| 1 | package be.nikiroo.utils.streams; |
| 2 | |
| 3 | import java.io.IOException; |
| 4 | import java.io.InputStream; |
| 5 | |
| 6 | /** |
| 7 | * This {@link InputStream} can be separated into sub-streams (you can process |
| 8 | * it as a normal {@link InputStream} but, when it is spent, you can call |
| 9 | * {@link NextableInputStream#next()} on it to unlock new data). |
| 10 | * <p> |
| 11 | * The separation in sub-streams is done via {@link NextableInputStreamStep}. |
| 12 | * |
| 13 | * @author niki |
| 14 | */ |
| 15 | public class NextableInputStream extends BufferedInputStream { |
| 16 | private NextableInputStreamStep step; |
| 17 | private boolean started; |
| 18 | private boolean stopped; |
| 19 | |
| 20 | /** |
| 21 | * Create a new {@link NextableInputStream} that wraps the given |
| 22 | * {@link InputStream}. |
| 23 | * |
| 24 | * @param in |
| 25 | * the {@link InputStream} to wrap |
| 26 | * @param step |
| 27 | * how to separate it into sub-streams (can be NULL, but in that |
| 28 | * case it will behave as a normal {@link InputStream}) |
| 29 | */ |
| 30 | public NextableInputStream(InputStream in, NextableInputStreamStep step) { |
| 31 | super(in); |
| 32 | this.step = step; |
| 33 | } |
| 34 | |
| 35 | /** |
| 36 | * Create a new {@link NextableInputStream} that wraps the given bytes array |
| 37 | * as a data source. |
| 38 | * |
| 39 | * @param in |
| 40 | * the array to wrap, cannot be NULL |
| 41 | * @param step |
| 42 | * how to separate it into sub-streams (can be NULL, but in that |
| 43 | * case it will behave as a normal {@link InputStream}) |
| 44 | */ |
| 45 | public NextableInputStream(byte[] in, NextableInputStreamStep step) { |
| 46 | this(in, step, 0, in.length); |
| 47 | } |
| 48 | |
| 49 | /** |
| 50 | * Create a new {@link NextableInputStream} that wraps the given bytes array |
| 51 | * as a data source. |
| 52 | * |
| 53 | * @param in |
| 54 | * the array to wrap, cannot be NULL |
| 55 | * @param step |
| 56 | * how to separate it into sub-streams (can be NULL, but in that |
| 57 | * case it will behave as a normal {@link InputStream}) |
| 58 | * @param offset |
| 59 | * the offset to start the reading at |
| 60 | * @param length |
| 61 | * the number of bytes to take into account in the array, |
| 62 | * starting from the offset |
| 63 | * |
| 64 | * @throws NullPointerException |
| 65 | * if the array is NULL |
| 66 | * @throws IndexOutOfBoundsException |
| 67 | * if the offset and length do not correspond to the given array |
| 68 | */ |
| 69 | public NextableInputStream(byte[] in, NextableInputStreamStep step, |
| 70 | int offset, int length) { |
| 71 | super(in, offset, length); |
| 72 | this.step = step; |
| 73 | checkBuffer(true); |
| 74 | } |
| 75 | |
| 76 | /** |
| 77 | * Unblock the processing of the next sub-stream. |
| 78 | * <p> |
| 79 | * It can only be called when the "current" stream is spent (i.e., you must |
| 80 | * first process the stream until it is spent). |
| 81 | * <p> |
| 82 | * We consider that when the under-laying {@link InputStream} is also spent, |
| 83 | * we cannot have a next sub-stream (it will thus return FALSE). |
| 84 | * <p> |
| 85 | * {@link IOException}s can happen when we have no data available in the |
| 86 | * buffer; in that case, we fetch more data to know if we can have a next |
| 87 | * sub-stream or not. |
| 88 | * |
| 89 | * @return TRUE if we unblocked the next sub-stream, FALSE if not |
| 90 | * |
| 91 | * @throws IOException |
| 92 | * in case of I/O error or if the stream is closed |
| 93 | */ |
| 94 | public boolean next() throws IOException { |
| 95 | return next(false); |
| 96 | } |
| 97 | |
| 98 | /** |
| 99 | * Unblock the next sub-stream as would have done |
| 100 | * {@link NextableInputStream#next()}, but disable the sub-stream systems. |
| 101 | * <p> |
| 102 | * That is, the next stream, if any, will be the last one and will not be |
| 103 | * subject to the {@link NextableInputStreamStep}. |
| 104 | * |
| 105 | * @return TRUE if we unblocked the next sub-stream, FALSE if not |
| 106 | * |
| 107 | * @throws IOException |
| 108 | * in case of I/O error or if the stream is closed |
| 109 | */ |
| 110 | public boolean nextAll() throws IOException { |
| 111 | return next(true); |
| 112 | } |
| 113 | |
| 114 | /** |
| 115 | * Check if this stream is totally spent (no more data to read or to |
| 116 | * process). |
| 117 | * <p> |
| 118 | * Note: an empty stream that is still not started will return FALSE, as we |
| 119 | * don't know yet if it is empty. |
| 120 | * |
| 121 | * @return TRUE if it is |
| 122 | */ |
| 123 | @Override |
| 124 | public boolean eof() { |
| 125 | return super.eof(); |
| 126 | } |
| 127 | |
| 128 | /** |
| 129 | * Check if we still have some data in the buffer and, if not, fetch some. |
| 130 | * |
| 131 | * @return TRUE if we fetched some data, FALSE if there are still some in |
| 132 | * the buffer |
| 133 | * |
| 134 | * @throws IOException |
| 135 | * in case of I/O error |
| 136 | */ |
| 137 | @Override |
| 138 | protected boolean preRead() throws IOException { |
| 139 | if (!stopped) { |
| 140 | boolean bufferChanged = super.preRead(); |
| 141 | checkBuffer(true); |
| 142 | return bufferChanged; |
| 143 | } |
| 144 | |
| 145 | if (start >= stop) { |
| 146 | eof = true; |
| 147 | } |
| 148 | |
| 149 | return false; |
| 150 | } |
| 151 | |
| 152 | /** |
| 153 | * We have more data available in the buffer or we can fetch more. |
| 154 | * |
| 155 | * @return TRUE if it is the case, FALSE if not |
| 156 | */ |
| 157 | @Override |
| 158 | protected boolean hasMoreData() { |
| 159 | return started && super.hasMoreData(); |
| 160 | } |
| 161 | |
| 162 | /** |
| 163 | * Check that the buffer didn't overshot to the next item, and fix |
| 164 | * {@link NextableInputStream#stop} if needed. |
| 165 | * <p> |
| 166 | * If {@link NextableInputStream#stop} is fixed, |
| 167 | * {@link NextableInputStream#eof} and {@link NextableInputStream#stopped} |
| 168 | * are set to TRUE. |
| 169 | * |
| 170 | * @param newBuffer |
| 171 | * we changed the buffer, we need to clear some information in |
| 172 | * the {@link NextableInputStreamStep} |
| 173 | */ |
| 174 | private void checkBuffer(boolean newBuffer) { |
| 175 | if (step != null && stop > 0) { |
| 176 | if (newBuffer) { |
| 177 | step.clearBuffer(); |
| 178 | } |
| 179 | |
| 180 | int stopAt = step.stop(buffer, start, stop); |
| 181 | if (stopAt >= 0) { |
| 182 | stop = stopAt; |
| 183 | eof = true; |
| 184 | stopped = true; |
| 185 | } |
| 186 | } |
| 187 | } |
| 188 | |
| 189 | /** |
| 190 | * The implementation of {@link NextableInputStream#next()} and |
| 191 | * {@link NextableInputStream#nextAll()}. |
| 192 | * |
| 193 | * @param all |
| 194 | * TRUE for {@link NextableInputStream#nextAll()}, FALSE for |
| 195 | * {@link NextableInputStream#next()} |
| 196 | * |
| 197 | * @return TRUE if we unblocked the next sub-stream, FALSE if not |
| 198 | * |
| 199 | * @throws IOException |
| 200 | * in case of I/O error or if the stream is closed |
| 201 | */ |
| 202 | private boolean next(boolean all) throws IOException { |
| 203 | checkClose(); |
| 204 | |
| 205 | if (!started) { |
| 206 | // First call before being allowed to read |
| 207 | started = true; |
| 208 | |
| 209 | if (all) { |
| 210 | step = null; |
| 211 | } |
| 212 | |
| 213 | return true; |
| 214 | } |
| 215 | |
| 216 | if (step != null && !hasMoreData() && stopped) { |
| 217 | stop = step.getResumeLen(); |
| 218 | start += step.getResumeSkip(); |
| 219 | eof = false; |
| 220 | |
| 221 | if (all) { |
| 222 | step = null; |
| 223 | } |
| 224 | |
| 225 | if (!preRead()) { |
| 226 | checkBuffer(false); |
| 227 | } |
| 228 | |
| 229 | // consider that if EOF, there is no next |
| 230 | return hasMoreData(); |
| 231 | } |
| 232 | |
| 233 | return false; |
| 234 | } |
| 235 | } |