js-cfb/bits/40_parse.js

function parse(file/*:RawBytes*/, options/*:CFBReadOpts*/)/*:CFBContainer*/ {
var mver = 3; // major version
var ssz = 512; // sector size
var nmfs = 0; // number of mini FAT sectors
var ndfs = 0; // number of DIFAT sectors
var dir_start = 0; // first directory sector location
var minifat_start = 0; // first mini FAT sector location
var difat_start = 0; // first mini FAT sector location

var fat_addrs/*:Array<number>*/ = []; // locations of FAT sectors

/* [MS-CFB] 2.2 Compound File Header */
var blob/*:CFBlob*/ = /*::(*/file.slice(0,512)/*:: :any)*/;
prep_blob(blob, 0);

/* major version */
var mv = check_get_mver(blob);
mver = mv[0];
switch(mver) {
	case 3: ssz = 512; break; case 4: ssz = 4096; break;
	default: throw new Error("Major Version: Expected 3 or 4 saw " + mver);
}

/* reprocess header */
if(ssz !== 512) { blob = /*::(*/file.slice(0,ssz)/*:: :any)*/; prep_blob(blob, 28 /* blob.l */); }
/* Save header for final object */
var header/*:RawBytes*/ = file.slice(0,ssz);

check_shifts(blob, mver);

// Number of Directory Sectors
var nds/*:number*/ = blob.read_shift(4, 'i');
if(mver === 3 && nds !== 0) throw new Error('# Directory Sectors: Expected 0 saw ' + nds);

// Number of FAT Sectors
//var nfs = blob.read_shift(4, 'i');
blob.l += 4;

// First Directory Sector Location
dir_start = blob.read_shift(4, 'i');

// Transaction Signature
blob.l += 4;

// Mini Stream Cutoff Size
blob.chk('00100000', 'Mini Stream Cutoff Size: ');

// First Mini FAT Sector Location
minifat_start = blob.read_shift(4, 'i');

// Number of Mini FAT Sectors
nmfs = blob.read_shift(4, 'i');

// First DIFAT sector location
difat_start = blob.read_shift(4, 'i');

// Number of DIFAT Sectors
ndfs = blob.read_shift(4, 'i');

// Grab FAT Sector Locations
for(var q = -1, j = 0; j < 109; ++j) { /* 109 = (512 - blob.l)>>>2; */
	q = blob.read_shift(4, 'i');
	if(q<0) break;
	fat_addrs[j] = q;
}

/** Break the file up into sectors */
var sectors/*:Array<RawBytes>*/ = sectorify(file, ssz);

sleuth_fat(difat_start, ndfs, sectors, ssz, fat_addrs);

/** Chains */
var sector_list/*:SectorList*/ = make_sector_list(sectors, dir_start, fat_addrs, ssz);

sector_list[dir_start].name = "!Directory";
if(nmfs > 0 && minifat_start !== ENDOFCHAIN) sector_list[minifat_start].name = "!MiniFAT";
sector_list[fat_addrs[0]].name = "!FAT";
sector_list.fat_addrs = fat_addrs;
sector_list.ssz = ssz;

/* [MS-CFB] 2.6.1 Compound File Directory Entry */
var files/*:CFBFiles*/ = {}, Paths/*:Array<string>*/ = [], FileIndex/*:CFBFileIndex*/ = [], FullPaths/*:Array<string>*/ = [], FullPathDir = {};
read_directory(dir_start, sector_list, sectors, Paths, nmfs, files, FileIndex);

build_full_paths(FileIndex, FullPathDir, FullPaths, Paths);

var root_name/*:string*/ = Paths.shift();

/* [MS-CFB] 2.6.4 (Unicode 3.0.1 case conversion) */
var find_path = make_find_path(FullPaths, Paths, FileIndex, files, root_name);

return {
	raw: {header: header, sectors: sectors},
	FileIndex: FileIndex,
	FullPaths: FullPaths,
	FullPathDir: FullPathDir,
	find: find_path
};
} // parse