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authorDenys Vlasenko <vda.linux@googlemail.com>2016-09-29 19:50:55 +0200
committerDenys Vlasenko <vda.linux@googlemail.com>2016-09-29 19:50:55 +0200
commit46e6498b2afccd093d03697313e0d0c2f6e4d38d (patch)
tree7527d9c60c2e58da81242bdaa185ff894f26a496
parent657086a3dc573649165a5271473fa1bcf58dc9ed (diff)
downloadbusybox-46e6498b2afccd093d03697313e0d0c2f6e4d38d.tar.gz
hush: speed optimizations
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>
-rw-r--r--shell/hush.c33
1 files changed, 27 insertions, 6 deletions
diff --git a/shell/hush.c b/shell/hush.c
index 177a794b5..65d7d870b 100644
--- a/shell/hush.c
+++ b/shell/hush.c
@@ -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);
+ 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);
- o->data[o->length] = ch;
- o->length++;
- o->data[o->length] = '\0';
+ 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.