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|
package scfg
import (
"bufio"
"fmt"
"io"
"os"
"strings"
)
// This limits the max block nesting depth to prevent stack overflows.
const maxNestingDepth = 1000
// Load loads a configuration file.
func Load(path string) (Block, error) {
f, err := os.Open(path)
if err != nil {
return nil, err
}
defer f.Close()
return Read(f)
}
// Read parses a configuration file from an io.Reader.
func Read(r io.Reader) (Block, error) {
scanner := bufio.NewScanner(r)
dec := decoder{scanner: scanner}
block, closingBrace, err := dec.readBlock()
if err != nil {
return nil, err
} else if closingBrace {
return nil, fmt.Errorf("line %v: unexpected '}'", dec.lineno)
}
return block, scanner.Err()
}
type decoder struct {
scanner *bufio.Scanner
lineno int
blockDepth int
}
// readBlock reads a block. closingBrace is true if parsing stopped on '}'
// (otherwise, it stopped on Scanner.Scan).
func (dec *decoder) readBlock() (block Block, closingBrace bool, err error) {
dec.blockDepth++
defer func() {
dec.blockDepth--
}()
if dec.blockDepth >= maxNestingDepth {
return nil, false, fmt.Errorf("exceeded max block depth")
}
for dec.scanner.Scan() {
dec.lineno++
l := dec.scanner.Text()
words, err := splitWords(l)
if err != nil {
return nil, false, fmt.Errorf("line %v: %v", dec.lineno, err)
} else if len(words) == 0 {
continue
}
if len(words) == 1 && l[len(l)-1] == '}' {
closingBrace = true
break
}
var d *Directive
if words[len(words)-1] == "{" && l[len(l)-1] == '{' {
words = words[:len(words)-1]
var name string
params := words
if len(words) > 0 {
name, params = words[0], words[1:]
}
startLineno := dec.lineno
childBlock, childClosingBrace, err := dec.readBlock()
if err != nil {
return nil, false, err
} else if !childClosingBrace {
return nil, false, fmt.Errorf("line %v: unterminated block", startLineno)
}
// Allows callers to tell apart "no block" and "empty block"
if childBlock == nil {
childBlock = Block{}
}
d = &Directive{Name: name, Params: params, Children: childBlock, lineno: dec.lineno}
} else {
d = &Directive{Name: words[0], Params: words[1:], lineno: dec.lineno}
}
block = append(block, d)
}
return block, closingBrace, nil
}
func splitWords(l string) ([]string, error) {
var (
words []string
sb strings.Builder
escape bool
quote rune
wantWSP bool
)
for _, ch := range l {
switch {
case escape:
sb.WriteRune(ch)
escape = false
case wantWSP && (ch != ' ' && ch != '\t'):
return words, fmt.Errorf("atom not allowed after quoted string")
case ch == '\\':
escape = true
case quote != 0 && ch == quote:
quote = 0
wantWSP = true
if sb.Len() == 0 {
words = append(words, "")
}
case quote == 0 && len(words) == 0 && sb.Len() == 0 && ch == '#':
return nil, nil
case quote == 0 && (ch == '\'' || ch == '"'):
if sb.Len() > 0 {
return words, fmt.Errorf("quoted string not allowed after atom")
}
quote = ch
case quote == 0 && (ch == ' ' || ch == '\t'):
if sb.Len() > 0 {
words = append(words, sb.String())
}
sb.Reset()
wantWSP = false
default:
sb.WriteRune(ch)
}
}
if quote != 0 {
return words, fmt.Errorf("unterminated quoted string")
}
if sb.Len() > 0 {
words = append(words, sb.String())
}
return words, nil
}
|
