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Encode structs directly to output buffer.
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For variable-length structs (structs with omitempty fields), encoding to the unused capacity at the
end of the output buffer while counting nonempty items is cheaper than using a separate temporary
buffer (no pool interactions and better spatial locality). Copying the items can be avoided entirely
by reserving space in the output buffer for the head if the encoded length of the head can be
predicted before checking optional fields.

                                                                     │ before.txt  │              after.txt              │
                                                                     │   sec/op    │   sec/op     vs base                │
Marshal/Go_struct_to_CBOR_map                                          1.404µ ± 0%   1.408µ ± 1%        ~ (p=0.170 n=10)
Marshal/Go_struct_many_fields_all_omitempty_all_empty_to_CBOR_map      443.8n ± 0%   430.6n ± 0%   -2.99% (p=0.000 n=10)
Marshal/Go_struct_some_fields_all_omitempty_all_empty_to_CBOR_map      181.7n ± 0%   163.5n ± 0%  -10.04% (p=0.000 n=10)
Marshal/Go_struct_many_fields_all_omitempty_all_nonempty_to_CBOR_map   813.5n ± 0%   784.8n ± 0%   -3.53% (p=0.000 n=10)
Marshal/Go_struct_some_fields_all_omitempty_all_nonempty_to_CBOR_map   300.8n ± 0%   275.4n ± 0%   -8.43% (p=0.000 n=10)
Marshal/Go_struct_many_fields_one_omitempty_to_CBOR_map                763.8n ± 0%   727.7n ± 0%   -4.73% (p=0.000 n=10)
Marshal/Go_struct_some_fields_one_omitempty_to_CBOR_map                284.2n ± 0%   257.6n ± 0%   -9.36% (p=0.000 n=10)
Marshal/Go_struct_keyasint_to_CBOR_map                                 1.422µ ± 0%   1.414µ ± 1%   -0.56% (p=0.029 n=10)
Marshal/Go_struct_toarray_to_CBOR_array                                1.341µ ± 1%   1.338µ ± 1%        ~ (p=0.340 n=10)
MarshalCanonical/Go_struct_to_CBOR_map                                 386.4n ± 0%   392.4n ± 0%   +1.57% (p=0.000 n=10)
MarshalCanonical/Go_struct_to_CBOR_map_canonical                       386.9n ± 0%   384.8n ± 0%   -0.52% (p=0.001 n=10)
geomean                                                                560.5n        540.4n        -3.59%

                                                                     │ before.txt │              after.txt              │
                                                                     │    B/op    │    B/op     vs base                 │
Marshal/Go_struct_to_CBOR_map                                          208.0 ± 0%   208.0 ± 0%       ~ (p=1.000 n=10) ¹
Marshal/Go_struct_many_fields_all_omitempty_all_empty_to_CBOR_map      1.000 ± 0%   1.000 ± 0%       ~ (p=1.000 n=10) ¹
Marshal/Go_struct_some_fields_all_omitempty_all_empty_to_CBOR_map      1.000 ± 0%   1.000 ± 0%       ~ (p=1.000 n=10) ¹
Marshal/Go_struct_many_fields_all_omitempty_all_nonempty_to_CBOR_map   176.0 ± 0%   176.0 ± 0%       ~ (p=1.000 n=10) ¹
Marshal/Go_struct_some_fields_all_omitempty_all_nonempty_to_CBOR_map   48.00 ± 0%   48.00 ± 0%       ~ (p=1.000 n=10) ¹
Marshal/Go_struct_many_fields_one_omitempty_to_CBOR_map                160.0 ± 0%   160.0 ± 0%       ~ (p=1.000 n=10) ¹
Marshal/Go_struct_some_fields_one_omitempty_to_CBOR_map                48.00 ± 0%   48.00 ± 0%       ~ (p=1.000 n=10) ¹
Marshal/Go_struct_keyasint_to_CBOR_map                                 192.0 ± 0%   192.0 ± 0%       ~ (p=1.000 n=10) ¹
Marshal/Go_struct_toarray_to_CBOR_array                                192.0 ± 0%   192.0 ± 0%       ~ (p=1.000 n=10) ¹
MarshalCanonical/Go_struct_to_CBOR_map                                 64.00 ± 0%   64.00 ± 0%       ~ (p=1.000 n=10) ¹
MarshalCanonical/Go_struct_to_CBOR_map_canonical                       64.00 ± 0%   64.00 ± 0%       ~ (p=1.000 n=10) ¹
geomean                                                                46.18        46.18       +0.00%
¹ all samples are equal

                                                                     │ before.txt │              after.txt              │
                                                                     │ allocs/op  │ allocs/op   vs base                 │
Marshal/Go_struct_to_CBOR_map                                          1.000 ± 0%   1.000 ± 0%       ~ (p=1.000 n=10) ¹
Marshal/Go_struct_many_fields_all_omitempty_all_empty_to_CBOR_map      1.000 ± 0%   1.000 ± 0%       ~ (p=1.000 n=10) ¹
Marshal/Go_struct_some_fields_all_omitempty_all_empty_to_CBOR_map      1.000 ± 0%   1.000 ± 0%       ~ (p=1.000 n=10) ¹
Marshal/Go_struct_many_fields_all_omitempty_all_nonempty_to_CBOR_map   1.000 ± 0%   1.000 ± 0%       ~ (p=1.000 n=10) ¹
Marshal/Go_struct_some_fields_all_omitempty_all_nonempty_to_CBOR_map   1.000 ± 0%   1.000 ± 0%       ~ (p=1.000 n=10) ¹
Marshal/Go_struct_many_fields_one_omitempty_to_CBOR_map                1.000 ± 0%   1.000 ± 0%       ~ (p=1.000 n=10) ¹
Marshal/Go_struct_some_fields_one_omitempty_to_CBOR_map                1.000 ± 0%   1.000 ± 0%       ~ (p=1.000 n=10) ¹
Marshal/Go_struct_keyasint_to_CBOR_map                                 1.000 ± 0%   1.000 ± 0%       ~ (p=1.000 n=10) ¹
Marshal/Go_struct_toarray_to_CBOR_array                                1.000 ± 0%   1.000 ± 0%       ~ (p=1.000 n=10) ¹
MarshalCanonical/Go_struct_to_CBOR_map                                 1.000 ± 0%   1.000 ± 0%       ~ (p=1.000 n=10) ¹
MarshalCanonical/Go_struct_to_CBOR_map_canonical                       1.000 ± 0%   1.000 ± 0%       ~ (p=1.000 n=10) ¹
geomean                                                                1.000        1.000       +0.00%
¹ all samples are equal

Signed-off-by: Ben Luddy <bluddy@redhat.com>
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@benluddy
benluddy committed Apr 29, 2024
1 parent da82dfa commit d981dec
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Showing 4 changed files with 181 additions and 14 deletions.
70 changes: 70 additions & 0 deletions bench_test.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -107,6 +107,65 @@ type T3 struct {
Mss map[string]string
}

type ManyFieldsOneOmitEmpty struct {
F01, F02, F03, F04, F05, F06, F07, F08, F09, F10, F11, F12, F13, F14, F15, F16 int
F17, F18, F19, F20, F21, F22, F23, F24, F25, F26, F27, F28, F29, F30, F31 int

F32 int `cbor:",omitempty"`
}

type SomeFieldsOneOmitEmpty struct {
F01, F02, F03, F04, F05, F06, F07 int

F08 int `cbor:",omitempty"`
}

type ManyFieldsAllOmitEmpty struct {
F01 int `cbor:",omitempty"`
F02 int `cbor:",omitempty"`
F03 int `cbor:",omitempty"`
F04 int `cbor:",omitempty"`
F05 int `cbor:",omitempty"`
F06 int `cbor:",omitempty"`
F07 int `cbor:",omitempty"`
F08 int `cbor:",omitempty"`
F09 int `cbor:",omitempty"`
F10 int `cbor:",omitempty"`
F11 int `cbor:",omitempty"`
F12 int `cbor:",omitempty"`
F13 int `cbor:",omitempty"`
F14 int `cbor:",omitempty"`
F15 int `cbor:",omitempty"`
F16 int `cbor:",omitempty"`
F17 int `cbor:",omitempty"`
F18 int `cbor:",omitempty"`
F19 int `cbor:",omitempty"`
F20 int `cbor:",omitempty"`
F21 int `cbor:",omitempty"`
F22 int `cbor:",omitempty"`
F23 int `cbor:",omitempty"`
F24 int `cbor:",omitempty"`
F25 int `cbor:",omitempty"`
F26 int `cbor:",omitempty"`
F27 int `cbor:",omitempty"`
F28 int `cbor:",omitempty"`
F29 int `cbor:",omitempty"`
F30 int `cbor:",omitempty"`
F31 int `cbor:",omitempty"`
F32 int `cbor:",omitempty"`
}

type SomeFieldsAllOmitEmpty struct {
F01 int `cbor:",omitempty"`
F02 int `cbor:",omitempty"`
F03 int `cbor:",omitempty"`
F04 int `cbor:",omitempty"`
F05 int `cbor:",omitempty"`
F06 int `cbor:",omitempty"`
F07 int `cbor:",omitempty"`
F08 int `cbor:",omitempty"`
}

var decodeBenchmarks = []struct {
name string
data []byte
Expand Down Expand Up @@ -396,6 +455,17 @@ func BenchmarkMarshal(b *testing.B) {
}{
{"Go map[string]interface{} to CBOR map", m1},
{"Go struct to CBOR map", v1},
{"Go struct many fields all omitempty all empty to CBOR map", ManyFieldsAllOmitEmpty{}},
{"Go struct some fields all omitempty all empty to CBOR map", SomeFieldsAllOmitEmpty{}},
{"Go struct many fields all omitempty all nonempty to CBOR map", ManyFieldsAllOmitEmpty{
F01: 1, F02: 1, F03: 1, F04: 1, F05: 1, F06: 1, F07: 1, F08: 1, F09: 1, F10: 1, F11: 1, F12: 1, F13: 1, F14: 1, F15: 1, F16: 1,
F17: 1, F18: 1, F19: 1, F20: 1, F21: 1, F22: 1, F23: 1, F24: 1, F25: 1, F26: 1, F27: 1, F28: 1, F29: 1, F30: 1, F31: 1, F32: 1,
}},
{"Go struct some fields all omitempty all nonempty to CBOR map", SomeFieldsAllOmitEmpty{
F01: 1, F02: 1, F03: 1, F04: 1, F05: 1, F06: 1, F07: 1, F08: 1,
}},
{"Go struct many fields one omitempty to CBOR map", ManyFieldsOneOmitEmpty{}},
{"Go struct some fields one omitempty to CBOR map", SomeFieldsOneOmitEmpty{}},
{"Go map[int]interface{} to CBOR map", m2},
{"Go struct keyasint to CBOR map", v2},
{"Go []interface{} to CBOR map", slc},
Expand Down
9 changes: 9 additions & 0 deletions cache.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -171,6 +171,7 @@ type encodingStructType struct {
err error
toArray bool
fixedLength bool // Struct type doesn't have any omitempty or anonymous fields.
maxHeadLen int
}

func (st *encodingStructType) getFields(em *encMode) fields {
Expand Down Expand Up @@ -231,6 +232,8 @@ func getEncodingStructType(t reflect.Type) (*encodingStructType, error) {
return getEncodingStructToArrayType(t, flds)
}

nOptional := 0

var err error
var hasKeyAsInt bool
var hasKeyAsStr bool
Expand Down Expand Up @@ -293,6 +296,10 @@ func getEncodingStructType(t reflect.Type) (*encodingStructType, error) {
fixedLength = false
omitEmptyIdx = append(omitEmptyIdx, i)
}

if len(flds[i].idx) > 1 || flds[i].omitEmpty {
nOptional++
}
}
putEncoderBuffer(e)

Expand Down Expand Up @@ -320,7 +327,9 @@ func getEncodingStructType(t reflect.Type) (*encodingStructType, error) {
lengthFirstFields: lengthFirstFields,
omitEmptyFieldsIdx: omitEmptyIdx,
fixedLength: fixedLength,
maxHeadLen: encodedHeadLen(uint64(len(flds))),
}

encodingStructTypeCache.Store(t, structType)
return structType, structType.err
}
Expand Down
64 changes: 50 additions & 14 deletions encode.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1297,12 +1297,17 @@ func encodeStruct(e *encoderBuffer, em *encMode, v reflect.Value) (err error) {
start = rand.Intn(len(flds)) //nolint:gosec // Don't need a CSPRNG for deck cutting.
}

kve := getEncoderBuffer() // encode key-value pairs based on struct field tag options
kvcount := 0
if b := em.encTagBytes(v.Type()); b != nil {
e.Write(b)
}

// Reserve space in the output buffer for the head if its encoded size is fixed.
encodeHead(e, byte(cborTypeMap), uint64(len(flds)))

kvbegin := e.Len()
kvcount := 0
for offset := 0; offset < len(flds); offset++ {
i := (start + offset) % len(flds)
f := flds[i]
f := flds[(start+offset)%len(flds)]

var fv reflect.Value
if len(f.idx) == 1 {
Expand All @@ -1320,7 +1325,6 @@ func encodeStruct(e *encoderBuffer, em *encMode, v reflect.Value) (err error) {
if f.omitEmpty {
empty, err := f.ief(em, fv)
if err != nil {
putEncoderBuffer(kve)
return err
}
if empty {
Expand All @@ -1329,26 +1333,42 @@ func encodeStruct(e *encoderBuffer, em *encMode, v reflect.Value) (err error) {
}

if !f.keyAsInt && em.fieldName == FieldNameToByteString {
kve.Write(f.cborNameByteString)
e.Write(f.cborNameByteString)
} else { // int or text string
kve.Write(f.cborName)
e.Write(f.cborName)
}

if err := f.ef(kve, em, fv); err != nil {
putEncoderBuffer(kve)
if err := f.ef(e, em, fv); err != nil {
return err
}

kvcount++
}

if b := em.encTagBytes(v.Type()); b != nil {
e.Write(b)
// Overwrite the bytes that were reserved for the head before encoding the map entries.
{
headbuf := encoderBuffer{Buffer: *bytes.NewBuffer(e.Bytes()[kvbegin-structType.maxHeadLen : kvbegin-structType.maxHeadLen : kvbegin])}
encodeHead(&headbuf, byte(cborTypeMap), uint64(kvcount))
}

actualHeadLen := encodedHeadLen(uint64(kvcount))
if actualHeadLen == structType.maxHeadLen {
// The bytes reserved for the encoded head were exactly the right size, so the
// encoded entries are already in their final positions.
return nil
}

encodeHead(e, byte(cborTypeMap), uint64(kvcount))
e.Write(kve.Bytes())
// We reserved more bytes than needed for the encoded head, based on the number of fields
// encoded. The encoded entries are offset to the right by the number of excess reserved
// bytes. Shift the entries left to remove the gap.
excessReservedBytes := structType.maxHeadLen - actualHeadLen
dst := e.Bytes()[kvbegin-excessReservedBytes : e.Len()-excessReservedBytes]
src := e.Bytes()[kvbegin:e.Len()]
copy(dst, src)

putEncoderBuffer(kve)
// After shifting, the excess bytes are at the end of the output buffer and they are
// garbage.
e.Truncate(e.Len() - excessReservedBytes)
return nil
}

Expand Down Expand Up @@ -1527,6 +1547,22 @@ func encodeHead(e *encoderBuffer, t byte, n uint64) {
e.Write(e.scratch[:9])
}

// encodedHeadLen returns the number of bytes that will be written by a call to encodeHead with the
// given argument. This must be kept in sync with encodeHead.
func encodedHeadLen(arg uint64) int {
switch {
case arg <= 23:
return 1
case arg <= math.MaxUint8:
return 2
case arg <= math.MaxUint16:
return 3
case arg <= math.MaxUint32:
return 5
}
return 9
}

var (
typeMarshaler = reflect.TypeOf((*Marshaler)(nil)).Elem()
typeBinaryMarshaler = reflect.TypeOf((*encoding.BinaryMarshaler)(nil)).Elem()
Expand Down
52 changes: 52 additions & 0 deletions encode_test.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -550,6 +550,58 @@ func TestMarshalStruct(t *testing.T) {
t.Errorf("Unmarshal() = %v, want %v", v2, unmarshalWant)
}
}

// TestMarshalStructVariableLength tests marshaling structs that can encode to CBOR maps of varying
// size depending on their field contents.
func TestMarshalStructVariableLength(t *testing.T) {
for _, tc := range []struct {
name string
in interface{}
want []byte
}{
{
name: "zero out of one items",
in: struct {
F int `cbor:",omitempty"`
}{},
want: hexDecode("a0"),
},
{
name: "one out of one items",
in: struct {
F int `cbor:",omitempty"`
}{F: 1},
want: hexDecode("a1614601"),
},
{
name: "23 out of 24 items",
in: struct {
A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W int
X int `cbor:",omitempty"`
}{},
want: hexDecode("b7614100614200614300614400614500614600614700614800614900614a00614b00614c00614d00614e00614f00615000615100615200615300615400615500615600615700"),
},
{
name: "24 out of 24 items",
in: struct {
A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W int
X int `cbor:",omitempty"`
}{X: 1},
want: hexDecode("b818614100614200614300614400614500614600614700614800614900614a00614b00614c00614d00614e00614f00615000615100615200615300615400615500615600615700615801"),
},
} {
t.Run(tc.name, func(t *testing.T) {
got, err := Marshal(tc.in)
if err != nil {
t.Fatal(err)
}
if !bytes.Equal(tc.want, got) {
t.Errorf("want 0x%x but got 0x%x", tc.want, got)
}
})
}
}

func TestMarshalStructCanonical(t *testing.T) {
v := outer{
IntField: 123,
Expand Down

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