1 files changed, 240 insertions, 0 deletions
diff --git a/src/internal/fuzz/encoding.go b/src/internal/fuzz/encoding.go
new file mode 100644
index 0000000000..d3f24c3e6c
--- /dev/null
+++ b/src/internal/fuzz/encoding.go
@@ -0,0 +1,240 @@
+// 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"
+	"strconv"
+)
+
+// 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 ...interface{}) []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, float32, float64, bool:
+			fmt.Fprintf(b, "%T(%v)\n", t, t)
+		case string:
+			fmt.Fprintf(b, "string(%q)\n", t)
+		case rune: // int32
+			fmt.Fprintf(b, "rune(%q)\n", t)
+		case byte: // uint8
+			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) ([]interface{}, 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 []interface{}
+	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) (interface{}, 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
+	}
+
+	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 {
+		// Special case for negative numbers.
+		lit, ok := op.X.(*ast.BasicLit)
+		if !ok || (lit.Kind != token.INT && lit.Kind != token.FLOAT) {
+			return nil, fmt.Errorf("expected operation on int or float type")
+		}
+		if op.Op != token.SUB {
+			return nil, fmt.Errorf("unsupported operation on int: %v", op.Op)
+		}
+		val = op.Op.String() + lit.Value // e.g. "-" + "124"
+		kind = lit.Kind
+	} else {
+		lit, ok := arg.(*ast.BasicLit)
+		if !ok {
+			return nil, fmt.Errorf("literal value required for primitive type")
+		}
+		val, kind = lit.Value, lit.Kind
+	}
+
+	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.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)
+	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) (interface{}, error) {
+	switch typ {
+	case "int":
+		return strconv.Atoi(val)
+	case "int8":
+		i, err := strconv.ParseInt(val, 10, 8)
+		return int8(i), err
+	case "int16":
+		i, err := strconv.ParseInt(val, 10, 16)
+		return int16(i), err
+	case "int32":
+		i, err := strconv.ParseInt(val, 10, 32)
+		return int32(i), err
+	case "int64":
+		return strconv.ParseInt(val, 10, 64)
+	default:
+		panic("unreachable")
+	}
+}
+
+// parseInt returns an unsigned integer of value val and type typ.
+func parseUint(val, typ string) (interface{}, error) {
+	switch typ {
+	case "uint":
+		i, err := strconv.ParseUint(val, 10, 0)
+		return uint(i), err
+	case "uint8":
+		i, err := strconv.ParseUint(val, 10, 8)
+		return uint8(i), err
+	case "uint16":
+		i, err := strconv.ParseUint(val, 10, 16)
+		return uint16(i), err
+	case "uint32":
+		i, err := strconv.ParseUint(val, 10, 32)
+		return uint32(i), err
+	case "uint64":
+		return strconv.ParseUint(val, 10, 64)
+	default:
+		panic("unreachable")
+	}
+}