libgo/go/database/sql/convert.go - rust-lang/gcc - Git at Google

 // 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 sql

 import (
 	"database/sql/driver"
 	"errors"
 	"fmt"
 	"reflect"
 	"strconv"
 	"time"
 	"unicode"
 	"unicode/utf8"
 )

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

 func describeNamedValue(nv *driver.NamedValue) string {
 	if len(nv.Name) == 0 {
 		return fmt.Sprintf("$%d", nv.Ordinal)
 	}
 	return fmt.Sprintf("with name %q", nv.Name)
 }

 func validateNamedValueName(name string) error {
 	if len(name) == 0 {
 		return nil
 	}
 	r, _ := utf8.DecodeRuneInString(name)
 	if unicode.IsLetter(r) {
 		return nil
 	}
 	return fmt.Errorf("name %q does not begin with a letter", name)
 }

 // ccChecker wraps the driver.ColumnConverter and allows it to be used
 // as if it were a NamedValueChecker. If the driver ColumnConverter
 // is not present then the NamedValueChecker will return driver.ErrSkip.
 type ccChecker struct {
 	cci  driver.ColumnConverter
 	want int
 }

 func (c ccChecker) CheckNamedValue(nv *driver.NamedValue) error {
 	if c.cci == nil {
 		return driver.ErrSkip
 	}
 	// The column converter shouldn't be called on any index
 	// it isn't expecting. The final error will be thrown
 	// in the argument converter loop.
 	index := nv.Ordinal - 1
 	if c.want <= index {
 		return nil
 	}

 	// First, see if the value itself knows how to convert
 	// itself to a driver type. For example, a NullString
 	// struct changing into a string or nil.
 	if vr, ok := nv.Value.(driver.Valuer); ok {
 		sv, err := callValuerValue(vr)
 		if err != nil {
 			return err
 		}
 		if !driver.IsValue(sv) {
 			return fmt.Errorf("non-subset type %T returned from Value", sv)
 		}
 		nv.Value = sv
 	}

 	// Second, ask the column to sanity check itself. For
 	// example, drivers might use this to make sure that
 	// an int64 values being inserted into a 16-bit
 	// integer field is in range (before getting
 	// truncated), or that a nil can't go into a NOT NULL
 	// column before going across the network to get the
 	// same error.
 	var err error
 	arg := nv.Value
 	nv.Value, err = c.cci.ColumnConverter(index).ConvertValue(arg)
 	if err != nil {
 		return err
 	}
 	if !driver.IsValue(nv.Value) {
 		return fmt.Errorf("driver ColumnConverter error converted %T to unsupported type %T", arg, nv.Value)
 	}
 	return nil
 }

 // defaultCheckNamedValue wraps the default ColumnConverter to have the same
 // function signature as the CheckNamedValue in the driver.NamedValueChecker
 // interface.
 func defaultCheckNamedValue(nv *driver.NamedValue) (err error) {
 	nv.Value, err = driver.DefaultParameterConverter.ConvertValue(nv.Value)
 	return err
 }

 // driverArgsConnLocked converts arguments from callers of Stmt.Exec and
 // Stmt.Query into driver Values.
 //
 // The statement ds may be nil, if no statement is available.
 //
 // ci must be locked.
 func driverArgsConnLocked(ci driver.Conn, ds *driverStmt, args []interface{}) ([]driver.NamedValue, error) {
 	nvargs := make([]driver.NamedValue, len(args))

 	// -1 means the driver doesn't know how to count the number of
 	// placeholders, so we won't sanity check input here and instead let the
 	// driver deal with errors.
 	want := -1

 	var si driver.Stmt
 	var cc ccChecker
 	if ds != nil {
 		si = ds.si
 		want = ds.si.NumInput()
 		cc.want = want
 	}

 	// Check all types of interfaces from the start.
 	// Drivers may opt to use the NamedValueChecker for special
 	// argument types, then return driver.ErrSkip to pass it along
 	// to the column converter.
 	nvc, ok := si.(driver.NamedValueChecker)
 	if !ok {
 		nvc, ok = ci.(driver.NamedValueChecker)
 	}
 	cci, ok := si.(driver.ColumnConverter)
 	if ok {
 		cc.cci = cci
 	}

 	// Loop through all the arguments, checking each one.
 	// If no error is returned simply increment the index
 	// and continue. However if driver.ErrRemoveArgument
 	// is returned the argument is not included in the query
 	// argument list.
 	var err error
 	var n int
 	for _, arg := range args {
 		nv := &nvargs[n]
 		if np, ok := arg.(NamedArg); ok {
 			if err = validateNamedValueName(np.Name); err != nil {
 				return nil, err
 			}
 			arg = np.Value
 			nv.Name = np.Name
 		}
 		nv.Ordinal = n + 1
 		nv.Value = arg

 		// Checking sequence has four routes:
 		// A: 1. Default
 		// B: 1. NamedValueChecker 2. Column Converter 3. Default
 		// C: 1. NamedValueChecker 3. Default
 		// D: 1. Column Converter 2. Default
 		//
 		// The only time a Column Converter is called is first
 		// or after NamedValueConverter. If first it is handled before
 		// the nextCheck label. Thus for repeats tries only when the
 		// NamedValueConverter is selected should the Column Converter
 		// be used in the retry.
 		checker := defaultCheckNamedValue
 		nextCC := false
 		switch {
 		case nvc != nil:
 			nextCC = cci != nil
 			checker = nvc.CheckNamedValue
 		case cci != nil:
 			checker = cc.CheckNamedValue
 		}

 	nextCheck:
 		err = checker(nv)
 		switch err {
 		case nil:
 			n++
 			continue
 		case driver.ErrRemoveArgument:
 			nvargs = nvargs[:len(nvargs)-1]
 			continue
 		case driver.ErrSkip:
 			if nextCC {
 				nextCC = false
 				checker = cc.CheckNamedValue
 			} else {
 				checker = defaultCheckNamedValue
 			}
 			goto nextCheck
 		default:
 			return nil, fmt.Errorf("sql: converting argument %s type: %v", describeNamedValue(nv), err)
 		}
 	}

 	// Check the length of arguments after conversion to allow for omitted
 	// arguments.
 	if want != -1 && len(nvargs) != want {
 		return nil, fmt.Errorf("sql: expected %d arguments, got %d", want, len(nvargs))
 	}

 	return nvargs, nil

 }

 // convertAssign is the same as convertAssignRows, but without the optional
 // rows argument.
 func convertAssign(dest, src interface{}) error {
 	return convertAssignRows(dest, src, nil)
 }

 // 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 *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 *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 *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 *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 *RawBytes:
 			if d == nil {
 				return errNilPtr
 			}
 			*d = nil
 			return nil
 		}
 	// The driver is returning a cursor the client may iterate over.
 	case driver.Rows:
 		switch d := dest.(type) {
 		case *Rows:
 			if d == nil {
 				return errNilPtr
 			}
 			if rows == nil {
 				return errors.New("invalid context to convert cursor rows, missing parent *Rows")
 			}
 			rows.closemu.Lock()
 			*d = Rows{
 				dc:          rows.dc,
 				releaseConn: func(error) {},
 				rowsi:       s,
 			}
 			// Chain the cancel function.
 			parentCancel := rows.cancel
 			rows.cancel = func() {
 				// When Rows.cancel is called, the closemu will be locked as well.
 				// So we can access rs.lasterr.
 				d.close(rows.lasterr)
 				if parentCancel != nil {
 					parentCancel()
 				}
 			}
 			rows.closemu.Unlock()
 			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:
 			*d = asString(src)
 			return nil
 		}
 	case *[]byte:
 		sv = reflect.ValueOf(src)
 		if b, ok := asBytes(nil, sv); ok {
 			*d = b
 			return nil
 		}
 	case *RawBytes:
 		sv = reflect.ValueOf(src)
 		if b, ok := asBytes([]byte(*d)[:0], sv); ok {
 			*d = 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.(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
 }
	// 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 sql

	import (
	"database/sql/driver"
	"errors"
	"fmt"
	"reflect"
	"strconv"
	"time"
	"unicode"
	"unicode/utf8"
	)

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

	func describeNamedValue(nv *driver.NamedValue) string {
	if len(nv.Name) == 0 {
	return fmt.Sprintf("$%d", nv.Ordinal)
	}
	return fmt.Sprintf("with name %q", nv.Name)
	}

	func validateNamedValueName(name string) error {
	if len(name) == 0 {
	return nil
	}
	r, _ := utf8.DecodeRuneInString(name)
	if unicode.IsLetter(r) {
	return nil
	}
	return fmt.Errorf("name %q does not begin with a letter", name)
	}

	// ccChecker wraps the driver.ColumnConverter and allows it to be used
	// as if it were a NamedValueChecker. If the driver ColumnConverter
	// is not present then the NamedValueChecker will return driver.ErrSkip.
	type ccChecker struct {
	cci driver.ColumnConverter
	want int
	}

	func (c ccChecker) CheckNamedValue(nv *driver.NamedValue) error {
	if c.cci == nil {
	return driver.ErrSkip
	}
	// The column converter shouldn't be called on any index
	// it isn't expecting. The final error will be thrown
	// in the argument converter loop.
	index := nv.Ordinal - 1
	if c.want <= index {
	return nil
	}

	// First, see if the value itself knows how to convert
	// itself to a driver type. For example, a NullString
	// struct changing into a string or nil.
	if vr, ok := nv.Value.(driver.Valuer); ok {
	sv, err := callValuerValue(vr)
	if err != nil {
	return err
	}
	if !driver.IsValue(sv) {
	return fmt.Errorf("non-subset type %T returned from Value", sv)
	}
	nv.Value = sv
	}

	// Second, ask the column to sanity check itself. For
	// example, drivers might use this to make sure that
	// an int64 values being inserted into a 16-bit
	// integer field is in range (before getting
	// truncated), or that a nil can't go into a NOT NULL
	// column before going across the network to get the
	// same error.
	var err error
	arg := nv.Value
	nv.Value, err = c.cci.ColumnConverter(index).ConvertValue(arg)
	if err != nil {
	return err
	}
	if !driver.IsValue(nv.Value) {
	return fmt.Errorf("driver ColumnConverter error converted %T to unsupported type %T", arg, nv.Value)
	}
	return nil
	}

	// defaultCheckNamedValue wraps the default ColumnConverter to have the same
	// function signature as the CheckNamedValue in the driver.NamedValueChecker
	// interface.
	func defaultCheckNamedValue(nv *driver.NamedValue) (err error) {
	nv.Value, err = driver.DefaultParameterConverter.ConvertValue(nv.Value)
	return err
	}

	// driverArgsConnLocked converts arguments from callers of Stmt.Exec and
	// Stmt.Query into driver Values.
	//
	// The statement ds may be nil, if no statement is available.
	//
	// ci must be locked.
	func driverArgsConnLocked(ci driver.Conn, ds *driverStmt, args []interface{}) ([]driver.NamedValue, error) {
	nvargs := make([]driver.NamedValue, len(args))

	// -1 means the driver doesn't know how to count the number of
	// placeholders, so we won't sanity check input here and instead let the
	// driver deal with errors.
	want := -1

	var si driver.Stmt
	var cc ccChecker
	if ds != nil {
	si = ds.si
	want = ds.si.NumInput()
	cc.want = want
	}

	// Check all types of interfaces from the start.
	// Drivers may opt to use the NamedValueChecker for special
	// argument types, then return driver.ErrSkip to pass it along
	// to the column converter.
	nvc, ok := si.(driver.NamedValueChecker)
	if !ok {
	nvc, ok = ci.(driver.NamedValueChecker)
	}
	cci, ok := si.(driver.ColumnConverter)
	if ok {
	cc.cci = cci
	}

	// Loop through all the arguments, checking each one.
	// If no error is returned simply increment the index
	// and continue. However if driver.ErrRemoveArgument
	// is returned the argument is not included in the query
	// argument list.
	var err error
	var n int
	for _, arg := range args {
	nv := &nvargs[n]
	if np, ok := arg.(NamedArg); ok {
	if err = validateNamedValueName(np.Name); err != nil {
	return nil, err
	}
	arg = np.Value
	nv.Name = np.Name
	}
	nv.Ordinal = n + 1
	nv.Value = arg

	// Checking sequence has four routes:
	// A: 1. Default
	// B: 1. NamedValueChecker 2. Column Converter 3. Default
	// C: 1. NamedValueChecker 3. Default
	// D: 1. Column Converter 2. Default
	//
	// The only time a Column Converter is called is first
	// or after NamedValueConverter. If first it is handled before
	// the nextCheck label. Thus for repeats tries only when the
	// NamedValueConverter is selected should the Column Converter
	// be used in the retry.
	checker := defaultCheckNamedValue
	nextCC := false
	switch {
	case nvc != nil:
	nextCC = cci != nil
	checker = nvc.CheckNamedValue
	case cci != nil:
	checker = cc.CheckNamedValue
	}

	nextCheck:
	err = checker(nv)
	switch err {
	case nil:
	n++
	continue
	case driver.ErrRemoveArgument:
	nvargs = nvargs[:len(nvargs)-1]
	continue
	case driver.ErrSkip:
	if nextCC {
	nextCC = false
	checker = cc.CheckNamedValue
	} else {
	checker = defaultCheckNamedValue
	}
	goto nextCheck
	default:
	return nil, fmt.Errorf("sql: converting argument %s type: %v", describeNamedValue(nv), err)
	}
	}

	// Check the length of arguments after conversion to allow for omitted
	// arguments.
	if want != -1 && len(nvargs) != want {
	return nil, fmt.Errorf("sql: expected %d arguments, got %d", want, len(nvargs))
	}

	return nvargs, nil

	}

	// convertAssign is the same as convertAssignRows, but without the optional
	// rows argument.
	func convertAssign(dest, src interface{}) error {
	return convertAssignRows(dest, src, nil)
	}

	// 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 *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 *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 *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 *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 *RawBytes:
	if d == nil {
	return errNilPtr
	}
	*d = nil
	return nil
	}
	// The driver is returning a cursor the client may iterate over.
	case driver.Rows:
	switch d := dest.(type) {
	case *Rows:
	if d == nil {
	return errNilPtr
	}
	if rows == nil {
	return errors.New("invalid context to convert cursor rows, missing parent *Rows")
	}
	rows.closemu.Lock()
	*d = Rows{
	dc: rows.dc,
	releaseConn: func(error) {},
	rowsi: s,
	}
	// Chain the cancel function.
	parentCancel := rows.cancel
	rows.cancel = func() {
	// When Rows.cancel is called, the closemu will be locked as well.
	// So we can access rs.lasterr.
	d.close(rows.lasterr)
	if parentCancel != nil {
	parentCancel()
	}
	}
	rows.closemu.Unlock()
	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:
	*d = asString(src)
	return nil
	}
	case *[]byte:
	sv = reflect.ValueOf(src)
	if b, ok := asBytes(nil, sv); ok {
	*d = b
	return nil
	}
	case *RawBytes:
	sv = reflect.ValueOf(src)
	if b, ok := asBytes([]byte(*d)[:0], sv); ok {
	*d = 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.(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
	}