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stupidgcm: cache C.EVP_chacha20_poly1305()

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2% performance improvement, almost for free.

gocryptfs/internal/speed$ benchstat old new
name             old time/op   new time/op   delta
StupidXchacha-4   5.82µs ± 0%   5.68µs ± 0%  -2.37%  (p=0.008 n=5+5)

name             old speed     new speed     delta
StupidXchacha-4  704MB/s ± 0%  721MB/s ± 0%  +2.43%  (p=0.008 n=5+5)
This commit is contained in:
Jakob Unterwurzacher 2021-09-07 12:34:47 +02:00
parent 6a0206897c
commit f89b14ee3d
1 changed files with 15 additions and 1 deletions
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16
internal/stupidgcm/chacha.go
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@ -21,6 +21,20 @@ type stupidChacha20poly1305 struct {
// Verify that we satisfy the cipher.AEAD interface
var _ cipher.AEAD = &stupidChacha20poly1305{}
// _EVP_chacha20_poly1305 caches C.EVP_chacha20_poly1305() to avoid the Cgo call
// overhead for each instantiation of NewChacha20poly1305.
var _EVP_chacha20_poly1305 *C.EVP_CIPHER
func init() {
_EVP_chacha20_poly1305 = C.EVP_chacha20_poly1305()
}
// NewChacha20poly1305 returns a new instance of the OpenSSL ChaCha20-Poly1305 AEAD
// cipher ( https://www.openssl.org/docs/man1.1.1/man3/EVP_chacha20_poly1305.html ).
//
// gocryptfs only uses ChaCha20-Poly1305 as a building block for OpenSSL
// XChaCha20-Poly1305. This function is hot because it gets called once for each
// block by XChaCha20-Poly1305.
func NewChacha20poly1305(key []byte) *stupidChacha20poly1305 {
if len(key) != chacha20poly1305.KeySize {
log.Panicf("Only %d-byte keys are supported, you passed %d bytes", chacha20poly1305.KeySize, len(key))
@ -28,7 +42,7 @@ func NewChacha20poly1305(key []byte) *stupidChacha20poly1305 {
return &stupidChacha20poly1305{
stupidAEADCommon{
key: append([]byte{}, key...), // private copy
openSSLEVPCipher: C.EVP_chacha20_poly1305(),
openSSLEVPCipher: _EVP_chacha20_poly1305,
nonceSize: chacha20poly1305.NonceSize,
},
}