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// Copyright 2018 The gVisor Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package main
import (
"bytes"
"fmt"
"go/ast"
"go/format"
"go/parser"
"go/token"
"strconv"
"gvisor.googlesource.com/gvisor/tools/go_generics/globals"
)
type importedPackage struct {
newName string
path string
}
// updateImportIdent modifies the given import identifier with the new name
// stored in the used map. If the identifier doesn't exist in the used map yet,
// a new name is generated and inserted into the map.
func updateImportIdent(orig string, imports mapValue, id *ast.Ident, used map[string]*importedPackage) error {
importName := id.Name
// If the name is already in the table, just use the new name.
m := used[importName]
if m != nil {
id.Name = m.newName
return nil
}
// Create a new entry in the used map.
path := imports[importName]
if path == "" {
return fmt.Errorf("Unknown path to package '%s', used in '%s'", importName, orig)
}
m = &importedPackage{
newName: fmt.Sprintf("__generics_imported%d", len(used)),
path: strconv.Quote(path),
}
used[importName] = m
id.Name = m.newName
return nil
}
// convertExpression creates a new string that is a copy of the input one with
// all imports references renamed to the names in the "used" map. If the
// referenced import isn't in "used" yet, a new one is created based on the path
// in "imports" and stored in "used". For example, if string s is
// "math.MaxUint32-math.MaxUint16+10", it would be converted to
// "x.MaxUint32-x.MathUint16+10", where x is a generated name.
func convertExpression(s string, imports mapValue, used map[string]*importedPackage) (string, error) {
// Parse the expression in the input string.
expr, err := parser.ParseExpr(s)
if err != nil {
return "", fmt.Errorf("Unable to parse \"%s\": %v", s, err)
}
// Go through the AST and update references.
var retErr error
ast.Inspect(expr, func(n ast.Node) bool {
switch x := n.(type) {
case *ast.SelectorExpr:
if id := globals.GetIdent(x.X); id != nil {
if err := updateImportIdent(s, imports, id, used); err != nil {
retErr = err
}
return false
}
}
return true
})
if retErr != nil {
return "", retErr
}
// Convert the modified AST back to a string.
fset := token.NewFileSet()
var buf bytes.Buffer
if err := format.Node(&buf, fset, expr); err != nil {
return "", err
}
return string(buf.Bytes()), nil
}
// updateImports replaces all maps in the input slice with copies where the
// mapped values have had all references to imported packages renamed to
// generated names. It also returns an import declaration for all the renamed
// import packages.
//
// For example, if the input maps contains A=math.B and C=math.D, the updated
// maps will instead contain A=__generics_imported0.B and
// C=__generics_imported0.C, and the 'import __generics_imported0 "math"' would
// be returned as the import declaration.
func updateImports(maps []mapValue, imports mapValue) (ast.Decl, error) {
importsUsed := make(map[string]*importedPackage)
// Update all maps.
for i, m := range maps {
newMap := make(mapValue)
for n, e := range m {
updated, err := convertExpression(e, imports, importsUsed)
if err != nil {
return nil, err
}
newMap[n] = updated
}
maps[i] = newMap
}
// Nothing else to do if no imports are used in the expressions.
if len(importsUsed) == 0 {
return nil, nil
}
// Create spec array for each new import.
specs := make([]ast.Spec, 0, len(importsUsed))
for _, i := range importsUsed {
specs = append(specs, &ast.ImportSpec{
Name: &ast.Ident{Name: i.newName},
Path: &ast.BasicLit{Value: i.path},
})
}
return &ast.GenDecl{
Tok: token.IMPORT,
Specs: specs,
Lparen: token.NoPos + 1,
}, nil
}
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