Parse -> Fetch, now tries to hit cache

parser/cache.go

@@ -2,7 +2,7 @@ package parser
 
 // cacheItem stores an item of the parser cache.
 type cacheItem struct {
-	section Section
+	tree    SyntaxTree
 	skimmed bool
 }
 

parser/parser.go

@@ -18,15 +18,28 @@ type ParsingOperation struct {
 }
 
 // TODO:
-// - implement parser cache
-// - have this try to hit the cache, and actually parse on miss
+// * implement parser cache
+// * have this try to hit the cache, and actually parse on miss
 // - rename this to Fetch
 // - add `skim bool` argument. when this is true, don't parse any code or data
 //   section initialization values, just definitions and their default values.
 
-// Parse reads the files located in the module specified by modulePath, and
-// converts them into an abstract syntax tree.
-func Parse (modulePath string) (tree SyntaxTree, err error) {
+// Fetch returns the parsed module located at the specified path, and returns an
+// abstract syntax tree. If the module has not yet been parsed, it parses it
+// first.
+func Fetch (modulePath string) (tree SyntaxTree, err error) {
+	if modulePath[0] != '/' {
+		panic("module path did not begin at filesystem root")
+	}
+
+	// try to hit cache
+	cached, exists := cache[modulePath]
+	if exists {
+		tree = cached.tree
+		return
+	}
+
+	// miss, so parse the module.
 	parser := ParsingOperation {
 		modulePath: modulePath,
 		tree: SyntaxTree {
@@ -56,6 +69,13 @@ func Parse (modulePath string) (tree SyntaxTree, err error) {
 	}
 	
 	tree = parser.tree
+
+	// cache tree
+	cache[modulePath] = cacheItem {
+		tree:    tree,
+		skimmed: false,
+	}
+	
 	return
 }