- /* Sector to write, starting byte offset within sector. */
- off_t sector_idx;
- int sector_ofs = file_ofs % DISK_SECTOR_SIZE;
-
- /* Bytes left in file, bytes left in sector, lesser of the two. */
- off_t file_left = inode_length (file->inode) - file_ofs;
- int sector_left = DISK_SECTOR_SIZE - sector_ofs;
- int min_left = file_left < sector_left ? file_left : sector_left;
-
- /* Number of bytes to actually write into this sector. */
- int chunk_size = size < min_left ? size : min_left;
- if (chunk_size <= 0)
- break;
-
- /* If the sector contains data before or after the chunk
- we're writing, then we need to read in the sector
- first. Otherwise we start with a sector of all zeros. */
- sector_idx = inode_byte_to_sector (file->inode, file_ofs);
- if (sector_ofs > 0 || chunk_size < sector_left)
- disk_read (filesys_disk, sector_idx, file->bounce);
- else
- memset (file->bounce, 0, DISK_SECTOR_SIZE);
- memcpy (file->bounce + sector_ofs, buffer + bytes_written, chunk_size);
- disk_write (filesys_disk, sector_idx, file->bounce);
-
- /* Advance. */
- size -= chunk_size;
- file_ofs += chunk_size;
- bytes_written += chunk_size;