| 1 | package sync |
|---|---|
| 2 | |
| 3 | // Rudimentary implementation of a mutex for interp tests. |
| 4 | type Mutex struct { |
| 5 | c chan int // Mutex is held when held c!=nil and is empty. Access is guarded by g. |
| 6 | } |
| 7 | |
| 8 | func (m *Mutex) Lock() { |
| 9 | c := ch(m) |
| 10 | <-c |
| 11 | } |
| 12 | |
| 13 | func (m *Mutex) Unlock() { |
| 14 | c := ch(m) |
| 15 | c <- 1 |
| 16 | } |
| 17 | |
| 18 | // sequentializes Mutex.c access. |
| 19 | var g = make(chan int, 1) |
| 20 | |
| 21 | func init() { |
| 22 | g <- 1 |
| 23 | } |
| 24 | |
| 25 | // ch initializes the m.c field if needed and returns it. |
| 26 | func ch(m *Mutex) chan int { |
| 27 | <-g |
| 28 | defer func() { |
| 29 | g <- 1 |
| 30 | }() |
| 31 | if m.c == nil { |
| 32 | m.c = make(chan int, 1) |
| 33 | m.c <- 1 |
| 34 | } |
| 35 | return m.c |
| 36 | } |
| 37 |
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