changed createLazyFile to only issue xhr requests when the file is accessed (fixes issue #1127)

1 files changed, 74 insertions, 51 deletions

diff --git a/src/library.js b/src/library.js
index 41796551..f22eaecf 100644
--- a/src/library.js
+++ b/src/library.js
@@ -296,74 +296,97 @@ LibraryManager.library = {
       if (typeof XMLHttpRequest !== 'undefined') {
         if (!ENVIRONMENT_IS_WORKER) throw 'Cannot do synchronous binary XHRs outside webworkers in modern browsers. Use --embed-file or --preload-file in emcc';
         // Lazy chunked Uint8Array (implements get and length from Uint8Array). Actual getting is abstracted away for eventual reuse.
-        var LazyUint8Array = function(chunkSize, length) {
-          this.length = length;
-          this.chunkSize = chunkSize;
+        var LazyUint8Array = function() {
+          this.lengthKnown = false;
           this.chunks = []; // Loaded chunks. Index is the chunk number
         }
         LazyUint8Array.prototype.get = function(idx) {
           if (idx > this.length-1 || idx < 0) {
             return undefined;
           }
-          var chunkOffset = idx % chunkSize;
-          var chunkNum = Math.floor(idx / chunkSize);
+          var chunkOffset = idx % this.chunkSize;
+          var chunkNum = Math.floor(idx / this.chunkSize);
           return this.getter(chunkNum)[chunkOffset];
         }
         LazyUint8Array.prototype.setDataGetter = function(getter) {
           this.getter = getter;
         }
-  
-        // Find length
-        var xhr = new XMLHttpRequest();
-        xhr.open('HEAD', url, false);
-        xhr.send(null);
-        if (!(xhr.status >= 200 && xhr.status < 300 || xhr.status === 304)) throw new Error("Couldn't load " + url + ". Status: " + xhr.status);
-        var datalength = Number(xhr.getResponseHeader("Content-length"));
-        var header;
-        var hasByteServing = (header = xhr.getResponseHeader("Accept-Ranges")) && header === "bytes";
+
+        LazyUint8Array.prototype.getLength = function() {
+            // Find length
+            var xhr = new XMLHttpRequest();
+            xhr.open('HEAD', url, false);
+            xhr.send(null);
+            if (!(xhr.status >= 200 && xhr.status < 300 || xhr.status === 304)) throw new Error("Couldn't load " + url + ". Status: " + xhr.status);
+            var datalength = Number(xhr.getResponseHeader("Content-length"));
+            var header;
+            var hasByteServing = (header = xhr.getResponseHeader("Accept-Ranges")) && header === "bytes";
 #if SMALL_XHR_CHUNKS
-        var chunkSize = 1024; // Chunk size in bytes
+            var chunkSize = 1024; // Chunk size in bytes
 #else
-        var chunkSize = 1024*1024; // Chunk size in bytes
+            var chunkSize = 1024*1024; // Chunk size in bytes
 #endif
-        if (!hasByteServing) chunkSize = datalength;
-  
-        // Function to get a range from the remote URL.
-        var doXHR = (function(from, to) {
-          if (from > to) throw new Error("invalid range (" + from + ", " + to + ") or no bytes requested!");
-          if (to > datalength-1) throw new Error("only " + datalength + " bytes available! programmer error!");
-  
-          // TODO: Use mozResponseArrayBuffer, responseStream, etc. if available.
-          var xhr = new XMLHttpRequest();
-          xhr.open('GET', url, false);
-          if (datalength !== chunkSize) xhr.setRequestHeader("Range", "bytes=" + from + "-" + to);
-  
-          // Some hints to the browser that we want binary data.
-          if (typeof Uint8Array != 'undefined') xhr.responseType = 'arraybuffer';
-          if (xhr.overrideMimeType) {
-            xhr.overrideMimeType('text/plain; charset=x-user-defined');
-          }
+            if (!hasByteServing) chunkSize = datalength;
+      
+            // Function to get a range from the remote URL.
+            var doXHR = (function(from, to) {
+              if (from > to) throw new Error("invalid range (" + from + ", " + to + ") or no bytes requested!");
+              if (to > datalength-1) throw new Error("only " + datalength + " bytes available! programmer error!");
+      
+              // TODO: Use mozResponseArrayBuffer, responseStream, etc. if available.
+              var xhr = new XMLHttpRequest();
+              xhr.open('GET', url, false);
+              if (datalength !== chunkSize) xhr.setRequestHeader("Range", "bytes=" + from + "-" + to);
+      
+              // Some hints to the browser that we want binary data.
+              if (typeof Uint8Array != 'undefined') xhr.responseType = 'arraybuffer';
+              if (xhr.overrideMimeType) {
+                xhr.overrideMimeType('text/plain; charset=x-user-defined');
+              }
+      
+              xhr.send(null);
+              if (!(xhr.status >= 200 && xhr.status < 300 || xhr.status === 304)) throw new Error("Couldn't load " + url + ". Status: " + xhr.status);
+              if (xhr.response !== undefined) {
+                return new Uint8Array(xhr.response || []);
+              } else {
+                return intArrayFromString(xhr.responseText || '', true);
+              }
+            });
+            var lazyArray = this;
+            lazyArray.setDataGetter(function(chunkNum) {
+              var start = chunkNum * chunkSize;
+              var end = (chunkNum+1) * chunkSize - 1; // including this byte
+              end = Math.min(end, datalength-1); // if datalength-1 is selected, this is the last block
+              if (typeof(lazyArray.chunks[chunkNum]) === "undefined") {
+                lazyArray.chunks[chunkNum] = doXHR(start, end);
+              }
+              if (typeof(lazyArray.chunks[chunkNum]) === "undefined") throw new Error("doXHR failed!");
+              return lazyArray.chunks[chunkNum];
+            });
+
+            this._length = datalength;
+            this._chunkSize = chunkSize;
+            this.lengthKnown = true;
+        }
   
-          xhr.send(null);
-          if (!(xhr.status >= 200 && xhr.status < 300 || xhr.status === 304)) throw new Error("Couldn't load " + url + ". Status: " + xhr.status);
-          if (xhr.response !== undefined) {
-            return new Uint8Array(xhr.response || []);
-          } else {
-            return intArrayFromString(xhr.responseText || '', true);
-          }
+        var lazyArray = new LazyUint8Array();
+        Object.defineProperty(lazyArray, "length", {
+            get: function() {
+                if(!this.lengthKnown) {
+                    this.getLength();
+                }
+                return this._length;
+            }
         });
-  
-        var lazyArray = new LazyUint8Array(chunkSize, datalength);
-        lazyArray.setDataGetter(function(chunkNum) {
-          var start = chunkNum * lazyArray.chunkSize;
-          var end = (chunkNum+1) * lazyArray.chunkSize - 1; // including this byte
-          end = Math.min(end, datalength-1); // if datalength-1 is selected, this is the last block
-          if (typeof(lazyArray.chunks[chunkNum]) === "undefined") {
-            lazyArray.chunks[chunkNum] = doXHR(start, end);
-          }
-          if (typeof(lazyArray.chunks[chunkNum]) === "undefined") throw new Error("doXHR failed!");
-          return lazyArray.chunks[chunkNum];
+        Object.defineProperty(lazyArray, "chunkSize", {
+            get: function() {
+                if(!this.lengthKnown) {
+                    this.getLength();
+                }
+                return this._chunkSize;
+            }
         });
+
         var properties = { isDevice: false, contents: lazyArray };
       } else {
         var properties = { isDevice: false, url: url };