add simple synchronization mechanism.

R=rsc
DELTA=25  (19 added, 1 deleted, 5 changed)
OCL=17346
CL=17346

diff --git a/usr/r/reflect/main.go b/usr/r/reflect/main.go
index f46b6d81eacfb7edf4223b1daa22efdab2362db9..0348cef9fef78e79eb0e09a877de2811432ca67c 100644 (file)
--- a/usr/r/reflect/main.go
+++ b/usr/r/reflect/main.go
@@ -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");
 }

diff --git a/usr/r/reflect/type.go b/usr/r/reflect/type.go
index 4eda9f407174ddb5240916e031a10c9c6fd334f7..965a3177b329702e69ae229e1b38f6a773f79d21 100644 (file)
--- a/usr/r/reflect/type.go
+++ b/usr/r/reflect/type.go
@@ -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;
 }