Refactor repository layout and convert build system to Mage.

This commit implements a massive refactor of the repository, and
moves the build system over to use Mage (magefile.org) which should
allow seamless building across multiple platforms.

vendor/github.com/dsnet/compress/bzip2/rle1.go

@@ -0,0 +1,101 @@
+// Copyright 2015, Joe Tsai. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE.md file.
+
+package bzip2
+
+import "github.com/dsnet/compress/internal/errors"
+
+// rleDone is a special "error" to indicate that the RLE stage is done.
+var rleDone = errorf(errors.Unknown, "RLE1 stage is completed")
+
+// runLengthEncoding implements the first RLE stage of bzip2. Every sequence
+// of 4..255 duplicated bytes is replaced by only the first 4 bytes, and a
+// single byte representing the repeat length. Similar to the C bzip2
+// implementation, the encoder will always terminate repeat sequences with a
+// count (even if it is the end of the buffer), and it will also never produce
+// run lengths of 256..259. The decoder can handle the latter case.
+//
+// For example, if the input was:
+//	input:  "AAAAAAABBBBCCCD"
+//
+// Then the output will be:
+//	output: "AAAA\x03BBBB\x00CCCD"
+type runLengthEncoding struct {
+	buf     []byte
+	idx     int
+	lastVal byte
+	lastCnt int
+}
+
+func (rle *runLengthEncoding) Init(buf []byte) {
+	*rle = runLengthEncoding{buf: buf}
+}
+
+func (rle *runLengthEncoding) Write(buf []byte) (int, error) {
+	for i, b := range buf {
+		if rle.lastVal != b {
+			rle.lastCnt = 0
+		}
+		rle.lastCnt++
+		switch {
+		case rle.lastCnt < 4:
+			if rle.idx >= len(rle.buf) {
+				return i, rleDone
+			}
+			rle.buf[rle.idx] = b
+			rle.idx++
+		case rle.lastCnt == 4:
+			if rle.idx+1 >= len(rle.buf) {
+				return i, rleDone
+			}
+			rle.buf[rle.idx] = b
+			rle.idx++
+			rle.buf[rle.idx] = 0
+			rle.idx++
+		case rle.lastCnt < 256:
+			rle.buf[rle.idx-1]++
+		default:
+			if rle.idx >= len(rle.buf) {
+				return i, rleDone
+			}
+			rle.lastCnt = 1
+			rle.buf[rle.idx] = b
+			rle.idx++
+		}
+		rle.lastVal = b
+	}
+	return len(buf), nil
+}
+
+func (rle *runLengthEncoding) Read(buf []byte) (int, error) {
+	for i := range buf {
+		switch {
+		case rle.lastCnt == -4:
+			if rle.idx >= len(rle.buf) {
+				return i, errorf(errors.Corrupted, "missing terminating run-length repeater")
+			}
+			rle.lastCnt = int(rle.buf[rle.idx])
+			rle.idx++
+			if rle.lastCnt > 0 {
+				break // Break the switch
+			}
+			fallthrough // Count was zero, continue the work
+		case rle.lastCnt <= 0:
+			if rle.idx >= len(rle.buf) {
+				return i, rleDone
+			}
+			b := rle.buf[rle.idx]
+			rle.idx++
+			if b != rle.lastVal {
+				rle.lastCnt = 0
+				rle.lastVal = b
+			}
+		}
+		buf[i] = rle.lastVal
+		rle.lastCnt--
+	}
+	return len(buf), nil
+}
+
+func (rle *runLengthEncoding) Bytes() []byte { return rle.buf[:rle.idx] }