/
csv.go
162 lines (149 loc) · 3.67 KB
/
csv.go
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
package objcsv
import (
"encoding/csv"
"fmt"
"io"
"reflect"
"strconv"
)
func csvError(msg string, args ...interface{}) error {
return fmt.Errorf("CSV: "+msg, args...)
}
// ReadCSV reads from reader r into a pointer to a slice of the destination struct type.
func ReadCSV(r io.Reader, ptrToSlice interface{}) error {
pv := reflect.ValueOf(ptrToSlice)
if pv.IsNil() {
return csvError("expected %v to have a non-nil value", ptrToSlice)
}
if pv.Kind() != reflect.Ptr || pv.Elem().Kind() != reflect.Slice {
return csvError("expected a pointer to a slice, got %v instead", pv.Kind())
}
t := pv.Elem().Type().Elem()
cr := csv.NewReader(r)
didHeader := false
for {
record, err := cr.Read()
if err != nil {
if err == io.EOF {
break
}
return err
}
if !didHeader {
didHeader = true
continue
}
rv, err := recordToValue(record, t)
if err != nil {
return err
}
pv.Elem().Set(reflect.Append(pv.Elem(), rv.Elem()))
}
return nil
}
func recordToValue(ss []string, t reflect.Type) (reflect.Value, error) {
v := reflect.New(t)
if len(ss) != t.NumField() {
return v, csvError("recordToValue: can't decode CSV record to struct (field mismatch): expected %v fields, got %v", t.NumField(), len(ss))
}
for i, s := range ss {
if s == "" {
continue
}
f := t.Field(i)
ft := f.Type.Kind()
fv := v.Elem().Field(i)
typeError := func(msg string, e error) error {
return csvError("%v: type %v, field %v: %v", msg, ft, f.Name, e)
}
switch ft {
case reflect.String:
fv.SetString(s)
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
theInt, err := strconv.ParseInt(s, 10, 64)
if err != nil {
return v, typeError("int", err)
}
fv.SetInt(theInt)
case reflect.Float64:
theFloat, err := strconv.ParseFloat(s, 64)
if err != nil {
return v, typeError("float64", err)
}
fv.SetFloat(theFloat)
case reflect.Bool:
theBool, err := strconv.ParseBool(s)
if err != nil {
return v, typeError("bool", err)
}
fv.SetBool(theBool)
default:
return v, csvError("recordToValue: unsupported type %v in field %v", ft, f.Name)
}
}
return v, nil
}
// WriteCSV writes to writer w from a slice of data records.
func WriteCSV(w io.Writer, slice interface{}) error {
// ensure that d is a slice containing at least some data.
v, err := reflectSlice(slice)
if err != nil {
return err
}
if v.Len() == 0 {
return csvError("data is empty")
}
cw := csv.NewWriter(w)
if err := writeHeader(cw, v.Index(0).Interface()); err != nil {
return err
}
for i := 0; i < v.Len(); i++ {
e := v.Index(i)
if err := writeRow(cw, e.Interface()); err != nil {
return err
}
}
cw.Flush()
return nil
}
func writeHeader(w *csv.Writer, d interface{}) error {
v := reflect.ValueOf(d)
header := make([]string, v.NumField())
for i := 0; i < v.NumField(); i++ {
header[i] = v.Type().Field(i).Name
}
if err := w.Write(header); err != nil {
return err
}
return nil
}
func writeRow(w *csv.Writer, d interface{}) error {
v := reflect.ValueOf(d)
row := make([]string, v.NumField())
for i := 0; i < v.NumField(); i++ {
switch t := v.Field(i).Interface(); t.(type) {
case int:
row[i] = fmt.Sprintf("%d", t)
case float64:
row[i] = fmt.Sprintf("%.2f", t)
case string:
row[i] = fmt.Sprintf("%s", t)
default:
row[i] = fmt.Sprintf("%v", t)
}
}
if err := w.Write(row); err != nil {
return err
}
return nil
}
func reflectSlice(i interface{}) (reflect.Value, error) {
v := reflect.ValueOf(i)
if v.IsNil() {
return v, csvError("expected %v to have a non-nil value", i)
}
if v.Kind() != reflect.Slice {
return v, csvError("expected a slice, got %v instead", v.Kind())
}
return v, nil
}