ref: c3101e4da486b2bf2e8b911bcb62dd8ec31c41bf
dir: /opt/misc/appl/bf.b/
# Interpreter for the canonical esoteric language.
# Compiles to bytecode, minimal optimizations, done for fun.
# Pete Elmore (pete at debu dot gs), New Year's Day 2014
# Released into the public domain.
implement Bf;
include "sys.m"; sys: Sys;
include "draw.m";
include "arg.m";
Bf: module {
init: fn(nil: ref Draw->Context, args: list of string);
ARENASZ: con 1024 * 1024;
EXIT, ADD, JZ, JNZ, ADDP, READ, WRITE: con iota;
};
init(nil: ref Draw->Context, args: list of string)
{
sys = load Sys Sys->PATH;
arg := load Arg Arg->PATH;
arg->init(args);
eflag := 0;
outputmode := 0;
source := "";
while ((opt := arg->opt()) != 0) {
case opt {
'e' =>
eflag = 1;
source = arg->arg();
'd' =>
outputmode = 1;
'c' =>
outputmode = 2;
* =>
usage();
}
}
args = arg->argv();
if(!eflag) {
if(len args != 1)
usage();
else
source = readfile(hd args);
}
code := compile(source);
case outputmode {
0 => execute(code, array[ARENASZ] of { * => byte 0 });
1 => sys->print("%s", disassemble(code));
2 => sys->print("%s", bf2limbo(code));
}
}
usage()
{
sys->fprint(sys->fildes(2), "usage: bf [-d|-c] [program.bf|-e inline-program]");
raise "fail:usage";
}
compile(p: string): array of int
{
marks: list of int = nil;
code := array[len p * 2 + 1] of { * => EXIT };
pc := 0;
n: int;
for(i := 0; i < len p; i++) {
case p[i] {
'-' or '+' =>
n = 0;
while(i < len p) {
if(p[i] == '-')
n--;
else if(p[i] == '+')
n++;
else {
i--;
break;
}
i++;
}
if(n) {
code[pc++] = ADD;
code[pc++] = n;
}
'<' or '>' =>
n = 0;
while(i < len p) {
if(p[i] == '<')
n--;
else if(p[i] == '>')
n++;
else {
i--;
break;
}
i++;
}
if(n) {
code[pc++] = ADDP;
code[pc++] = n;
}
',' => code[pc++] = READ;
'.' => code[pc++] = WRITE;
'[' =>
code[pc++] = JZ;
marks = pc++ :: marks;
']' =>
if(marks == nil) {
sys->fprint(sys->fildes(2), "bf: unmatched ']' at character %d.", pc);
raise "fail:errors";
}
c := hd marks;
marks = tl marks;
code[pc++] = JNZ;
code[c] = pc;
code[pc++] = c;
}
}
if(marks != nil) {
sys->fprint(sys->fildes(2), "bf: unmatched '['.");
raise "fail:errors";
}
return code[:pc + 1];
}
execute(code: array of int, arena: array of byte)
{
pc := 0;
p := 0;
buf := array[1] of byte;
stopreading := 0;
for(;;) {
case code[pc] {
ADD =>
arena[p] += byte code[++pc];
ADDP =>
p += code[++pc];
while(p < 0)
p += len arena;
p = p % len arena;
READ =>
arena[p] = byte -1;
if(!stopreading) {
n := sys->read(sys->fildes(0), buf, 1);
if(n < 1)
stopreading = 1;
else
arena[p] = buf[0];
}
WRITE =>
buf[0] = arena[p];
sys->write(sys->fildes(1), buf, 1);
JNZ =>
if(arena[p] != byte 0)
pc = code[pc + 1];
else
pc++;
JZ =>
if(arena[p] == byte 0)
pc = code[pc + 1];
else
pc++;
EXIT => return;
}
pc++;
}
}
disassemble(code: array of int): string
{
s := "";
for(i := 0; i < len code && code[i] != EXIT; i++) {
s += sys->sprint("[0x%08x] 0x%02x ", i, code[i]);
case code[i] {
ADD => s += sys->sprint("add %d", code[++i]);
ADDP => s += sys->sprint("addp %d", code[++i]);
READ => s += "read ";
WRITE => s += "write";
JNZ => s += sys->sprint("jnz 0x%08x", code[++i]);
JZ => s += sys->sprint("jz 0x%08x", code[++i]);
* => s += sys->sprint(">>>>>>BUG %d / 0x%08x", code[i], code[i]);
}
s += "\n";
}
return s;
}
bf2limbo(code: array of int): string
{
indent := 1;
s := "implement BfProg;\n" +
"include \"sys.m\"; sys: Sys;\n" +
"include \"draw.m\";\n" +
"BfProg: module {\n" +
"\tinit: fn(nil: ref Draw->Context, nil: list of string);\n" +
"};\n" +
"init(nil: ref Draw->Context, nil: list of string)\n{\n" +
"\tsys = load Sys Sys->PATH;\n" +
"\tp := 0;\n" +
"\tstopreading := 0;\n" +
"\tn := 0;\n" +
"\tbuf := array[1] of byte;\n" +
"\tarena := array[" + string ARENASZ + "] of { * => byte 0 };\n" +
"\n";
for(i := 0; i < len code && code[i] != EXIT; i++) {
case code[i] {
ADD => s += indents(indent) + "arena[p] += byte " + string code[++i] + ";\n";
ADDP =>
s += indents(indent) + "p += " + string code[++i] + ";\n" +
indents(indent) + "while(p < 0)\n" +
indents(indent + 1) + "p += len arena;\n" +
indents(indent) + "p = p % len arena;\n";
READ =>
s += indents(indent) + "arena[p] = byte -1;\n" +
indents(indent) + "if(!stopreading) {\n" +
indents(indent + 1) + "n = sys->read(sys->fildes(0), buf, 1);\n" +
indents(indent + 1) + "if(n < 1)\n" +
indents(indent + 2) + "stopreading = 1;\n" +
indents(indent + 1) + "else\n" +
indents(indent + 2) + "arena[p] = buf[0];\n" +
indents(indent) + "}\n";
WRITE =>
s += indents(indent) + "buf[0] = arena[p];\n" +
indents(indent) + "sys->write(sys->fildes(1), buf, 1);\n";
JNZ =>
indent--;
s += indents(indent) + "}\n";
i++;
JZ =>
s += indents(indent) + "while(arena[p] != byte 0) {\n";
indent++;
i++;
}
}
return s + "}\n";
}
indents(i: int): string
{
r := "";
while(i > 0) {
r += "\t";
i--;
}
return r;
}
readfile(fname: string): string
{
fd := sys->open(fname, Sys->OREAD);
if(fd == nil)
die(fname);
src := "";
buf := array[Sys->ATOMICIO] of byte;
while((n := sys->read(fd, buf, len buf)) > 0) {
src += string buf[:n];
}
return src;
}
die(s: string)
{
sys->fprint(sys->fildes(2), "bf: %s: %r\n", s);
raise "fail:errors";
}