vendor: Move back to upstream KCP (fixes #4407)

GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/4614

vendor/github.com/klauspost/reedsolomon/options.go

@@ -0,0 +1,111 @@
+package reedsolomon
+
+import (
+	"runtime"
+
+	"github.com/klauspost/cpuid"
+)
+
+// Option allows to override processing parameters.
+type Option func(*options)
+
+type options struct {
+	maxGoroutines              int
+	minSplitSize               int
+	useAVX2, useSSSE3, useSSE2 bool
+	usePAR1Matrix              bool
+	useCauchy                  bool
+	shardSize                  int
+}
+
+var defaultOptions = options{
+	maxGoroutines: 384,
+	minSplitSize:  1024,
+}
+
+func init() {
+	if runtime.GOMAXPROCS(0) <= 1 {
+		defaultOptions.maxGoroutines = 1
+	}
+	// Detect CPU capabilities.
+	defaultOptions.useSSSE3 = cpuid.CPU.SSSE3()
+	defaultOptions.useAVX2 = cpuid.CPU.AVX2()
+	defaultOptions.useSSE2 = cpuid.CPU.SSE2()
+}
+
+// WithMaxGoroutines is the maximum number of goroutines number for encoding & decoding.
+// Jobs will be split into this many parts, unless each goroutine would have to process
+// less than minSplitSize bytes (set with WithMinSplitSize).
+// For the best speed, keep this well above the GOMAXPROCS number for more fine grained
+// scheduling.
+// If n <= 0, it is ignored.
+func WithMaxGoroutines(n int) Option {
+	return func(o *options) {
+		if n > 0 {
+			o.maxGoroutines = n
+		}
+	}
+}
+
+// WithAutoGoroutines will adjust the number of goroutines for optimal speed with a
+// specific shard size.
+// Send in the shard size you expect to send. Other shard sizes will work, but may not
+// run at the optimal speed.
+// Overwrites WithMaxGoroutines.
+// If shardSize <= 0, it is ignored.
+func WithAutoGoroutines(shardSize int) Option {
+	return func(o *options) {
+		o.shardSize = shardSize
+	}
+}
+
+// WithMinSplitSize is the minimum encoding size in bytes per goroutine.
+// See WithMaxGoroutines on how jobs are split.
+// If n <= 0, it is ignored.
+func WithMinSplitSize(n int) Option {
+	return func(o *options) {
+		if n > 0 {
+			o.minSplitSize = n
+		}
+	}
+}
+
+func withSSE3(enabled bool) Option {
+	return func(o *options) {
+		o.useSSSE3 = enabled
+	}
+}
+
+func withAVX2(enabled bool) Option {
+	return func(o *options) {
+		o.useAVX2 = enabled
+	}
+}
+
+func withSSE2(enabled bool) Option {
+	return func(o *options) {
+		o.useSSE2 = enabled
+	}
+}
+
+// WithPAR1Matrix causes the encoder to build the matrix how PARv1
+// does. Note that the method they use is buggy, and may lead to cases
+// where recovery is impossible, even if there are enough parity
+// shards.
+func WithPAR1Matrix() Option {
+	return func(o *options) {
+		o.usePAR1Matrix = true
+		o.useCauchy = false
+	}
+}
+
+// WithCauchyMatrix will make the encoder build a Cauchy style matrix.
+// The output of this is not compatible with the standard output.
+// A Cauchy matrix is faster to generate. This does not affect data throughput,
+// but will result in slightly faster start-up time.
+func WithCauchyMatrix() Option {
+	return func(o *options) {
+		o.useCauchy = true
+		o.usePAR1Matrix = false
+	}
+}