github.com/tidwall/go@v0.0.0-20170415222209-6694a6888b7d/src/cmd/compile/internal/syntax/syntax.go (about)

     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  // Error describes a syntax error. Error implements the error interface.
    18  type Error struct {
    19  	Pos src.Pos
    20  	Msg string
    21  }
    22  
    23  func (err Error) Error() string {
    24  	return fmt.Sprintf("%s: %s", err.Pos, err.Msg)
    25  }
    26  
    27  var _ error = Error{} // verify that Error implements error
    28  
    29  // An ErrorHandler is called for each error encountered reading a .go file.
    30  type ErrorHandler func(err error)
    31  
    32  // A Pragma value is a set of flags that augment a function or
    33  // type declaration. Callers may assign meaning to the flags as
    34  // appropriate.
    35  type Pragma uint16
    36  
    37  // A PragmaHandler is used to process //line and //go: directives as
    38  // they're scanned. The returned Pragma value will be unioned into the
    39  // next FuncDecl node.
    40  type PragmaHandler func(pos src.Pos, text string) Pragma
    41  
    42  // Parse parses a single Go source file from src and returns the corresponding
    43  // syntax tree. If there are errors, Parse will return the first error found,
    44  // and a possibly partially constructed syntax tree, or nil if no correct package
    45  // clause was found. The base argument is only used for position information.
    46  //
    47  // If errh != nil, it is called with each error encountered, and Parse will
    48  // process as much source as possible. If errh is nil, Parse will terminate
    49  // immediately upon encountering an error.
    50  //
    51  // If a PragmaHandler is provided, it is called with each pragma encountered.
    52  //
    53  // The Mode argument is currently ignored.
    54  func Parse(base *src.PosBase, src io.Reader, errh ErrorHandler, pragh PragmaHandler, mode Mode) (_ *File, first error) {
    55  	defer func() {
    56  		if p := recover(); p != nil {
    57  			if err, ok := p.(Error); ok {
    58  				first = err
    59  				return
    60  			}
    61  			panic(p)
    62  		}
    63  	}()
    64  
    65  	var p parser
    66  	p.init(base, src, errh, pragh)
    67  	p.next()
    68  	return p.fileOrNil(), p.first
    69  }
    70  
    71  // ParseBytes behaves like Parse but it reads the source from the []byte slice provided.
    72  func ParseBytes(base *src.PosBase, src []byte, errh ErrorHandler, pragh PragmaHandler, mode Mode) (*File, error) {
    73  	return Parse(base, &bytesReader{src}, errh, pragh, mode)
    74  }
    75  
    76  type bytesReader struct {
    77  	data []byte
    78  }
    79  
    80  func (r *bytesReader) Read(p []byte) (int, error) {
    81  	if len(r.data) > 0 {
    82  		n := copy(p, r.data)
    83  		r.data = r.data[n:]
    84  		return n, nil
    85  	}
    86  	return 0, io.EOF
    87  }
    88  
    89  // ParseFile behaves like Parse but it reads the source from the named file.
    90  func ParseFile(filename string, errh ErrorHandler, pragh PragmaHandler, mode Mode) (*File, error) {
    91  	f, err := os.Open(filename)
    92  	if err != nil {
    93  		if errh != nil {
    94  			errh(err)
    95  		}
    96  		return nil, err
    97  	}
    98  	defer f.Close()
    99  	return Parse(src.NewFileBase(filename, filename), f, errh, pragh, mode)
   100  }