/* Try to encode a string object in order to save space */
robj *tryObjectEncoding(robj *o) {
long value;
sds s = o->ptr;
size_t len;
serverAssertWithInfo(NULL,o,o->type == OBJ_STRING);
if (!sdsEncodedObject(o)) return o;
if (o->refcount > 1) return o;
len = sdslen(s);
if (len <= 20 && string2l(s,len,&value)) {
if ((server.maxmemory == 0 ||
!(server.maxmemory_policy & MAXMEMORY_FLAG_NO_SHARED_INTEGERS)) &&
value >= 0 &&
value < OBJ_SHARED_INTEGERS)
{
decrRefCount(o);
incrRefCount(shared.integers[value]);
return shared.integers[value];
} else {
if (o->encoding == OBJ_ENCODING_RAW) {
sdsfree(o->ptr);
o->encoding = OBJ_ENCODING_INT;
o->ptr = (void*) value;
return o;
} else if (o->encoding == OBJ_ENCODING_EMBSTR) {
decrRefCount(o);
return createStringObjectFromLongLongForValue(value);
}
}
}
if (len <= OBJ_ENCODING_EMBSTR_SIZE_LIMIT) {
robj *emb;
if (o->encoding == OBJ_ENCODING_EMBSTR) return o;
emb = createEmbeddedStringObject(s,sdslen(s));
decrRefCount(o);
return emb;
}
trimStringObjectIfNeeded(o);
return o;
}
o->ptr = (void*) value;
return o;
上面的这段代码为什么可以这么写?
具体位置在:
if (len <= 20 && string2l(s,len,&value)) 下的
if (o->encoding == OBJ_ENCODING_RAW)