Go Map Internals

bhuppal · April 29, 2021, 12:23am

Go in Action book not given more details about internal implementation about Map. Anybody can explain with good drawing or share some resources to understand fully the internals about Map in Go. Thanks

lutzhorn · April 29, 2021, 12:17pm

Take a look at the source code:

github.com

golang/go/blob/master/src/runtime/map.go

// Copyright 2014 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package runtime

// This file contains the implementation of Go's map type.
//
// A map is just a hash table. The data is arranged
// into an array of buckets. Each bucket contains up to
// 8 key/elem pairs. The low-order bits of the hash are
// used to select a bucket. Each bucket contains a few
// high-order bits of each hash to distinguish the entries
// within a single bucket.
//
// If more than 8 keys hash to a bucket, we chain on
// extra buckets.
//
// When the hashtable grows, we allocate a new array
// of buckets twice as big. Buckets are incrementally

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bhuppal · April 29, 2021, 8:15pm

How the hash function choosing the right bucket?

skillian · April 29, 2021, 9:43pm

Looks like it does it here: https://github.com/golang/go/blob/fd095936673dcb53b96b825d95c1e83adde3ce15/src/runtime/map.go#L414

bhuppal · May 1, 2021, 12:06pm

Thanks for sharing

system · July 30, 2021, 12:13pm

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