src/be/nikiroo/utils/streams/ReplaceInputStream.java

   1 package be.nikiroo.utils.streams;
   2
   3 import java.io.IOException;
   4 import java.io.InputStream;
   5
   6 /**
   7  * This {@link InputStream} will change some of its content by replacing it with
   8  * something else.
   9  *
  10  * @author niki
  11  */
  12 public class ReplaceInputStream extends BufferedInputStream {
  13         /**
  14          * The minimum size of the internal buffer (could be more if at least one of
  15          * the 'FROM' bytes arrays is &gt; 2048 bytes &mdash; in that case the
  16          * buffer will be twice the largest size of the 'FROM' bytes arrays).
  17          * <p>
  18          * This is a different buffer than the one from the inherited class.
  19          */
  20         static private final int MIN_BUFFER_SIZE = 4096;
  21
  22         private byte[][] froms;
  23         private byte[][] tos;
  24         private int maxFromSize;
  25         private int maxToSize;
  26
  27         private byte[] source;
  28         private int spos;
  29         private int slen;
  30
  31         /**
  32          * Create a {@link ReplaceInputStream} that will replace <tt>from</tt> with
  33          * <tt>to</tt>.
  34          *
  35          * @param in
  36          *            the under-laying {@link InputStream}
  37          * @param from
  38          *            the {@link String} to replace
  39          * @param to
  40          *            the {@link String} to replace with
  41          */
  42         public ReplaceInputStream(InputStream in, String from, String to) {
  43                 this(in, StreamUtils.bytes(from), StreamUtils.bytes(to));
  44         }
  45
  46         /**
  47          * Create a {@link ReplaceInputStream} that will replace <tt>from</tt> with
  48          * <tt>to</tt>.
  49          *
  50          * @param in
  51          *            the under-laying {@link InputStream}
  52          * @param from
  53          *            the value to replace
  54          * @param to
  55          *            the value to replace with
  56          */
  57         public ReplaceInputStream(InputStream in, byte[] from, byte[] to) {
  58                 this(in, new byte[][] { from }, new byte[][] { to });
  59         }
  60
  61         /**
  62          * Create a {@link ReplaceInputStream} that will replace all <tt>froms</tt>
  63          * with <tt>tos</tt>.
  64          * <p>
  65          * Note that they will be replaced in order, and that for each <tt>from</tt>
  66          * a <tt>to</tt> must correspond.
  67          *
  68          * @param in
  69          *            the under-laying {@link InputStream}
  70          * @param froms
  71          *            the values to replace
  72          * @param tos
  73          *            the values to replace with
  74          */
  75         public ReplaceInputStream(InputStream in, String[] froms, String[] tos) {
  76                 this(in, StreamUtils.bytes(froms), StreamUtils.bytes(tos));
  77         }
  78
  79         /**
  80          * Create a {@link ReplaceInputStream} that will replace all <tt>froms</tt>
  81          * with <tt>tos</tt>.
  82          * <p>
  83          * Note that they will be replaced in order, and that for each <tt>from</tt>
  84          * a <tt>to</tt> must correspond.
  85          *
  86          * @param in
  87          *            the under-laying {@link InputStream}
  88          * @param froms
  89          *            the values to replace
  90          * @param tos
  91          *            the values to replace with
  92          */
  93         public ReplaceInputStream(InputStream in, byte[][] froms, byte[][] tos) {
  94                 super(in);
  95
  96                 if (froms.length != tos.length) {
  97                         throw new IllegalArgumentException(
  98                                         "For replacing, each FROM must have a corresponding TO");
  99                 }
 100
 101                 this.froms = froms;
 102                 this.tos = tos;
 103
 104                 maxFromSize = 0;
 105                 for (int i = 0; i < froms.length; i++) {
 106                         maxFromSize = Math.max(maxFromSize, froms[i].length);
 107                 }
 108
 109                 maxToSize = 0;
 110                 for (int i = 0; i < tos.length; i++) {
 111                         maxToSize = Math.max(maxToSize, tos[i].length);
 112                 }
 113
 114                 // We need at least maxFromSize so we can iterate and replace
 115                 source = new byte[Math.max(2 * maxFromSize, MIN_BUFFER_SIZE)];
 116                 spos = 0;
 117                 slen = 0;
 118         }
 119
 120         @Override
 121         protected int read(InputStream in, byte[] buffer, int off, int len)
 122                         throws IOException {
 123                 if (len < maxToSize || source.length < maxToSize * 2) {
 124                         throw new IOException(
 125                                         "An underlaying buffer is too small for these replace values");
 126                 }
 127
 128                 // We need at least one byte of data to process
 129                 if (available() < Math.max(maxFromSize, 1) && !eof) {
 130                         spos = 0;
 131                         slen = in.read(source);
 132                 }
 133
 134                 // Note: very simple, not efficient implementation; sorry.
 135                 int count = 0;
 136                 while (spos < slen && count < len - maxToSize) {
 137                         boolean replaced = false;
 138                         for (int i = 0; i < froms.length; i++) {
 139                                 if (froms[i] != null && froms[i].length > 0
 140                                                 && StreamUtils.startsWith(froms[i], source, spos, slen)) {
 141                                         if (tos[i] != null && tos[i].length > 0) {
 142                                                 System.arraycopy(tos[i], 0, buffer, off + spos,
 143                                                                 tos[i].length);
 144                                                 count += tos[i].length;
 145                                         }
 146
 147                                         spos += froms[i].length;
 148                                         replaced = true;
 149                                         break;
 150                                 }
 151                         }
 152
 153                         if (!replaced) {
 154                                 buffer[off + count++] = source[spos++];
 155                         }
 156                 }
 157
 158                 return count;
 159         }
 160 }