| 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 | private byte[] from; |
| 14 | private byte[] to; |
| 15 | |
| 16 | private byte[] source; |
| 17 | private int spos; |
| 18 | private int slen; |
| 19 | |
| 20 | /** |
| 21 | * Create a {@link ReplaceInputStream} that will replace <tt>from</tt> with |
| 22 | * <tt>to</tt>. |
| 23 | * |
| 24 | * @param in |
| 25 | * the under-laying {@link InputStream} |
| 26 | * @param from |
| 27 | * the {@link String} to replace |
| 28 | * @param to |
| 29 | * the {@link String} to replace with |
| 30 | */ |
| 31 | public ReplaceInputStream(InputStream in, String from, String to) { |
| 32 | this(in, StreamUtils.bytes(from), StreamUtils.bytes(to)); |
| 33 | } |
| 34 | |
| 35 | /** |
| 36 | * Create a {@link ReplaceInputStream} that will replace <tt>from</tt> with |
| 37 | * <tt>to</tt>. |
| 38 | * |
| 39 | * @param in |
| 40 | * the under-laying {@link InputStream} |
| 41 | * @param from |
| 42 | * the value to replace |
| 43 | * @param to |
| 44 | * the value to replace with |
| 45 | */ |
| 46 | public ReplaceInputStream(InputStream in, byte[] from, byte[] to) { |
| 47 | super(in); |
| 48 | this.from = from; |
| 49 | this.to = to; |
| 50 | |
| 51 | source = new byte[4096]; |
| 52 | spos = 0; |
| 53 | slen = 0; |
| 54 | } |
| 55 | |
| 56 | @Override |
| 57 | protected int read(InputStream in, byte[] buffer) throws IOException { |
| 58 | if (buffer.length < to.length || source.length < to.length * 2) { |
| 59 | throw new IOException( |
| 60 | "An underlaying buffer is too small for this replace value"); |
| 61 | } |
| 62 | |
| 63 | if (spos >= slen) { |
| 64 | spos = 0; |
| 65 | slen = in.read(source); |
| 66 | } |
| 67 | |
| 68 | // Note: very simple, not efficient implementation, sorry. |
| 69 | int count = 0; |
| 70 | while (spos < slen && count < buffer.length - to.length) { |
| 71 | if (from.length > 0 |
| 72 | && StreamUtils.startsWith(from, source, spos, slen)) { |
| 73 | System.arraycopy(to, 0, buffer, spos, to.length); |
| 74 | count += to.length; |
| 75 | spos += from.length; |
| 76 | } else { |
| 77 | buffer[count++] = source[spos++]; |
| 78 | } |
| 79 | } |
| 80 | |
| 81 | return count; |
| 82 | } |
| 83 | } |