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using System;
using System.Collections.Generic;
using System.Text;
using System.IO;
using System.Security.Cryptography;
using System.IO.Compression;
namespace ExifLibrary
{
/// <summary>
/// Contains utility functions.
/// </summary>
public class Utility
{
#region File I/O
/// <summary>
/// Reads the entire stream and returns its contents as a byte array.
/// </summary>
/// <param name="stream">The <see cref="System.IO.Stream"/> to read.</param>
/// <returns>Contents of the <paramref name="stream"/> as a byte array.</returns>
public static byte[] GetStreamBytes(Stream stream)
{
using (MemoryStream mem = new MemoryStream())
{
stream.Seek(0, SeekOrigin.Begin);
byte[] b = new byte[32768];
int r;
while ((r = stream.Read(b, 0, b.Length)) > 0)
mem.Write(b, 0, r);
return mem.ToArray();
}
}
/// <summary>
/// Reads the stream into the given byte array.
/// </summary>
/// <param name="stream">The <see cref="System.IO.Stream"/> to read.</param>
/// <param name="rem">The number of bytes to read.</param>
/// <returns>Contents of the <paramref name="stream"/> as a byte array.</returns>
public static byte[] GetStreamBytes(Stream stream, long rem)
{
using (MemoryStream mem = new MemoryStream())
{
byte[] b = new byte[32768];
int r;
while (rem > 0 && (r = stream.Read(b, 0, (int)Math.Min(rem, b.LongLength))) > 0)
{
mem.Write(b, 0, r);
rem = rem - r;
}
return mem.ToArray();
}
}
#endregion
#region Crypto
public static class CRC32
{
// Table of CRCs of all 8-bit messages.
private static ulong[] table = null;
/// <summary>
/// Make the table for a fast CRC.
/// </summary>
private static void Initialize()
{
table = new ulong[256];
for (int n = 0; n < 256; n++)
{
ulong c = (ulong)n;
for (int k = 0; k < 8; k++)
{
if ((c & 1) != 0)
c = 0xedb88320L ^ (c >> 1);
else
c = c >> 1;
}
table[n] = c;
}
}
/// <summary>
/// Updates a running CRC with the given bytes. The CRC
/// should be initialized to all 1's, and the transmitted value
/// is the 1's complement of the final running CRC (see the
/// CRC routine below).
/// </summary>
/// <param name="crc">Initial CRC.</param>
/// <param name="buffer">The bytes to calculate the CRC of.</param>
/// <returns>Checksum as 1's complement of the final running CRC.</returns>
private static ulong UpdateCRC(ulong crc, byte[] buffer)
{
ulong c = crc;
if (table == null)
Initialize();
for (int n = 0; n < buffer.Length; n++)
{
c = table[(c ^ buffer[n]) & 0xff] ^ (c >> 8);
}
return c;
}
/// <summary>
/// Return the CRC of the given bytes.
/// </summary>
/// <param name="buf">The bytes to calculate the CRC of.</param>
/// <returns>CRC checksum.</returns>
public static ulong CRC(byte[] buffer)
{
return UpdateCRC(0xffffffffL, buffer) ^ 0xffffffffL;
}
/// <summary>
/// Return the CRC of the given bytes.
/// </summary>
/// <param name="crc">Initial CRC.</param>
/// <param name="buf">The bytes to calculate the CRC of.</param>
/// <returns>CRC checksum.</returns>
public static ulong Hash(ulong crc, byte[] buffer)
{
crc ^= 0xffffffffL;
return UpdateCRC(crc, buffer) ^ 0xffffffffL;
}
}
#endregion
#region Compression
/// <summary>
/// Compresses the given string.
/// </summary>
/// <param name="text">Input string.</param>
/// <param name="encoding">Text encoding.</param>
/// <returns>The compressed bytes.</returns>
public static byte[] CompressString(String text, Encoding encoding)
{
using (MemoryStream stream = new MemoryStream())
using (DeflateStream zip = new DeflateStream(stream, CompressionMode.Compress))
using (StreamWriter writer = new StreamWriter(zip, encoding))
{
writer.Write(text);
return stream.ToArray();
}
}
/// <summary>
/// Compresses the given bytes representing a string.
/// </summary>
/// <param name="input">Input data.</param>
/// <param name="encoding">Text encoding.</param>
/// <returns>The decompressed string.</returns>
public static string DecompressString(byte[] input, Encoding encoding)
{
using (MemoryStream stream = new MemoryStream(input))
{
//stream.Seek(2, SeekOrigin.Begin); // Skip zlib flags
int b1 = stream.ReadByte();
int b2 = stream.ReadByte();
using (DeflateStream zip = new DeflateStream(stream, CompressionMode.Decompress))
using (StreamReader reader = new StreamReader(zip, encoding))
{
return reader.ReadToEnd();
}
}
}
#endregion
#region Arrays
/// <summary>
/// Splits the given byte array at seperators.
/// </summary>
/// <param name="data">Input array.</param>
/// <param name="seperator">Separator byte.</param>
/// <returns>Sub arrays splitted at the separator.</returns>
public static List<byte[]> SplitByteArray(byte[] data, byte seperator)
{
List<byte[]> output = new List<byte[]>();
long lastSepIndex = -1;
long sepIndex = -1;
for (long i = 0; i < data.LongLength; i++)
{
if (data[i] == seperator)
{
sepIndex = i;
byte[] subArray = new byte[sepIndex - (lastSepIndex + 1)];
Array.Copy(data, lastSepIndex + 1, subArray, 0, subArray.LongLength);
lastSepIndex = sepIndex;
output.Add(subArray);
}
}
if (lastSepIndex < data.LongLength - 1)
{
sepIndex = data.LongLength - 1;
byte[] subArray = new byte[sepIndex - (lastSepIndex + 1)];
Array.Copy(data, lastSepIndex + 1, subArray, 0, subArray.LongLength);
lastSepIndex = sepIndex;
output.Add(subArray);
}
return output;
}
#endregion
}
}
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