Java Type.BYTE属性代码示例

/**
 * Returns the required array type for an array load or store
 * instruction, based on a given implied type and an observed
 * actual array type.
 *
 * <p>The interesting cases here have to do with object arrays,
 * <code>byte[]</code>s, <code>boolean[]</code>s, and
 * known-nulls.</p>
 *
 * <p>In the case of arrays of objects, we want to narrow the type
 * to the actual array present on the stack, as long as what is
 * present is an object type. Similarly, due to a quirk of the
 * original bytecode representation, the instructions for dealing
 * with <code>byte[]</code> and <code>boolean[]</code> are
 * undifferentiated, and we aim here to return whichever one was
 * actually present on the stack.</p>
 *
 * <p>In the case where there is a known-null on the stack where
 * an array is expected, we just fall back to the implied type of
 * the instruction. Due to the quirk described above, this means
 * that source code that uses <code>boolean[]</code> might get
 * translated surprisingly -- but correctly -- into an instruction
 * that specifies a <code>byte[]</code>. It will be correct,
 * because should the code actually execute, it will necessarily
 * throw a <code>NullPointerException</code>, and it won't matter
 * what opcode variant is used to achieve that result.</p>
 *
 * @param impliedType {@code non-null;} type implied by the
 * instruction; is <i>not</i> an array type
 * @param foundArrayType {@code non-null;} type found on the
 * stack; is either an array type or a known-null
 * @return {@code non-null;} the array type that should be
 * required in this context
 */
private static Type requiredArrayTypeFor(Type impliedType,
        Type foundArrayType) {
    if (foundArrayType == Type.KNOWN_NULL) {
        return impliedType.getArrayType();
    }

    if ((impliedType == Type.OBJECT)
            && foundArrayType.isArray()
            && foundArrayType.getComponentType().isReference()) {
        return foundArrayType;
    }

    if ((impliedType == Type.BYTE)
            && (foundArrayType == Type.BOOLEAN_ARRAY)) {
        /*
         * Per above, an instruction with implied byte[] is also
         * allowed to be used on boolean[].
         */
        return Type.BOOLEAN_ARRAY;
    }

    return impliedType.getArrayType();
}
 

/** {@inheritDoc} */
public Type getType() {
    return Type.BYTE;
}
 

/**
 * Returns the required array type for an array load or store
 * instruction, based on a given implied type and an observed
 * actual array type.
 *
 * <p>The interesting cases here have to do with object arrays,
 * <code>byte[]</code>s, <code>boolean[]</code>s, and
 * known-nulls.</p>
 *
 * <p>In the case of arrays of objects, we want to narrow the type
 * to the actual array present on the stack, as long as what is
 * present is an object type. Similarly, due to a quirk of the
 * original bytecode representation, the instructions for dealing
 * with <code>byte[]</code> and <code>boolean[]</code> are
 * undifferentiated, and we aim here to return whichever one was
 * actually present on the stack.</p>
 *
 * <p>In the case where there is a known-null on the stack where
 * an array is expected, our behavior depends on the implied type
 * of the instruction. When the implied type is a reference, we
 * don't attempt to infer anything, as we don't know the dimension
 * of the null constant and thus any explicit inferred type could
 * be wrong. When the implied type is a primitive, we fall back to
 * the implied type of the instruction. Due to the quirk described
 * above, this means that source code that uses
 * <code>boolean[]</code> might get translated surprisingly -- but
 * correctly -- into an instruction that specifies a
 * <code>byte[]</code>. It will be correct, because should the
 * code actually execute, it will necessarily throw a
 * <code>NullPointerException</code>, and it won't matter what
 * opcode variant is used to achieve that result.</p>
 *
 * @param impliedType {@code non-null;} type implied by the
 * instruction; is <i>not</i> an array type
 * @param foundArrayType {@code non-null;} type found on the
 * stack; is either an array type or a known-null
 * @return {@code non-null;} the array type that should be
 * required in this context
 */
private static Type requiredArrayTypeFor(Type impliedType,
        Type foundArrayType) {
    if (foundArrayType == Type.KNOWN_NULL) {
        return impliedType.isReference()
            ? Type.KNOWN_NULL
            : impliedType.getArrayType();
    }

    if ((impliedType == Type.OBJECT)
            && foundArrayType.isArray()
            && foundArrayType.getComponentType().isReference()) {
        return foundArrayType;
    }

    if ((impliedType == Type.BYTE)
            && (foundArrayType == Type.BOOLEAN_ARRAY)) {
        /*
         * Per above, an instruction with implied byte[] is also
         * allowed to be used on boolean[].
         */
        return Type.BOOLEAN_ARRAY;
    }

    return impliedType.getArrayType();
}