Buffered IO.

cmd/bfg/main.go

@@ -49,11 +49,13 @@ func main() {
 		}
 		inputBuf = bufio.NewReader(file)
 	}
+	outputBuf := bufio.NewWriter(os.Stdout)
+	defer outputBuf.Flush()
 
 	program, err := parser.Compile(sourceBuf)
 	if err != nil {
 		fmt.Println("error compiling program: err:", err)
 		os.Exit(1)
 	}
-	parser.Execute(program, inputBuf)
+	parser.Execute(program, inputBuf, outputBuf)
 }

parser/execute.go

@@ -1,16 +1,16 @@
 package parser
 
 import (
-	"fmt"
+	"bufio"
 	"io"
 	"math"
 )
 
 const dataSize int = math.MaxUint16 + 1
 
-func Execute(program []Instruction, reader io.ByteReader) []int16 {
+func Execute(program []Instruction, reader io.ByteReader, writer *bufio.Writer) []int16 {
 	data := make([]int16, dataSize)
-	var dataPtr int = 0
+	var dataPtr, writeCount int = 0, 0
 	for pc := 0; pc < len(program); pc++ {
 		switch program[pc].operator {
 		case opAddDp:
@@ -19,8 +19,17 @@ func Execute(program []Instruction, reader io.ByteReader) []int16 {
 		case opAddVal:
 			data[dataPtr] += int16(program[pc].operand)
 		case opOut:
-			fmt.Printf("%c", data[dataPtr]&0xff)
+			writer.WriteByte(byte(data[dataPtr] & 0xff))
+			writeCount++
+			if data[dataPtr] == 10 || writeCount > 200 {
+				writer.Flush()
+				writeCount = 0
+			}
 		case opIn:
+			if writeCount > 0 {
+				writer.Flush()
+				writeCount = 0
+			}
 			readVal, err := reader.ReadByte()
 			data[dataPtr] = int16(readVal)
 			if err == io.EOF {

parser/execute_test.go

@@ -2,13 +2,13 @@ package parser
 
 import (
 	"bufio"
+	"os"
 	"reflect"
 	"strings"
 	"testing"
 )
 
 func TestExecuteSmall(t *testing.T) {
-	//func Execute(program []Instruction, reader io.ByteReader) []int16
 	program := []Instruction{
 		Instruction{opNoop, 0},
 		Instruction{opAddDp, 5},
@@ -17,7 +17,9 @@ func TestExecuteSmall(t *testing.T) {
 		Instruction{opMove, 2},
 		Instruction{opAddDp, 2},
 	}
-	data := Execute(program, bufio.NewReader(strings.NewReader("no input.")))[:10]
+	outputBuf := bufio.NewWriter(os.Stdout)
+	inputBuf := bufio.NewReader(strings.NewReader("no input."))
+	data := Execute(program, inputBuf, outputBuf)[:10]
 	want := []int16{0, 0, 0, 0, 0, 0, 0, 5, 0, 0}
 
 	if !reflect.DeepEqual(data, want) {