diff options
Diffstat (limited to 'vendor/golang.org/x/crypto/internal/chacha20/xor.go')
-rw-r--r-- | vendor/golang.org/x/crypto/internal/chacha20/xor.go | 43 |
1 files changed, 43 insertions, 0 deletions
diff --git a/vendor/golang.org/x/crypto/internal/chacha20/xor.go b/vendor/golang.org/x/crypto/internal/chacha20/xor.go new file mode 100644 index 000000000..9c5ba0b33 --- /dev/null +++ b/vendor/golang.org/x/crypto/internal/chacha20/xor.go @@ -0,0 +1,43 @@ +// Copyright 2018 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found src the LICENSE file. + +package chacha20 + +import ( + "runtime" +) + +// Platforms that have fast unaligned 32-bit little endian accesses. +const unaligned = runtime.GOARCH == "386" || + runtime.GOARCH == "amd64" || + runtime.GOARCH == "arm64" || + runtime.GOARCH == "ppc64le" || + runtime.GOARCH == "s390x" + +// xor reads a little endian uint32 from src, XORs it with u and +// places the result in little endian byte order in dst. +func xor(dst, src []byte, u uint32) { + _, _ = src[3], dst[3] // eliminate bounds checks + if unaligned { + // The compiler should optimize this code into + // 32-bit unaligned little endian loads and stores. + // TODO: delete once the compiler does a reliably + // good job with the generic code below. + // See issue #25111 for more details. + v := uint32(src[0]) + v |= uint32(src[1]) << 8 + v |= uint32(src[2]) << 16 + v |= uint32(src[3]) << 24 + v ^= u + dst[0] = byte(v) + dst[1] = byte(v >> 8) + dst[2] = byte(v >> 16) + dst[3] = byte(v >> 24) + } else { + dst[0] = src[0] ^ byte(u) + dst[1] = src[1] ^ byte(u>>8) + dst[2] = src[2] ^ byte(u>>16) + dst[3] = src[3] ^ byte(u>>24) + } +} |