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SDS: use type 8 if we are likely to append to the string.

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When empty strings are created, or when sdsMakeRoomFor() is called, we
are likely into an appending pattern. Use at least type 8 SDS strings
since TYPE 5 does not remember the free allocation size and requires to
call sdsMakeRoomFor() at every new piece appended.
This commit is contained in:
antirez 2015-07-23 09:16:47 +02:00
parent cf68f4ee6a
commit ea9bd243ec
1 changed files with 11 additions and 0 deletions
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11
src/sds.c
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@ -80,6 +80,9 @@ sds sdsnewlen(const void *init, size_t initlen) {
void *sh;
sds s;
char type = sdsReqType(initlen);
/* Empty strings are usually created in order to append. Use type 8
* since type 5 is not good at this. */
if (type == SDS_TYPE_5 && initlen == 0) type = SDS_TYPE_8;
int hdrlen = sdsHdrSize(type);
unsigned char *fp; /* flags pointer. */
@ -193,7 +196,9 @@ sds sdsMakeRoomFor(sds s, size_t addlen) {
char type, oldtype = s[-1] & SDS_TYPE_MASK;
int hdrlen;
/* Return ASAP if there is enough space left. */
if (avail >= addlen) return s;
len = sdslen(s);
sh = (char*)s-sdsHdrSize(oldtype);
newlen = (len+addlen);
@ -203,6 +208,12 @@ sds sdsMakeRoomFor(sds s, size_t addlen) {
newlen += SDS_MAX_PREALLOC;
type = sdsReqType(newlen);
/* Don't use type 5: the user is appending to the string and type 5 is
* not able to remember empty space, so sdsMakeRoomFor() must be called
* at every appending operation. */
if (type == SDS_TYPE_5) type = SDS_TYPE_8;
hdrlen = sdsHdrSize(type);
if (oldtype==type) {
newsh = zrealloc(sh, hdrlen+newlen+1);