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// Package gcfg reads "gitconfig-like" text-based configuration files with
// "name=value" pairs grouped into sections (gcfg files).
// Support for writing gcfg files may be added later.
//
// See ReadInto and the examples to get an idea of how to use it.
//
// This package is still a work in progress, and both the supported syntax and
// the API is subject to change.
//
// The syntax is based on that used by git config:
// http://git-scm.com/docs/git-config#_syntax .
// Note that the gcfg syntax may diverge from that of git config in the future
// to a limited degree.
// Currently planned differences (apart from TODOs listed below) are:
// - gcfg files must use UTF-8 encoding and must not contain the 0 byte
// - include and "path" type is not supported at the package level
// - `[sec.sub]` format is not allowed (deprecated in gitconfig)
// - `[sec ""]` is not allowed
// - `[sec]` is the equivalent (section name "sec" and empty subsection name)
// - within a single file, definitions must be consecutive for each:
// - section: '[secA]' -> '[secB]' -> '[secA]' is an error
// - subsection: '[sec "A"]' -> '[sec "B"]' -> '[sec "A"]' is an error
// - multivalued variable: 'multi=a' -> 'other=x' -> 'multi=b' is an error
//
// The package may be usable for handling some of the various "INI file" formats
// used by some programs and libraries, but achieving or maintaining
// compatibility with any of those is not a primary concern.
//
// TODO:
// - docs
// - format spec
// - parsing
// - define internal representation structure
// - support multi-value variables
// - non-regexp based parser
// - support partially quoted strings
// - support escaping in strings
// - support multiple inputs (readers, strings, files)
// - support declaring encoding (?)
// - support pointer fields
// - scanEnum
// - should use longest match (?)
// - support matching on unique prefix (?)
// - writing gcfg files
// - error handling
// - include error context
// - more helpful error messages
// - error types / codes?
// - limit input size?
//
package gcfg
import (
"bufio"
"errors"
"fmt"
"io"
"os"
"reflect"
"regexp"
"strings"
)
var (
reCmnt = regexp.MustCompile(`^([^;#"]*)[;#].*$`)
reCmntQ = regexp.MustCompile(`^([^;#"]*"[^"]*"[^;#"]*)[;#].*$`)
reBlank = regexp.MustCompile(`^\s*$`)
reSect = regexp.MustCompile(`^\s*\[\s*([^"\s]*)\s*\]\s*$`)
reSectSub = regexp.MustCompile(`^\s*\[\s*([^"\s]*)\s*"([^"]+)"\s*\]\s*$`)
reVar = regexp.MustCompile(`^\s*([^"=\s]+)\s*=\s*([^"\s]*)\s*$`)
reVarQ = regexp.MustCompile(`^\s*([^"=\s]+)\s*=\s*"([^"\n\\]*)"\s*$`)
reVarDflt = regexp.MustCompile(`^\s*\b(.*)\b\s*$`)
)
const (
// Default value string in case a value for a variable isn't provided.
defaultValue = "true"
)
type gbool bool
var gboolValues = map[string]interface{}{
"true": true, "yes": true, "on": true, "1": true,
"false": false, "no": false, "off": false, "0": false}
func (b *gbool) Scan(state fmt.ScanState, verb rune) error {
v, err := scanEnum(state, gboolValues, true)
if err != nil {
return err
}
bb, _ := v.(bool) // cannot be non-bool
*b = gbool(bb)
return nil
}
func fieldFold(v reflect.Value, name string) reflect.Value {
n := strings.Replace(name, "-", "_", -1)
return v.FieldByNameFunc(func(fieldName string) bool {
return strings.EqualFold(n, fieldName)
})
}
func set(cfg interface{}, sect, sub, name, value string) error {
vDest := reflect.ValueOf(cfg).Elem()
vSect := fieldFold(vDest, sect)
if vSect.Kind() == reflect.Map {
if vSect.IsNil() {
vSect.Set(reflect.MakeMap(vSect.Type()))
}
k := reflect.ValueOf(sub)
pv := vSect.MapIndex(k)
if !pv.IsValid() {
vType := vSect.Type().Elem().Elem()
pv = reflect.New(vType)
vSect.SetMapIndex(k, pv)
}
vSect = pv.Elem()
} else if sub != "" {
return fmt.Errorf("expected map; section %q subsection %q", sect, sub)
}
vName := fieldFold(vSect, name)
vAddr := vName.Addr().Interface()
switch v := vAddr.(type) {
case *string:
*v = value
return nil
case *bool:
vAddr = (*gbool)(v)
}
// attempt to read an extra rune to make sure the value is consumed
var r rune
n, err := fmt.Sscanf(value, "%v%c", vAddr, &r)
switch {
case n < 1 || n == 1 && err != io.EOF:
return fmt.Errorf("failed to parse %q as %#v: parse error %v", value,
vName.Type(), err)
case n > 1:
return fmt.Errorf("failed to parse %q as %#v: extra characters", value,
vName.Type())
case n == 1 && err == io.EOF:
return nil
}
panic("never reached")
}
// ReadInto reads gcfg formatted data from reader and sets the values into the
// corresponding fields in config.
//
// Config must be a pointer to a struct.
// Each section corresponds to a struct field in config, and each variable in a
// section corresponds to a data field in the section struct.
// The name of the field must match the name of the section or variable,
// ignoring case.
// Hyphens in variable names correspond to underscores in section or field
// names.
//
// For sections with subsections, the corresponding field in config must be a
// map, rather than a struct, with string keys and pointer-to-struct values.
// Values for subsection variables are stored in the map with the subsection
// name used as the map key.
// (Note that unlike section and variable names, subsection names are case
// sensitive.)
// When using a map, and there is a section with the same section name but
// without a subsection name, its values are stored with the empty string used
// as the key.
//
// The section structs in the config struct may contain arbitrary types.
// For string fields, the (unquoted and unescaped) value string is assigned to
// the field.
// For bool fields, the field is set to true if the value is "true", "yes", "on"
// or "1", and set to false if the value is "false", "no", "off" or "0",
// ignoring case.
// For all other types, fmt.Sscanf is used to parse the value and set it to the
// field.
// This means that built-in Go types are parseable using the standard format,
// and any user-defined type is parseable if it implements the fmt.Scanner
// interface.
//
// See ReadStringInto for examples.
//
func ReadInto(config interface{}, reader io.Reader) error {
r := bufio.NewReader(reader)
sect := (*string)(nil)
sectsub := ""
for line := 1; true; line++ {
l, pre, err := r.ReadLine()
if err != nil && err != io.EOF {
return err
} else if pre {
return errors.New("line too long")
}
// exclude comments
if c := reCmnt.FindSubmatch(l); c != nil {
l = c[1]
} else if c := reCmntQ.FindSubmatch(l); c != nil {
l = c[1]
}
if !reBlank.Match(l) {
// "switch" based on line contents
if sec := reSect.FindSubmatch(l); sec != nil {
strsec := string(sec[1])
sect, sectsub = &strsec, ""
} else if sec := reSectSub.FindSubmatch(l); sec != nil {
strsec := string(sec[1])
strsub := string(sec[2])
if strsub == "" {
return errors.New("empty subsection not allowed")
}
sect, sectsub = &strsec, strsub
} else if v, vq, vd := reVar.FindSubmatch(l),
reVarQ.FindSubmatch(l), reVarDflt.FindSubmatch(l); //
v != nil || vq != nil || vd != nil {
if sect == nil {
return errors.New("no section")
}
var name, value string
if v != nil {
name, value = string(v[1]), string(v[2])
} else if vq != nil {
name, value = string(vq[1]), string(vq[2])
} else { // vd != nil
name, value = string(vd[1]), defaultValue
}
err := set(config, *sect, sectsub, name, value)
if err != nil {
return err
}
} else {
return fmt.Errorf("invalid line %q", string(l))
}
}
if err == io.EOF {
break
}
}
return nil
}
// ReadStringInto reads gcfg formatted data from str and sets the values into
// the corresponding fields in config.
// See ReadInto(config, reader) for a detailed description of how values are
// parsed and set into config.
func ReadStringInto(config interface{}, str string) error {
r := strings.NewReader(str)
return ReadInto(config, r)
}
// ReadFileInto reads gcfg formatted data from the file filename and sets the
// values into the corresponding fields in config.
// See ReadInto(config, reader) for a detailed description of how values are
// parsed and set into config.
func ReadFileInto(config interface{}, filename string) error {
f, err := os.Open(filename)
if err != nil {
return err
}
defer f.Close()
return ReadInto(config, f)
}