| 1 | // Copyright 2014 The Go Authors. All rights reserved. |
|---|---|
| 2 | // Use of this source code is governed by a BSD-style |
| 3 | // license that can be found in the LICENSE file. |
| 4 | |
| 5 | // This file implements a cache of method sets. |
| 6 | |
| 7 | package typeutil |
| 8 | |
| 9 | import ( |
| 10 | "go/types" |
| 11 | "sync" |
| 12 | ) |
| 13 | |
| 14 | // A MethodSetCache records the method set of each type T for which |
| 15 | // MethodSet(T) is called so that repeat queries are fast. |
| 16 | // The zero value is a ready-to-use cache instance. |
| 17 | type MethodSetCache struct { |
| 18 | mu sync.Mutex |
| 19 | named map[*types.Named]struct{ value, pointer *types.MethodSet } // method sets for named N and *N |
| 20 | others map[types.Type]*types.MethodSet // all other types |
| 21 | } |
| 22 | |
| 23 | // MethodSet returns the method set of type T. It is thread-safe. |
| 24 | // |
| 25 | // If cache is nil, this function is equivalent to types.NewMethodSet(T). |
| 26 | // Utility functions can thus expose an optional *MethodSetCache |
| 27 | // parameter to clients that care about performance. |
| 28 | func (cache *MethodSetCache) MethodSet(T types.Type) *types.MethodSet { |
| 29 | if cache == nil { |
| 30 | return types.NewMethodSet(T) |
| 31 | } |
| 32 | cache.mu.Lock() |
| 33 | defer cache.mu.Unlock() |
| 34 | |
| 35 | switch T := T.(type) { |
| 36 | case *types.Named: |
| 37 | return cache.lookupNamed(T).value |
| 38 | |
| 39 | case *types.Pointer: |
| 40 | if N, ok := T.Elem().(*types.Named); ok { |
| 41 | return cache.lookupNamed(N).pointer |
| 42 | } |
| 43 | } |
| 44 | |
| 45 | // all other types |
| 46 | // (The map uses pointer equivalence, not type identity.) |
| 47 | mset := cache.others[T] |
| 48 | if mset == nil { |
| 49 | mset = types.NewMethodSet(T) |
| 50 | if cache.others == nil { |
| 51 | cache.others = make(map[types.Type]*types.MethodSet) |
| 52 | } |
| 53 | cache.others[T] = mset |
| 54 | } |
| 55 | return mset |
| 56 | } |
| 57 | |
| 58 | func (cache *MethodSetCache) lookupNamed(named *types.Named) struct{ value, pointer *types.MethodSet } { |
| 59 | if cache.named == nil { |
| 60 | cache.named = make(map[*types.Named]struct{ value, pointer *types.MethodSet }) |
| 61 | } |
| 62 | // Avoid recomputing mset(*T) for each distinct Pointer |
| 63 | // instance whose underlying type is a named type. |
| 64 | msets, ok := cache.named[named] |
| 65 | if !ok { |
| 66 | msets.value = types.NewMethodSet(named) |
| 67 | msets.pointer = types.NewMethodSet(types.NewPointer(named)) |
| 68 | cache.named[named] = msets |
| 69 | } |
| 70 | return msets |
| 71 | } |
| 72 |
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