redis intset整数集合ソース分析
9795 ワード
//
typedef struct intset {
//
uint32_t encoding;
// , , contents
uint32_t length;
//
int8_t contents[];
} intset;
#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. */
// v
static uint8_t _intsetValueEncoding(int64_t v) {
// 32 , 64
if (v < INT32_MIN || v > INT32_MAX)
return INTSET_ENC_INT64;
// 16 , 16 32 32
else if (v < INT16_MIN || v > INT16_MAX)
return INTSET_ENC_INT32;
// 16
else
return INTSET_ENC_INT16;
}
/* Return the value at pos, given an encoding. */
// , pos
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. */
// pos
static int64_t _intsetGet(intset *is, int pos) {
return _intsetGetEncoded(is,pos,intrev32ifbe(is->encoding));
}
/* Set the value at pos, using the configured encoding. */
// , pos
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. */
//
intset *intsetNew(void) {
intset *is = zmalloc(sizeof(intset));
// int16_t
is->encoding = intrev32ifbe(INTSET_ENC_INT16);
// 0
is->length = 0;
return is;
}
/* Resize the intset */
//
// , length, length
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. */
// value pos
// value , 0
// value , 1
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) {
// index 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,intrev32ifbe(is->length)-1)) {
// index
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 {
// mid value
break;
}
}
if (value == cur) {
if (pos) *pos = mid;
return 1;
} else {
if (pos) *pos = min;
return 0;
}
}
/* 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;
}
// from to
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); // src bytes dst
}
/* Insert an integer in the intset */
// value, success , 1 , 0
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. */
// 1, , ,
if (intsetSearch(is,value,&pos)) {
if (success) *success = 0;
return is;
}
//
is = intsetResize(is,intrev32ifbe(is->length)+1);
// ,
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;
//
// , 1.pos
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);
}
//
return is;
}
/* Determine whether a value belongs to this set */
// value
// 1 , 0
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));
}
/* Sets the value to the value at the given position. When this position is
* out of range the function returns 0, when in range it returns 1. */
// intset pos , 1
// ( ) 0
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 */
// intset
uint32_t intsetLen(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);
}