mariadb/newbrt/bread.h

#ifndef BREAD_H
#define BREAD_H

// A BREAD reads a file backwards using buffered I/O.  BREAD stands for Buffered Read or Backwards Read.
// Conceivably, we could read forward too.
// The buffered I/O is buffered using a large buffer (e.g., something like a megabyte).
// Furthermore, data is compressed into blocks.  Each block is a 4-byte compressed length (in network order), followed by compressed data, followed by a 4-byte uncompressed-length (in network order), followed by  a 4-byte compressed length
// The compressed-length appears twice so that the file can be read backward or forward.
// If not for the large-buffer requirement, as well as compression, as well as reading backward, we could have used a FILE.

#include <sys/types.h>
typedef struct bread *BREAD;

BREAD create_bread_from_fd_initialize_at(int fd);
// Effect:  Given a file descriptor, fd, create a BREAD.
// Requires: The fd must be an open fd.

int close_bread_without_closing_fd(BREAD);
// Effect: Close the BREAD, but don't close the underlying fd.

ssize_t bread_backwards(BREAD, void *buf, size_t nbytes);
// Read nbytes into buf, reading backwards.  

int bread_has_more(BREAD);
// Is there more to read?

#endif