1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.apache.commons.geometry.io.euclidean.threed.stl;
18
19 import java.io.BufferedReader;
20 import java.io.InputStream;
21 import java.io.InputStreamReader;
22 import java.io.PushbackInputStream;
23 import java.nio.charset.Charset;
24 import java.text.MessageFormat;
25 import java.util.Arrays;
26
27 import org.apache.commons.geometry.io.core.internal.GeometryIOUtils;
28 import org.apache.commons.geometry.io.euclidean.threed.FacetDefinitionReader;
29
30 /** Utility class with factory methods for constructing {@link FacetDefinitionReader}
31 * instances for STL content.
32 */
33 public final class StlFacetDefinitionReaders {
34
35 /** Utility class; no instantiation. */
36 private StlFacetDefinitionReaders() { }
37
38 /** Construct a {@link FacetDefinitionReader} for reading STL content from the
39 * given input. The format of the input is checked to determine if it is a binary
40 * or text file and an appropriate reader is returned.
41 * @param in input to read from
42 * @param charset charset to use when checking the input for text content;
43 * if null, the input is assumed to use the UTF-8 charset
44 * @return facet definition reader
45 * @throws IllegalStateException if a parsing error occurs
46 * @throws java.io.UncheckedIOException if an I/O error occurs
47 */
48 public static FacetDefinitionReader create(final InputStream in, final Charset charset) {
49 final Charset inputCharset = charset != null ?
50 charset :
51 StlConstants.DEFAULT_CHARSET;
52
53 final byte[] testBytes = StlConstants.SOLID_START_KEYWORD.getBytes(inputCharset);
54 final byte[] actualBytes = new byte[testBytes.length];
55
56 final int read = GeometryIOUtils.applyAsIntUnchecked(in::read, actualBytes);
57 if (read < actualBytes.length) {
58 throw GeometryIOUtils.parseError(MessageFormat.format(
59 "Cannot determine STL format: attempted to read {0} bytes but found only {1} available",
60 actualBytes.length, read));
61 }
62
63 // "unread" the test bytes so that the created readers can start from the
64 // beginning of the content
65 final PushbackInputStream pushbackInput = new PushbackInputStream(in, actualBytes.length);
66 GeometryIOUtils.acceptUnchecked(pushbackInput::unread, actualBytes);
67
68 if (Arrays.equals(testBytes, actualBytes)) {
69 // this is a text file
70 return new TextStlFacetDefinitionReader(
71 new BufferedReader(new InputStreamReader(pushbackInput, inputCharset)));
72 } else {
73 // this is a binary file
74 return new BinaryStlFacetDefinitionReader(pushbackInput);
75 }
76 }
77 }