字典 – Golang:计算地图的内存占用量(或字节长度)
发布时间:2020-12-16 09:27:23 所属栏目:大数据 来源:网络整理
导读:我想将地图限制为最大X字节.似乎没有直接计算地图字节长度的方法. “encoding / binary”包有一个很好的Size函数,但它只适用于切片或“固定值”,而不适用于map. 我可以尝试从地图中获取所有键/值对,推断它们的类型(如果它是map [string] interface {})并计算
我想将地图限制为最大X字节.似乎没有直接计算地图字节长度的方法.
“encoding / binary”包有一个很好的Size函数,但它只适用于切片或“固定值”,而不适用于map. 我可以尝试从地图中获取所有键/值对,推断它们的类型(如果它是map [string] interface {})并计算长度 – 但这既麻烦又可能不正确(因为这将排除“内部“地图本身的golang成本 – 管理元素指针等”. 这样做的任何建议方式?最好是代码示例. 解决方法
对于地图标题,这是
the definition:
// A header for a Go map. type hmap struct { // Note: the format of the Hmap is encoded in ../../cmd/gc/reflect.c and // ../reflect/type.go. Don't change this structure without also changing that code! count int // # live cells == size of map. Must be first (used by len() builtin) flags uint32 hash0 uint32 // hash seed B uint8 // log_2 of # of buckets (can hold up to loadFactor * 2^B items) buckets unsafe.Pointer // array of 2^B Buckets. may be nil if count==0. oldbuckets unsafe.Pointer // previous bucket array of half the size,non-nil only when growing nevacuate uintptr // progress counter for evacuation (buckets less than this have been evacuated) } 计算它的大小非常简单(unsafe.Sizeof). 这是地图指向的每个桶的定义: // A bucket for a Go map. type bmap struct { tophash [bucketCnt]uint8 // Followed by bucketCnt keys and then bucketCnt values. // NOTE: packing all the keys together and then all the values together makes the // code a bit more complicated than alternating key/value/key/value/... but it allows // us to eliminate padding which would be needed for,e.g.,map[int64]int8. // Followed by an overflow pointer. } bucketCnt是一个常量,定义为: bucketCnt = 1 << bucketCntBits // equals decimal 8 bucketCntBits = 3 最终的计算是: unsafe.Sizeof(hmap) + (len(theMap) * 8) + (len(theMap) * 8 * unsafe.Sizeof(x)) + (len(theMap) * 8 * unsafe.Sizeof(y)) 如果Map是您的地图值,则x是地图的键类型的值,y是地图的值类型的值. 您必须通过程序集与程序包共享hmap结构,类似于运行时中的 (编辑:李大同) 【声明】本站内容均来自网络,其相关言论仅代表作者个人观点,不代表本站立场。若无意侵犯到您的权利,请及时与联系站长删除相关内容! |