filesys_8c-source.html

MP3播放器源代码, VS1003B

<a name="l00303"></a><a class="code" href="filesys_8c.html#a18">00303</a> <span class="keywordtype">unsigned</span> <span class="keywordtype">long</span> <a class="code" href="filesys_8c.html#a18">GetNextSector</a>(<span class="keywordtype">unsigned</span> <span class="keywordtype">long</span> currentSector){
00304   <a class="code" href="unionAddress.html">addressType</a> fatSector;
00305   <span class="keywordtype">unsigned</span> <span class="keywordtype">char</span> entryNumber;
00306   
00307   <span class="comment">/* how manyth sector from start of data area -&gt; fatsector */</span>
00308   fatSector.<a class="code" href="unionAddress.html#o0">l</a> = currentSector - <a class="code" href="filesys_8c.html#a4">dataStart</a>;
00309   
00310   <span class="comment">/* Check for cluster boundary */</span>
00311   <span class="comment">/* if we're not in cluster boundary then return currentsector + 1 */</span>
00312   <span class="keywordflow">if</span> ((fatSector.<a class="code" href="unionAddress.html#o1">b</a>.<a class="code" href="structAddress_1_1B.html#o0">b0</a> + 1) % <a class="code" href="filesys_8c.html#a5">fatSectorsPerCluster</a>){
00313     <span class="keywordflow">return</span> currentSector + 1;
00314   }
00315   
00316   <span class="comment">/* is the value negative? then return currentSector + 1 */</span>
00317   <span class="keywordflow">if</span> (fatSector.<a class="code" href="unionAddress.html#o1">b</a>.<a class="code" href="structAddress_1_1B.html#o3">b3</a> &amp; 0x80) {
00318     <span class="keywordflow">return</span> currentSector + 1;
00319   }    
00320 
00321   <span class="comment">/* The trivial conditions are not met, we actually do need to </span>
00322 <span class="comment">     look up the next sector info from FAT tables in the disk.*/</span>
00323 
00324   <span class="comment">/* convert fatSector from CurrentSectorN to currentClusterN */</span>
00325   fatSector.<a class="code" href="unionAddress.html#o0">l</a> /= <a class="code" href="filesys_8c.html#a5">fatSectorsPerCluster</a>;
00326 
00327   <span class="comment">/* calculate which page (fatSector) and entry of FAT table correspond</span>
00328 <span class="comment">     to current sector */</span>
00329    
00330   <span class="keywordflow">if</span> (!<a class="code" href="filesys_8h.html#a0">IS_FAT_32</a>){ <span class="comment">//FAT16</span>
00331     entryNumber = fatSector.<a class="code" href="unionAddress.html#o1">b</a>.<a class="code" href="structAddress_1_1B.html#o0">b0</a>; <span class="comment">/* 256 entries / page in FAT16 table */</span>
00332     fatSector.<a class="code" href="unionAddress.html#o0">l</a> &gt;&gt;= 8; <span class="comment">/* Divide by 256 (n of entries/page in FAT32 table */</span>
00333   }<span class="keywordflow">else</span>{ <span class="comment">//FAT32</span>
00334     entryNumber =(fatSector.<a class="code" href="unionAddress.html#o1">b</a>.<a class="code" href="structAddress_1_1B.html#o0">b0</a> &amp; 0x7f); <span class="comment">/* 128 entries/page in FAT32 tbl */</span>
00335     fatSector.<a class="code" href="unionAddress.html#o0">l</a> &gt;&gt;= 7; <span class="comment">/* Divide by 128 (n of entries/sector in FAT32 table */</span>
00336   }
00337   
00338   <span class="comment">/* Get sector address for the needed page */</span>
00339   fatSector.<a class="code" href="unionAddress.html#o0">l</a> += <a class="code" href="filesys_8c.html#a2">fatStart</a>;
00340   
00341   <span class="comment">/* Load (if needed) table page from disk */</span>
00342   <span class="keywordflow">if</span> (<a class="code" href="buffer_8c.html#a2">sectorAddress</a>.<a class="code" href="unionAddress.html#o0">l</a> != fatSector.<a class="code" href="unionAddress.html#o0">l</a>){
00343     <a class="code" href="buffer_8c.html#a2">sectorAddress</a>.<a class="code" href="unionAddress.html#o0">l</a> = fatSector.<a class="code" href="unionAddress.html#o0">l</a>; <span class="comment">/* (not needed because mmc.c does this) */</span>
00344     <a class="code" href="storage_8h.html#a2">ReadDiskSector</a>(fatSector.<a class="code" href="unionAddress.html#o0">l</a>);
00345     
00346     ConsolePutChar(<span class="charliteral">'n'</span>);
00347     
00348     
00349   }
00350   <span class="comment">/* Now there should be correct FAT entry page in memory... */</span>
00351   
00352   <span class="keywordflow">if</span> (!<a class="code" href="filesys_8h.html#a0">IS_FAT_32</a>){ <span class="comment">//FAT16</span>
00353     fatSector.<a class="code" href="unionAddress.html#o0">l</a> = <a class="code" href="buffer_8c.html#a0">diskSect</a>.<a class="code" href="unionDiskBlock.html#o3">Fat16Table</a>[entryNumber];
00354     <span class="comment">/* Check for FAT16 end-of-file condition */</span>
00355     <span class="keywordflow">if</span> ((fatSector.<a class="code" href="unionAddress.html#o1">b</a>.<a class="code" href="structAddress_1_1B.html#o1">b1</a> == 0xff) &amp;&amp; (fatSector.<a class="code" href="unionAddress.html#o1">b</a>.<a class="code" href="structAddress_1_1B.html#o0">b0</a> == 0xff)){
00356       <span class="comment">/* End of file */</span>
00357       fatSector.<a class="code" href="unionAddress.html#o1">b</a>.<a class="code" href="structAddress_1_1B.html#o3">b3</a> = 0xff; <span class="comment">/* return a large value (fat32 compatible) */</span>
00358       <span class="keywordflow">return</span> fatSector.<a class="code" href="unionAddress.html#o0">l</a>;
00359     }
00360   }<span class="keywordflow">else</span>{ <span class="comment">//FAT32</span>
00361     fatSector.<a class="code" href="unionAddress.html#o0">l</a> = <a class="code" href="buffer_8c.html#a0">diskSect</a>.<a class="code" href="unionDiskBlock.html#o4">Fat32Table</a>[entryNumber] &amp; 0x0fffffff;
00362     <span class="comment">/* Check for FAT32 end-of-file condition */</span>
00363     <span class="keywordflow">if</span> ((fatSector.<a class="code" href="unionAddress.html#o1">b</a>.<a class="code" href="structAddress_1_1B.html#o3">b3</a>&amp;0x08) <span class="comment">//Quick test</span>
00364         &amp;&amp; (fatSector.<a class="code" href="unionAddress.html#o0">l</a>&gt;0x0ffffff0)){ <span class="comment">//Complete test</span>
00365       <span class="comment">/* End of file */</span>
00366       <span class="keywordflow">return</span> 0xffffffff; <span class="comment">/* return EOF*/</span>
00367     }
00368   }
00369   
00370 
00371   <span class="comment">/* now fatSector.l contains the proper next cluster value */</span>
00372 
00373   fatSector.<a class="code" href="unionAddress.html#o0">l</a> *= <a class="code" href="filesys_8c.html#a5">fatSectorsPerCluster</a>;
00374   <span class="comment">/* now fatSector.l contains the next sector value */</span>
00375 
00376   fatSector.<a class="code" href="unionAddress.html#o0">l</a> += <a class="code" href="filesys_8c.html#a4">dataStart</a>;
00377   <span class="comment">/* now fatSector.l contains the proper absolute sector address */</span>
00378 
00379   <span class="keywordflow">return</span> fatSector.<a class="code" href="unionAddress.html#o0">l</a>;
00380 }
00381 
00382 
<a name="l00401"></a><a class="code" href="filesys_8h.html#a10">00401</a> <a class="code" href="board_8h.html#a47">Public</a> <span class="keywordtype">unsigned</span> <span class="keywordtype">char</span> <a class="code" href="filesys_8c.html#a19">BuildFragmentTable</a>(){
00402 
00403   <span class="keywordtype">unsigned</span> <span class="keywordtype">char</span> c=0;
00404   <a class="code" href="unionAddress.html">addressType</a> <span class="keyword">this</span>,next;
00405   <a class="code" href="unionAddress.html">addressType</a> fatSector;
00406   <span class="keywordtype">unsigned</span> <span class="keywordtype">char</span> entryNumber;
00407 
00408 
00409   <span class="keywordflow">if</span> (<a class="code" href="filesys_8c.html#a12">IS_FAT_12</a>){
00410     ConsoleWrite(<span class="stringliteral">"Single fragment support for FAT12"</span>);
00411     <a class="code" href="filesys_8c.html#a6">fragment</a>[0].<a class="code" href="structfragmentEntry.html#o0">start</a> = <a class="code" href="buffer_8c.html#a2">sectorAddress</a>.<a class="code" href="unionAddress.html#o0">l</a>;
00412     <a class="code" href="filesys_8c.html#a6">fragment</a>[0].<a class="code" href="structfragmentEntry.html#o1">length</a> = <a class="code" href="filesys_8c.html#a7">fileSize</a>/512;
00413     <span class="keywordflow">return</span>(1); <span class="comment">//Return 1 fragment</span>
00414   }
00415 
00416 
00417   <span class="comment">//as long as the sectorAddress is "sane"...</span>
00418   <span class="keywordflow">while</span> (!(<a class="code" href="buffer_8c.html#a2">sectorAddress</a>.<a class="code" href="unionAddress.html#o1">b</a>.<a class="code" href="structAddress_1_1B.html#o3">b3</a> &amp; 0x80)){
00419         
00420     <a class="code" href="filesys_8c.html#a6">fragment</a>[c].<a class="code" href="structfragmentEntry.html#o0">start</a> = <a class="code" href="buffer_8c.html#a2">sectorAddress</a>.<a class="code" href="unionAddress.html#o0">l</a>;
00421     <a class="code" href="filesys_8c.html#a6">fragment</a>[c].<a class="code" href="structfragmentEntry.html#o1">length</a> = <a class="code" href="filesys_8c.html#a5">fatSectorsPerCluster</a>;
00422     
00423     <span class="comment">/* Find cluster entry for the current sector */</span>
00424     
00425     <span class="comment">/* in how manyth sector from start of data area are we? -&gt;this */</span>
00426     <span class="keyword">this</span>.l = <a class="code" href="buffer_8c.html#a2">sectorAddress</a>.<a class="code" href="unionAddress.html#o0">l</a> - <a class="code" href="filesys_8c.html#a4">dataStart</a>;
00427     <span class="comment">/* convert from CurrentSectorN to currentClusterN */</span>
00428     <span class="keyword">this</span>.l /= <a class="code" href="filesys_8c.html#a5">fatSectorsPerCluster</a>;
00429     <span class="comment">/* this.l is now the current cluster number */</span>
00430     
00431     
00432     <span class="comment">/* now let's find the FAT entry for this.l cluster */</span>
00433     <span class="keywordflow">if</span> (!<a class="code" href="filesys_8h.html#a0">IS_FAT_32</a>){ <span class="comment">//FAT16</span>
00434       entryNumber = <span class="keyword">this</span>.b.b0; <span class="comment">/* 256 entries / page in FAT16 table */</span>
00435       fatSector.<a class="code" href="unionAddress.html#o0">l</a> = <span class="keyword">this</span>.l &gt;&gt; 8; <span class="comment">/* Div by n of entries/page in FAT16 tbl*/</span>
00436     }<span class="keywordflow">else</span>{ <span class="comment">//FAT32</span>
00437       entryNumber = (<span class="keyword">this</span>.b.b0 &amp; 0x7f); <span class="comment">/* 128 entries/page in FAT32 table */</span>
00438       fatSector.<a class="code" href="unionAddress.html#o0">l</a> = <span class="keyword">this</span>.l &gt;&gt; 7; <span class="comment">/* Div by n of entries/page in FAT32 tbl*/</span>
00439     }
00440     fatSector.<a class="code" href="unionAddress.html#o0">l</a> += <a class="code" href="filesys_8c.html#a2">fatStart</a>;
00441     <span class="comment">/* fatSector.l is now the DISK SECTOR NUMBER CONTAINING THE FAT table */</span>
00442     <span class="comment">/* read this page into memory */</span>
00443     <a class="code" href="storage_8h.html#a2">ReadDiskSector</a>(fatSector.<a class="code" href="unionAddress.html#o0">l</a>);    
00444     
00445     <span class="keywordflow">if</span> (!<a class="code" href="filesys_8h.html#a0">IS_FAT_32</a>){ <span class="comment">//FAT16</span>
00446       next.<a class="code" href="unionAddress.html#o0">l</a> = <a class="code" href="buffer_8c.html#a0">diskSect</a>.<a class="code" href="unionDiskBlock.html#o3">Fat16Table</a>[entryNumber]; <span class="comment">/* get next cluster n */</span>
00447       <span class="comment">/* Check for FAT16 end-of-file condition */</span>
00448       <span class="keywordflow">if</span> ((next.<a class="code" href="unionAddress.html#o1">b</a>.<a class="code" href="structAddress_1_1B.html#o1">b1</a> == 0xff) &amp;&amp; (next.<a class="code" href="unionAddress.html#o1">b</a>.<a class="code" href="structAddress_1_1B.html#o0">b0</a> == 0xff)){
00449         <span class="comment">/* FAT16 End of file */</span>
00450         next.<a class="code" href="unionAddress.html#o1">b</a>.<a class="code" href="structAddress_1_1B.html#o3">b3</a> = 0xff; <span class="comment">/* return a large value (fat32 compatible) */</span>
00451       }