仔细看了一下,这里的hashTypeSet函数的实现挺巧妙,该函数被频繁调用多次,挺重要:
#define HASH_SET_TAKE_FIELD (1<<0)
#define HASH_SET_TAKE_VALUE (1<<1)
#define HASH_SET_COPY 0
int hashTypeSet(robj *o, sds field, sds value, int flags) {
int update = 0;
if (o->encoding == OBJ_ENCODING_ZIPLIST) {
unsigned char *zl, *fptr, *vptr;
zl = o->ptr;
fptr = ziplistIndex(zl, ZIPLIST_HEAD);
if (fptr != NULL) {
fptr = ziplistFind(zl, fptr, (unsigned char*)field, sdslen(field), 1);
if (fptr != NULL) {
/* Grab pointer to the value (fptr points to the field) */
vptr = ziplistNext(zl, fptr);
serverAssert(vptr != NULL);
update = 1;
/* Replace value */
zl = ziplistReplace(zl, vptr, (unsigned char*)value,
sdslen(value));
}
}
if (!update) {
/* Push new field/value pair onto the tail of the ziplist */
zl = ziplistPush(zl, (unsigned char*)field, sdslen(field),
ZIPLIST_TAIL);
zl = ziplistPush(zl, (unsigned char*)value, sdslen(value),
ZIPLIST_TAIL);
}
o->ptr = zl;
/* Check if the ziplist needs to be converted to a hash table */
if (hashTypeLength(o) > server.hash_max_ziplist_entries)
hashTypeConvert(o, OBJ_ENCODING_HT);
} else if (o->encoding == OBJ_ENCODING_HT) {
dictEntry *de = dictFind(o->ptr,field);
if (de) {
sdsfree(dictGetVal(de));
if (flags & HASH_SET_TAKE_VALUE) {
dictGetVal(de) = value;
value = NULL;
} else {
dictGetVal(de) = sdsdup(value);
}
update = 1;
} else {
sds f,v;
if (flags & HASH_SET_TAKE_FIELD) {
f = field;
field = NULL;
} else {
f = sdsdup(field);
}
if (flags & HASH_SET_TAKE_VALUE) {
v = value;
value = NULL;
} else {
v = sdsdup(value);
}
dictAdd(o->ptr,f,v);
}
} else {
serverPanic("Unknown hash encoding");
}
/* Free SDS strings we did not referenced elsewhere if the flags
* want this function to be responsible. */
if (flags & HASH_SET_TAKE_FIELD && field) sdsfree(field);
if (flags & HASH_SET_TAKE_VALUE && value) sdsfree(value);
return update;
}
/* Delete an element from a hash.
* Return 1 on deleted and 0 on not found. */
int hashTypeDelete(robj *o, sds field) {
int deleted = 0;
if (o->encoding == OBJ_ENCODING_ZIPLIST) {
unsigned char *zl, *fptr;
zl = o->ptr;
fptr = ziplistIndex(zl, ZIPLIST_HEAD);
if (fptr != NULL) {
fptr = ziplistFind(zl, fptr, (unsigned char*)field, sdslen(field), 1);
if (fptr != NULL) {
zl = ziplistDelete(zl,&fptr); /* Delete the key. */
zl = ziplistDelete(zl,&fptr); /* Delete the value. */
o->ptr = zl;
deleted = 1;
}
}
} else if (o->encoding == OBJ_ENCODING_HT) {
if (dictDelete((dict*)o->ptr, field) == C_OK) {
deleted = 1;
/* Always check if the dictionary needs a resize after a delete. */
if (htNeedsResize(o->ptr)) dictResize(o->ptr);
}
} else {
serverPanic("Unknown hash encoding");
}
return deleted;
}