mp4 file parse (WIP)

DataView.prototype.getString=function(bi,L){
 var s="";
 while(bi!=L){
  s+=String.fromCharCode(this.getUint8(bi));
  bi++;
 }
 return s;
};



//mp4 file to arraybuffer (byteArray), then to dataview


self.parse_mp4=function parse_mp4(dv,ind,L){
var rez=[],clen,cuc=0,bL=dv.byteLength; ind=ind||0,L=L||bL;
if(ind>bL||L>bL||L<8||ind<0){ return "input atom indexes are invalid"; }
while(ind<L){
 clen=dv.getUint32(ind); if((clen+ind)>L) console.log("error atom length overflow @ "+ind);
 else if(clen<8){ console.log("atom length underflow: "+clen+", skipped 4 bits @ "+ind); clen=4; }
 else rez.push([dv.getString(ind+4,ind+8),ind,clen]);
 ind+=clen;
  cuc++; if(cuc>65535){ console.log("infinite loop error @ "+ind); break; }
}
return rez;
};


//not use?
self.parse_atoms=function parse_atoms(ay,dv){
 var i2=ay.length,c;
 if(i2>0)while(i2--){ c=ay[i2]; c.push(parse_mp4(dv,c[1]+8,c[2]+c[1])); }
};


self.parse_mp4_iter=function parse_mp4_iter(dv,ind,L,L0,Pi){ if(L0>165){ return "somthin ain't right..."; }
var rez=[],clen,cuc=0,ye,bL=dv.byteLength; ind=ind||0,L=L||bL; L0=L0||0; Pi=Pi||0;
if(ind>bL||L>bL||L<8||ind<0){ return "input atom indexes are invalid"; }
while(ind<L){
 clen=dv.getUint32(ind); if((clen+ind)>L) console.log("error atom length overflow @ "+ind);
 else if(clen<8){clen=4; console.log("atom length underflow: "+clen+", skipped 4 bits @ "+ind);}
 else{ rez.push([dv.getString(ind+4,ind+8),ind,clen,Pi,L0]); rez=rez.concat(parse_mp4_iter(dv,ind+8,ind+clen,(L0)+1,ind)); }
 ind+=clen;
  cuc++; if(cuc>65535){ console.log("infinite loop error @ "+ind); break; }
}
return rez;
};

self.rMap=function reverseMap(parsa){ //input rez (output of parse_mp4_iter)
 var map={},i=parsa.length;
 while(i--){ map[parsa[i][1]]=i; }
 parsa.pm=map; //parent map;
 return map;
};


self.parse_stco=function parse_stco(stco,mp4Dv){ //input stco entry array from parse_mp4_iter

var si=stco[1],lim=si+stco[2], st=si+16,ne=mp4Dv.getUint32(si+12),i=st,
ent=[]; //chunck index entries;

while(i<lim){ ent.push(mp4Dv.getUint32(i)); i+=4; }
if(ent.length!=ne)console.error("error, chunk entry count is wrong?");
return ent;
};


//ex:
//rez[i]=[name,RealIndex,RealLength] //don't forget to add 8 to RealIndex (the length of the length store plus the type store)





//will need? https://web.archive.org/web/20201111155659im_/https://sole.github.io/Animated_GIF/dist/Animated_GIF.js

/*
finp=document.querySelector("input[type=file]");
fi=finp.files[0];
fi.arrayBuffer().then(function(a){ self.mp4Dv=new DataView(a);

self.rez2=parse_mp4(mp4Dv);



 });


*/