| package com.googlecode.prolog_cafe.builtin; |
| import com.googlecode.prolog_cafe.lang.*; |
| import java.io.*; |
| /** |
| <code>peek_byte/2</code><br> |
| @author Mutsunori Banbara (banbara@kobe-u.ac.jp) |
| @author Naoyuki Tamura (tamura@kobe-u.ac.jp) |
| @version 1.1 |
| @since 1.1 |
| */ |
| public class PRED_peek_byte_2 extends Predicate.P2 { |
| private static final IntegerTerm INT_EOF = new IntegerTerm(-1); |
| |
| public PRED_peek_byte_2(Term a1, Term a2, Operation cont) { |
| arg1 = a1; |
| arg2 = a2; |
| this.cont = cont; |
| } |
| |
| public Operation exec(Prolog engine) { |
| engine.setB0(); |
| Term a1, a2; |
| a1 = arg1; |
| a2 = arg2; |
| Object stream = null; |
| |
| // InByte |
| a2 = a2.dereference(); |
| if (! a2.isVariable()) { |
| if (! a2.isInteger()) |
| throw new IllegalTypeException(this, 2, "in_byte", a2); |
| int n = ((IntegerTerm)a2).intValue(); |
| if (n != -1 && (n < 0 || n > 255)) |
| throw new RepresentationException(this, 2, "in_byte"); |
| } |
| // S_or_a |
| a1 = a1.dereference(); |
| if (a1.isVariable()) { |
| throw new PInstantiationException(this, 1); |
| } else if (a1.isSymbol()) { |
| if (! engine.getStreamManager().containsKey(a1)) |
| throw new ExistenceException(this, 1, "stream", a1, ""); |
| stream = ((JavaObjectTerm) engine.getStreamManager().get(a1)).object(); |
| } else if (a1.isJavaObject()) { |
| stream = ((JavaObjectTerm) a1).object(); |
| } else { |
| throw new IllegalDomainException(this, 1, "stream_or_alias", a1); |
| } |
| if (! (stream instanceof PushbackReader)) |
| throw new PermissionException(this, "input", "stream", a1, ""); |
| // read single byte |
| try { |
| int c = ((PushbackReader)stream).read(); |
| if (c < 0) { // EOF |
| if (! a2.unify(INT_EOF, engine.trail)) |
| return engine.fail(); |
| return cont; |
| } |
| if (c > 255) |
| throw new RepresentationException(this, 0, "byte"); |
| ((PushbackReader)stream).unread(c); |
| if (! a2.unify(new IntegerTerm(c), engine.trail)) |
| return engine.fail(); |
| return cont; |
| } catch (IOException e) { |
| throw new TermException(new JavaObjectTerm(e)); |
| } |
| } |
| } |