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tokenizer.go
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670 lines (634 loc) · 14.6 KB
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package goxpath
import (
"fmt"
"io"
"strconv"
"strings"
"unicode"
)
type tokenType int
const (
// tokAny contains any token.
tokAny tokenType = iota
// tokString contains any characters including whitespace.
tokString
// tokVarname represents a variable name.
tokVarname
// tokNumber represents a float64.
tokNumber
// tokOperator contains a single or double letter operator or path
// separator.
tokOperator
// tokOpenParen is an opening parenthesis (.
tokOpenParen
// tokCloseParen is a closing parenthesis ).
tokCloseParen
// tokOpenBracket is an opening bracket [.
tokOpenBracket
// tokCloseBracket is a closing bracket ].
tokCloseBracket
// tokQName is a QName (which might contain one colon).
tokQName
// tokComma represents a comma
tokComma
// tokDoubleColon represents a word with two colons a the end (axis for
// example)
tokDoubleColon
// tokOpenBrace is an opening curly brace {.
tokOpenBrace
// tokCloseBrace is a closing curly brace }.
tokCloseBrace
// tokEQName is a URIQualifiedName: Q{namespace}localname.
tokEQName
)
func (tt tokenType) String() string {
switch tt {
case tokAny:
return "Any token"
case tokString:
return "string"
case tokVarname:
return "variable name"
case tokNumber:
return "number"
case tokOperator:
return "operator"
case tokOpenParen:
return "open paren"
case tokCloseParen:
return "close paren"
case tokOpenBracket:
return "open bracket"
case tokCloseBracket:
return "close bracket"
case tokQName:
return "QName"
case tokComma:
return "comma"
case tokOpenBrace:
return "open brace"
case tokCloseBrace:
return "close brace"
case tokEQName:
return "EQName"
}
return "--"
}
type token struct {
Value any
Typ tokenType
}
func (tok *token) isNCName() bool {
if tok.Typ != tokQName {
return false
}
tokAsString := tok.Value.(string)
return !strings.ContainsRune(tokAsString, ':')
}
type tokens []token
func (toks tokens) String() string {
var str []string
for _, t := range toks {
str = append(str, t.String())
}
return strings.Join(str, " ")
}
func (tok token) String() string {
switch tok.Typ {
case tokVarname:
return "$" + tok.Value.(string)
case tokOpenParen:
return "("
case tokCloseParen:
return ")"
case tokOpenBracket:
return "["
case tokCloseBracket:
return "]"
case tokOpenBrace:
return "{"
case tokCloseBrace:
return "}"
}
switch v := tok.Value.(type) {
case string:
return v
case float64:
return fmt.Sprintf("%f", v)
default:
fmt.Printf("v %#v\n", v)
return "***"
}
}
// Tokenlist represents units of XPath language elements.
type Tokenlist struct {
pos int
toks tokens
attributeMode bool // for Name Test
}
func (tl *Tokenlist) nexttokIsTyp(typ tokenType) bool {
tok, err := tl.peek()
if err != nil {
return false
}
return tok.Typ == typ
}
func (tl *Tokenlist) readIfTokenFollow(toks []token) bool {
pos := tl.pos
savepos := tl.pos
for _, tok := range toks {
peekTok, err := tl.peek()
if err != nil {
tl.pos = savepos
return false
}
if peekTok.Value == tok.Value && peekTok.Typ == tok.Typ {
pos++
} else {
tl.pos = savepos
return false
}
tl.read()
}
return true
}
// nexttokIsValue looks at the next token and returns true if the value matches.
// Does not move the pointer forward.
func (tl *Tokenlist) nexttokIsValue(val string) bool {
tok, err := tl.peek()
if err != nil {
return false
}
if str, ok := tok.Value.(string); ok {
return str == val
}
return false
}
func (tl *Tokenlist) readNexttokIfIsOneOfValue(val []string) (string, bool) {
tok, err := tl.peek()
if err != nil {
return "", false
}
if str, ok := tok.Value.(string); ok {
for _, v := range val {
if str == v {
tl.read()
return v, true
}
}
}
return "", false
}
func (tl *Tokenlist) readNexttokIfIsOneOfValueAndType(val []string, typ tokenType) (string, bool) {
tok, err := tl.peek()
if err != nil {
return "", false
}
if tok.Typ != typ {
return fmt.Sprint(tok.Value), false
}
if str, ok := tok.Value.(string); ok {
for _, v := range val {
if str == v {
tl.read()
return v, true
}
}
}
return "", false
}
func (tl *Tokenlist) peek() (*token, error) {
if len(tl.toks) == tl.pos {
return nil, io.EOF
}
return &tl.toks[tl.pos], nil
}
func (tl *Tokenlist) read() (*token, error) {
if len(tl.toks) == tl.pos {
return nil, io.EOF
}
tl.pos++
return &tl.toks[tl.pos-1], nil
}
func (tl *Tokenlist) unread() error {
tl.pos--
return nil
}
// skipType reads the next token and returns an error if the token type does not
// match.
func (tl *Tokenlist) skipType(typ tokenType) error {
var val *token
var err error
if val, err = tl.read(); err != nil {
return err
}
if val.Typ != typ {
return fmt.Errorf("expect %s, got %s", typ, val.Typ)
}
return nil
}
func (tl *Tokenlist) skipNCName(name string) error {
var val *token
var err error
if val, err = tl.read(); err != nil {
return err
}
if !val.isNCName() {
return fmt.Errorf("expect %s, got %s", name, val.Typ)
}
if str, ok := val.Value.(string); ok && str != name {
return fmt.Errorf("expect %s, got %s", name, str)
}
return nil
}
// getNum reads a numeric literal and returns the appropriately typed value:
// - IntegerLiteral (digits only) → int
// - DecimalLiteral (digits with '.') → XSDecimal
// - DoubleLiteral (has 'e'/'E') → XSDouble
func getNum(sr *strings.Reader) any {
var buf []byte
hasExp := false
hasDot := false
for {
r, _, err := sr.ReadRune()
if err != nil {
break
}
if r >= '0' && r <= '9' {
buf = append(buf, byte(r))
} else if r == '.' {
hasDot = true
buf = append(buf, byte(r))
} else if (r == 'e' || r == 'E') && !hasExp {
buf = append(buf, byte(r))
hasExp = true
} else if (r == '+' || r == '-') && hasExp && len(buf) > 0 && (buf[len(buf)-1] == 'e' || buf[len(buf)-1] == 'E') {
buf = append(buf, byte(r))
} else {
sr.UnreadRune()
break
}
}
s := string(buf)
f, _ := strconv.ParseFloat(s, 64)
if hasExp {
return XSDouble(f)
}
if hasDot {
return XSDecimal(f)
}
// Integer literal — parse as int64 to preserve precision
if i, err := strconv.ParseInt(s, 10, 64); err == nil {
return int(i)
}
// Overflow — store as XSDecimal to preserve the value as best as possible
return XSDecimal(f)
}
// getNumWithPrefix parses a number literal starting with a given prefix (e.g., ".").
func getNumWithPrefix(prefix string, sr *strings.Reader) any {
var buf []byte
buf = append(buf, []byte(prefix)...)
hasExp := false
hasDot := strings.Contains(prefix, ".")
for {
r, _, err := sr.ReadRune()
if err != nil {
break
}
if r >= '0' && r <= '9' {
buf = append(buf, byte(r))
} else if r == '.' && !hasDot {
hasDot = true
buf = append(buf, byte(r))
} else if (r == 'e' || r == 'E') && !hasExp {
buf = append(buf, byte(r))
hasExp = true
} else if (r == '+' || r == '-') && hasExp && len(buf) > 0 && (buf[len(buf)-1] == 'e' || buf[len(buf)-1] == 'E') {
buf = append(buf, byte(r))
} else {
sr.UnreadRune()
break
}
}
s := string(buf)
f, _ := strconv.ParseFloat(s, 64)
if hasExp {
return XSDouble(f)
}
if hasDot {
return XSDecimal(f)
}
if i, err := strconv.Atoi(s); err == nil {
return i
}
return int(f)
}
// getQName reads until any non QName rune is found.
func getQName(sr *strings.Reader) (string, error) {
var word []rune
var hasColon bool
for {
r, _, err := sr.ReadRune()
if err == io.EOF {
break
}
if err != nil {
return "", err
}
if unicode.IsLetter(r) || unicode.IsDigit(r) || r == '_' || r == '-' || r == '.' || r == '·' || r == '‿' || r == '⁀' {
word = append(word, r)
} else if r == ':' {
if hasColon {
sr.UnreadRune()
break
}
word = append(word, r)
hasColon = true
} else {
sr.UnreadRune()
break
}
}
return string(word), nil
}
// getEQName reads the rest of an EQName after "Q{" has been consumed.
// It reads the namespace URI up to "}", then the local name.
// Returns "namespace}localname" as the token value.
func getEQName(sr *strings.Reader) (string, error) {
var ns []rune
for {
r, _, err := sr.ReadRune()
if err != nil {
return "", fmt.Errorf("unterminated Q{} EQName")
}
if r == '}' {
break
}
ns = append(ns, r)
}
localName, err := getQName(sr)
if err != nil {
return "", err
}
if localName == "" {
return "", fmt.Errorf("missing local name in Q{%s}", string(ns))
}
return string(ns) + "}" + localName, nil
}
func getDelimitedString(sr *strings.Reader) (string, error) {
var str []rune
delim, _, err := sr.ReadRune()
if err != nil {
return "", err
}
for {
r, _, err := sr.ReadRune()
if err == io.EOF {
break
}
if err != nil {
return "", err
}
if r == delim {
// XPath escaped delimiter: "" → " or '' → '
next, _, err := sr.ReadRune()
if err == nil && next == delim {
str = append(str, delim)
continue
}
if err == nil {
sr.UnreadRune()
}
break
} else {
str = append(str, r)
}
}
return string(str), err
}
func getComment(sr *strings.Reader) (string, error) {
lvl := 1
var this, next rune
var err error
var comment []rune
for {
if this, _, err = sr.ReadRune(); err != nil {
if err == io.EOF {
// todo error handling
}
return "", err
}
if next, _, err = sr.ReadRune(); err != nil {
if err == io.EOF {
// todo error handling
}
return "", err
}
if this == ':' && next == ')' {
lvl--
if lvl == 0 {
break
}
}
if this == '(' && next == ':' {
lvl++
}
comment = append(comment, this)
if next == ':' || next == '(' {
sr.UnreadRune()
} else {
comment = append(comment, next)
}
}
return string(comment), nil
}
func stringToTokenlist(str string) (*Tokenlist, error) {
var tokens []token
sr := strings.NewReader(str)
for {
r, _, err := sr.ReadRune()
if err == io.EOF {
break
}
if err != nil {
break
}
if '0' <= r && r <= '9' {
sr.UnreadRune()
tokens = append(tokens, token{getNum(sr), tokNumber})
} else if r == '.' {
nextRune, _, err := sr.ReadRune()
if err == io.EOF {
tokens = append(tokens, token{".", tokOperator})
break
}
if err != nil {
return nil, err
}
if '0' <= nextRune && nextRune <= '9' {
// Put back the digit, then parse number starting with "."
sr.UnreadRune()
tokens = append(tokens, token{getNumWithPrefix(".", sr), tokNumber})
} else if nextRune == '.' {
tokens = append(tokens, token{"..", tokOperator})
} else {
sr.UnreadRune()
tokens = append(tokens, token{".", tokOperator})
}
} else if r == '+' || r == '-' || r == '*' || r == '?' || r == '@' || r == '#' {
tokens = append(tokens, token{string(r), tokOperator})
} else if r == '=' {
nextRune, _, err := sr.ReadRune()
if err == io.EOF {
tokens = append(tokens, token{"=", tokOperator})
break
}
if err != nil {
return nil, err
}
if nextRune == '>' {
tokens = append(tokens, token{"=>", tokOperator})
} else {
tokens = append(tokens, token{"=", tokOperator})
sr.UnreadRune()
}
} else if r == '|' {
nextRune, _, err := sr.ReadRune()
if err == io.EOF {
tokens = append(tokens, token{"|", tokOperator})
break
}
if err != nil {
return nil, err
}
if nextRune == '|' {
tokens = append(tokens, token{"||", tokOperator})
} else {
tokens = append(tokens, token{"|", tokOperator})
sr.UnreadRune()
}
} else if r == ',' {
tokens = append(tokens, token{string(r), tokComma})
} else if r == '>' || r == '<' {
nextRune, _, err := sr.ReadRune()
if err != nil {
return nil, err
}
if nextRune == '=' || nextRune == r {
tokens = append(tokens, token{string(r) + string(nextRune), tokOperator})
} else {
tokens = append(tokens, token{string(r), tokOperator})
sr.UnreadRune()
}
} else if r == '!' {
nextRune, _, err := sr.ReadRune()
if err != nil {
// standalone ! at end of input
tokens = append(tokens, token{"!", tokOperator})
break
}
if nextRune == '=' {
tokens = append(tokens, token{"!=", tokOperator})
} else {
tokens = append(tokens, token{"!", tokOperator})
sr.UnreadRune()
}
} else if r == '/' || r == ':' {
nextRune, _, err := sr.ReadRune()
if err == io.EOF {
tokens = append(tokens, token{string(r), tokOperator})
break
}
if err != nil {
return nil, err
}
if nextRune == r {
tokens = append(tokens, token{string(r) + string(r), tokOperator})
} else {
tokens = append(tokens, token{string(r), tokOperator})
sr.UnreadRune()
}
} else if r == '[' {
tokens = append(tokens, token{r, tokOpenBracket})
} else if r == ']' {
tokens = append(tokens, token{r, tokCloseBracket})
} else if r == '$' {
qname, err := getQName(sr)
if err != nil {
return nil, err
}
tokens = append(tokens, token{qname, tokVarname})
} else if unicode.IsSpace(r) {
// ignore whitespace
} else if unicode.IsLetter(r) {
sr.UnreadRune()
word, err := getQName(sr)
if err != nil {
return nil, err
}
// Check for EQName: Q{namespace}localname
if word == "Q" {
nextRune, _, err := sr.ReadRune()
if err == nil && nextRune == '{' {
eqname, err := getEQName(sr)
if err != nil {
return nil, err
}
tokens = append(tokens, token{eqname, tokEQName})
continue
}
if err == nil {
sr.UnreadRune()
}
}
nextRune, _, err := sr.ReadRune()
if err == io.EOF {
tokens = append(tokens, token{word, tokQName})
break
}
if nextRune == ':' {
tokens = append(tokens, token{strings.TrimSuffix(word, ":"), tokDoubleColon})
} else {
sr.UnreadRune()
tokens = append(tokens, token{word, tokQName})
}
} else if r == '\'' || r == '"' {
sr.UnreadRune()
str, err := getDelimitedString(sr)
if err != nil {
return nil, err
}
tokens = append(tokens, token{str, tokString})
} else if r == '(' {
nextRune, _, err := sr.ReadRune()
if err == io.EOF {
// what should we do?
return nil, fmt.Errorf("parse error, unbalanced ( at end")
}
if err != nil {
return nil, err
}
if nextRune == ':' {
_, err := getComment(sr)
if err != nil {
return nil, err
}
// comments are ignored
// tokens = append(tokens, token{cmt, TokAny})
} else {
sr.UnreadRune()
tokens = append(tokens, token{r, tokOpenParen})
}
} else if r == ')' {
tokens = append(tokens, token{r, tokCloseParen})
} else if r == '{' {
tokens = append(tokens, token{r, tokOpenBrace})
} else if r == '}' {
tokens = append(tokens, token{r, tokCloseBrace})
} else {
return nil, fmt.Errorf("Invalid char for xpath expression %q", string(r))
}
}
tl := Tokenlist{pos: 0, toks: tokens}
return &tl, nil
}