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/common.go

@@ -0,0 +1,110 @@
+// 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 implements the BZip2 compressed data format.
+//
+// Canonical C implementation:
+//	http://bzip.org
+//
+// Unofficial format specification:
+//	https://github.com/dsnet/compress/blob/master/doc/bzip2-format.pdf
+package bzip2
+
+import (
+	"fmt"
+	"hash/crc32"
+
+	"github.com/dsnet/compress/internal"
+	"github.com/dsnet/compress/internal/errors"
+)
+
+// There does not exist a formal specification of the BZip2 format. As such,
+// much of this work is derived by either reverse engineering the original C
+// source code or using secondary sources.
+//
+// Significant amounts of fuzz testing is done to ensure that outputs from
+// this package is properly decoded by the C library. Furthermore, we test that
+// both this package and the C library agree about what inputs are invalid.
+//
+// Compression stack:
+//	Run-length encoding 1     (RLE1)
+//	Burrows-Wheeler transform (BWT)
+//	Move-to-front transform   (MTF)
+//	Run-length encoding 2     (RLE2)
+//	Prefix encoding           (PE)
+//
+// References:
+//	http://bzip.org/
+//	https://en.wikipedia.org/wiki/Bzip2
+//	https://code.google.com/p/jbzip2/
+
+const (
+	BestSpeed          = 1
+	BestCompression    = 9
+	DefaultCompression = 6
+)
+
+const (
+	hdrMagic = 0x425a         // Hex of "BZ"
+	blkMagic = 0x314159265359 // BCD of PI
+	endMagic = 0x177245385090 // BCD of sqrt(PI)
+
+	blockSize = 100000
+)
+
+func errorf(c int, f string, a ...interface{}) error {
+	return errors.Error{Code: c, Pkg: "bzip2", Msg: fmt.Sprintf(f, a...)}
+}
+
+func panicf(c int, f string, a ...interface{}) {
+	errors.Panic(errorf(c, f, a...))
+}
+
+// errWrap converts a lower-level errors.Error to be one from this package.
+// The replaceCode passed in will be used to replace the code for any errors
+// with the errors.Invalid code.
+//
+// For the Reader, set this to errors.Corrupted.
+// For the Writer, set this to errors.Internal.
+func errWrap(err error, replaceCode int) error {
+	if cerr, ok := err.(errors.Error); ok {
+		if errors.IsInvalid(cerr) {
+			cerr.Code = replaceCode
+		}
+		err = errorf(cerr.Code, "%s", cerr.Msg)
+	}
+	return err
+}
+
+var errClosed = errorf(errors.Closed, "")
+
+// crc computes the CRC-32 used by BZip2.
+//
+// The CRC-32 computation in bzip2 treats bytes as having bits in big-endian
+// order. That is, the MSB is read before the LSB. Thus, we can use the
+// standard library version of CRC-32 IEEE with some minor adjustments.
+//
+// The byte array is used as an intermediate buffer to swap the bits of every
+// byte of the input.
+type crc struct {
+	val uint32
+	buf [256]byte
+}
+
+// update computes the CRC-32 of appending buf to c.
+func (c *crc) update(buf []byte) {
+	cval := internal.ReverseUint32(c.val)
+	for len(buf) > 0 {
+		n := len(buf)
+		if n > len(c.buf) {
+			n = len(c.buf)
+		}
+		for i, b := range buf[:n] {
+			c.buf[i] = internal.ReverseLUT[b]
+		}
+		cval = crc32.Update(cval, crc32.IEEETable, c.buf[:n])
+		buf = buf[n:]
+	}
+	c.val = internal.ReverseUint32(cval)
+}