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// Copyright 2013 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package loader
import (
"go/ast"
"go/build"
"go/parser"
"go/token"
"io"
"os"
"strconv"
"sync"
"golang.org/x/tools/go/buildutil"
)
// We use a counting semaphore to limit
// the number of parallel I/O calls per process.
var ioLimit = make(chan bool, 10)
// parseFiles parses the Go source files within directory dir and
// returns the ASTs of the ones that could be at least partially parsed,
// along with a list of I/O and parse errors encountered.
//
// I/O is done via ctxt, which may specify a virtual file system.
// displayPath is used to transform the filenames attached to the ASTs.
//
func parseFiles(fset *token.FileSet, ctxt *build.Context, displayPath func(string) string, dir string, files []string, mode parser.Mode) ([]*ast.File, []error) {
if displayPath == nil {
displayPath = func(path string) string { return path }
}
var wg sync.WaitGroup
n := len(files)
parsed := make([]*ast.File, n)
errors := make([]error, n)
for i, file := range files {
if !buildutil.IsAbsPath(ctxt, file) {
file = buildutil.JoinPath(ctxt, dir, file)
}
wg.Add(1)
go func(i int, file string) {
ioLimit <- true // wait
defer func() {
wg.Done()
<-ioLimit // signal
}()
var rd io.ReadCloser
var err error
if ctxt.OpenFile != nil {
rd, err = ctxt.OpenFile(file)
} else {
rd, err = os.Open(file)
}
if err != nil {
errors[i] = err // open failed
return
}
// ParseFile may return both an AST and an error.
parsed[i], errors[i] = parser.ParseFile(fset, displayPath(file), rd, mode)
rd.Close()
}(i, file)
}
wg.Wait()
// Eliminate nils, preserving order.
var o int
for _, f := range parsed {
if f != nil {
parsed[o] = f
o++
}
}
parsed = parsed[:o]
o = 0
for _, err := range errors {
if err != nil {
errors[o] = err
o++
}
}
errors = errors[:o]
return parsed, errors
}
// scanImports returns the set of all import paths from all
// import specs in the specified files.
func scanImports(files []*ast.File) map[string]bool {
imports := make(map[string]bool)
for _, f := range files {
for _, decl := range f.Decls {
if decl, ok := decl.(*ast.GenDecl); ok && decl.Tok == token.IMPORT {
for _, spec := range decl.Specs {
spec := spec.(*ast.ImportSpec)
// NB: do not assume the program is well-formed!
path, err := strconv.Unquote(spec.Path.Value)
if err != nil {
continue // quietly ignore the error
}
if path == "C" {
continue // skip pseudopackage
}
imports[path] = true
}
}
}
}
return imports
}
// ---------- Internal helpers ----------
// TODO(adonovan): make this a method: func (*token.File) Contains(token.Pos)
func tokenFileContainsPos(f *token.File, pos token.Pos) bool {
p := int(pos)
base := f.Base()
return base <= p && p < base+f.Size()
}