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|
//
// System.Security.Cryptography.ToBase64Transform
//
// Author:
// Sergey Chaban (serge@wildwestsoftware.com)
//
using System;
using System.Security.Cryptography;
namespace System.Security.Cryptography {
public class ToBase64Transform : ICryptoTransform {
/// <summary>
/// Default constructor.
/// </summary>
public ToBase64Transform ()
{
}
/// <summary>
/// </summary>
public bool CanTransformMultipleBlocks {
get {
return false;
}
}
/// <summary>
/// Returns the input block size for the Base64 encoder.
/// </summary>
/// <remarks>
/// The returned value is always 3.
/// </remarks>
public int InputBlockSize {
get {
return 3;
}
}
/// <summary>
/// Returns the output block size for the Base64 encoder.
/// </summary>
/// <remarks>
/// The value returned by this property is always 4.
/// </remarks>
public int OutputBlockSize {
get {
return 4;
}
}
/// <summary>
/// </summary>
public int TransformBlock (byte [] inputBuffer,
int inputOffset,
int inputCount,
byte [] outputBuffer,
int outputOffset)
{
if (inputCount != this.InputBlockSize)
throw new CryptographicException();
byte [] lookup = Base64Table.EncodeTable;
int b1 = inputBuffer [inputOffset];
int b2 = inputBuffer [inputOffset + 1];
int b3 = inputBuffer [inputOffset + 2];
outputBuffer [outputOffset] = lookup [b1 >> 2];
outputBuffer [outputOffset+1] = lookup [((b1 << 4) & 0x30) | (b2 >> 4)];
outputBuffer [outputOffset+2] = lookup [((b2 << 2) & 0x3c) | (b3 >> 6)];
outputBuffer [outputOffset+3] = lookup [b3 & 0x3f];
return this.OutputBlockSize;
}
// LAMESPEC: It's not clear from Beta2 docs what should be
// happening here if inputCount > InputBlockSize.
// It just "Converts the specified region of the specified
// byte array" and that's all.
// Beta2 implementation throws some strange (and undocumented)
// exception in such case. The exception is thrown by
// System.Convert and not the method itself.
// Anyhow, this implementation just encodes blocks of any size,
// like any usual Base64 encoder.
/// <summary>
/// </summary>
public byte [] TransformFinalBlock (byte [] inputBuffer,
int inputOffset,
int inputCount)
{
int blockLen = this.InputBlockSize;
int outLen = this.OutputBlockSize;
int fullBlocks = inputCount / blockLen;
int tail = inputCount % blockLen;
byte [] res = new byte [(inputCount != 0)
? ((inputCount + 2) / blockLen) * outLen
: 0];
int outputOffset = 0;
for (int i = 0; i < fullBlocks; i++) {
TransformBlock (inputBuffer, inputOffset,
blockLen, res, outputOffset);
inputOffset += blockLen;
outputOffset += outLen;
}
byte [] lookup = Base64Table.EncodeTable;
int b1,b2;
// When fewer than 24 input bits are available
// in an input group, zero bits are added
// (on the right) to form an integral number of
// 6-bit groups.
switch (tail) {
case 0:
break;
case 1:
b1 = inputBuffer [inputOffset];
res [outputOffset] = lookup [b1 >> 2];
res [outputOffset+1] = lookup [(b1 << 4) & 0x30];
// padding
res [outputOffset+2] = (byte)'=';
res [outputOffset+3] = (byte)'=';
break;
case 2:
b1 = inputBuffer [inputOffset];
b2 = inputBuffer [inputOffset + 1];
res [outputOffset] = lookup [b1 >> 2];
res [outputOffset+1] = lookup [((b1 << 4) & 0x30) | (b2 >> 4)];
res [outputOffset+2] = lookup [(b2 << 2) & 0x3c];
// one-byte padding
res [outputOffset+3] = (byte)'=';
break;
default:
break;
}
return res;
}
/// <summary>
/// </summary>
public override string ToString ()
{
return "mono::System.Security.Cryptography.ToBase64Transform";
}
} // ToBase64Transform
[MonoTODO ("Put me in a separate file")]
internal sealed class Base64Table {
// This is the Base64 alphabet as described in RFC 2045
// (Table 1, page 25).
private static string ALPHABET =
"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
private static byte[] encodeTable;
private static byte[] decodeTable;
static Base64Table ()
{
int len = ALPHABET.Length;
encodeTable = new byte [len];
for (int i=0; i < len; i++) {
encodeTable [i] = (byte) ALPHABET [i];
}
decodeTable = new byte [1 + (int)'z'];
for (int i=0; i < decodeTable.Length; i++) {
decodeTable [i] = Byte.MaxValue;
}
for (int i=0; i < len; i++) {
char ch = ALPHABET [i];
decodeTable [(int)ch] = (byte) i;
}
}
private Base64Table ()
{
// Never instantiated.
}
internal static byte [] EncodeTable {
get {
return encodeTable;
}
}
internal static byte [] DecodeTable {
get {
return decodeTable;
}
}
} // Base64Table
} // System.Security.Cryptography
|
