52 lines
1.8 KiB
JavaScript
52 lines
1.8 KiB
JavaScript
/** Break the file up into sectors */
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var nsectors = Math.ceil((file.length - ssz)/ssz);
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var sectors = [];
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for(var i=1; i != nsectors; ++i) sectors[i-1] = file.slice(i*ssz,(i+1)*ssz);
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sectors[nsectors-1] = file.slice(nsectors*ssz);
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/** 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 bytes */
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function sleuth_fat(idx, cnt) {
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if(idx === ENDOFCHAIN) {
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if(cnt !== 0) throw "DIFAT chain shorter than expected";
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return;
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}
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if(idx !== FREESECT) {
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var sector = sectors[idx];
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for(var i = 0; i != ssz/4-1; ++i) {
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if((q = __readUInt32LE(sector,i*4)) === ENDOFCHAIN) break;
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fat_addrs.push(q);
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}
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sleuth_fat(__readUInt32LE(sector,ssz-4),cnt - 1);
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}
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}
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sleuth_fat(difat_start, ndfs);
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/** DONT CAT THE FAT! Just calculate where we need to go */
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function get_buffer(byte_addr, bytes) {
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var addr = fat_addrs[Math.floor(byte_addr*4/ssz)];
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if(ssz - (byte_addr*4 % ssz) < (bytes || 0)) throw "FAT boundary crossed: " + byte_addr + " "+bytes+" "+ssz;
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return sectors[addr].slice((byte_addr*4 % ssz));
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}
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function get_buffer_u32(byte_addr) {
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return __readUInt32LE(get_buffer(byte_addr,4), 0);
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}
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function get_next_sector(idx) { return get_buffer_u32(idx); }
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/** Chains */
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var chkd = new Array(sectors.length), sector_list = [];
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var get_sector = function get_sector(k) { return sectors[k]; };
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for(i=0; i != sectors.length; ++i) {
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var buf = [], k = (i + dir_start) % sectors.length;
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if(chkd[k]) continue;
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for(j=k; j<=MAXREGSECT; buf.push(j),j=get_next_sector(j)) chkd[j] = true;
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sector_list[k] = {nodes: buf};
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sector_list[k].data = __toBuffer(Array(buf.map(get_sector)));
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}
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sector_list[dir_start].name = "!Directory";
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if(nmfs > 0 && minifat_start !== ENDOFCHAIN) sector_list[minifat_start].name = "!MiniFAT";
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sector_list[fat_addrs[0]].name = "!FAT";
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