make o_addchr() faster: do not call o_grow_by() each time.
Create i_getch_and_eat_bkslash_nl(), use it instead of peek+getch pair.

function                                             old     new   delta
o_addchr                                              42      54     +12
parse_dollar                                         761     771     +10
o_grow_by                                             48      37     -11
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 3/1 up/down: 24/-11)             Total: 11 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko 2016-09-29 19:50:55 +02:00
parent 657086a3dc
commit 46e6498b2a
1 changed files with 27 additions and 6 deletions
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29
shell/hush.c
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@ -2373,7 +2373,7 @@ static ALWAYS_INLINE void o_free_unsafe(o_string *o)
static void o_grow_by(o_string *o, int len)
{
if (o->length + len > o->maxlen) {
o->maxlen += (2*len > B_CHUNK ? 2*len : B_CHUNK);
o->maxlen += (2 * len) | (B_CHUNK-1);
o->data = xrealloc(o->data, 1 + o->maxlen);
}
}
@ -2381,10 +2381,16 @@ static void o_grow_by(o_string *o, int len)
static void o_addchr(o_string *o, int ch)
{
debug_printf("o_addchr: '%c' o->length=%d o=%p\n", ch, o->length, o);
o_grow_by(o, 1);
if (o->length < o->maxlen) {
/* likely. avoid o_grow_by() call */
add:
o->data[o->length] = ch;
o->length++;
o->data[o->length] = '\0';
return;
}
o_grow_by(o, 1);
goto add;
}
#if 0
@ -3909,6 +3915,22 @@ static int parse_group(o_string *dest, struct parse_context *ctx,
/* command remains "open", available for possible redirects */
}
static int i_getch_and_eat_bkslash_nl(struct in_str *input)
{
for (;;) {
int ch, ch2;
ch = i_getch(input);
if (ch != '\\')
return ch;
ch2 = i_peek(input);
if (ch2 != '\n')
return ch;
/* backslash+newline, skip it */
i_getch(input);
}
}
static int i_peek_and_eat_bkslash_nl(struct in_str *input)
{
for (;;) {
@ -4149,8 +4171,7 @@ static int parse_dollar(o_string *as_string,
ch = i_getch(input); /* eat '{' */
nommu_addchr(as_string, ch);
i_peek_and_eat_bkslash_nl(input);
ch = i_getch(input); /* first char after '{' */
ch = i_getch_and_eat_bkslash_nl(input); /* first char after '{' */
/* It should be ${?}, or ${#var},
* or even ${?+subst} - operator acting on a special variable,
* or the beginning of variable name.