intimate/convert.go

// Copyright 2011 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// Type conversions for Scan.

package intimate

import (
	"database/sql/driver"
	"errors"
	"fmt"
	"reflect"
	"strconv"
)

var errNilPtr = errors.New("destination pointer is nil") // embedded in descriptive error

// convertAssignRows 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. If rows is passed in, the rows will
// be used as the parent for any cursor values converted from a
// driver.Rows to a *Rows.
// func convertAssignRows(dest, src interface{}, rows *sql.Rows) error {
// 	// Common cases, without reflect.
// 	switch s := src.(type) {
// 	case string:
// 		switch d := dest.(type) {
// 		case *string:
// 			if d == nil {
// 				return errNilPtr
// 			}
// 			*d = s
// 			return nil
// 		case *[]byte:
// 			if d == nil {
// 				return errNilPtr
// 			}
// 			*d = []byte(s)
// 			return nil
// 		case *sql.RawBytes:
// 			if d == nil {
// 				return errNilPtr
// 			}
// 			*d = append((*d)[:0], s...)
// 			return nil
// 		}
// 	case []byte:
// 		switch d := dest.(type) {
// 		case *string:
// 			if d == nil {
// 				return errNilPtr
// 			}
// 			*d = string(s)
// 			return nil
// 		case *interface{}:
// 			if d == nil {
// 				return errNilPtr
// 			}
// 			*d = cloneBytes(s)
// 			return nil
// 		case *[]byte:
// 			if d == nil {
// 				return errNilPtr
// 			}
// 			*d = cloneBytes(s)
// 			return nil
// 		case *sql.RawBytes:
// 			if d == nil {
// 				return errNilPtr
// 			}
// 			*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:
// 			if d == nil {
// 				return errNilPtr
// 			}
// 			*d = []byte(s.Format(time.RFC3339Nano))
// 			return nil
// 		case *sql.RawBytes:
// 			if d == nil {
// 				return errNilPtr
// 			}
// 			*d = s.AppendFormat((*d)[:0], time.RFC3339Nano)
// 			return nil
// 		}
// 	case decimalDecompose:
// 		switch d := dest.(type) {
// 		case decimalCompose:
// 			return d.Compose(s.Decompose(nil))
// 		}
// 	case nil:
// 		switch d := dest.(type) {
// 		case *interface{}:
// 			if d == nil {
// 				return errNilPtr
// 			}
// 			*d = nil
// 			return nil
// 		case *[]byte:
// 			if d == nil {
// 				return errNilPtr
// 			}
// 			*d = nil
// 			return nil
// 		case *sql.RawBytes:
// 			if d == nil {
// 				return errNilPtr
// 			}
// 			*d = nil
// 			return nil
// 		}
// 		// The driver is returning a cursor the client may iterate over.
// 	}

// 	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:
// 			*d = asString(src)
// 			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
// 	}

// 	if scanner, ok := dest.(sql.Scanner); ok {
// 		return scanner.Scan(src)
// 	}

// 	dpv := reflect.ValueOf(dest)
// 	if dpv.Kind() != reflect.Ptr {
// 		return errors.New("destination not a pointer")
// 	}
// 	if dpv.IsNil() {
// 		return errNilPtr
// 	}

// 	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.
// 	switch dv.Kind() {
// 	case reflect.Ptr:
// 		if src == nil {
// 			dv.Set(reflect.Zero(dv.Type()))
// 			return nil
// 		}
// 		dv.Set(reflect.New(dv.Type().Elem()))
// 		return convertAssignRows(dv.Interface(), src, rows)
// 	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
// 		if src == nil {
// 			return fmt.Errorf("converting NULL to %s is unsupported", dv.Kind())
// 		}
// 		s := asString(src)
// 		i64, err := strconv.ParseInt(s, 10, dv.Type().Bits())
// 		if err != nil {
// 			err = strconvErr(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:
// 		if src == nil {
// 			return fmt.Errorf("converting NULL to %s is unsupported", dv.Kind())
// 		}
// 		s := asString(src)
// 		u64, err := strconv.ParseUint(s, 10, dv.Type().Bits())
// 		if err != nil {
// 			err = strconvErr(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:
// 		if src == nil {
// 			return fmt.Errorf("converting NULL to %s is unsupported", dv.Kind())
// 		}
// 		s := asString(src)
// 		f64, err := strconv.ParseFloat(s, dv.Type().Bits())
// 		if err != nil {
// 			err = strconvErr(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:
// 		if src == nil {
// 			return fmt.Errorf("converting NULL to %s is unsupported", dv.Kind())
// 		}
// 		switch v := src.(type) {
// 		case string:
// 			dv.SetString(v)
// 			return nil
// 		case []byte:
// 			dv.SetString(string(v))
// 			return nil
// 		}
// 	}

// 	return fmt.Errorf("unsupported Scan, storing driver.Value type %T into type %T", src, dest)
// }

func strconvErr(err error) error {
	if ne, ok := err.(*strconv.NumError); ok {
		return ne.Err
	}
	return err
}

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 {
	switch v := src.(type) {
	case string:
		return v
	case []byte:
		return string(v)
	}
	rv := reflect.ValueOf(src)
	switch rv.Kind() {
	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
		return strconv.FormatInt(rv.Int(), 10)
	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
		return strconv.FormatUint(rv.Uint(), 10)
	case reflect.Float64:
		return strconv.FormatFloat(rv.Float(), 'g', -1, 64)
	case reflect.Float32:
		return strconv.FormatFloat(rv.Float(), 'g', -1, 32)
	case reflect.Bool:
		return strconv.FormatBool(rv.Bool())
	}
	return fmt.Sprintf("%v", src)
}

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
}

var valuerReflectType = reflect.TypeOf((*driver.Valuer)(nil)).Elem()

// callValuerValue returns vr.Value(), with one exception:
// If vr.Value is an auto-generated method on a pointer type and the
// pointer is nil, it would panic at runtime in the panicwrap
// method. Treat it like nil instead.
// Issue 8415.
//
// This is so people can implement driver.Value on value types and
// still use nil pointers to those types to mean nil/NULL, just like
// string/*string.
//
// This function is mirrored in the database/sql/driver package.
func callValuerValue(vr driver.Valuer) (v driver.Value, err error) {
	if rv := reflect.ValueOf(vr); rv.Kind() == reflect.Ptr &&
		rv.IsNil() &&
		rv.Type().Elem().Implements(valuerReflectType) {
		return nil, nil
	}
	return vr.Value()
}

// decimal composes or decomposes a decimal value to and from individual parts.
// There are four parts: a boolean negative flag, a form byte with three possible states
// (finite=0, infinite=1, NaN=2), a base-2 big-endian integer
// coefficient (also known as a significand) as a []byte, and an int32 exponent.
// These are composed into a final value as "decimal = (neg) (form=finite) coefficient * 10 ^ exponent".
// A zero length coefficient is a zero value.
// The big-endian integer coefficient stores the most significant byte first (at coefficient[0]).
// If the form is not finite the coefficient and exponent should be ignored.
// The negative parameter may be set to true for any form, although implementations are not required
// to respect the negative parameter in the non-finite form.
//
// Implementations may choose to set the negative parameter to true on a zero or NaN value,
// but implementations that do not differentiate between negative and positive
// zero or NaN values should ignore the negative parameter without error.
// If an implementation does not support Infinity it may be converted into a NaN without error.
// If a value is set that is larger than what is supported by an implementation,
// an error must be returned.
// Implementations must return an error if a NaN or Infinity is attempted to be set while neither
// are supported.
//
// NOTE(kardianos): This is an experimental interface. See https://golang.org/issue/30870
type decimal interface {
	decimalDecompose
	decimalCompose
}

type decimalDecompose interface {
	// Decompose returns the internal decimal state in parts.
	// If the provided buf has sufficient capacity, buf may be returned as the coefficient with
	// the value set and length set as appropriate.
	Decompose(buf []byte) (form byte, negative bool, coefficient []byte, exponent int32)
}

type decimalCompose interface {
	// Compose sets the internal decimal value from parts. If the value cannot be
	// represented then an error should be returned.
	Compose(form byte, negative bool, coefficient []byte, exponent int32) error
}