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rlp: optimize big.Int decoding for size <= 32 bytes (#22927)

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This change grows the static integer buffer in Stream to 32 bytes,
making it possible to decode 256bit integers without allocating a
temporary buffer.

In the recent commit 088da24, Stream struct size decreased from 120
bytes down to 88 bytes. This commit grows the struct to 112 bytes again,
but the size change will not degrade performance because Stream
instances are internally cached in sync.Pool.

    name             old time/op    new time/op    delta
    DecodeBigInts-8    12.2µs ± 0%     8.6µs ± 4%  -29.58%  (p=0.000 n=9+10)

    name             old speed      new speed      delta
    DecodeBigInts-8   230MB/s ± 0%   326MB/s ± 4%  +42.04%  (p=0.000 n=9+10)
This commit is contained in:
Felix Lange
2021-05-25 21:56:25 +02:00
committed by GitHub
parent 017cf71fbd
commit 4d33de9b49
3 changed files with 74 additions and 16 deletions
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22
rlp/decode_test.go
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@ -329,6 +329,11 @@ type recstruct struct {
Child *recstruct `rlp:"nil"`
}
type bigIntStruct struct {
I *big.Int
B string
}
type invalidNilTag struct {
X []byte `rlp:"nil"`
}
@ -405,10 +410,11 @@ type ignoredField struct {
}
var (
veryBigInt = big.NewInt(0).Add(
veryBigInt = new(big.Int).Add(
big.NewInt(0).Lsh(big.NewInt(0xFFFFFFFFFFFFFF), 16),
big.NewInt(0xFFFF),
)
veryVeryBigInt = new(big.Int).Exp(veryBigInt, big.NewInt(8), nil)
)
var decodeTests = []decodeTest{
@ -479,12 +485,15 @@ var decodeTests = []decodeTest{
{input: "C0", ptr: new(string), error: "rlp: expected input string or byte for string"},
// big ints
{input: "80", ptr: new(*big.Int), value: big.NewInt(0)},
{input: "01", ptr: new(*big.Int), value: big.NewInt(1)},
{input: "89FFFFFFFFFFFFFFFFFF", ptr: new(*big.Int), value: veryBigInt},
{input: "B848FFFFFFFFFFFFFFFFF800000000000000001BFFFFFFFFFFFFFFFFC8000000000000000045FFFFFFFFFFFFFFFFC800000000000000001BFFFFFFFFFFFFFFFFF8000000000000000001", ptr: new(*big.Int), value: veryVeryBigInt},
{input: "10", ptr: new(big.Int), value: *big.NewInt(16)}, // non-pointer also works
{input: "C0", ptr: new(*big.Int), error: "rlp: expected input string or byte for *big.Int"},
{input: "820001", ptr: new(big.Int), error: "rlp: non-canonical integer (leading zero bytes) for *big.Int"},
{input: "8105", ptr: new(big.Int), error: "rlp: non-canonical size information for *big.Int"},
{input: "00", ptr: new(*big.Int), error: "rlp: non-canonical integer (leading zero bytes) for *big.Int"},
{input: "820001", ptr: new(*big.Int), error: "rlp: non-canonical integer (leading zero bytes) for *big.Int"},
{input: "8105", ptr: new(*big.Int), error: "rlp: non-canonical size information for *big.Int"},
// structs
{
@ -497,6 +506,13 @@ var decodeTests = []decodeTest{
ptr: new(recstruct),
value: recstruct{1, &recstruct{2, &recstruct{3, nil}}},
},
{
// This checks that empty big.Int works correctly in struct context. It's easy to
// miss the update of s.kind for this case, so it needs its own test.
input: "C58083343434",
ptr: new(bigIntStruct),
value: bigIntStruct{new(big.Int), "444"},
},
// struct errors
{