did something

vendor/periph.io/x/host/v3/bcm283x/streams.go

@@ -0,0 +1,134 @@
+// Copyright 2017 The Periph Authors. All rights reserved.
+// Use of this source code is governed under the Apache License, Version 2.0
+// that can be found in the LICENSE file.
+
+package bcm283x
+
+import (
+	"encoding/binary"
+	"errors"
+	"fmt"
+
+	"periph.io/x/conn/v3/gpio/gpiostream"
+)
+
+// uint32ToBitLSBF packs a bit offset found on slice `d` (that is actually
+// uint32) back into a densely packed Bits stream.
+func uint32ToBitLSBF(w []byte, d []uint8, bit uint8, skip int) {
+	// Little endian.
+	x := bit / 8
+	d = d[x:]
+	bit -= 8 * x
+	mask := uint8(1) << bit
+	for i := range w {
+		w[i] = ((d[0]&mask)>>bit<<0 |
+			(d[skip*1]&mask)>>bit<<1 |
+			(d[skip*2]&mask)>>bit<<2 |
+			(d[skip*3]&mask)>>bit<<3 |
+			(d[skip*4]&mask)>>bit<<4 |
+			(d[skip*5]&mask)>>bit<<5 |
+			(d[skip*6]&mask)>>bit<<6 |
+			(d[skip*7]&mask)>>bit<<7)
+		d = d[skip*8:]
+	}
+}
+
+func getBit(b byte, index int, msb bool) byte {
+	var shift uint
+	if msb {
+		shift = uint(7 - index)
+	} else {
+		shift = uint(index)
+	}
+	return (b >> shift) & 1
+}
+
+func raster32Bits(s gpiostream.Stream, skip int, clear, set []uint32, mask uint32) error {
+	var msb bool
+	var bits []byte
+	switch b := s.(type) {
+	case *gpiostream.BitStream:
+		msb = !b.LSBF
+		bits = b.Bits
+	default:
+		return fmt.Errorf("unsupported type %T", b)
+	}
+	m := len(clear) / 8
+	if n := len(bits); n < m {
+		m = n
+	}
+	index := 0
+	for i := 0; i < m; i++ {
+		for j := 0; j < 8; j++ {
+			if getBit(bits[i], j, msb) != 0 {
+				for k := 0; k < skip; k++ {
+					set[index] |= mask
+					index++
+				}
+			} else {
+				for k := 0; k < skip; k++ {
+					clear[index] |= mask
+					index++
+				}
+			}
+		}
+	}
+	return nil
+}
+
+// raster32 rasters the stream into a uint32 stream with the specified masks to
+// put in the correctly slice when the bit is set and when it is clear.
+//
+// `s` must be one of the types in this package.
+func raster32(s gpiostream.Stream, skip int, clear, set []uint32, mask uint32) error {
+	if mask == 0 {
+		return errors.New("bcm283x: mask is 0")
+	}
+	if len(clear) == 0 {
+		return errors.New("bcm283x: clear buffer is empty")
+	}
+	if len(set) == 0 {
+		return errors.New("bcm283x: set buffer is empty")
+	}
+	if len(clear) != len(set) {
+		return errors.New("bcm283x: clear and set buffers have different length")
+	}
+	switch x := s.(type) {
+	case *gpiostream.BitStream:
+		// TODO
+		return raster32Bits(x, skip, clear, set, mask)
+	case *gpiostream.EdgeStream:
+		return errors.New("bcm283x: EdgeStream is not supported yet")
+	case *gpiostream.Program:
+		return errors.New("bcm283x: Program is not supported yet")
+	default:
+		return errors.New("bcm283x: unknown stream type")
+	}
+}
+
+// PCM/PWM DMA buf is encoded as little-endian and MSB first.
+func copyStreamToDMABuf(w gpiostream.Stream, dst []uint32) error {
+	switch v := w.(type) {
+	case *gpiostream.BitStream:
+		if v.LSBF {
+			return errors.New("TODO(simokawa): handle BitStream.LSBF")
+		}
+		// This is big-endian and MSB first.
+		i := 0
+		for ; i < len(v.Bits)/4; i++ {
+			dst[i] = binary.BigEndian.Uint32(v.Bits[i*4:])
+		}
+		last := uint32(0)
+		if mod := len(v.Bits) % 4; mod > 0 {
+			for j := 0; j < mod; j++ {
+				last |= (uint32(v.Bits[i*4+j])) << uint32(8*(3-j))
+			}
+			dst[i] = last
+		}
+		return nil
+	case *gpiostream.EdgeStream:
+		return errors.New("TODO(simokawa): handle EdgeStream")
+	default:
+		return errors.New("unsupported Stream type")
+	}
+}