diff options
Diffstat (limited to 'isam/_cache.c')
| -rw-r--r-- | isam/_cache.c | 92 |
1 files changed, 92 insertions, 0 deletions
diff --git a/isam/_cache.c b/isam/_cache.c new file mode 100644 index 00000000000..53619126660 --- /dev/null +++ b/isam/_cache.c @@ -0,0 +1,92 @@ +/* Copyright (C) 2000 MySQL AB & MySQL Finland AB & TCX DataKonsult AB + + 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; either version 2 of the License, or + (at your option) any later version. + + 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */ + +/* Functions for read record cacheing with nisam */ +/* Used instead of my_b_read() to allow for no-cacheed seeks */ + +#include "isamdef.h" + +#define READING_NEXT 1 +#define READING_HEADER 2 + + /* Copy block from cache if it`s in it. If re_read_if_possibly is */ + /* set read to cache (if after current file-position) else read to */ + /* buff */ + +int _nisam_read_cache(IO_CACHE *info, byte *buff, ulong pos, uint length, + int flag) +{ + uint read_length,in_buff_length; + ulong offset; + char *in_buff_pos; + + if (pos < info->pos_in_file) + { + read_length= (uint) min((ulong) length,(ulong) (info->pos_in_file-pos)); + info->seek_not_done=1; + VOID(my_seek(info->file,pos,MY_SEEK_SET,MYF(0))); + if (my_read(info->file,buff,read_length,MYF(MY_NABP))) + return 1; + if (!(length-=read_length)) + return 0; + pos+=read_length; + buff+=read_length; + } + if ((offset=pos - (ulong) info->pos_in_file) < + (ulong) (info->rc_end - info->rc_request_pos)) + { + in_buff_pos=info->rc_request_pos+(uint) offset; + in_buff_length= min(length,(uint) (info->rc_end-in_buff_pos)); + memcpy(buff,info->rc_request_pos+(uint) offset,(size_t) in_buff_length); + if (!(length-=in_buff_length)) + return 0; + pos+=in_buff_length; + buff+=in_buff_length; + } + else + in_buff_length=0; + if (flag & READING_NEXT) + { + if (pos != ((info)->pos_in_file + + (uint) ((info)->rc_end - (info)->rc_request_pos))) + { + info->pos_in_file=pos; /* Force start here */ + info->rc_pos=info->rc_end=info->rc_request_pos; /* Everything used */ + info->seek_not_done=1; + } + else + info->rc_pos=info->rc_end; /* All block used */ + if (!(*info->read_function)(info,buff,length)) + return 0; + if (!(flag & READING_HEADER) || info->error == -1 || + (uint) info->error+in_buff_length < 3) + return 1; + if (BLOCK_INFO_HEADER_LENGTH < in_buff_length + (uint) info->error) + bzero(buff+info->error,BLOCK_INFO_HEADER_LENGTH - in_buff_length - + (uint) info->error); + return 0; + } + info->seek_not_done=1; + VOID(my_seek(info->file,pos,MY_SEEK_SET,MYF(0))); + if ((read_length=my_read(info->file,buff,length,MYF(0))) == length) + return 0; + if (!(flag & READING_HEADER) || (int) read_length == -1 || + read_length+in_buff_length < 3) + return 1; + bzero(buff+read_length,BLOCK_INFO_HEADER_LENGTH - in_buff_length - + read_length); + return 0; +} /* _nisam_read_cache */ |