feat: add ROM conversion command

cmd/convert.go

@@ -0,0 +1,51 @@
+package cmd
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"path"
+	"strings"
+
+	"github.com/mroach/n64-go/rom"
+	"github.com/spf13/cobra"
+)
+
+func init() {
+	var overwrite bool
+	var convertCmd = &cobra.Command{
+		Use:   "convert",
+		Short: "Converts a ROM to native Big-Endian Z64 format",
+		Args:  cobra.MinimumNArgs(1),
+		RunE: func(cmd *cobra.Command, args []string) error {
+			inpath := args[0]
+			dirname, filename := path.Split(inpath)
+			baseFilename := basename(filename)
+			outFilename := baseFilename + ".z64"
+			outpath := path.Join(dirname, outFilename)
+
+			if !overwrite {
+				if _, err := os.Stat(outpath); err == nil {
+					return errors.New(outpath + " already exists")
+				}
+			}
+
+			if err := rom.ConvertRomFormat(inpath, outpath); err != nil {
+				return err
+			}
+
+			fmt.Println(inpath, "=>", outpath)
+			return nil
+		},
+	}
+
+	convertCmd.Flags().BoolVarP(&overwrite, "force", "f", false, "Overwrite destination file if it exists")
+	rootCmd.AddCommand(convertCmd)
+}
+
+func basename(filename string) string {
+	if pos := strings.LastIndexByte(filename, '.'); pos != -1 {
+		return filename[:pos]
+	}
+	return filename
+}

rom/convert.go

@@ -0,0 +1,77 @@
+package rom
+
+import (
+	"errors"
+	"io"
+	"os"
+)
+
+func ConvertRomFormat(inpath string, outpath string) error {
+	const bufferSize = 2048
+
+	info, err := FromPath(inpath)
+	if err != nil {
+		return err
+	}
+
+	if info.File.Format == "z64" {
+		return errors.New("File is already in the native Z64 format")
+	}
+
+	source, err := os.Open(inpath)
+	if err != nil {
+		return err
+	}
+
+	dest, err := os.Create(outpath)
+	if err != nil {
+		return err
+	}
+
+	for {
+		buf := make([]byte, bufferSize)
+		n, err := source.Read(buf)
+		if err != nil && err != io.EOF {
+			return err
+		}
+		if n == 0 {
+			break
+		}
+
+		buf = maybeReverseBytes(buf, info.File.Format)
+		if _, err := dest.Write(buf[:n]); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func maybeReverseBytes(bytes []byte, romFormat string) []byte {
+	if romFormat == "v64" {
+		return reverseBytes(bytes, 2)
+	}
+
+	if romFormat == "n64" {
+		return reverseBytes(bytes, 4)
+	}
+
+	return bytes
+}
+
+func reverseBytes(bytes []byte, size int) (reversed []byte) {
+	for _, chunk := range chunk(bytes, size) {
+		for i := len(chunk) - 1; i >= 0; i = i - 1 {
+			reversed = append(reversed, chunk[i])
+		}
+	}
+
+	return reversed
+}
+
+func chunk(bytes []byte, chunkSize int) (chunks [][]byte) {
+	for chunkSize < len(bytes) {
+		bytes, chunks = bytes[chunkSize:], append(chunks, bytes[0:chunkSize:chunkSize])
+	}
+	return append(chunks, bytes)
+}

rom/rom.go

@@ -224,35 +224,6 @@ func detectRomFormat(signature []byte) (string, error) {
 	return "", errors.New("Unknown ROM format. Invalid file?")
 }
 
-func maybeReverseBytes(bytes []byte, romFormat string) []byte {
-	if romFormat == "v64" {
-		return reverseBytes(bytes, 2)
-	}
-
-	if romFormat == "n64" {
-		return reverseBytes(bytes, 4)
-	}
-
-	return bytes
-}
-
-func reverseBytes(bytes []byte, size int) (reversed []byte) {
-	for _, chunk := range chunk(bytes, size) {
-		for i := len(chunk) - 1; i >= 0; i = i - 1 {
-			reversed = append(reversed, chunk[i])
-		}
-	}
-
-	return reversed
-}
-
-func chunk(bytes []byte, chunkSize int) (chunks [][]byte) {
-	for chunkSize < len(bytes) {
-		bytes, chunks = bytes[chunkSize:], append(chunks, bytes[0:chunkSize:chunkSize])
-	}
-	return append(chunks, bytes)
-}
-
 func bytesToString(bytes []byte) string {
 	chars := []rune{}