package simplest import ( "io" ) // xorBytes computes c = a xor b. func xorBytes(a, b [DigestSize]byte) (c [DigestSize]byte) { for i := 0; i < DigestSize; i++ { c[i] = a[i] ^ b[i] } return } // initChoice initializes the receiver's choice array from the PackedRandomChoiceBits array func (receiver *Receiver) initChoice() { // unpack the random values in PackedRandomChoiceBits into bits in Choice receiver.Output.RandomChoiceBits = make([]int, receiver.batchSize) for i := 0; i < len(receiver.Output.RandomChoiceBits); i++ { receiver.Output.RandomChoiceBits[i] = int(ExtractBitFromByteVector(receiver.Output.PackedRandomChoiceBits, i)) } } // ExtractBitFromByteVector interprets the byte-vector `vector` as if it were a _bit_-vector with len(vector) * 8 bits. // it extracts the `index`th such bit, interpreted in the little-endian way (i.e., both across bytes and within bytes). func ExtractBitFromByteVector(vector []byte, index int) byte { // the bitwise tricks index >> 3 == index // 8 and index & 0x07 == index % 8 are designed to avoid CPU division. return vector[index>>3] >> (index & 0x07) & 0x01 } type pipeWrapper struct { r *io.PipeReader w *io.PipeWriter exchanged int // used this during testing, to track bytes exchanged } func (wrapper *pipeWrapper) Write(p []byte) (n int, err error) { n, err = wrapper.w.Write(p) wrapper.exchanged += n return } func (wrapper *pipeWrapper) Read(p []byte) (n int, err error) { n, err = wrapper.r.Read(p) wrapper.exchanged += n return } func NewPipeWrappers() (*pipeWrapper, *pipeWrapper) { leftOut, leftIn := io.Pipe() rightOut, rightIn := io.Pipe() return &pipeWrapper{r: leftOut, w: rightIn}, &pipeWrapper{r: rightOut, w: leftIn} }