gpython/parser/lexer.go at main · go-python/gpython · GitHub

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// Use of this source code is governed by a BSD-style

// license that can be found in the LICENSE file.

package parser

// FIXME need to implement formfeed

// Lexer should count line numbers too!

import (

"bufio"

"bytes"

"fmt"

"io"

"log"

"regexp"

"strings"

"unicode"

"github.com/go-python/gpython/ast"

"github.com/go-python/gpython/py"

)

// The parser expects the lexer to return 0 on EOF. Give it a name

// for clarity.

const eof = 0

// Signal eof with Error

const eofError = -1

// Standard python definition of a tab

const tabSize = 8

// The parser uses the type <prefix>Lex as a lexer. It must provide

// the methods Lex(*<prefix>SymType) int and Error(string).

type yyLex struct {

reader *bufio.Reader

filename string // name of the file being read

line string // current line being parsed

lastLine string // last line that was parsed

pos ast.Pos // current position within file

yylval *yySymType // last token

eof bool // flag to show EOF was read

error bool // set if an error has ocurred

errorString string // the string of the error

indentStack []int // indent stack to control INDENT / DEDENT tokens

state int // current state of state machine

currentIndent string // whitespace at start of current line

interactive bool // set if mode "single" reading interactive input

exec bool // set if mode "exec" reading from file

bracket int // number of open [ ]

parenthesis int // number of open ( )

brace int // number of open { }

mod ast.Mod // output

tokens []int // buffered tokens to output

}

// Create a new lexer

// The mode argument specifies what kind of code must be compiled; it

// can be 'exec' if source consists of a sequence of statements,

// 'eval' if it consists of a single expression, or 'single' if it

// consists of a single interactive statement

func NewLex(r io.Reader, filename string, mode py.CompileMode) (*yyLex, error) {

x := &yyLex{

reader: bufio.NewReader(r),

filename: filename,

indentStack: []int{0},

state: readString,

}

switch mode {

case py.ExecMode:

x.queue(FILE_INPUT)

x.exec = true

case py.EvalMode:

x.queue(EVAL_INPUT)

case py.SingleMode:

x.queue(SINGLE_INPUT)

x.interactive = true

default:

return nil, py.ExceptionNewf(py.ValueError, "compile mode must be 'exec', 'eval' or 'single'")

}

return x, nil

}

// queue tokens for later return

func (x *yyLex) queue(tokens ...int) {

x.tokens = append(x.tokens, tokens...)

}

// Return whether the token queue is empty

func (x *yyLex) queueEmpty() bool {

return len(x.tokens) == 0

}

// dequeue a token for return

// panic if no token available

func (x *yyLex) dequeue() int {

if x.queueEmpty() {

panic("token queue empty")

}

token := x.tokens[0]

x.tokens = x.tokens[1:]

return token

}

// Refill line

func (x *yyLex) refill() {

var err error

x.line, err = x.reader.ReadString('\n')

if strings.HasSuffix(x.line, "\r\n") {

x.line = x.line[:len(x.line)-2] + "\n"

}

if yyDebug >= 2 {

fmt.Printf("line = %q, err = %v\n", x.line, err)

}

x.pos.Lineno += 1

x.pos.ColOffset = 0

switch err {

case nil:

case io.EOF:

x.eof = true

default:

x.eof = true

x.SyntaxErrorf("Error reading input: %v", err)

}

// If this is exec input, add a newline to the end of the

// string if there isn't one already.

if x.eof && x.exec && len(x.line) > 0 && x.line[len(x.line)-1] != '\n' {

x.line += "\n"

}

x.lastLine = x.line

}

// Finds the length of a space and tab seperated string

func countIndent(s string) int {

if len(s) == 0 {

return 0

}

// FIXME these rules don't actually implement the python3

// lexing rules which state

// Indentation is rejected as inconsistent if a source file

// mixes tabs and spaces in a way that makes the meaning

// dependent on the worth of a tab in spaces; a TabError is

// raised in that case

indent := 0

for _, c := range s {

switch c {

case ' ':

indent++

case '\t':

// 012345678901234567

// a b

// ab

// a b

indent += tabSize - (indent & (tabSize - 1))

default:

panic(py.ExceptionNewf(py.IndentationError, "unexpected indent"))

}

return indent

}

var operators = map[string]int{

// 1 Character operators

"(": '(',

")": ')',

"[": '[',

"]": ']',

":": ':',

",": ',',

";": ';',

"+": '+',

"-": '-',

"*": '*',

"/": '/',

"|": '|',

"&": '&',

"<": '<',

">": '>',

"=": '=',

".": '.',

"%": '%',

"{": '{',

"}": '}',

"^": '^',

"~": '~',

"@": '@',

// 2 Character operators

"!=": PLINGEQ,

"%=": PERCEQ,

"&=": ANDEQ,

"**": STARSTAR,

"*=": STAREQ,

"+=": PLUSEQ,

"-=": MINUSEQ,

"->": MINUSGT,

"//": DIVDIV,

"/=": DIVEQ,

"<<": LTLT,

"<=": LTEQ,

"<>": LTGT,

"==": EQEQ,

">=": GTEQ,

">>": GTGT,

"^=": HATEQ,

"|=": PIPEEQ,

// 3 Character operators

"**=": STARSTAREQ,

"...": ELIPSIS,

"//=": DIVDIVEQ,

"<<=": LTLTEQ,

">>=": GTGTEQ,

}

var tokens = map[string]int{

// Reserved words

"False": FALSE,

"None": NONE,

"True": TRUE,

"and": AND,

"as": AS,

"assert": ASSERT,

"break": BREAK,

"class": CLASS,

"continue": CONTINUE,

"def": DEF,

"del": DEL,

"elif": ELIF,

"else": ELSE,

"except": EXCEPT,

"finally": FINALLY,

"for": FOR,

"from": FROM,

"global": GLOBAL,

"if": IF,

"import": IMPORT,

"in": IN,

"is": IS,

"lambda": LAMBDA,

"nonlocal": NONLOCAL,

"not": NOT,

"or": OR,

"pass": PASS,

"raise": RAISE,

"return": RETURN,

"try": TRY,

"while": WHILE,

"with": WITH,

"yield": YIELD,

}

var tokenToString map[int]string

// Make tokenToString map

func init() {

tokenToString = make(map[int]string, len(operators)+len(tokens)+16)

for k, v := range operators {

tokenToString[v] = k

}

for k, v := range tokens {

tokenToString[v] = k

}

tokenToString[eof] = "eof"

tokenToString[eofError] = "eofError"

tokenToString[NEWLINE] = "NEWLINE"

tokenToString[ENDMARKER] = "ENDMARKER"

tokenToString[NAME] = "NAME"

tokenToString[INDENT] = "INDENT"

tokenToString[DEDENT] = "DEDENT"

tokenToString[STRING] = "STRING"

tokenToString[NUMBER] = "NUMBER"

tokenToString[FILE_INPUT] = "FILE_INPUT"

tokenToString[SINGLE_INPUT] = "SINGLE_INPUT"

tokenToString[EVAL_INPUT] = "EVAL_INPUT"

}

// True if there are any open brackets

func (x *yyLex) openBrackets() bool {

return x.bracket != 0 || x.parenthesis != 0 || x.brace != 0

}

// States

const (

readString = iota

readIndent

checkEmpty

checkIndent

parseTokens

checkEof

isEof

)

// A Token with value

type LexToken struct {

token int

value py.Object

pos ast.Pos

}

// Convert the yySymType and token into a LexToken

func newLexToken(token int, yylval *yySymType) (lt LexToken) {

lt.token = token

lt.pos = yylval.pos

if token == NAME {

lt.value = py.String(yylval.str)

} else if token == STRING || token == NUMBER {

lt.value = yylval.obj

} else {

lt.value = nil

}

return

}

// String a LexToken

func (lt *LexToken) String() string {

name := tokenToString[lt.token]

if lt.value == nil {

return fmt.Sprintf("%q (%d) %d:%d", name, lt.token, lt.pos.Lineno, lt.pos.ColOffset)

}

return fmt.Sprintf("%q (%d) = %T{%v} %d:%d", name, lt.token, lt.value, lt.value, lt.pos.Lineno, lt.pos.ColOffset)

}

// An slice of LexToken~s

type LexTokens []LexToken

// Compare two LexTokens

func (as LexTokens) Eq(bs []LexToken) bool {

if len(as) != len(bs) {

return false

}

for i := range as {

a := as[i]

b := bs[i]

if a != b {

return false

}

return true

}

// String a LexTokens

func (lts LexTokens) String() string {

buf := new(bytes.Buffer)

_, _ = buf.WriteString("[")

for i := range lts {

lt := lts[i]

_, _ = buf.WriteString("{")

_, _ = buf.WriteString(lt.String())

_, _ = buf.WriteString("}, ")

}

_, _ = buf.WriteString("]")

return buf.String()

}

// Queue any remaining DEDENTS

func (x *yyLex) queueDedents() {

for i := len(x.indentStack) - 1; i >= 1; i-- {

x.queue(DEDENT)

}

x.indentStack = x.indentStack[:1]

}

// The parser calls this method to get each new token. This

// implementation returns operators and NUM.

func (x *yyLex) Lex(yylval *yySymType) (ret int) {

// Clear out the yySymType on each token (copied from rsc's cc)

*yylval = yySymType{}

x.yylval = yylval

if yyDebug >= 2 {

defer func() {

lt := newLexToken(ret, yylval)

fmt.Printf("LEX> %s\n", lt.String())

}()

}

// Return queued tokens if there are any

if !x.queueEmpty() {

yylval.pos = x.pos

return x.dequeue()

}

for {

yylval.pos = x.pos

switch x.state {

case readString:

// Read x.line

x.refill()

yylval.pos = x.pos

x.state++

if x.line == "" && x.eof {

x.state = checkEof

// During interactive input of statements an entirely blank logical

// line (i.e. one containing not even whitespace or a comment)

// terminates a multi-line statement.

if x.interactive && !x.openBrackets() {

x.queueDedents()

x.queue(NEWLINE)

return x.dequeue()

}

continue

}

case readIndent:

// Read the initial indent and get rid of it

trimmed := strings.TrimLeft(x.line, " \t")

removed := len(x.line) - len(trimmed)

x.currentIndent = x.line[:removed]

x.pos.ColOffset += removed

x.line = trimmed

x.state++

case checkEmpty:

despaced := strings.TrimSpace(x.line) // remove other whitespace other than " \t"

// Ignore line if just white space or whitespace then comment

if despaced == "" || despaced[0] == '#' {

x.state = checkEof

continue

}

x.state++

case checkIndent:

x.state++

// Don't output INDENT or DEDENT if brackets are open

if x.openBrackets() {

continue

}

// See if indent has changed and issue INDENT / DEDENT

indent := countIndent(x.currentIndent)

i := len(x.indentStack) - 1

indentStackTop := x.indentStack[i]

if indent == indentStackTop {

continue

} else if indent > indentStackTop {

x.indentStack = append(x.indentStack, indent)

yylval.pos.ColOffset = 0 // Indents start at 0

return INDENT

} else {

for ; i >= 0; i-- {

if x.indentStack[i] == indent {

goto foundIndent

}

x.queue(DEDENT)

}

x.SyntaxError("Inconsistent indent")

return eof

foundIndent:

x.indentStack = x.indentStack[:i+1]

return x.dequeue()

}

case parseTokens:

// Skip white space

trimmed := strings.TrimLeft(x.line, " \t")

x.pos.ColOffset += len(x.line) - len(trimmed)

x.line = trimmed

// Peek next word

if len(x.line) == 0 {

x.state = checkEof

continue

}

// Check if newline or comment reached

if x.line[0] == '\n' || x.line[0] == '#' {

x.state = checkEof

// Don't output NEWLINE if brackets are open

if x.openBrackets() {

continue

}

return NEWLINE

}

// Check if continuation character

if x.line[0] == '\\' && (len(x.line) <= 1 || x.line[1] == '\n') {

if x.eof {

x.state = checkEof

continue

}

x.refill()

x.state = parseTokens

continue

}

// Note start of token for parser

yylval.pos = x.pos

// Read a number if available

token, value := x.readNumber()

if token != eof {

if token == eofError {

return eof

}

yylval.obj = value

return token

}

// Read a string if available

token, value = x.readString()

if token != eof {

if token == eofError {

return eof

}

yylval.obj = value

return token

}

// Read a keyword or identifier if available

token, str := x.readIdentifierOrKeyword()

if token != eof {

yylval.str = str

return token

}

// Read an operator if available

token = x.readOperator()

if token != eof {

// implement implicit line joining rules

switch token {

case '[':

x.bracket++

case ']':

x.bracket--

case '(':

x.parenthesis++

case ')':

x.parenthesis--

case '{':

x.brace++

case '}':

x.brace--

}

return token

}

// Nothing we recognise found

x.SyntaxError("invalid syntax")

return eof

case checkEof:

if x.eof {

x.queueDedents()

// then return ENDMARKER

x.state = isEof

if !x.interactive {

x.queue(ENDMARKER)

}

if x.queueEmpty() {

continue

}

return x.dequeue()

}

x.state = readString

case isEof:

return eof

default:

panic("Bad state")

}

// Can this rune start an identifier?

// identifier: `xid_start` `xid_continue`*

// id_start: <all characters in general categories Lu, Ll, Lt, Lm, Lo, Nl, the underscore, and characters with the Other_ID_Start property>

// id_continue: <all characters in `id_start`, plus characters in the categories Mn, Mc, Nd, Pc and others with the Other_ID_Continue property>

// xid_start: <all characters in `id_start` whose NFKC normalization is in "id_start xid_continue*">

// xid_continue: <all characters in `id_continue` whose NFKC normalization is in "id_continue*">

func isIdentifierStart(c rune) bool {

switch {

case c >= 'a' && c <= 'z':

return true

case c >= 'A' && c <= 'Z':

return true

case c == '_':

return true

case c < 128:

return false

case unicode.In(c, unicode.Lu, unicode.Ll, unicode.Lt, unicode.Lm, unicode.Lo, unicode.Nl):

return true

}

return false

}

// Can this rune continue an identifier?

func isIdentifierChar(c rune) bool {

switch {

case c >= 'a' && c <= 'z':

return true

case c >= 'A' && c <= 'Z':

return true

case c >= '0' && c <= '9':

return true

case c == '_':

return true

case c < 128:

return false

case unicode.In(c, unicode.Lu, unicode.Ll, unicode.Lt, unicode.Lm, unicode.Lo, unicode.Nl, unicode.Mn, unicode.Mc, unicode.Nd, unicode.Pc):

return true

}

return false

}

// Cut i characters off the start of the line

// returns the characters cut

func (x *yyLex) cut(i int) (cut string) {

cut, x.line = x.line[:i], x.line[i:]

x.pos.ColOffset += i

return cut

}

// Read an identifier

func (x *yyLex) readIdentifier() string {

var i int

var c rune

for i, c = range x.line {

if i == 0 {

if !isIdentifierStart(c) {

goto found

}

} else {

if !isIdentifierChar(c) {

goto found

}

i = len(x.line)

found:

return x.cut(i)

}

// Read an identifier or keyword

func (x *yyLex) readIdentifierOrKeyword() (int, string) {

identifier := x.readIdentifier()

if identifier == "" {

return eof, ""

}

token, ok := tokens[identifier]

if ok {

return token, identifier

}

return NAME, identifier

}

// Read operator - returns token or eof for not found

func (x *yyLex) readOperator() int {

// Look for length 3, 2, 1 operators

for i := 3; i >= 1; i-- {

if len(x.line) >= i {

op := x.line[:i]

if tok, ok := operators[op]; ok {

x.cut(i)

return tok

}

return eof

}

const pointFloat = `([0-9]*\.[0-9]+|[0-9]+\.)`

var (

decimalInteger = regexp.MustCompile(`^[0-9]+[jJ]?`)

illegalDecimalInteger = regexp.MustCompile(`^0[0-9]*[1-9][0-9]*$`)

octalInteger = regexp.MustCompile(`^0[oO][0-7]+`)

hexInteger = regexp.MustCompile(`^0[xX][0-9a-fA-F]+`)

binaryInteger = regexp.MustCompile(`^0[bB][01]+`)

floatNumber = regexp.MustCompile(`^(([0-9]+|` + pointFloat + `)[eE][+-]?[0-9]+|` + pointFloat + `)[jJ]?`)

)

// Read one of the many types of python number

// Returns eof for couldn't read number or eofError on a bad read

func (x *yyLex) readNumber() (token int, value py.Object) {

// Quick check for this being a number

if len(x.line) == 0 {

return eof, nil

}

// Starts with a digit

r0 := x.line[0]

if '0' <= r0 && r0 <= '9' {

goto isNumber

}

// Or starts with . then a digit

if len(x.line) > 1 && r0 == '.' {

if r1 := x.line[1]; '0' <= r1 && r1 <= '9' {

goto isNumber

}

return eof, nil

isNumber:

var s string

var err error

if s = octalInteger.FindString(x.line); s != "" {

value, err = py.IntFromString(s[2:], 8)

if err != nil {

panic(err)

}

} else if s = hexInteger.FindString(x.line); s != "" {

value, err = py.IntFromString(s[2:], 16)

if err != nil {

panic(err)

}

} else if s = binaryInteger.FindString(x.line); s != "" {

value, err = py.IntFromString(s[2:], 2)

if err != nil {

panic(err)

}

} else if s = floatNumber.FindString(x.line); s != "" {

last := s[len(s)-1]

imaginary := false

toParse := s

if last == 'j' || last == 'J' {

imaginary = true

toParse = s[:len(s)-1]

}

value, err = py.FloatFromString(toParse)

if err != nil {

panic(err)

}

if imaginary {

value = py.Complex(complex(0, value.(py.Float)))

}

} else if s = decimalInteger.FindString(x.line); s != "" {

last := s[len(s)-1]

if last == 'j' || last == 'J' {

toParse := s[:len(s)-1]

value, err = py.FloatFromString(toParse)

if err != nil {

panic(err)

}

value = py.Complex(complex(0, value.(py.Float)))

} else {

// Discard numbers with leading 0 except all 0s

if illegalDecimalInteger.FindString(s) != "" {

// FIXME where is this error going in the grammar?

x.SyntaxError("illegal decimal with leading zero")

return eofError, nil

}

value, err = py.IntFromString(s, 10)

if err != nil {

panic(err)

}

} else {

panic("Unparsed number")

}

x.cut(len(s))

token = NUMBER

return

}

// Read one of the many types of python string

// May return eof to skip to next matcher, or eofError indicating there was a problem

func (x *yyLex) readString() (token int, value py.Object) {

// Quick check for this being a string

if len(x.line) == 0 {

return eof, nil

}

r0 := x.line[0]

r1 := byte(0)

r2 := byte(0)

if len(x.line) >= 2 {

r1 = x.line[1]

if len(x.line) >= 3 {

r2 = x.line[2]

}

rawString := false // whether we are parsing a r"" string

byteString := false // whether we are parsing a b"" string

// u"" strings are just normal strings so we ignore that qualifier

// Start of string

if r0 == '\'' || r0 == '"' {

goto found

}

// Or start of r"" u"" b""

if (r0 == 'r' || r0 == 'R') && (r1 == '\'' || r1 == '"') {

rawString = true

x.cut(1)

goto found

}

if (r0 == 'b' || r0 == 'B') && (r1 == '\'' || r1 == '"') {

byteString = true

x.cut(1)

goto found

}

if (r0 == 'u' || r0 == 'U') && (r1 == '\'' || r1 == '"') {

x.cut(1)

goto found

}

// Or start of br"" Br"" bR"" BR"" rb"" rB"" Rb"" RB""

if (r0 == 'r' || r0 == 'R') && (r1 == 'b' || r1 == 'B') && (r2 == '\'' || r2 == '"') {

rawString = true

byteString = true

x.cut(2)

goto found

}

if (r0 == 'b' || r0 == 'B') && (r1 == 'r' || r1 == 'R') && (r2 == '\'' || r2 == '"') {

rawString = true

byteString = true

x.cut(2)

goto found

}

return eof, nil

found:

multiLineString := false

stringEnd := ""

// Use x.rawString and x.byteString flags

// Parse "x" """x""" 'x' '''x'''

if strings.HasPrefix(x.line, `"""`) {

stringEnd = `"""`

x.cut(3)

multiLineString = true

} else if strings.HasPrefix(x.line, `'''`) {

stringEnd = `'''`

x.cut(3)

multiLineString = true

} else if strings.HasPrefix(x.line, `"`) {

stringEnd = `"`

x.cut(1)

} else if strings.HasPrefix(x.line, `'`) {

stringEnd = `'`

x.cut(1)

} else {

panic("Bad string start")

}

buf := new(bytes.Buffer)

for {

escape := false

for i, c := range x.line {

if escape {

// Continuation line - remove \ then continue

if c == '\n' {

buf.Truncate(buf.Len() - 1)

goto readMore

}

_, _ = buf.WriteRune(c)

escape = false

} else {

if strings.HasPrefix(x.line[i:], stringEnd) {

x.cut(i + len(stringEnd))

goto foundEndOfString

}

if c == '\\' {

escape = true

}

if !multiLineString && c == '\n' {

break

}

_, _ = buf.WriteRune(c)

}

if !multiLineString {

x.SyntaxErrorf("EOL while scanning string literal")

return eofError, nil

}

if x.eof {

if multiLineString {

x.SyntaxErrorf("EOF while scanning triple-quoted string literal")

} else {

x.SyntaxErrorf("EOL while scanning string literal")

}

return eofError, nil

}

x.refill()

}

foundEndOfString:

if !rawString {

var err error

buf, err = DecodeEscape(buf, byteString)

if err != nil {

x.SyntaxErrorf("Decode error: %v", err)

return eofError, nil

}

if byteString {

return STRING, py.Bytes(buf.Bytes())

}

return STRING, py.String(buf.String())

}

// The parser calls this method on a parse error.

func (x *yyLex) Error(s string) {

x.error = true

if yyDebug >= 1 {

log.Printf("Parse error: %s", s)

log.Printf("Parse buffer %q", x.line)

log.Printf("State %#v", x)

}

// The parser calls this method on a parse error.

func (x *yyLex) SyntaxError(s string) {

x.errorString = s

x.Error(s)

}

// Call this to write formatted errors

func (x *yyLex) SyntaxErrorf(format string, a ...interface{}) {

x.SyntaxError(fmt.Sprintf(format, a...))

}

// Returns an python error for the current yyLex

func (x *yyLex) ErrorReturn() error {

if x.error {

if x.errorString == "" {

if x.eof {

x.errorString = "unexpected EOF while parsing"

} else {

x.errorString = "invalid syntax"

}

return py.ExceptionNewf(py.SyntaxError, "%s", x.errorString)

}

return nil

}

// Set the debug level 0 = off, 4 = max

func SetDebug(level int) {

yyDebug = level

}

// Parse a file

func Parse(in io.Reader, filename string, mode py.CompileMode) (mod ast.Mod, err error) {

lex, err := NewLex(in, filename, mode)

if err != nil {

return nil, err

}

defer func() {

if r := recover(); r != nil {

err = py.MakeSyntaxError(r, filename, lex.pos.Lineno, lex.pos.ColOffset, lex.lastLine)

}

}()

yyParse(lex)

err = lex.ErrorReturn()

if err != nil {

err = py.MakeSyntaxError(err, filename, lex.pos.Lineno, lex.pos.ColOffset, lex.lastLine)

}

return lex.mod, err

}

// Parse a string

func ParseString(in string, mode py.CompileMode) (ast.Ast, error) {

return Parse(bytes.NewBufferString(in), "<string>", mode)

}

// Lex a file only, returning a sequence of tokens

func Lex(in io.Reader, filename string, mode py.CompileMode) (lts LexTokens, err error) {

lex, err := NewLex(in, filename, mode)

if err != nil {

return nil, err

}

defer func() {

if r := recover(); r != nil {

err = py.MakeSyntaxError(r, filename, lex.pos.Lineno, lex.pos.ColOffset, lex.lastLine)

}

}()

yylval := yySymType{}

for {

ret := lex.Lex(&yylval)

if ret == eof {

break

}

lt := newLexToken(ret, &yylval)

lts = append(lts, lt)

}

err = lex.ErrorReturn()

if err != nil {

err = py.MakeSyntaxError(err, filename, lex.pos.Lineno, lex.pos.ColOffset, lex.lastLine)

}

return

}

// Lex a string

func LexString(in string, mode py.CompileMode) (lts LexTokens, err error) {

return Lex(bytes.NewBufferString(in), "<string>", mode)

}

gpython/parser/lexer.go at main · go-python/gpython · GitHub

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