001 /**
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements. See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership. The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License. You may obtain a copy of the License at
009 *
010 * http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018 package org.apache.hadoop.fs;
019
020 import java.io.FileNotFoundException;
021 import java.io.IOException;
022 import java.util.EnumSet;
023
024 import org.apache.hadoop.HadoopIllegalArgumentException;
025 import org.apache.hadoop.classification.InterfaceAudience;
026 import org.apache.hadoop.classification.InterfaceStability;
027
028 /****************************************************************
029 * CreateFlag specifies the file create semantic. Users can combine flags like: <br>
030 * <code>
031 * EnumSet.of(CreateFlag.CREATE, CreateFlag.APPEND)
032 * <code>
033 * <p>
034 *
035 * Use the CreateFlag as follows:
036 * <ol>
037 * <li> CREATE - to create a file if it does not exist,
038 * else throw FileAlreadyExists.</li>
039 * <li> APPEND - to append to a file if it exists,
040 * else throw FileNotFoundException.</li>
041 * <li> OVERWRITE - to truncate a file if it exists,
042 * else throw FileNotFoundException.</li>
043 * <li> CREATE|APPEND - to create a file if it does not exist,
044 * else append to an existing file.</li>
045 * <li> CREATE|OVERWRITE - to create a file if it does not exist,
046 * else overwrite an existing file.</li>
047 * <li> SYNC_BLOCK - to force closed blocks to the disk device.
048 * In addition {@link Syncable#hsync()} should be called after each write,
049 * if true synchronous behavior is required.</li>
050 * </ol>
051 *
052 * Following combination is not valid and will result in
053 * {@link HadoopIllegalArgumentException}:
054 * <ol>
055 * <li> APPEND|OVERWRITE</li>
056 * <li> CREATE|APPEND|OVERWRITE</li>
057 * </ol>
058 *****************************************************************/
059 @InterfaceAudience.Public
060 @InterfaceStability.Evolving
061 public enum CreateFlag {
062
063 /**
064 * Create a file. See javadoc for more description
065 * already exists
066 */
067 CREATE((short) 0x01),
068
069 /**
070 * Truncate/overwrite a file. Same as POSIX O_TRUNC. See javadoc for description.
071 */
072 OVERWRITE((short) 0x02),
073
074 /**
075 * Append to a file. See javadoc for more description.
076 */
077 APPEND((short) 0x04),
078
079 /**
080 * Force closed blocks to disk. Similar to POSIX O_SYNC. See javadoc for description.
081 */
082 SYNC_BLOCK((short) 0x08);
083
084 private final short mode;
085
086 private CreateFlag(short mode) {
087 this.mode = mode;
088 }
089
090 short getMode() {
091 return mode;
092 }
093
094 /**
095 * Validate the CreateFlag and throw exception if it is invalid
096 * @param flag set of CreateFlag
097 * @throws HadoopIllegalArgumentException if the CreateFlag is invalid
098 */
099 public static void validate(EnumSet<CreateFlag> flag) {
100 if (flag == null || flag.isEmpty()) {
101 throw new HadoopIllegalArgumentException(flag
102 + " does not specify any options");
103 }
104 final boolean append = flag.contains(APPEND);
105 final boolean overwrite = flag.contains(OVERWRITE);
106
107 // Both append and overwrite is an error
108 if (append && overwrite) {
109 throw new HadoopIllegalArgumentException(
110 flag + "Both append and overwrite options cannot be enabled.");
111 }
112 }
113
114 /**
115 * Validate the CreateFlag for create operation
116 * @param path Object representing the path; usually String or {@link Path}
117 * @param pathExists pass true if the path exists in the file system
118 * @param flag set of CreateFlag
119 * @throws IOException on error
120 * @throws HadoopIllegalArgumentException if the CreateFlag is invalid
121 */
122 public static void validate(Object path, boolean pathExists,
123 EnumSet<CreateFlag> flag) throws IOException {
124 validate(flag);
125 final boolean append = flag.contains(APPEND);
126 final boolean overwrite = flag.contains(OVERWRITE);
127 if (pathExists) {
128 if (!(append || overwrite)) {
129 throw new FileAlreadyExistsException("File already exists: "
130 + path.toString()
131 + ". Append or overwrite option must be specified in " + flag);
132 }
133 } else if (!flag.contains(CREATE)) {
134 throw new FileNotFoundException("Non existing file: " + path.toString()
135 + ". Create option is not specified in " + flag);
136 }
137 }
138 }