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t_hash.c
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t_hash.c
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/*
* Copyright (c) 2009-2012, Salvatore Sanfilippo <antirez at gmail dot com>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* * Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* * Neither the name of Redis nor the names of its contributors may be used
* to endorse or promote products derived from this software without
* specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
#include "server.h"
#include <math.h>
/*-----------------------------------------------------------------------------
* Hash type API
*----------------------------------------------------------------------------*/
/* Check the length of a number of objects to see if we need to convert a
* listpack to a real hash. Note that we only check string encoded objects
* as their string length can be queried in constant time. */
/* 检查对象的长度，看我们是否需要将一个 listpack(紧凑列表) 转换为真正的 hashtable(哈希表)
* 注意，我们只检查字符串编码的对象，因为它的字符串长度可以在 O(1) 时间内被查询到 */
void hashTypeTryConversion(robj *o, robj **argv, int start, int end) {
int i;
size_t sum = 0;
/* 如果内部编码类型不是 listpack,就不用转换了 */
if (o->encoding != OBJ_ENCODING_LISTPACK) return;
/* 使用给定的 start 到 end 范围读取 argv 参数 */
for (i = start; i <= end; i++) {
/* 检查对象类型是否为字符串编码，如果不是就不用继续检查长度 */
if (!sdsEncodedObject(argv[i]))
continue;
/* 获取字符串长度 */
size_t len = sdslen(argv[i]->ptr);
/* 检查长度是否超过限制值 hash_max_listpack_value ,
* 若超过限制则调用 hashTypeConvert 函数转换编码类型为 hashtable */
if (len > server.hash_max_listpack_value) {
hashTypeConvert(o, OBJ_ENCODING_HT);
return;
}
/* 计算字符串编码对象总和 */
sum += len;
}
/* 对字符串编码对象长度总和与目前 listpack 的大小进行加法运算，
* 检查结果是否超出 listpack 最大安全容量限制 (默认1GB)
* 若超出限制返回0，并转换编码为 hashtable */
if (!lpSafeToAdd(o->ptr, sum))
hashTypeConvert(o, OBJ_ENCODING_HT);
}
/* Get the value from a listpack encoded hash, identified by field.
* Returns -1 when the field cannot be found. */
/* 从 listpack 编码的哈希类型对象获取 value ,
* 如果查找不到返回 -1 */
int hashTypeGetFromListpack(robj *o, sds field,
unsigned char **vstr,
unsigned int *vlen,
long long *vll)
{
unsigned char *zl, *fptr = NULL, *vptr = NULL;
/* 断言：o 内部编码类型一定是 OBJ_ENCODING_LISTPACK ，否则中止 */
serverAssert(o->encoding == OBJ_ENCODING_LISTPACK);
zl = o->ptr;
fptr = lpFirst(zl);
/* 从头开始遍历整个 listpack 来查找 field 所在的 entry */
if (fptr != NULL) {
fptr = lpFind(zl, fptr, (unsigned char*)field, sdslen(field), 1);
if (fptr != NULL) {
/* Grab pointer to the value (fptr points to the field) */
/* fptr 为指向 field 的指针， vptr 为指向 value 的指针 ,
* 对于哈希类型，value 被保存在对应的 field 的下一个 entry */
vptr = lpNext(zl, fptr);
serverAssert(vptr != NULL);
}
}
/* 找到了 value , 若 value 为字符串编码则令 vstr 指向该 value,
* 若 value 为 整数编码则 vll 会指向 value */
if (vptr != NULL) {
*vstr = lpGetValue(vptr, vlen, vll);
return 0;
}
return -1;
}
/* Get the value from a hash table encoded hash, identified by field.
* Returns NULL when the field cannot be found, otherwise the SDS value
* is returned. */
/* 从 hashtable 编码的哈希类型对象获取 value ,
* 查找不到返回 NULL ,否则返回一个 sds 类型变量（ sds 是 redis 中的字符串，底层为 char* ） */
sds hashTypeGetFromHashTable(robj *o, sds field) {
dictEntry *de;
serverAssert(o->encoding == OBJ_ENCODING_HT);
/* 在字典/哈希表 dict 中查找 field 对应的 dictEntry */
de = dictFind(o->ptr, field);
if (de == NULL) return NULL;
return dictGetVal(de);
}
/* Higher level function of hashTypeGet*() that returns the hash value
* associated with the specified field. If the field is found C_OK
* is returned, otherwise C_ERR. The returned object is returned by
* reference in either *vstr and *vlen if it's returned in string form,
* or stored in *vll if it's returned as a number.
*
* If *vll is populated *vstr is set to NULL, so the caller
* can always check the function return by checking the return value
* for C_OK and checking if vll (or vstr) is NULL. */
/* hashTypeGet*() 的高级函数（我认为叫通用函数更容易理解），返回 field 对应的 value
* 如果查找成功，返回 C_OK ，否则为 C_ERR
* 如果是以字符串形式返回，则字符串值和长度的引用存储在 *vstr 和 *vlen 中
* 如果以数字形式返回，则存储在 *vll 中 (只有 listpack 会有整数编码， hashtable 依然以字符串编码保存整数）
*
* 如果 *vll 被赋值，*vstr 被设置为NULL ，反之亦然
* 所以调用者可以通过检查返回值是否返回 C_OK ，返回C_OK后检查 vll（或 vstr）是否为 NULL
*/
int hashTypeGetValue(robj *o, sds field, unsigned char **vstr, unsigned int *vlen, long long *vll) {
/* 判断内部编码类型并调用相应的函数获取 value */
if (o->encoding == OBJ_ENCODING_LISTPACK) {
*vstr = NULL;
if (hashTypeGetFromListpack(o, field, vstr, vlen, vll) == 0)
return C_OK;
} else if (o->encoding == OBJ_ENCODING_HT) {
sds value;
if ((value = hashTypeGetFromHashTable(o, field)) != NULL) {
*vstr = (unsigned char*) value;
*vlen = sdslen(value);
return C_OK;
}
} else {
serverPanic("Unknown hash encoding");
}
return C_ERR;
}
/* Like hashTypeGetValue() but returns a Redis object, which is useful for
* interaction with the hash type outside t_hash.c.
* The function returns NULL if the field is not found in the hash. Otherwise
* a newly allocated string object with the value is returned. */
/* 与 hashTypeGetValue() 类似，但返回一个 redisObject(Redis对象)，
* 这对与 t_hash.c 以外的哈希类型的交互很有用
* 如果在哈希对象中没有找到 field ，该函数返回 NULL。否则，将返回一个新分配的带有该值的字符串对象 */
robj *hashTypeGetValueObject(robj *o, sds field) {
unsigned char *vstr;
unsigned int vlen;
long long vll;
if (hashTypeGetValue(o,field,&vstr,&vlen,&vll) == C_ERR) return NULL;
if (vstr) return createStringObject((char*)vstr,vlen);
else return createStringObjectFromLongLong(vll);
}
/* Higher level function using hashTypeGet*() to return the length of the
* object associated with the requested field, or 0 if the field does not
* exist. */
/* hashTypeGet*() 的高级函数，返回与 field 相关的对象的长度。
* 对象的长度，如果 field 不存在，则返回0。 */
size_t hashTypeGetValueLength(robj *o, sds field) {
size_t len = 0;
unsigned char *vstr = NULL;
unsigned int vlen = UINT_MAX;
long long vll = LLONG_MAX;
if (hashTypeGetValue(o, field, &vstr, &vlen, &vll) == C_OK)
len = vstr ? vlen : sdigits10(vll);
return len;
}
/* Test if the specified field exists in the given hash. Returns 1 if the field
* exists, and 0 when it doesn't. */
/* 测试指定的 field 是否存在于给定的哈希类型对象中，如果存在则返回1，不存在则返回0 */
int hashTypeExists(robj *o, sds field) {
unsigned char *vstr = NULL;
unsigned int vlen = UINT_MAX;
long long vll = LLONG_MAX;
return hashTypeGetValue(o, field, &vstr, &vlen, &vll) == C_OK;
}
/* Add a new field, overwrite the old with the new value if it already exists.
* Return 0 on insert and 1 on update.
*
* By default, the key and value SDS strings are copied if needed, so the
* caller retains ownership of the strings passed. However this behavior
* can be effected by passing appropriate flags (possibly bitwise OR-ed):
*
* HASH_SET_TAKE_FIELD -- The SDS field ownership passes to the function.
* HASH_SET_TAKE_VALUE -- The SDS value ownership passes to the function.
*
* When the flags are used the caller does not need to release the passed
* SDS string(s). It's up to the function to use the string to create a new
* entry or to free the SDS string before returning to the caller.
*
* HASH_SET_COPY corresponds to no flags passed, and means the default
* semantics of copying the values if needed.
*
*/
/* 添加一个新 field-value (在 set 中 field 和 value 是成对的，field-value 表示一个 field value 对)
* 如果 field 已经存在，则用新值覆盖。
* 插入新的 field-value 时返回0，更新时返回1。
*
* 默认情况下，如果需要 field 和 value 是返回它们的字符串副本，因此调用者保留了对所传递字符串的所有权。
* 可以通过传递的标志 (flags) 来决定函数的执行方法。
*
* HASH_SET_TAKE_FIELD -- SDS field 的所有权传递给函数。
* HASH_SET_TAKE_VALUE -- SDS value 的所有权传给了函数。
*
* 当这些标志被使用时，调用者不需要自己释放所传递的 SDS 字符串，
* 函数会根据标志决定是否使用该字符串创建一个新的 entry，或在返回给调用者之前释放 SDS 字符串。
*
* HASH_SET_COPY 对应于没有设置任何标志，意味着默认的语义是在需要时复制 value。
*/
#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;
/* Check if the field is too long for listpack, and convert before adding the item.
* This is needed for HINCRBY* case since in other commands this is handled early by
* hashTypeTryConversion, so this check will be a NOP. */
/* 检查 field 和 value 是否对 listpack 来说太长，并在添加前进行编码类型转换。
* 这是在使用 HINCRBY 和 HINCRBYFLOAT 命令的情况下需要的，而在其他命令中，
* 这个编码转换问题会被 hashTypeTryConversion 提前处理，所以这个检查将是一个空操作 */
if (o->encoding == OBJ_ENCODING_LISTPACK) {
if (sdslen(field) > server.hash_max_listpack_value || sdslen(value) > server.hash_max_listpack_value)
hashTypeConvert(o, OBJ_ENCODING_HT);
}
/* 哈希对象编码类型为listpack */
if (o->encoding == OBJ_ENCODING_LISTPACK) {
unsigned char *zl, *fptr, *vptr;
zl = o->ptr;
fptr = lpFirst(zl);
/* 从头开始遍历 listpack 找到对应的 field-value */
if (fptr != NULL) {
fptr = lpFind(zl, fptr, (unsigned char*)field, sdslen(field), 1);
if (fptr != NULL) {
/* Grab pointer to the value (fptr points to the field) */
/* 获取指针所指向的 value ( fptr 指向的区域)*/
vptr = lpNext(zl, fptr);
serverAssert(vptr != NULL);
/* update 设为1表示查找成功 */
update = 1;
/* Replace value */
/* 替换 value 为所要设置的值 */
zl = lpReplace(zl, &vptr, (unsigned char*)value, sdslen(value));
}
}
/* 查找失败 */
if (!update) {
/* Push new field/value pair onto the tail of the listpack */
/* 在 listpack 尾部追加 field-value */
zl = lpAppend(zl, (unsigned char*)field, sdslen(field));
zl = lpAppend(zl, (unsigned char*)value, sdslen(value));
}
o->ptr = zl;
/* Check if the listpack needs to be converted to a hash table */
/* entry 数量超过限制的最大值，哈希编码类型需要转换为 hashtable */
if (hashTypeLength(o) > server.hash_max_listpack_entries)
hashTypeConvert(o, OBJ_ENCODING_HT);
/* 哈希编码类型为 hashtable */
} else if (o->encoding == OBJ_ENCODING_HT) {
dictEntry *de = dictFind(o->ptr,field);
/* 查找成功 */
if (de) {
/* 先将 dictEntry 中原来的 value 释放 */
sdsfree(dictGetVal(de));
/* 设置了 HASH_SET_TAKE_VALUE 标志的情况下，直接让 dictEntry 的 val 引用这个 value，
* 并让 value = NULL ，即不再引用任何地方 */
if (flags & HASH_SET_TAKE_VALUE) {
dictGetVal(de) = value;
value = NULL;
} else {
/* 没有设置 HASH_SET_TAKE_VALUE 标志，我们复制一个 value 并让 dicrEntry 引用这个副本 */
dictGetVal(de) = sdsdup(value);
}
update = 1;
/* 查找失败，设置 field, value 具体过程与上方查找成功类似 */
} 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. */
/* 如果有把所有权交给函数的标志，释放我们没有在引用其他地方的 SDS 字符串 */
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. */
/* 从哈希类型对象中删除一个元素，返回1表示被删除，返回0表示未找到 */
int hashTypeDelete(robj *o, sds field) {
int deleted = 0;
if (o->encoding == OBJ_ENCODING_LISTPACK) {
unsigned char *zl, *fptr;
zl = o->ptr;
fptr = lpFirst(zl);
if (fptr != NULL) {
fptr = lpFind(zl, fptr, (unsigned char*)field, sdslen(field), 1);
if (fptr != NULL) {
/* Delete both of the key and the value. */
/* 将 field 和 value 一并删除 */
zl = lpDeleteRangeWithEntry(zl,&fptr,2);
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. */
/* 检查删除元素后是否需要重新分配哈希表的内存空间 */
if (htNeedsResize(o->ptr)) dictResize(o->ptr);
}
} else {
serverPanic("Unknown hash encoding");
}
return deleted;
}
/* Return the number of elements in a hash. */
/* 返回哈希类型对象中的元素数量 */
unsigned long hashTypeLength(const robj *o) {
unsigned long length = ULONG_MAX;
if (o->encoding == OBJ_ENCODING_LISTPACK) {
/* field-value 对为一个元素，所以元素数量是 listpack 的 entry 数量除以2 */
length = lpLength(o->ptr) / 2;
} else if (o->encoding == OBJ_ENCODING_HT) {
/* redis 的哈希表是渐进式 rehash 的，所以 dict 中有一新一旧的两个哈希表，
* 所以 dictSize 计算元素数量方法是将两个哈希表的元素数量相加 */
length = dictSize((const dict*)o->ptr);
} else {
serverPanic("Unknown hash encoding");
}
return length;
}
/* 哈希类型对象迭代器的初始化函数 */
hashTypeIterator *hashTypeInitIterator(robj *subject) {
hashTypeIterator *hi = zmalloc(sizeof(hashTypeIterator));
hi->subject = subject;
hi->encoding = subject->encoding;
if (hi->encoding == OBJ_ENCODING_LISTPACK) {
hi->fptr = NULL;
hi->vptr = NULL;
} else if (hi->encoding == OBJ_ENCODING_HT) {
hi->di = dictGetIterator(subject->ptr);
} else {
serverPanic("Unknown hash encoding");
}
return hi;
}
/* 释放哈希类型对象迭代器 */
void hashTypeReleaseIterator(hashTypeIterator *hi) {
if (hi->encoding == OBJ_ENCODING_HT)
dictReleaseIterator(hi->di);
zfree(hi);
}
/* Move to the next entry in the hash. Return C_OK when the next entry
* could be found and C_ERR when the iterator reaches the end. */
/* 移动到哈希表的下一个 entry。当找到下一个 entry 时返回 C_OK，当迭代器到达终点时返回 C_ERR */
int hashTypeNext(hashTypeIterator *hi) {
/* 编码类型为 listpack */
if (hi->encoding == OBJ_ENCODING_LISTPACK) {
unsigned char *zl;
unsigned char *fptr, *vptr;
zl = hi->subject->ptr;
fptr = hi->fptr;
vptr = hi->vptr;
if (fptr == NULL) {
/* Initialize cursor */
/* 初始化游标，即令 fptr 等于 listpack 的第一个 entry */
serverAssert(vptr == NULL);
fptr = lpFirst(zl);
} else {
/* Advance cursor */
/* 游标前进，即令 fptr 等于 vptr 的下一个 entry */
serverAssert(vptr != NULL);
fptr = lpNext(zl, vptr);
}
/* 如果到这 fptr 仍为空，则 fptr 指向了终点，返回 C_ERR */
if (fptr == NULL) return C_ERR;
/* Grab pointer to the value (fptr points to the field) */
/* vptr 指向 fptr 下一个节点，即指向了 field 对应的 value */
vptr = lpNext(zl, fptr);
serverAssert(vptr != NULL);
/* fptr, vptr now point to the first or next pair */
/* 改变迭代器中的 fptr 和 vptr */
hi->fptr = fptr;
hi->vptr = vptr;
/* 编码类型为 hashtable */
} else if (hi->encoding == OBJ_ENCODING_HT) {
if ((hi->de = dictNext(hi->di)) == NULL) return C_ERR;
} else {
serverPanic("Unknown hash encoding");
}
return C_OK;
}
/* Get the field or value at iterator cursor, for an iterator on a hash value
* encoded as a listpack. Prototype is similar to `hashTypeGetFromListpack`. */
/* 在迭代器游标处获取 field 或 value ,哈希类型为 listpack 时使用*/
void hashTypeCurrentFromListpack(hashTypeIterator *hi, int what,
unsigned char **vstr,
unsigned int *vlen,
long long *vll)
{
serverAssert(hi->encoding == OBJ_ENCODING_LISTPACK);
/* what & OBJ_HASH_KEY == true ,则取出 field ，否则取出 value */
if (what & OBJ_HASH_KEY) {
*vstr = lpGetValue(hi->fptr, vlen, vll);
} else {
*vstr = lpGetValue(hi->vptr, vlen, vll);
}
}
/* Get the field or value at iterator cursor, for an iterator on a hash value
* encoded as a hash table. Prototype is similar to
* `hashTypeGetFromHashTable`. */
/* 在迭代器游标处获取 field 或 value ,哈希类型为 hashtable 时使用*/
sds hashTypeCurrentFromHashTable(hashTypeIterator *hi, int what) {
serverAssert(hi->encoding == OBJ_ENCODING_HT);
if (what & OBJ_HASH_KEY) {
return dictGetKey(hi->de);
} else {
return dictGetVal(hi->de);
}
}
/* Higher level function of hashTypeCurrent*() that returns the hash value
* at current iterator position.
*
* The returned element is returned by reference in either *vstr and *vlen if
* it's returned in string form, or stored in *vll if it's returned as
* a number.
*
* If *vll is populated *vstr is set to NULL, so the caller
* can always check the function return by checking the return value
* type checking if vstr == NULL. */
/* hashTypeCurrent*()的高级函数，是返回当前哈希迭代器位置的元素
* 如果它返回的元素是字符串类型的，则既填充 *vstr 又填充 *vlen ，如果它返回的是整数类型的，则只填充 *vil
* 那么调用方始终可以通过检查 vstr 是否为空的方法，来得知元素被保存在了哪个变量中 */
void hashTypeCurrentObject(hashTypeIterator *hi, int what, unsigned char **vstr, unsigned int *vlen, long long *vll) {
/* 根据编码类型，调用不同的函数获取值 */
if (hi->encoding == OBJ_ENCODING_LISTPACK) {
*vstr = NULL;
hashTypeCurrentFromListpack(hi, what, vstr, vlen, vll);
} else if (hi->encoding == OBJ_ENCODING_HT) {
sds ele = hashTypeCurrentFromHashTable(hi, what);
*vstr = (unsigned char*) ele;
*vlen = sdslen(ele);
} else {
serverPanic("Unknown hash encoding");
}
}
/* Return the key or value at the current iterator position as a new
* SDS string. */
/* 返回当前迭代器位置的 key 或 value ，返回的是一个新创建的 SDS 字符串(或者说副本) */
sds hashTypeCurrentObjectNewSds(hashTypeIterator *hi, int what) {
unsigned char *vstr;
unsigned int vlen;
long long vll;
hashTypeCurrentObject(hi,what,&vstr,&vlen,&vll);
if (vstr) return sdsnewlen(vstr,vlen);
return sdsfromlonglong(vll);
}
/* 在写模式下查找key，如果查找不到则创建该key */
robj *hashTypeLookupWriteOrCreate(client *c, robj *key) {
robj *o = lookupKeyWrite(c->db,key);
if (checkType(c,o,OBJ_HASH)) return NULL;
if (o == NULL) {
o = createHashObject();
dbAdd(c->db,key,o);
}
return o;
}
/* 将哈希编码类型从 listpack 转化为 hashtable */
void hashTypeConvertListpack(robj *o, int enc) {
serverAssert(o->encoding == OBJ_ENCODING_LISTPACK);
/* enc 指定了转化类型，如果转化类型为 listpack 则什么也不做 */
if (enc == OBJ_ENCODING_LISTPACK) {
/* Nothing to do... */
} else if (enc == OBJ_ENCODING_HT) {
hashTypeIterator *hi;
dict *dict;
int ret;
/* 初始化迭代器 hi 和字典(哈希表) dict */
hi = hashTypeInitIterator(o);
dict = dictCreate(&hashDictType);
/* Presize the dict to avoid rehashing */
/* 预分配内存空间，避免rehashing重新分配空间导致性能下降 */
dictExpand(dict,hashTypeLength(o));
/* 利用迭代器遍历 listpack */
while (hashTypeNext(hi) != C_ERR) {
sds key, value;
/* 取出迭代器当前游标下的 key 和 value */
key = hashTypeCurrentObjectNewSds(hi,OBJ_HASH_KEY);
value = hashTypeCurrentObjectNewSds(hi,OBJ_HASH_VALUE);
/* 将 key 和 value 加入 dict */
ret = dictAdd(dict, key, value);
/* key 和 value 添加到 dict 失败，释放 key, value, hi ，并向服务器报错 */
if (ret != DICT_OK) {
sdsfree(key); sdsfree(value); /* Needed for gcc ASAN */
hashTypeReleaseIterator(hi); /* Needed for gcc ASAN */
serverLogHexDump(LL_WARNING,"listpack with dup elements dump",
o->ptr,lpBytes(o->ptr));
serverPanic("Listpack corruption detected");
}
}
/* 释放迭代器内存空间 */
hashTypeReleaseIterator(hi);
/* 释放原来的 listpack */
zfree(o->ptr);
/* 修改 o 的编码类型标识为 hashtable */
o->encoding = OBJ_ENCODING_HT;
/* 修改 o 的 ptr 指针指向 dict */
o->ptr = dict;
} else {
serverPanic("Unknown hash encoding");
}
}
/* 哈希编码类型转换 */
void hashTypeConvert(robj *o, int enc) {
if (o->encoding == OBJ_ENCODING_LISTPACK) {
hashTypeConvertListpack(o, enc);
} else if (o->encoding == OBJ_ENCODING_HT) {
serverPanic("Not implemented");
} else {
serverPanic("Unknown hash encoding");
}
}
/* This is a helper function for the COPY command.
* Duplicate a hash object, with the guarantee that the returned object
* has the same encoding as the original one.
*
* The resulting object always has refcount set to 1 */
/* 这是一个用于 COPY 命令的辅助函数。
* 复制一个哈希对象，并保证返回的对象具有与原始对象相同的编码。
* 返回的对象总是将 refcount(被引用次数) 设置为1 */
robj *hashTypeDup(robj *o) {
robj *hobj;
hashTypeIterator *hi;
serverAssert(o->type == OBJ_HASH);
if(o->encoding == OBJ_ENCODING_LISTPACK) {
unsigned char *zl = o->ptr;
size_t sz = lpBytes(zl);
/* 为副本开辟内存空间 */
unsigned char *new_zl = zmalloc(sz);
/* 复制原来的 listpack */
memcpy(new_zl, zl, sz);
/* 创建新的哈希类型对象，并设置编码类型标识为 listpack */
hobj = createObject(OBJ_HASH, new_zl);
hobj->encoding = OBJ_ENCODING_LISTPACK;
} else if(o->encoding == OBJ_ENCODING_HT){
/* 创建副本的字典(哈希表) dict 并预分配空间 */
dict *d = dictCreate(&hashDictType);
dictExpand(d, dictSize((const dict*)o->ptr));
hi = hashTypeInitIterator(o);
/* 利用迭代器遍历源 hashtable */
while (hashTypeNext(hi) != C_ERR) {
sds field, value;
sds newfield, newvalue;
/* Extract a field-value pair from an original hash object.*/
/* 从原哈希对象中提取一对 field-value */
field = hashTypeCurrentFromHashTable(hi, OBJ_HASH_KEY);
value = hashTypeCurrentFromHashTable(hi, OBJ_HASH_VALUE);
/* 对 field, value 进行复制 */
newfield = sdsdup(field);
newvalue = sdsdup(value);
/* Add a field-value pair to a new hash object. */
/* 将 field-value 加入到新哈希对象中 */
dictAdd(d,newfield,newvalue);
}
hashTypeReleaseIterator(hi);
/* 创建新的哈希类型对象，并设置编码类型标识为 hashtable */
hobj = createObject(OBJ_HASH, d);
hobj->encoding = OBJ_ENCODING_HT;
} else {
serverPanic("Unknown hash encoding");
}
return hobj;
}
/* Create a new sds string from the listpack entry. */
/* 获取参数给定的 listpack 的 entry 中的值 ，并返回一个以该值创建的 sds 字符串 */
sds hashSdsFromListpackEntry(listpackEntry *e) {
return e->sval ? sdsnewlen(e->sval, e->slen) : sdsfromlonglong(e->lval);
}
/* Reply with bulk string from the listpack entry. */
/* 将参数给定的 listpack 的 entry 中的值回复给客户端 */
void hashReplyFromListpackEntry(client *c, listpackEntry *e) {
if (e->sval)
addReplyBulkCBuffer(c, e->sval, e->slen);
else
addReplyBulkLongLong(c, e->lval);
}
/* Return random element from a non empty hash.
* 'key' and 'val' will be set to hold the element.
* The memory in them is not to be freed or modified by the caller.
* 'val' can be NULL in which case it's not extracted. */
/* 从一个非空哈希类型对象中返回随机元素
* 'key' 和 'val' 将持有该元素
* 它们的内存不能被释放或被调用者修改。
* 'val' 可以是 NULL，在这种情况下它不会被进行赋值 */
void hashTypeRandomElement(robj *hashobj, unsigned long hashsize, listpackEntry *key, listpackEntry *val) {
if (hashobj->encoding == OBJ_ENCODING_HT) {
/* 调用 dictGetFairRandomKey 随机获取一个 dictEntry */
dictEntry *de = dictGetFairRandomKey(hashobj->ptr);
sds s = dictGetKey(de);
key->sval = (unsigned char*)s;
key->slen = sdslen(s);
/* val 不为 NULL, 要求获取 value */
if (val) {
sds s = dictGetVal(de);
val->sval = (unsigned char*)s;
val->slen = sdslen(s);
}
} else if (hashobj->encoding == OBJ_ENCODING_LISTPACK) {
/* 调用 lpRandomPair 随机获取一个 field 或 field-value (若 val 不为 NULL) */
lpRandomPair(hashobj->ptr, hashsize, key, val);
} else {
serverPanic("Unknown hash encoding");
}
}
/*-----------------------------------------------------------------------------
* Hash type commands
*----------------------------------------------------------------------------*/
/* 处理hsetnx命令的函数 */
void hsetnxCommand(client *c) {
robj *o;
/* 查找 key */
if ((o = hashTypeLookupWriteOrCreate(c,c->argv[1])) == NULL) return;
/* key 已存在，向客户端回复0 */
if (hashTypeExists(o, c->argv[2]->ptr)) {
addReply(c, shared.czero);
} else {
/* 尝试哈希编码类型转换(该函数仅判断输入 field 和 value 长度是否大于限制) */
hashTypeTryConversion(o,c->argv,2,3);
/* 设置 field-value */
hashTypeSet(o,c->argv[2]->ptr,c->argv[3]->ptr,HASH_SET_COPY);
/* 向客户端回复1 */
addReply(c, shared.cone);
/* 发送数据库被修改的通知 */
signalModifiedKey(c,c->db,c->argv[1]);
/* 发送事件通知 */
notifyKeyspaceEvent(NOTIFY_HASH,"hset",c->argv[1],c->db->id);
/* 距离上次成功保存的数据变动次数 + 1 */
server.dirty++;
}
}
/* 处理hset命令的函数 */
void hsetCommand(client *c) {
int i, created = 0;
robj *o;
/* 该命令输入参数个数必为偶数，若为奇数则输入有误，将导致报错并返回 */
if ((c->argc % 2) == 1) {
addReplyErrorArity(c);
return;
}
/* 查找key */
if ((o = hashTypeLookupWriteOrCreate(c,c->argv[1])) == NULL) return;
hashTypeTryConversion(o,c->argv,2,c->argc-1);
/* 解析输入的 field value 参数 */
for (i = 2; i < c->argc; i += 2)
/* 设置 field-value ，同时给记录新创建的 field-value 数量的变量 created 计数
* 若 field-value 是新建的 hashTypeSet 返回0，所以需要前面加上 '!' 逻辑非符号转化为1 */
created += !hashTypeSet(o,c->argv[i]->ptr,c->argv[i+1]->ptr,HASH_SET_COPY);
/* HMSET (deprecated) and HSET return value is different. */
/* HMSET 命令 (不推荐使用，已过时，可被HSET替代) 和 HSET 命令的返回值不相同 */
char *cmdname = c->argv[0]->ptr;
if (cmdname[1] == 's' || cmdname[1] == 'S') {
/* HSET */
/* HSET 返回值为新的 field-value 个数 */
addReplyLongLong(c, created);
} else {
/* HMSET */
/* HMSET 返回值为 'OK' */
addReply(c, shared.ok);
}
signalModifiedKey(c,c->db,c->argv[1]);
notifyKeyspaceEvent(NOTIFY_HASH,"hset",c->argv[1],c->db->id);
server.dirty += (c->argc - 2)/2;
}
/* 处理hincrby命令的函数 */
void hincrbyCommand(client *c) {
long long value, incr, oldvalue;
robj *o;
sds new;
unsigned char *vstr;
unsigned int vlen;
/* 取出输入参数 increment 并赋值给 incr */
if (getLongLongFromObjectOrReply(c,c->argv[3],&incr,NULL) != C_OK) return;
if ((o = hashTypeLookupWriteOrCreate(c,c->argv[1])) == NULL) return;
/* 取出哈希对象的 value */
if (hashTypeGetValue(o,c->argv[2]->ptr,&vstr,&vlen,&value) == C_OK) {
if (vstr) {
/* 将哈希对象的 value 转换为 long long 并赋值给 value */
if (string2ll((char*)vstr,vlen,&value) == 0) {
/* value 无法转换，报错并返回 */
addReplyError(c,"hash value is not an integer");
return;
}
} /* Else hashTypeGetValue() already stored it into &value */
} else {
/* 哈希对象不存在，value 设置为默认值0 */
value = 0;
}
oldvalue = value;
/* 检查原 value 加上 incr 是否会溢出 */
if ((incr < 0 && oldvalue < 0 && incr < (LLONG_MIN-oldvalue)) ||
(incr > 0 && oldvalue > 0 && incr > (LLONG_MAX-oldvalue))) {
addReplyError(c,"increment or decrement would overflow");
return;
}
/* value 加上 incr */
value += incr;
/* new 是以 value 的值创建而来的字符串 */
new = sdsfromlonglong(value);
hashTypeSet(o,c->argv[2]->ptr,new,HASH_SET_TAKE_VALUE);
addReplyLongLong(c,value);
signalModifiedKey(c,c->db,c->argv[1]);
notifyKeyspaceEvent(NOTIFY_HASH,"hincrby",c->argv[1],c->db->id);
server.dirty++;
}
/* 处理 hincrbyfloat 命令的函数，具体实现与 hincrby 类似 */
void hincrbyfloatCommand(client *c) {
long double value, incr;
long long ll;
robj *o;
sds new;
unsigned char *vstr;
unsigned int vlen;
if (getLongDoubleFromObjectOrReply(c,c->argv[3],&incr,NULL) != C_OK) return;
if ((o = hashTypeLookupWriteOrCreate(c,c->argv[1])) == NULL) return;
if (hashTypeGetValue(o,c->argv[2]->ptr,&vstr,&vlen,&ll) == C_OK) {
if (vstr) {
if (string2ld((char*)vstr,vlen,&value) == 0) {
addReplyError(c,"hash value is not a float");
return;
}
} else {
value = (long double)ll;
}
} else {
value = 0;
}
value += incr;
if (isnan(value) || isinf(value)) {
addReplyError(c,"increment would produce NaN or Infinity");
return;
}
char buf[MAX_LONG_DOUBLE_CHARS];
int len = ld2string(buf,sizeof(buf),value,LD_STR_HUMAN);
new = sdsnewlen(buf,len);
hashTypeSet(o,c->argv[2]->ptr,new,HASH_SET_TAKE_VALUE);
addReplyBulkCBuffer(c,buf,len);
signalModifiedKey(c,c->db,c->argv[1]);
notifyKeyspaceEvent(NOTIFY_HASH,"hincrbyfloat",c->argv[1],c->db->id);
server.dirty++;
/* Always replicate HINCRBYFLOAT as an HSET command with the final value
* in order to make sure that differences in float precision or formatting
* will not create differences in replicas or after an AOF restart. */
/* 始终将 HINCRBYFLOAT 作为 HSET 命令进行复制，
* 以确保浮点数精度或格式化的差异不会在复制中或AOF重启后产生差异 */
robj *newobj;
newobj = createRawStringObject(buf,len);
rewriteClientCommandArgument(c,0,shared.hset);
rewriteClientCommandArgument(c,3,newobj);
decrRefCount(newobj);
}
/* 查找指定的 field-value 并将 value 回复给客户端 */
static void addHashFieldToReply(client *c, robj *o, sds field) {
if (o == NULL) {
addReplyNull(c);
return;
}
unsigned char *vstr = NULL;
unsigned int vlen = UINT_MAX;
long long vll = LLONG_MAX;
if (hashTypeGetValue(o, field, &vstr, &vlen, &vll) == C_OK) {
if (vstr) {
addReplyBulkCBuffer(c, vstr, vlen);
} else {
addReplyBulkLongLong(c, vll);
}
} else {
addReplyNull(c);
}
}
/* 处理 hget 命令的函数 */
void hgetCommand(client *c) {
robj *o;
/* 查找 key 对应的 redis 对象 ，找到后检查对象类型是否为 hashtable */
if ((o = lookupKeyReadOrReply(c,c->argv[1],shared.null[c->resp])) == NULL ||
checkType(c,o,OBJ_HASH)) return;
/* 调用 addHashFieldToReply 进行查找与回复 value 给客户端 */
addHashFieldToReply(c, o, c->argv[2]->ptr);
}
/* 处理 hmget 命令的函数 */
void hmgetCommand(client *c) {
robj *o;
int i;
/* Don't abort when the key cannot be found. Non-existing keys are empty
* hashes, where HMGET should respond with a series of null bulks. */
/* 当找不到 key 的时候不要中止，不存在的 key 即空哈希对象 ，HMGET 应该用空值来回应 */
o = lookupKeyRead(c->db, c->argv[1]);
if (checkType(c,o,OBJ_HASH)) return;
/* 将以列表的形式回复客户端，这里设置列表的长度 */
addReplyArrayLen(c, c->argc-2);
/* 解析输入的 field 和 value 参数，并调用 addHashFieldToReply 进行查找与回复 value 给客户端 */
for (i = 2; i < c->argc; i++) {
addHashFieldToReply(c, o, c->argv[i]->ptr);
}
}
/* 处理 hdel 命令的函数 */
void hdelCommand(client *c) {
robj *o;
int j, deleted = 0, keyremoved = 0;