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/* - mode: c; c-basic-offset: 2; indent-tabs-mode: nil; -*-
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* vim:expandtab:shiftwidth=2:tabstop=2:smarttab:
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* Copyright (C) 2008 MySQL
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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#ifndef mysys_iocache_h
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#define mysys_iocache_h
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#if defined(__cplusplus)
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typedef int (*IO_CACHE_CALLBACK)(struct st_io_cache*);
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typedef struct st_io_cache_share
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pthread_mutex_t mutex; /* To sync on reads into buffer. */
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pthread_cond_t cond; /* To wait for signals. */
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pthread_cond_t cond_writer; /* For a synchronized writer. */
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/* Offset in file corresponding to the first byte of buffer. */
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/* If a synchronized write cache is the source of the data. */
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struct st_io_cache *source_cache;
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unsigned char *buffer; /* The read buffer. */
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unsigned char *read_end; /* Behind last valid byte of buffer. */
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int running_threads; /* threads not in lock. */
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int total_threads; /* threads sharing the cache. */
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int error; /* Last error. */
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#ifdef NOT_YET_IMPLEMENTED
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/* whether the structure should be free'd */
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typedef struct st_io_cache /* Used when cacheing files */
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/* Offset in file corresponding to the first byte of unsigned char* buffer. */
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The offset of end of file for READ_CACHE and WRITE_CACHE.
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For SEQ_READ_APPEND it the maximum of the actual end of file and
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the position represented by read_end.
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/* Points to current read position in the buffer */
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unsigned char *read_pos;
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/* the non-inclusive boundary in the buffer for the currently valid read */
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unsigned char *read_end;
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unsigned char *buffer; /* The read buffer */
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/* Used in ASYNC_IO */
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unsigned char *request_pos;
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/* Only used in WRITE caches and in SEQ_READ_APPEND to buffer writes */
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unsigned char *write_buffer;
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Only used in SEQ_READ_APPEND, and points to the current read position
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in the write buffer. Note that reads in SEQ_READ_APPEND caches can
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happen from both read buffer (unsigned char* buffer) and write buffer
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(unsigned char* write_buffer).
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unsigned char *append_read_pos;
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/* Points to current write position in the write buffer */
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unsigned char *write_pos;
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/* The non-inclusive boundary of the valid write area */
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unsigned char *write_end;
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Current_pos and current_end are convenience variables used by
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my_b_tell() and other routines that need to know the current offset
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current_pos points to &write_pos, and current_end to &write_end in a
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WRITE_CACHE, and &read_pos and &read_end respectively otherwise
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unsigned char **current_pos, **current_end;
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The lock is for append buffer used in SEQ_READ_APPEND cache
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need mutex copying from append buffer to read buffer.
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pthread_mutex_t append_buffer_lock;
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The following is used when several threads are reading the
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same file in parallel. They are synchronized on disk
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accesses reading the cached part of the file asynchronously.
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It should be set to NULL to disable the feature. Only
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READ_CACHE mode is supported.
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IO_CACHE_SHARE *share;
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A caller will use my_b_read() macro to read from the cache
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if the data is already in cache, it will be simply copied with
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memcpy() and internal variables will be accordinging updated with
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no functions invoked. However, if the data is not fully in the cache,
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my_b_read() will call read_function to fetch the data. read_function
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must never be invoked directly.
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int (*read_function)(struct st_io_cache *,unsigned char *,size_t);
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Same idea as in the case of read_function, except my_b_write() needs to
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be replaced with my_b_append() for a SEQ_READ_APPEND cache
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int (*write_function)(struct st_io_cache *,const unsigned char *,size_t);
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Specifies the type of the cache. Depending on the type of the cache
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certain operations might not be available and yield unpredicatable
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results. Details to be documented later
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enum cache_type type;
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Callbacks when the actual read I/O happens. These were added and
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are currently used for binary logging of LOAD DATA INFILE - when a
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block is read from the file, we create a block create/append event, and
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when IO_CACHE is closed, we create an end event. These functions could,
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of course be used for other things
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IO_CACHE_CALLBACK pre_read;
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IO_CACHE_CALLBACK post_read;
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IO_CACHE_CALLBACK pre_close;
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Counts the number of times, when we were forced to use disk. We use it to
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increase the binlog_cache_disk_use status variable.
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uint32_t disk_writes;
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void* arg; /* for use by pre/post_read */
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char *file_name; /* if used with 'open_cached_file' */
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File file; /* file descriptor */
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seek_not_done is set by my_b_seek() to inform the upcoming read/write
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operation that a seek needs to be preformed prior to the actual I/O
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error is 0 if the cache operation was successful, -1 if there was a
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"hard" error, and the actual number of I/O-ed bytes if the read/write was
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int seek_not_done,error;
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/* buffer_length is memory size allocated for buffer or write_buffer */
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size_t buffer_length;
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/* read_length is the same as buffer_length except when we use async io */
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myf myflags; /* Flags used to my_read/my_write */
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alloced_buffer is 1 if the buffer was allocated by init_io_cache() and
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0 if it was supplied by the user.
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Currently READ_NET is the only one that will use a buffer allocated
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As inidicated by ifdef, this is for async I/O, which is not currently
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used (because it's not reliable on all systems)
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my_off_t aio_read_pos;
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my_aio_result aio_result;
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/* tell write offset in the SEQ_APPEND cache */
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int my_b_copy_to_file(IO_CACHE *cache, FILE *file);
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my_off_t my_b_append_tell(IO_CACHE* info);
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my_off_t my_b_safe_tell(IO_CACHE* info); /* picks the correct tell() */
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extern int init_io_cache(IO_CACHE *info,File file,size_t cachesize,
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enum cache_type type,my_off_t seek_offset,
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bool use_async_io, myf cache_myflags);
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extern bool reinit_io_cache(IO_CACHE *info,enum cache_type type,
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my_off_t seek_offset,bool use_async_io,
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extern void setup_io_cache(IO_CACHE* info);
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extern int _my_b_read(IO_CACHE *info,unsigned char *Buffer,size_t Count);
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extern int _my_b_read_r(IO_CACHE *info,unsigned char *Buffer,size_t Count);
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extern void init_io_cache_share(IO_CACHE *read_cache, IO_CACHE_SHARE *cshare,
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IO_CACHE *write_cache, uint32_t num_threads);
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extern void remove_io_thread(IO_CACHE *info);
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extern int _my_b_seq_read(IO_CACHE *info,unsigned char *Buffer,size_t Count);
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extern int _my_b_net_read(IO_CACHE *info,unsigned char *Buffer,size_t Count);
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extern int _my_b_get(IO_CACHE *info);
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extern int _my_b_async_read(IO_CACHE *info,unsigned char *Buffer,size_t Count);
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extern int _my_b_write(IO_CACHE *info,const unsigned char *Buffer,
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extern int my_b_append(IO_CACHE *info,const unsigned char *Buffer,
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extern int my_b_safe_write(IO_CACHE *info,const unsigned char *Buffer,
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extern int my_block_write(IO_CACHE *info, const unsigned char *Buffer,
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size_t Count, my_off_t pos);
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extern int my_b_flush_io_cache(IO_CACHE *info, int need_append_buffer_lock);
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#define flush_io_cache(info) my_b_flush_io_cache((info),1)
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extern int end_io_cache(IO_CACHE *info);
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extern size_t my_b_fill(IO_CACHE *info);
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extern void my_b_seek(IO_CACHE *info,my_off_t pos);
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extern size_t my_b_gets(IO_CACHE *info, char *to, size_t max_length);
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extern my_off_t my_b_filelength(IO_CACHE *info);
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extern size_t my_b_printf(IO_CACHE *info, const char* fmt, ...);
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extern size_t my_b_vprintf(IO_CACHE *info, const char* fmt, va_list ap);
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extern bool open_cached_file(IO_CACHE *cache,const char *dir,
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const char *prefix, size_t cache_size,
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extern bool real_open_cached_file(IO_CACHE *cache);
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extern void close_cached_file(IO_CACHE *cache);
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#if defined(__cplusplus)
added
removed
mysys/iocache.h
