1 // Copyright 2016 The Go Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style 3 // license that can be found in the LICENSE file. 4 5 package syntax 6 7 import ( 8 "cmd/internal/src" 9 "fmt" 10 "io" 11 "os" 12 ) 13 14 // Mode describes the parser mode. 15 type Mode uint 16 17 // Modes supported by the parser. 18 const ( 19 CheckBranches Mode = 1 << iota // check correct use of labels, break, continue, and goto statements 20 ) 21 22 // Error describes a syntax error. Error implements the error interface. 23 type Error struct { 24 Pos src.Pos 25 Msg string 26 } 27 28 func (err Error) Error() string { 29 return fmt.Sprintf("%s: %s", err.Pos, err.Msg) 30 } 31 32 var _ error = Error{} // verify that Error implements error 33 34 // An ErrorHandler is called for each error encountered reading a .go file. 35 type ErrorHandler func(err error) 36 37 // A Pragma value is a set of flags that augment a function or 38 // type declaration. Callers may assign meaning to the flags as 39 // appropriate. 40 type Pragma uint16 41 42 // A PragmaHandler is used to process //go: directives as 43 // they're scanned. The returned Pragma value will be unioned into the 44 // next FuncDecl node. 45 type PragmaHandler func(pos src.Pos, text string) Pragma 46 47 // A FilenameHandler is used to process each filename encountered 48 // in //line directives. The returned value is used as the absolute filename. 49 type FilenameHandler func(name string) string 50 51 // Parse parses a single Go source file from src and returns the corresponding 52 // syntax tree. If there are errors, Parse will return the first error found, 53 // and a possibly partially constructed syntax tree, or nil if no correct package 54 // clause was found. The base argument is only used for position information. 55 // 56 // If errh != nil, it is called with each error encountered, and Parse will 57 // process as much source as possible. If errh is nil, Parse will terminate 58 // immediately upon encountering an error. 59 // 60 // If a PragmaHandler is provided, it is called with each pragma encountered. 61 // 62 // If a FilenameHandler is provided, it is called to process each filename 63 // encountered in //line directives. 64 // 65 // The Mode argument is currently ignored. 66 func Parse(base *src.PosBase, src io.Reader, errh ErrorHandler, pragh PragmaHandler, fileh FilenameHandler, mode Mode) (_ *File, first error) { 67 defer func() { 68 if p := recover(); p != nil { 69 if err, ok := p.(Error); ok { 70 first = err 71 return 72 } 73 panic(p) 74 } 75 }() 76 77 var p parser 78 p.init(base, src, errh, pragh, fileh, mode) 79 p.next() 80 return p.fileOrNil(), p.first 81 } 82 83 // ParseBytes behaves like Parse but it reads the source from the []byte slice provided. 84 func ParseBytes(base *src.PosBase, src []byte, errh ErrorHandler, pragh PragmaHandler, fileh FilenameHandler, mode Mode) (*File, error) { 85 return Parse(base, &bytesReader{src}, errh, pragh, fileh, mode) 86 } 87 88 type bytesReader struct { 89 data []byte 90 } 91 92 func (r *bytesReader) Read(p []byte) (int, error) { 93 if len(r.data) > 0 { 94 n := copy(p, r.data) 95 r.data = r.data[n:] 96 return n, nil 97 } 98 return 0, io.EOF 99 } 100 101 // ParseFile behaves like Parse but it reads the source from the named file. 102 func ParseFile(filename string, errh ErrorHandler, pragh PragmaHandler, mode Mode) (*File, error) { 103 f, err := os.Open(filename) 104 if err != nil { 105 if errh != nil { 106 errh(err) 107 } 108 return nil, err 109 } 110 defer f.Close() 111 return Parse(src.NewFileBase(filename, filename), f, errh, pragh, nil, mode) 112 } 113
