int(nbuckets)) } else { //复用旧的内存 buckets = dirtyalloc size := t.Bucket.Size_ * nbuckets if t.Bucket.PtrBytes != 0 { memclrHasPointers(buckets, size) } else { memclrNoHeapPointers(buckets, size) } } if
count int // # live cells == size of map. Must be first (used by len() builtin) flags uint8 B uint8 // log_2 of # of buckets (can hold up to loadFactor * 2^B items) noverflow uint16 // approximate number of overflow buckets; see incrnoverflow for details hash0 uint32 //...
In computer science, an associative array, map, symbol table, or dictionary is an abstract data type composed of a collection of (key, value) pairs, such that each possible key appears at most once in the collection. 说明:在计算机科学中,包含键值对(key-value)集合的抽象数据结构(关联数组、符...
//typeas containing no pointers. This avoids scanning such maps. // However, bmap.overflow is a pointer. In order to keep overflow buckets // alive, we store pointers to all overflow bucketsinhmap.extra.overflow and hmap.extra.oldoverflow. // overflow and oldoverflow are only usedifkey an...
在开发过程中,map是必不可少的数据结构,在Golang中,使用map或多或少会遇到与其他语言不一样的体验,比如访问不存在的元素会返回其类型的空值、map的大小究竟是多少,为什么会报"cannot take the address of"错误,遍历map的随机性等等。 本文希望通过研究map的底层实现,以解答这些疑惑。
Golang - Map 内部实现原理解析 一.前言 Golang中Map存储的是kv键值对,采用哈希表作为底层实现,用拉链法解决hash冲突 本文Go版本:gov1.14.4,源码位于src/runtime/map.go 回到顶部 二.Map的内存模型 在源码中,表示map的结构体是hmap,是hashmap的缩写 ...
// 获取当前桶的溢出桶func(b*bmap)overflow(t*maptype)*bmap{return*(**bmap)(add(unsafe.Pointer(b),uintptr(t.bucketsize)-sys.PtrSize))}// 设置当前桶的溢出桶func(h*hmap)setoverflow(t*maptype,b,ovf*bmap){h.incrnoverflow()ift.bucket.kind&kindNoPointers!=0{h.createOverflow()//重点,...
(buckets less than this have been evacuated)extra*mapextra// optional fields}// mapextra holds fields that are not present on all maps.type mapextra struct{// If both key and elem do not contain pointers and are inline, then we mark bucket// type as containing no pointers. This avoids...
memclrHasPointers(buckets, size) }else{ memclrNoHeapPointers(buckets, size) } }ifbase != nbuckets {// 处理多申请出来的bucket}returnbuckets, nextOverflow } 这里用到了比较多的指针计算,需要细细品读。 首先,就是就是通过B计算一个base值,base = 1 << B (2 ^ B) ...
memclrHasPointers(e, t.elem.size) } else { memclrNoHeapPointers(e, t.elem.size) } // 标记空 b.tophash[i] = emptyOne // If the bucket now ends in a bunch of emptyOne states, // change those to emptyRest states. if i == bucketCnt-1 { ...