2459
2459
The function ensures that a block of data of size length from file
2460
2460
positioned at filepos is in the buffers for some key cache blocks.
2461
2461
Then the function either copies the data into the buffer buff, or,
2464
2464
Filepos must be a multiple of 'block_length', but it doesn't
2465
2465
have to be a multiple of key_cache_block_size;