64 lines
2.4 KiB
JavaScript
64 lines
2.4 KiB
JavaScript
/** Chase down the rest of the DIFAT chain to build a comprehensive list
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DIFAT chains by storing the next sector number as the last 32 bits */
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function sleuth_fat(idx/*:number*/, cnt/*:number*/, sectors/*:Array<RawBytes>*/, ssz/*:number*/, fat_addrs)/*:void*/ {
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var q/*:number*/ = ENDOFCHAIN;
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if(idx === ENDOFCHAIN) {
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if(cnt !== 0) throw new Error("DIFAT chain shorter than expected");
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} else if(idx !== -1 /*FREESECT*/) {
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var sector = sectors[idx], m = (ssz>>>2)-1;
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if(!sector) return;
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for(var i = 0; i < m; ++i) {
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if((q = __readInt32LE(sector,i*4)) === ENDOFCHAIN) break;
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fat_addrs.push(q);
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}
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if(cnt >= 1) sleuth_fat(__readInt32LE(sector,ssz-4),cnt - 1, sectors, ssz, fat_addrs);
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}
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}
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/** Follow the linked list of sectors for a given starting point */
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function get_sector_list(sectors/*:Array<RawBytes>*/, start/*:number*/, fat_addrs/*:Array<number>*/, ssz/*:number*/, chkd/*:?Array<boolean>*/)/*:SectorEntry*/ {
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var buf/*:Array<number>*/ = [], buf_chain/*:Array<any>*/ = [];
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if(!chkd) chkd = [];
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var modulus = ssz - 1, j = 0, jj = 0;
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for(j=start; j>=0;) {
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chkd[j] = true;
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buf[buf.length] = j;
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buf_chain.push(sectors[j]);
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var addr = fat_addrs[Math.floor(j*4/ssz)];
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jj = ((j*4) & modulus);
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if(ssz < 4 + jj) throw new Error("FAT boundary crossed: " + j + " 4 "+ssz);
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if(!sectors[addr]) break;
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j = __readInt32LE(sectors[addr], jj);
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}
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return {nodes: buf, data:__toBuffer([buf_chain])};
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}
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/** Chase down the sector linked lists */
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function make_sector_list(sectors/*:Array<RawBytes>*/, dir_start/*:number*/, fat_addrs/*:Array<number>*/, ssz/*:number*/)/*:SectorList*/ {
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var sl = sectors.length, sector_list/*:SectorList*/ = ([]/*:any*/);
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var chkd/*:Array<boolean>*/ = [], buf/*:Array<number>*/ = [], buf_chain/*:Array<RawBytes>*/ = [];
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var modulus = ssz - 1, i=0, j=0, k=0, jj=0;
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for(i=0; i < sl; ++i) {
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buf = ([]/*:Array<number>*/);
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k = (i + dir_start); if(k >= sl) k-=sl;
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if(chkd[k]) continue;
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buf_chain = [];
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var seen = [];
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for(j=k; j>=0;) {
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seen[j] = true;
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chkd[j] = true;
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buf[buf.length] = j;
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buf_chain.push(sectors[j]);
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var addr/*:number*/ = fat_addrs[Math.floor(j*4/ssz)];
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jj = ((j*4) & modulus);
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if(ssz < 4 + jj) throw new Error("FAT boundary crossed: " + j + " 4 "+ssz);
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if(!sectors[addr]) break;
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j = __readInt32LE(sectors[addr], jj);
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if(seen[j]) break;
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}
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sector_list[k] = ({nodes: buf, data:__toBuffer([buf_chain])}/*:SectorEntry*/);
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}
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return sector_list;
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}
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