diff options
Diffstat (limited to 'mysys/mf_iocache.c')
| -rw-r--r-- | mysys/mf_iocache.c | 1886 |
1 files changed, 1886 insertions, 0 deletions
diff --git a/mysys/mf_iocache.c b/mysys/mf_iocache.c new file mode 100644 index 00000000..3eaf1580 --- /dev/null +++ b/mysys/mf_iocache.c @@ -0,0 +1,1886 @@ +/* + 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 */ + +/* + Cashing 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 exeeds 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; + +#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 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) +{ + 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; + + 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. +*/ + +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 && my_b_flush_io_cache(info,1)) + DBUG_RETURN(1); + 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 (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 (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))) + { + if (append_cache) + { + if (mysql_file_write(info->file, info->write_buffer, length, + info->myflags | MY_NABP)) + { + info->error= -1; + DBUG_RETURN(-1); + } + info->end_of_file+= info->write_pos - info->append_read_pos; + 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) + 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(info->error); + } + } + 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); + } + 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 |