[CODEC-121] QuotedPrintableCodec does not support soft line break per the 'quoted-printable' example on Wikipedia. Apply patch from TN.

garydgregory · garydgregory · commit bdc77f1b289f · 2014-11-05T23:43:14.000Z
git-svn-id: https://svn.apache.org/repos/asf/commons/proper/codec/trunk@1637008 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/src/changes/changes.xml b/src/changes/changes.xml
@@ -44,6 +44,7 @@ The <action> type attribute can be add,update,fix,remove.
   <body>
     <release version="1.10" date="DD November 2014" description="Feature and fix release.">
       <action dev="ggregory" type="add" issue="CODEC-192" due-to="Thomas Neidhart">Add Daitch-Mokotoff Soundex</action>   
+      <action dev="ggregory" type="add" issue="CODEC-121" due-to="Thomas Neidhart, Java John">QuotedPrintableCodec does not support soft line break per the 'quoted-printable' example on Wikipedia</action>   
       <action dev="tn" type="fix" issue="CODEC-185" due-to="Sean Busbey">Added clarification to Javadoc of Base64 concerning the use of the urlSafe parameter</action>   
       <action dev="tn" type="fix" issue="CODEC-191" due-to="Igor Savin">Added clarification to the Javadoc of Base[32|64]OutputStream that it is mandatory to call close()</action>   
       <action dev="ggregory" type="fix" issue="CODEC-188" due-to="Hendrik Saly">Add support for HMAC Message Authentication Code (MAC) digests</action>   
diff --git a/src/main/java/org/apache/commons/codec/net/QuotedPrintableCodec.java b/src/main/java/org/apache/commons/codec/net/QuotedPrintableCodec.java
@@ -45,14 +45,19 @@
  * <p>
  * Note:
  * <p>
- * Rules #3, #4, and #5 of the quoted-printable spec are not implemented yet because the complete quoted-printable spec
- * does not lend itself well into the byte[] oriented codec framework. Complete the codec once the streamable codec
- * framework is ready. The motivation behind providing the codec in a partial form is that it can already come in handy
- * for those applications that do not require quoted-printable line formatting (rules #3, #4, #5), for instance Q codec.
+ * Depending on the selected {@code strict} parameter, this class will implement a different set of rules of the
+ * quoted-printable spec:
+ * <ul>
+ *   <li>{@code strict=false}: only rules #1 and #2 are implemented 
+ *   <li>{@code strict=true}: all rules #1 through #5 are implemented
+ * </ul>
+ * Originally, this class only supported the non-strict mode, but the codec in this partial form could already be used
+ * for certain applications that do not require quoted-printable line formatting (rules #3, #4, #5), for instance Q codec.
+ * The strict mode has been added in 1.10.
  * <p>
  * This class is immutable and thread-safe.
  *
- * @see <a href="http://www.ietf.org/rfc/rfc1521.txt"> RFC 1521 MIME (Multipurpose Internet Mail Extensions) Part One:
+ * @see <a href="http://www.ietf.org/rfc/rfc1521.txt">RFC 1521 MIME (Multipurpose Internet Mail Extensions) Part One:
  *          Mechanisms for Specifying and Describing the Format of Internet Message Bodies </a>
  *
  * @since 1.3
@@ -64,6 +69,11 @@ public class QuotedPrintableCodec implements BinaryEncoder, BinaryDecoder, Strin
      */
     private final Charset charset;
 
+    /**
+     * Indicates whether soft line breaks shall be used during encoding (rule #3-5).
+     */
+    private final boolean strict;
+
     /**
      * BitSet of printable characters as defined in RFC 1521.
      */
@@ -74,6 +84,16 @@ public class QuotedPrintableCodec implements BinaryEncoder, BinaryDecoder, Strin
     private static final byte TAB = 9;
 
     private static final byte SPACE = 32;
+
+    private static final byte CR = 13;
+
+    private static final byte LF = 10;
+
+    /**
+     * Safe line length for quoted printable encoded text.
+     */
+    private static final int SAFE_LENGTH = 73;
+
     // Static initializer for printable chars collection
     static {
         // alpha characters
@@ -91,7 +111,18 @@ public class QuotedPrintableCodec implements BinaryEncoder, BinaryDecoder, Strin
      * Default constructor, assumes default charset of {@link Charsets#UTF_8}
      */
     public QuotedPrintableCodec() {
-        this(Charsets.UTF_8);
+        this(Charsets.UTF_8, false);
+    }
+
+    /**
+     * Constructor which allows for the selection of the strict mode.
+     *
+     * @param strict
+     *            if {@code true}, soft line breaks will be used
+     * @since 1.10
+     */
+    public QuotedPrintableCodec(final boolean strict) {
+        this(Charsets.UTF_8, strict);
     }
 
     /**
@@ -102,7 +133,21 @@ public QuotedPrintableCodec() {
      * @since 1.7
      */
     public QuotedPrintableCodec(final Charset charset) {
+        this(charset, false);
+    }
+
+    /**
+     * Constructor which allows for the selection of a default charset and strict mode.
+     *
+     * @param charset
+     *            the default string charset to use.
+     * @param strict
+     *            if {@code true}, soft line breaks will be used
+     * @since 1.10
+     */
+    public QuotedPrintableCodec(final Charset charset, final boolean strict) {
         this.charset = charset;
+        this.strict = strict;
     }
 
     /**
@@ -122,7 +167,7 @@ public QuotedPrintableCodec(final Charset charset) {
      */
     public QuotedPrintableCodec(final String charsetName)
             throws IllegalCharsetNameException, IllegalArgumentException, UnsupportedCharsetException {
-        this(Charset.forName(charsetName));
+        this(Charset.forName(charsetName), false);
     }
 
     /**
@@ -132,13 +177,65 @@ public QuotedPrintableCodec(final String charsetName)
      *            byte to encode
      * @param buffer
      *            the buffer to write to
+     * @return The number of bytes written to the <code>buffer</code>
      */
-    private static final void encodeQuotedPrintable(final int b, final ByteArrayOutputStream buffer) {
+    private static final int encodeQuotedPrintable(final int b, final ByteArrayOutputStream buffer) {
         buffer.write(ESCAPE_CHAR);
         final char hex1 = Character.toUpperCase(Character.forDigit((b >> 4) & 0xF, 16));
         final char hex2 = Character.toUpperCase(Character.forDigit(b & 0xF, 16));
         buffer.write(hex1);
         buffer.write(hex2);
+        return 3;
+    }
+
+    /**
+     * Return the byte at position <code>index</code> of the byte array and
+     * make sure it is unsigned.
+     *
+     * @param index
+     *            position in the array
+     * @param bytes
+     *            the byte array
+     * @return the unsigned octet at position <code>index</code> from the array
+     */
+    private static int getUnsignedOctet(final int index, final byte[] bytes) {
+        int b = bytes[index];
+        if (b < 0) {
+            b = 256 + b;
+        }
+        return b;
+    }
+
+    /**
+     * Write a byte to the buffer.
+     *
+     * @param b
+     *            byte to write
+     * @param encode
+     *            indicates whether the octet shall be encoded
+     * @param buffer
+     *            the buffer to write to
+     * @return the number of bytes that have been written to the buffer
+     */
+    private static int encodeByte(final int b, final boolean encode,
+                                  final ByteArrayOutputStream buffer) {
+        if (encode) {
+            return encodeQuotedPrintable(b, buffer);
+        } else {
+            buffer.write(b);
+            return 1;
+        }
+    }
+
+    /**
+     * Checks whether the given byte is whitespace.
+     *
+     * @param b
+     *            byte to be checked
+     * @return <code>true</code> if the byte is either a space or tab character
+     */
+    private static boolean isWhitespace(final int b) {
+        return b == SPACE || b == TAB;
     }
 
     /**
@@ -154,22 +251,86 @@ private static final void encodeQuotedPrintable(final int b, final ByteArrayOutp
      * @return array of bytes containing quoted-printable data
      */
     public static final byte[] encodeQuotedPrintable(BitSet printable, final byte[] bytes) {
+        return encodeQuotedPrintable(printable, bytes, false);
+    }
+
+    /**
+     * Encodes an array of bytes into an array of quoted-printable 7-bit characters. Unsafe characters are escaped.
+     * <p>
+     * Depending on the selection of the {@code strict} parameter, this function either implements the full ruleset
+     * or only a subset of quoted-printable encoding specification (rule #1 and rule #2) as defined in
+     * RFC 1521 and is suitable for encoding binary data and unformatted text.
+     *
+     * @param printable
+     *            bitset of characters deemed quoted-printable
+     * @param bytes
+     *            array of bytes to be encoded
+     * @param strict
+     *            if {@code true} the full ruleset is used, otherwise only rule #1 and rule #2
+     * @return array of bytes containing quoted-printable data
+     * @since 1.10
+     */
+    public static final byte[] encodeQuotedPrintable(BitSet printable, final byte[] bytes, boolean strict) {
         if (bytes == null) {
             return null;
         }
         if (printable == null) {
             printable = PRINTABLE_CHARS;
         }
         final ByteArrayOutputStream buffer = new ByteArrayOutputStream();
-        for (final byte c : bytes) {
-            int b = c;
-            if (b < 0) {
-                b = 256 + b;
+        
+        if (strict) {
+            int pos = 1;
+            // encode up to buffer.length - 3, the last three octets will be treated
+            // separately for simplification of note #3
+            for (int i = 0; i < bytes.length - 3; i++) {
+                int b = getUnsignedOctet(i, bytes);
+                if (pos < SAFE_LENGTH) {
+                    // up to this length it is safe to add any byte, encoded or not
+                    pos += encodeByte(b, !printable.get(b), buffer);
+                } else {
+                    // rule #3: whitespace at the end of a line *must* be encoded
+                    encodeByte(b, !printable.get(b) || isWhitespace(b), buffer);
+
+                    // rule #5: soft line break
+                    buffer.write(ESCAPE_CHAR);
+                    buffer.write(CR);
+                    buffer.write(LF);
+                    pos = 1;
+                }
             }
-            if (printable.get(b)) {
-                buffer.write(b);
-            } else {
-                encodeQuotedPrintable(b, buffer);
+
+            // rule #3: whitespace at the end of a line *must* be encoded
+            // if we would do a soft break line after this octet, encode whitespace
+            int b = getUnsignedOctet(bytes.length - 3, bytes);
+            boolean encode = !printable.get(b) || (isWhitespace(b) && pos > SAFE_LENGTH - 5);
+            pos += encodeByte(b, encode, buffer);
+
+            // note #3: '=' *must not* be the ultimate or penultimate character
+            // simplification: if < 6 bytes left, do a soft line break as we may need
+            //                 exactly 6 bytes space for the last 2 bytes
+            if (pos > SAFE_LENGTH - 2) {
+                buffer.write(ESCAPE_CHAR);
+                buffer.write(CR);
+                buffer.write(LF);
+            }
+            for (int i = bytes.length - 2; i < bytes.length; i++) {
+                b = getUnsignedOctet(i, bytes);
+                // rule #3: trailing whitespace shall be encoded
+                encode = !printable.get(b) || (i > bytes.length - 2 && isWhitespace(b));
+                encodeByte(b, encode, buffer);
+            }
+        } else {
+            for (final byte c : bytes) {
+                int b = c;
+                if (b < 0) {
+                    b = 256 + b;
+                }
+                if (printable.get(b)) {
+                    buffer.write(b);
+                } else {
+                    encodeQuotedPrintable(b, buffer);
+                }
             }
         }
         return buffer.toByteArray();
@@ -179,8 +340,8 @@ public static final byte[] encodeQuotedPrintable(BitSet printable, final byte[]
      * Decodes an array quoted-printable characters into an array of original bytes. Escaped characters are converted
      * back to their original representation.
      * <p>
-     * This function implements a subset of quoted-printable encoding specification (rule #1 and rule #2) as defined in
-     * RFC 1521.
+     * This function fully implements the quoted-printable encoding specification (rule #1 through rule #5) as
+     * defined in RFC 1521.
      *
      * @param bytes
      *            array of quoted-printable characters
@@ -197,13 +358,18 @@ public static final byte[] decodeQuotedPrintable(final byte[] bytes) throws Deco
             final int b = bytes[i];
             if (b == ESCAPE_CHAR) {
                 try {
-                    final int u = Utils.digit16(bytes[++i]);
+                    // if the next octet is a CR we have found a soft line break
+                    if (bytes[++i] == CR) {
+                        continue;
+                    }
+                    final int u = Utils.digit16(bytes[i]);
                     final int l = Utils.digit16(bytes[++i]);
                     buffer.write((char) ((u << 4) + l));
                 } catch (final ArrayIndexOutOfBoundsException e) {
                     throw new DecoderException("Invalid quoted-printable encoding", e);
                 }
-            } else {
+            } else if (b != CR && b != LF) {
+                // every other octet is appended except for CR & LF
                 buffer.write(b);
             }
         }
@@ -213,7 +379,8 @@ public static final byte[] decodeQuotedPrintable(final byte[] bytes) throws Deco
     /**
      * Encodes an array of bytes into an array of quoted-printable 7-bit characters. Unsafe characters are escaped.
      * <p>
-     * This function implements a subset of quoted-printable encoding specification (rule #1 and rule #2) as defined in
+     * Depending on the selection of the {@code strict} parameter, this function either implements the full ruleset
+     * or only a subset of quoted-printable encoding specification (rule #1 and rule #2) as defined in
      * RFC 1521 and is suitable for encoding binary data and unformatted text.
      *
      * @param bytes
@@ -222,15 +389,15 @@ public static final byte[] decodeQuotedPrintable(final byte[] bytes) throws Deco
      */
     @Override
     public byte[] encode(final byte[] bytes) {
-        return encodeQuotedPrintable(PRINTABLE_CHARS, bytes);
+        return encodeQuotedPrintable(PRINTABLE_CHARS, bytes, strict);
     }
 
     /**
      * Decodes an array of quoted-printable characters into an array of original bytes. Escaped characters are converted
      * back to their original representation.
      * <p>
-     * This function implements a subset of quoted-printable encoding specification (rule #1 and rule #2) as defined in
-     * RFC 1521.
+     * This function fully implements the quoted-printable encoding specification (rule #1 through rule #5) as
+     * defined in RFC 1521.
      *
      * @param bytes
      *            array of quoted-printable characters
@@ -246,8 +413,9 @@ public byte[] decode(final byte[] bytes) throws DecoderException {
     /**
      * Encodes a string into its quoted-printable form using the default string charset. Unsafe characters are escaped.
      * <p>
-     * This function implements a subset of quoted-printable encoding specification (rule #1 and rule #2) as defined in
-     * RFC 1521 and is suitable for encoding binary data.
+     * Depending on the selection of the {@code strict} parameter, this function either implements the full ruleset
+     * or only a subset of quoted-printable encoding specification (rule #1 and rule #2) as defined in
+     * RFC 1521 and is suitable for encoding binary data and unformatted text.
      *
      * @param str
      *            string to convert to quoted-printable form
@@ -392,7 +560,8 @@ public String getDefaultCharset() {
     /**
      * Encodes a string into its quoted-printable form using the specified charset. Unsafe characters are escaped.
      * <p>
-     * This function implements a subset of quoted-printable encoding specification (rule #1 and rule #2) as defined in
+     * Depending on the selection of the {@code strict} parameter, this function either implements the full ruleset
+     * or only a subset of quoted-printable encoding specification (rule #1 and rule #2) as defined in
      * RFC 1521 and is suitable for encoding binary data and unformatted text.
      *
      * @param str
@@ -412,7 +581,8 @@ public String encode(final String str, final Charset charset) {
     /**
      * Encodes a string into its quoted-printable form using the specified charset. Unsafe characters are escaped.
      * <p>
-     * This function implements a subset of quoted-printable encoding specification (rule #1 and rule #2) as defined in
+     * Depending on the selection of the {@code strict} parameter, this function either implements the full ruleset
+     * or only a subset of quoted-printable encoding specification (rule #1 and rule #2) as defined in
      * RFC 1521 and is suitable for encoding binary data and unformatted text.
      *
      * @param str
diff --git a/src/test/java/org/apache/commons/codec/net/QuotedPrintableCodecTest.java b/src/test/java/org/apache/commons/codec/net/QuotedPrintableCodecTest.java
