Created
August 23, 2021 14:34
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| package main | |
| import ( | |
| "context" | |
| "fmt" | |
| "time" | |
| "unsafe" | |
| ) | |
| func main() { | |
| // build a context for test | |
| ctx := context.Background() | |
| ctx = context.WithValue(ctx, "key1", "value1") | |
| ctx, _ = context.WithCancel(ctx) | |
| ctx = context.WithValue(ctx, &TestData{ | |
| Name: "key2", | |
| Number: 1, | |
| }, "value2") | |
| ctx, _ = context.WithDeadline(ctx, time.Now().Add(time.Second*20)) | |
| ctx = context.WithValue(ctx, &TestData{ | |
| Name: "key3", | |
| Number: 2, | |
| }, "value3") | |
| ctx = context.WithValue(ctx, &TestData{ | |
| Name: "key4", | |
| Number: 3, | |
| }, nil) | |
| ctx = context.WithValue(ctx, &TestData{ | |
| Name: "key5", | |
| Number: 4, | |
| }, nil) | |
| // get keys and values | |
| m := GetKeyValues(ctx) | |
| printMapKeyValue(m) | |
| // output: | |
| // [key: &{Name:key3 Number:2}] [value: value3] | |
| // [key: &{Name:key2 Number:1}] [value: value2] | |
| // [key: key1] [value: value1] | |
| // [key: &{Name:key5 Number:4}] [value: <nil>] | |
| // [key: &{Name:key4 Number:3}] [value: <nil>] | |
| } | |
| type TestData struct { | |
| Name string | |
| Number int | |
| } | |
| type iface struct { | |
| itab, data uintptr | |
| } | |
| type emptyCtx int | |
| type valueCtx struct { | |
| context.Context | |
| key, val interface{} | |
| } | |
| func GetKeyValues(ctx context.Context) map[interface{}]interface{} { | |
| m := make(map[interface{}]interface{}) | |
| getKeyValue(ctx, m) | |
| return m | |
| } | |
| func getKeyValue(ctx context.Context, m map[interface{}]interface{}) { | |
| ictx := *(*iface)(unsafe.Pointer(&ctx)) | |
| if ictx.data == 0 || int(*(*emptyCtx)(unsafe.Pointer(ictx.data))) == 0 { | |
| return | |
| } | |
| valCtx := (*valueCtx)(unsafe.Pointer(ictx.data)) | |
| if valCtx != nil && valCtx.key != nil { | |
| m[valCtx.key] = valCtx.val | |
| } | |
| getKeyValue(valCtx.Context, m) | |
| } | |
| func printMapKeyValue(m map[interface{}]interface{}) { | |
| for k, v := range m { | |
| fmt.Printf("[key: %+v] [value: %+v]\n", k, v) | |
| } | |
| } |
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