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add simple synchronization mechanism.

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R=rsc
DELTA=25  (19 added, 1 deleted, 5 changed)
OCL=17346
CL=17346
This commit is contained in:
Rob Pike 2008-10-17 10:58:34 -07:00
parent 925454e932
commit cac904b609
2 changed files with 24 additions and 6 deletions
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2
usr/r/reflect/main.go
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@ -39,6 +39,6 @@ func main() {
t = reflect.ParseTypeString("*(a int8, b int32)");
s = reflect.ToString(t); print(s, "\n");
t = reflect.ParseTypeString("struct {c *(? *chan *int32, ? *int8)}");
t = reflect.ParseTypeString("struct {c *(? *chan *P.integer, ? *int8)}");
s = reflect.ToString(t); print(s, "\n");
}

28
usr/r/reflect/type.go
View File

@ -309,14 +309,30 @@ func NewFuncTypeStruct(in, out *StructTypeStruct) *FuncTypeStruct {
// Cache of expanded types keyed by type name.
var types *map[string] *Type // BUG TODO: should be Type not *Type
// List of typename, typestring pairs
var typestrings *map[string] string
// Map of basic types to prebuilt StubTypes
var basicstubs *map[string] *StubType
var MissingStub *StubType;
// The database stored in the maps is global; use locking to guarantee safety.
var lockchan *chan bool // Channel with buffer of 1, used as a mutex
func Lock() {
lockchan <- true // block if buffer is full
}
func Unlock() {
<-lockchan // release waiters
}
func init() {
lockchan = new(chan bool, 1); // unlocked at creation - buffer is empty
Lock(); // not necessary because of init ordering but be safe.
types = new(map[string] *Type);
typestrings = new(map[string] string);
basicstubs = new(map[string] *StubType);
@ -352,10 +368,9 @@ func init() {
basicstubs["float80"] = NewStubType(Float80);
basicstubs["string"] = NewStubType(String);
typestrings["P.integer"] = "int32";
return;
typestrings["P.S"] = "struct {t *P.T}";
typestrings["P.T"] = "struct {c *(? *chan P.S, *int)}";
typestrings["P.integer"] = "int32"; // TODO: for testing; remove
Unlock();
}
/*
@ -648,7 +663,7 @@ export func ParseTypeString(str string) Type {
return p.Type().Get();
}
// Look up type string associated with name.
// Look up type string associated with name. Lock is held.
func TypeNameToTypeString(name string) string {
s, ok := typestrings[name];
if !ok {
@ -660,8 +675,10 @@ func TypeNameToTypeString(name string) string {
// Type is known by name. Find (and create if necessary) its real type.
func ExpandType(name string) Type {
Lock();
t, ok := types[name];
if ok {
Unlock();
return *t
}
types[name] = &Missing; // prevent recursion; will overwrite
@ -669,5 +686,6 @@ func ExpandType(name string) Type {
p := new(Type);
*p = t1;
types[name] = p;
Unlock();
return t1;
}