1 files changed, 190 insertions, 0 deletions
diff --git a/core/src/main/java/org/spongycastle/util/encoders/HexEncoder.java b/core/src/main/java/org/spongycastle/util/encoders/HexEncoder.java
new file mode 100644
index 00000000..16120129
--- /dev/null
+++ b/core/src/main/java/org/spongycastle/util/encoders/HexEncoder.java
@@ -0,0 +1,190 @@
+package org.spongycastle.util.encoders;
+
+import java.io.IOException;
+import java.io.OutputStream;
+
+/**
+ * A streaming Hex encoder.
+ */
+public class HexEncoder
+    implements Encoder
+{
+    protected final byte[] encodingTable =
+    {
+        (byte)'0', (byte)'1', (byte)'2', (byte)'3', (byte)'4', (byte)'5', (byte)'6', (byte)'7',
+        (byte)'8', (byte)'9', (byte)'a', (byte)'b', (byte)'c', (byte)'d', (byte)'e', (byte)'f'
+    };
+
+    /*
+     * set up the decoding table.
+     */
+    protected final byte[] decodingTable = new byte[128];
+
+    protected void initialiseDecodingTable()
+    {
+        for (int i = 0; i < decodingTable.length; i++)
+        {
+            decodingTable[i] = (byte)0xff;
+        }
+
+        for (int i = 0; i < encodingTable.length; i++)
+        {
+            decodingTable[encodingTable[i]] = (byte)i;
+        }
+        
+        decodingTable['A'] = decodingTable['a'];
+        decodingTable['B'] = decodingTable['b'];
+        decodingTable['C'] = decodingTable['c'];
+        decodingTable['D'] = decodingTable['d'];
+        decodingTable['E'] = decodingTable['e'];
+        decodingTable['F'] = decodingTable['f'];
+    }
+    
+    public HexEncoder()
+    {
+        initialiseDecodingTable();
+    }
+    
+    /**
+     * encode the input data producing a Hex output stream.
+     *
+     * @return the number of bytes produced.
+     */
+    public int encode(
+        byte[]                data,
+        int                    off,
+        int                    length,
+        OutputStream    out) 
+        throws IOException
+    {        
+        for (int i = off; i < (off + length); i++)
+        {
+            int    v = data[i] & 0xff;
+
+            out.write(encodingTable[(v >>> 4)]);
+            out.write(encodingTable[v & 0xf]);
+        }
+
+        return length * 2;
+    }
+
+    private static boolean ignore(
+        char    c)
+    {
+        return c == '\n' || c =='\r' || c == '\t' || c == ' ';
+    }
+
+    /**
+     * decode the Hex encoded byte data writing it to the given output stream,
+     * whitespace characters will be ignored.
+     *
+     * @return the number of bytes produced.
+     */
+    public int decode(
+        byte[]          data,
+        int             off,
+        int             length,
+        OutputStream    out)
+        throws IOException
+    {
+        byte    b1, b2;
+        int     outLen = 0;
+        
+        int     end = off + length;
+        
+        while (end > off)
+        {
+            if (!ignore((char)data[end - 1]))
+            {
+                break;
+            }
+            
+            end--;
+        }
+        
+        int i = off;
+        while (i < end)
+        {
+            while (i < end && ignore((char)data[i]))
+            {
+                i++;
+            }
+            
+            b1 = decodingTable[data[i++]];
+            
+            while (i < end && ignore((char)data[i]))
+            {
+                i++;
+            }
+            
+            b2 = decodingTable[data[i++]];
+
+            if ((b1 | b2) < 0)
+            {
+                throw new IOException("invalid characters encountered in Hex data");
+            }
+
+            out.write((b1 << 4) | b2);
+            
+            outLen++;
+        }
+
+        return outLen;
+    }
+    
+    /**
+     * decode the Hex encoded String data writing it to the given output stream,
+     * whitespace characters will be ignored.
+     *
+     * @return the number of bytes produced.
+     */
+    public int decode(
+        String          data,
+        OutputStream    out)
+        throws IOException
+    {
+        byte    b1, b2;
+        int     length = 0;
+        
+        int     end = data.length();
+        
+        while (end > 0)
+        {
+            if (!ignore(data.charAt(end - 1)))
+            {
+                break;
+            }
+            
+            end--;
+        }
+        
+        int i = 0;
+        while (i < end)
+        {
+            while (i < end && ignore(data.charAt(i)))
+            {
+                i++;
+            }
+            
+            b1 = decodingTable[data.charAt(i++)];
+            
+            while (i < end && ignore(data.charAt(i)))
+            {
+                i++;
+            }
+            
+            b2 = decodingTable[data.charAt(i++)];
+
+            if ((b1 | b2) < 0)
+            {
+                throw new IOException("invalid characters encountered in Hex string");
+            }
+
+            out.write((b1 << 4) | b2);
+            
+            length++;
+        }
+
+        return length;
+    }
+}