streams/ReplaceInputStream.java

   1 package be.nikiroo.utils.streams;
   2
   3 import java.io.IOException;
   4 import java.io.InputStream;
   5
   6 import be.nikiroo.utils.StringUtils;
   7
   8 /**
   9  * This {@link InputStream} will change some of its content by replacing it with
  10  * something else.
  11  *
  12  * @author niki
  13  */
  14 public class ReplaceInputStream extends BufferedInputStream {
  15         /**
  16          * The minimum size of the internal buffer (could be more if at least one of
  17          * the 'FROM' bytes arrays is &gt; 2048 bytes &mdash; in that case the
  18          * buffer will be twice the largest size of the 'FROM' bytes arrays).
  19          * <p>
  20          * This is a different buffer than the one from the inherited class.
  21          */
  22         static private final int MIN_BUFFER_SIZE = 4096;
  23
  24         private byte[][] froms;
  25         private byte[][] tos;
  26         private int maxFromSize;
  27         private int maxToSize;
  28
  29         private byte[] source;
  30         private int spos;
  31         private int slen;
  32
  33         /**
  34          * Create a {@link ReplaceInputStream} that will replace <tt>from</tt> with
  35          * <tt>to</tt>.
  36          *
  37          * @param in
  38          *            the under-laying {@link InputStream}
  39          * @param from
  40          *            the {@link String} to replace
  41          * @param to
  42          *            the {@link String} to replace with
  43          */
  44         public ReplaceInputStream(InputStream in, String from, String to) {
  45                 this(in, StringUtils.getBytes(from), StringUtils.getBytes(to));
  46         }
  47
  48         /**
  49          * Create a {@link ReplaceInputStream} that will replace <tt>from</tt> with
  50          * <tt>to</tt>.
  51          *
  52          * @param in
  53          *            the under-laying {@link InputStream}
  54          * @param from
  55          *            the value to replace
  56          * @param to
  57          *            the value to replace with
  58          */
  59         public ReplaceInputStream(InputStream in, byte[] from, byte[] to) {
  60                 this(in, new byte[][] { from }, new byte[][] { to });
  61         }
  62
  63         /**
  64          * Create a {@link ReplaceInputStream} that will replace all <tt>froms</tt>
  65          * with <tt>tos</tt>.
  66          * <p>
  67          * Note that they will be replaced in order, and that for each <tt>from</tt>
  68          * a <tt>to</tt> must correspond.
  69          *
  70          * @param in
  71          *            the under-laying {@link InputStream}
  72          * @param froms
  73          *            the values to replace
  74          * @param tos
  75          *            the values to replace with
  76          */
  77         public ReplaceInputStream(InputStream in, String[] froms, String[] tos) {
  78                 this(in, StreamUtils.getBytes(froms), StreamUtils.getBytes(tos));
  79         }
  80
  81         /**
  82          * Create a {@link ReplaceInputStream} that will replace all <tt>froms</tt>
  83          * with <tt>tos</tt>.
  84          * <p>
  85          * Note that they will be replaced in order, and that for each <tt>from</tt>
  86          * a <tt>to</tt> must correspond.
  87          *
  88          * @param in
  89          *            the under-laying {@link InputStream}
  90          * @param froms
  91          *            the values to replace
  92          * @param tos
  93          *            the values to replace with
  94          */
  95         public ReplaceInputStream(InputStream in, byte[][] froms, byte[][] tos) {
  96                 super(in);
  97
  98                 if (froms.length != tos.length) {
  99                         throw new IllegalArgumentException(
 100                                         "For replacing, each FROM must have a corresponding TO");
 101                 }
 102
 103                 this.froms = froms;
 104                 this.tos = tos;
 105
 106                 maxFromSize = 0;
 107                 for (int i = 0; i < froms.length; i++) {
 108                         maxFromSize = Math.max(maxFromSize, froms[i].length);
 109                 }
 110
 111                 maxToSize = 0;
 112                 for (int i = 0; i < tos.length; i++) {
 113                         maxToSize = Math.max(maxToSize, tos[i].length);
 114                 }
 115
 116                 // We need at least maxFromSize so we can iterate and replace
 117                 source = new byte[Math.max(2 * Math.max(maxToSize, maxFromSize),
 118                                 MIN_BUFFER_SIZE)];
 119                 spos = 0;
 120                 slen = 0;
 121         }
 122
 123         @Override
 124         protected int read(InputStream in, byte[] buffer, int off, int len)
 125                         throws IOException {
 126                 if (len < maxToSize || source.length < maxToSize * 2) {
 127                         throw new IOException(
 128                                         "An underlaying buffer is too small for these replace values");
 129                 }
 130
 131                 // We need at least one byte of data to process
 132                 if (available() < Math.max(maxFromSize, 1) && !eof) {
 133                         spos = 0;
 134                         slen = in.read(source);
 135                 }
 136
 137                 // Note: very simple, not efficient implementation; sorry.
 138                 int count = 0;
 139                 while (spos < slen && count < len - maxToSize) {
 140                         boolean replaced = false;
 141                         for (int i = 0; i < froms.length; i++) {
 142                                 if (froms[i] != null && froms[i].length > 0
 143                                                 && StreamUtils.startsWith(froms[i], source, spos, slen)) {
 144                                         if (tos[i] != null && tos[i].length > 0) {
 145                                                 System.arraycopy(tos[i], 0, buffer, off + count,
 146                                                                 tos[i].length);
 147                                                 count += tos[i].length;
 148                                         }
 149
 150                                         spos += froms[i].length;
 151                                         replaced = true;
 152                                         break;
 153                                 }
 154                         }
 155
 156                         if (!replaced) {
 157                                 buffer[off + count++] = source[spos++];
 158                         }
 159                 }
 160
 161                 return count;
 162         }
 163 }