convert.go

Documentation: database/sql

     1  // Copyright 2011 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  // Type conversions for Scan.
     6  
     7  package sql
     8  
     9  import (
    10  	"bytes"
    11  	"database/sql/driver"
    12  	"errors"
    13  	"fmt"
    14  	"reflect"
    15  	"strconv"
    16  	"time"
    17  	"unicode"
    18  	"unicode/utf8"
    19  )
    20  
    21  var errNilPtr = errors.New("destination pointer is nil") // embedded in descriptive error
    22  
    23  func describeNamedValue(nv *driver.NamedValue) string {
    24  	if len(nv.Name) == 0 {
    25  		return fmt.Sprintf("$%d", nv.Ordinal)
    26  	}
    27  	return fmt.Sprintf("with name %q", nv.Name)
    28  }
    29  
    30  func validateNamedValueName(name string) error {
    31  	if len(name) == 0 {
    32  		return nil
    33  	}
    34  	r, _ := utf8.DecodeRuneInString(name)
    35  	if unicode.IsLetter(r) {
    36  		return nil
    37  	}
    38  	return fmt.Errorf("name %q does not begin with a letter", name)
    39  }
    40  
    41  // ccChecker wraps the driver.ColumnConverter and allows it to be used
    42  // as if it were a NamedValueChecker. If the driver ColumnConverter
    43  // is not present then the NamedValueChecker will return driver.ErrSkip.
    44  type ccChecker struct {
    45  	cci  driver.ColumnConverter
    46  	want int
    47  }
    48  
    49  func (c ccChecker) CheckNamedValue(nv *driver.NamedValue) error {
    50  	if c.cci == nil {
    51  		return driver.ErrSkip
    52  	}
    53  	// The column converter shouldn't be called on any index
    54  	// it isn't expecting. The final error will be thrown
    55  	// in the argument converter loop.
    56  	index := nv.Ordinal - 1
    57  	if c.want <= index {
    58  		return nil
    59  	}
    60  
    61  	// First, see if the value itself knows how to convert
    62  	// itself to a driver type. For example, a NullString
    63  	// struct changing into a string or nil.
    64  	if vr, ok := nv.Value.(driver.Valuer); ok {
    65  		sv, err := callValuerValue(vr)
    66  		if err != nil {
    67  			return err
    68  		}
    69  		if !driver.IsValue(sv) {
    70  			return fmt.Errorf("non-subset type %T returned from Value", sv)
    71  		}
    72  		nv.Value = sv
    73  	}
    74  
    75  	// Second, ask the column to sanity check itself. For
    76  	// example, drivers might use this to make sure that
    77  	// an int64 values being inserted into a 16-bit
    78  	// integer field is in range (before getting
    79  	// truncated), or that a nil can't go into a NOT NULL
    80  	// column before going across the network to get the
    81  	// same error.
    82  	var err error
    83  	arg := nv.Value
    84  	nv.Value, err = c.cci.ColumnConverter(index).ConvertValue(arg)
    85  	if err != nil {
    86  		return err
    87  	}
    88  	if !driver.IsValue(nv.Value) {
    89  		return fmt.Errorf("driver ColumnConverter error converted %T to unsupported type %T", arg, nv.Value)
    90  	}
    91  	return nil
    92  }
    93  
    94  // defaultCheckNamedValue wraps the default ColumnConverter to have the same
    95  // function signature as the CheckNamedValue in the driver.NamedValueChecker
    96  // interface.
    97  func defaultCheckNamedValue(nv *driver.NamedValue) (err error) {
    98  	nv.Value, err = driver.DefaultParameterConverter.ConvertValue(nv.Value)
    99  	return err
   100  }
   101  
   102  // driverArgsConnLocked converts arguments from callers of Stmt.Exec and
   103  // Stmt.Query into driver Values.
   104  //
   105  // The statement ds may be nil, if no statement is available.
   106  //
   107  // ci must be locked.
   108  func driverArgsConnLocked(ci driver.Conn, ds *driverStmt, args []any) ([]driver.NamedValue, error) {
   109  	nvargs := make([]driver.NamedValue, len(args))
   110  
   111  	// -1 means the driver doesn't know how to count the number of
   112  	// placeholders, so we won't sanity check input here and instead let the
   113  	// driver deal with errors.
   114  	want := -1
   115  
   116  	var si driver.Stmt
   117  	var cc ccChecker
   118  	if ds != nil {
   119  		si = ds.si
   120  		want = ds.si.NumInput()
   121  		cc.want = want
   122  	}
   123  
   124  	// Check all types of interfaces from the start.
   125  	// Drivers may opt to use the NamedValueChecker for special
   126  	// argument types, then return driver.ErrSkip to pass it along
   127  	// to the column converter.
   128  	nvc, ok := si.(driver.NamedValueChecker)
   129  	if !ok {
   130  		nvc, ok = ci.(driver.NamedValueChecker)
   131  	}
   132  	cci, ok := si.(driver.ColumnConverter)
   133  	if ok {
   134  		cc.cci = cci
   135  	}
   136  
   137  	// Loop through all the arguments, checking each one.
   138  	// If no error is returned simply increment the index
   139  	// and continue. However if driver.ErrRemoveArgument
   140  	// is returned the argument is not included in the query
   141  	// argument list.
   142  	var err error
   143  	var n int
   144  	for _, arg := range args {
   145  		nv := &nvargs[n]
   146  		if np, ok := arg.(NamedArg); ok {
   147  			if err = validateNamedValueName(np.Name); err != nil {
   148  				return nil, err
   149  			}
   150  			arg = np.Value
   151  			nv.Name = np.Name
   152  		}
   153  		nv.Ordinal = n + 1
   154  		nv.Value = arg
   155  
   156  		// Checking sequence has four routes:
   157  		// A: 1. Default
   158  		// B: 1. NamedValueChecker 2. Column Converter 3. Default
   159  		// C: 1. NamedValueChecker 3. Default
   160  		// D: 1. Column Converter 2. Default
   161  		//
   162  		// The only time a Column Converter is called is first
   163  		// or after NamedValueConverter. If first it is handled before
   164  		// the nextCheck label. Thus for repeats tries only when the
   165  		// NamedValueConverter is selected should the Column Converter
   166  		// be used in the retry.
   167  		checker := defaultCheckNamedValue
   168  		nextCC := false
   169  		switch {
   170  		case nvc != nil:
   171  			nextCC = cci != nil
   172  			checker = nvc.CheckNamedValue
   173  		case cci != nil:
   174  			checker = cc.CheckNamedValue
   175  		}
   176  
   177  	nextCheck:
   178  		err = checker(nv)
   179  		switch err {
   180  		case nil:
   181  			n++
   182  			continue
   183  		case driver.ErrRemoveArgument:
   184  			nvargs = nvargs[:len(nvargs)-1]
   185  			continue
   186  		case driver.ErrSkip:
   187  			if nextCC {
   188  				nextCC = false
   189  				checker = cc.CheckNamedValue
   190  			} else {
   191  				checker = defaultCheckNamedValue
   192  			}
   193  			goto nextCheck
   194  		default:
   195  			return nil, fmt.Errorf("sql: converting argument %s type: %v", describeNamedValue(nv), err)
   196  		}
   197  	}
   198  
   199  	// Check the length of arguments after conversion to allow for omitted
   200  	// arguments.
   201  	if want != -1 && len(nvargs) != want {
   202  		return nil, fmt.Errorf("sql: expected %d arguments, got %d", want, len(nvargs))
   203  	}
   204  
   205  	return nvargs, nil
   206  }
   207  
   208  // convertAssign is the same as convertAssignRows, but without the optional
   209  // rows argument.
   210  func convertAssign(dest, src any) error {
   211  	return convertAssignRows(dest, src, nil)
   212  }
   213  
   214  // convertAssignRows copies to dest the value in src, converting it if possible.
   215  // An error is returned if the copy would result in loss of information.
   216  // dest should be a pointer type. If rows is passed in, the rows will
   217  // be used as the parent for any cursor values converted from a
   218  // driver.Rows to a *Rows.
   219  func convertAssignRows(dest, src any, rows *Rows) error {
   220  	// Common cases, without reflect.
   221  	switch s := src.(type) {
   222  	case string:
   223  		switch d := dest.(type) {
   224  		case *string:
   225  			if d == nil {
   226  				return errNilPtr
   227  			}
   228  			*d = s
   229  			return nil
   230  		case *[]byte:
   231  			if d == nil {
   232  				return errNilPtr
   233  			}
   234  			*d = []byte(s)
   235  			return nil
   236  		case *RawBytes:
   237  			if d == nil {
   238  				return errNilPtr
   239  			}
   240  			*d = append((*d)[:0], s...)
   241  			return nil
   242  		}
   243  	case []byte:
   244  		switch d := dest.(type) {
   245  		case *string:
   246  			if d == nil {
   247  				return errNilPtr
   248  			}
   249  			*d = string(s)
   250  			return nil
   251  		case *any:
   252  			if d == nil {
   253  				return errNilPtr
   254  			}
   255  			*d = bytes.Clone(s)
   256  			return nil
   257  		case *[]byte:
   258  			if d == nil {
   259  				return errNilPtr
   260  			}
   261  			*d = bytes.Clone(s)
   262  			return nil
   263  		case *RawBytes:
   264  			if d == nil {
   265  				return errNilPtr
   266  			}
   267  			*d = s
   268  			return nil
   269  		}
   270  	case time.Time:
   271  		switch d := dest.(type) {
   272  		case *time.Time:
   273  			*d = s
   274  			return nil
   275  		case *string:
   276  			*d = s.Format(time.RFC3339Nano)
   277  			return nil
   278  		case *[]byte:
   279  			if d == nil {
   280  				return errNilPtr
   281  			}
   282  			*d = []byte(s.Format(time.RFC3339Nano))
   283  			return nil
   284  		case *RawBytes:
   285  			if d == nil {
   286  				return errNilPtr
   287  			}
   288  			*d = s.AppendFormat((*d)[:0], time.RFC3339Nano)
   289  			return nil
   290  		}
   291  	case decimalDecompose:
   292  		switch d := dest.(type) {
   293  		case decimalCompose:
   294  			return d.Compose(s.Decompose(nil))
   295  		}
   296  	case nil:
   297  		switch d := dest.(type) {
   298  		case *any:
   299  			if d == nil {
   300  				return errNilPtr
   301  			}
   302  			*d = nil
   303  			return nil
   304  		case *[]byte:
   305  			if d == nil {
   306  				return errNilPtr
   307  			}
   308  			*d = nil
   309  			return nil
   310  		case *RawBytes:
   311  			if d == nil {
   312  				return errNilPtr
   313  			}
   314  			*d = nil
   315  			return nil
   316  		}
   317  	// The driver is returning a cursor the client may iterate over.
   318  	case driver.Rows:
   319  		switch d := dest.(type) {
   320  		case *Rows:
   321  			if d == nil {
   322  				return errNilPtr
   323  			}
   324  			if rows == nil {
   325  				return errors.New("invalid context to convert cursor rows, missing parent *Rows")
   326  			}
   327  			rows.closemu.Lock()
   328  			*d = Rows{
   329  				dc:          rows.dc,
   330  				releaseConn: func(error) {},
   331  				rowsi:       s,
   332  			}
   333  			// Chain the cancel function.
   334  			parentCancel := rows.cancel
   335  			rows.cancel = func() {
   336  				// When Rows.cancel is called, the closemu will be locked as well.
   337  				// So we can access rs.lasterr.
   338  				d.close(rows.lasterr)
   339  				if parentCancel != nil {
   340  					parentCancel()
   341  				}
   342  			}
   343  			rows.closemu.Unlock()
   344  			return nil
   345  		}
   346  	}
   347  
   348  	var sv reflect.Value
   349  
   350  	switch d := dest.(type) {
   351  	case *string:
   352  		sv = reflect.ValueOf(src)
   353  		switch sv.Kind() {
   354  		case reflect.Bool,
   355  			reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64,
   356  			reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64,
   357  			reflect.Float32, reflect.Float64:
   358  			*d = asString(src)
   359  			return nil
   360  		}
   361  	case *[]byte:
   362  		sv = reflect.ValueOf(src)
   363  		if b, ok := asBytes(nil, sv); ok {
   364  			*d = b
   365  			return nil
   366  		}
   367  	case *RawBytes:
   368  		sv = reflect.ValueOf(src)
   369  		if b, ok := asBytes([]byte(*d)[:0], sv); ok {
   370  			*d = RawBytes(b)
   371  			return nil
   372  		}
   373  	case *bool:
   374  		bv, err := driver.Bool.ConvertValue(src)
   375  		if err == nil {
   376  			*d = bv.(bool)
   377  		}
   378  		return err
   379  	case *any:
   380  		*d = src
   381  		return nil
   382  	}
   383  
   384  	if scanner, ok := dest.(Scanner); ok {
   385  		return scanner.Scan(src)
   386  	}
   387  
   388  	dpv := reflect.ValueOf(dest)
   389  	if dpv.Kind() != reflect.Pointer {
   390  		return errors.New("destination not a pointer")
   391  	}
   392  	if dpv.IsNil() {
   393  		return errNilPtr
   394  	}
   395  
   396  	if !sv.IsValid() {
   397  		sv = reflect.ValueOf(src)
   398  	}
   399  
   400  	dv := reflect.Indirect(dpv)
   401  	if sv.IsValid() && sv.Type().AssignableTo(dv.Type()) {
   402  		switch b := src.(type) {
   403  		case []byte:
   404  			dv.Set(reflect.ValueOf(bytes.Clone(b)))
   405  		default:
   406  			dv.Set(sv)
   407  		}
   408  		return nil
   409  	}
   410  
   411  	if dv.Kind() == sv.Kind() && sv.Type().ConvertibleTo(dv.Type()) {
   412  		dv.Set(sv.Convert(dv.Type()))
   413  		return nil
   414  	}
   415  
   416  	// The following conversions use a string value as an intermediate representation
   417  	// to convert between various numeric types.
   418  	//
   419  	// This also allows scanning into user defined types such as "type Int int64".
   420  	// For symmetry, also check for string destination types.
   421  	switch dv.Kind() {
   422  	case reflect.Pointer:
   423  		if src == nil {
   424  			dv.SetZero()
   425  			return nil
   426  		}
   427  		dv.Set(reflect.New(dv.Type().Elem()))
   428  		return convertAssignRows(dv.Interface(), src, rows)
   429  	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
   430  		if src == nil {
   431  			return fmt.Errorf("converting NULL to %s is unsupported", dv.Kind())
   432  		}
   433  		s := asString(src)
   434  		i64, err := strconv.ParseInt(s, 10, dv.Type().Bits())
   435  		if err != nil {
   436  			err = strconvErr(err)
   437  			return fmt.Errorf("converting driver.Value type %T (%q) to a %s: %v", src, s, dv.Kind(), err)
   438  		}
   439  		dv.SetInt(i64)
   440  		return nil
   441  	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
   442  		if src == nil {
   443  			return fmt.Errorf("converting NULL to %s is unsupported", dv.Kind())
   444  		}
   445  		s := asString(src)
   446  		u64, err := strconv.ParseUint(s, 10, dv.Type().Bits())
   447  		if err != nil {
   448  			err = strconvErr(err)
   449  			return fmt.Errorf("converting driver.Value type %T (%q) to a %s: %v", src, s, dv.Kind(), err)
   450  		}
   451  		dv.SetUint(u64)
   452  		return nil
   453  	case reflect.Float32, reflect.Float64:
   454  		if src == nil {
   455  			return fmt.Errorf("converting NULL to %s is unsupported", dv.Kind())
   456  		}
   457  		s := asString(src)
   458  		f64, err := strconv.ParseFloat(s, dv.Type().Bits())
   459  		if err != nil {
   460  			err = strconvErr(err)
   461  			return fmt.Errorf("converting driver.Value type %T (%q) to a %s: %v", src, s, dv.Kind(), err)
   462  		}
   463  		dv.SetFloat(f64)
   464  		return nil
   465  	case reflect.String:
   466  		if src == nil {
   467  			return fmt.Errorf("converting NULL to %s is unsupported", dv.Kind())
   468  		}
   469  		switch v := src.(type) {
   470  		case string:
   471  			dv.SetString(v)
   472  			return nil
   473  		case []byte:
   474  			dv.SetString(string(v))
   475  			return nil
   476  		}
   477  	}
   478  
   479  	return fmt.Errorf("unsupported Scan, storing driver.Value type %T into type %T", src, dest)
   480  }
   481  
   482  func strconvErr(err error) error {
   483  	if ne, ok := err.(*strconv.NumError); ok {
   484  		return ne.Err
   485  	}
   486  	return err
   487  }
   488  
   489  func asString(src any) string {
   490  	switch v := src.(type) {
   491  	case string:
   492  		return v
   493  	case []byte:
   494  		return string(v)
   495  	}
   496  	rv := reflect.ValueOf(src)
   497  	switch rv.Kind() {
   498  	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
   499  		return strconv.FormatInt(rv.Int(), 10)
   500  	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
   501  		return strconv.FormatUint(rv.Uint(), 10)
   502  	case reflect.Float64:
   503  		return strconv.FormatFloat(rv.Float(), 'g', -1, 64)
   504  	case reflect.Float32:
   505  		return strconv.FormatFloat(rv.Float(), 'g', -1, 32)
   506  	case reflect.Bool:
   507  		return strconv.FormatBool(rv.Bool())
   508  	}
   509  	return fmt.Sprintf("%v", src)
   510  }
   511  
   512  func asBytes(buf []byte, rv reflect.Value) (b []byte, ok bool) {
   513  	switch rv.Kind() {
   514  	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
   515  		return strconv.AppendInt(buf, rv.Int(), 10), true
   516  	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
   517  		return strconv.AppendUint(buf, rv.Uint(), 10), true
   518  	case reflect.Float32:
   519  		return strconv.AppendFloat(buf, rv.Float(), 'g', -1, 32), true
   520  	case reflect.Float64:
   521  		return strconv.AppendFloat(buf, rv.Float(), 'g', -1, 64), true
   522  	case reflect.Bool:
   523  		return strconv.AppendBool(buf, rv.Bool()), true
   524  	case reflect.String:
   525  		s := rv.String()
   526  		return append(buf, s...), true
   527  	}
   528  	return
   529  }
   530  
   531  var valuerReflectType = reflect.TypeFor[driver.Valuer]()
   532  
   533  // callValuerValue returns vr.Value(), with one exception:
   534  // If vr.Value is an auto-generated method on a pointer type and the
   535  // pointer is nil, it would panic at runtime in the panicwrap
   536  // method. Treat it like nil instead.
   537  // Issue 8415.
   538  //
   539  // This is so people can implement driver.Value on value types and
   540  // still use nil pointers to those types to mean nil/NULL, just like
   541  // string/*string.
   542  //
   543  // This function is mirrored in the database/sql/driver package.
   544  func callValuerValue(vr driver.Valuer) (v driver.Value, err error) {
   545  	if rv := reflect.ValueOf(vr); rv.Kind() == reflect.Pointer &&
   546  		rv.IsNil() &&
   547  		rv.Type().Elem().Implements(valuerReflectType) {
   548  		return nil, nil
   549  	}
   550  	return vr.Value()
   551  }
   552  
   553  // decimal composes or decomposes a decimal value to and from individual parts.
   554  // There are four parts: a boolean negative flag, a form byte with three possible states
   555  // (finite=0, infinite=1, NaN=2), a base-2 big-endian integer
   556  // coefficient (also known as a significand) as a []byte, and an int32 exponent.
   557  // These are composed into a final value as "decimal = (neg) (form=finite) coefficient * 10 ^ exponent".
   558  // A zero length coefficient is a zero value.
   559  // The big-endian integer coefficient stores the most significant byte first (at coefficient[0]).
   560  // If the form is not finite the coefficient and exponent should be ignored.
   561  // The negative parameter may be set to true for any form, although implementations are not required
   562  // to respect the negative parameter in the non-finite form.
   563  //
   564  // Implementations may choose to set the negative parameter to true on a zero or NaN value,
   565  // but implementations that do not differentiate between negative and positive
   566  // zero or NaN values should ignore the negative parameter without error.
   567  // If an implementation does not support Infinity it may be converted into a NaN without error.
   568  // If a value is set that is larger than what is supported by an implementation,
   569  // an error must be returned.
   570  // Implementations must return an error if a NaN or Infinity is attempted to be set while neither
   571  // are supported.
   572  //
   573  // NOTE(kardianos): This is an experimental interface. See https://golang.org/issue/30870
   574  type decimal interface {
   575  	decimalDecompose
   576  	decimalCompose
   577  }
   578  
   579  type decimalDecompose interface {
   580  	// Decompose returns the internal decimal state in parts.
   581  	// If the provided buf has sufficient capacity, buf may be returned as the coefficient with
   582  	// the value set and length set as appropriate.
   583  	Decompose(buf []byte) (form byte, negative bool, coefficient []byte, exponent int32)
   584  }
   585  
   586  type decimalCompose interface {
   587  	// Compose sets the internal decimal value from parts. If the value cannot be
   588  	// represented then an error should be returned.
   589  	Compose(form byte, negative bool, coefficient []byte, exponent int32) error
   590  }
   591
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