Luna/kernel/src/fs/ext2/Inode.cpp

#include "fs/ext2/Inode.h"

namespace Ext2
{
    Inode::Inode(Badge<FileSystem>, FileSystem* fs) : m_fs(fs)
    {
    }

    Result<usize> Inode::read(u8* buf, usize offset, usize length) const
    {
        if (length == 0) return 0;

        if (offset > size()) return 0;
        if (offset + length > size()) length = size() - offset;

        const usize block_size = m_fs->m_block_size;

        usize to_read = length;

        if (offset % block_size)
        {
            usize block_offset = (offset % block_size);
            usize block = find_block(offset / block_size);
            usize size_to_read = block_size - block_offset;

            usize host_offset = (block * block_size) + block_offset;

            // FIXME: Cache this data.
            TRY(m_fs->m_host_device->read(buf, host_offset, size_to_read));

            to_read -= size_to_read;
            buf += size_to_read;
            offset += size_to_read;
        }

        while (to_read >= block_size)
        {
            usize block = find_block(offset / block_size);

            usize host_offset = block * block_size;

            // FIXME: Cache this data.
            TRY(m_fs->m_host_device->read(buf, host_offset, block_size));

            to_read -= block_size;
            buf += block_size;
            offset += block_size;
        }

        if (to_read > 0)
        {
            usize block = find_block(offset / block_size);

            usize host_offset = block * block_size;

            // FIXME: Cache this data.
            TRY(m_fs->m_host_device->read(buf, host_offset, to_read));
        }

        return length;
    }

    usize Inode::find_block(usize index) const
    {
        expect(index < 12, "ext2: Finding blocks in the indirect pointers is not yet supported");

        return m_raw_inode.direct_pointers[index];
    }
}