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#include <IO/HashingWriteBuffer.h>
#include <iomanip>
namespace DB
{
/// computation of the hash depends on the partitioning of blocks
/// so you need to compute a hash of n complete pieces and one incomplete
template <typename Buffer>
void IHashingBuffer<Buffer>::calculateHash(DB::BufferBase::Position data, size_t len)
{
if (len)
{
/// if the data is less than `block_size`, then put them into buffer and calculate hash later
if (block_pos + len < block_size)
{
memcpy(&BufferWithOwnMemory<Buffer>::memory[block_pos], data, len);
block_pos += len;
}
else
{
/// if something is already written to the buffer, then we'll add it
if (block_pos)
{
size_t n = block_size - block_pos;
memcpy(&BufferWithOwnMemory<Buffer>::memory[block_pos], data, n);
append(&BufferWithOwnMemory<Buffer>::memory[0]);
len -= n;
data += n;
block_pos = 0;
}
while (len >= block_size)
{
append(data);
len -= block_size;
data += block_size;
}
/// write the remainder to its buffer
if (len)
{
memcpy(&BufferWithOwnMemory<Buffer>::memory[0], data, len);
block_pos = len;
}
}
}
}
template class IHashingBuffer<DB::ReadBuffer>;
template class IHashingBuffer<DB::WriteBuffer>;
}
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