rewrote field data structure for simplicity

pkg/field/field.go

@@ -1,7 +1,6 @@
 package field
 
 import (
-	"bytes"
 	"io"
 )
 
@@ -16,15 +15,17 @@ import (
 //                  y|2,147,483,647
 
 type Field struct {
-	firstLineIndex int
-	length         int
-	lines          []Line
+	x     int
+	y     int
+	lx    int
+	ly    int
+	lines []Line
 }
 
 type Line struct {
-	firstColumnIndex int
-	length           int
-	columns          []byte
+	x       int
+	l       int
+	columns []int
 }
 
 func LoadFile(fd io.Reader) (*Field, error) {
@@ -35,11 +36,14 @@ func LoadFile(fd io.Reader) (*Field, error) {
 		data := make([]byte, 4096)
 		if n, errRead := fd.Read(data); errRead != nil {
 			if errRead == io.EOF {
-				if f.length == 0 && l.length == 0 {
+				if f.ly == 0 && l.l == 0 {
 					return nil, newDecodeError("No instruction on the first line of the file produces an unusable program in Befunge98")
 				}
-				if l.length > 0 {
-					f.length++
+				if l.l > 0 {
+					f.ly++
+					if f.lx < l.l {
+						f.lx = l.l
+					}
 					f.lines = append(f.lines, *l)
 				}
 				break
@@ -49,10 +53,13 @@ func LoadFile(fd io.Reader) (*Field, error) {
 		} else {
 			for i := 0; i < n; i++ {
 				if data[i] == '\n' || data[i] == '\r' {
-					if f.length == 0 && l.length == 0 {
+					if f.ly == 0 && l.l == 0 {
 						return nil, newDecodeError("No instruction on the first line of the file produces an unusable program in Befunge98")
 					}
-					f.length++
+					f.ly++
+					if f.lx < l.l {
+						f.lx = l.l
+					}
 					f.lines = append(f.lines, *l)
 					l = new(Line)
 					trailingSpaces = 0
@@ -60,17 +67,18 @@ func LoadFile(fd io.Reader) (*Field, error) {
 						i++
 					}
 				} else {
-					if l.length == 0 && data[i] == ' ' {
-						l.firstColumnIndex++ // trim leading spaces
+					if l.l == 0 && data[i] == ' ' {
+						l.x++ // trim leading spaces
 					} else {
 						if data[i] == ' ' {
 							trailingSpaces++
 						} else {
-							l.columns = append(l.columns, bytes.Repeat([]byte{' '}, trailingSpaces)...)
-							l.length += trailingSpaces
+							for j := 0; j < trailingSpaces; j++ {
+								l.columns = append(l.columns, ' ')
+							}
+							l.l += trailingSpaces + 1
 							trailingSpaces = 0
-							l.length++
-							l.columns = append(l.columns, data[i])
+							l.columns = append(l.columns, int(data[i]))
 						}
 					}
 				}