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// 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"
)
var errNilPtr = errors.New("destination pointer is nil") // embedded in descriptive error
// driverArgs converts arguments from callers of Stmt.Exec and
// Stmt.Query into driver Values.
//
// The statement si may be nil, if no statement is available.
func driverArgs(si driver.Stmt, args []interface{}) ([]driver.Value, error) {
dargs := make([]driver.Value, len(args))
cc, ok := si.(driver.ColumnConverter)
// Normal path, for a driver.Stmt that is not a ColumnConverter.
if !ok {
for n, arg := range args {
var err error
dargs[n], err = driver.DefaultParameterConverter.ConvertValue(arg)
if err != nil {
return nil, fmt.Errorf("sql: converting Exec argument #%d's type: %v", n, err)
}
}
return dargs, nil
}
// Let the Stmt convert its own arguments.
for n, arg := range args {
// 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 svi, ok := arg.(driver.Valuer); ok {
sv, err := svi.Value()
if err != nil {
return nil, fmt.Errorf("sql: argument index %d from Value: %v", n, err)
}
if !driver.IsValue(sv) {
return nil, fmt.Errorf("sql: argument index %d: non-subset type %T returned from Value", n, sv)
}
arg = 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
dargs[n], err = cc.ColumnConverter(n).ConvertValue(arg)
if err != nil {
return nil, fmt.Errorf("sql: converting argument #%d's type: %v", n, err)
}
if !driver.IsValue(dargs[n]) {
return nil, fmt.Errorf("sql: driver ColumnConverter error converted %T to unsupported type %T",
arg, dargs[n])
}
}
return dargs, nil
}
// 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.
func convertAssign(dest, src interface{}) 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 []byte:
switch d := dest.(type) {
case *string:
if d == nil {
return errNilPtr
}
*d = string(s)
return nil
case *interface{}:
if d == nil {
return errNilPtr
}
bcopy := make([]byte, len(s))
copy(bcopy, s)
*d = bcopy
return nil
case *[]byte:
if d == nil {
return errNilPtr
}
*d = s
return nil
}
case nil:
switch d := dest.(type) {
case *[]byte:
if d == nil {
return errNilPtr
}
*d = nil
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 = fmt.Sprintf("%v", src)
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 dv.Kind() == sv.Kind() {
dv.Set(sv)
return nil
}
switch dv.Kind() {
case reflect.Ptr:
if src == nil {
dv.Set(reflect.Zero(dv.Type()))
return nil
} else {
dv.Set(reflect.New(dv.Type().Elem()))
return convertAssign(dv.Interface(), src)
}
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
s := asString(src)
i64, err := strconv.ParseInt(s, 10, dv.Type().Bits())
if err != nil {
return fmt.Errorf("converting string %q to a %s: %v", s, dv.Kind(), err)
}
dv.SetInt(i64)
return nil
case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
s := asString(src)
u64, err := strconv.ParseUint(s, 10, dv.Type().Bits())
if err != nil {
return fmt.Errorf("converting string %q to a %s: %v", s, dv.Kind(), err)
}
dv.SetUint(u64)
return nil
case reflect.Float32, reflect.Float64:
s := asString(src)
f64, err := strconv.ParseFloat(s, dv.Type().Bits())
if err != nil {
return fmt.Errorf("converting string %q to a %s: %v", s, dv.Kind(), err)
}
dv.SetFloat(f64)
return nil
}
return fmt.Errorf("unsupported driver -> Scan pair: %T -> %T", src, dest)
}
func asString(src interface{}) string {
switch v := src.(type) {
case string:
return v
case []byte:
return string(v)
}
return fmt.Sprintf("%v", src)
}
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