Bring MIME4J current to match AOSP upstream as of 9e5757b5316f88d252b5d80fab1e3964ce19bbdf - Thanks to Ludovic LANGE / ludovic.lange.android

src/org/apache/james/mime4j/codec/EncoderUtil.java

@@ -0,0 +1,630 @@
+/****************************************************************
+ * Licensed to the Apache Software Foundation (ASF) under one   *
+ * or more contributor license agreements.  See the NOTICE file *
+ * distributed with this work for additional information        *
+ * regarding copyright ownership.  The ASF licenses this file   *
+ * to you 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 org.apache.james.mime4j.codec;
+
+import java.nio.ByteBuffer;
+import java.nio.charset.Charset;
+import java.util.BitSet;
+import java.util.Locale;
+
+import org.apache.james.mime4j.util.CharsetUtil;
+
+/**
+ * ANDROID:  THIS CLASS IS COPIED FROM A NEWER VERSION OF MIME4J
+ */
+
+/**
+ * Static methods for encoding header field values. This includes encoded-words
+ * as defined in <a href='http://www.faqs.org/rfcs/rfc2047.html'>RFC 2047</a>
+ * or display-names of an e-mail address, for example.
+ * 
+ */
+public class EncoderUtil {
+
+    // This array is a lookup table that translates 6-bit positive integer index
+    // values into their "Base64 Alphabet" equivalents as specified in Table 1
+    // of RFC 2045.
+    // ANDROID:  THIS TABLE IS COPIED FROM BASE64OUTPUTSTREAM
+    static final byte[] BASE64_TABLE = { 'A', 'B', 'C', 'D', 'E', 'F',
+            'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S',
+            'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f',
+            'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's',
+            't', 'u', 'v', 'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5',
+            '6', '7', '8', '9', '+', '/' };
+
+    // Byte used to pad output.
+    private static final byte BASE64_PAD = '=';
+
+    private static final BitSet Q_REGULAR_CHARS = initChars("=_?");
+
+    private static final BitSet Q_RESTRICTED_CHARS = initChars("=_?\"#$%&'(),.:;<>@[\\]^`{|}~");
+
+    private static final int MAX_USED_CHARACTERS = 50;
+
+    private static final String ENC_WORD_PREFIX = "=?";
+    private static final String ENC_WORD_SUFFIX = "?=";
+
+    private static final int ENCODED_WORD_MAX_LENGTH = 75; // RFC 2047
+
+    private static final BitSet TOKEN_CHARS = initChars("()<>@,;:\\\"/[]?=");
+
+    private static final BitSet ATEXT_CHARS = initChars("()<>@.,;:\\\"[]");
+
+    private static BitSet initChars(String specials) {
+        BitSet bs = new BitSet(128);
+        for (char ch = 33; ch < 127; ch++) {
+            if (specials.indexOf(ch) == -1) {
+                bs.set(ch);
+            }
+        }
+        return bs;
+    }
+
+    /**
+     * Selects one of the two encodings specified in RFC 2047.
+     */
+    public enum Encoding {
+        /** The B encoding (identical to base64 defined in RFC 2045). */
+        B,
+        /** The Q encoding (similar to quoted-printable defined in RFC 2045). */
+        Q
+    }
+
+    /**
+     * Indicates the intended usage of an encoded word.
+     */
+    public enum Usage {
+        /**
+         * Encoded word is used to replace a 'text' token in any Subject or
+         * Comments header field.
+         */
+        TEXT_TOKEN,
+        /**
+         * Encoded word is used to replace a 'word' entity within a 'phrase',
+         * for example, one that precedes an address in a From, To, or Cc
+         * header.
+         */
+        WORD_ENTITY
+    }
+
+    private EncoderUtil() {
+    }
+
+    /**
+     * Encodes the display-name portion of an address. See <a
+     * href='http://www.faqs.org/rfcs/rfc5322.html'>RFC 5322</a> section 3.4
+     * and <a href='http://www.faqs.org/rfcs/rfc2047.html'>RFC 2047</a> section
+     * 5.3. The specified string should not be folded.
+     * 
+     * @param displayName
+     *            display-name to encode.
+     * @return encoded display-name.
+     */
+    public static String encodeAddressDisplayName(String displayName) {
+        // display-name = phrase
+        // phrase = 1*( encoded-word / word )
+        // word = atom / quoted-string
+        // atom = [CFWS] 1*atext [CFWS]
+        // CFWS = comment or folding white space
+
+        if (isAtomPhrase(displayName)) {
+            return displayName;
+        } else if (hasToBeEncoded(displayName, 0)) {
+            return encodeEncodedWord(displayName, Usage.WORD_ENTITY);
+        } else {
+            return quote(displayName);
+        }
+    }
+
+    /**
+     * Encodes the local part of an address specification as described in RFC
+     * 5322 section 3.4.1. Leading and trailing CFWS should have been removed
+     * before calling this method. The specified string should not contain any
+     * illegal (control or non-ASCII) characters.
+     * 
+     * @param localPart
+     *            the local part to encode
+     * @return the encoded local part.
+     */
+    public static String encodeAddressLocalPart(String localPart) {
+        // local-part = dot-atom / quoted-string
+        // dot-atom = [CFWS] dot-atom-text [CFWS]
+        // CFWS = comment or folding white space
+
+        if (isDotAtomText(localPart)) {
+            return localPart;
+        } else {
+            return quote(localPart);
+        }
+    }
+
+    /**
+     * Encodes the specified strings into a header parameter as described in RFC
+     * 2045 section 5.1 and RFC 2183 section 2. The specified strings should not
+     * contain any illegal (control or non-ASCII) characters.
+     * 
+     * @param name
+     *            parameter name.
+     * @param value
+     *            parameter value.
+     * @return encoded result.
+     */
+    public static String encodeHeaderParameter(String name, String value) {
+        name = name.toLowerCase(Locale.US);
+
+        // value := token / quoted-string
+        if (isToken(value)) {
+            return name + "=" + value;
+        } else {
+            return name + "=" + quote(value);
+        }
+    }
+
+    /**
+     * Shortcut method that encodes the specified text into an encoded-word if
+     * the text has to be encoded.
+     * 
+     * @param text
+     *            text to encode.
+     * @param usage
+     *            whether the encoded-word is to be used to replace a text token
+     *            or a word entity (see RFC 822).
+     * @param usedCharacters
+     *            number of characters already used up (<code>0 <= usedCharacters <= 50</code>).
+     * @return the specified text if encoding is not necessary or an encoded
+     *         word or a sequence of encoded words otherwise.
+     */
+    public static String encodeIfNecessary(String text, Usage usage,
+            int usedCharacters) {
+        if (hasToBeEncoded(text, usedCharacters))
+            return encodeEncodedWord(text, usage, usedCharacters);
+        else
+            return text;
+    }
+
+    /**
+     * Determines if the specified string has to encoded into an encoded-word.
+     * Returns <code>true</code> if the text contains characters that don't
+     * fall into the printable ASCII character set or if the text contains a
+     * 'word' (sequence of non-whitespace characters) longer than 77 characters
+     * (including characters already used up in the line).
+     * 
+     * @param text
+     *            text to analyze.
+     * @param usedCharacters
+     *            number of characters already used up (<code>0 <= usedCharacters <= 50</code>).
+     * @return <code>true</code> if the specified text has to be encoded into
+     *         an encoded-word, <code>false</code> otherwise.
+     */
+    public static boolean hasToBeEncoded(String text, int usedCharacters) {
+        if (text == null)
+            throw new IllegalArgumentException();
+        if (usedCharacters < 0 || usedCharacters > MAX_USED_CHARACTERS)
+            throw new IllegalArgumentException();
+
+        int nonWhiteSpaceCount = usedCharacters;
+
+        for (int idx = 0; idx < text.length(); idx++) {
+            char ch = text.charAt(idx);
+            if (ch == '\t' || ch == ' ') {
+                nonWhiteSpaceCount = 0;
+            } else {
+                nonWhiteSpaceCount++;
+                if (nonWhiteSpaceCount > 77) {
+                    // Line cannot be folded into multiple lines with no more
+                    // than 78 characters each. Encoding as encoded-words makes
+                    // that possible. One character has to be reserved for
+                    // folding white space; that leaves 77 characters.
+                    return true;
+                }
+
+                if (ch < 32 || ch >= 127) {
+                    // non-printable ascii character has to be encoded
+                    return true;
+                }
+            }
+        }
+
+        return false;
+    }
+
+    /**
+     * Encodes the specified text into an encoded word or a sequence of encoded
+     * words separated by space. The text is separated into a sequence of
+     * encoded words if it does not fit in a single one.
+     * <p>
+     * The charset to encode the specified text into a byte array and the
+     * encoding to use for the encoded-word are detected automatically.
+     * <p>
+     * This method assumes that zero characters have already been used up in the
+     * current line.
+     * 
+     * @param text
+     *            text to encode.
+     * @param usage
+     *            whether the encoded-word is to be used to replace a text token
+     *            or a word entity (see RFC 822).
+     * @return the encoded word (or sequence of encoded words if the given text
+     *         does not fit in a single encoded word).
+     * @see #hasToBeEncoded(String, int)
+     */
+    public static String encodeEncodedWord(String text, Usage usage) {
+        return encodeEncodedWord(text, usage, 0, null, null);
+    }
+
+    /**
+     * Encodes the specified text into an encoded word or a sequence of encoded
+     * words separated by space. The text is separated into a sequence of
+     * encoded words if it does not fit in a single one.
+     * <p>
+     * The charset to encode the specified text into a byte array and the
+     * encoding to use for the encoded-word are detected automatically.
+     * 
+     * @param text
+     *            text to encode.
+     * @param usage
+     *            whether the encoded-word is to be used to replace a text token
+     *            or a word entity (see RFC 822).
+     * @param usedCharacters
+     *            number of characters already used up (<code>0 <= usedCharacters <= 50</code>).
+     * @return the encoded word (or sequence of encoded words if the given text
+     *         does not fit in a single encoded word).
+     * @see #hasToBeEncoded(String, int)
+     */
+    public static String encodeEncodedWord(String text, Usage usage,
+            int usedCharacters) {
+        return encodeEncodedWord(text, usage, usedCharacters, null, null);
+    }
+
+    /**
+     * Encodes the specified text into an encoded word or a sequence of encoded
+     * words separated by space. The text is separated into a sequence of
+     * encoded words if it does not fit in a single one.
+     * 
+     * @param text
+     *            text to encode.
+     * @param usage
+     *            whether the encoded-word is to be used to replace a text token
+     *            or a word entity (see RFC 822).
+     * @param usedCharacters
+     *            number of characters already used up (<code>0 <= usedCharacters <= 50</code>).
+     * @param charset
+     *            the Java charset that should be used to encode the specified
+     *            string into a byte array. A suitable charset is detected
+     *            automatically if this parameter is <code>null</code>.
+     * @param encoding
+     *            the encoding to use for the encoded-word (either B or Q). A
+     *            suitable encoding is automatically chosen if this parameter is
+     *            <code>null</code>.
+     * @return the encoded word (or sequence of encoded words if the given text
+     *         does not fit in a single encoded word).
+     * @see #hasToBeEncoded(String, int)
+     */
+    public static String encodeEncodedWord(String text, Usage usage,
+            int usedCharacters, Charset charset, Encoding encoding) {
+        if (text == null)
+            throw new IllegalArgumentException();
+        if (usedCharacters < 0 || usedCharacters > MAX_USED_CHARACTERS)
+            throw new IllegalArgumentException();
+
+        if (charset == null)
+            charset = determineCharset(text);
+
+        String mimeCharset = CharsetUtil.toMimeCharset(charset.name());
+        if (mimeCharset == null) {
+            // cannot happen if charset was originally null
+            throw new IllegalArgumentException("Unsupported charset");
+        }
+
+        byte[] bytes = encode(text, charset);
+
+        if (encoding == null)
+            encoding = determineEncoding(bytes, usage);
+
+        if (encoding == Encoding.B) {
+            String prefix = ENC_WORD_PREFIX + mimeCharset + "?B?";
+            return encodeB(prefix, text, usedCharacters, charset, bytes);
+        } else {
+            String prefix = ENC_WORD_PREFIX + mimeCharset + "?Q?";
+            return encodeQ(prefix, text, usage, usedCharacters, charset, bytes);
+        }
+    }
+
+    /**
+     * Encodes the specified byte array using the B encoding defined in RFC
+     * 2047.
+     * 
+     * @param bytes
+     *            byte array to encode.
+     * @return encoded string.
+     */
+    public static String encodeB(byte[] bytes) {
+        StringBuilder sb = new StringBuilder();
+
+        int idx = 0;
+        final int end = bytes.length;
+        for (; idx < end - 2; idx += 3) {
+            int data = (bytes[idx] & 0xff) << 16 | (bytes[idx + 1] & 0xff) << 8
+                    | bytes[idx + 2] & 0xff;
+            sb.append((char) BASE64_TABLE[data >> 18 & 0x3f]);
+            sb.append((char) BASE64_TABLE[data >> 12 & 0x3f]);
+            sb.append((char) BASE64_TABLE[data >> 6 & 0x3f]);
+            sb.append((char) BASE64_TABLE[data & 0x3f]);
+        }
+
+        if (idx == end - 2) {
+            int data = (bytes[idx] & 0xff) << 16 | (bytes[idx + 1] & 0xff) << 8;
+            sb.append((char) BASE64_TABLE[data >> 18 & 0x3f]);
+            sb.append((char) BASE64_TABLE[data >> 12 & 0x3f]);
+            sb.append((char) BASE64_TABLE[data >> 6 & 0x3f]);
+            sb.append((char) BASE64_PAD);
+
+        } else if (idx == end - 1) {
+            int data = (bytes[idx] & 0xff) << 16;
+            sb.append((char) BASE64_TABLE[data >> 18 & 0x3f]);
+            sb.append((char) BASE64_TABLE[data >> 12 & 0x3f]);
+            sb.append((char) BASE64_PAD);
+            sb.append((char) BASE64_PAD);
+        }
+
+        return sb.toString();
+    }
+
+    /**
+     * Encodes the specified byte array using the Q encoding defined in RFC
+     * 2047.
+     * 
+     * @param bytes
+     *            byte array to encode.
+     * @param usage
+     *            whether the encoded-word is to be used to replace a text token
+     *            or a word entity (see RFC 822).
+     * @return encoded string.
+     */
+    public static String encodeQ(byte[] bytes, Usage usage) {
+        BitSet qChars = usage == Usage.TEXT_TOKEN ? Q_REGULAR_CHARS
+                : Q_RESTRICTED_CHARS;
+
+        StringBuilder sb = new StringBuilder();
+
+        final int end = bytes.length;
+        for (int idx = 0; idx < end; idx++) {
+            int v = bytes[idx] & 0xff;
+            if (v == 32) {
+                sb.append('_');
+            } else if (!qChars.get(v)) {
+                sb.append('=');
+                sb.append(hexDigit(v >>> 4));
+                sb.append(hexDigit(v & 0xf));
+            } else {
+                sb.append((char) v);
+            }
+        }
+
+        return sb.toString();
+    }
+
+    /**
+     * Tests whether the specified string is a token as defined in RFC 2045
+     * section 5.1.
+     * 
+     * @param str
+     *            string to test.
+     * @return <code>true</code> if the specified string is a RFC 2045 token,
+     *         <code>false</code> otherwise.
+     */
+    public static boolean isToken(String str) {
+        // token := 1*<any (US-ASCII) CHAR except SPACE, CTLs, or tspecials>
+        // tspecials := "(" / ")" / "<" / ">" / "@" / "," / ";" / ":" / "\" /
+        // <"> / "/" / "[" / "]" / "?" / "="
+        // CTL := 0.- 31., 127.
+
+        final int length = str.length();
+        if (length == 0)
+            return false;
+
+        for (int idx = 0; idx < length; idx++) {
+            char ch = str.charAt(idx);
+            if (!TOKEN_CHARS.get(ch))
+                return false;
+        }
+
+        return true;
+    }
+
+    private static boolean isAtomPhrase(String str) {
+        // atom = [CFWS] 1*atext [CFWS]
+
+        boolean containsAText = false;
+
+        final int length = str.length();
+        for (int idx = 0; idx < length; idx++) {
+            char ch = str.charAt(idx);
+            if (ATEXT_CHARS.get(ch)) {
+                containsAText = true;
+            } else if (!CharsetUtil.isWhitespace(ch)) {
+                return false;
+            }
+        }
+
+        return containsAText;
+    }
+
+    // RFC 5322 section 3.2.3
+    private static boolean isDotAtomText(String str) {
+        // dot-atom-text = 1*atext *("." 1*atext)
+        // atext = ALPHA / DIGIT / "!" / "#" / "$" / "%" / "&" / "'" / "*" /
+        // "+" / "-" / "/" / "=" / "?" / "^" / "_" / "`" / "{" / "|" / "}" / "~"
+
+        char prev = '.';
+
+        final int length = str.length();
+        if (length == 0)
+            return false;
+
+        for (int idx = 0; idx < length; idx++) {
+            char ch = str.charAt(idx);
+
+            if (ch == '.') {
+                if (prev == '.' || idx == length - 1)
+                    return false;
+            } else {
+                if (!ATEXT_CHARS.get(ch))
+                    return false;
+            }
+
+            prev = ch;
+        }
+
+        return true;
+    }
+
+    // RFC 5322 section 3.2.4
+    private static String quote(String str) {
+        // quoted-string = [CFWS] DQUOTE *([FWS] qcontent) [FWS] DQUOTE [CFWS]
+        // qcontent = qtext / quoted-pair
+        // qtext = %d33 / %d35-91 / %d93-126
+        // quoted-pair = ("\" (VCHAR / WSP))
+        // VCHAR = %x21-7E
+        // DQUOTE = %x22
+
+        String escaped = str.replaceAll("[\\\\\"]", "\\\\$0");
+        return "\"" + escaped + "\"";
+    }
+
+    private static String encodeB(String prefix, String text,
+            int usedCharacters, Charset charset, byte[] bytes) {
+        int encodedLength = bEncodedLength(bytes);
+
+        int totalLength = prefix.length() + encodedLength
+                + ENC_WORD_SUFFIX.length();
+        if (totalLength <= ENCODED_WORD_MAX_LENGTH - usedCharacters) {
+            return prefix + encodeB(bytes) + ENC_WORD_SUFFIX;
+        } else {
+            int splitOffset = text.offsetByCodePoints(text.length() / 2, -1);
+                                                         
+            String part1 = text.substring(0, splitOffset);
+            byte[] bytes1 = encode(part1, charset);
+            String word1 = encodeB(prefix, part1, usedCharacters, charset,
+                    bytes1);
+
+            String part2 = text.substring(splitOffset);
+            byte[] bytes2 = encode(part2, charset);
+            String word2 = encodeB(prefix, part2, 0, charset, bytes2);
+
+            return word1 + " " + word2;
+        }
+    }
+
+    private static int bEncodedLength(byte[] bytes) {
+        return (bytes.length + 2) / 3 * 4;
+    }
+
+    private static String encodeQ(String prefix, String text, Usage usage,
+            int usedCharacters, Charset charset, byte[] bytes) {
+        int encodedLength = qEncodedLength(bytes, usage);
+
+        int totalLength = prefix.length() + encodedLength
+                + ENC_WORD_SUFFIX.length();
+        if (totalLength <= ENCODED_WORD_MAX_LENGTH - usedCharacters) {
+            return prefix + encodeQ(bytes, usage) + ENC_WORD_SUFFIX;
+        } else {
+            int splitOffset = text.offsetByCodePoints(text.length() / 2, -1);
+
+            String part1 = text.substring(0, splitOffset);
+            byte[] bytes1 = encode(part1, charset);
+            String word1 = encodeQ(prefix, part1, usage, usedCharacters,
+                    charset, bytes1);
+
+            String part2 = text.substring(splitOffset);
+            byte[] bytes2 = encode(part2, charset);
+            String word2 = encodeQ(prefix, part2, usage, 0, charset, bytes2);
+
+            return word1 + " " + word2;
+        }
+    }
+
+    private static int qEncodedLength(byte[] bytes, Usage usage) {
+        BitSet qChars = usage == Usage.TEXT_TOKEN ? Q_REGULAR_CHARS
+                : Q_RESTRICTED_CHARS;
+
+        int count = 0;
+
+        for (int idx = 0; idx < bytes.length; idx++) {
+            int v = bytes[idx] & 0xff;
+            if (v == 32) {
+                count++;
+            } else if (!qChars.get(v)) {
+                count += 3;
+            } else {
+                count++;
+            }
+        }
+
+        return count;
+    }
+
+    private static byte[] encode(String text, Charset charset) {
+        ByteBuffer buffer = charset.encode(text);
+        byte[] bytes = new byte[buffer.limit()];
+        buffer.get(bytes);
+        return bytes;
+    }
+
+    private static Charset determineCharset(String text) {
+        // it is an important property of iso-8859-1 that it directly maps
+        // unicode code points 0000 to 00ff to byte values 00 to ff.
+        boolean ascii = true;
+        final int len = text.length();
+        for (int index = 0; index < len; index++) {
+            char ch = text.charAt(index);
+            if (ch > 0xff) {
+                return CharsetUtil.UTF_8;
+            }
+            if (ch > 0x7f) {
+                ascii = false;
+            }
+        }
+        return ascii ? CharsetUtil.US_ASCII : CharsetUtil.ISO_8859_1;
+    }
+
+    private static Encoding determineEncoding(byte[] bytes, Usage usage) {
+        if (bytes.length == 0)
+            return Encoding.Q;
+
+        BitSet qChars = usage == Usage.TEXT_TOKEN ? Q_REGULAR_CHARS
+                : Q_RESTRICTED_CHARS;
+
+        int qEncoded = 0;
+        for (int i = 0; i < bytes.length; i++) {
+            int v = bytes[i] & 0xff;
+            if (v != 32 && !qChars.get(v)) {
+                qEncoded++;
+            }
+        }
+
+        int percentage = qEncoded * 100 / bytes.length;
+        return percentage > 30 ? Encoding.B : Encoding.Q;
+    }
+
+    private static char hexDigit(int i) {
+        return i < 10 ? (char) (i + '0') : (char) (i - 10 + 'A');
+    }
+}

src/org/apache/james/mime4j/decoder/DecoderUtil.java

@@ -19,15 +19,15 @@
 
 package org.apache.james.mime4j.decoder;
 
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+import org.apache.james.mime4j.util.CharsetUtil;
+
 import java.io.ByteArrayInputStream;
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 import java.io.UnsupportedEncodingException;
 
-import org.apache.commons.logging.Log;
-import org.apache.commons.logging.LogFactory;
-import org.apache.james.mime4j.util.CharsetUtil;
-
 /**
  * Static methods for decoding strings, byte arrays and encoded words.
  *
@@ -146,131 +146,132 @@ public class DecoderUtil {
      * =?charset?enc?Encoded word?= where enc is either 'Q' or 'q' for 
      * quoted-printable and 'B' or 'b' for Base64.
      * 
+     * ANDROID:  COPIED FROM A NEWER VERSION OF MIME4J
+     * 
      * @param body the string to decode.
      * @return the decoded string.
      */
     public static String decodeEncodedWords(String body) {
-        StringBuffer sb = new StringBuffer();
         
-        int p1 = 0;
-        int p2 = 0;
-        
-        try {
-            
-            /*
-             * Encoded words in headers have the form 
-             * =?charset?enc?Encoded word?= where enc is either 'Q' or 'q' for 
-             * quoted printable and 'B' and 'b' for Base64
-             */
-            
-            while (p2 < body.length()) {
-                /*
-                 * Find beginning of first encoded word
-                 */
-                p1 = body.indexOf("=?", p2);
-                if (p1 == -1) {
-                    /*
-                     * None found. Emit the rest of the header and exit.
-                     */
-                    sb.append(body.substring(p2));
-                    break;
-                }
-                
-                /*
-                 * p2 points to the previously found end marker or the start
-                 * of the entire header text. Append the text between that
-                 * marker and the one pointed to by p1.
-                 */
-                if (p1 - p2 > 0) {
-                    sb.append(body.substring(p2, p1));
-                }
-
-                /*
-                 * Find the first and second '?':s after the marker pointed to
-                 * by p1.
-                 */
-                int t1 = body.indexOf('?', p1 + 2);
-                int t2 = t1 != -1 ? body.indexOf('?', t1 + 1) : -1;
-
-                /*
-                 * Find this words end marker.
-                 */
-                p2 = t2 != -1 ? body.indexOf("?=", t2 + 1) : -1;
-                if (p2 == -1) {
-                    if (t2 != -1 && (body.length() - 1 == t2 || body.charAt(t2 + 1) == '=')) {
-                        /*
-                         * Treat "=?charset?enc?" and "=?charset?enc?=" as
-                         * empty strings.
-                         */
-                        p2 = t2;
-                    } else {
-                        /*
-                         * No end marker was found. Append the rest of the 
-                         * header and exit.
-                         */
-                        sb.append(body.substring(p1));
-                        break;
-                    }
-                }
-
-                /*
-                 * [p1+2, t1] -> charset
-                 * [t1+1, t2] -> encoding
-                 * [t2+1, p2] -> encoded word
-                 */
-                
-                String decodedWord = null;
-                if (t2 == p2) {
-                    /*
-                     * The text is empty
-                     */
-                    decodedWord = "";
-                } else {
-
-                    String mimeCharset = body.substring(p1 + 2, t1);
-                    String enc = body.substring(t1 + 1, t2);
-                    String encodedWord = body.substring(t2 + 1, p2);
-
-                    /*
-                     * Convert the MIME charset to a corresponding Java one.
-                     */
-                    String charset = CharsetUtil.toJavaCharset(mimeCharset);
-                    if (charset == null) {
-                        decodedWord = body.substring(p1, p2 + 2);
-                        if (log.isWarnEnabled()) {
-                            log.warn("MIME charset '" + mimeCharset 
-                                    + "' in header field doesn't have a "
-                                    +"corresponding Java charset");
-                        }
-                    } else if (!CharsetUtil.isDecodingSupported(charset)) {
-                        decodedWord = body.substring(p1, p2 + 2);
-                        if (log.isWarnEnabled()) {
-                            log.warn("Current JDK doesn't support decoding "
-                                   + "of charset '" + charset 
-                                   + "' (MIME charset '" 
-                                   + mimeCharset + "')");
-                        }
-                    } else {
-                        if (enc.equalsIgnoreCase("Q")) {
-                            decodedWord = DecoderUtil.decodeQ(encodedWord, charset);
-                        } else if (enc.equalsIgnoreCase("B")) {
-                            decodedWord = DecoderUtil.decodeB(encodedWord, charset);
-                        } else {
-                            decodedWord = encodedWord;
-                            if (log.isWarnEnabled()) {
-                                log.warn("Warning: Unknown encoding in "
-                                        + "header field '" + enc + "'");
-                            }
-                        }
-                    }
-                }
-                p2 += 2;
-                sb.append(decodedWord);
-            }
-        } catch (Throwable t) {
-            log.error("Decoding header field body '" + body + "'", t);
+        // ANDROID:  Most strings will not include "=?" so a quick test can prevent unneeded
+        // object creation.  This could also be handled via lazy creation of the StringBuilder.
+        if (body.indexOf("=?") == -1) {
+            return body;
         }
         
-        return sb.toString();
+        int previousEnd = 0;
+        boolean previousWasEncoded = false;
+
+        StringBuilder sb = new StringBuilder();
+
+        while (true) {
+            int begin = body.indexOf("=?", previousEnd);
+            
+            // ANDROID:  The mime4j original version has an error here.  It gets confused if
+            // the encoded string begins with an '=' (just after "?Q?").  This patch seeks forward
+            // to find the two '?' in the "header", before looking for the final "?=".
+            int endScan = begin + 2;
+            if (begin != -1) {
+                int qm1 = body.indexOf('?', endScan + 2);
+                int qm2 = body.indexOf('?', qm1 + 1);
+                if (qm2 != -1) {
+                    endScan = qm2 + 1;
+                }
+            }
+            
+            int end = begin == -1 ? -1 : body.indexOf("?=", endScan);
+            if (end == -1) {
+                if (previousEnd == 0)
+                    return body;
+
+                sb.append(body.substring(previousEnd));
+                return sb.toString();
+            }
+            end += 2;
+
+            String sep = body.substring(previousEnd, begin);
+
+            String decoded = decodeEncodedWord(body, begin, end);
+            if (decoded == null) {
+                sb.append(sep);
+                sb.append(body.substring(begin, end));
+            } else {
+                if (!previousWasEncoded || !CharsetUtil.isWhitespace(sep)) {
+                    sb.append(sep);
+                }
+                sb.append(decoded);
+            }
+
+            previousEnd = end;
+            previousWasEncoded = decoded != null;
+        }
+    }
+
+    // return null on error
+    private static String decodeEncodedWord(String body, int begin, int end) {
+        int qm1 = body.indexOf('?', begin + 2);
+        if (qm1 == end - 2)
+            return null;
+
+        int qm2 = body.indexOf('?', qm1 + 1);
+        if (qm2 == end - 2)
+            return null;
+
+        String mimeCharset = body.substring(begin + 2, qm1);
+        String encoding = body.substring(qm1 + 1, qm2);
+        String encodedText = body.substring(qm2 + 1, end - 2);
+
+        String charset = CharsetUtil.toJavaCharset(mimeCharset);
+        if (charset == null) {
+            if (log.isWarnEnabled()) {
+                log.warn("MIME charset '" + mimeCharset + "' in encoded word '"
+                        + body.substring(begin, end) + "' doesn't have a "
+                        + "corresponding Java charset");
+            }
+            return null;
+        } else if (!CharsetUtil.isDecodingSupported(charset)) {
+            if (log.isWarnEnabled()) {
+                log.warn("Current JDK doesn't support decoding of charset '"
+                        + charset + "' (MIME charset '" + mimeCharset
+                        + "' in encoded word '" + body.substring(begin, end)
+                        + "')");
+            }
+            return null;
+        }
+
+        if (encodedText.length() == 0) {
+            if (log.isWarnEnabled()) {
+                log.warn("Missing encoded text in encoded word: '"
+                        + body.substring(begin, end) + "'");
+            }
+            return null;
+        }
+
+        try {
+            if (encoding.equalsIgnoreCase("Q")) {
+                return DecoderUtil.decodeQ(encodedText, charset);
+            } else if (encoding.equalsIgnoreCase("B")) {
+                return DecoderUtil.decodeB(encodedText, charset);
+            } else {
+                if (log.isWarnEnabled()) {
+                    log.warn("Warning: Unknown encoding in encoded word '"
+                            + body.substring(begin, end) + "'");
+                }
+                return null;
+            }
+        } catch (UnsupportedEncodingException e) {
+            // should not happen because of isDecodingSupported check above
+            if (log.isWarnEnabled()) {
+                log.warn("Unsupported encoding in encoded word '"
+                        + body.substring(begin, end) + "'", e);
+            }
+            return null;
+        } catch (RuntimeException e) {
+            if (log.isWarnEnabled()) {
+                log.warn("Could not decode encoded word '"
+                        + body.substring(begin, end) + "'", e);
+            }
+            return null;
+        }
     }
 }

src/org/apache/james/mime4j/util/CharsetUtil.java

@@ -1056,6 +1056,73 @@ public class CharsetUtil {
         }
     }
     
+    /**
+     * ANDROID:  THE FOLLOWING SET OF STATIC STRINGS ARE COPIED FROM A NEWER VERSION OF MIME4J
+     */
+    
+    /** carriage return - line feed sequence */
+    public static final String CRLF = "\r\n";
+
+    /** US-ASCII CR, carriage return (13) */
+    public static final int CR = '\r';
+
+    /** US-ASCII LF, line feed (10) */
+    public static final int LF = '\n';
+
+    /** US-ASCII SP, space (32) */
+    public static final int SP = ' ';
+
+    /** US-ASCII HT, horizontal-tab (9)*/
+    public static final int HT = '\t';
+    
+    public static final java.nio.charset.Charset US_ASCII = java.nio.charset.Charset
+            .forName("US-ASCII");
+
+    public static final java.nio.charset.Charset ISO_8859_1 = java.nio.charset.Charset
+            .forName("ISO-8859-1");
+
+    public static final java.nio.charset.Charset UTF_8 = java.nio.charset.Charset
+            .forName("UTF-8");
+
+    /**
+     * Returns <code>true</code> if the specified character is a whitespace
+     * character (CR, LF, SP or HT).
+     * 
+     * ANDROID:  COPIED FROM A NEWER VERSION OF MIME4J
+     * 
+     * @param ch
+     *            character to test.
+     * @return <code>true</code> if the specified character is a whitespace
+     *         character, <code>false</code> otherwise.
+     */
+    public static boolean isWhitespace(char ch) {
+        return ch == SP || ch == HT || ch == CR || ch == LF;
+    }
+
+    /**
+     * Returns <code>true</code> if the specified string consists entirely of
+     * whitespace characters.
+     * 
+     * ANDROID:  COPIED FROM A NEWER VERSION OF MIME4J
+     * 
+     * @param s
+     *            string to test.
+     * @return <code>true</code> if the specified string consists entirely of
+     *         whitespace characters, <code>false</code> otherwise.
+     */
+    public static boolean isWhitespace(final String s) {
+        if (s == null) {
+            throw new IllegalArgumentException("String may not be null");
+        }
+        final int len = s.length();
+        for (int i = 0; i < len; i++) {
+            if (!isWhitespace(s.charAt(i))) {
+                return false;
+            }
+        }
+        return true;
+    }
+
     /**
      * Determines if the VM supports encoding (chars to bytes) the 
      * specified character set. NOTE: the given character set name may