add a Base64 implementation to the API

b/1413917 - RFE: Base64 utility class
Change-Id: I11697859e1f78f596b92d2e03a49ed1be04ae42d

3 files changed, 1028 insertions, 0 deletions

diff --git a/core/java/android/util/base64/Base64.java b/core/java/android/util/base64/Base64.java
new file mode 100644
index 0000000..088de9f
--- /dev/null
+++ b/core/java/android/util/base64/Base64.java
@@ -0,0 +1,706 @@
+/*
+ * 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 android.util.base64;
+
+/**
+ * Utilities for encoding and decoding the Base64 encoding.  See RFCs
+ * 2045 and 3548.
+ */
+public class Base64 {
+    /**
+     * Default values for encoder/decoder flags.
+     */
+    public static final int DEFAULT = 0;
+
+    /**
+     * 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.  Has no effect if {@code NO_WRAP} is
+     * specified as well.  
+     */
+    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;
+
+    /**
+     * Flag to pass to Base64OutputStream to indicate that it should
+     * not close the output stream it is wrapping when it itself is
+     * closed.
+     */
+    public static final int NO_CLOSE = 16;
+
+    //  --------------------------------------------------------
+    //  decoding
+    //  --------------------------------------------------------
+
+    /**
+     * 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.
+     *               Pass {@code DEFAULT} 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.
+     *               Pass {@code DEFAULT} 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.
+     *               Pass {@code DEFAULT} to decode standard Base64.
+     *
+     * @throws IllegalArgumentException if the input contains
+     * incorrect padding
+     */
+    public static byte[] decode(byte[] input, int offset, int len, int flags) {
+        // Allocate space for the most data the input could represent.
+        // (It could contain less if it contains whitespace, etc.)
+        DecoderState state = new DecoderState(flags, new byte[len*3/4]);
+
+        if (!decodeInternal(input, offset, len, state, true)) {
+            throw new IllegalArgumentException("bad base-64");
+        }
+
+        // Maybe we got lucky and allocated exactly enough output space.
+        if (state.op == state.output.length) {
+            return state.output;
+        }
+
+        // Need to shorten the array, so allocate a new one of the
+        // right size and copy.
+        byte[] temp = new byte[state.op];
+        System.arraycopy(state.output, 0, temp, 0, state.op);
+        return temp;
+    }
+
+    /* package */ static class DecoderState {
+        public byte[] output;
+        public int op;
+
+        public int state;   // state number (0 to 6)
+        public int value;
+
+        final public int[] alphabet;
+
+        public DecoderState(int flags, byte[] output) {
+            this.output = output;
+
+            alphabet = ((flags & WEB_SAFE) == 0) ? DECODE : DECODE_WEBSAFE;
+            state = 0;
+            value = 0;
+        }
+    }
+
+    /**
+     * Decode another block of input data.
+     *
+     * @param dstate a DecoderState object whose (caller-provided)
+     *        output array is big enough to hold all the decoded data.
+     *        On return, dstate.op will be set to the length of the
+     *        decoded data.
+     * @param finish true if this is the final call to decodeInternal
+     *        with the given DecoderState object.  Will finalize the
+     *        decoder state and include any final bytes in the output.
+     *
+     * @return true if the state machine is still healthy.  false if
+     *         bad base-64 data has been detected in the input stream.
+     */
+
+    /* package */ static boolean decodeInternal(
+        byte[] input, int offset, int len, final DecoderState dstate, boolean finish) {
+        if (dstate.state == 6) return false;
+
+        int state = dstate.state;
+        int value = dstate.value;
+        final int[] decode = dstate.alphabet;
+        final byte[] output = dstate.output;
+        int op = 0;
+
+        int p = offset;
+        len += offset;
+
+        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.
+            // State 6 is the error state; an error has been detected
+            // in the input and no future input can "fix" it.
+
+            int d = decode[input[p++] & 0xff];
+
+            switch (state) {
+                case 0:
+                    if (d >= 0) {
+                        value = d;
+                        ++state;
+                    } else if (d != SKIP) {
+                        dstate.state = 6;
+                        return false;
+                    }
+                    break;
+
+                case 1:
+                    if (d >= 0) {
+                        value = (value << 6) | d;
+                        ++state;
+                    } else if (d != SKIP) {
+                        dstate.state = 6;
+                        return false;
+                    }
+                    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) {
+                        dstate.state = 6;
+                        return false;
+                    }
+                    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) {
+                        dstate.state = 6;
+                        return false;
+                    }
+                    break;
+
+                case 4:
+                    if (d == EQUALS) {
+                        ++state;
+                    } else if (d != SKIP) {
+                        dstate.state = 6;
+                        return false;
+                    }
+                    break;
+
+                case 5:
+                    if (d != SKIP) {
+                        dstate.state = 6;
+                        return false;
+                    }
+                    break;
+            }
+        }
+
+        if (!finish) {
+            // We're out of input, but a future call could provide
+            // more.  Return the output we've produced on this call
+            // and save the current state of the state machine.
+            dstate.state = state;
+            dstate.value = value;
+            dstate.op = op;
+            return true;
+        }
+
+        // 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.
+                dstate.state = 6;
+                return false;
+            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.
+                dstate.state = 6;
+                return false;
+            case 5:
+                // Read all the padding '='s we expected and no more.
+                // Fine.
+                break;
+        }
+
+        dstate.op = op;
+        return true;
+    }
+
+    //  --------------------------------------------------------
+    //  encoding
+    //  --------------------------------------------------------
+
+    /**
+     * 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 {@code DEFAULT} results in output that
+     *               adheres to RFC 2045.
+     */
+    public static String encodeToString(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 {@code DEFAULT} results in output that
+     *               adheres to RFC 2045.
+     */
+    public static String encodeToString(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 {@code DEFAULT} 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 {@code DEFAULT} results in output that
+     *               adheres to RFC 2045.
+     */
+    public static byte[] encode(byte[] input, int offset, int len, int flags) {
+        EncoderState state = new EncoderState(flags, null);
+
+        // 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 (state.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 (state.do_newline && len > 0) {
+            output_len += (((len-1) / (3 * LINE_GROUPS)) + 1) * (state.do_cr ? 2 : 1);
+        }
+
+        state.output = new byte[output_len];
+        encodeInternal(input, offset, len, state, true);
+
+        assert state.op == output_len;
+
+        return state.output;
+    }
+
+    /* package */ static class EncoderState {
+        public byte[] output;
+        public int op;
+
+        final public byte[] tail;
+        public int tailLen;
+        public int count;
+
+        final public boolean do_padding;
+        final public boolean do_newline;
+        final public boolean do_cr;
+        final public byte[] alphabet;
+
+        public EncoderState(int flags, byte[] output) {
+            this.output = output;
+
+            do_padding = (flags & NO_PADDING) == 0;
+            do_newline = (flags & NO_WRAP) == 0;
+            do_cr = (flags & CRLF) != 0;
+            alphabet = ((flags & WEB_SAFE) == 0) ? ENCODE : ENCODE_WEBSAFE;
+
+            tail = new byte[2];
+            tailLen = 0;
+
+            count = do_newline ? LINE_GROUPS : -1;
+        }
+    }
+
+    /**
+     * Encode another block of input data.
+     *
+     * @param estate an EncoderState object whose (caller-provided)
+     *        output array is big enough to hold all the encoded data.
+     *        On return, estate.op will be set to the length of the
+     *        encoded data.
+     * @param finish true if this is the final call to encodeInternal
+     *        with the given EncoderState object.  Will finalize the
+     *        encoder state and include any final bytes in the output.
+     */
+    static void encodeInternal(byte[] input, int offset, int len,
+                               final EncoderState estate, boolean finish) {
+        final boolean do_cr = estate.do_cr;
+        final boolean do_newline = estate.do_newline;
+        final boolean do_padding = estate.do_padding;
+        final byte[] output = estate.output;
+
+        int op = 0;
+
+        int p = offset;
+        len += offset;
+        int v = -1;
+        int count = estate.count;
+
+        // First we need to concatenate the tail of the previous call
+        // with any input bytes available now and see if we can empty
+        // the tail.
+
+        switch (estate.tailLen) {
+            case 0:
+                // There was no tail.
+                break;
+
+            case 1:
+                if (p+2 <= len) {
+                    // A 1-byte tail with at least 2 bytes of
+                    // input available now.
+                    v = ((estate.tail[0] & 0xff) << 16) |
+                        ((input[p++] & 0xff) << 8) |
+                        (input[p++] & 0xff);
+                    estate.tailLen = 0;
+                };
+                break;
+
+            case 2:
+                if (p+1 <= len) {
+                    // A 2-byte tail with at least 1 byte of input.
+                    v = ((estate.tail[0] & 0xff) << 16) |
+                        ((estate.tail[1] & 0xff) << 8) |
+                        (input[p++] & 0xff);
+                    estate.tailLen = 0;
+                }
+                break;
+        }
+
+        if (v != -1) {
+            output[op++] = estate.alphabet[(v >> 18) & 0x3f];
+            output[op++] = estate.alphabet[(v >> 12) & 0x3f];
+            output[op++] = estate.alphabet[(v >> 6) & 0x3f];
+            output[op++] = estate.alphabet[v & 0x3f];
+            if (--count == 0) {
+                if (do_cr) output[op++] = '\r';
+                output[op++] = '\n';
+                count = LINE_GROUPS;
+            }
+        }
+
+        // At this point either there is no tail, or there are fewer
+        // than 3 bytes of input available.
+
+        // The main loop, turning 3 input bytes into 4 output bytes on
+        // each iteration.
+        while (p+3 <= len) {
+            v = ((input[p++] & 0xff) << 16) |
+                ((input[p++] & 0xff) << 8) |
+                (input[p++] & 0xff);
+            output[op++] = estate.alphabet[(v >> 18) & 0x3f];
+            output[op++] = estate.alphabet[(v >> 12) & 0x3f];
+            output[op++] = estate.alphabet[(v >> 6) & 0x3f];
+            output[op++] = estate.alphabet[v & 0x3f];
+            if (--count == 0) {
+                if (do_cr) output[op++] = '\r';
+                output[op++] = '\n';
+                count = LINE_GROUPS;
+            }
+        }
+
+        if (finish) {
+            // Finish up the tail of the input.  Note that we need to
+            // consume any bytes in estate.tail before any bytes
+            // remaining in input; there should be at most two bytes
+            // total.
+
+            if (p-estate.tailLen == len-1) {
+                int t = 0;
+                v = ((estate.tailLen > 0 ? estate.tail[t++] : input[p++]) & 0xff) << 4;
+                estate.tailLen -= t;
+                output[op++] = estate.alphabet[(v >> 6) & 0x3f];
+                output[op++] = estate.alphabet[v & 0x3f];
+                if (do_padding) {
+                    output[op++] = '=';
+                    output[op++] = '=';
+                }
+                if (do_newline) {
+                    if (do_cr) output[op++] = '\r';
+                    output[op++] = '\n';
+                }
+            } else if (p-estate.tailLen == len-2) {
+                int t = 0;
+                v = (((estate.tailLen > 1 ? estate.tail[t++] : input[p++]) & 0xff) << 10) |
+                    (((estate.tailLen > 0 ? estate.tail[t++] : input[p++]) & 0xff) << 2);
+                estate.tailLen -= t;
+                output[op++] = estate.alphabet[(v >> 12) & 0x3f];
+                output[op++] = estate.alphabet[(v >> 6) & 0x3f];
+                output[op++] = estate.alphabet[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 estate.tailLen == 0;
+            assert p == len;
+        } else {
+            // Save the leftovers in tail to be consumed on the next
+            // call to encodeInternal.
+
+            if (p == len-1) {
+                estate.tail[estate.tailLen++] = input[p];
+            } else if (p == len-2) {
+                estate.tail[estate.tailLen++] = input[p];
+                estate.tail[estate.tailLen++] = input[p+1];
+            }
+        }
+
+        estate.op = op;
+        estate.count = count;
+    }
+
+    private Base64() { }   // don't instantiate
+}
diff --git a/core/java/android/util/base64/Base64InputStream.java b/core/java/android/util/base64/Base64InputStream.java
new file mode 100644
index 0000000..c0c1636
--- /dev/null
+++ b/core/java/android/util/base64/Base64InputStream.java
@@ -0,0 +1,169 @@
+/*
+ * 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 android.util.base64;
+
+import java.io.FilterInputStream;
+import java.io.IOException;
+import java.io.InputStream;
+
+/**
+ * An OutputStream that does either Base64 encoding or decoding on the
+ * data written to it, writing the resulting data to another
+ * OutputStream.
+ */
+public class Base64InputStream extends FilterInputStream {
+    private final boolean encode;
+    private final Base64.EncoderState estate;
+    private final Base64.DecoderState dstate;
+
+    private static byte[] EMPTY = new byte[0];
+
+    private static final int BUFFER_SIZE = 2048;
+    private boolean eof;
+    private byte[] inputBuffer;
+    private byte[] outputBuffer;
+    private int outputStart;
+    private int outputEnd;
+
+    /**
+     * An InputStream that performs Base64 decoding on the data read
+     * from the wrapped stream.
+     *
+     * @param in the InputStream to read the source data from
+     * @param flags bit flags for controlling the decoder; see the
+     *        constants in {@link Base64}
+     */
+    public Base64InputStream(InputStream in, int flags) {
+        this(in, flags, false);
+    }
+
+    /**
+     * Performs Base64 encoding or decoding on the data read from the
+     * wrapped InputStream.
+     *
+     * @param in the InputStream to read the source data from
+     * @param flags bit flags for controlling the decoder; see the
+     *        constants in {@link Base64}
+     * @param encode true to encode, false to decode
+     */
+    public Base64InputStream(InputStream in, int flags, boolean encode) {
+        super(in);
+        this.encode = encode;
+        eof = false;
+        inputBuffer = new byte[BUFFER_SIZE];
+        if (encode) {
+            // len*8/5+10 is an overestimate of the most bytes the
+            // encoder can produce for len bytes of input.
+            outputBuffer = new byte[BUFFER_SIZE * 8/5 + 10];
+            estate = new Base64.EncoderState(flags, outputBuffer);
+            dstate = null;
+        } else {
+            // len*3/4+10 is an overestimate of the most bytes the
+            // decoder can produce for len bytes of input.
+            outputBuffer = new byte[BUFFER_SIZE * 3/4 + 10];
+            estate = null;
+            dstate = new Base64.DecoderState(flags, outputBuffer);
+        }
+        outputStart = 0;
+        outputEnd = 0;
+    }
+
+    public boolean markSupported() {
+        return false;
+    }
+
+    public void mark(int readlimit) {
+        throw new UnsupportedOperationException();
+    }
+
+    public void reset() {
+        throw new UnsupportedOperationException();
+    }
+
+    public void close() throws IOException {
+        in.close();
+        inputBuffer = null;
+    }
+
+    public int available() {
+        return outputEnd - outputStart;
+    }
+
+    public long skip(long n) throws IOException {
+        if (outputStart >= outputEnd) {
+            refill();
+        }
+        if (outputStart >= outputEnd) {
+            return 0;
+        }
+        long bytes = Math.min(n, outputEnd-outputStart);
+        outputStart += bytes;
+        return bytes;
+    }
+
+    public int read() throws IOException {
+        if (outputStart >= outputEnd) {
+            refill();
+        }
+        if (outputStart >= outputEnd) {
+            return -1;
+        } else {
+            return outputBuffer[outputStart++];
+        }
+    }
+
+    public int read(byte[] b, int off, int len) throws IOException {
+        if (outputStart >= outputEnd) {
+            refill();
+        }
+        if (outputStart >= outputEnd) {
+            return -1;
+        }
+        int bytes = Math.min(len, outputEnd-outputStart);
+        System.arraycopy(outputBuffer, outputStart, b, off, bytes);
+        outputStart += bytes;
+        return bytes;
+    }
+
+    /**
+     * Read data from the input stream into inputBuffer, then
+     * decode/encode it into the empty outputBuffer, and reset the
+     * outputStart and outputEnd pointers.
+     */
+    private void refill() throws IOException {
+        if (eof) return;
+        int bytesRead = in.read(inputBuffer);
+        if (encode) {
+            if (bytesRead == -1) {
+                eof = true;
+                Base64.encodeInternal(EMPTY, 0, 0, estate, true);
+            } else {
+                Base64.encodeInternal(inputBuffer, 0, bytesRead, estate, false);
+            }
+            outputEnd = estate.op;
+        } else {
+            if (bytesRead == -1) {
+                eof = true;
+                Base64.decodeInternal(EMPTY, 0, 0, dstate, true);
+            } else {
+                Base64.decodeInternal(inputBuffer, 0, bytesRead, dstate, false);
+            }
+            outputEnd = dstate.op;
+        }
+        outputStart = 0;
+    }
+}
diff --git a/core/java/android/util/base64/Base64OutputStream.java b/core/java/android/util/base64/Base64OutputStream.java
new file mode 100644
index 0000000..126bde4
--- /dev/null
+++ b/core/java/android/util/base64/Base64OutputStream.java
@@ -0,0 +1,153 @@
+/*
+ * 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 android.util.base64;
+
+import java.io.FilterOutputStream;
+import java.io.IOException;
+import java.io.OutputStream;
+
+/**
+ * An OutputStream that does either Base64 encoding or decoding on the
+ * data written to it, writing the resulting data to another
+ * OutputStream.
+ */
+public class Base64OutputStream extends FilterOutputStream {
+    private final boolean encode;
+    private final Base64.EncoderState estate;
+    private final Base64.DecoderState dstate;
+    private final int flags;
+
+    private byte[] buffer = null;
+    private int bpos = 0;
+
+    private static byte[] EMPTY = new byte[0];
+
+    /**
+     * Performs Base64 encoding on the data written to the stream,
+     * writing the encoded data to another OutputStream.
+     *
+     * @param out the OutputStream to write the encoded data to
+     * @param flags bit flags for controlling the encoder; see the
+     *        constants in {@link Base64}
+     */
+    public Base64OutputStream(OutputStream out, int flags) {
+        this(out, flags, true);
+    }
+
+    /**
+     * Performs Base64 encoding or decoding on the data written to the
+     * stream, writing the encoded/decoded data to another
+     * OutputStream.
+     *
+     * @param out the OutputStream to write the encoded data to
+     * @param flags bit flags for controlling the encoder; see the
+     *        constants in {@link Base64}
+     * @param encode true to encode, false to decode
+     */
+    public Base64OutputStream(OutputStream out, int flags, boolean encode) {
+        super(out);
+        this.flags = flags;
+        this.encode = encode;
+        if (encode) {
+            estate = new Base64.EncoderState(flags, null);
+            dstate = null;
+        } else {
+            estate = null;
+            dstate = new Base64.DecoderState(flags, null);
+        }
+    }
+
+    public void write(int b) throws IOException {
+        // To avoid invoking the encoder/decoder routines for single
+        // bytes, we buffer up calls to write(int) in an internal
+        // byte array to transform them into writes of decently-sized
+        // arrays.
+
+        if (buffer == null) {
+            buffer = new byte[1024];
+        }
+        if (bpos >= buffer.length) {
+            // internal buffer full; write it out.
+            internalWrite(buffer, 0, bpos, false);
+            bpos = 0;
+        }
+        buffer[bpos++] = (byte) b;
+    }
+
+    /**
+     * Flush any buffered data from calls to write(int).  Needed
+     * before doing a write(byte[], int, int) or a close().
+     */
+    private void flushBuffer() throws IOException {
+        if (bpos > 0) {
+            internalWrite(buffer, 0, bpos, false);
+            bpos = 0;
+        }
+    }
+
+    public void write(byte[] b, int off, int len) throws IOException {
+        if (len <= 0) return;
+        flushBuffer();
+        internalWrite(b, off, len, false);
+    }
+
+    public void close() throws IOException {
+        flushBuffer();
+        internalWrite(EMPTY, 0, 0, true);
+        if ((flags & Base64.NO_CLOSE) == 0) {
+            out.close();
+        } else {
+            out.flush();
+        }
+    }
+
+    /**
+     * Write the given bytes to the encoder/decoder.
+     *
+     * @param finish true if this is the last batch of input, to cause
+     *        encoder/decoder state to be finalized.
+     */
+    private void internalWrite(byte[] b, int off, int len, boolean finish) throws IOException {
+        if (encode) {
+            // len*8/5+10 is an overestimate of the most bytes the
+            // encoder can produce for len bytes of input.
+            estate.output = embiggen(estate.output, len*8/5+10);
+            Base64.encodeInternal(b, off, len, estate, finish);
+            out.write(estate.output, 0, estate.op);
+        } else {
+            // len*3/4+10 is an overestimate of the most bytes the
+            // decoder can produce for len bytes of input.
+            dstate.output = embiggen(dstate.output, len*3/4+10);
+            if (!Base64.decodeInternal(b, off, len, dstate, finish)) {
+                throw new IOException("bad base-64");
+            }
+            out.write(dstate.output, 0, dstate.op);
+        }
+    }
+
+    /**
+     * If b.length is at least len, return b.  Otherwise return a new
+     * byte array of length len.
+     */
+    private byte[] embiggen(byte[] b, int len) {
+        if (b == null || b.length < len) {
+            return new byte[len];
+        } else {
+            return b;
+        }
+    }
+}