redis4.0_intset源码剖析

1.intset概述

intset(整数集合)可以用于保存类型为int16_t, int32_t, int64_t的整数值,并且保证intset中不会出现重复元素。

2.intst结构体

  • 表示intset的结构体定义如下:

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    typedef struct intset {
    //intset的编码方式:int*_t
    uint32_t encoding;
    //intset中元素的数量
    uint32_t length;
    //用于保存元素的数组(0长度数组的妙用)
    int8_t contents[];
    } intset;
  • intset对应的图示如下

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    |----------|
    | encoding |
    |----------|
    | length |
    |----------|
    |int*_t v0 |
    |----------|
    |int*_t v1 |
    |----------|
    |int*_t |
    |vlength-1 |
    |----------|

3.intset源码

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/*
* Copyright (c) 2009-2012, Pieter Noordhuis <pcnoordhuis at gmail dot com>
* 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 <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "intset.h"
#include "zmalloc.h"
#include "endianconv.h"
/* Note that these encodings are ordered, so:
* INTSET_ENC_INT16 < INTSET_ENC_INT32 < INTSET_ENC_INT64. */
#define INTSET_ENC_INT16 (sizeof(int16_t))
#define INTSET_ENC_INT32 (sizeof(int32_t))
#define INTSET_ENC_INT64 (sizeof(int64_t))
/* Return the required encoding for the provided value. */
//获取v对应的encoding
static uint8_t _intsetValueEncoding(int64_t v) {
//INT32_MAX=2^31-1 INT_32_MIN=-2^31
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;
}
/* Return the value at pos, given an encoding. */
//返回(int*_t)is->content[pos]的值
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);
return v64;
} else if (enc == INTSET_ENC_INT32) {
memcpy(&v32,((int32_t*)is->contents)+pos,sizeof(v32));
memrev32ifbe(&v32);
return v32;
} else {
memcpy(&v16,((int16_t*)is->contents)+pos,sizeof(v16));
memrev16ifbe(&v16);
return v16;
}
}
/* Return the value at pos, using the configured encoding. */
static int64_t _intsetGet(intset *is, int pos) {
return _intsetGetEncoded(is,pos,intrev32ifbe(is->encoding));
}
/* Set the value at pos, using the configured encoding. */
static void _intsetSet(intset *is, int pos, int64_t value) {
uint32_t encoding = intrev32ifbe(is->encoding);
if (encoding == INTSET_ENC_INT64) {
((int64_t*)is->contents)[pos] = value;
memrev64ifbe(((int64_t*)is->contents)+pos);
} else if (encoding == INTSET_ENC_INT32) {
((int32_t*)is->contents)[pos] = value;
memrev32ifbe(((int32_t*)is->contents)+pos);
} else {
((int16_t*)is->contents)[pos] = value;
memrev16ifbe(((int16_t*)is->contents)+pos);
}
}
/* Create an empty intset. */
//创建一个空的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;
}
/* Search for the position of "value". Return 1 when the value was found and
* sets "pos" to the position of the value within the intset. Return 0 when
* the value is not present in the intset and sets "pos" to the position
* where "value" can be inserted. */
//返回值为1:intset中含有该value, *pos为inset content中该value的偏移量
//返回值为0:intset中不含有该value, *pos为inset content中插入该value的偏移量
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. */
//获得intset最后一个元素的值,如果value大于最后一个元素,则value插入intset末尾
if (value > _intsetGet(is,intrev32ifbe(is->length)-1)) {
if (pos) *pos = intrev32ifbe(is->length);
return 0;
} else if (value < _intsetGet(is,0)) {
if (pos) *pos = 0;
return 0;
}
}
//二分查找
while(max >= min) {
//mid=((unsigned)min + (unsigned)max)/2;
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 {
//value==cur
break;
}
}
if (value == cur) {
if (pos) *pos = mid;
return 1;
} else {
//待插入元素的位置
if (pos) *pos = min;
return 0;
}
}
/* Upgrades the intset to a larger encoding and inserts the given integer. */
//升级intset的encoding
static intset *intsetUpgradeAndAdd(intset *is, int64_t value) {
uint8_t curenc = intrev32ifbe(is->encoding);
uint8_t newenc = _intsetValueEncoding(value);
int length = intrev32ifbe(is->length);
//如果value<0则prepend
//如果value>=0,则append
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. */
//根据newenc,将原有intset的所有元素copy到new 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;
}
//将from之后的所有元素移动到to开头的地址
static void intsetMoveTail(intset *is, uint32_t from, uint32_t to) {
void *src, *dst;
uint32_t bytes = intrev32ifbe(is->length)-from;
uint32_t encoding = intrev32ifbe(is->encoding);
if (encoding == INTSET_ENC_INT64) {
src = (int64_t*)is->contents+from;
dst = (int64_t*)is->contents+to;
bytes *= sizeof(int64_t);
} else if (encoding == INTSET_ENC_INT32) {
src = (int32_t*)is->contents+from;
dst = (int32_t*)is->contents+to;
bytes *= sizeof(int32_t);
} else {
src = (int16_t*)is->contents+from;
dst = (int16_t*)is->contents+to;
bytes *= sizeof(int16_t);
}
memmove(dst,src,bytes);
}
/* Insert an integer in the intset */
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)) {
/* This always succeeds, so we don't need to curry *success. */
return intsetUpgradeAndAdd(is,value);
} 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)) {
//在intset中查找到value
if (success) *success = 0;
return is;
}
//intset中没有value,所以在pos位置插入value
is = intsetResize(is,intrev32ifbe(is->length)+1);
//将pos处的内存预留给value
if (pos < intrev32ifbe(is->length)) intsetMoveTail(is,pos,pos+1);
}
_intsetSet(is,pos,value);
is->length = intrev32ifbe(intrev32ifbe(is->length)+1);
return is;
}
/* Delete integer from intset */
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)) {
uint32_t len = intrev32ifbe(is->length);
/* We know we can delete */
if (success) *success = 1;
/* Overwrite value with tail and update length */
if (pos < (len-1)) intsetMoveTail(is,pos+1,pos);
is = intsetResize(is,len-1);
is->length = intrev32ifbe(len-1);
}
//else value不可能存在于该intset
return is;
}
/* Determine whether a value belongs to this set */
uint8_t intsetFind(intset *is, int64_t value) {
uint8_t valenc = _intsetValueEncoding(value);
return valenc <= intrev32ifbe(is->encoding) && intsetSearch(is,value,NULL);
}
/* Return random member */
int64_t intsetRandom(intset *is) {
return _intsetGet(is,rand()%intrev32ifbe(is->length));
}
/* Get the value at the given position. When this position is
* out of range the function returns 0, when in range it returns 1. */
uint8_t intsetGet(intset *is, uint32_t pos, int64_t *value) {
if (pos < intrev32ifbe(is->length)) {
*value = _intsetGet(is,pos);
return 1;
}
return 0;
}
/* Return intset length */
uint32_t intsetLen(const intset *is) {
return intrev32ifbe(is->length);
}
/* Return intset blob size in bytes. */
size_t intsetBlobLen(intset *is) {
return sizeof(intset)+intrev32ifbe(is->length)*intrev32ifbe(is->encoding);
}
#ifdef REDIS_TEST
#include <sys/time.h>
#include <time.h>
#if 0
static void intsetRepr(intset *is) {
for (uint32_t i = 0; i < intrev32ifbe(is->length); i++) {
printf("%lld\n", (uint64_t)_intsetGet(is,i));
}
printf("\n");
}
static void error(char *err) {
printf("%s\n", err);
exit(1);
}
#endif
static void ok(void) {
printf("OK\n");
}
static long long usec(void) {
struct timeval tv;
gettimeofday(&tv,NULL);
return (((long long)tv.tv_sec)*1000000)+tv.tv_usec;
}
#define assert(_e) ((_e)?(void)0:(_assert(#_e,__FILE__,__LINE__),exit(1)))
static void _assert(char *estr, char *file, int line) {
printf("\n\n=== ASSERTION FAILED ===\n");
printf("==> %s:%d '%s' is not true\n",file,line,estr);
}
static intset *createSet(int bits, int size) {
uint64_t mask = (1<<bits)-1;
uint64_t value;
intset *is = intsetNew();
for (int i = 0; i < size; i++) {
if (bits > 32) {
value = (rand()*rand()) & mask;
} else {
value = rand() & mask;
}
is = intsetAdd(is,value,NULL);
}
return is;
}
static void checkConsistency(intset *is) {
for (uint32_t i = 0; i < (intrev32ifbe(is->length)-1); i++) {
uint32_t encoding = intrev32ifbe(is->encoding);
if (encoding == INTSET_ENC_INT16) {
int16_t *i16 = (int16_t*)is->contents;
assert(i16[i] < i16[i+1]);
} else if (encoding == INTSET_ENC_INT32) {
int32_t *i32 = (int32_t*)is->contents;
assert(i32[i] < i32[i+1]);
} else {
int64_t *i64 = (int64_t*)is->contents;
assert(i64[i] < i64[i+1]);
}
}
}
#define UNUSED(x) (void)(x)
int intsetTest(int argc, char **argv) {
uint8_t success;
int i;
intset *is;
srand(time(NULL));
UNUSED(argc);
UNUSED(argv);
printf("Value encodings: "); {
assert(_intsetValueEncoding(-32768) == INTSET_ENC_INT16);
assert(_intsetValueEncoding(+32767) == INTSET_ENC_INT16);
assert(_intsetValueEncoding(-32769) == INTSET_ENC_INT32);
assert(_intsetValueEncoding(+32768) == INTSET_ENC_INT32);
assert(_intsetValueEncoding(-2147483648) == INTSET_ENC_INT32);
assert(_intsetValueEncoding(+2147483647) == INTSET_ENC_INT32);
assert(_intsetValueEncoding(-2147483649) == INTSET_ENC_INT64);
assert(_intsetValueEncoding(+2147483648) == INTSET_ENC_INT64);
assert(_intsetValueEncoding(-9223372036854775808ull) ==
INTSET_ENC_INT64);
assert(_intsetValueEncoding(+9223372036854775807ull) ==
INTSET_ENC_INT64);
ok();
}
printf("Basic adding: "); {
is = intsetNew();
is = intsetAdd(is,5,&success); assert(success);
is = intsetAdd(is,6,&success); assert(success);
is = intsetAdd(is,4,&success); assert(success);
is = intsetAdd(is,4,&success); assert(!success);
ok();
}
printf("Large number of random adds: "); {
uint32_t inserts = 0;
is = intsetNew();
for (i = 0; i < 1024; i++) {
is = intsetAdd(is,rand()%0x800,&success);
if (success) inserts++;
}
assert(intrev32ifbe(is->length) == inserts);
checkConsistency(is);
ok();
}
printf("Upgrade from int16 to int32: "); {
is = intsetNew();
is = intsetAdd(is,32,NULL);
assert(intrev32ifbe(is->encoding) == INTSET_ENC_INT16);
is = intsetAdd(is,65535,NULL);
assert(intrev32ifbe(is->encoding) == INTSET_ENC_INT32);
assert(intsetFind(is,32));
assert(intsetFind(is,65535));
checkConsistency(is);
is = intsetNew();
is = intsetAdd(is,32,NULL);
assert(intrev32ifbe(is->encoding) == INTSET_ENC_INT16);
is = intsetAdd(is,-65535,NULL);
assert(intrev32ifbe(is->encoding) == INTSET_ENC_INT32);
assert(intsetFind(is,32));
assert(intsetFind(is,-65535));
checkConsistency(is);
ok();
}
printf("Upgrade from int16 to int64: "); {
is = intsetNew();
is = intsetAdd(is,32,NULL);
assert(intrev32ifbe(is->encoding) == INTSET_ENC_INT16);
is = intsetAdd(is,4294967295,NULL);
assert(intrev32ifbe(is->encoding) == INTSET_ENC_INT64);
assert(intsetFind(is,32));
assert(intsetFind(is,4294967295));
checkConsistency(is);
is = intsetNew();
is = intsetAdd(is,32,NULL);
assert(intrev32ifbe(is->encoding) == INTSET_ENC_INT16);
is = intsetAdd(is,-4294967295,NULL);
assert(intrev32ifbe(is->encoding) == INTSET_ENC_INT64);
assert(intsetFind(is,32));
assert(intsetFind(is,-4294967295));
checkConsistency(is);
ok();
}
printf("Upgrade from int32 to int64: "); {
is = intsetNew();
is = intsetAdd(is,65535,NULL);
assert(intrev32ifbe(is->encoding) == INTSET_ENC_INT32);
is = intsetAdd(is,4294967295,NULL);
assert(intrev32ifbe(is->encoding) == INTSET_ENC_INT64);
assert(intsetFind(is,65535));
assert(intsetFind(is,4294967295));
checkConsistency(is);
is = intsetNew();
is = intsetAdd(is,65535,NULL);
assert(intrev32ifbe(is->encoding) == INTSET_ENC_INT32);
is = intsetAdd(is,-4294967295,NULL);
assert(intrev32ifbe(is->encoding) == INTSET_ENC_INT64);
assert(intsetFind(is,65535));
assert(intsetFind(is,-4294967295));
checkConsistency(is);
ok();
}
printf("Stress lookups: "); {
long num = 100000, size = 10000;
int i, bits = 20;
long long start;
is = createSet(bits,size);
checkConsistency(is);
start = usec();
for (i = 0; i < num; i++) intsetSearch(is,rand() % ((1<<bits)-1),NULL);
printf("%ld lookups, %ld element set, %lldusec\n",
num,size,usec()-start);
}
printf("Stress add+delete: "); {
int i, v1, v2;
is = intsetNew();
for (i = 0; i < 0xffff; i++) {
v1 = rand() % 0xfff;
is = intsetAdd(is,v1,NULL);
assert(intsetFind(is,v1));
v2 = rand() % 0xfff;
is = intsetRemove(is,v2,NULL);
assert(!intsetFind(is,v2));
}
checkConsistency(is);
ok();
}
return 0;
}
#endif

4.参考文献

redis_reading