src/internal/fuzz/encoding.go - go - Git at Google

 // Copyright 2021 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.

 package fuzz

 import (
 	"bytes"
 	"fmt"
 	"go/ast"
 	"go/parser"
 	"go/token"
 	"math"
 	"strconv"
 	"unicode/utf8"
 )

 // encVersion1 will be the first line of a file with version 1 encoding.
 var encVersion1 = "go test fuzz v1"

 // marshalCorpusFile encodes an arbitrary number of arguments into the file format for the
 // corpus.
 func marshalCorpusFile(vals ...any) []byte {
 	if len(vals) == 0 {
 		panic("must have at least one value to marshal")
 	}
 	b := bytes.NewBuffer([]byte(encVersion1 + "\n"))
 	// TODO(katiehockman): keep uint8 and int32 encoding where applicable,
 	// instead of changing to byte and rune respectively.
 	for _, val := range vals {
 		switch t := val.(type) {
 		case int, int8, int16, int64, uint, uint16, uint32, uint64, bool:
 			fmt.Fprintf(b, "%T(%v)\n", t, t)
 		case float32:
 			if math.IsNaN(float64(t)) && math.Float32bits(t) != math.Float32bits(float32(math.NaN())) {
 				// We encode unusual NaNs as hex values, because that is how users are
 				// likely to encounter them in literature about floating-point encoding.
 				// This allows us to reproduce fuzz failures that depend on the specific
 				// NaN representation (for float32 there are about 2^24 possibilities!),
 				// not just the fact that the value is *a* NaN.
 				//
 				// Note that the specific value of float32(math.NaN()) can vary based on
 				// whether the architecture represents signaling NaNs using a low bit
 				// (as is common) or a high bit (as commonly implemented on MIPS
 				// hardware before around 2012). We believe that the increase in clarity
 				// from identifying "NaN" with math.NaN() is worth the slight ambiguity
 				// from a platform-dependent value.
 				fmt.Fprintf(b, "math.Float32frombits(0x%x)\n", math.Float32bits(t))
 			} else {
 				// We encode all other values — including the NaN value that is
 				// bitwise-identical to float32(math.Nan()) — using the default
 				// formatting, which is equivalent to strconv.FormatFloat with format
 				// 'g' and can be parsed by strconv.ParseFloat.
 				//
 				// For an ordinary floating-point number this format includes
 				// sufficiently many digits to reconstruct the exact value. For positive
 				// or negative infinity it is the string "+Inf" or "-Inf". For positive
 				// or negative zero it is "0" or "-0". For NaN, it is the string "NaN".
 				fmt.Fprintf(b, "%T(%v)\n", t, t)
 			}
 		case float64:
 			if math.IsNaN(t) && math.Float64bits(t) != math.Float64bits(math.NaN()) {
 				fmt.Fprintf(b, "math.Float64frombits(0x%x)\n", math.Float64bits(t))
 			} else {
 				fmt.Fprintf(b, "%T(%v)\n", t, t)
 			}
 		case string:
 			fmt.Fprintf(b, "string(%q)\n", t)
 		case rune: // int32
 			// Although rune and int32 are represented by the same type, only a subset
 			// of valid int32 values can be expressed as rune literals. Notably,
 			// negative numbers, surrogate halves, and values above unicode.MaxRune
 			// have no quoted representation.
 			//
 			// fmt with "%q" (and the corresponding functions in the strconv package)
 			// would quote out-of-range values to the Unicode replacement character
 			// instead of the original value (see https://go.dev/issue/51526), so
 			// they must be treated as int32 instead.
 			//
 			// We arbitrarily draw the line at UTF-8 validity, which biases toward the
 			// "rune" interpretation. (However, we accept either format as input.)
 			if utf8.ValidRune(t) {
 				fmt.Fprintf(b, "rune(%q)\n", t)
 			} else {
 				fmt.Fprintf(b, "int32(%v)\n", t)
 			}
 		case byte: // uint8
 			// For bytes, we arbitrarily prefer the character interpretation.
 			// (Every byte has a valid character encoding.)
 			fmt.Fprintf(b, "byte(%q)\n", t)
 		case []byte: // []uint8
 			fmt.Fprintf(b, "[]byte(%q)\n", t)
 		default:
 			panic(fmt.Sprintf("unsupported type: %T", t))
 		}
 	}
 	return b.Bytes()
 }

 // unmarshalCorpusFile decodes corpus bytes into their respective values.
 func unmarshalCorpusFile(b []byte) ([]any, error) {
 	if len(b) == 0 {
 		return nil, fmt.Errorf("cannot unmarshal empty string")
 	}
 	lines := bytes.Split(b, []byte("\n"))
 	if len(lines) < 2 {
 		return nil, fmt.Errorf("must include version and at least one value")
 	}
 	if string(lines[0]) != encVersion1 {
 		return nil, fmt.Errorf("unknown encoding version: %s", lines[0])
 	}
 	var vals []any
 	for _, line := range lines[1:] {
 		line = bytes.TrimSpace(line)
 		if len(line) == 0 {
 			continue
 		}
 		v, err := parseCorpusValue(line)
 		if err != nil {
 			return nil, fmt.Errorf("malformed line %q: %v", line, err)
 		}
 		vals = append(vals, v)
 	}
 	return vals, nil
 }

 func parseCorpusValue(line []byte) (any, error) {
 	fs := token.NewFileSet()
 	expr, err := parser.ParseExprFrom(fs, "(test)", line, 0)
 	if err != nil {
 		return nil, err
 	}
 	call, ok := expr.(*ast.CallExpr)
 	if !ok {
 		return nil, fmt.Errorf("expected call expression")
 	}
 	if len(call.Args) != 1 {
 		return nil, fmt.Errorf("expected call expression with 1 argument; got %d", len(call.Args))
 	}
 	arg := call.Args[0]

 	if arrayType, ok := call.Fun.(*ast.ArrayType); ok {
 		if arrayType.Len != nil {
 			return nil, fmt.Errorf("expected []byte or primitive type")
 		}
 		elt, ok := arrayType.Elt.(*ast.Ident)
 		if !ok || elt.Name != "byte" {
 			return nil, fmt.Errorf("expected []byte")
 		}
 		lit, ok := arg.(*ast.BasicLit)
 		if !ok || lit.Kind != token.STRING {
 			return nil, fmt.Errorf("string literal required for type []byte")
 		}
 		s, err := strconv.Unquote(lit.Value)
 		if err != nil {
 			return nil, err
 		}
 		return []byte(s), nil
 	}

 	var idType *ast.Ident
 	if selector, ok := call.Fun.(*ast.SelectorExpr); ok {
 		xIdent, ok := selector.X.(*ast.Ident)
 		if !ok || xIdent.Name != "math" {
 			return nil, fmt.Errorf("invalid selector type")
 		}
 		switch selector.Sel.Name {
 		case "Float64frombits":
 			idType = &ast.Ident{Name: "float64-bits"}
 		case "Float32frombits":
 			idType = &ast.Ident{Name: "float32-bits"}
 		default:
 			return nil, fmt.Errorf("invalid selector type")
 		}
 	} else {
 		idType, ok = call.Fun.(*ast.Ident)
 		if !ok {
 			return nil, fmt.Errorf("expected []byte or primitive type")
 		}
 		if idType.Name == "bool" {
 			id, ok := arg.(*ast.Ident)
 			if !ok {
 				return nil, fmt.Errorf("malformed bool")
 			}
 			if id.Name == "true" {
 				return true, nil
 			} else if id.Name == "false" {
 				return false, nil
 			} else {
 				return nil, fmt.Errorf("true or false required for type bool")
 			}
 		}
 	}

 	var (
 		val  string
 		kind token.Token
 	)
 	if op, ok := arg.(*ast.UnaryExpr); ok {
 		switch lit := op.X.(type) {
 		case *ast.BasicLit:
 			if op.Op != token.SUB {
 				return nil, fmt.Errorf("unsupported operation on int/float: %v", op.Op)
 			}
 			// Special case for negative numbers.
 			val = op.Op.String() + lit.Value // e.g. "-" + "124"
 			kind = lit.Kind
 		case *ast.Ident:
 			if lit.Name != "Inf" {
 				return nil, fmt.Errorf("expected operation on int or float type")
 			}
 			if op.Op == token.SUB {
 				val = "-Inf"
 			} else {
 				val = "+Inf"
 			}
 			kind = token.FLOAT
 		default:
 			return nil, fmt.Errorf("expected operation on int or float type")
 		}
 	} else {
 		switch lit := arg.(type) {
 		case *ast.BasicLit:
 			val, kind = lit.Value, lit.Kind
 		case *ast.Ident:
 			if lit.Name != "NaN" {
 				return nil, fmt.Errorf("literal value required for primitive type")
 			}
 			val, kind = "NaN", token.FLOAT
 		default:
 			return nil, fmt.Errorf("literal value required for primitive type")
 		}
 	}

 	switch typ := idType.Name; typ {
 	case "string":
 		if kind != token.STRING {
 			return nil, fmt.Errorf("string literal value required for type string")
 		}
 		return strconv.Unquote(val)
 	case "byte", "rune":
 		if kind == token.INT {
 			switch typ {
 			case "rune":
 				return parseInt(val, typ)
 			case "byte":
 				return parseUint(val, typ)
 			}
 		}
 		if kind != token.CHAR {
 			return nil, fmt.Errorf("character literal required for byte/rune types")
 		}
 		n := len(val)
 		if n < 2 {
 			return nil, fmt.Errorf("malformed character literal, missing single quotes")
 		}
 		code, _, _, err := strconv.UnquoteChar(val[1:n-1], '\'')
 		if err != nil {
 			return nil, err
 		}
 		if typ == "rune" {
 			return code, nil
 		}
 		if code >= 256 {
 			return nil, fmt.Errorf("can only encode single byte to a byte type")
 		}
 		return byte(code), nil
 	case "int", "int8", "int16", "int32", "int64":
 		if kind != token.INT {
 			return nil, fmt.Errorf("integer literal required for int types")
 		}
 		return parseInt(val, typ)
 	case "uint", "uint8", "uint16", "uint32", "uint64":
 		if kind != token.INT {
 			return nil, fmt.Errorf("integer literal required for uint types")
 		}
 		return parseUint(val, typ)
 	case "float32":
 		if kind != token.FLOAT && kind != token.INT {
 			return nil, fmt.Errorf("float or integer literal required for float32 type")
 		}
 		v, err := strconv.ParseFloat(val, 32)
 		return float32(v), err
 	case "float64":
 		if kind != token.FLOAT && kind != token.INT {
 			return nil, fmt.Errorf("float or integer literal required for float64 type")
 		}
 		return strconv.ParseFloat(val, 64)
 	case "float32-bits":
 		if kind != token.INT {
 			return nil, fmt.Errorf("integer literal required for math.Float32frombits type")
 		}
 		bits, err := parseUint(val, "uint32")
 		if err != nil {
 			return nil, err
 		}
 		return math.Float32frombits(bits.(uint32)), nil
 	case "float64-bits":
 		if kind != token.FLOAT && kind != token.INT {
 			return nil, fmt.Errorf("integer literal required for math.Float64frombits type")
 		}
 		bits, err := parseUint(val, "uint64")
 		if err != nil {
 			return nil, err
 		}
 		return math.Float64frombits(bits.(uint64)), nil
 	default:
 		return nil, fmt.Errorf("expected []byte or primitive type")
 	}
 }

 // parseInt returns an integer of value val and type typ.
 func parseInt(val, typ string) (any, error) {
 	switch typ {
 	case "int":
 		// The int type may be either 32 or 64 bits. If 32, the fuzz tests in the
 		// corpus may include 64-bit values produced by fuzzing runs on 64-bit
 		// architectures. When running those tests, we implicitly wrap the values to
 		// fit in a regular int. (The test case is still “interesting”, even if the
 		// specific values of its inputs are platform-dependent.)
 		i, err := strconv.ParseInt(val, 0, 64)
 		return int(i), err
 	case "int8":
 		i, err := strconv.ParseInt(val, 0, 8)
 		return int8(i), err
 	case "int16":
 		i, err := strconv.ParseInt(val, 0, 16)
 		return int16(i), err
 	case "int32", "rune":
 		i, err := strconv.ParseInt(val, 0, 32)
 		return int32(i), err
 	case "int64":
 		return strconv.ParseInt(val, 0, 64)
 	default:
 		panic("unreachable")
 	}
 }

 // parseInt returns an unsigned integer of value val and type typ.
 func parseUint(val, typ string) (any, error) {
 	switch typ {
 	case "uint":
 		i, err := strconv.ParseUint(val, 0, 64)
 		return uint(i), err
 	case "uint8", "byte":
 		i, err := strconv.ParseUint(val, 0, 8)
 		return uint8(i), err
 	case "uint16":
 		i, err := strconv.ParseUint(val, 0, 16)
 		return uint16(i), err
 	case "uint32":
 		i, err := strconv.ParseUint(val, 0, 32)
 		return uint32(i), err
 	case "uint64":
 		return strconv.ParseUint(val, 0, 64)
 	default:
 		panic("unreachable")
 	}
 }
	// Copyright 2021 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.

	package fuzz

	import (
	"bytes"
	"fmt"
	"go/ast"
	"go/parser"
	"go/token"
	"math"
	"strconv"
	"unicode/utf8"
	)

	// encVersion1 will be the first line of a file with version 1 encoding.
	var encVersion1 = "go test fuzz v1"

	// marshalCorpusFile encodes an arbitrary number of arguments into the file format for the
	// corpus.
	func marshalCorpusFile(vals ...any) []byte {
	if len(vals) == 0 {
	panic("must have at least one value to marshal")
	}
	b := bytes.NewBuffer([]byte(encVersion1 + "\n"))
	// TODO(katiehockman): keep uint8 and int32 encoding where applicable,
	// instead of changing to byte and rune respectively.
	for _, val := range vals {
	switch t := val.(type) {
	case int, int8, int16, int64, uint, uint16, uint32, uint64, bool:
	fmt.Fprintf(b, "%T(%v)\n", t, t)
	case float32:
	if math.IsNaN(float64(t)) && math.Float32bits(t) != math.Float32bits(float32(math.NaN())) {
	// We encode unusual NaNs as hex values, because that is how users are
	// likely to encounter them in literature about floating-point encoding.
	// This allows us to reproduce fuzz failures that depend on the specific
	// NaN representation (for float32 there are about 2^24 possibilities!),
	// not just the fact that the value is a NaN.
	//
	// Note that the specific value of float32(math.NaN()) can vary based on
	// whether the architecture represents signaling NaNs using a low bit
	// (as is common) or a high bit (as commonly implemented on MIPS
	// hardware before around 2012). We believe that the increase in clarity
	// from identifying "NaN" with math.NaN() is worth the slight ambiguity
	// from a platform-dependent value.
	fmt.Fprintf(b, "math.Float32frombits(0x%x)\n", math.Float32bits(t))
	} else {
	// We encode all other values — including the NaN value that is
	// bitwise-identical to float32(math.Nan()) — using the default
	// formatting, which is equivalent to strconv.FormatFloat with format
	// 'g' and can be parsed by strconv.ParseFloat.
	//
	// For an ordinary floating-point number this format includes
	// sufficiently many digits to reconstruct the exact value. For positive
	// or negative infinity it is the string "+Inf" or "-Inf". For positive
	// or negative zero it is "0" or "-0". For NaN, it is the string "NaN".
	fmt.Fprintf(b, "%T(%v)\n", t, t)
	}
	case float64:
	if math.IsNaN(t) && math.Float64bits(t) != math.Float64bits(math.NaN()) {
	fmt.Fprintf(b, "math.Float64frombits(0x%x)\n", math.Float64bits(t))
	} else {
	fmt.Fprintf(b, "%T(%v)\n", t, t)
	}
	case string:
	fmt.Fprintf(b, "string(%q)\n", t)
	case rune: // int32
	// Although rune and int32 are represented by the same type, only a subset
	// of valid int32 values can be expressed as rune literals. Notably,
	// negative numbers, surrogate halves, and values above unicode.MaxRune
	// have no quoted representation.
	//
	// fmt with "%q" (and the corresponding functions in the strconv package)
	// would quote out-of-range values to the Unicode replacement character
	// instead of the original value (see https://go.dev/issue/51526), so
	// they must be treated as int32 instead.
	//
	// We arbitrarily draw the line at UTF-8 validity, which biases toward the
	// "rune" interpretation. (However, we accept either format as input.)
	if utf8.ValidRune(t) {
	fmt.Fprintf(b, "rune(%q)\n", t)
	} else {
	fmt.Fprintf(b, "int32(%v)\n", t)
	}
	case byte: // uint8
	// For bytes, we arbitrarily prefer the character interpretation.
	// (Every byte has a valid character encoding.)
	fmt.Fprintf(b, "byte(%q)\n", t)
	case []byte: // []uint8
	fmt.Fprintf(b, "[]byte(%q)\n", t)
	default:
	panic(fmt.Sprintf("unsupported type: %T", t))
	}
	}
	return b.Bytes()
	}

	// unmarshalCorpusFile decodes corpus bytes into their respective values.
	func unmarshalCorpusFile(b []byte) ([]any, error) {
	if len(b) == 0 {
	return nil, fmt.Errorf("cannot unmarshal empty string")
	}
	lines := bytes.Split(b, []byte("\n"))
	if len(lines) < 2 {
	return nil, fmt.Errorf("must include version and at least one value")
	}
	if string(lines[0]) != encVersion1 {
	return nil, fmt.Errorf("unknown encoding version: %s", lines[0])
	}
	var vals []any
	for _, line := range lines[1:] {
	line = bytes.TrimSpace(line)
	if len(line) == 0 {
	continue
	}
	v, err := parseCorpusValue(line)
	if err != nil {
	return nil, fmt.Errorf("malformed line %q: %v", line, err)
	}
	vals = append(vals, v)
	}
	return vals, nil
	}

	func parseCorpusValue(line []byte) (any, error) {
	fs := token.NewFileSet()
	expr, err := parser.ParseExprFrom(fs, "(test)", line, 0)
	if err != nil {
	return nil, err
	}
	call, ok := expr.(*ast.CallExpr)
	if !ok {
	return nil, fmt.Errorf("expected call expression")
	}
	if len(call.Args) != 1 {
	return nil, fmt.Errorf("expected call expression with 1 argument; got %d", len(call.Args))
	}
	arg := call.Args[0]

	if arrayType, ok := call.Fun.(*ast.ArrayType); ok {
	if arrayType.Len != nil {
	return nil, fmt.Errorf("expected []byte or primitive type")
	}
	elt, ok := arrayType.Elt.(*ast.Ident)
	if !ok \|\| elt.Name != "byte" {
	return nil, fmt.Errorf("expected []byte")
	}
	lit, ok := arg.(*ast.BasicLit)
	if !ok \|\| lit.Kind != token.STRING {
	return nil, fmt.Errorf("string literal required for type []byte")
	}
	s, err := strconv.Unquote(lit.Value)
	if err != nil {
	return nil, err
	}
	return []byte(s), nil
	}

	var idType *ast.Ident
	if selector, ok := call.Fun.(*ast.SelectorExpr); ok {
	xIdent, ok := selector.X.(*ast.Ident)
	if !ok \|\| xIdent.Name != "math" {
	return nil, fmt.Errorf("invalid selector type")
	}
	switch selector.Sel.Name {
	case "Float64frombits":
	idType = &ast.Ident{Name: "float64-bits"}
	case "Float32frombits":
	idType = &ast.Ident{Name: "float32-bits"}
	default:
	return nil, fmt.Errorf("invalid selector type")
	}
	} else {
	idType, ok = call.Fun.(*ast.Ident)
	if !ok {
	return nil, fmt.Errorf("expected []byte or primitive type")
	}
	if idType.Name == "bool" {
	id, ok := arg.(*ast.Ident)
	if !ok {
	return nil, fmt.Errorf("malformed bool")
	}
	if id.Name == "true" {
	return true, nil
	} else if id.Name == "false" {
	return false, nil
	} else {
	return nil, fmt.Errorf("true or false required for type bool")
	}
	}
	}

	var (
	val string
	kind token.Token
	)
	if op, ok := arg.(*ast.UnaryExpr); ok {
	switch lit := op.X.(type) {
	case *ast.BasicLit:
	if op.Op != token.SUB {
	return nil, fmt.Errorf("unsupported operation on int/float: %v", op.Op)
	}
	// Special case for negative numbers.
	val = op.Op.String() + lit.Value // e.g. "-" + "124"
	kind = lit.Kind
	case *ast.Ident:
	if lit.Name != "Inf" {
	return nil, fmt.Errorf("expected operation on int or float type")
	}
	if op.Op == token.SUB {
	val = "-Inf"
	} else {
	val = "+Inf"
	}
	kind = token.FLOAT
	default:
	return nil, fmt.Errorf("expected operation on int or float type")
	}
	} else {
	switch lit := arg.(type) {
	case *ast.BasicLit:
	val, kind = lit.Value, lit.Kind
	case *ast.Ident:
	if lit.Name != "NaN" {
	return nil, fmt.Errorf("literal value required for primitive type")
	}
	val, kind = "NaN", token.FLOAT
	default:
	return nil, fmt.Errorf("literal value required for primitive type")
	}
	}

	switch typ := idType.Name; typ {
	case "string":
	if kind != token.STRING {
	return nil, fmt.Errorf("string literal value required for type string")
	}
	return strconv.Unquote(val)
	case "byte", "rune":
	if kind == token.INT {
	switch typ {
	case "rune":
	return parseInt(val, typ)
	case "byte":
	return parseUint(val, typ)
	}
	}
	if kind != token.CHAR {
	return nil, fmt.Errorf("character literal required for byte/rune types")
	}
	n := len(val)
	if n < 2 {
	return nil, fmt.Errorf("malformed character literal, missing single quotes")
	}
	code, _, _, err := strconv.UnquoteChar(val[1:n-1], '\'')
	if err != nil {
	return nil, err
	}
	if typ == "rune" {
	return code, nil
	}
	if code >= 256 {
	return nil, fmt.Errorf("can only encode single byte to a byte type")
	}
	return byte(code), nil
	case "int", "int8", "int16", "int32", "int64":
	if kind != token.INT {
	return nil, fmt.Errorf("integer literal required for int types")
	}
	return parseInt(val, typ)
	case "uint", "uint8", "uint16", "uint32", "uint64":
	if kind != token.INT {
	return nil, fmt.Errorf("integer literal required for uint types")
	}
	return parseUint(val, typ)
	case "float32":
	if kind != token.FLOAT && kind != token.INT {
	return nil, fmt.Errorf("float or integer literal required for float32 type")
	}
	v, err := strconv.ParseFloat(val, 32)
	return float32(v), err
	case "float64":
	if kind != token.FLOAT && kind != token.INT {
	return nil, fmt.Errorf("float or integer literal required for float64 type")
	}
	return strconv.ParseFloat(val, 64)
	case "float32-bits":
	if kind != token.INT {
	return nil, fmt.Errorf("integer literal required for math.Float32frombits type")
	}
	bits, err := parseUint(val, "uint32")
	if err != nil {
	return nil, err
	}
	return math.Float32frombits(bits.(uint32)), nil
	case "float64-bits":
	if kind != token.FLOAT && kind != token.INT {
	return nil, fmt.Errorf("integer literal required for math.Float64frombits type")
	}
	bits, err := parseUint(val, "uint64")
	if err != nil {
	return nil, err
	}
	return math.Float64frombits(bits.(uint64)), nil
	default:
	return nil, fmt.Errorf("expected []byte or primitive type")
	}
	}

	// parseInt returns an integer of value val and type typ.
	func parseInt(val, typ string) (any, error) {
	switch typ {
	case "int":
	// The int type may be either 32 or 64 bits. If 32, the fuzz tests in the
	// corpus may include 64-bit values produced by fuzzing runs on 64-bit
	// architectures. When running those tests, we implicitly wrap the values to
	// fit in a regular int. (The test case is still “interesting”, even if the
	// specific values of its inputs are platform-dependent.)
	i, err := strconv.ParseInt(val, 0, 64)
	return int(i), err
	case "int8":
	i, err := strconv.ParseInt(val, 0, 8)
	return int8(i), err
	case "int16":
	i, err := strconv.ParseInt(val, 0, 16)
	return int16(i), err
	case "int32", "rune":
	i, err := strconv.ParseInt(val, 0, 32)
	return int32(i), err
	case "int64":
	return strconv.ParseInt(val, 0, 64)
	default:
	panic("unreachable")
	}
	}

	// parseInt returns an unsigned integer of value val and type typ.
	func parseUint(val, typ string) (any, error) {
	switch typ {
	case "uint":
	i, err := strconv.ParseUint(val, 0, 64)
	return uint(i), err
	case "uint8", "byte":
	i, err := strconv.ParseUint(val, 0, 8)
	return uint8(i), err
	case "uint16":
	i, err := strconv.ParseUint(val, 0, 16)
	return uint16(i), err
	case "uint32":
	i, err := strconv.ParseUint(val, 0, 32)
	return uint32(i), err
	case "uint64":
	return strconv.ParseUint(val, 0, 64)
	default:
	panic("unreachable")
	}
	}