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mariadb/mysys/mf_iocache.c
Vasilii Lakhin 5f7c2a617f Fix typos in C comments in miscellaneous files
2025-03-24 13:36:28 +11:00

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/*
Copyright (c) 2000, 2011, Oracle and/or its affiliates
Copyright (c) 2010, 2021, MariaDB
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1335 USA */
/*
Caсhing of files with only does (sequential) read or writes of fixed-
length records. A read isn't allowed to go over file-length. A read is ok
if it ends at file-length and next read can try to read after file-length
(and get a EOF-error).
Possibly use of asyncronic io.
macros for read and writes for faster io.
Used instead of FILE when reading or writing whole files.
One can change info->pos_in_file to a higher value to skip bytes in file if
also info->read_pos is set to info->read_end.
If called through open_cached_file(), then the temporary file will
only be created if a write exceeds the file buffer or if one calls
my_b_flush_io_cache().
If one uses SEQ_READ_APPEND, then two buffers are allocated, one for
reading and another for writing. Reads are first done from disk and
then done from the write buffer. This is an efficient way to read
from a log file when one is writing to it at the same time.
For this to work, the file has to be opened in append mode!
Note that when one uses SEQ_READ_APPEND, one MUST write using
my_b_append ! This is needed because we need to lock the mutex
every time we access the write buffer.
TODO:
When one SEQ_READ_APPEND and we are reading and writing at the same time,
each time the write buffer gets full and it's written to disk, we will
always do a disk read to read a part of the buffer from disk to the
read buffer.
This should be fixed so that when we do a my_b_flush_io_cache() and
we have been reading the write buffer, we should transfer the rest of the
write buffer to the read buffer before we start to reuse it.
*/
#include "mysys_priv.h"
#include <m_string.h>
#include <errno.h>
#include "mysql/psi/mysql_file.h"
PSI_file_key key_file_io_cache;
TMPFILE_SIZE_CB update_tmp_file_size= 0;
#define lock_append_buffer(info) \
mysql_mutex_lock(&(info)->append_buffer_lock)
#define unlock_append_buffer(info) \
mysql_mutex_unlock(&(info)->append_buffer_lock)
#define IO_ROUND_UP(X) (((X)+IO_SIZE-1) & ~(IO_SIZE-1))
#define IO_ROUND_DN(X) ( (X) & ~(IO_SIZE-1))
static int _my_b_cache_read(IO_CACHE *info, uchar *Buffer, size_t Count);
static int _my_b_cache_read_r(IO_CACHE *info, uchar *Buffer, size_t Count);
static int _my_b_seq_read(IO_CACHE *info, uchar *Buffer, size_t Count);
static int _my_b_cache_write(IO_CACHE *info, const uchar *Buffer, size_t Count);
static int _my_b_cache_write_r(IO_CACHE *info, const uchar *Buffer, size_t Count);
int (*_my_b_encr_read)(IO_CACHE *info,uchar *Buffer,size_t Count)= 0;
int (*_my_b_encr_write)(IO_CACHE *info,const uchar *Buffer,size_t Count)= 0;
static inline my_bool tmp_file_track(IO_CACHE *info, ulonglong file_size)
{
if ((info->myflags & (MY_TRACK | MY_TRACK_WITH_LIMIT)) &&
update_tmp_file_size)
{
if (info->tracking.file_size < file_size)
{
int error;
info->tracking.file_size= file_size;
if ((error= update_tmp_file_size(&info->tracking,
!(info->myflags &
MY_TRACK_WITH_LIMIT))))
{
if (info->myflags & MY_WME)
my_error(error, MYF(0));
info->error= -1;
return 1;
}
}
}
return 0;
}
my_bool io_cache_tmp_file_track(IO_CACHE *info, ulonglong file_size)
{
return tmp_file_track(info, file_size);
}
/**
Reset tmp space tracking for the data in the io cache
This is called when deleting or truncating the
cached file.
*/
static void reset_tracking_io_cache(IO_CACHE *info)
{
if ((info->myflags & (MY_TRACK | MY_TRACK_WITH_LIMIT)) &&
info->tracking.file_size)
{
info->tracking.file_size= 0;
update_tmp_file_size(&info->tracking, 1);
}
}
void truncate_io_cache(IO_CACHE *info)
{
if (my_chsize(info->file, 0, 0, MYF(MY_WME)) == 0)
reset_tracking_io_cache(info);
}
static void
init_functions(IO_CACHE* info)
{
enum cache_type type= info->type;
info->read_function = 0; /* Force a core if used */
info->write_function = 0; /* Force a core if used */
switch (type) {
case READ_NET:
/*
Must be initialized by the caller. The problem is that
_my_b_net_read has to be defined in sql directory because of
the dependency on THD, and therefore cannot be visible to
programs that link against mysys but know nothing about THD, such
as myisamchk
*/
DBUG_ASSERT(!(info->myflags & MY_ENCRYPT));
break;
case SEQ_READ_APPEND:
info->read_function = _my_b_seq_read;
DBUG_ASSERT(!(info->myflags & MY_ENCRYPT));
break;
case READ_CACHE:
if (info->myflags & MY_ENCRYPT)
{
DBUG_ASSERT(info->share == 0);
info->read_function = _my_b_encr_read;
break;
}
/* fall through */
case WRITE_CACHE:
if (info->myflags & MY_ENCRYPT)
{
info->write_function = _my_b_encr_write;
break;
}
/* fall through */
case READ_FIFO:
DBUG_ASSERT(!(info->myflags & MY_ENCRYPT));
info->read_function = info->share ? _my_b_cache_read_r : _my_b_cache_read;
info->write_function = info->share ? _my_b_cache_write_r : _my_b_cache_write;
break;
case TYPE_NOT_SET:
DBUG_ASSERT(0);
break;
}
if (type == READ_CACHE || type == WRITE_CACHE || type == SEQ_READ_APPEND)
info->myflags|= MY_FULL_IO;
else
info->myflags&= ~MY_FULL_IO;
}
/*
Initialize an IO_CACHE object
SYNOPSOS
init_io_cache_ext()
info cache handler to initialize
file File that should be associated to to the handler
If == -1 then real_open_cached_file()
will be called when it's time to open file.
cachesize Size of buffer to allocate for read/write
If == 0 then use my_default_record_cache_size
type Type of cache
seek_offset Where cache should start reading/writing
use_async_io Set to 1 of we should use async_io (if available)
cache_myflags Bitmap of different flags
MY_WME | MY_FAE | MY_NABP | MY_FNABP |
MY_DONT_CHECK_FILESIZE
file_key Instrumented file key for temporary cache file
RETURN
0 ok
# error
*/
int init_io_cache_ext(IO_CACHE *info, File file, size_t cachesize,
enum cache_type type, my_off_t seek_offset,
pbool use_async_io, myf cache_myflags,
PSI_file_key file_key __attribute__((unused)))
{
size_t min_cache;
my_off_t pos;
my_off_t end_of_file= ~(my_off_t) 0;
DBUG_ENTER("init_io_cache_ext");
DBUG_PRINT("enter",("cache:%p type: %d pos: %llu",
info, (int) type, (ulonglong) seek_offset));
info->file= file;
info->type= TYPE_NOT_SET; /* Don't set it until mutex are created */
info->pos_in_file= seek_offset;
info->alloced_buffer = 0;
info->buffer=0;
info->seek_not_done= 0;
info->next_file_user= NULL;
info->tracking.previous_file_size= 0;
info->tracking.file_size= 0;
if (file >= 0)
{
DBUG_ASSERT(!(cache_myflags & MY_ENCRYPT));
pos= mysql_file_tell(file, MYF(0));
if ((pos == (my_off_t) -1) && (my_errno == ESPIPE))
{
/*
This kind of object doesn't support seek() or tell(). Don't set a
seek_not_done that will make us again try to seek() later and fail.
Additionally, if we're supposed to start somewhere other than the
the beginning of whatever this file is, then somebody made a bad
assumption.
*/
DBUG_ASSERT(seek_offset == 0);
}
else
info->seek_not_done= MY_TEST(seek_offset != pos);
}
else
if (type == WRITE_CACHE && _my_b_encr_read)
{
cache_myflags|= MY_ENCRYPT;
DBUG_ASSERT(seek_offset == 0);
}
info->disk_writes= 0;
info->share=0;
if (!cachesize && !(cachesize= my_default_record_cache_size))
DBUG_RETURN(1); /* No cache requested */
min_cache=use_async_io ? IO_SIZE*4 : IO_SIZE*2;
if (type == READ_CACHE || type == SEQ_READ_APPEND)
{ /* Assume file isn't growing */
DBUG_ASSERT(!(cache_myflags & MY_ENCRYPT));
if (!(cache_myflags & MY_DONT_CHECK_FILESIZE))
{
/* Calculate end of file to avoid allocating oversized buffers */
end_of_file= mysql_file_seek(file, 0L, MY_SEEK_END, MYF(0));
/* Need to reset seek_not_done now that we just did a seek. */
info->seek_not_done= end_of_file == seek_offset ? 0 : 1;
if (end_of_file < seek_offset)
end_of_file=seek_offset;
/* Trim cache size if the file is very small */
if ((my_off_t) cachesize > end_of_file-seek_offset+IO_SIZE*2-1)
{
cachesize= (size_t) (end_of_file-seek_offset)+IO_SIZE*2-1;
use_async_io=0; /* No need to use async */
}
}
}
cache_myflags &= ~MY_DONT_CHECK_FILESIZE;
if (type != READ_NET)
{
/* Retry allocating memory in smaller blocks until we get one */
cachesize= ((cachesize + min_cache-1) & ~(min_cache-1));
for (;;)
{
size_t buffer_block;
/*
Unset MY_WAIT_IF_FULL bit if it is set, to prevent conflict with
MY_ZEROFILL.
*/
myf flags= (myf) (cache_myflags & ~(MY_WME | MY_WAIT_IF_FULL));
if (cachesize < min_cache)
cachesize = min_cache;
buffer_block= cachesize;
if (type == SEQ_READ_APPEND)
buffer_block *= 2;
else if (cache_myflags & MY_ENCRYPT)
buffer_block= 2*(buffer_block + MY_AES_BLOCK_SIZE) + sizeof(IO_CACHE_CRYPT);
if (cachesize == min_cache)
flags|= (myf) MY_WME;
if ((info->buffer= (uchar*) my_malloc(key_memory_IO_CACHE, buffer_block, flags)) != 0)
{
if (type == SEQ_READ_APPEND)
info->write_buffer= info->buffer + cachesize;
else
info->write_buffer= info->buffer;
info->alloced_buffer= buffer_block;
break; /* Enough memory found */
}
if (cachesize == min_cache)
DBUG_RETURN(2); /* Can't alloc cache */
/* Try with less memory */
cachesize= (cachesize*3/4 & ~(min_cache-1));
}
}
DBUG_PRINT("info",("init_io_cache_ext: cachesize = %lu", (ulong) cachesize));
info->read_length=info->buffer_length=cachesize;
info->myflags=cache_myflags & ~(MY_NABP | MY_FNABP);
info->request_pos= info->read_pos= info->write_pos = info->buffer;
if (type == SEQ_READ_APPEND)
{
info->append_read_pos = info->write_pos = info->write_buffer;
info->write_end = info->write_buffer + info->buffer_length;
mysql_mutex_init(key_IO_CACHE_append_buffer_lock,
&info->append_buffer_lock, MY_MUTEX_INIT_FAST);
}
#if defined(SAFE_MUTEX)
else
{
/* Clear mutex so that safe_mutex will notice that it's not initialized */
bzero((char*) &info->append_buffer_lock, sizeof(info->append_buffer_lock));
}
#endif
if (type == WRITE_CACHE)
info->write_end=
info->buffer+info->buffer_length- (seek_offset & (IO_SIZE-1));
else
info->read_end=info->buffer; /* Nothing in cache */
/* End_of_file may be changed by user later */
info->end_of_file= end_of_file;
info->error=0;
info->type= type;
init_functions(info);
DBUG_RETURN(0);
}
int init_io_cache(IO_CACHE *info, File file, size_t cachesize,
enum cache_type type, my_off_t seek_offset,
my_bool use_async_io, myf cache_myflags)
{
return init_io_cache_ext(info, file, cachesize, type, seek_offset,
use_async_io, cache_myflags, key_file_io_cache);
}
/*
Initialize the slave IO_CACHE to read the same file (and data)
as master does.
One can create multiple slaves from a single master. Every slave and master
will have independent file positions.
The master must be a non-shared READ_CACHE.
It is assumed that no more reads are done after a master and/or a slave
has been freed (this limitation can be easily lifted).
*/
int init_slave_io_cache(IO_CACHE *master, IO_CACHE *slave)
{
uchar *slave_buf;
DBUG_ASSERT(master->type == READ_CACHE);
DBUG_ASSERT(!master->share);
DBUG_ASSERT(master->alloced_buffer);
if (!(slave_buf= (uchar*)my_malloc(PSI_INSTRUMENT_ME, master->alloced_buffer, MYF(0))))
{
return 1;
}
memcpy(slave, master, sizeof(IO_CACHE));
slave->buffer= slave_buf;
memcpy(slave->buffer, master->buffer, master->alloced_buffer);
slave->read_pos= slave->buffer + (master->read_pos - master->buffer);
slave->read_end= slave->buffer + (master->read_end - master->buffer);
if (master->next_file_user)
{
IO_CACHE *p;
for (p= master->next_file_user;
p->next_file_user !=master;
p= p->next_file_user)
{}
p->next_file_user= slave;
slave->next_file_user= master;
}
else
{
slave->next_file_user= master;
master->next_file_user= slave;
}
return 0;
}
void end_slave_io_cache(IO_CACHE *cache)
{
/* Remove the cache from the next_file_user circular linked list. */
if (cache->next_file_user != cache)
{
IO_CACHE *p= cache->next_file_user;
while (p->next_file_user != cache)
p= p->next_file_user;
p->next_file_user= cache->next_file_user;
}
my_free(cache->buffer);
}
/*
Seek a read io cache to a given offset
*/
void seek_io_cache(IO_CACHE *cache, my_off_t needed_offset)
{
my_off_t cached_data_start= cache->pos_in_file;
my_off_t cached_data_end= cache->pos_in_file + (cache->read_end -
cache->buffer);
if (needed_offset >= cached_data_start &&
needed_offset < cached_data_end)
{
/*
The offset we're seeking to is in the buffer.
Move buffer's read position accordingly
*/
cache->read_pos= cache->buffer + (needed_offset - cached_data_start);
}
else
{
if (needed_offset > cache->end_of_file)
needed_offset= cache->end_of_file;
/*
The offset we're seeking to is not in the buffer.
- Set the buffer to be exhausted.
- Make the next read to a mysql_file_seek() call to the required
offset.
TODO(cvicentiu, spetrunia) properly implement aligned seeks for
efficiency.
*/
cache->seek_not_done= 1;
cache->pos_in_file= needed_offset;
/* When reading it must appear as if we've started from the offset
that we've seeked here. We must let _my_b_cache_read assume that
by implying "no reading starting from pos_in_file" has happened. */
cache->read_pos= cache->buffer;
cache->read_end= cache->buffer;
}
}
/**
Use this to reset cache to re-start reading or to change the type
between READ_CACHE <-> WRITE_CACHE
If we are doing a reinit of a cache where we have the start of the file
in the cache, we are reusing this memory without flushing it to disk.
@param info IO_CACHE
@param type READ_CACHE or WRITE_CACHE
@param seek_offset Where to start reading or writing
@param use_async_io Not used
@param clear_cache 0 No clear, keep all information
1 truncate file. seek_offset has to be 0.
*/
my_bool reinit_io_cache(IO_CACHE *info, enum cache_type type,
my_off_t seek_offset,
my_bool use_async_io __attribute__((unused)),
my_bool clear_cache)
{
DBUG_ENTER("reinit_io_cache");
DBUG_PRINT("enter",("cache:%p type: %d seek_offset: %llu clear_cache: %d",
info, type, (ulonglong) seek_offset,
(int) clear_cache));
DBUG_ASSERT(type == READ_CACHE || type == WRITE_CACHE);
DBUG_ASSERT(info->type == READ_CACHE || info->type == WRITE_CACHE);
/* If the whole file is in memory, avoid flushing to disk */
if (! clear_cache &&
seek_offset >= info->pos_in_file &&
seek_offset <= my_b_tell(info))
{
/* Reuse current buffer without flushing it to disk */
uchar *pos;
if (info->type == WRITE_CACHE && type == READ_CACHE)
{
info->read_end=info->write_pos;
info->end_of_file=my_b_tell(info);
/*
Trigger a new seek only if we have a valid
file handle.
*/
info->seek_not_done= (info->file != -1);
}
else if (type == WRITE_CACHE)
{
if (info->type == READ_CACHE)
{
info->write_end=info->write_buffer+info->buffer_length;
info->seek_not_done=1;
}
info->end_of_file = ~(my_off_t) 0;
}
pos=info->request_pos+(seek_offset-info->pos_in_file);
if (type == WRITE_CACHE)
info->write_pos=pos;
else
info->read_pos= pos;
}
else
{
/*
If we change from WRITE_CACHE to READ_CACHE, assume that everything
after the current positions should be ignored. In other cases we
update end_of_file as it may have changed since last init.
*/
if (type == READ_CACHE)
{
if (info->type == WRITE_CACHE)
info->end_of_file= my_b_tell(info);
else
{
if (!(info->myflags & MY_ENCRYPT))
info->end_of_file= mysql_file_seek(info->file, 0L,
MY_SEEK_END, MYF(0));
}
}
/* flush cache if we want to reuse it */
if (!clear_cache && info->type == WRITE_CACHE)
{
int ret;
myf save_flags;
if (type == WRITE_CACHE && seek_offset > info->pos_in_file)
{
/* Write only up to where we will start next write */
my_off_t buffer_used= seek_offset - info->pos_in_file;
info->write_pos= info->write_buffer + buffer_used;
}
save_flags= info->myflags;
/* Allow temporary space over usage. Will be detected on next write */
info->myflags&= ~MY_TRACK_WITH_LIMIT;
ret= my_b_flush_io_cache(info,1);
info->myflags= save_flags;
if (ret)
DBUG_RETURN(ret);
}
info->pos_in_file=seek_offset;
/* Better to do always do a seek */
info->seek_not_done=1;
info->request_pos=info->read_pos=info->write_pos=info->buffer;
if (type == READ_CACHE)
{
info->read_end=info->buffer; /* Nothing in cache */
}
else
{
if (info->myflags & MY_ENCRYPT)
{
info->write_end = info->write_buffer + info->buffer_length;
if (seek_offset && info->file != -1)
{
info->read_end= info->buffer;
_my_b_encr_read(info, 0, 0); /* prefill the buffer */
info->write_pos= info->read_pos;
info->seek_not_done=1;
}
}
else
{
info->write_end=(info->buffer + info->buffer_length -
(seek_offset & (IO_SIZE-1)));
}
info->end_of_file= ~(my_off_t) 0;
}
}
info->type=type;
info->error=0;
init_functions(info);
DBUG_RETURN(0);
} /* reinit_io_cache */
int _my_b_read(IO_CACHE *info, uchar *Buffer, size_t Count)
{
size_t left_length;
int res;
/* If the buffer is not empty yet, copy what is available. */
if ((left_length= (size_t) (info->read_end - info->read_pos)))
{
DBUG_ASSERT(Count > left_length);
memcpy(Buffer, info->read_pos, left_length);
Buffer+=left_length;
Count-=left_length;
}
res= info->read_function(info, Buffer, Count);
if (res && info->error >= 0)
info->error+= (int)left_length; /* update number or read bytes */
return res;
}
int _my_b_write(IO_CACHE *info, const uchar *Buffer, size_t Count)
{
size_t rest_length;
int res;
/* Always use my_b_flush_io_cache() to flush write_buffer! */
DBUG_ASSERT(Buffer != info->write_buffer);
if (info->pos_in_file + info->buffer_length > info->end_of_file)
{
my_errno=errno=EFBIG;
return info->error = -1;
}
rest_length= (size_t) (info->write_end - info->write_pos);
DBUG_ASSERT(Count >= rest_length);
memcpy(info->write_pos, Buffer, (size_t) rest_length);
Buffer+=rest_length;
Count-=rest_length;
info->write_pos+=rest_length;
if (my_b_flush_io_cache(info, 1))
return 1;
if (Count)
{
my_off_t old_pos_in_file= info->pos_in_file;
res= info->write_function(info, Buffer, Count);
Count-= (size_t) (info->pos_in_file - old_pos_in_file);
Buffer+= info->pos_in_file - old_pos_in_file;
}
else
res= 0;
if (!res && Count)
{
memcpy(info->write_pos, Buffer, Count);
info->write_pos+= Count;
}
return res;
}
/*
Read buffered.
SYNOPSIS
_my_b_cache_read()
info IO_CACHE pointer
Buffer Buffer to retrieve count bytes from file
Count Number of bytes to read into Buffer
NOTE
This function is only called from the my_b_read() macro when there
isn't enough characters in the buffer to satisfy the request.
WARNING
When changing this function, be careful with handling file offsets
(end-of_file, pos_in_file). Do not cast them to possibly smaller
types than my_off_t unless you can be sure that their value fits.
Same applies to differences of file offsets.
When changing this function, check _my_b_cache_read_r(). It might need the
same change.
RETURN
0 we succeeded in reading all data
1 Error: couldn't read requested characters. In this case:
If info->error == -1, we got a read error.
Otherwise info->error contains the number of bytes in Buffer.
*/
int _my_b_cache_read(IO_CACHE *info, uchar *Buffer, size_t Count)
{
size_t length= 0, diff_length, left_length= 0, max_length;
my_off_t pos_in_file;
DBUG_ENTER("_my_b_cache_read");
/* pos_in_file always point on where info->buffer was read */
pos_in_file=info->pos_in_file+ (size_t) (info->read_end - info->buffer);
/*
Whenever a function which operates on IO_CACHE flushes/writes
some part of the IO_CACHE to disk it will set the property
"seek_not_done" to indicate this to other functions operating
on the IO_CACHE.
*/
if (info->seek_not_done)
{
if ((mysql_file_seek(info->file, pos_in_file, MY_SEEK_SET, MYF(0))
!= MY_FILEPOS_ERROR))
{
/* No error, reset seek_not_done flag. */
info->seek_not_done= 0;
if (info->next_file_user)
{
IO_CACHE *c;
for (c= info->next_file_user;
c!= info;
c= c->next_file_user)
{
c->seek_not_done= 1;
}
}
}
else
{
/*
If the seek failed and the error number is ESPIPE, it is because
info->file is a pipe or socket or FIFO. We never should have tried
to seek on that. See Bugs#25807 and #22828 for more info.
*/
DBUG_ASSERT(my_errno != ESPIPE);
info->error= -1;
DBUG_RETURN(1);
}
}
/*
Calculate, how much we are within a IO_SIZE block. Ideally this
should be zero.
*/
diff_length= (size_t) (pos_in_file & (IO_SIZE-1));
/*
If more than a block plus the rest of the current block is wanted,
we do read directly, without filling the buffer.
*/
if (Count >= (size_t) (IO_SIZE+(IO_SIZE-diff_length)))
{ /* Fill first intern buffer */
size_t read_length;
if (info->end_of_file <= pos_in_file)
{
/* End of file. Return, what we did copy from the buffer. */
info->error= (int) left_length;
info->seek_not_done=1;
DBUG_RETURN(1);
}
/*
Crop the wanted count to a multiple of IO_SIZE and subtract,
what we did already read from a block. That way, the read will
end aligned with a block.
*/
length= IO_ROUND_DN(Count) - diff_length;
if ((read_length= mysql_file_read(info->file,Buffer, length, info->myflags))
!= length)
{
/*
If we didn't get, what we wanted, we either return -1 for a read
error, or (it's end of file), how much we got in total.
*/
info->error= (read_length == (size_t) -1 ? -1 :
(int) (read_length+left_length));
info->seek_not_done=1;
DBUG_RETURN(1);
}
Count-=length;
Buffer+=length;
pos_in_file+=length;
left_length+=length;
diff_length=0;
}
/*
At this point, we want less than one and a partial block.
We will read a full cache, minus the number of bytes, we are
within a block already. So we will reach new alignment.
*/
max_length= info->read_length-diff_length;
/* We will not read past end of file. */
if (info->type != READ_FIFO &&
max_length > (info->end_of_file - pos_in_file))
max_length= (size_t) (info->end_of_file - pos_in_file);
/*
If there is nothing left to read,
we either are done, or we failed to fulfill the request.
Otherwise, we read max_length into the cache.
*/
if (!max_length)
{
if (Count)
{
/* We couldn't fulfil the request. Return, how much we got. */
info->error= (int) left_length;
DBUG_RETURN(1);
}
else
{
info->error= 0;
if (length == 0) /* nothing was read */
DBUG_RETURN(0); /* EOF */
length= 0; /* non-zero size read was done */
}
}
else
{
if (info->next_file_user)
{
IO_CACHE *c;
for (c= info->next_file_user;
c!= info;
c= c->next_file_user)
{
c->seek_not_done= 1;
}
}
if ((length= mysql_file_read(info->file,info->buffer, max_length,
info->myflags)) < Count ||
length == (size_t) -1)
{
/*
We got an read error, or less than requested (end of file).
If not a read error, copy, what we got.
*/
if (length != (size_t) -1)
memcpy(Buffer, info->buffer, length);
info->pos_in_file= pos_in_file;
/* For a read error, return -1, otherwise, what we got in total. */
info->error= length == (size_t) -1 ? -1 : (int) (length+left_length);
info->read_pos=info->read_end=info->buffer;
info->seek_not_done=1;
DBUG_RETURN(1);
}
}
/*
Count is the remaining number of bytes requested.
length is the amount of data in the cache.
Read Count bytes from the cache.
*/
info->read_pos=info->buffer+Count;
info->read_end=info->buffer+length;
info->pos_in_file=pos_in_file;
if (Count)
memcpy(Buffer, info->buffer, Count);
DBUG_RETURN(0);
}
/*
Prepare IO_CACHE for shared use.
SYNOPSIS
init_io_cache_share()
read_cache A read cache. This will be copied for
every thread after setup.
cshare The share.
write_cache If non-NULL a write cache that is to be
synchronized with the read caches.
num_threads Number of threads sharing the cache
including the write thread if any.
DESCRIPTION
The shared cache is used so: One IO_CACHE is initialized with
init_io_cache(). This includes the allocation of a buffer. Then a
share is allocated and init_io_cache_share() is called with the io
cache and the share. Then the io cache is copied for each thread. So
every thread has its own copy of IO_CACHE. But the allocated buffer
is shared because cache->buffer is the same for all caches.
One thread reads data from the file into the buffer. All threads
read from the buffer, but every thread maintains its own set of
pointers into the buffer. When all threads have used up the buffer
contents, one of the threads reads the next block of data into the
buffer. To accomplish this, each thread enters the cache lock before
accessing the buffer. They wait in lock_io_cache() until all threads
joined the lock. The last thread entering the lock is in charge of
reading from file to buffer. It wakes all threads when done.
Synchronizing a write cache to the read caches works so: Whenever
the write buffer needs a flush, the write thread enters the lock and
waits for all other threads to enter the lock too. They do this when
they have used up the read buffer. When all threads are in the lock,
the write thread copies the write buffer to the read buffer and
wakes all threads.
share->running_threads is the number of threads not being in the
cache lock. When entering lock_io_cache() the number is decreased.
When the thread that fills the buffer enters unlock_io_cache() the
number is reset to the number of threads. The condition
running_threads == 0 means that all threads are in the lock. Bumping
up the number to the full count is non-intuitive. But increasing the
number by one for each thread that leaves the lock could lead to a
solo run of one thread. The last thread to join a lock reads from
file to buffer, wakes the other threads, processes the data in the
cache and enters the lock again. If no other thread left the lock
meanwhile, it would think it's the last one again and read the next
block...
The share has copies of 'error', 'buffer', 'read_end', and
'pos_in_file' from the thread that filled the buffer. We may not be
able to access this information directly from its cache because the
thread may be removed from the share before the variables could be
copied by all other threads. Or, if a write buffer is synchronized,
it would change its 'pos_in_file' after waking the other threads,
possibly before they could copy its value.
However, the 'buffer' variable in the share is for a synchronized
write cache. It needs to know where to put the data. Otherwise it
would need access to the read cache of one of the threads that is
not yet removed from the share.
RETURN
void
*/
void init_io_cache_share(IO_CACHE *read_cache, IO_CACHE_SHARE *cshare,
IO_CACHE *write_cache, uint num_threads)
{
DBUG_ENTER("init_io_cache_share");
DBUG_PRINT("io_cache_share", ("read_cache: %p share: %p "
"write_cache: %p threads: %u",
read_cache, cshare,
write_cache, num_threads));
DBUG_ASSERT(num_threads > 1);
DBUG_ASSERT(read_cache->type == READ_CACHE);
DBUG_ASSERT(!write_cache || (write_cache->type == WRITE_CACHE));
mysql_mutex_init(key_IO_CACHE_SHARE_mutex,
&cshare->mutex, MY_MUTEX_INIT_FAST);
mysql_cond_init(key_IO_CACHE_SHARE_cond, &cshare->cond, 0);
mysql_cond_init(key_IO_CACHE_SHARE_cond_writer, &cshare->cond_writer, 0);
cshare->running_threads= num_threads;
cshare->total_threads= num_threads;
cshare->error= 0; /* Initialize. */
cshare->buffer= read_cache->buffer;
cshare->read_end= NULL; /* See function comment of lock_io_cache(). */
cshare->pos_in_file= 0; /* See function comment of lock_io_cache(). */
cshare->source_cache= write_cache; /* Can be NULL. */
read_cache->share= cshare;
read_cache->read_function= _my_b_cache_read_r;
if (write_cache)
{
write_cache->share= cshare;
write_cache->write_function= _my_b_cache_write_r;
}
DBUG_VOID_RETURN;
}
/*
Remove a thread from shared access to IO_CACHE.
SYNOPSIS
remove_io_thread()
cache The IO_CACHE to be removed from the share.
NOTE
Every thread must do that on exit for not to deadlock other threads.
The last thread destroys the pthread resources.
A writer flushes its cache first.
RETURN
void
*/
void remove_io_thread(IO_CACHE *cache)
{
IO_CACHE_SHARE *cshare= cache->share;
uint total;
DBUG_ENTER("remove_io_thread");
/* If the writer goes, it needs to flush the write cache. */
if (cache == cshare->source_cache)
flush_io_cache(cache);
mysql_mutex_lock(&cshare->mutex);
DBUG_PRINT("io_cache_share", ("%s: %p",
(cache == cshare->source_cache) ?
"writer" : "reader", cache));
/* Remove from share. */
total= --cshare->total_threads;
DBUG_PRINT("io_cache_share", ("remaining threads: %u", total));
/* Detach from share. */
cache->share= NULL;
/* If the writer goes, let the readers know. */
if (cache == cshare->source_cache)
{
DBUG_PRINT("io_cache_share", ("writer leaves"));
cshare->source_cache= NULL;
}
/* If all threads are waiting for me to join the lock, wake them. */
if (!--cshare->running_threads)
{
DBUG_PRINT("io_cache_share", ("the last running thread leaves, wake all"));
mysql_cond_signal(&cshare->cond_writer);
mysql_cond_broadcast(&cshare->cond);
}
mysql_mutex_unlock(&cshare->mutex);
if (!total)
{
DBUG_PRINT("io_cache_share", ("last thread removed, destroy share"));
mysql_cond_destroy (&cshare->cond_writer);
mysql_cond_destroy (&cshare->cond);
mysql_mutex_destroy(&cshare->mutex);
}
DBUG_VOID_RETURN;
}
/*
Lock IO cache and wait for all other threads to join.
SYNOPSIS
lock_io_cache()
cache The cache of the thread entering the lock.
pos File position of the block to read.
Unused for the write thread.
DESCRIPTION
Wait for all threads to finish with the current buffer. We want
all threads to proceed in concert. The last thread to join
lock_io_cache() will read the block from file and all threads start
to use it. Then they will join again for reading the next block.
The waiting threads detect a fresh buffer by comparing
cshare->pos_in_file with the position they want to process next.
Since the first block may start at position 0, we take
cshare->read_end as an additional condition. This variable is
initialized to NULL and will be set after a block of data is written
to the buffer.
RETURN
1 OK, lock in place, go ahead and read.
0 OK, unlocked, another thread did the read.
*/
static int lock_io_cache(IO_CACHE *cache, my_off_t pos)
{
IO_CACHE_SHARE *cshare= cache->share;
DBUG_ENTER("lock_io_cache");
/* Enter the lock. */
mysql_mutex_lock(&cshare->mutex);
cshare->running_threads--;
DBUG_PRINT("io_cache_share", ("%s: %p pos: %lu running: %u",
(cache == cshare->source_cache) ?
"writer" : "reader", cache, (ulong) pos,
cshare->running_threads));
if (cshare->source_cache)
{
/* A write cache is synchronized to the read caches. */
if (cache == cshare->source_cache)
{
/* The writer waits until all readers are here. */
while (cshare->running_threads)
{
DBUG_PRINT("io_cache_share", ("writer waits in lock"));
mysql_cond_wait(&cshare->cond_writer, &cshare->mutex);
}
DBUG_PRINT("io_cache_share", ("writer awoke, going to copy"));
/* Stay locked. Leave the lock later by unlock_io_cache(). */
DBUG_RETURN(1);
}
/* The last thread wakes the writer. */
if (!cshare->running_threads)
{
DBUG_PRINT("io_cache_share", ("waking writer"));
mysql_cond_signal(&cshare->cond_writer);
}
/*
Readers wait until the data is copied from the writer. Another
reason to stop waiting is the removal of the write thread. If this
happens, we leave the lock with old data in the buffer.
*/
while ((!cshare->read_end || (cshare->pos_in_file < pos)) &&
cshare->source_cache)
{
DBUG_PRINT("io_cache_share", ("reader waits in lock"));
mysql_cond_wait(&cshare->cond, &cshare->mutex);
}
/*
If the writer was removed from the share while this thread was
asleep, we need to simulate an EOF condition. The writer cannot
reset the share variables as they might still be in use by readers
of the last block. When we awake here then because the last
joining thread signalled us. If the writer is not the last, it
will not signal. So it is safe to clear the buffer here.
*/
if (!cshare->read_end || (cshare->pos_in_file < pos))
{
DBUG_PRINT("io_cache_share", ("reader found writer removed. EOF"));
cshare->read_end= cshare->buffer; /* Empty buffer. */
cshare->error= 0; /* EOF is not an error. */
}
}
else
{
/*
There are read caches only. The last thread arriving in
lock_io_cache() continues with a locked cache and reads the block.
*/
if (!cshare->running_threads)
{
DBUG_PRINT("io_cache_share", ("last thread joined, going to read"));
/* Stay locked. Leave the lock later by unlock_io_cache(). */
DBUG_RETURN(1);
}
/*
All other threads wait until the requested block is read by the
last thread arriving. Another reason to stop waiting is the
removal of a thread. If this leads to all threads being in the
lock, we have to continue also. The first of the awaken threads
will then do the read.
*/
while ((!cshare->read_end || (cshare->pos_in_file < pos)) &&
cshare->running_threads)
{
DBUG_PRINT("io_cache_share", ("reader waits in lock"));
mysql_cond_wait(&cshare->cond, &cshare->mutex);
}
/* If the block is not yet read, continue with a locked cache and read. */
if (!cshare->read_end || (cshare->pos_in_file < pos))
{
DBUG_PRINT("io_cache_share", ("reader awoke, going to read"));
/* Stay locked. Leave the lock later by unlock_io_cache(). */
DBUG_RETURN(1);
}
/* Another thread did read the block already. */
}
DBUG_PRINT("io_cache_share", ("reader awoke, going to process %u bytes",
(uint) (cshare->read_end ? (size_t)
(cshare->read_end - cshare->buffer) :
0)));
/*
Leave the lock. Do not call unlock_io_cache() later. The thread that
filled the buffer did this and marked all threads as running.
*/
mysql_mutex_unlock(&cshare->mutex);
DBUG_RETURN(0);
}
/*
Unlock IO cache.
SYNOPSIS
unlock_io_cache()
cache The cache of the thread leaving the lock.
NOTE
This is called by the thread that filled the buffer. It marks all
threads as running and awakes them. This must not be done by any
other thread.
Do not signal cond_writer. Either there is no writer or the writer
is the only one who can call this function.
The reason for resetting running_threads to total_threads before
waking all other threads is that it could be possible that this
thread is so fast with processing the buffer that it enters the lock
before even one other thread has left it. If every awoken thread
would increase running_threads by one, this thread could think that
he is again the last to join and would not wait for the other
threads to process the data.
RETURN
void
*/
static void unlock_io_cache(IO_CACHE *cache)
{
IO_CACHE_SHARE *cshare= cache->share;
DBUG_ENTER("unlock_io_cache");
DBUG_PRINT("io_cache_share", ("%s: %p pos: %lu running: %u",
(cache == cshare->source_cache) ?
"writer" : "reader",
cache, (ulong) cshare->pos_in_file,
cshare->total_threads));
cshare->running_threads= cshare->total_threads;
mysql_cond_broadcast(&cshare->cond);
mysql_mutex_unlock(&cshare->mutex);
DBUG_VOID_RETURN;
}
/*
Read from IO_CACHE when it is shared between several threads.
SYNOPSIS
_my_b_cache_read_r()
cache IO_CACHE pointer
Buffer Buffer to retrieve count bytes from file
Count Number of bytes to read into Buffer
NOTE
This function is only called from the my_b_read() macro when there
isn't enough characters in the buffer to satisfy the request.
IMPLEMENTATION
It works as follows: when a thread tries to read from a file (that
is, after using all the data from the (shared) buffer), it just
hangs on lock_io_cache(), waiting for other threads. When the very
last thread attempts a read, lock_io_cache() returns 1, the thread
does actual IO and unlock_io_cache(), which signals all the waiting
threads that data is in the buffer.
WARNING
When changing this function, be careful with handling file offsets
(end-of_file, pos_in_file). Do not cast them to possibly smaller
types than my_off_t unless you can be sure that their value fits.
Same applies to differences of file offsets. (Bug #11527)
When changing this function, check _my_b_cache_read(). It might need the
same change.
RETURN
0 we succeeded in reading all data
1 Error: can't read requested characters
*/
static int _my_b_cache_read_r(IO_CACHE *cache, uchar *Buffer, size_t Count)
{
my_off_t pos_in_file;
size_t length, diff_length, left_length= 0;
IO_CACHE_SHARE *cshare= cache->share;
DBUG_ENTER("_my_b_cache_read_r");
DBUG_ASSERT(!(cache->myflags & MY_ENCRYPT));
while (Count)
{
size_t cnt, len;
pos_in_file= cache->pos_in_file + (cache->read_end - cache->buffer);
diff_length= (size_t) (pos_in_file & (IO_SIZE-1));
length=IO_ROUND_UP(Count+diff_length)-diff_length;
length= ((length <= cache->read_length) ?
length + IO_ROUND_DN(cache->read_length - length) :
length - IO_ROUND_UP(length - cache->read_length));
if (cache->type != READ_FIFO &&
(length > (cache->end_of_file - pos_in_file)))
length= (size_t) (cache->end_of_file - pos_in_file);
if (length == 0)
{
cache->error= (int) left_length;
DBUG_RETURN(1);
}
if (lock_io_cache(cache, pos_in_file))
{
/* With a synchronized write/read cache we won't come here... */
DBUG_ASSERT(!cshare->source_cache);
/*
... unless the writer has gone before this thread entered the
lock. Simulate EOF in this case. It can be distinguished by
cache->file.
*/
if (cache->file < 0)
len= 0;
else
{
/*
Whenever a function which operates on IO_CACHE flushes/writes
some part of the IO_CACHE to disk it will set the property
"seek_not_done" to indicate this to other functions operating
on the IO_CACHE.
*/
if (cache->seek_not_done)
{
if (mysql_file_seek(cache->file, pos_in_file, MY_SEEK_SET, MYF(0))
== MY_FILEPOS_ERROR)
{
cache->error= -1;
unlock_io_cache(cache);
DBUG_RETURN(1);
}
}
len= mysql_file_read(cache->file, cache->buffer, length, cache->myflags);
}
DBUG_PRINT("io_cache_share", ("read %lu bytes", (ulong) len));
cache->read_end= cache->buffer + (len == (size_t) -1 ? 0 : len);
cache->error= (len == length ? 0 : (int) len);
cache->pos_in_file= pos_in_file;
/* Copy important values to the share. */
cshare->error= cache->error;
cshare->read_end= cache->read_end;
cshare->pos_in_file= pos_in_file;
/* Mark all threads as running and wake them. */
unlock_io_cache(cache);
}
else
{
/*
With a synchronized write/read cache readers always come here.
Copy important values from the share.
*/
cache->error= cshare->error;
cache->read_end= cshare->read_end;
cache->pos_in_file= cshare->pos_in_file;
len= ((cache->error == -1) ? (size_t) -1 :
(size_t) (cache->read_end - cache->buffer));
}
cache->read_pos= cache->buffer;
cache->seek_not_done= 0;
if (len == 0 || len == (size_t) -1)
{
DBUG_PRINT("io_cache_share", ("reader error. len %lu left %lu",
(ulong) len, (ulong) left_length));
cache->error= (int) left_length;
DBUG_RETURN(1);
}
cnt= (len > Count) ? Count : len;
if (cnt)
memcpy(Buffer, cache->read_pos, cnt);
Count -= cnt;
Buffer+= cnt;
left_length+= cnt;
cache->read_pos+= cnt;
}
DBUG_RETURN(0);
}
/*
Copy data from write cache to read cache.
SYNOPSIS
copy_to_read_buffer()
write_cache The write cache.
write_buffer The source of data, mostly the cache buffer.
write_length The number of bytes to copy.
NOTE
The write thread will wait for all read threads to join the cache
lock. Then it copies the data over and wakes the read threads.
RETURN
void
*/
static void copy_to_read_buffer(IO_CACHE *write_cache,
const uchar *write_buffer, my_off_t pos_in_file)
{
size_t write_length= (size_t) (write_cache->pos_in_file - pos_in_file);
IO_CACHE_SHARE *cshare= write_cache->share;
DBUG_ASSERT(cshare->source_cache == write_cache);
/*
write_length is usually less or equal to buffer_length.
It can be bigger if _my_b_cache_write_r() is called with a big length.
*/
while (write_length)
{
size_t copy_length= MY_MIN(write_length, write_cache->buffer_length);
int __attribute__((unused)) rc;
rc= lock_io_cache(write_cache, pos_in_file);
/* The writing thread does always have the lock when it awakes. */
DBUG_ASSERT(rc);
memcpy(cshare->buffer, write_buffer, copy_length);
cshare->error= 0;
cshare->read_end= cshare->buffer + copy_length;
cshare->pos_in_file= pos_in_file;
/* Mark all threads as running and wake them. */
unlock_io_cache(write_cache);
write_buffer+= copy_length;
write_length-= copy_length;
}
}
/*
Do sequential read from the SEQ_READ_APPEND cache.
We do this in three stages:
- first read from info->buffer
- then if there are still data to read, try the file descriptor
- afterwards, if there are still data to read, try append buffer
RETURNS
0 Success
1 Failed to read
*/
static int _my_b_seq_read(IO_CACHE *info, uchar *Buffer, size_t Count)
{
size_t length, diff_length, save_count, max_length;
my_off_t pos_in_file;
save_count=Count;
lock_append_buffer(info);
/* pos_in_file always point on where info->buffer was read */
if ((pos_in_file=info->pos_in_file +
(size_t) (info->read_end - info->buffer)) >= info->end_of_file)
goto read_append_buffer;
/*
With read-append cache we must always do a seek before we read,
because the write could have moved the file pointer astray
*/
if (mysql_file_seek(info->file, pos_in_file, MY_SEEK_SET, MYF(0)) == MY_FILEPOS_ERROR)
{
info->error= -1;
unlock_append_buffer(info);
return (1);
}
info->seek_not_done=0;
diff_length= (size_t) (pos_in_file & (IO_SIZE-1));
/* now the second stage begins - read from file descriptor */
if (Count >= (size_t) (IO_SIZE+(IO_SIZE-diff_length)))
{
/* Fill first intern buffer */
size_t read_length;
length= IO_ROUND_DN(Count) - diff_length;
if ((read_length= mysql_file_read(info->file,Buffer, length,
info->myflags)) == (size_t) -1)
{
info->error= -1;
unlock_append_buffer(info);
return 1;
}
Count-=read_length;
Buffer+=read_length;
pos_in_file+=read_length;
if (read_length != length)
{
/*
We only got part of data; Read the rest of the data from the
write buffer
*/
goto read_append_buffer;
}
diff_length=0;
}
max_length= info->read_length-diff_length;
if (max_length > (info->end_of_file - pos_in_file))
max_length= (size_t) (info->end_of_file - pos_in_file);
if (!max_length)
{
if (Count)
goto read_append_buffer;
length=0; /* Didn't read any more chars */
}
else
{
length= mysql_file_read(info->file,info->buffer, max_length, info->myflags);
if (length == (size_t) -1)
{
info->error= -1;
unlock_append_buffer(info);
return 1;
}
if (length < Count)
{
memcpy(Buffer, info->buffer, length);
Count -= length;
Buffer += length;
/*
added the line below to make
DBUG_ASSERT(pos_in_file==info->end_of_file) pass.
otherwise this does not appear to be needed
*/
pos_in_file += length;
goto read_append_buffer;
}
}
unlock_append_buffer(info);
info->read_pos=info->buffer+Count;
info->read_end=info->buffer+length;
info->pos_in_file=pos_in_file;
memcpy(Buffer,info->buffer,(size_t) Count);
return 0;
read_append_buffer:
/*
Read data from the current write buffer.
Count should never be == 0 here (The code will work even if count is 0)
*/
{
/* First copy the data to Count */
size_t len_in_buff = (size_t) (info->write_pos - info->append_read_pos);
size_t copy_len;
size_t transfer_len;
DBUG_ASSERT(info->append_read_pos <= info->write_pos);
copy_len=MY_MIN(Count, len_in_buff);
memcpy(Buffer, info->append_read_pos, copy_len);
info->append_read_pos += copy_len;
Count -= copy_len;
if (Count)
info->error= (int) (save_count - Count);
/* Fill read buffer with data from write buffer */
memcpy(info->buffer, info->append_read_pos,
(size_t) (transfer_len=len_in_buff - copy_len));
info->read_pos= info->buffer;
info->read_end= info->buffer+transfer_len;
info->append_read_pos=info->write_pos;
info->pos_in_file=pos_in_file+copy_len;
info->end_of_file+=len_in_buff;
}
unlock_append_buffer(info);
return Count ? 1 : 0;
}
/* Read one byte when buffer is empty */
int _my_b_get(IO_CACHE *info)
{
uchar buff;
if ((*(info)->read_function)(info,&buff,1))
return my_b_EOF;
return (int) (uchar) buff;
}
/*
Write a byte buffer to IO_CACHE and flush to disk
if IO_CACHE is full.
RETURN VALUE
1 On error on write
0 On success
-1 On error; my_errno contains error code.
*/
int _my_b_cache_write(IO_CACHE *info, const uchar *Buffer, size_t Count)
{
if (Buffer != info->write_buffer)
{
Count= IO_ROUND_DN(Count);
if (!Count)
return 0;
}
if (info->seek_not_done)
{
/*
Whenever a function which operates on IO_CACHE flushes/writes
some part of the IO_CACHE to disk it will set the property
"seek_not_done" to indicate this to other functions operating
on the IO_CACHE.
*/
if (mysql_file_seek(info->file, info->pos_in_file, MY_SEEK_SET,
MYF(info->myflags & MY_WME)) == MY_FILEPOS_ERROR)
{
info->error= -1;
return 1;
}
info->seek_not_done=0;
}
if (tmp_file_track(info, info->pos_in_file + Count) ||
mysql_file_write(info->file, Buffer, Count, info->myflags | MY_NABP))
return info->error= -1;
info->pos_in_file+= Count;
return 0;
}
/*
In case of a shared I/O cache with a writer we normally do direct
write cache to read cache copy. Simulate this here by direct
caller buffer to read cache copy. Do it after the write so that
the cache readers actions on the flushed part can go in parallel
with the write of the extra stuff. copy_to_read_buffer()
synchronizes writer and readers so that after this call the
readers can act on the extra stuff while the writer can go ahead
and prepare the next output. copy_to_read_buffer() relies on
info->pos_in_file.
*/
static int _my_b_cache_write_r(IO_CACHE *info, const uchar *Buffer, size_t Count)
{
my_off_t old_pos_in_file= info->pos_in_file;
int res= _my_b_cache_write(info, Buffer, Count);
if (res)
return res;
DBUG_ASSERT(!(info->myflags & MY_ENCRYPT));
DBUG_ASSERT(info->share);
copy_to_read_buffer(info, Buffer, old_pos_in_file);
return 0;
}
/*
Append a block to the write buffer.
This is done with the buffer locked to ensure that we don't read from
the write buffer before we are ready with it.
*/
int my_b_append(IO_CACHE *info, const uchar *Buffer, size_t Count)
{
size_t rest_length,length;
MEM_CHECK_DEFINED(Buffer, Count);
/*
Assert that we cannot come here with a shared cache. If we do one
day, we might need to add a call to copy_to_read_buffer().
*/
DBUG_ASSERT(!info->share);
DBUG_ASSERT(!(info->myflags & MY_ENCRYPT));
lock_append_buffer(info);
rest_length= (size_t) (info->write_end - info->write_pos);
if (Count <= rest_length)
goto end;
memcpy(info->write_pos, Buffer, rest_length);
Buffer+=rest_length;
Count-=rest_length;
info->write_pos+=rest_length;
if (my_b_flush_io_cache(info,0))
{
unlock_append_buffer(info);
return 1;
}
if (Count >= IO_SIZE)
{ /* Fill first intern buffer */
length= IO_ROUND_DN(Count);
if (tmp_file_track(info, info->end_of_file + length) ||
mysql_file_write(info->file,Buffer, length, info->myflags | MY_NABP))
{
unlock_append_buffer(info);
return info->error= -1;
}
Count-=length;
Buffer+=length;
info->end_of_file+=length;
}
end:
memcpy(info->write_pos,Buffer,(size_t) Count);
info->write_pos+=Count;
unlock_append_buffer(info);
return 0;
}
int my_b_safe_write(IO_CACHE *info, const uchar *Buffer, size_t Count)
{
/*
Sasha: We are not writing this with the ? operator to avoid hitting
a possible compiler bug. At least gcc 2.95 cannot deal with
several layers of ternary operators that evaluated comma(,) operator
expressions inside - I do have a test case if somebody wants it
*/
if (info->type == SEQ_READ_APPEND)
return my_b_append(info, Buffer, Count);
return my_b_write(info, Buffer, Count);
}
/*
Write a block to disk where part of the data may be inside the record
buffer. As all write calls to the data goes through the cache,
we will never get a seek over the end of the buffer
*/
int my_block_write(IO_CACHE *info, const uchar *Buffer, size_t Count,
my_off_t pos)
{
size_t length;
int error=0;
/*
Assert that we cannot come here with a shared cache. If we do one
day, we might need to add a call to copy_to_read_buffer().
*/
DBUG_ASSERT(!info->share);
DBUG_ASSERT(!(info->myflags & MY_ENCRYPT));
if (pos < info->pos_in_file)
{
/* Of no overlap, write everything without buffering */
if (pos + Count <= info->pos_in_file)
return (int)mysql_file_pwrite(info->file, Buffer, Count, pos,
info->myflags | MY_NABP);
/* Write the part of the block that is before buffer */
length= (uint) (info->pos_in_file - pos);
if (mysql_file_pwrite(info->file, Buffer, length, pos, info->myflags | MY_NABP))
info->error= error= -1;
Buffer+=length;
pos+= length;
Count-= length;
}
/* Check if we want to write inside the used part of the buffer.*/
length= (size_t) (info->write_end - info->buffer);
if (pos < info->pos_in_file + length)
{
size_t offset= (size_t) (pos - info->pos_in_file);
length-=offset;
if (length > Count)
length=Count;
memcpy(info->buffer+offset, Buffer, length);
Buffer+=length;
Count-= length;
/* Fix length of buffer if the new data was larger */
if (info->buffer+length > info->write_pos)
info->write_pos=info->buffer+length;
if (!Count)
return (error);
}
/* Write at the end of the current buffer; This is the normal case */
if (_my_b_write(info, Buffer, Count))
error= -1;
return error;
}
/* Flush write cache */
#define LOCK_APPEND_BUFFER if (need_append_buffer_lock) \
lock_append_buffer(info);
#define UNLOCK_APPEND_BUFFER if (need_append_buffer_lock) \
unlock_append_buffer(info);
int my_b_flush_io_cache(IO_CACHE *info, int need_append_buffer_lock)
{
size_t length;
my_bool append_cache= (info->type == SEQ_READ_APPEND);
DBUG_ENTER("my_b_flush_io_cache");
DBUG_PRINT("enter", ("cache: %p", info));
if (!append_cache)
need_append_buffer_lock= 0;
if (info->type == WRITE_CACHE || append_cache)
{
if (info->file == -1)
{
if (real_open_cached_file(info))
DBUG_RETURN((info->error= -1));
}
LOCK_APPEND_BUFFER;
if ((length=(size_t) (info->write_pos - info->write_buffer)))
{
my_off_t eof= info->end_of_file + info->write_pos - info->append_read_pos;
if (append_cache)
{
if (tmp_file_track(info, eof) ||
mysql_file_write(info->file, info->write_buffer, length,
info->myflags | MY_NABP))
{
UNLOCK_APPEND_BUFFER;
info->error= -1;
DBUG_RETURN(-1);
}
info->end_of_file= eof;
info->append_read_pos= info->write_buffer;
DBUG_ASSERT(info->end_of_file == mysql_file_tell(info->file, MYF(0)));
}
else
{
int res= info->write_function(info, info->write_buffer, length);
if (res)
{
UNLOCK_APPEND_BUFFER;
DBUG_RETURN(res);
}
set_if_bigger(info->end_of_file, info->pos_in_file);
}
info->write_end= (info->write_buffer + info->buffer_length -
((info->pos_in_file + length) & (IO_SIZE - 1)));
info->write_pos= info->write_buffer;
++info->disk_writes;
UNLOCK_APPEND_BUFFER;
DBUG_RETURN(0);
}
}
UNLOCK_APPEND_BUFFER;
DBUG_RETURN(0);
}
/*
Free an IO_CACHE object
SYNOPSOS
end_io_cache()
info IO_CACHE Handle to free
NOTES
It's currently safe to call this if one has called init_io_cache()
on the 'info' object, even if init_io_cache() failed.
This function is also safe to call twice with the same handle.
Note that info->file is not reset as the caller may still use ut for my_close()
RETURN
0 ok
# Error
*/
int end_io_cache(IO_CACHE *info)
{
int error=0;
DBUG_ENTER("end_io_cache");
DBUG_PRINT("enter",("cache: %p", info));
/*
Every thread must call remove_io_thread(). The last one destroys
the share elements.
*/
DBUG_ASSERT(!info->share || !info->share->total_threads);
if (info->alloced_buffer)
{
info->alloced_buffer=0;
if (info->file != -1) /* File doesn't exist */
error= my_b_flush_io_cache(info,1);
my_free(info->buffer);
info->buffer=info->read_pos=(uchar*) 0;
}
if (info->type == SEQ_READ_APPEND)
{
/* Destroy allocated mutex */
mysql_mutex_destroy(&info->append_buffer_lock);
}
reset_tracking_io_cache(info);
info->share= 0;
info->type= TYPE_NOT_SET; /* Ensure that flush_io_cache() does nothing */
info->write_end= 0; /* Ensure that my_b_write() fails */
info->write_function= 0; /* my_b_write will crash if used */
DBUG_RETURN(error);
} /* end_io_cache */
/**********************************************************************
Testing of MF_IOCACHE
**********************************************************************/
#ifdef MAIN
#include <my_dir.h>
void die(const char* fmt, ...)
{
va_list va_args;
va_start(va_args,fmt);
fprintf(stderr,"Error:");
vfprintf(stderr, fmt,va_args);
fprintf(stderr,", errno=%d\n", errno);
va_end(va_args);
exit(1);
}
int open_file(const char* fname, IO_CACHE* info, int cache_size)
{
int fd;
if ((fd=my_open(fname,O_CREAT | O_RDWR,MYF(MY_WME))) < 0)
die("Could not open %s", fname);
if (init_io_cache(info, fd, cache_size, SEQ_READ_APPEND, 0,0,MYF(MY_WME)))
die("failed in init_io_cache()");
return fd;
}
void close_file(IO_CACHE* info)
{
end_io_cache(info);
my_close(info->file, MYF(MY_WME));
}
int main(int argc, char** argv)
{
IO_CACHE sra_cache; /* SEQ_READ_APPEND */
MY_STAT status;
const char* fname="/tmp/iocache.test";
int cache_size=16384;
char llstr_buf[22];
int max_block,total_bytes=0;
int i,num_loops=100,error=0;
char *p;
char* block, *block_end;
MY_INIT(argv[0]);
max_block = cache_size*3;
if (!(block=(char*)my_malloc(max_block,MYF(MY_WME))))
die("Not enough memory to allocate test block");
block_end = block + max_block;
for (p = block,i=0; p < block_end;i++)
{
*p++ = (char)i;
}
if (my_stat(fname,&status, MYF(0)) &&
my_delete(fname,MYF(MY_WME)))
{
die("Delete of %s failed, aborting", fname);
}
open_file(fname,&sra_cache, cache_size);
for (i = 0; i < num_loops; i++)
{
char buf[4];
int block_size = abs(rand() % max_block);
int4store(buf, block_size);
if (my_b_append(&sra_cache,buf,4) ||
my_b_append(&sra_cache, block, block_size))
die("write failed");
total_bytes += 4+block_size;
}
close_file(&sra_cache);
my_free(block);
if (!my_stat(fname,&status,MYF(MY_WME)))
die("%s failed to stat, but I had just closed it,\
wonder how that happened");
printf("Final size of %s is %s, wrote %d bytes\n",fname,
llstr(status.st_size,llstr_buf),
total_bytes);
my_delete(fname, MYF(MY_WME));
/* check correctness of tests */
if (total_bytes != status.st_size)
{
fprintf(stderr,"Not the same number of bytes actually in file as bytes \
supposedly written\n");
error=1;
}
exit(error);
return 0;
}
#endif
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