diff --git a/ext/wasm/EXPORTED_FUNCTIONS.fiddle.in b/ext/wasm/EXPORTED_FUNCTIONS.fiddle.in
index 392e36e842..96df7c8713 100644
--- a/ext/wasm/EXPORTED_FUNCTIONS.fiddle.in
+++ b/ext/wasm/EXPORTED_FUNCTIONS.fiddle.in
@@ -5,4 +5,5 @@ _fiddle_experiment
 _fiddle_interrupt
 _fiddle_main
 _fiddle_reset_db
-_fiddle_the_db
+_fiddle_db_handle
+_fiddle_db_is_opfs
diff --git a/ext/wasm/api/sqlite3-api-glue.js b/ext/wasm/api/sqlite3-api-glue.js
index 847bf7bc2c..49f736669d 100644
--- a/ext/wasm/api/sqlite3-api-glue.js
+++ b/ext/wasm/api/sqlite3-api-glue.js
@@ -185,9 +185,20 @@ self.sqlite3ApiBootstrap.initializers.push(function(sqlite3){
         capi[e[0]] = e[1];
       }
     }
+    const __rcMap = Object.create(null);
+    for(const t of ['resultCodes']){
+      for(const e of Object.entries(wasm.ctype[t])){
+        __rcMap[e[1]] = e[0];
+      }
+    }
+    /**
+       For the given integer, returns the SQLITE_xxx result code as a
+       string, or undefined if no such mapping is found.
+    */
+    capi.sqlite3_wasm_rc_str = (rc)=>__rcMap[rc];
     /* Bind all registered C-side structs... */
     for(const s of wasm.ctype.structs){
       capi[s.name] = sqlite3.StructBinder(s);
     }
-  }
+  }/*end C constant imports*/
 });
diff --git a/ext/wasm/api/sqlite3-api-opfs.js b/ext/wasm/api/sqlite3-api-opfs.js
index f69e162c7e..2c22c03f7d 100644
--- a/ext/wasm/api/sqlite3-api-opfs.js
+++ b/ext/wasm/api/sqlite3-api-opfs.js
@@ -999,11 +999,14 @@ sqlite3.installOpfsVfs = function callee(asyncProxyUri = callee.defaultProxyUri)
                 warn("Running sanity checks because of opfs-sanity-check URL arg...");
                 sanityCheck();
               }
-              W.onerror = W._originalOnError;
-              delete W._originalOnError;
-              sqlite3.opfs = opfsUtil;
-              log("End of OPFS sqlite3_vfs setup.", opfsVfs);
-              promiseResolve(sqlite3);
+              navigator.storage.getDirectory().then((d)=>{
+                W.onerror = W._originalOnError;
+                delete W._originalOnError;
+                sqlite3.opfs = opfsUtil;
+                opfsUtil.rootDirectory = d;
+                log("End of OPFS sqlite3_vfs setup.", opfsVfs);
+                promiseResolve(sqlite3);
+              });
             }catch(e){
               error(e);
               promiseReject(e);
diff --git a/ext/wasm/fiddle/fiddle-worker.js b/ext/wasm/fiddle/fiddle-worker.js
index 827d2cfa90..5da09257d4 100644
--- a/ext/wasm/fiddle/fiddle-worker.js
+++ b/ext/wasm/fiddle/fiddle-worker.js
@@ -99,7 +99,9 @@
         };
   const stdout = (...args)=>wMsg('stdout', args);
   const stderr = (...args)=>wMsg('stderr', args);
-
+  const toss = (...args)=>{
+    throw new Error(args.join(' '));
+  };
   const fixmeOPFS = "(FIXME: won't work with vanilla OPFS.)";
   
   self.onerror = function(/*message, source, lineno, colno, error*/) {
@@ -136,7 +138,7 @@
       const S = fiddleModule.sqlite3;
       /* We need to call sqlite3_shutdown() in order to avoid numerous
          legitimate warnings from the shell about it being initialized
-         after sqlite3_initialize() has been called. This mean ,
+         after sqlite3_initialize() has been called. This means,
          however, that any initialization done by the JS code may need
          to be re-done (e.g.  re-registration of dynamically-loaded
          VFSes). */
@@ -156,7 +158,7 @@
       if(S.opfs){
         stdout("\nOPFS is available. To open a persistent db, use:\n\n",
                "  .open file:name?vfs=opfs\n\nbut note that some",
-               "features (e.g. export) do not yet work with OPFS.");
+               "features (e.g. upload) do not yet work with OPFS.");
         S.opfs.reregisterVfs();
       }
       stdout('\nEnter ".help" for usage hints.');
@@ -207,6 +209,69 @@
       f._();
     }
   };
+
+  /**
+     Exports the shell's current db file in such a way that it can
+     export DBs hosted in the Emscripten-supplied FS or in native OPFS
+     (and, hypothetically, kvvfs). Throws on error. On success returns
+     a Blob containing the whole db contents.
+
+     Bug: xFileSize() is returning garbage for the default VFS but
+     works in OPFS. Thus for exporting that impl we'll use the
+     fiddleModule.FS API for the time being.
+  */
+  const exportDbFileToBlob = function(){
+    const S = fiddleModule.sqlite3, capi = S.capi, wasm = capi.wasm;
+    const pDb = wasm.xCall("fiddle_db_handle");
+    if(!pDb) toss("No db is opened.");
+    const scope = wasm.scopedAllocPush();
+    try{
+      const ppFile = wasm.scopedAlloc(12/*sizeof(i32 + i64)*/);
+      const pFileSize = ppFile + 4;
+      wasm.setMemValue(ppFile, 0, 'i32');
+      let rc = capi.sqlite3_file_control(
+        pDb, "main", capi.SQLITE_FCNTL_FILE_POINTER, ppFile
+      );
+      if(rc) toss("Cannot get sqlite3_file handle.");
+      const jFile = new capi.sqlite3_file(wasm.getPtrValue(ppFile));
+      const jIom = new capi.sqlite3_io_methods(jFile.$pMethods);
+      console.warn("jIom =",jIom);
+      const xFileSize = wasm.functionEntry(jIom.$xFileSize);
+      const xRead = wasm.functionEntry(jIom.$xRead);
+      wasm.setMemValue(pFileSize, 0n, 'i64');
+      //stderr("nFileSize =",wasm.getMemValue(pFileSize,'i64'),"pFileSize =",pFileSize);
+      rc = xFileSize( jFile.pointer, pFileSize );
+      if(rc) toss("Cannot get db file size.");
+      //stderr("nFileSize =",wasm.getMemValue(pFileSize,'i64'),"pFileSize =",pFileSize);
+      const nFileSize = Number( wasm.getMemValue(pFileSize,'i64') );
+      if(nFileSize <= 0n || nFileSize>=Number.MAX_SAFE_INTEGER){
+        toss("Unexpected DB size:",nFileSize);
+      }
+      //stderr("nFileSize =",nFileSize,"pFileSize =",pFileSize);
+      const nIobuf = 1024 * 4;
+      const iobuf = wasm.scopedAlloc(nIobuf);
+      let nPos = 0;
+      const blobList = [];
+      const heap = wasm.heap8u();
+      for( ; nPos < nFileSize; nPos += nIobuf ){
+        rc = xRead(jFile.pointer, iobuf, nIobuf, BigInt(nPos));
+        if(rc){
+          if(capi.SQLITE_IOERR_SHORT_READ === rc){
+            //stderr('rc =',rc,'nPos =',nPos,'nIobuf =',nIobuf,'nFileSize =',nFileSize);
+            rc = ((nPos + nIobuf) < nFileSize) ? rc : 0/*assume EOF*/;
+          }
+          if(rc) toss("xRead() SQLITE_xxx error #"+rc,capi.sqlite3_wasm_rc_str(rc));
+        }
+        blobList.push(heap.slice(iobuf, iobuf+nIobuf));
+      }
+      return new Blob(blobList);
+    }catch(e){
+      console.error('exportDbFileToBlob()',e);
+      stderr("exportDbFileToBlob():",e.message);
+    }finally{
+      wasm.scopedAllocPop(scope);
+    }
+  }/*exportDbFileToBlob()*/;
   
   self.onmessage = function f(ev){
     ev = ev.data;
@@ -233,14 +298,22 @@
           */
         case 'db-export': {
           const fn = Sqlite3Shell.dbFilename();
-          stdout("Exporting",fn+".",fixmeOPFS);
+          stdout("Exporting",fn+".");
           const fn2 = fn ? fn.split(/[/\\]/).pop() : null;
           try{
             if(!fn2) throw new Error("DB appears to be closed.");
-            const buffer = fiddleModule.FS.readFile(
-              fn, {encoding:"binary"}
-            ).buffer;
-            wMsg('db-export',{filename: fn2, buffer}, [buffer]);
+            if(fiddleModule.sqlite3.capi.wasm.xCall(
+              'fiddle_db_is_opfs'
+            )){
+              exportDbFileToBlob().arrayBuffer().then((buffer)=>{
+                wMsg('db-export',{filename: fn2, buffer}, [buffer]);
+              });
+            }else{
+              const buffer = fiddleModule.FS.readFile(
+                fn, {encoding:"binary"}
+              ).buffer;
+              wMsg('db-export',{filename: fn2, buffer}, [buffer]);
+            }
           }catch(e){
             /* Post a failure message so that UI elements disabled
                during the export can be re-enabled. */
diff --git a/ext/wasm/index.html b/ext/wasm/index.html
index 7b541a6457..ee31306bb7 100644
--- a/ext/wasm/index.html
+++ b/ext/wasm/index.html
@@ -15,40 +15,49 @@
       "make"d first. The intent is that <em>this</em> page be run
       using:</div>
     <blockquote><pre>althttpd -page index.html</pre></blockquote>
-    <div>and the individual tests be started in their own tab.</div>
-    <div>Warnings and Caveats:
+    <div>and the individual tests be started in their own tab.
+      Warnings and Caveats:
       <ul class='warning'>
         <li>Some of these pages require that
-          the web server emit the so-called COOP and COEP headers. The
-          default build of althttpd <em>does not</em>.
+          the web server emit the so-called
+          <a href='https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Cross-Origin-Opener-Policy'>COOP</a>
+          and
+          <a href='https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Cross-Origin-Embedder-Policy'>COEP</a>
+          headers. The default build
+          of <a href='https://sqlite.org/althttpd'>althttpd</a>
+          <em>does not</em>.
+        </li>
+        <li>Any OPFS-related pages require very recent version of
+          Chrome or Chromium (v102 at least, possibly newer). OPFS
+          support in the other major browsers is pending. Development
+          and testing is currently done against a dev-channel release
+          of Chrome (v107 as of 2022-09-26).
         </li>
-        <li>Any OPFS-related pages require very recent
-          version of Chrome or Chromium (v102 at least, possibly
-          newer). OPFS support in the other major browsers is
-          pending.</li>
         <li>Whether or not WASMFS/OPFS support is enabled on any given
           page may depend on build-time options which are <em>off by
           default</em> because they currently (as of 2022-09-08) break
-          with Worker-based pages. Similarly, WASMFS does not work on
-          some platforms, e.g. Raspberry Pi 4.
+          with Worker-based pages.
+          <!-- Similarly, WASMFS does not work on some platforms,
+               e.g. Raspberry Pi 4 (for which there is no Chrome
+               build, so it's currently a moot point). -->
         </li>
       </ul>
     </div>
-    <div>The tests...
+    <div>The tests and demos...
       <ul id='test-list'>
         <li>High-level apps and demos...
           <ul>
             <li><a href='fiddle/fiddle.html'>fiddle</a> is an HTML front-end
               to a wasm build of the sqlite3 shell.</li>
             <li><a href='demo-123.html'>demo-123</a> provides a
-              no-nonsense example of adding sqlite3 support to a
-              web page. </li>
-            <li><a href='demo-123-worker.html'>demo-123-worker</a> is the
-              same as <code>demo-123</code> but loads and run sqlite3 from
-              a Worker thread.</li>
+              no-nonsense example of adding sqlite3 support to a web
+              page in the UI thread.</li>
+            <li><a href='demo-123-worker.html'>demo-123-worker</a> is
+              the same as <code>demo-123</code> but loads and runs
+              sqlite3 from a Worker thread.</li>
             <li><a href='demo-kvvfs1.html'>demo-kvvfs1</a>: very basic
-              demo of using the key-value vfs for storing a persistent db
-              in JS localStorage or sessionStorage.</li>
+              demo of using the key-value VFS for storing a persistent db
+              in JS <code>localStorage</code> or <code>sessionStorage</code>.</li>
           </ul>
         </li>
         <li>speedtest1 ports (sqlite3's primary benchmarking tool)...
diff --git a/ext/wasm/jaccwabyt/jaccwabyt.md b/ext/wasm/jaccwabyt/jaccwabyt.md
index 2bb39e636f..edcba260a7 100644
--- a/ext/wasm/jaccwabyt/jaccwabyt.md
+++ b/ext/wasm/jaccwabyt/jaccwabyt.md
@@ -809,9 +809,7 @@ common:
   A read-only numeric property which is the "pointer" returned by the
   configured allocator when this object is constructed. After
   `dispose()` (inherited from [StructType][]) is called, this property
-  has the `undefined` value. When passing instances of this struct to
-  C-bound code, `pointer` is the value which must be passed in place
-  of a C-side struct pointer. When calling C-side code which takes a
+  has the `undefined` value. When calling C-side code which takes a
   pointer to a struct of this type, simply pass it `myStruct.pointer`.
 
 <a name='appendices'></a>
diff --git a/manifest b/manifest
index 4778b3cf4b..31376ee0cc 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C wasm:\schange\sStructBinder\ssignature\sfor\ssqlite3_file::pMethods\sfrom\s'P'\sto\s'p'\sto\seliminate\san\sunnecessary\sand\sinconsistent\slevel\sof\smagic.
-D 2022-09-26T11:34:31.822
+C Get\sfiddle\sdb\sexport\sworking\sfor\sOPFS\sVFS.\sAdd\sroot\sdir\shandle\sto\sthe\smain\sOPFS\sVFS\sworker\sto\senable\screation\sof\scertain\sutility\sfunctions\swithout\sdelegating\sto\sthe\sasync\sworker.\sAdd\ssqlite3.capi.sqlite3_wasm_rc_str()\sto\smap\sinteger\sresult\scodes\sback\sto\stheir\sSQLITE_xxx\scounterparts.\sMinor\sdoc\stouchups.
+D 2022-09-26T11:38:58.930
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -472,7 +472,7 @@ F ext/session/test_session.c f433f68a8a8c64b0f5bc74dc725078f12483301ad4ae8375205
 F ext/userauth/sqlite3userauth.h 7f3ea8c4686db8e40b0a0e7a8e0b00fac13aa7a3
 F ext/userauth/user-auth.txt e6641021a9210364665fe625d067617d03f27b04
 F ext/userauth/userauth.c 7f00cded7dcaa5d47f54539b290a43d2e59f4b1eb5f447545fa865f002fc80cb
-F ext/wasm/EXPORTED_FUNCTIONS.fiddle.in 105f6f7f211f49dea8fa6ee8b7b56492d5f9237ab0d1c1b3c970df11e4d0df02
+F ext/wasm/EXPORTED_FUNCTIONS.fiddle.in 48af0d812e2e1099798ae0e27f1d4836d572d0d068c83b3e2088ef4d97c45c2f
 F ext/wasm/EXPORTED_RUNTIME_METHODS.fiddle 0e88c8cfc3719e4b7e74980d9da664c709e68acf863e48386cda376edfd3bfb0
 F ext/wasm/GNUmakefile 34a84e30e6b25e24959a8264e9dec020dffa82d96879dc55ad65d3c31c95d3b1
 F ext/wasm/README.md e1ee1e7c321c6a250bf78a84ca6f5882890a237a450ba5a0649c7a8399194c52
@@ -482,9 +482,9 @@ F ext/wasm/api/README.md d876597edd2b9542b6ea031adaaff1c042076fde7b670b1dc6d8a87
 F ext/wasm/api/post-js-footer.js b64319261d920211b8700004d08b956a6c285f3b0bba81456260a713ed04900c
 F ext/wasm/api/post-js-header.js 2e5c886398013ba2af88028ecbced1e4b22dc96a86467f1ecc5ba9e64ef90a8b
 F ext/wasm/api/sqlite3-api-cleanup.js 8564a6077cdcaea9a9f428a019af8a05887f0131e6a2a1e72a7ff1145fadfe77
-F ext/wasm/api/sqlite3-api-glue.js cfff894bdf98a6c579975d09dd45471b0e3399f08a6f9e44a22646e8403196ed
+F ext/wasm/api/sqlite3-api-glue.js fe5ca21ac519e6411f5e7a6403d06fe92c51ef81cca8e07ea8895df8ec9c2e4e
 F ext/wasm/api/sqlite3-api-oo1.js f974e79d9af8f26bf33928c5730b0988cc706d14f59a5fe36394739b92249841
-F ext/wasm/api/sqlite3-api-opfs.js 5585dc80aea9df54c3d5d3a6c62771bf741f21b23706330ba62571c57ec07abf
+F ext/wasm/api/sqlite3-api-opfs.js 151f8bab445915dd4fa8fe3329accc5250351e7bf0af1518cb5cc49886c123d2
 F ext/wasm/api/sqlite3-api-prologue.js 76db12cce58ec6724ec01a977dfbedabfd4916e915a6e7679ffc24dd52eef64e
 F ext/wasm/api/sqlite3-api-worker1.js 2eeb2a24e1a90322d84a9b88a99919b806623de62792436446099c0988f2030b
 F ext/wasm/api/sqlite3-wasi.h 25356084cfe0d40458a902afb465df8c21fc4152c1d0a59b563a3fba59a068f9
@@ -502,12 +502,12 @@ F ext/wasm/demo-kvvfs1.html 7d4f28873de67f51ac18c584b7d920825139866a96049a49c424
 F ext/wasm/demo-kvvfs1.js e884ea35022d772c0d1dd884b40011413696438394f605c6cd4808cfb1642a4a
 F ext/wasm/fiddle.make fd56fa21bada6ecbf860686a9a789ebda7cc3d9b60835927000fcb00246ea50f
 F ext/wasm/fiddle/emscripten.css 3d253a6fdb8983a2ac983855bfbdd4b6fa1ff267c28d69513dd6ef1f289ada3f
-F ext/wasm/fiddle/fiddle-worker.js d3e4d1e442a9a86cc34f8bd646059d848cf3345b5220883379268b03b3c3cdfa
+F ext/wasm/fiddle/fiddle-worker.js 42c31065660e57844afa796bcf120666348c060fc4c656c335151b62da7fc60d
 F ext/wasm/fiddle/fiddle.html 5daf54e8f3d7777cbb1ca4f93affe28858dbfff25841cb4ab81d694efed28ec2
 F ext/wasm/fiddle/fiddle.js aa44051be6e48c53fd23c829177d43f557dcc6f0998ccfcbae7c473ff405f0c6
-F ext/wasm/index.html 8b4b7ea052d558262c8466f94326fb455c21049b2d1d3577ed0a5fce15101ba8
+F ext/wasm/index.html a39d14f6de6bd1294d39522fcf40eca3c9f0b6da44bb8df6948378e9f30468f5
 F ext/wasm/jaccwabyt/jaccwabyt.js 0d7f32817456a0f3937fcfd934afeb32154ca33580ab264dab6c285e6dbbd215
-F ext/wasm/jaccwabyt/jaccwabyt.md 447cc02b598f7792edaa8ae6853a7847b8178a18ed356afacbdbf312b2588106
+F ext/wasm/jaccwabyt/jaccwabyt.md 9aa6951b529a8b29f578ec8f0355713c39584c92cf1708f63ba0cf917cb5b68e
 F ext/wasm/jaccwabyt/jaccwabyt_test.c 39e4b865a33548f943e2eb9dd0dc8d619a80de05d5300668e9960fff30d0d36f
 F ext/wasm/jaccwabyt/jaccwabyt_test.exports 5ff001ef975c426ffe88d7d8a6e96ec725e568d2c2307c416902059339c06f19
 F ext/wasm/scratchpad-wasmfs-main.html 20cf6f1a8f368e70d01e8c17200e3eaa90f1c8e1029186d836d14b83845fbe06
@@ -615,7 +615,7 @@ F src/random.c 546d6feb15ec69c1aafe9bb351a277cbb498fd5410e646add673acb805714960
 F src/resolve.c efea4e5fbecfd6d0a9071b0be0d952620991673391b6ffaaf4c277b0bb674633
 F src/rowset.c ba9515a922af32abe1f7d39406b9d35730ed65efab9443dc5702693b60854c92
 F src/select.c d69dfb5b082f9a25e6700e152ddb3d942359b847b1df504eb09f9b4531844f8d
-F src/shell.c.in c4625fa9493cf815ff15e62bee5af93e91bbdb1a0c4e2c5a34a3744df3d5daaf
+F src/shell.c.in 00a72221c8b2df823f3a9d712457ae8bebe627b5989fefa1ccfe099eafab5139
 F src/sqlite.h.in b9b7fd73239d94db20332bb6e504688001e5564b655e1318a4427a1caef4b99e
 F src/sqlite3.rc 5121c9e10c3964d5755191c80dd1180c122fc3a8
 F src/sqlite3ext.h a988810c9b21c0dc36dc7a62735012339dc76fc7ab448fb0792721d30eacb69d
@@ -2026,8 +2026,8 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P bcec4f964a7b02f59be05286ff715bac654a32b19f05a743e402f4cdb207cab8
-R 793f9e89b06d2236f21d1ef1114135f2
+P 85f2e877e53899860af4dc6630044b471a9c7c82faba1f4e1e60ae991460b943
+R 021d11845b25e048635a4d675c2c9f1f
 U stephan
-Z 73b30ac4eb53afa297401f4b1b820a88
+Z 684fe82520a24a3caf4c9fdd7b640f27
 # Remove this line to create a well-formed Fossil manifest.
diff --git a/manifest.uuid b/manifest.uuid
index 27efa67a09..2ef99b9942 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-85f2e877e53899860af4dc6630044b471a9c7c82faba1f4e1e60ae991460b943
\ No newline at end of file
+9b2244e1c8a40efe6547094a1b57acc8f2173145a8731abb0e36268ce0a8ef41
\ No newline at end of file
diff --git a/src/shell.c.in b/src/shell.c.in
index bafcc697f2..3e5a1c2168 100644
--- a/src/shell.c.in
+++ b/src/shell.c.in
@@ -12632,27 +12632,13 @@ int fiddle_experiment(int a,int b){
    return a + b;
 }
 
-/* Only for emcc experimentation purposes.
-
-  Define this function in JS using:
-
-  emcc ... --js-library somefile.js
-
-  containing:
-
-mergeInto(LibraryManager.library, {
-    my_foo: function(){
-        console.debug("my_foo()",arguments);
-    }
-});
+/*
+** Returns a pointer to the current DB handle.
 */
-/*extern void my_foo(sqlite3 *);*/
-/* Only for emcc experimentation purposes. */
-sqlite3 * fiddle_the_db(){
-    printf("fiddle_the_db(%p)\n", (const void*)globalDb);
-    /*my_foo(globalDb);*/
+sqlite3 * fiddle_db_handle(){
     return globalDb;
 }
+
 /* Only for emcc experimentation purposes. */
 sqlite3 * fiddle_db_arg(sqlite3 *arg){
     printf("fiddle_db_arg(%p)\n", (const void*)arg);
@@ -12702,6 +12688,55 @@ void fiddle_reset_db(void){
   sqlite3_free(zFilename);
 }
 
+/*
+** This is a bit of a workaround: returns true if the current db uses
+** the "opfs" VFS, else false.
+*/
+int fiddle_db_is_opfs(void){
+  sqlite3_vfs * pVfs = 0;
+  if( 0!=shellState.db ){
+    sqlite3_file_control( shellState.db, "main",
+                          SQLITE_FCNTL_VFS_POINTER, &pVfs );
+  }
+  return pVfs ? 0==strcmp("opfs", pVfs->zName) : 0;
+}
+
+#if 0
+/* TODO: test whether this impl works properly wrt xSize() in the
+** unix-none VFS. The JS impl works fine for OPFS but not unix-none
+** because xSize() is returning a garbage size.
+*/
+int fiddle_export_db( int (*callback)(unsigned const char *zOut, int n) ){
+  sqlite3_int64 nSize = 0;
+  sqlite3_int64 nPos = 0;
+  sqlite3_vfs * pVfs = 0;
+  sqlite3_file * pFile = 0;
+  unsigned char buf[1024 * 4];
+  const int nBuf = (int)sizeof(buf);
+  int rc = shellState.db
+    ? sqlite3_file_control(shellState.db, "main",
+                           SQLITE_FCNTL_VFS_POINTER, &pVfs)
+    : 0;
+  if( rc ) return rc;
+  else if( 0==pVfs ) return SQLITE_NOTFOUND;
+  rc = sqlite3_file_control(shellState.db, "main",
+                            SQLITE_FCNTL_FILE_POINTER, &pFile);
+  if( rc ) return rc;
+  rc = pFile->pMethods->xFileSize(pFile, &nSize);
+  if(rc) return rc;
+  for( ; 0==rc && nPos<nSize; nPos += nBuf ){
+    rc = pFile->pMethods->xRead(pFile, buf, nBuf, nPos);
+    if(SQLITE_IOERR_SHORT_READ == rc){
+      rc = (nPos + nBuf) < nSize ? rc : 0/*assume EOF*/;
+    }
+    if(rc) return rc;
+    nPos += nBuf;
+    rc = callback(buf, nBuf);
+  }
+  return rc;
+}
+#endif
+
 /*
 ** Trivial exportable function for emscripten. It processes zSql as if
 ** it were input to the sqlite3 shell and redirects all output to the