Imported ImapUtility.java from AOSP Email

Modified it to fit our needs.

src/com/fsck/k9/mail/store/imap/ImapUtility.java

@@ -0,0 +1,113 @@
+/*
+ * Copyright (C) 2012 The K-9 Dog Walkers
+ * Copyright (C) 2011 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.fsck.k9.mail.store.imap;
+
+import android.util.Log;
+
+import com.fsck.k9.K9;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * Utility methods for use with IMAP.
+ */
+public class ImapUtility {
+    /**
+     * Gets all of the values in a sequence set per RFC 3501.
+     *
+     * <p>
+     * Any ranges are expanded into a list of individual numbers.
+     * </p>
+     *
+     * <pre>
+     * sequence-number = nz-number / "*"
+     * sequence-range  = sequence-number ":" sequence-number
+     * sequence-set    = (sequence-number / sequence-range) *("," sequence-set)
+     * </pre>
+     *
+     * @param set
+     *         The sequence set string as received by the server.
+     *
+     * @return The list of IDs as strings in this sequence set. If the set is invalid, an empty
+     *         list is returned.
+     */
+    public static List<String> getImapSequenceValues(String set) {
+        ArrayList<String> list = new ArrayList<String>();
+        if (set != null) {
+            String[] setItems = set.split(",");
+            for (String item : setItems) {
+                if (item.indexOf(':') == -1) {
+                    // simple item
+                    try {
+                        Integer.parseInt(item); // Don't need the value; just ensure it's valid
+                        list.add(item);
+                    } catch (NumberFormatException e) {
+                        Log.d(K9.LOG_TAG, "Invalid UID value", e);
+                    }
+                } else {
+                    // range
+                    list.addAll(getImapRangeValues(item));
+                }
+            }
+        }
+
+        return list;
+    }
+
+    /**
+     * Expand the given number range into a list of individual numbers.
+     *
+     * <pre>
+     * sequence-number = nz-number / "*"
+     * sequence-range  = sequence-number ":" sequence-number
+     * sequence-set    = (sequence-number / sequence-range) *("," sequence-set)
+     * </pre>
+     *
+     * @param range
+     *         The range string as received by the server.
+     *
+     * @return The list of IDs as strings in this range. If the range is not valid, an empty list
+     *         is returned.
+     */
+    public static List<String> getImapRangeValues(String range) {
+        ArrayList<String> list = new ArrayList<String>();
+        try {
+            if (range != null) {
+                int colonPos = range.indexOf(':');
+                if (colonPos > 0) {
+                    int first  = Integer.parseInt(range.substring(0, colonPos));
+                    int second = Integer.parseInt(range.substring(colonPos + 1));
+                    if (first < second) {
+                        for (int i = first; i <= second; i++) {
+                            list.add(Integer.toString(i));
+                        }
+                    } else {
+                        for (int i = first; i >= second; i--) {
+                            list.add(Integer.toString(i));
+                        }
+                    }
+                }
+            }
+        } catch (NumberFormatException e) {
+            Log.d(K9.LOG_TAG, "Invalid range value", e);
+        }
+
+        return list;
+    }
+}