diskii/basic/applesoft/applesoft.go

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// Copyright © 2016 Zellyn Hunter <zellyn@gmail.com>
// Package applesoft provides routines for working with Applesoft
// files.
package applesoft
import (
"bytes"
"fmt"
)
// TokensByCode is a map from byte value to token text.
var TokensByCode = map[byte]string{
0x80: "END",
0x81: "FOR",
0x82: "NEXT",
0x83: "DATA",
0x84: "INPUT",
0x85: "DEL",
0x86: "DIM",
0x87: "READ",
0x88: "GR",
0x89: "TEXT",
0x8A: "PR #",
0x8B: "IN #",
0x8C: "CALL",
0x8D: "PLOT",
0x8E: "HLIN",
0x8F: "VLIN",
0x90: "HGR2",
0x91: "HGR",
0x92: "HCOLOR=",
0x93: "HPLOT",
0x94: "DRAW",
0x95: "XDRAW",
0x96: "HTAB",
0x97: "HOME",
0x98: "ROT=",
0x99: "SCALE=",
0x9A: "SHLOAD",
0x9B: "TRACE",
0x9C: "NOTRACE",
0x9D: "NORMAL",
0x9E: "INVERSE",
0x9F: "FLASH",
0xA0: "COLOR=",
0xA1: "POP",
0xA2: "VTAB",
0xA3: "HIMEM:",
0xA4: "LOMEM:",
0xA5: "ONERR",
0xA6: "RESUME",
0xA7: "RECALL",
0xA8: "STORE",
0xA9: "SPEED=",
0xAA: "LET",
0xAB: "GOTO",
0xAC: "RUN",
0xAD: "IF",
0xAE: "RESTORE",
0xAF: "&",
0xB0: "GOSUB",
0xB1: "RETURN",
0xB2: "REM",
0xB3: "STOP",
0xB4: "ON",
0xB5: "WAIT",
0xB6: "LOAD",
0xB7: "SAVE",
0xB8: "DEF FN",
0xB9: "POKE",
0xBA: "PRINT",
0xBB: "CONT",
0xBC: "LIST",
0xBD: "CLEAR",
0xBE: "GET",
0xBF: "NEW",
0xC0: "TAB",
0xC1: "TO",
0xC2: "FN",
0xC3: "SPC(",
0xC4: "THEN",
0xC5: "AT",
0xC6: "NOT",
0xC7: "STEP",
0xC8: "+",
0xC9: "-",
0xCA: "*",
0xCB: "/",
0xCC: ";",
0xCD: "AND",
0xCE: "OR",
0xCF: ">",
0xD0: "=",
0xD1: "<",
0xD2: "SGN",
0xD3: "INT",
0xD4: "ABS",
0xD5: "USR",
0xD6: "FRE",
0xD7: "SCRN (",
0xD8: "PDL",
0xD9: "POS",
0xDA: "SQR",
0xDB: "RND",
0xDC: "LOG",
0xDD: "EXP",
0xDE: "COS",
0xDF: "SIN",
0xE0: "TAN",
0xE1: "ATN",
0xE2: "PEEK",
0xE3: "LEN",
0xE4: "STR$",
0xE5: "VAL",
0xE6: "ASC",
0xE7: "CHR$",
0xE8: "LEFT$",
0xE9: "RIGHT$",
0xEA: "MID$",
}
// Listing holds a listing of an entire BASIC program.
type Listing []Line
// Line holds a single BASIC line, with line number and text.
type Line struct {
Num int
Bytes []byte
}
// Decode turns a raw binary file into a basic program. Location
// specifies the program's location in RAM (0x801 for in-ROM Applesoft, 0x3001 for tape-loaded Applesoft).
func Decode(raw []byte, location uint16) (Listing, error) {
// First two bytes of Applesoft files on disk are length. Let's be
// tolerant to getting either format.
if len(raw) >= 2 {
size := int(raw[0]) + (256 * int(raw[1]))
if size == len(raw)-2 || size == len(raw)-3 {
raw = raw[2:]
}
}
bounds := fmt.Sprintf("$%X to $%X", location, int(location)+len(raw))
calcOffset := func(address int) int {
return address - int(location)
}
listing := []Line{}
last := 0 // last line number
next := int(location)
for next != 0 {
ofs := calcOffset(next)
if ofs < -1 || ofs+1 >= len(raw) {
return nil, fmt.Errorf("line %d has next line at $%X, which is outside the input range of %s", last, next, bounds)
}
next = int(raw[ofs]) + 256*int(raw[ofs+1])
ofs += 2
if next == 0 {
break
}
if ofs+1 >= len(raw) {
if len(listing) == 0 {
return nil, fmt.Errorf("ran out of input trying to read the first line number")
}
return nil, fmt.Errorf("ran out of input trying to read line number of line after %d", last)
}
line := Line{Num: int(raw[ofs]) + 256*int(raw[ofs+1])}
ofs += 2
for {
if ofs >= len(raw) {
2021-08-01 03:14:55 +00:00
return nil, fmt.Errorf("ran out of input at location $%X in line %d", ofs+int(location), line.Num)
}
char := raw[ofs]
if char == 0 {
break
}
if char < 0x80 {
line.Bytes = append(line.Bytes, char)
} else {
token := TokensByCode[char]
if token == "" {
return nil, fmt.Errorf("unknown token $%X in line %d", char, line.Num)
}
line.Bytes = append(line.Bytes, char)
}
ofs++
}
listing = append(listing, line)
}
return listing, nil
}
func (l Line) String() string {
var buf bytes.Buffer
fmt.Fprintf(&buf, "%d ", l.Num)
for _, char := range l.Bytes {
if char < 0x80 {
buf.WriteByte(char)
} else {
token := TokensByCode[char]
buf.WriteString(" " + token + " ")
}
}
return buf.String()
}
func (l Listing) String() string {
var buf bytes.Buffer
for _, line := range l {
buf.WriteString(line.String())
buf.WriteByte('\n')
}
return buf.String()
}