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unmarshal.go
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unmarshal.go
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// Copyright (C) 2020 Storj Labs, Inc.
// See LICENSE for copying information.
package strictcsv
import (
"bytes"
"encoding"
"encoding/csv"
"errors"
"io"
"reflect"
"sort"
"strconv"
"strings"
)
var (
unmarshalCSVType = reflect.TypeOf((*Unmarshaler)(nil)).Elem()
unmarshalTextType = reflect.TypeOf((*encoding.TextUnmarshaler)(nil)).Elem()
)
// Unmarshaler is used to implement customized CSV field unmarshaling.
type Unmarshaler interface {
UnmarshalCSV(s string) error
}
// Unmarshal unmarshals an object from CSV bytes.
func Unmarshal(b []byte, obj interface{}) error {
return Read(bytes.NewReader(b), obj)
}
// UnmarshalString unmarshals an object from a CSV string.
func UnmarshalString(s string, obj interface{}) error {
return Read(strings.NewReader(s), obj)
}
// Read unmarshals an object from a CSV reader.
func Read(r io.Reader, obj interface{}) error {
pv := reflect.ValueOf(obj)
switch {
case pv == reflect.Value{}:
return Error.New("destination (%T) cannot be nil", obj)
case pv.Kind() != reflect.Ptr:
return Error.New("destination (%T) must be a non-nil pointer to a struct or slice of structs", obj)
case pv.IsNil():
return Error.New("destination (%T) cannot be nil", obj)
}
isSlice := false
isPtr := false
v := pv.Elem()
t := v.Type()
if t.Kind() == reflect.Slice {
isSlice = true
t = t.Elem()
}
if t.Kind() == reflect.Ptr {
isPtr = true
t = t.Elem()
}
if t.Kind() != reflect.Struct {
return Error.New("destination (%T) must be a non-nil pointer to a struct or slice of structs", obj)
}
settableFields, err := getSettableFields(t)
if err != nil {
return err
}
csvr := csv.NewReader(r)
headers, err := csvr.Read()
if err != nil {
return Error.New("unable to read CSV headers: %v", err)
}
unmatchedFields := make(map[string]struct{}, len(settableFields))
for header := range settableFields {
unmatchedFields[header] = struct{}{}
}
fields := make([]settableField, 0, len(headers))
for _, header := range headers {
field, ok := settableFields[header]
if !ok {
return Error.New("CSV header %q is not mapped to struct field", header)
}
if _, ok := unmatchedFields[header]; !ok {
return Error.New("CSV header %q is duplicated", header)
}
delete(unmatchedFields, header)
fields = append(fields, field)
}
if len(unmatchedFields) > 0 {
unmatchedHeaders := make([]string, 0, len(unmatchedFields))
for header := range unmatchedFields {
unmatchedHeaders = append(unmatchedHeaders, header)
}
sort.Strings(unmatchedHeaders)
return Error.New("field headers %q missing from CSV", unmatchedHeaders)
}
if !isSlice {
record, err := csvr.Read()
if err != nil {
return Error.New("unable to read CSV record: %v", err)
}
if isPtr {
v = reflect.New(t).Elem()
pv.Elem().Set(v.Addr())
}
return setFields(fields, record, v)
}
for {
record, err := csvr.Read()
if err != nil {
if errors.Is(err, io.EOF) {
pv.Elem().Set(v)
return nil
}
return Error.New("unable to read CSV record: %v", err)
}
e := reflect.New(t).Elem()
// This length check is purely defensive since the CSV reader already
// handles this.
if len(record) != len(fields) {
return Error.New("expected %d columns; got %d", len(fields), len(record))
}
if err := setFields(fields, record, e); err != nil {
return err
}
if isPtr {
v = reflect.Append(v, e.Addr())
} else {
v = reflect.Append(v, e)
}
}
}
type settableField struct {
Name string
Index []int
Setter func(v reflect.Value, s string) error
}
type settableFields map[string]settableField
func getSettableFields(t reflect.Type) (settableFields, error) {
fields := make(settableFields)
for i := 0; i < t.NumField(); i++ {
field := t.Field(i)
header := field.Tag.Get("csv")
if header == "" {
return nil, Error.New("field %q missing csv tag", field.Name)
}
if header == "-" {
continue
}
var setter func(reflect.Value, string) error
switch {
case field.Type.Implements(unmarshalCSVType):
setter = setUnmarshalCSVValue
case reflect.PtrTo(field.Type).Implements(unmarshalCSVType):
setter = setUnmarshalCSVValue
case field.Type.Implements(unmarshalTextType):
setter = setUnmarshalTextValue
case reflect.PtrTo(field.Type).Implements(unmarshalTextType):
setter = setUnmarshalTextValue
default:
ft := field.Type
if ft.Kind() == reflect.Ptr {
ft = ft.Elem()
}
switch ft.Kind() {
case reflect.String:
setter = setStringValue
case reflect.Bool:
setter = setBoolValue
case reflect.Int64:
setter = setInt64Value
case reflect.Uint64:
setter = setUint64Value
case reflect.Float64:
setter = setFloat64Value
default:
return nil, Error.New("field %q has unsupported type %s", field.Name, field.Type.String())
}
}
if field.Type.Kind() == reflect.Ptr {
setter = setPointerValue(setter)
}
fields[header] = settableField{
Name: field.Name,
Index: field.Index,
Setter: setter,
}
}
return fields, nil
}
func setFields(fields []settableField, record []string, v reflect.Value) error {
for i, field := range fields {
if err := field.Setter(v.FieldByIndex(field.Index), record[i]); err != nil {
return Error.New("unable to unmarshal field %q: %v", field.Name, err)
}
}
return nil
}
func setPointerValue(setter func(reflect.Value, string) error) func(reflect.Value, string) error {
return func(v reflect.Value, s string) error {
if s == "" {
return nil
}
n := reflect.New(v.Type().Elem())
if err := setter(n.Elem(), s); err != nil {
return err
}
v.Set(n)
return nil
}
}
func setStringValue(v reflect.Value, s string) error {
v.Set(reflect.ValueOf(s).Convert(v.Type()))
return nil
}
func setBoolValue(v reflect.Value, s string) error {
value, err := strconv.ParseBool(s)
if err != nil {
return err
}
v.Set(reflect.ValueOf(value).Convert(v.Type()))
return nil
}
func setInt64Value(v reflect.Value, s string) error {
value, err := strconv.ParseInt(s, 10, 64)
if err != nil {
return err
}
v.Set(reflect.ValueOf(value).Convert(v.Type()))
return nil
}
func setUint64Value(v reflect.Value, s string) error {
value, err := strconv.ParseUint(s, 10, 64)
if err != nil {
return err
}
v.Set(reflect.ValueOf(value).Convert(v.Type()))
return nil
}
func setFloat64Value(v reflect.Value, s string) error {
value, err := strconv.ParseFloat(s, 64)
if err != nil {
return err
}
v.Set(reflect.ValueOf(value).Convert(v.Type()))
return nil
}
func setUnmarshalCSVValue(v reflect.Value, s string) error {
value := v.Addr().Interface().(Unmarshaler)
return value.UnmarshalCSV(s)
}
func setUnmarshalTextValue(v reflect.Value, s string) error {
value := v.Addr().Interface().(encoding.TextUnmarshaler)
return value.UnmarshalText([]byte(s))
}