/// <summary>
/// Search for ZIP 'End of central directory record' near the end of file.
/// Returns offset of 'PK' signature or -1 if no signature was found.
/// </summary>
internal unsafe long SearchForSignature(ArcView file, byte[] signature)
{
if (signature.Length < 4)
{
throw new ArgumentException("Invalid ZIP file signature", "signature");
}
uint tail_size = (uint)Math.Min(file.MaxOffset, 0x10016L);
if (tail_size < 0x16)
{
return(-1);
}
var start_offset = file.MaxOffset - tail_size;
using (var view = file.CreateViewAccessor(start_offset, tail_size))
using (var pointer = new ViewPointer(view, start_offset))
{
byte *ptr_end = pointer.Value;
byte *ptr = ptr_end + tail_size - 0x16;
for (; ptr >= ptr_end; --ptr)
{
if (signature[3] == ptr[3] && signature[2] == ptr[2] &&
signature[1] == ptr[1] && signature[0] == ptr[0])
{
return(start_offset + (ptr - ptr_end));
}
}
return(-1);
}
}
/// <summary>
/// Search for byte sequence within specified section.
/// </summary>
/// <returns>Offset of byte sequence, if found, -1 otherwise.</returns>
public long FindString(Section section, byte[] seq, int step = 1)
{
if (step <= 0)
{
throw new ArgumentOutOfRangeException("step", "Search step should be positive integer.");
}
long offset = section.Offset;
if (offset < 0 || offset > m_file.MaxOffset)
{
throw new ArgumentOutOfRangeException("section", "Invalid executable file section specified.");
}
uint seq_length = (uint)seq.Length;
if (0 == seq_length || section.Size < seq_length)
{
return(-1);
}
long end_offset = Math.Min(m_file.MaxOffset, offset + section.Size);
unsafe
{
while (offset < end_offset)
{
uint page_size = (uint)Math.Min(0x10000L, end_offset - offset);
if (page_size < seq_length)
{
break;
}
using (var view = m_file.CreateViewAccessor(offset, page_size))
using (var ptr = new ViewPointer(view, offset))
{
byte *page_begin = ptr.Value;
byte *page_end = page_begin + page_size - seq_length;
byte *p;
for (p = page_begin; p <= page_end; p += step)
{
int i = 0;
while (p[i] == seq[i])
{
if (++i == seq.Length)
{
return(offset + (p - page_begin));
}
}
}
offset += p - page_begin;
}
}
}
return(-1);
}
