void decode()

in bijection-core/src/main/java/com/twitter/bijection/codec/Base64.java [427:483]
47 lines of code
14 McCabe index (conditional complexity)

    void decode(final byte[] in, int inPos, final int inAvail, final BaseNCodec.Context context) {
        if (context.eof) {
            return;
        }
        if (inAvail < 0) {
            context.eof = true;
        }
        for (int i = 0; i < inAvail; i++) {
            final byte[] buffer = ensureBufferSize(decodeSize, context);
            final byte b = in[inPos++];
            if (b == PAD) {
                // We're done.
                context.eof = true;
                break;
            } else {
                if (b >= 0 && b < DECODE_TABLE.length) {
                    final int result = DECODE_TABLE[b];
                    if (result >= 0) {
                        context.modulus = (context.modulus+1) % BYTES_PER_ENCODED_BLOCK;
                        context.ibitWorkArea = (context.ibitWorkArea << BITS_PER_ENCODED_BYTE) + result;
                        if (context.modulus == 0) {
                            buffer[context.pos++] = (byte) ((context.ibitWorkArea >> 16) & MASK_8BITS);
                            buffer[context.pos++] = (byte) ((context.ibitWorkArea >> 8) & MASK_8BITS);
                            buffer[context.pos++] = (byte) (context.ibitWorkArea & MASK_8BITS);
                        }
                    }
                }
            }
        }

        // Two forms of EOF as far as base64 decoder is concerned: actual
        // EOF (-1) and first time '=' character is encountered in stream.
        // This approach makes the '=' padding characters completely optional.
        if (context.eof && context.modulus != 0) {
            final byte[] buffer = ensureBufferSize(decodeSize, context);

            // We have some spare bits remaining
            // Output all whole multiples of 8 bits and ignore the rest
            switch (context.modulus) {
//              case 0 : // impossible, as excluded above
                case 1 : // 6 bits - ignore entirely
                    // TODO not currently tested; perhaps it is impossible?
                    break;
                case 2 : // 12 bits = 8 + 4
                    context.ibitWorkArea = context.ibitWorkArea >> 4; // dump the extra 4 bits
                    buffer[context.pos++] = (byte) ((context.ibitWorkArea) & MASK_8BITS);
                    break;
                case 3 : // 18 bits = 8 + 8 + 2
                    context.ibitWorkArea = context.ibitWorkArea >> 2; // dump 2 bits
                    buffer[context.pos++] = (byte) ((context.ibitWorkArea >> 8) & MASK_8BITS);
                    buffer[context.pos++] = (byte) ((context.ibitWorkArea) & MASK_8BITS);
                    break;
                default:
                    throw new IllegalStateException("Impossible modulus "+context.modulus);
            }
        }
    }