ref: c67ae1bdeeac3752c2df1fa47a013353b3b508bd
dir: /config/parser.go/
package config
import (
"bufio"
"bytes"
"errors"
"fmt"
"io"
"strings"
)
type configParser struct {
reader *bufio.Reader
lineNum int
currentSection string
currentSubsec string
peeked byte
hasPeeked bool
}
func (p *configParser) parse() (*Config, error) {
cfg := &Config{}
err := p.skipBOM()
if err != nil {
return nil, err
}
for {
ch, err := p.nextChar()
if errors.Is(err, io.EOF) {
break
}
if err != nil {
return nil, err
}
// Skip leading whitespace between entries.
if isWhitespace(ch) {
continue
}
// Comments
if ch == '#' || ch == ';' {
err := p.skipToEOL()
if err != nil && !errors.Is(err, io.EOF) {
return nil, err
}
continue
}
// Section header
if ch == '[' {
err := p.parseSection()
if err != nil {
return nil, fmt.Errorf("furgit: config: line %d: %w", p.lineNum, err)
}
continue
}
// Key-value pair
if isLetter(ch) {
p.unreadChar(ch)
err := p.parseKeyValue(cfg)
if err != nil {
return nil, fmt.Errorf("furgit: config: line %d: %w", p.lineNum, err)
}
continue
}
return nil, fmt.Errorf("furgit: config: line %d: unexpected character %q", p.lineNum, ch)
}
return cfg, nil
}
func (p *configParser) nextChar() (byte, error) {
if p.hasPeeked {
p.hasPeeked = false
return p.peeked, nil
}
ch, err := p.reader.ReadByte()
if err != nil {
return 0, err
}
if ch == '\r' {
next, err := p.reader.ReadByte()
if err == nil && next == '\n' {
ch = '\n'
} else if err == nil {
// Weird but ok
_ = p.reader.UnreadByte()
}
}
if ch == '\n' {
p.lineNum++
}
return ch, nil
}
func (p *configParser) unreadChar(ch byte) {
p.peeked = ch
p.hasPeeked = true
if ch == '\n' && p.lineNum > 1 {
p.lineNum--
}
}
func (p *configParser) skipBOM() error {
first, err := p.reader.ReadByte()
if errors.Is(err, io.EOF) {
return nil
}
if err != nil {
return err
}
if first != 0xef {
_ = p.reader.UnreadByte()
return nil
}
second, err := p.reader.ReadByte()
if err != nil {
if errors.Is(err, io.EOF) {
_ = p.reader.UnreadByte()
return nil
}
return err
}
third, err := p.reader.ReadByte()
if err != nil {
if errors.Is(err, io.EOF) {
_ = p.reader.UnreadByte()
_ = p.reader.UnreadByte()
return nil
}
return err
}
if second == 0xbb && third == 0xbf {
return nil
}
_ = p.reader.UnreadByte()
_ = p.reader.UnreadByte()
_ = p.reader.UnreadByte()
return nil
}
func (p *configParser) skipToEOL() error {
for {
ch, err := p.nextChar()
if err != nil {
return err
}
if ch == '\n' {
return nil
}
}
}
func (p *configParser) parseSection() error {
var name bytes.Buffer
for {
ch, err := p.nextChar()
if err != nil {
return errors.New("unexpected EOF in section header")
}
if ch == ']' {
section := name.String()
if !isValidSection(section) {
return fmt.Errorf("invalid section name: %q", section)
}
p.currentSection = strings.ToLower(section)
p.currentSubsec = ""
return nil
}
if isWhitespace(ch) {
return p.parseExtendedSection(&name)
}
if !isKeyChar(ch) && ch != '.' {
return fmt.Errorf("invalid character in section name: %q", ch)
}
name.WriteByte(toLower(ch))
}
}
func (p *configParser) parseExtendedSection(sectionName *bytes.Buffer) error {
for {
ch, err := p.nextChar()
if err != nil {
return errors.New("unexpected EOF in section header")
}
if !isWhitespace(ch) {
if ch != '"' {
return errors.New("expected quote after section name")
}
break
}
}
var subsec bytes.Buffer
for {
ch, err := p.nextChar()
if err != nil {
return errors.New("unexpected EOF in subsection")
}
if ch == '\n' {
return errors.New("newline in subsection")
}
if ch == '"' {
break
}
if ch == '\\' {
next, err := p.nextChar()
if err != nil {
return errors.New("unexpected EOF after backslash in subsection")
}
if next == '\n' {
return errors.New("newline after backslash in subsection")
}
subsec.WriteByte(next)
} else {
subsec.WriteByte(ch)
}
}
ch, err := p.nextChar()
if err != nil {
return errors.New("unexpected EOF after subsection")
}
if ch != ']' {
return fmt.Errorf("expected ']' after subsection, got %q", ch)
}
section := sectionName.String()
if !isValidSection(section) {
return fmt.Errorf("invalid section name: %q", section)
}
p.currentSection = strings.ToLower(section)
p.currentSubsec = subsec.String()
return nil
}
func (p *configParser) parseKeyValue(cfg *Config) error {
if p.currentSection == "" {
return errors.New("key-value pair before any section header")
}
var key bytes.Buffer
for {
ch, err := p.nextChar()
if errors.Is(err, io.EOF) {
break
}
if err != nil {
return err
}
if ch == '=' || ch == '\n' || isSpace(ch) {
p.unreadChar(ch)
break
}
if !isKeyChar(ch) {
return fmt.Errorf("invalid character in key: %q", ch)
}
key.WriteByte(toLower(ch))
}
keyStr := key.String()
if len(keyStr) == 0 {
return errors.New("empty key name")
}
if !isLetter(keyStr[0]) {
return errors.New("key must start with a letter")
}
for {
ch, err := p.nextChar()
if errors.Is(err, io.EOF) {
cfg.entries = append(cfg.entries, ConfigEntry{
Section: p.currentSection,
Subsection: p.currentSubsec,
Key: keyStr,
Kind: ValueValueless,
Value: "",
})
return nil
}
if err != nil {
return err
}
if ch == '\n' {
cfg.entries = append(cfg.entries, ConfigEntry{
Section: p.currentSection,
Subsection: p.currentSubsec,
Key: keyStr,
Kind: ValueValueless,
Value: "",
})
return nil
}
if ch == '#' || ch == ';' {
err := p.skipToEOL()
if err != nil && !errors.Is(err, io.EOF) {
return err
}
cfg.entries = append(cfg.entries, ConfigEntry{
Section: p.currentSection,
Subsection: p.currentSubsec,
Key: keyStr,
Kind: ValueValueless,
Value: "",
})
return nil
}
if ch == '=' {
break
}
if !isSpace(ch) {
return fmt.Errorf("unexpected character after key: %q", ch)
}
}
value, err := p.parseValue()
if err != nil {
return err
}
cfg.entries = append(cfg.entries, ConfigEntry{
Section: p.currentSection,
Subsection: p.currentSubsec,
Key: keyStr,
Kind: ValueString,
Value: value,
})
return nil
}
func (p *configParser) parseValue() (string, error) {
var (
value bytes.Buffer
inQuote bool
inComment bool
)
trimLen := 0
for {
ch, err := p.nextChar()
if errors.Is(err, io.EOF) {
if inQuote {
return "", errors.New("unexpected EOF in quoted value")
}
if trimLen > 0 {
return truncateAtNUL(value.String()[:trimLen]), nil
}
return truncateAtNUL(value.String()), nil
}
if err != nil {
return "", err
}
if ch == '\n' {
if inQuote {
return "", errors.New("newline in quoted value")
}
if trimLen > 0 {
return truncateAtNUL(value.String()[:trimLen]), nil
}
return truncateAtNUL(value.String()), nil
}
if inComment {
continue
}
if isWhitespace(ch) && !inQuote {
if trimLen == 0 && value.Len() > 0 {
trimLen = value.Len()
}
if value.Len() > 0 {
value.WriteByte(ch)
}
continue
}
if !inQuote && (ch == '#' || ch == ';') {
inComment = true
continue
}
if trimLen > 0 {
trimLen = 0
}
if ch == '\\' {
next, err := p.nextChar()
if errors.Is(err, io.EOF) {
return "", errors.New("unexpected EOF after backslash")
}
if err != nil {
return "", err
}
switch next {
case '\n':
continue
case 'n':
value.WriteByte('\n')
case 't':
value.WriteByte('\t')
case 'b':
value.WriteByte('\b')
case '\\', '"':
value.WriteByte(next)
default:
return "", fmt.Errorf("invalid escape sequence: \\%c", next)
}
continue
}
if ch == '"' {
inQuote = !inQuote
continue
}
value.WriteByte(ch)
}
}