convert.go
// Modified from: database/sql/convert.go
// Copyright 2011 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
package rel
import (
"database/sql"
"database/sql/driver"
"fmt"
"reflect"
"strconv"
"time"
)
// convertAssign copies to dest the value in src, converting it if possible.
// An error is returned if the copy would result in loss of information.
// dest should be a pointer type.
// dest will be set to zero value if src is nil.
// this function assumes dest will never be nil.
func convertAssign(dest, src interface{}) error {
// Common cases, without reflect.
switch s := src.(type) {
case string:
switch d := dest.(type) {
case *string:
*d = s
return nil
case *[]byte:
*d = []byte(s)
return nil
case *sql.RawBytes:
*d = append((*d)[:0], s...)
return nil
}
case []byte:
switch d := dest.(type) {
case *string:
*d = string(s)
return nil
case *interface{}:
*d = cloneBytes(s)
return nil
case *[]byte:
*d = cloneBytes(s)
return nil
case *sql.RawBytes:
*d = s
return nil
}
case time.Time:
switch d := dest.(type) {
case *time.Time:
*d = s
return nil
case *string:
*d = s.Format(time.RFC3339Nano)
return nil
case *[]byte:
*d = []byte(s.Format(time.RFC3339Nano))
return nil
case *sql.RawBytes:
*d = s.AppendFormat((*d)[:0], time.RFC3339Nano)
return nil
}
case nil:
assignZero(dest)
return nil
}
var sv reflect.Value
switch d := dest.(type) {
case *string:
sv = reflect.ValueOf(src)
switch sv.Kind() {
case reflect.Bool,
reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64,
reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64,
reflect.Float32, reflect.Float64:
if s, ok := asString(src); ok {
*d = s
return nil
}
}
case *[]byte:
sv = reflect.ValueOf(src)
if b, ok := asBytes(nil, sv); ok {
*d = b
return nil
}
case *sql.RawBytes:
sv = reflect.ValueOf(src)
if b, ok := asBytes([]byte(*d)[:0], sv); ok {
*d = sql.RawBytes(b)
return nil
}
case *bool:
bv, err := driver.Bool.ConvertValue(src)
if err == nil {
*d = bv.(bool)
}
return err
case *interface{}:
*d = src
return nil
}
dpv := reflect.ValueOf(dest)
if !sv.IsValid() {
sv = reflect.ValueOf(src)
}
dv := reflect.Indirect(dpv)
if sv.IsValid() && sv.Type().AssignableTo(dv.Type()) {
switch b := src.(type) {
case []byte:
dv.Set(reflect.ValueOf(cloneBytes(b)))
default:
dv.Set(sv)
}
return nil
}
if dv.Kind() == sv.Kind() && sv.Type().ConvertibleTo(dv.Type()) {
dv.Set(sv.Convert(dv.Type()))
return nil
}
// The following conversions use a string value as an intermediate representation
// to convert between various numeric types.
//
// This also allows scanning into user defined types such as "type Int int64".
// For symmetry, also check for string destination types.
if s, ok := asString(src); ok {
switch dv.Kind() {
case reflect.Ptr:
dv.Set(reflect.New(dv.Type().Elem()))
return convertAssign(dv.Interface(), src)
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
i64, err := strconv.ParseInt(s, 10, dv.Type().Bits())
if err != nil {
// The errors that ParseInt returns have concrete type *NumError
err = err.(*strconv.NumError).Err
return fmt.Errorf("converting driver.Value type %T (%q) to a %s: %v", src, s, dv.Kind(), err)
}
dv.SetInt(i64)
return nil
case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
u64, err := strconv.ParseUint(s, 10, dv.Type().Bits())
if err != nil {
// The errors that ParseUint returns have concrete type *NumError
err = err.(*strconv.NumError).Err
return fmt.Errorf("converting driver.Value type %T (%q) to a %s: %v", src, s, dv.Kind(), err)
}
dv.SetUint(u64)
return nil
case reflect.Float32, reflect.Float64:
f64, err := strconv.ParseFloat(s, dv.Type().Bits())
if err != nil {
// The errors that ParseFloat returns have concrete type *NumError
err = err.(*strconv.NumError).Err
return fmt.Errorf("converting driver.Value type %T (%q) to a %s: %v", src, s, dv.Kind(), err)
}
dv.SetFloat(f64)
return nil
case reflect.String:
dv.SetString(s)
return nil
}
}
return fmt.Errorf("unsupported Scan, storing driver.Value type %T into type %T", src, dest)
}
func cloneBytes(b []byte) []byte {
if b == nil {
return nil
}
c := make([]byte, len(b))
copy(c, b)
return c
}
func asString(src interface{}) (string, bool) {
switch v := src.(type) {
case string:
return v, true
case []byte:
return string(v), true
}
rv := reflect.ValueOf(src)
switch rv.Kind() {
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
return strconv.FormatInt(rv.Int(), 10), true
case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
return strconv.FormatUint(rv.Uint(), 10), true
case reflect.Float64:
return strconv.FormatFloat(rv.Float(), 'g', -1, 64), true
case reflect.Float32:
return strconv.FormatFloat(rv.Float(), 'g', -1, 32), true
case reflect.Bool:
return strconv.FormatBool(rv.Bool()), true
}
return "", false
}
func asBytes(buf []byte, rv reflect.Value) (b []byte, ok bool) {
switch rv.Kind() {
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
return strconv.AppendInt(buf, rv.Int(), 10), true
case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
return strconv.AppendUint(buf, rv.Uint(), 10), true
case reflect.Float32:
return strconv.AppendFloat(buf, rv.Float(), 'g', -1, 32), true
case reflect.Float64:
return strconv.AppendFloat(buf, rv.Float(), 'g', -1, 64), true
case reflect.Bool:
return strconv.AppendBool(buf, rv.Bool()), true
case reflect.String:
s := rv.String()
return append(buf, s...), true
}
return
}
func assignZero(dest interface{}) {
switch d := dest.(type) {
case *bool:
*d = false
case *string:
*d = ""
case *int:
*d = 0
case *int8:
*d = 0
case *int16:
*d = 0
case *int32:
*d = 0
case *int64:
*d = 0
case *uint:
*d = 0
case *uint8:
*d = 0
case *uint16:
*d = 0
case *uint32:
*d = 0
case *uint64:
*d = 0
case *uintptr:
*d = 0
case *float32:
*d = 0
case *float64:
*d = 0
case *interface{}:
*d = nil
case *[]byte:
*d = nil
case *sql.RawBytes:
*d = nil
default:
rv := reflect.ValueOf(dest)
rv.Elem().Set(reflect.Zero(rv.Type().Elem()))
}
}