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/*************************************************
* Buffered EntropySource Source File *
* (C) 1999-2007 The Botan Project *
*************************************************/
#include <botan/buf_es.h>
#include <botan/bit_ops.h>
#include <botan/util.h>
#include <algorithm>
namespace Botan {
/*************************************************
* Buffered_EntropySource Constructor *
*************************************************/
Buffered_EntropySource::Buffered_EntropySource() : buffer(256)
{
read_pos = write_pos = 0;
done_slow_poll = false;
}
/*************************************************
* Fast Poll *
*************************************************/
u32bit Buffered_EntropySource::fast_poll(byte out[], u32bit length)
{
if(!done_slow_poll) { do_slow_poll(); done_slow_poll = true; }
do_fast_poll();
return copy_out(out, length, buffer.size() / 4);
}
/*************************************************
* Slow Poll *
*************************************************/
u32bit Buffered_EntropySource::slow_poll(byte out[], u32bit length)
{
do_slow_poll();
done_slow_poll = true;
return copy_out(out, length, buffer.size());
}
/*************************************************
* Default fast poll operation *
*************************************************/
void Buffered_EntropySource::do_fast_poll()
{
return do_slow_poll();
}
/*************************************************
* Add entropy to the internal buffer *
*************************************************/
void Buffered_EntropySource::add_bytes(const void* entropy_ptr, u32bit length)
{
const byte* bytes = static_cast<const byte*>(entropy_ptr);
while(length)
{
u32bit copied = std::min(length, buffer.size() - write_pos);
xor_buf(buffer + write_pos, bytes, copied);
bytes += copied;
length -= copied;
write_pos = (write_pos + copied) % buffer.size();
}
}
/*************************************************
* Add entropy to the internal buffer *
*************************************************/
void Buffered_EntropySource::add_bytes(u64bit entropy)
{
add_bytes(&entropy, 8);
}
/*************************************************
* Add entropy to the internal buffer *
*************************************************/
void Buffered_EntropySource::add_timestamp()
{
add_bytes(system_clock());
}
/*************************************************
* Take entropy from the internal buffer *
*************************************************/
u32bit Buffered_EntropySource::copy_out(byte out[], u32bit length,
u32bit max_read)
{
length = std::min(length, max_read);
u32bit copied = std::min(length, buffer.size() - read_pos);
xor_buf(out, buffer + read_pos, copied);
read_pos = (read_pos + copied) % buffer.size();
return copied;
}
}
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