MTK优美代码赏析7:文件搜索与匹配
???最近因需要拓展音乐播放器功能，研究了下MTK的文件系统，趁周末我总结一下关于文件系统关键的接口<文件搜索与匹配>MTK实现的方法。
???关于文件搜索，因为都是基于FAT格式的系统，所以MTK文件处理的思路和Window是很相似的。
???通过FindFirstFile函数获取操作句柄HANDLE，将此句柄作为参数传入FindNextFile函数，通过FindNextFile不断搜索下一个文件/文件夹，当FindNextFile返回值为0时表示搜索完成，查询完成后通过FindClose关闭句柄。
???对应MTK中的接口为FS_FindFirst,FS_FindNext和FS_FindClose，下面拿一段代码来看(来自aud_vr_sd.c)
//作者：张素丰，转载请注明出处：http://www.zhangsufeng.cn/?p=237/??FUNCTION???aud_vr_sd_scan_tags_in_group_folder??DESCRIPTION???vr?sd?scan?all?tags?in?a?group?folder??PARAMETERS???group_id????????[IN]???????????path????????????[?]???????????RETURNS???void?/void?aud_vr_sd_scan_tags_in_group_folder(kal_uint16?group_id,?kal_uint16?path){????/----------------------------------------------------------------/????/?Local?Variables????????????????????????????????????????????????/????/----------------------------------------------------------------/????kal_uint16?filename[VR_MAX_DB_PATH_LEN?+?1];????kal_uint16?filename_expr[VR_MAX_DB_PATH_LEN?+?1];????kal_int32?word_id;????FS_HANDLE?fd_cursor;????FS_DOSDirEntry?file_info;????/----------------------------------------------------------------/????/?Code?Body??????????????????????????????????????????????????????/????/----------------------------------------------------------------/????vr_sd_ctx.id_length[group_id]?=?0;????kal_wsprintf(filename_expr,?"%wMTKVR_????.vrd",?path);????if?((fd_cursor?=?FS_FindFirst(filename_expr,?0,?0,?&file_info,?filename,?(VR_MAX_DB_PATH_LEN?+?1)?<=?0)????{????????/?loop?through?all?vrd?files?in?a?group?folder?/????????do????????{????????????/?filter?out?folder?results?/????????????if?(!(file_info.Attributes?&?FS_ATTR_DIR))????????????{????????????????/?parse?word?id?and?add?to?id?array?and?increment?id?length?/????????????????if?((word_id?=?aud_vr_sd_extract_word_id(filename))?>=?0)????????????????{????????????????????vr_sd_ctx.id_array[group_id][vr_sd_ctx.id_length[group_id]++]?=?word_id;????????????????}????????????}????????}?while?(FS_FindNext(fd_cursor,?&file_info,?filename,?(VR_MAX_DB_PATH_LEN?+?1)?<
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???下面讲一讲匹配，这里所说的匹配主要是将文件格式(即后缀名)的匹配,在获取到文件名以后进行。
???思路也都是相同的，那就是从文件名末端开始搜索到第一个"."，然后截取"."后面这一段作为拓展名，然后把这个拓展名拿到自己的需要的格式列表中对比即可。
???MTK中有两种方式实现了这个需求，
???方式1(来自FileManagerSrc.c):
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??FUNCTION???mmi_fmgr_get_file_group??DESCRIPTION???check?file?type?belongs?to?which?file?group??PARAMETERS???path????????[?]???????RETURNS???void?/U8?mmi_fmgr_get_file_group(S8?path){????/----------------------------------------------------------------/????/?Local?Variables????????????????????????????????????????????????/????/----------------------------------------------------------------/????FMGR_FILTER?file_type;????S32?result;????/----------------------------------------------------------------/????/?Code?Body??????????????????????????????????????????????????????/????/----------------------------------------------------------------/????result?=?mmi_fmgr_get_file_type(path,?&file_type);????if?(result?==?FS_FILE_NOT_FOUND)????{????????return?FMGR_GROUP_UNKNOWN;????}????????if?(FMGR_FILTER_IS_SET_AUDIO(&file_type))????{????????return?FMGR_GROUP_AUDIO;????}????else?if?(FMGR_FILTER_IS_SET_IMAGE(&file_type))????{????????return?FMGR_GROUP_IMAGE;????}????else?if?(FMGR_FILTER_IS_SET_VIDEO(&file_type))????{????????return?FMGR_GROUP_VIDEO;????}????else?if?(FMGR_FILTER_IS_SET_SWFLASH(&file_type))????{????????return?FMGR_GROUP_SWFLASH;????}????else????{????????return?FMGR_GROUP_UNKNOWN;????}}
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?在mmi_fmgr_get_file_type函数内实现了相应的逻辑，这个流程依赖于FileMgr.c中
constfmgr_filter_structfmgr_filter[FMGR_MAX_FILTER_COUNT]；
???方式2：依赖于系统的全局变量的东西有时并不能满足我们应用的需求，这个时候我们需要自己定义一个私有的fmgr_filter，来实现拓展名的判断。
???这个流程的实现可以参照09A代码AudioPlayerPlayList.c中mmi_audply_playlist_generate_search函数。
???下面来对比两个获取后缀名的函数：
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??FUNCTION???mmi_fmgr_extract_ext_file_name??DESCRIPTION???get?pointer?to?the?extension?file?name?in?the?file?path??PARAMETERS???path????????[?]???????RETURNS???void?/PS8?mmi_fmgr_extract_ext_file_name(S8?path){????/----------------------------------------------------------------/????/?Local?Variables????????????????????????????????????????????????/????/----------------------------------------------------------------/????S16?i,?length;????/----------------------------------------------------------------/????/?Code?Body??????????????????????????????????????????????????????/????/----------------------------------------------------------------/????length?=?(S16)?mmi_ucs2strlen(path);????i?=?length?-?1;????while?(i?>=?0)????{????????if?(path[i?<
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???另一种系统string处理的接口：
/??FUNCTION???app_ucs2_strrchr??DESCRIPTION???Scan?a?UCS2?encoded?string?for?the?last?occurrence?of?a?character.??PARAMETERS???string????????[IN]??UCS2?encoded?string?to?search?in.??????????ch????????????[IN]??UCS2?encoded?wide-character?to?search?for.????????RETURNS???returns?pointer?to?the?last?occurrence?of?ch?in?string???returns?NULL?if?ch?does?not?occur?in?string?/kal_int8?app_ucs2_strrchr(const?kal_int8??string,?kal_wchar?ch){????/----------------------------------------------------------------/????/?Local?Variables????????????????????????????????????????????????/????/----------------------------------------------------------------/????kal_int8?cursor?=?(kal_int8?)string;????????/----------------------------------------------------------------/????/?Code?Body??????????????????????????????????????????????????????/????/----------------------------------------------------------------/????????while?(cursor?||?(cursor+1))??????????????/?find?end?of?string?/????{????????cursor?+=?2;????}????????/?search?towards?front?/????while?((kal_int8?)string?!=?cursor?&&????????????((cursor+1)<<8|(kal_uint8)(cursor))?!=?ch)????{????????cursor?-=?2;????}????????if?(((cursor+1)<<8|(kal_uint8)(cursor))?==?ch)??????????/?found??/????{????????return?cursor;????}????????return?NULL;}PS8??test(const?UI_string_type?ext){?????/----------------------------------------------------------------/????/?Local?Variables????????????????????????????????????????????????/????/----------------------------------------------------------------/????U8?i?=?0;????U32?ext_len?=?0;????UI_character_type?file_ext[FMGR_MAX_EXT_LEN?+?1];????/----------------------------------------------------------------/????/?Code?Body??????????????????????????????????????????????????????/????/----------------------------------------------------------------/???/?skip?".".?/????{????????PS8?dot?=?(PS8)app_ucs2_strrchr((const?PS8)ext,?(U16)L''.'');????????if?(dot)????????{????????????dot?+=?2;????????}????????else????????{????????????dot?=?(PS8)ext;????????}????????mmi_ucs2ncpy((PS8)file_ext,?(const?PS8)dot,?FMGR_MAX_EXT_LEN);????????ext_len?=?mmi_ucs2strlen((const?PS8)dot);????????return?dot;????}}
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