[rnd me]

Intro
By popular demand, here is how i "zip and unzip" strings in javascript. I did not write the orig, that was done a long time a go in a land far away. But, i have managed to squeeze 55kb into 8kb, and 20kb into 5kb, making the package useful in real-life. i made a peppering of other minor optimizations. My point is that even though i didn't come up with this, it's still as it stands below, my pride and joy. This was an ace up my sleeve that I decided to throw down on the table for all to see. X-mas comes early this year...





Code


Live Copy

/* Copyright (C) 1999 Masanao Izumo <iz@onicos.co.jp>
 * Version: 1.0.1
 * LastModified: Dec 25 1999.
 * updated and compressed by dandavis, 2012 (attribution only derivative)
 * Presumed abandonware, but retain this notice for public use.
 */

// 5kb:
var inflate=function(){function U(){this[J]=this[R]=null}function V(){this.n=this.b=this.e=0,this.t=null}function K(h,v,u,b,a,p){this[D]=16,this.N_MAX=288,this[z]=0,this[C]=null,this.m=0;var q=B(this[D]+1),m,c,l,g,d,e,f,i=B(this[D]+1),j,k,A,w=new V,r=B(this[D]);g=B(this.N_MAX);var x,s=B(this[D]+1),n,t,y;y=this[C]=null;for(d=0;d<q[E];d++)q[d]=0;for(d=0;d<i[E];d++)i[d]=0;for(d=0;d<r[E];d++)r[d]=null;for(d=0;d<g[E];d++)g[d]=0;for(d=0;d<s[E];d++)s[d]=0;m=256<v?h[256]:this[D],j=h,k=0,d=v;do q[j[k]]++,k++;while(0<--d);if(q[0]==v)this[C]=null,this[z]=this.m=0;else{for(e=1;e<=this[D]&&0==q[e];e++);f=e,p<e&&(p=e);for(d=this[D];0!=d&&0==q[d];d--);l=d,p>d&&(p=d);for(n=1<<e;e<d;e++,n<<=1)if(0>(n-=q[e])){this[z]=2,this.m=p;return}if(0>(n-=q[d]))this[z]=2,this.m=p;else{q[d]+=n,s[1]=e=0,j=q,k=1;for(A=2;0<--d;)s[A++]=e+=j[k++];j=h,d=k=0;do 0!=(e=j[k++])&&(g[s[e]++]=d);while(++d<v);v=s[l],s[0]=d=0,j=g,k=0,g=-1,x=i[0]=0,A=null;for(t=0;f<=l;f++)for(h=q[f];0<h--;){for(;f>x+i[1+g];){x+=i[1+g],g++,t=(t=l-x)>p?p:t;if((c=1<<(e=f-x))>h+1){c-=h+1;for(A=f;++e<t&&!((c<<=1)<=q[++A]);)c-=q[A]}x+e>m&&x<m&&(e=m-x),t=1<<e,i[1+g]=e,A=B(t);for(c=0;c<t;c++)A[c]=new V;null==y?y=this[C]=new U:y=y[R]=new U,y[R]=null,y[J]=A,r[g]=A,0<g&&(s[g]=d,w.b=i[g],w.e=16+e,w.t=A,e=(d&(1<<x)-1)>>x-i[g],r[g-1][e].e=w.e,r[g-1][e].b=w.b,r[g-1][e].n=w.n,r[g-1][e].t=w.t)}w.b=f-x,k>=v?w.e=99:j[k]<u?(w.e=256>j[k]?16:15,w.n=j[k++]):(w.e=a[j[k]-u],w.n=b[j[k++]-u]),c=1<<f-x;for(e=d>>x;e<t;e+=c)A[e].e=w.e,A[e].b=w.b,A[e].n=w.n,A[e].t=w.t;for(e=1<<f-1;0!=(d&e);e>>=1)d^=e;for(d^=e;(d&(1<<x)-1)!=s[g];)x-=i[g],g--}this.m=i[1],this[z]=0!=n&&1!=l?1:0}}}function f(h){for(;y<h;)H|=(M[E]==S?-1:M.charCodeAt(S++)&255)<<y,y+=8}function i(h){return H&ba[h]}function l(h){H>>=h,y-=h}function N(h,v,u){var b,a,p;if(0==u)return 0;for(p=0;;){f(r),a=s[J][i(r)];for(b=a.e;16<b;){if(99==b)return-1;l(a.b),b-=16,f(b),a=a.t[i(b)],b=a.e}l(a.b);if(16==b)j&=F-1,h[v+p++]=n[j++]=a.n;else{if(15==b)break;f(b),k=a.n+i(b),l(b),f(I),a=T[J][i(I)];for(b=a.e;16<b;){if(99==b)return-1;l(a.b),b-=16,f(b),a=a.t[i(b)],b=a.e}l(a.b),f(b),G=j-a.n-i(b);for(l(b);0<k&&p<u;)k--,G&=F-1,j&=F-1,h[v+p++]=n[j++]=n[G++]}if(p==u)return u}return t=-1,p}function ca(h,j,k){var b,a,p,q,m,c,n,g=B(316);for(b=0;b<g[E];b++)g[b]=0;f(5),c=257+i(5),l(5),f(5),n=1+i(5),l(5),f(4),b=4+i(4),l(4);if(286<c||30<n)return-1;for(a=0;a<b;a++)f(3),g[W[a]]=i(3),l(3);for(;19>a;a++)g[W[a]]=0;r=7,a=new K(g,19,19,null,null,r);if(0!=a[z])return-1;s=a[C],r=a.m,q=c+n;for(b=p=0;b<q;)if(f(r),m=s[J][i(r)],a=m.b,l(a),a=m.n,16>a)g[b++]=p=a;else if(16==a){f(2),a=3+i(2),l(2);if(b+a>q)return-1;for(;0<a--;)g[b++]=p}else{17==a?(f(3),a=3+i(3),l(3)):(f(7),a=11+i(7),l(7));if(b+a>q)return-1;for(;0<a--;)g[b++]=0;p=0}r=da,a=new K(g,c,257,X,Y,r),0==r&&(a[z]=1);if(0!=a[z])return 1==a[z],-1;s=a[C],r=a.m;for(b=0;b<n;b++)g[b]=g[b+c];return I=ea,a=new K(g,n,0,Z,$,I),T=a[C],I=a.m,0==I&&257<c?-1:(1==a[z],0!=a[z]?-1:N(h,j,k))}function fa(h,v,u){var b,a;for(b=0;b<u&&(!L||-1!=t);){if(0<k){if(t!=ga)for(;0<k&&b<u;)k--,G&=F-1,j&=F-1,h[v+b++]=n[j++]=n[G++];else{for(;0<k&&b<u;)k--,j&=F-1,f(8),h[v+b++]=n[j++]=i(8),l(8);0==k&&(t=-1)}if(b==u)break}if(-1==t){if(L)break;f(1),0!=i(1)&&(L=!0),l(1),f(2),t=i(2),l(2),s=null,k=0}switch(t){case 0:a=h;var p=v+b,q=u-b,m=void 0,m=y&7;l(m),f(16),m=i(16),l(16),f(16);if(m!=(~H&65535))a=-1;else{l(16),k=m;for(m=0;0<k&&m<q;)k--,j&=F-1,f(8),a[p+m++]=n[j++]=i(8),l(8);a=(0==k&&(t=-1),m)}break;case 1:if(null!=s)a=N(h,v+b,u-b);else a:{a=h,p=v+b,q=u-b;if(null==O){for(var c=void 0,m=B(288),c=0;144>c;c++)m[c]=8;for(;256>c;c++)m[c]=9;for(;280>c;c++)m[c]=7;for(;288>c;c++)m[c]=8;P=7,c=new K(m,288,257,X,Y,P);if(0!=c[z]){a=(alert("HufBuild error: "+c[z]),-1);break a}O=c[C],P=c.m;for(c=0;30>c;c++)m[c]=5;Q=5,c=new K(m,30,0,Z,$,Q);if(1<c[z]){a=(O=null,alert("HufBuild error: "+c[z]),-1);break a}aa=c[C],Q=c.m}a=(s=O,T=aa,r=P,I=Q,N(a,p,q))}break;case 2:null!=s?a=N(h,v+b,u-b):a=ca(h,v+b,u-b);break;default:a=-1}if(-1==a)return L?0:-1;b+=a}return b}var B=Array,z="status",E="length",C="root",D="BMAX",J="list",R="next",Q,F=32768,ga=0,da=9,ea=6,n,j,O=null,aa,P,H,y,t,L,k,G,s,T,r,I,M,S,ba=[0,1,3,7,15,31,63,127,255,511,1023,2047,4095,8191,16383,32767,65535],X=[3,4,5,6,7,8,9,10,11,13,15,17,19,23,27,31,35,43,51,59,67,83,99,115,131,163,195,227,258,0,0],Y=[0,0,0,0,0,0,0,0,1,1,1,1,2,2,2,2,3,3,3,3,4,4,4,4,5,5,5,5,0,99,99],Z=[1,2,3,4,5,7,9,13,17,25,33,49,65,97,129,193,257,385,513,769,1025,1537,2049,3073,4097,6145,8193,12289,16385,24577],$=[0,0,0,0,1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12,13,13],W=[16,17,18,0,8,7,9,6,10,5,11,4,12,3,13,2,14,1,15];return window.inflate=function(h){var f,i,b;null==n&&(n=B(2*F)),y=H=j=0,t=-1,L=!1,k=G=0,s=null,M=h,S=0,f=B(1024);for(h="";0<(i=fa(f,0,f[E]));)for(b=0;b<i;b++)h+=String.fromCharCode(f[b]);return M=null,h}}();


// 8kb:
var deflate=function(){var e,t,n,r,i=null,s,o,u,a,f,l,c,h,p,d,v,m,g,y,b,w,E,S,x,T,N,C,k,L,A,O,M,_,D,P,H,B,j,F,I,q,R,U,z,W,X,V,$,J,K,Q,G,Y,Z,et,tt,nt=function(){this.dl=this.fc=0},rt=function(){this.extra_bits=this.static_tree=this.dyn_tree=null,this.max_code=this.max_length=this.elems=this.extra_base=0},it=function(e,t,n,r){this.good_length=e,this.max_lazy=t,this.nice_length=n,this.max_chain=r},st=function(){this.next=null,this.len=0,this.ptr=[8192],this.off=0},ot=[0,0,0,0,0,0,0,0,1,1,1,1,2,2,2,2,3,3,3,3,4,4,4,4,5,5,5,5,0],ut=[0,0,0,0,1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12,13,13],at=[0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2,3,7],ft=[16,17,18,0,8,7,9,6,10,5,11,4,12,3,13,2,14,1,15],lt=[new it(0,0,0,0),new it(4,4,8,4),new it(4,5,16,8),new it(4,6,32,32),new it(4,4,16,16),new it(8,16,32,32),new it(8,16,128,128),new it(8,32,128,256),new it(32,128,258,1024),new it(32,258,258,4096)],ct=function(r){i[o+s++]=r;if(8192==o+s&&0!=s){var u,r=(null!=e?(u=e,e=e.next):u=new st,u.next=null,u.len=u.off=0,u);null==t?t=n=r:n=n.next=r,r.len=s-o;for(u=0;u<r.len;u++)r.ptr[u]=i[o+u];s=o=0}},ht=function(e){e&=65535,8190>o+s?(i[o+s++]=e&255,i[o+s++]=e>>>8):(ct(e&255),ct(e>>>8))},pt=function(){v=(v<<5^a[E+3-1]&255)&8191,m=c[32768+v],c[E&32767]=m,c[32768+v]=E},dt=function(e,t){Ot(t[e].fc,t[e].dl)},vt=function(e,t,n){return e[t].fc<e[n].fc||e[t].fc==e[n].fc&&R[t]<=R[n]},mt=function(e,t,n){var r;for(r=0;r<n&&tt<et.length;r++)e[t+r]=et.charCodeAt(tt++)&255;return r},gt=function(e){var t=N,n=E,r,i=w,s=32506<E?E-32506:0,o=E+258,u=a[n+i-1],f=a[n+i];w>=L&&(t>>=2);do if(r=e,a[r+i]==f&&a[r+i-1]==u&&a[r]==a[n]&&a[++r]==a[n+1]){n+=2,r++;do;while(a[++n]==a[++r]&&a[++n]==a[++r]&&a[++n]==a[++r]&&a[++n]==a[++r]&&a[++n]==a[++r]&&a[++n]==a[++r]&&a[++n]==a[++r]&&a[++n]==a[++r]&&n<o);r=258-(o-n),n=o-258;if(r>i){S=e,i=r;if(258<=r)break;u=a[n+i-1],f=a[n+i]}}while((e=c[e&32767])>s&&0!=--t);return i},yt=function(){var e,t,n=65536-T-E;if(-1==n)n--;else if(65274<=E){for(e=0;32768>e;e++)a[e]=a[e+32768];S-=32768,E-=32768,d-=32768;for(e=0;8192>e;e++)t=c[32768+e],c[32768+e]=32768<=t?t-32768:0;for(e=0;32768>e;e++)t=c[e],c[e]=32768<=t?t-32768:0;n+=32768}x||(e=mt(a,E+T,n),0>=e?x=!0:T+=e)},bt=function(e,n,i){var f;if(!r){if(!x){p=h=0;var l,F;if(0==_[0].dl){P.dyn_tree=A,P.static_tree=M,P.extra_bits=ot,P.extra_base=257,P.elems=286,P.max_length=15,P.max_code=0,H.dyn_tree=O,H.static_tree=_,H.extra_bits=ut,H.extra_base=0,H.elems=30,H.max_length=15,H.max_code=0,B.dyn_tree=D,B.static_tree=null,B.extra_bits=at,B.extra_base=0,B.elems=19,B.max_length=7;for(F=l=B.max_code=0;28>F;F++){W[F]=l;for(f=0;f<1<<ot[F];f++)U[l++]=F}U[l-1]=F;for(F=l=0;16>F;F++){X[F]=l;for(f=0;f<1<<ut[F];f++)z[l++]=F}for(l>>=7;30>F;F++){X[F]=l<<7;for(f=0;f<1<<ut[F]-7;f++)z[256+l++]=F}for(f=0;15>=f;f++)j[f]=0;for(f=0;143>=f;)M[f++].dl=8,j[8]++;for(;255>=f;)M[f++].dl=9,j[9]++;for(;279>=f;)M[f++].dl=7,j[7]++;for(;287>=f;)M[f++].dl=8,j[8]++;xt(M,287);for(f=0;30>f;f++)_[f].dl=5,_[f].fc=Mt(f,5);Et()}for(f=0;8192>f;f++)c[32768+f]=0;C=lt[k].max_lazy,L=lt[k].good_length,N=lt[k].max_chain,d=E=0,T=mt(a,0,65536);if(0>=T)x=!0,T=0;else{for(x=!1;262>T&&!x;)yt();for(f=v=0;2>f;f++)v=(v<<5^a[f]&255)&8191}t=null,o=s=0,3>=k?(w=2,b=0):(b=2,y=0),u=!1}r=!0;if(0==T)return u=!0,0}if((f=wt(e,n,i))==i)e=i;else if(u)e=f;else{if(3>=k)for(;0!=T&&null==t;){pt(),0!=m&&32506>=E-m&&(b=gt(m),b>T&&(b=T));if(3<=b)if(F=Lt(E-S,b-3),T-=b,b<=C){b--;do E++,pt();while(0!=--b);E++}else E+=b,b=0,v=a[E]&255,v=(v<<5^a[E+1]&255)&8191;else F=Lt(0,a[E]&255),T--,E++;for(F&&(kt(0),d=E);262>T&&!x;)yt()}else for(;0!=T&&null==t;){pt(),w=b,g=S,b=2,0!=m&&w<C&&32506>=E-m&&(b=gt(m),b>T&&(b=T),3==b&&4096<E-S&&b--);if(3<=w&&b<=w){F=Lt(E-1-g,w-3),T-=w-1,w-=2;do E++,pt();while(0!=--w);y=0,b=2,E++,F&&(kt(0),d=E)}else 0!=y?(Lt(0,a[E-1]&255)&&(kt(0),d=E),E++,T--):(y=1,E++,T--);for(;262>T&&!x;)yt()}e=(0==T&&(0!=y&&Lt(0,a[E-1]&255),kt(1),u=!0),f+wt(e,f+n,i-f))}return e},wt=function(n,r,u){var a,f,l;for(a=0;null!=t&&a<u;){f=u-a,f>t.len&&(f=t.len);for(l=0;l<f;l++)n[r+a+l]=t.ptr[t.off+l];t.off+=f,t.len-=f,a+=f,0==t.len&&(f=t,t=t.next,f.next=e,e=f)}if(a==u)return a;if(o<s){f=u-a,f>s-o&&(f=s-o);for(l=0;l<f;l++)n[r+a+l]=i[o+l];o+=f,a+=f,s==o&&(s=o=0)}return a},Et=function(){var e;for(e=0;286>e;e++)A[e].fc=0;for(e=0;30>e;e++)O[e].fc=0;for(e=0;19>e;e++)D[e].fc=0;A[256].fc=1,Q=$=J=K=Y=Z=0,G=1},St=function(e,t){for(var n=F[t],r=t<<1;r<=I;){r<I&&vt(e,F[r+1],F[r])&&r++;if(vt(e,n,F[r]))break;F[t]=F[r],t=r,r<<=1}F[t]=n},xt=function(e,t){var n=[16],r=0,i;for(i=1;15>=i;i++)r=r+j[i-1]<<1,n[i]=r;for(r=0;r<=t;r++)i=e[r].dl,0!=i&&(e[r].fc=Mt(n[i]++,i))},Tt=function(e){var t=e.dyn_tree,n=e.static_tree,r=e.elems,i,s=-1,o=r;I=0,q=573;for(i=0;i<r;i++)0!=t[i].fc?(F[++I]=s=i,R[i]=0):t[i].dl=0;for(;2>I;)i=F[++I]=2>s?++s:0,t[i].fc=1,R[i]=0,Y--,null!=n&&(Z-=n[i].dl);e.max_code=s;for(i=I>>1;1<=i;i--)St(t,i);do i=F[1],F[1]=F[I--],St(t,1),n=F[1],F[--q]=i,F[--q]=n,t[o].fc=t[i].fc+t[n].fc,R[i]>R[n]+1?R[o]=R[i]:R[o]=R[n]+1,t[i].dl=t[n].dl=o,F[1]=o++,St(t,1);while(2<=I);F[--q]=F[1],o=e.dyn_tree,i=e.extra_bits;var r=e.extra_base,n=e.max_code,u=e.max_length,a=e.static_tree,f,l,c,h,p=0;for(l=0;15>=l;l++)j[l]=0;o[F[q]].dl=0;for(e=q+1;573>e;e++)f=F[e],l=o[o[f].dl].dl+1,l>u&&(l=u,p++),o[f].dl=l,f>n||(j[l]++,c=0,f>=r&&(c=i[f-r]),h=o[f].fc,Y+=h*(l+c),null!=a&&(Z+=h*(a[f].dl+c)));if(0!=p){do{for(l=u-1;0==j[l];)l--;j[l]--,j[l+1]+=2,j[u]--,p-=2}while(0<p);for(l=u;0!=l;l--)for(f=j[l];0!=f;)i=F[--e],i>n||(o[i].dl!=l&&(Y+=(l-o[i].dl)*o[i].fc,o[i].fc=l),f--)}xt(t,s)},Nt=function(e,t){var n,r=-1,i,s=e[0].dl,o=0,u=7,a=4;0==s&&(u=138,a=3),e[t+1].dl=65535;for(n=0;n<=t;n++)i=s,s=e[n+1].dl,++o<u&&i==s||(o<a?D[i].fc+=o:0!=i?(i!=r&&D[i].fc++,D[16].fc++):10>=o?D[17].fc++:D[18].fc++,o=0,r=i,0==s?(u=138,a=3):i==s?(u=6,a=3):(u=7,a=4))},Ct=function(e,t){var n,r=-1,i,s=e[0].dl,o=0,u=7,a=4;0==s&&(u=138,a=3);for(n=0;n<=t;n++)if(i=s,s=e[n+1].dl,!(++o<u&&i==s)){if(o<a){do dt(i,D);while(0!=--o)}else 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v=[u];for(h=0;h<u;h++)v[h]=String.fromCharCode(p[h]);d[d.length]=v.join("")}return et=null,d.join("")}}()

Considerations
Note that some char codes cannot be zipped. I am not 100% sure why this is. ascii is 100% ok, but SOME intl char sometimes throw it. forgive me for not figuring this out in detail, feel free, but the issue is easy to work around using escape/unescape or window.btoa/atob where available/possible. I've never had an issue using it since i figured out that much about the problem.


if you are storing plain text and json, you're fine.
binary and intl chars will need dumbed-down before zipping.
Even in that case, even with the escape overhead, zipping still saves a lot of space; escape only fattens the zip ~10-20%.

here is a usage example, proof of operation, and a demo of the intl complication:


Usage

// run in firebug/devtools/"F12" on http://www.codingforums.com/showthread.php?t=283110
function testZip(str){
  return inflate(deflate(str))==str;
}

testZip(document.head.outerHTML); // true
testZip(document.body.outerHTML); // false
testZip(escape(document.body.outerHTML)); // true

deflate() is akin to escape() and inflate() is akin to unescape().


Performance


compression:

• BYTES string source // note
• 83,816 document.body.outerHTML.length // orig
• 18,941 deflate(document.body.outerHTML).length // (non-operational)
• 21,406 deflate(escape(document.body.outerHTML)).length //works

that's about 4:1 on fairly non-repetitive HTML. JSON usually give me 5:1, and HTML tables can go up to 20:1. Elegant plain text is lucky to get 3:1. You can expect at least a doubling of the amount you can store, so 10mb is the new 5mb.

CPU usage:
my timings on 30,000 bytes of pretty repetitive json, running on a cheap year-old desktop:

• 0.09ms deflate (30kb _> 1.3kb)
• 0.13ms inflate (1.3kb _> 30kb)

notes


even on a phone 1/100th the speed of my desktop, we are talking about 13ms to inflate the data. the iphone 4S tests at about 1/13th of my desktop for comparison. so, on the iphone, this should happen in ~2ms. jquery.js might take 10ms on that device, not a humanly-perceivable delay.


bigger payloads will take more time, in a linear fashion, but they will also compresses with more efficiency. 105kb when compressed is more than 5kb smaller than 100kb when compressed. in fact, it would likely add less than 5% to the compressed size because of existing repetition.


breaking the data into chunks can reduce CPU at the cost of disk.
it WILL take a noticeable while to deflate 5mb of text on a smartphone. If you are trying to do this often, or at a bad time, say, onkeypress, your app will grind to a halt. If you had 10 different 500kb packages, you would only have to touch ~1/10th the data, and your pauses would be 10th as long.



you can use deflate() solely in your build process and tuck inflate() into your distribute-able package for smaller downloads.


usually the additional inflate CPU overhead is less time than downloading the extra uncompressed data would have been. This remains true on "under-powered" smartphones because their network, even at 4g is slow.


keep in mind that shipping a zipped package will reduce the efficiency of server-based transparent gzip transfer encoding. This is for (hopefully) obvious reasons. it's not like it hurts, you're still saving a ton compared to the orig. the zip/zip overhead is only about 10%, and given the advantage of being able to persist the compressed version client side, i think it's almost always worth it. a lot of servers don't even gzip or cache JS files, so that is not an issue for many.


if you server doesn't support gzip at all, you can probably get better app loading perf by zipping all your CSS files into one string, and using a javascript "addCSSasString()" type method. same benefits for JS.



one cool thing is that is when you ship, say jQuery.js as a zipped string, you can save the whole lib to localStorage. with a conditional adder like yepnope or whatever, you can load jquery locally upon the next visit instead of pinging the server to check the HTTP cache status, or even downloading it each time on a non-caching server. i've measured many a big improvement on production sites where i've rolled the pattern out, despite a few naysayers slamming localStorage performance a couple years ago...

here is an example of deploying code like that: http://danml.com/js/?compression,mode=json
as opposed to http://danml.com/js/compression.js or http://danml.com/js/?compression

to use that url's specific functionality, you have to define App and App.X, but then, any and all externally-loaded code is available in App.X, which is one JSON.stringify() away from persistence.
you should modify you own code server to dish out the callbacks or containers that your projects use.



In conclusion, enjoy and let me know what you think of it.