mariadb/newbrt/bread.h
Bradley C. Kuszmaul 1f796663cd Check in the code for compressing the rolltmp file.
This was a tricky merge.  In the 1332a directory I did:
{{{
svn merge https://svn.tokutek.com/tokudb/toku/tokudb.1032b+1332@8415 https://svn.tokutek.com/tokudb/toku/tokudb.1032b+1332@8416
}}}
Then I was able to resolve the conflicts.

Then in the main line I did:
{{{
svn merge -r9042:9046 https://svn.tokutek.com/tokudb/toku/tokudb.1332a
}}}

Fixes #1332.


git-svn-id: file:///svn/toku/tokudb@9047 c7de825b-a66e-492c-adef-691d508d4ae1
2013-04-16 23:57:38 -04:00

27 lines
1.2 KiB
C

#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