redis源码5 intset
intset数据结构
typedef struct intset {
uint32_t encoding; // 编码模式
uint32_t length; // 长度
int8_t contents[]; // 数据部分
} intset;_intsetValueEncoding
根据数值获取长度类型
static uint8_t _intsetValueEncoding(int64_t v) {
if (v < INT32_MIN || v > INT32_MAX)
return INTSET_ENC_INT64;
else if (v < INT16_MIN || v > INT16_MAX)
return INTSET_ENC_INT32;
else
return INTSET_ENC_INT16;
}大小端转换
因为不同CPU的数值存储方式可能存在不同，具体的可分为大端存储和小端存储，即倒放与正放所以redis得根据当前cpu的架构来决定怎么安放数字。
_intsetGetEncoded
根据编码取值
static int64_t _intsetGetEncoded(intset *is, int pos, uint8_t enc) {
int64_t v64;
int32_t v32;
int16_t v16;
if (enc == INTSET_ENC_INT64) {
memcpy(&v64,((int64_t*)is->contents)+pos,sizeof(v64));
memrev64ifbe(&v64);//大小端转换
return v64;
} else if (enc == INTSET_ENC_INT32) {
memcpy(&v32,((int32_t*)is->contents)+pos,sizeof(v32));
memrev32ifbe(&v32);//大小端转换
return v32;
} else {
memcpy(&v16,((int16_t*)is->contents)+pos,sizeof(v16));
memrev16ifbe(&v16);//大小端转换
return v16;
}
}根据intset编码来获取内容
static int64_t _intsetGet(intset *is, int pos) {
return _intsetGetEncoded(is,pos,intrev32ifbe(is->encoding));
}intsetNew&intsetResize
创建新的intset和根据大小复制新的intset
/* Create an empty intset. */
intset *intsetNew(void) {
intset *is = zmalloc(sizeof(intset));
is->encoding = intrev32ifbe(INTSET_ENC_INT16);
is->length = 0;
return is;
}
/* Resize the intset */
static intset *intsetResize(intset *is, uint32_t len) {
uint32_t size = len*intrev32ifbe(is->encoding);
is = zrealloc(is,sizeof(intset)+size);
return is;
}intsetSearch
二分查找
static uint8_t intsetSearch(intset *is, int64_t value, uint32_t *pos) {
int min = 0, max = intrev32ifbe(is->length)-1, mid = -1;
int64_t cur = -1;
/* The value can never be found when the set is empty */
if (intrev32ifbe(is->length) == 0) {
if (pos) *pos = 0;
return 0;
} else {
/* Check for the case where we know we cannot find the value,
* but do know the insert position. */
if (value > _intsetGet(is,max)) {
if (pos) *pos = intrev32ifbe(is->length);
return 0;
} else if (value < _intsetGet(is,0)) {
if (pos) *pos = 0;
return 0;
}
}
while(max >= min) {
mid = ((unsigned int)min + (unsigned int)max) >> 1;
cur = _intsetGet(is,mid);
if (value > cur) {
min = mid+1;
} else if (value < cur) {
max = mid-1;
} else {
break;
}
}
if (value == cur) {
if (pos) *pos = mid;
return 1;
} else {
if (pos) *pos = min;
return 0;
}
}intsetUpgradeAndAdd
扩容且插入新值
/* Upgrades the intset to a larger encoding and inserts the given integer. */
static intset *intsetUpgradeAndAdd(intset *is, int64_t value) {
uint8_t curenc = intrev32ifbe(is->encoding);
uint8_t newenc = _intsetValueEncoding(value);
int length = intrev32ifbe(is->length);
int prepend = value < 0 ? 1 : 0;
/* First set new encoding and resize */
is->encoding = intrev32ifbe(newenc);
is = intsetResize(is,intrev32ifbe(is->length)+1);
/* Upgrade back-to-front so we don't overwrite values.
* Note that the "prepend" variable is used to make sure we have an empty
* space at either the beginning or the end of the intset. */
while(length--)
_intsetSet(is,length+prepend,_intsetGetEncoded(is,length,curenc));
/* Set the value at the beginning or the end. */
if (prepend)
_intsetSet(is,0,value);
else
_intsetSet(is,intrev32ifbe(is->length),value);
is->length = intrev32ifbe(intrev32ifbe(is->length)+1);
return is;
}intsetAdd
像集合增加内容
intset *intsetAdd(intset *is, int64_t value, uint8_t *success) {
uint8_t valenc = _intsetValueEncoding(value);
uint32_t pos;
if (success) *success = 1;
/* Upgrade encoding if necessary. If we need to upgrade, we know that
* this value should be either appended (if > 0) or prepended (if < 0),
* because it lies outside the range of existing values. */
if (valenc > intrev32ifbe(is->encoding)) { //当前值大于编码 则需要扩容
/* This always succeeds, so we don't need to curry *success. */
return intsetUpgradeAndAdd(is,value); //扩容且设置值
} else {
/* Abort if the value is already present in the set.
* This call will populate "pos" with the right position to insert
* the value when it cannot be found. */
if (intsetSearch(is,value,&pos)) { //二分查找找到值对应的pos位置
if (success) *success = 0;
return is;
}
is = intsetResize(is,intrev32ifbe(is->length)+1); //扩容
if (pos < intrev32ifbe(is->length)) //如果pos小于当前编码则都往后挪 intsetMoveTail(is,pos,pos+1);
}
_intsetSet(is,pos,value);//设置值
is->length = intrev32ifbe(intrev32ifbe(is->length)+1); //长度
return is;
}intsetRemove
在intset里删除指定值
intset *intsetRemove(intset *is, int64_t value, int *success) {
uint8_t valenc = _intsetValueEncoding(value);
uint32_t pos;
if (success) *success = 0;
if (valenc <= intrev32ifbe(is->encoding) && intsetSearch(is,value,&pos)) { //值小于编码 且 值找得到
uint32_t len = intrev32ifbe(is->length);
/* We know we can delete */
if (success) *success = 1; //设置了success指针则赋值
/* Overwrite value with tail and update length */
if (pos < (len-1)) intsetMoveTail(is,pos+1,pos); //复制
is = intsetResize(is,len-1); //重构大小
is->length = intrev32ifbe(len-1);
}
return is;
}
