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[dev.boringcrypto] crypto/internal/boring: avoid allocation in big.Int conversion
The conversion via byte slices is inefficient; we can convert via word slices and avoid the copy entirely. For #51940. Change-Id: I06f747e0acffffae427d9706d43bdacf146c027d Reviewed-on: https://go-review.googlesource.com/c/go/+/395875 Reviewed-by: Roland Shoemaker <roland@golang.org> Run-TryBot: Russ Cox <rsc@golang.org> TryBot-Result: Gopher Robot <gobot@golang.org>
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@ -18,6 +18,8 @@ import (
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"crypto/internal/boring/sig"
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_ "crypto/internal/boring/syso"
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"math/big"
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"math/bits"
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"unsafe"
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)
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const available = true
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@ -58,15 +60,26 @@ type fail string
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func (e fail) Error() string { return "boringcrypto: " + string(e) + " failed" }
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func wbase(b []big.Word) *C.uint8_t {
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if len(b) == 0 {
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return nil
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}
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return (*C.uint8_t)(unsafe.Pointer(&b[0]))
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}
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const wordBytes = bits.UintSize / 8
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func bigToBN(x *big.Int) *C.GO_BIGNUM {
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raw := x.Bytes()
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return C._goboringcrypto_BN_bin2bn(base(raw), C.size_t(len(raw)), nil)
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raw := x.Bits()
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return C._goboringcrypto_BN_le2bn(wbase(raw), C.size_t(len(raw)*wordBytes), nil)
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}
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func bnToBig(bn *C.GO_BIGNUM) *big.Int {
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raw := make([]byte, C._goboringcrypto_BN_num_bytes(bn))
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n := C._goboringcrypto_BN_bn2bin(bn, base(raw))
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return new(big.Int).SetBytes(raw[:n])
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raw := make([]big.Word, (C._goboringcrypto_BN_num_bytes(bn)+wordBytes-1)/wordBytes)
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if C._goboringcrypto_BN_bn2le_padded(wbase(raw), C.size_t(len(raw)*wordBytes), bn) == 0 {
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panic("boringcrypto: bignum conversion failed")
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}
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return new(big.Int).SetBits(raw)
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}
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func bigToBn(bnp **C.GO_BIGNUM, b *big.Int) bool {
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@ -77,8 +90,7 @@ func bigToBn(bnp **C.GO_BIGNUM, b *big.Int) bool {
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if b == nil {
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return true
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}
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raw := b.Bytes()
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bn := C._goboringcrypto_BN_bin2bn(base(raw), C.size_t(len(raw)), nil)
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bn := bigToBN(b)
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if bn == nil {
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return false
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}
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@ -141,7 +141,9 @@ unsigned _goboringcrypto_BN_num_bits(const GO_BIGNUM*);
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unsigned _goboringcrypto_BN_num_bytes(const GO_BIGNUM*);
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int _goboringcrypto_BN_is_negative(const GO_BIGNUM*);
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GO_BIGNUM* _goboringcrypto_BN_bin2bn(const uint8_t*, size_t, GO_BIGNUM*);
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GO_BIGNUM* _goboringcrypto_BN_le2bn(const uint8_t*, size_t, GO_BIGNUM*);
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size_t _goboringcrypto_BN_bn2bin(const GO_BIGNUM*, uint8_t*);
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int _goboringcrypto_BN_bn2le_padded(uint8_t*, size_t, const GO_BIGNUM*);
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// #include <openssl/ec.h>
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/*unchecked (opaque)*/ typedef struct GO_EC_GROUP { char data[1]; } GO_EC_GROUP;
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