net/http: add a package to parse and serialize Structured Field Values

Structured Field Values fields value for HTTP is an upcoming RFC
defining data types for headers and trailers.
This new package implements the specification.

New methods are also added to the Header type to manipulate structured
values.

.gitmodules

@@ -0,0 +1,3 @@
+[submodule "src/net/http/sfv/structured-field-tests"]
+	path = src/net/http/sfv/structured-field-tests
+	url = https://github.com/httpwg/structured-field-tests

src/go/build/deps_test.go

@@ -414,6 +414,16 @@ var depsRules = `
 	< golang.org/x/net/idna
 	< golang.org/x/net/http/httpguts, golang.org/x/net/http/httpproxy;
 
+	encoding/base64,
+	errors,
+	fmt,
+	io,
+	math,
+	reflect,
+	strconv,
+	strings
+	< net/http/sfv;
+
 	NET, crypto/tls
 	< net/http/httptrace;
 
@@ -423,6 +433,7 @@ var depsRules = `
 	golang.org/x/net/http2/hpack,
 	net/http/internal,
 	net/http/httptrace,
+	net/http/sfv,
 	mime/multipart,
 	log
 	< net/http;

src/net/http/header.go

@@ -7,6 +7,7 @@ package http
 import (
 	"io"
 	"net/http/httptrace"
+	"net/http/sfv"
 	"net/textproto"
 	"sort"
 	"strings"
@@ -37,6 +38,24 @@ func (h Header) Set(key, value string) {
 	textproto.MIMEHeader(h).Set(key, value)
 }
 
+// SetStructured sets the header entries associated with key to the
+// given structured value.
+// It encodes the structured value as text before setting it.
+// It replaces any existing values associated with key.
+// The key is case insensitive; it is canonicalized by
+// textproto.CanonicalMIMEHeaderKey.
+// To use non-canonical keys, assign to the map directly.
+func (h Header) SetStructured(key string, value sfv.StructuredFieldValue) error {
+	v, err := sfv.Marshal(value)
+	if err != nil {
+		return err
+	}
+
+	h.Set(key, v)
+
+	return nil
+}
+
 // Get gets the first value associated with the given key. If
 // there are no values associated with the key, Get returns "".
 // It is case insensitive; textproto.CanonicalMIMEHeaderKey is
@@ -46,6 +65,42 @@ func (h Header) Get(key string) string {
 	return textproto.MIMEHeader(h).Get(key)
 }
 
+// GetItem returns the item
+// (according to the Structured Field Values specification)
+// associated with the headers having the given key.
+// If the key doesn't exist or if the value format
+// is not a valid item, an error is returned.
+// It is case insensitive; textproto.CanonicalMIMEHeaderKey is
+// used to canonicalize the provided key. To use non-canonical keys,
+// access the map directly.
+func (h Header) GetItem(key string) (sfv.Item, error) {
+	return sfv.UnmarshalItem(h.Values(key))
+}
+
+// GetList returns the list
+// (according to the Structured Field Values specification)
+// associated with the headers having the given key.
+// If the key doesn't exist or if the value format
+// is not a valid list, an error is returned.
+// It is case insensitive; textproto.CanonicalMIMEHeaderKey is
+// used to canonicalize the provided key. To use non-canonical keys,
+// access the map directly.
+func (h Header) GetList(key string) (sfv.List, error) {
+	return sfv.UnmarshalList(h.Values(key))
+}
+
+// GetDictionary returns the dictionary
+// (according to the Structured Field Values specification)
+// associated with the given key.
+// If the key doesn't exist or if the value format
+// is not a valid dictionary, an error is returned.
+// It is case insensitive; textproto.CanonicalMIMEHeaderKey is
+// used to canonicalize the provided key. To use non-canonical keys,
+// access the map directly.
+func (h Header) GetDictionary(key string) (*sfv.Dictionary, error) {
+	return sfv.UnmarshalDictionary(h.Values(key))
+}
+
 // Values returns all values associated with the given key.
 // It is case insensitive; textproto.CanonicalMIMEHeaderKey is
 // used to canonicalize the provided key. To use non-canonical

src/net/http/header_test.go

@@ -7,6 +7,7 @@ package http
 import (
 	"bytes"
 	"internal/race"
+	"net/http/sfv"
 	"reflect"
 	"runtime"
 	"testing"
@@ -251,3 +252,63 @@ func TestCloneOrMakeHeader(t *testing.T) {
 		})
 	}
 }
+
+func TestSetStructured(t *testing.T) {
+	bar := sfv.NewItem(sfv.Token("bar"))
+	bar.Params.Add("baz", 42)
+
+	l := sfv.List{
+		bar,
+		sfv.NewItem(false),
+	}
+
+	d := sfv.NewDictionary()
+	d.Add("a", bar)
+	d.Add("b", sfv.NewItem(false))
+
+	tests := []struct {
+		key        string
+		value      sfv.StructuredFieldValue
+		err        bool
+		serialized string
+	}{
+		{"Item", sfv.NewItem("bar"), false, `"bar"`},
+		{"List", l, false, `bar;baz=42, ?0`},
+		{"Dict", d, false, `a=bar;baz=42, b=?0`},
+		{"Dict", sfv.NewItem(999999999999999999), true, ""},
+	}
+
+	h := Header{}
+	for _, tt := range tests {
+		err := h.SetStructured(tt.key, tt.value) != nil
+		if err != tt.err {
+			t.Errorf("Got:  %#v\nWant: %#v", err, tt.err)
+		}
+
+		if err {
+			continue
+		}
+
+		s := h.Get(tt.key)
+		if s != tt.serialized {
+			t.Errorf("Got:  %#v\nWant: %#v", s, tt.serialized)
+		}
+
+		var r sfv.StructuredFieldValue
+		switch tt.value.(type) {
+		case sfv.Item:
+			r, _ = h.GetItem(tt.key)
+		case sfv.List:
+			r, _ = h.GetList(tt.key)
+		case *sfv.Dictionary:
+			r, _ = h.GetDictionary(tt.key)
+		default:
+			panic("type not found")
+		}
+
+		s, _ = sfv.Marshal(r)
+		if s != tt.serialized {
+			t.Errorf("Got:  %#v\nWant: %#v", s, tt.serialized)
+		}
+	}
+}

src/net/http/sfv/bareitem.go

@@ -0,0 +1,106 @@
+// Copyright 2020 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 sfv
+
+import (
+	"errors"
+	"fmt"
+	"reflect"
+	"strings"
+)
+
+// ErrInvalidBareItem is returned when a bare item is invalid.
+var ErrInvalidBareItem = errors.New(
+	"invalid bare item type (allowed types are bool, string, int64, float64, []byte and Token)",
+)
+
+// assertBareItem asserts that v is a valid bare item
+// according to https://httpwg.org/http-extensions/draft-ietf-httpbis-header-structure.html#item.
+//
+// v can be either:
+//
+// * an integer (Section 3.3.1.)
+// * a decimal (Section 3.3.2.)
+// * a string (Section 3.3.3.)
+// * a token (Section 3.3.4.)
+// * a byte sequence (Section 3.3.5.)
+// * a boolean (Section 3.3.6.)
+func assertBareItem(v interface{}) {
+	switch v.(type) {
+	case bool,
+		string,
+		int,
+		int8,
+		int16,
+		int32,
+		int64,
+		uint,
+		uint8,
+		uint16,
+		uint32,
+		uint64,
+		float32,
+		float64,
+		[]byte,
+		Token:
+		return
+	default:
+		panic(fmt.Errorf("%w: got %s", ErrInvalidBareItem, reflect.TypeOf(v)))
+	}
+}
+
+// marshalBareItem serializes as defined in
+// https://httpwg.org/http-extensions/draft-ietf-httpbis-header-structure.html#ser-bare-item.
+func marshalBareItem(b *strings.Builder, v interface{}) error {
+	switch v := v.(type) {
+	case bool:
+		return marshalBoolean(b, v)
+	case string:
+		return marshalString(b, v)
+	case int64:
+		return marshalInteger(b, v)
+	case int, int8, int16, int32:
+		return marshalInteger(b, reflect.ValueOf(v).Int())
+	case uint, uint8, uint16, uint32, uint64:
+		// Casting an uint64 to an int64 is possible because the maximum allowed value is 999,999,999,999,999
+		return marshalInteger(b, int64(reflect.ValueOf(v).Uint()))
+	case float32, float64:
+		return marshalDecimal(b, v.(float64))
+	case []byte:
+		return marshalBinary(b, v)
+	case Token:
+		return v.marshalSFV(b)
+	default:
+		panic(ErrInvalidBareItem)
+	}
+}
+
+// parseBareItem parses as defined in
+// https://httpwg.org/http-extensions/draft-ietf-httpbis-header-structure.html#parse-bare-item.
+func parseBareItem(s *scanner) (interface{}, error) {
+	if s.eof() {
+		return nil, &UnmarshalError{s.off, ErrUnexpectedEndOfString}
+	}
+
+	c := s.data[s.off]
+	switch c {
+	case '"':
+		return parseString(s)
+	case '?':
+		return parseBoolean(s)
+	case '*':
+		return parseToken(s)
+	case ':':
+		return parseBinary(s)
+	case '-', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9':
+		return parseNumber(s)
+	default:
+		if isAlpha(c) {
+			return parseToken(s)
+		}
+
+		return nil, &UnmarshalError{s.off, ErrUnrecognizedCharacter}
+	}
+}

src/net/http/sfv/bareitem_test.go

@@ -0,0 +1,65 @@
+// Copyright 2020 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 sfv
+
+import (
+	"reflect"
+	"strings"
+	"testing"
+	"time"
+)
+
+func TestParseBareItem(t *testing.T) {
+	data := []struct {
+		in  string
+		out interface{}
+		err bool
+	}{
+		{"?1", true, false},
+		{"?0", false, false},
+		{"22", int64(22), false},
+		{"-2.2", -2.2, false},
+		{`"foo"`, "foo", false},
+		{"abc", Token("abc"), false},
+		{"*abc", Token("*abc"), false},
+		{":YWJj:", []byte("abc"), false},
+		{"", nil, true},
+		{"~", nil, true},
+	}
+
+	for _, d := range data {
+		s := &scanner{data: d.in}
+
+		i, err := parseBareItem(s)
+		if d.err && err == nil {
+			t.Errorf("parseBareItem(%s): error expected", d.in)
+		}
+
+		if !d.err && !reflect.DeepEqual(d.out, i) {
+			t.Errorf("parseBareItem(%s) = %v, %v; %v, <nil> expected", d.in, i, err, d.out)
+		}
+	}
+}
+
+func TestMarshalBareItem(t *testing.T) {
+	defer func() {
+		if r := recover(); r == nil {
+			t.Errorf("The code did not panic")
+		}
+	}()
+
+	var b strings.Builder
+	_ = marshalBareItem(&b, time.Second)
+}
+
+func TestAssertBareItem(t *testing.T) {
+	defer func() {
+		if r := recover(); r == nil {
+			t.Errorf("The code did not panic")
+		}
+	}()
+
+	assertBareItem(time.Second)
+}