a new java implementation of base64 for android-common

A new Base64 encoder/decoder class.  Some benchmarks comparing the
decoder it to those from android.os.Base64Utils (a decode-only native
implementation not accessible to apps) and
org.apache.commons.codec.binary.Base64, all with the JIT enabled:

  1k encoded data
  APACHE   avg:   811 us    min:   244 us    max: 13671 us
  COMMON   avg:   263 us    min:    30 us    max:  4730 us
  NATIVE   avg:   102 us    min:    61 us    max:  5493 us

  10k encoded data
  APACHE   avg:  3624 us    min:  2746 us    max: 23895 us
  COMMON   avg:   979 us    min:   518 us    max:  7751 us
  NATIVE   avg:   817 us    min:   762 us    max:  3143 us

  100k encoded data
  APACHE   avg: 33167 us    min: 31829 us    max: 140411 us
  COMMON   avg:  6047 us    min:  5493 us    max: 45227 us
  NATIVE   avg: 10109 us    min: 10009 us    max: 12451 us

Change-Id: Ic622e3a967a62d57d30bd25b80cbe4e0dd60e764

2 files changed, 705 insertions, 0 deletions

diff --git a/common/java/com/android/common/Base64.java b/common/java/com/android/common/Base64.java
new file mode 100644
index 0000000..d108f44
--- /dev/null
+++ b/common/java/com/android/common/Base64.java
@@ -0,0 +1,497 @@
+/*
+ * Copyright (C) 2010 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.android.common;
+
+/**
+ * Utilities for encoding and decoding the Base64 encoding.  See RFCs
+ * 2045 and 3548.
+ */
+public class Base64 {
+    /**
+     * Encoder flag bit to indicate you want the padding '='
+     * characters at the end (if any) to be omitted.
+     */
+    public static final int NO_PADDING = 1;
+
+    /**
+     * Encoder flag bit to indicate you want all line terminators to
+     * be omitted (ie, the output will be on one long line).
+     */
+    public static final int NO_WRAP = 2;
+
+    /**
+     * Encoder flag bit to indicate you want lines to be ended with
+     * CRLF instead of just LF.
+     */
+    public static final int CRLF = 4;
+
+    /**
+     * Encoder/decoder flag bit to indicate using the "web safe"
+     * variant of Base64 (see RFC 3548 section 4) where '-' and '_'
+     * are used in place of '+' and '/'.
+     */
+    public static final int WEB_SAFE = 8;
+
+    /**
+     * Lookup table for turning bytes into their position in the
+     * Base64 alphabet.
+     */
+    private static final int DECODE[] = {
+        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63,
+        52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -2, -1, -1,
+        -1,  0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14,
+        15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1,
+        -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
+        41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1,
+        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+    };
+
+    /**
+     * Decode lookup table for the "web safe" variant (RFC 3548
+     * sec. 4) where - and _ replace + and /.
+     */
+    private static final int DECODE_WEBSAFE[] = {
+        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1,
+        52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -2, -1, -1,
+        -1,  0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14,
+        15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, 63,
+        -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
+        41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1,
+        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+    };
+
+    /** Non-data values in the DECODE arrays. */
+    private static final int SKIP = -1;
+    private static final int EQUALS = -2;
+
+    /**
+     * Decode the Base64-encoded data in input and return the data in
+     * a new byte array.
+     *
+     * The padding '=' characters at the end are considered optional, but
+     * if any are present, there must be the correct number of them.
+     *
+     * @param input the input String to decode, which is converted to
+     *               bytes using the default charset
+     * @param flags  controls certain features of the decoded output.
+     *               Passing 0 to decode standard Base64.
+     *
+     * @throws IllegalArgumentException if the input contains
+     * incorrect padding
+     */
+    public static byte[] decode(String str, int flags) {
+        return decode(str.getBytes(), flags);
+    }
+
+    /**
+     * Decode the Base64-encoded data in input and return the data in
+     * a new byte array.
+     *
+     * The padding '=' characters at the end are considered optional, but
+     * if any are present, there must be the correct number of them.
+     *
+     * @param input the input array to decode
+     * @param flags  controls certain features of the decoded output.
+     *               Passing 0 to decode standard Base64.
+     *
+     * @throws IllegalArgumentException if the input contains
+     * incorrect padding
+     */
+    public static byte[] decode(byte[] input, int flags) {
+        return decode(input, 0, input.length, flags);
+    }
+
+    /**
+     * Decode the Base64-encoded data in input and return the data in
+     * a new byte array.
+     *
+     * The padding '=' characters at the end are considered optional, but
+     * if any are present, there must be the correct number of them.
+     *
+     * @param input  the data to decode
+     * @param offset the position within the input array at which to start
+     * @param len    the number of bytes of input to decode
+     * @param flags  controls certain features of the decoded output.
+     *               Passing 0 to decode standard Base64.
+     *
+     * @throws IllegalArgumentException if the input contains
+     * incorrect padding
+     */
+    public static byte[] decode(byte[] input, int offset, int len, int flags) {
+        int p = offset;
+        // Allocate space for the most data the input could represent.
+        // (It could contain less if it contains whitespace, etc.)
+        byte[] output = new byte[len*3/4];
+        len += offset;
+        int op = 0;
+
+        final int[] decode = ((flags & WEB_SAFE) == 0) ?
+            DECODE : DECODE_WEBSAFE;
+
+        int state = 0;
+        int value = 0;
+
+        while (p < len) {
+
+            // Try the fast path:  we're starting a new tuple and the
+            // next four bytes of the input stream are all data
+            // bytes.  This corresponds to going through states
+            // 0-1-2-3-0.  We expect to use this method for most of
+            // the data.
+            //
+            // If any of the next four bytes of input are non-data
+            // (whitespace, etc.), value will end up negative.  (All
+            // the non-data values in decode are small negative
+            // numbers, so shifting any of them up and or'ing them
+            // together will result in a value with its top bit set.)
+            //
+            // You can remove this whole block and the output should
+            // be the same, just slower.
+            if (state == 0 && p+4 <= len &&
+                (value = ((decode[input[p] & 0xff] << 18) |
+                          (decode[input[p+1] & 0xff] << 12) |
+                          (decode[input[p+2] & 0xff] << 6) |
+                          (decode[input[p+3] & 0xff]))) >= 0) {
+                output[op+2] = (byte) value;
+                output[op+1] = (byte) (value >> 8);
+                output[op] = (byte) (value >> 16);
+                op += 3;
+                p += 4;
+                continue;
+            }
+
+            // The fast path isn't available -- either we've read a
+            // partial tuple, or the next four input bytes aren't all
+            // data, or whatever.  Fall back to the slower state
+            // machine implementation.
+            //
+            // States 0-3 are reading through the next input tuple.
+            // State 4 is having read one '=' and expecting exactly
+            // one more.
+            // State 5 is expecting no more data or padding characters
+            // in the input.
+
+            int d = decode[input[p++] & 0xff];
+
+            switch (state) {
+                case 0:
+                    if (d >= 0) {
+                        value = d;
+                        ++state;
+                    } else if (d != SKIP) {
+                        throw new IllegalArgumentException("bad base-64");
+                    }
+                    break;
+
+                case 1:
+                    if (d >= 0) {
+                        value = (value << 6) | d;
+                        ++state;
+                    } else if (d != SKIP) {
+                        throw new IllegalArgumentException("bad base-64");
+                    }
+                    break;
+
+                case 2:
+                    if (d >= 0) {
+                        value = (value << 6) | d;
+                        ++state;
+                    } else if (d == EQUALS) {
+                        // Emit the last (partial) output tuple;
+                        // expect exactly one more padding character.
+                        output[op++] = (byte) (value >> 4);
+                        state = 4;
+                    } else if (d != SKIP) {
+                        throw new IllegalArgumentException("bad base-64");
+                    }
+                    break;
+
+                case 3:
+                    if (d >= 0) {
+                        // Emit the output triple and return to state 0.
+                        value = (value << 6) | d;
+                        output[op+2] = (byte) value;
+                        output[op+1] = (byte) (value >> 8);
+                        output[op] = (byte) (value >> 16);
+                        op += 3;
+                        state = 0;
+                    } else if (d == EQUALS) {
+                        // Emit the last (partial) output tuple;
+                        // expect no further data or padding characters.
+                        output[op+1] = (byte) (value >> 2);
+                        output[op] = (byte) (value >> 10);
+                        op += 2;
+                        state = 5;
+                    } else if (d != SKIP) {
+                        throw new IllegalArgumentException("bad base-64");
+                    }
+                    break;
+
+                case 4:
+                    if (d == EQUALS) {
+                        ++state;
+                    } else if (d != SKIP) {
+                        throw new IllegalArgumentException("bad base-64");
+                    }
+                    break;
+
+                case 5:
+                    if (d != SKIP) {
+                        throw new IllegalArgumentException("bad base-64");
+                    }
+                    break;
+            }
+        }
+
+        // Done reading input.  Now figure out where we are left in
+        // the state machine and finish up.
+
+        switch (state) {
+            case 0:
+                // Output length is a multiple of three.  Fine.
+                break;
+            case 1:
+                // Read one extra input byte, which isn't enough to
+                // make another output byte.  Illegal.
+                throw new IllegalArgumentException("bad base-64");
+            case 2:
+                // Read two extra input bytes, enough to emit 1 more
+                // output byte.  Fine.
+                output[op++] = (byte) (value >> 4);
+                break;
+            case 3:
+                // Read three extra input bytes, enough to emit 2 more
+                // output bytes.  Fine.
+                output[op+1] = (byte) (value >> 2);
+                output[op] = (byte) (value >> 10);
+                op += 2;
+                break;
+            case 4:
+                // Read one padding '=' when we expected 2.  Illegal.
+                throw new IllegalArgumentException("bad base-64");
+            case 5:
+                // Read all the padding '='s we expected and no more.
+                // Fine.
+                break;
+        }
+
+        // Maybe we got lucky and allocated exactly enough output space.
+        if (op == output.length) {
+            return output;
+        }
+
+        // Need to shorten the array, so allocate a new one of the
+        // right size and copy.
+        byte[] temp = new byte[op];
+        System.arraycopy(output, 0, temp, 0, op);
+        return temp;
+    }
+
+    /**
+     * Emit a new line every this many output tuples.  Corresponds to
+     * a 76-character line length (the maximum allowable according to
+     * RFC 2045).
+     */
+    private static final int LINE_GROUPS = 19;
+
+    /**
+     * Lookup table for turning Base64 alphabet positions (6 bits)
+     * into output bytes.
+     */
+    private static final byte ENCODE[] = {
+        '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', '+', '/',
+    };
+
+    /**
+     * Lookup table for turning Base64 alphabet positions (6 bits)
+     * into output bytes.
+     */
+    private static final byte ENCODE_WEBSAFE[] = {
+        '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', '-', '_',
+    };
+
+    /**
+     * Base64-encode the given data and return a newly allocated
+     * String with the result.
+     *
+     * @param input  the data to encode
+     * @param flags  controls certain features of the encoded output.
+     *               Passing 0 results in output that adheres to RFC
+     *               2045.
+     */
+    public static String encodeString(byte[] input, int flags) {
+        return new String(encode(input, flags));
+    }
+
+    /**
+     * Base64-encode the given data and return a newly allocated
+     * String with the result.
+     *
+     * @param input  the data to encode
+     * @param offset the position within the input array at which to
+     *               start
+     * @param len    the number of bytes of input to encode
+     * @param flags  controls certain features of the encoded output.
+     *               Passing 0 results in output that adheres to RFC
+     *               2045.
+     */
+    public static String encodeString(byte[] input, int offset, int len, int flags) {
+        return new String(encode(input, offset, len, flags));
+    }
+
+    /**
+     * Base64-encode the given data and return a newly allocated
+     * byte[] with the result.
+     *
+     * @param input  the data to encode
+     * @param flags  controls certain features of the encoded output.
+     *               Passing 0 results in output that adheres to RFC
+     *               2045.
+     */
+    public static byte[] encode(byte[] input, int flags) {
+        return encode(input, 0, input.length, flags);
+    }
+
+    /**
+     * Base64-encode the given data and return a newly allocated
+     * byte[] with the result.
+     *
+     * @param input  the data to encode
+     * @param offset the position within the input array at which to
+     *               start
+     * @param len    the number of bytes of input to encode
+     * @param flags  controls certain features of the encoded output.
+     *               Passing 0 results in output that adheres to RFC
+     *               2045.
+     */
+    public static byte[] encode(byte[] input, int offset, int len, int flags) {
+        final boolean do_padding = (flags & NO_PADDING) == 0;
+        final boolean do_newline = (flags & NO_WRAP) == 0;
+        final boolean do_cr = (flags & CRLF) != 0;
+
+        final byte[] encode = ((flags & WEB_SAFE) == 0) ? ENCODE : ENCODE_WEBSAFE;
+
+        // Compute the exact length of the array we will produce.
+        int output_len = len / 3 * 4;
+
+        // Account for the tail of the data and the padding bytes, if any.
+        if (do_padding) {
+            if (len % 3 > 0) {
+                output_len += 4;
+            }
+        } else {
+            switch (len % 3) {
+                case 0: break;
+                case 1: output_len += 2; break;
+                case 2: output_len += 3; break;
+            }
+        }
+
+        // Account for the newlines, if any.
+        if (do_newline && len > 0) {
+            output_len += (((len-1) / (3 * LINE_GROUPS)) + 1) * (do_cr ? 2 : 1);
+        }
+
+        int op = 0;
+        byte[] output = new byte[output_len];
+
+        // The main loop, turning 3 input bytes into 4 output bytes on
+        // each iteration.
+        int count = do_newline ? LINE_GROUPS : -1;
+        int p = offset;
+        len += offset;
+        while (p+3 <= len) {
+            int v = ((input[p++] & 0xff) << 16) |
+                ((input[p++] & 0xff) << 8) |
+                (input[p++] & 0xff);
+            output[op++] = encode[(v >> 18) & 0x3f];
+            output[op++] = encode[(v >> 12) & 0x3f];
+            output[op++] = encode[(v >> 6) & 0x3f];
+            output[op++] = encode[v & 0x3f];
+            if (--count == 0) {
+                if (do_cr) output[op++] = '\r';
+                output[op++] = '\n';
+                count = LINE_GROUPS;
+            }
+        }
+
+        // Finish up the tail of the input.
+        if (p == len-1) {
+            int v = (input[p] & 0xff) << 4;
+            output[op++] = encode[(v >> 6) & 0x3f];
+            output[op++] = encode[v & 0x3f];
+            if (do_padding) {
+                output[op++] = '=';
+                output[op++] = '=';
+            }
+            if (do_newline) {
+                if (do_cr) output[op++] = '\r';
+                output[op++] = '\n';
+            }
+        } else if (p == len-2) {
+            int v = ((input[p] & 0xff) << 10) | ((input[p+1] & 0xff) << 2);
+            output[op++] = encode[(v >> 12) & 0x3f];
+            output[op++] = encode[(v >> 6) & 0x3f];
+            output[op++] = encode[v & 0x3f];
+            if (do_padding) {
+                output[op++] = '=';
+            }
+            if (do_newline) {
+                if (do_cr) output[op++] = '\r';
+                output[op++] = '\n';
+            }
+        } else if (do_newline && op > 0 && count != LINE_GROUPS) {
+            if (do_cr) output[op++] = '\r';
+            output[op++] = '\n';
+        }
+
+        assert op == output.length;
+        return output;
+    }
+}
diff --git a/common/tests/src/com/android/common/Base64Test.java b/common/tests/src/com/android/common/Base64Test.java
new file mode 100644
index 0000000..39c4b20
--- /dev/null
+++ b/common/tests/src/com/android/common/Base64Test.java
@@ -0,0 +1,208 @@
+/*
+ * Copyright (C) 2010 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.android.common;
+
+import junit.framework.TestCase;
+
+public class Base64Test extends TestCase {
+    private static final String TAG = "B64Test";
+
+    /** Decodes a string, returning a string. */
+    private String decodeString(String in) throws Exception {
+        byte[] out = Base64.decode(in, 0);
+        return new String(out);
+    }
+
+    /**
+     * Encodes the string 'in' using 'flags'.  Asserts that decoding
+     * gives the same string.  Returns the encoded string.
+     */
+    private String encodeString(String in, int flags) throws Exception {
+        String b64 = Base64.encodeString(in.getBytes(), flags);
+        String dec = decodeString(b64);
+        assertEquals(in, dec);
+        return b64;
+    }
+
+    /** Assert that decoding 'in' throws IllegalArgumentException. */
+    private void assertBad(String in) throws Exception {
+        try {
+            byte[] out = Base64.decode(in, 0);
+            fail("should have failed to decode");
+        } catch (IllegalArgumentException e) {
+        }
+    }
+
+    /** Assert that actual equals the first len bytes of expected. */
+    private void assertEquals(byte[] expected, int len, byte[] actual) {
+        assertEquals(len, actual.length);
+        for (int i = 0; i < len; ++i) {
+            assertEquals(expected[i], actual[i]);
+        }
+    }
+
+    public void testDecodeExtraChars() throws Exception {
+        // padding 0
+        assertEquals("hello, world", decodeString("aGVsbG8sIHdvcmxk"));
+        assertBad("aGVsbG8sIHdvcmxk=");
+        assertBad("aGVsbG8sIHdvcmxk==");
+        assertBad("aGVsbG8sIHdvcmxk =");
+        assertBad("aGVsbG8sIHdvcmxk = = ");
+        assertEquals("hello, world", decodeString(" aGVs bG8s IHdv cmxk  "));
+        assertEquals("hello, world", decodeString(" aGV sbG8 sIHd vcmx k "));
+        assertEquals("hello, world", decodeString(" aG VsbG 8sIH dvcm xk "));
+        assertEquals("hello, world", decodeString(" a GVsb G8sI Hdvc mxk "));
+        assertEquals("hello, world", decodeString(" a G V s b G 8 s I H d v c m x k "));
+        assertEquals("hello, world", decodeString("_a*G_V*s_b*G_8*s_I*H_d*v_c*m_x*k_"));
+        assertEquals("hello, world", decodeString("aGVsbG8sIHdvcmxk"));
+
+        // padding 1
+        assertEquals("hello, world?!", decodeString("aGVsbG8sIHdvcmxkPyE="));
+        assertEquals("hello, world?!", decodeString("aGVsbG8sIHdvcmxkPyE"));
+        assertBad("aGVsbG8sIHdvcmxkPyE==");
+        assertBad("aGVsbG8sIHdvcmxkPyE ==");
+        assertBad("aGVsbG8sIHdvcmxkPyE = = ");
+        assertEquals("hello, world?!", decodeString("aGVsbG8sIHdvcmxkPy E="));
+        assertEquals("hello, world?!", decodeString("aGVsbG8sIHdvcmxkPy E"));
+        assertEquals("hello, world?!", decodeString("aGVsbG8sIHdvcmxkPy E ="));
+        assertEquals("hello, world?!", decodeString("aGVsbG8sIHdvcmxkPy E "));
+        assertEquals("hello, world?!", decodeString("aGVsbG8sIHdvcmxkPy E = "));
+        assertEquals("hello, world?!", decodeString("aGVsbG8sIHdvcmxkPy E   "));
+
+        // padding 2
+        assertEquals("hello, world.", decodeString("aGVsbG8sIHdvcmxkLg=="));
+        assertEquals("hello, world.", decodeString("aGVsbG8sIHdvcmxkLg"));
+        assertBad("aGVsbG8sIHdvcmxkLg=");
+        assertBad("aGVsbG8sIHdvcmxkLg =");
+        assertBad("aGVsbG8sIHdvcmxkLg = ");
+        assertEquals("hello, world.", decodeString("aGVsbG8sIHdvcmxkL g=="));
+        assertEquals("hello, world.", decodeString("aGVsbG8sIHdvcmxkL g"));
+        assertEquals("hello, world.", decodeString("aGVsbG8sIHdvcmxkL g =="));
+        assertEquals("hello, world.", decodeString("aGVsbG8sIHdvcmxkL g "));
+        assertEquals("hello, world.", decodeString("aGVsbG8sIHdvcmxkL g = = "));
+        assertEquals("hello, world.", decodeString("aGVsbG8sIHdvcmxkL g   "));
+    }
+
+    private static final byte[] BYTES = { (byte) 0xff, (byte) 0xee, (byte) 0xdd,
+                                          (byte) 0xcc, (byte) 0xbb, (byte) 0xaa,
+                                          (byte) 0x99, (byte) 0x88, (byte) 0x77 };
+
+    public void testBinaryDecode() throws Exception {
+        assertEquals(BYTES, 0, Base64.decode("", 0));
+        assertEquals(BYTES, 1, Base64.decode("/w==", 0));
+        assertEquals(BYTES, 2, Base64.decode("/+4=", 0));
+        assertEquals(BYTES, 3, Base64.decode("/+7d", 0));
+        assertEquals(BYTES, 4, Base64.decode("/+7dzA==", 0));
+        assertEquals(BYTES, 5, Base64.decode("/+7dzLs=", 0));
+        assertEquals(BYTES, 6, Base64.decode("/+7dzLuq", 0));
+        assertEquals(BYTES, 7, Base64.decode("/+7dzLuqmQ==", 0));
+        assertEquals(BYTES, 8, Base64.decode("/+7dzLuqmYg=", 0));
+    }
+
+    public void testWebSafe() throws Exception {
+        assertEquals(BYTES, 0, Base64.decode("", Base64.WEB_SAFE));
+        assertEquals(BYTES, 1, Base64.decode("_w==", Base64.WEB_SAFE));
+        assertEquals(BYTES, 2, Base64.decode("_-4=", Base64.WEB_SAFE));
+        assertEquals(BYTES, 3, Base64.decode("_-7d", Base64.WEB_SAFE));
+        assertEquals(BYTES, 4, Base64.decode("_-7dzA==", Base64.WEB_SAFE));
+        assertEquals(BYTES, 5, Base64.decode("_-7dzLs=", Base64.WEB_SAFE));
+        assertEquals(BYTES, 6, Base64.decode("_-7dzLuq", Base64.WEB_SAFE));
+        assertEquals(BYTES, 7, Base64.decode("_-7dzLuqmQ==", Base64.WEB_SAFE));
+        assertEquals(BYTES, 8, Base64.decode("_-7dzLuqmYg=", Base64.WEB_SAFE));
+
+        assertEquals("", Base64.encodeString(BYTES, 0, 0, Base64.WEB_SAFE));
+        assertEquals("_w==\n", Base64.encodeString(BYTES, 0, 1, Base64.WEB_SAFE));
+        assertEquals("_-4=\n", Base64.encodeString(BYTES, 0, 2, Base64.WEB_SAFE));
+        assertEquals("_-7d\n", Base64.encodeString(BYTES, 0, 3, Base64.WEB_SAFE));
+        assertEquals("_-7dzA==\n", Base64.encodeString(BYTES, 0, 4, Base64.WEB_SAFE));
+        assertEquals("_-7dzLs=\n", Base64.encodeString(BYTES, 0, 5, Base64.WEB_SAFE));
+        assertEquals("_-7dzLuq\n", Base64.encodeString(BYTES, 0, 6, Base64.WEB_SAFE));
+        assertEquals("_-7dzLuqmQ==\n", Base64.encodeString(BYTES, 0, 7, Base64.WEB_SAFE));
+        assertEquals("_-7dzLuqmYg=\n", Base64.encodeString(BYTES, 0, 8, Base64.WEB_SAFE));
+    }
+
+    public void testFlags() throws Exception {
+        assertEquals("YQ==\n",       encodeString("a", 0));
+        assertEquals("YQ==",         encodeString("a", Base64.NO_WRAP));
+        assertEquals("YQ\n",         encodeString("a", Base64.NO_PADDING));
+        assertEquals("YQ",           encodeString("a", Base64.NO_PADDING | Base64.NO_WRAP));
+        assertEquals("YQ==\r\n",     encodeString("a", Base64.CRLF));
+        assertEquals("YQ\r\n",       encodeString("a", Base64.CRLF | Base64.NO_PADDING));
+
+        assertEquals("YWI=\n",       encodeString("ab", 0));
+        assertEquals("YWI=",         encodeString("ab", Base64.NO_WRAP));
+        assertEquals("YWI\n",        encodeString("ab", Base64.NO_PADDING));
+        assertEquals("YWI",          encodeString("ab", Base64.NO_PADDING | Base64.NO_WRAP));
+        assertEquals("YWI=\r\n",     encodeString("ab", Base64.CRLF));
+        assertEquals("YWI\r\n",      encodeString("ab", Base64.CRLF | Base64.NO_PADDING));
+
+        assertEquals("YWJj\n",       encodeString("abc", 0));
+        assertEquals("YWJj",         encodeString("abc", Base64.NO_WRAP));
+        assertEquals("YWJj\n",       encodeString("abc", Base64.NO_PADDING));
+        assertEquals("YWJj",         encodeString("abc", Base64.NO_PADDING | Base64.NO_WRAP));
+        assertEquals("YWJj\r\n",     encodeString("abc", Base64.CRLF));
+        assertEquals("YWJj\r\n",     encodeString("abc", Base64.CRLF | Base64.NO_PADDING));
+
+        assertEquals("YWJjZA==\n",   encodeString("abcd", 0));
+        assertEquals("YWJjZA==",     encodeString("abcd", Base64.NO_WRAP));
+        assertEquals("YWJjZA\n",     encodeString("abcd", Base64.NO_PADDING));
+        assertEquals("YWJjZA",       encodeString("abcd", Base64.NO_PADDING | Base64.NO_WRAP));
+        assertEquals("YWJjZA==\r\n", encodeString("abcd", Base64.CRLF));
+        assertEquals("YWJjZA\r\n",   encodeString("abcd", Base64.CRLF | Base64.NO_PADDING));
+    }
+
+    public void testLineLength() throws Exception {
+        String in_56 = "abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcd";
+        String in_57 = in_56 + "e";
+        String in_58 = in_56 + "ef";
+        String in_59 = in_56 + "efg";
+        String in_60 = in_56 + "efgh";
+        String in_61 = in_56 + "efghi";
+
+        String prefix = "YWJjZGVmZ2hpamtsbW5vcHFyc3R1dnd4eXphYmNkZWZnaGlqa2xtbm9wcXJzdHV2d3h5emFi";
+        String out_56 = prefix + "Y2Q=\n";
+        String out_57 = prefix + "Y2Rl\n";
+        String out_58 = prefix + "Y2Rl\nZg==\n";
+        String out_59 = prefix + "Y2Rl\nZmc=\n";
+        String out_60 = prefix + "Y2Rl\nZmdo\n";
+        String out_61 = prefix + "Y2Rl\nZmdoaQ==\n";
+
+        // no newline for an empty input array.
+        assertEquals("", encodeString("", 0));
+
+        assertEquals(out_56, encodeString(in_56, 0));
+        assertEquals(out_57, encodeString(in_57, 0));
+        assertEquals(out_58, encodeString(in_58, 0));
+        assertEquals(out_59, encodeString(in_59, 0));
+        assertEquals(out_60, encodeString(in_60, 0));
+        assertEquals(out_61, encodeString(in_61, 0));
+
+        assertEquals(out_56.replaceAll("=", ""), encodeString(in_56, Base64.NO_PADDING));
+        assertEquals(out_57.replaceAll("=", ""), encodeString(in_57, Base64.NO_PADDING));
+        assertEquals(out_58.replaceAll("=", ""), encodeString(in_58, Base64.NO_PADDING));
+        assertEquals(out_59.replaceAll("=", ""), encodeString(in_59, Base64.NO_PADDING));
+        assertEquals(out_60.replaceAll("=", ""), encodeString(in_60, Base64.NO_PADDING));
+        assertEquals(out_61.replaceAll("=", ""), encodeString(in_61, Base64.NO_PADDING));
+
+        assertEquals(out_56.replaceAll("\n", ""), encodeString(in_56, Base64.NO_WRAP));
+        assertEquals(out_57.replaceAll("\n", ""), encodeString(in_57, Base64.NO_WRAP));
+        assertEquals(out_58.replaceAll("\n", ""), encodeString(in_58, Base64.NO_WRAP));
+        assertEquals(out_59.replaceAll("\n", ""), encodeString(in_59, Base64.NO_WRAP));
+        assertEquals(out_60.replaceAll("\n", ""), encodeString(in_60, Base64.NO_WRAP));
+        assertEquals(out_61.replaceAll("\n", ""), encodeString(in_61, Base64.NO_WRAP));
+    }
+}