private void WriteNewFile(FileStream fs, WXAPKG_FILE file, string targetDir)
{
fs.Seek(file.m_offset, SeekOrigin.Begin);
string fileName = targetDir + "\\" + file.m_name;
FileInfo fi = new FileInfo(fileName);
if (!Directory.Exists(fi.DirectoryName))
{
Directory.CreateDirectory(fi.DirectoryName);
}
Log($"抽取文件: {fi.FullName}");
FileStream outFs = new FileStream(fi.FullName, FileMode.Create, FileAccess.Write, FileShare.ReadWrite);
byte[] buffer = new byte[32 * 1024];
int alreadyRead = 0;
while (true)
{
if (alreadyRead + buffer.Length > file.m_size)
{
int shouldRead = file.m_size - alreadyRead;
fs.Read(buffer, 0, shouldRead);
outFs.Write(buffer, 0, shouldRead);
alreadyRead += shouldRead;
break;
}
else
{
fs.Read(buffer, 0, buffer.Length);
outFs.Write(buffer, 0, buffer.Length);
alreadyRead += buffer.Length;
}
}
outFs.Flush();
outFs.Close();
}
public void Extractor(string wxFile, string targetDir)
{
FileStream fs = null;
try
{
fs = new FileStream(wxFile, FileMode.Open, FileAccess.Read);
// 获取头部信息
WXAPKG_HEADER header = new WXAPKG_HEADER();
// 第一个标识，固定为 0xBE
header.m_first_mark = (byte)fs.ReadByte();
if (0xBE != header.m_first_mark)
{
Log("文件第一个标识有误，非 WXAPKG 格式文件！");
throw new Exception("文件第一个标识有误，非 WXAPKG 格式文件！");
}
// 版本号，0 -> 微信分发到客户端 1 -> 开发者上传到微信后台
byte[] b_int = new byte[4];
fs.Read(b_int, 0, b_int.Length);
header.m_edition = IPAddress.NetworkToHostOrder(BitConverter.ToInt32(b_int, 0));
// 索引段的长度
fs.Read(b_int, 0, b_int.Length);
header.m_index_info_length = IPAddress.NetworkToHostOrder(BitConverter.ToInt32(b_int, 0));
// 数据段的长度
fs.Read(b_int, 0, b_int.Length);
header.m_body_info_length = IPAddress.NetworkToHostOrder(BitConverter.ToInt32(b_int, 0));
// 第二个标识，固定为 0xED
header.m_last_mark = (byte)fs.ReadByte();
if (0xED != header.m_last_mark)
{
Log("文件标识有误，非 WXAPKG 格式文件！");
throw new Exception("文件标识有误，非 WXAPKG 格式文件！");
}
// 文件数量
fs.Read(b_int, 0, b_int.Length);
header.m_file_count = IPAddress.NetworkToHostOrder(BitConverter.ToInt32(b_int, 0));
List <WXAPKG_FILE> fileList = new List <WXAPKG_FILE>();
// 获取每个文件的信息
for (int i = 0; i < header.m_file_count; i++)
{
WXAPKG_FILE file = new WXAPKG_FILE();
// 文件长度
fs.Read(b_int, 0, b_int.Length);
file.m_name_length = IPAddress.NetworkToHostOrder(BitConverter.ToInt32(b_int, 0));
if (file.m_name_length > 255)
{
throw new Exception("错误的文件长度！");
}
// 文件名
byte[] b_name = new byte[file.m_name_length];
fs.Read(b_name, 0, b_name.Length);
file.m_name = Encoding.UTF8.GetString(b_name);
// 偏移
fs.Read(b_int, 0, b_int.Length);
file.m_offset = IPAddress.NetworkToHostOrder(BitConverter.ToInt32(b_int, 0));
// 大小
fs.Read(b_int, 0, b_int.Length);
file.m_size = IPAddress.NetworkToHostOrder(BitConverter.ToInt32(b_int, 0));
fileList.Add(file);
}
Log($"准备抽取文件到目录{targetDir}");
for (int i = 0; i < fileList.Count; i++)
{
WXAPKG_FILE file = fileList[i];
WriteNewFile(fs, file, targetDir);
}
}
catch (Exception ex)
{
MessageBox.Show(ex.ToString());
}
finally
{
if (null != fs)
{
fs.Close();
}
}
}