X-Git-Url: http://source.jalview.org/gitweb/?p=jalview.git;a=blobdiff_plain;f=src2%2Fjavajs%2Fimg%2FCRCEncoder.java;fp=src2%2Fjavajs%2Fimg%2FCRCEncoder.java;h=77ed11eec139d943ad53d8c714a3fbefd58c0e8b;hp=0000000000000000000000000000000000000000;hb=665d2c2f4c1310e6985b93b7c2c8a8eec2fa9086;hpb=0e684f72690bd6532272a39ab6c188a27559fd09

diff --git a/src2/javajs/img/CRCEncoder.java b/src2/javajs/img/CRCEncoder.java
new file mode 100644
index 0000000..77ed11e
--- /dev/null
+++ b/src2/javajs/img/CRCEncoder.java
@@ -0,0 +1,110 @@
+package javajs.img;
+
+import java.util.zip.CRC32;
+
+
+import javajs.util.AU;
+
+abstract class CRCEncoder extends ImageEncoder {
+
+  protected int startPos, bytePos;
+  
+  private CRC32 crc;  
+  protected byte[] pngBytes;  
+  protected int dataLen;
+  private byte[] int2 = new byte[2];
+  private byte[] int4 = new byte[4];
+
+  CRCEncoder() {
+    pngBytes = new byte[250];
+    crc = new CRC32();
+  }
+
+  protected void setData(byte[] b, int pt) {
+    pngBytes = b;
+    dataLen = b.length;
+    startPos = bytePos = pt;
+  }
+
+  protected byte[] getBytes() {
+    return (dataLen == pngBytes.length ? pngBytes : AU.arrayCopyByte(
+        pngBytes, dataLen));
+  }
+
+  protected void writeCRC() {
+    crc.reset();
+    crc.update(pngBytes, startPos, bytePos - startPos);
+    writeInt4((int) crc.getValue());
+  }
+
+  /**
+   * Write a two-byte integer into the pngBytes array at a given position.
+   *
+   * @param n The integer to be written into pngBytes.
+   */
+  protected void writeInt2(int n) {
+    int2[0] = (byte) ((n >> 8) & 0xff);
+    int2[1] = (byte) (n & 0xff);
+    writeBytes(int2);
+  }
+
+  /**
+   * Write a four-byte integer into the pngBytes array at a given position.
+   *
+   * @param n The integer to be written into pngBytes.
+   */
+  protected void writeInt4(int n) {
+    getInt4(n, int4);
+    writeBytes(int4);
+  }
+
+  protected static void getInt4(int n, byte[] int4) {
+    int4[0] = (byte) ((n >> 24) & 0xff);
+    int4[1] = (byte) ((n >> 16) & 0xff);
+    int4[2] = (byte) ((n >> 8) & 0xff);
+    int4[3] = (byte) (n & 0xff);
+  }
+
+  /**
+   * Write a single byte into the pngBytes array at a given position.
+   *
+   * @param b The byte to be written into pngBytes.
+   */
+  protected void writeByte(int b) {
+    byte[] temp = {
+      (byte) b
+    };
+    writeBytes(temp);
+  }
+
+  /**
+   * Write a string into the pngBytes array at a given position.
+   * This uses the getBytes method, so the encoding used will
+   * be its default.
+   *
+   * @param s The string to be written into pngBytes.
+   * @see java.lang.String#getBytes()
+   */
+  protected void writeString(String s) {
+    writeBytes(s.getBytes());
+  }
+
+  /**
+   * Write an array of bytes into the pngBytes array. 
+   * Both dataLen and bytePos are updated. If we don't have 
+   * enough room, this is certainly in image data writing,
+   * so we add just enough for CRC END CRC
+   * 
+   * @param data
+   *        The data to be written into pngBytes.
+   */
+  protected void writeBytes(byte[] data) {
+    int newPos = bytePos + data.length;
+    dataLen = Math.max(dataLen, newPos);
+    if (newPos > pngBytes.length)
+      pngBytes = AU.arrayCopyByte(pngBytes, newPos + 16);
+    System.arraycopy(data, 0, pngBytes, bytePos, data.length);
+    bytePos = newPos;
+  }
+
+}