Split the JS vfs/vtab helper code into discreet units as a step towards a build which optionally elides those pieces. This is an internal restructuring change and does not affect the API.

FossilOrigin-Name: ede945fd2360097d9961b8a4b8fb48fea57399cb9163534ed1c3c6b86588b0a5

ext/wasm/api/sqlite3-vfs-helper.c-pp.js

@@ -0,0 +1,103 @@
+/*
+** 2022-11-30
+**
+** The author disclaims copyright to this source code.  In place of a
+** legal notice, here is a blessing:
+**
+** *   May you do good and not evil.
+** *   May you find forgiveness for yourself and forgive others.
+** *   May you share freely, never taking more than you give.
+*/
+
+/**
+   This file installs sqlite3.vfs, an object which exists to assist
+   in the creation of JavaScript implementations of sqlite3_vfs.
+*/
+'use strict';
+globalThis.sqlite3ApiBootstrap.initializers.push(function(sqlite3){
+  const wasm = sqlite3.wasm, capi = sqlite3.capi, toss = sqlite3.util.toss3;
+  const vfs = Object.create(null);
+  sqlite3.vfs = vfs;
+
+  /**
+     Uses sqlite3_vfs_register() to register this
+     sqlite3.capi.sqlite3_vfs. This object must have already been
+     filled out properly. If the first argument is truthy, the VFS is
+     registered as the default VFS, else it is not.
+
+     On success, returns this object. Throws on error.
+  */
+  capi.sqlite3_vfs.prototype.registerVfs = function(asDefault=false){
+    if(!(this instanceof sqlite3.capi.sqlite3_vfs)){
+      toss("Expecting a sqlite3_vfs-type argument.");
+    }
+    const rc = capi.sqlite3_vfs_register(this, asDefault ? 1 : 0);
+    if(rc){
+      toss("sqlite3_vfs_register(",this,") failed with rc",rc);
+    }
+    if(this.pointer !== capi.sqlite3_vfs_find(this.$zName)){
+      toss("BUG: sqlite3_vfs_find(vfs.$zName) failed for just-installed VFS",
+           this);
+    }
+    return this;
+  };
+
+  /**
+     A wrapper for
+     sqlite3.StructBinder.StructType.prototype.installMethods() or
+     registerVfs() to reduce installation of a VFS and/or its I/O
+     methods to a single call.
+
+     Accepts an object which contains the properties "io" and/or
+     "vfs", each of which is itself an object with following properties:
+
+     - `struct`: an sqlite3.StructBinder.StructType-type struct. This
+       must be a populated (except for the methods) object of type
+       sqlite3_io_methods (for the "io" entry) or sqlite3_vfs (for the
+       "vfs" entry).
+
+     - `methods`: an object mapping sqlite3_io_methods method names
+       (e.g. 'xClose') to JS implementations of those methods. The JS
+       implementations must be call-compatible with their native
+       counterparts.
+
+     For each of those object, this function passes its (`struct`,
+     `methods`, (optional) `applyArgcCheck`) properties to
+     installMethods().
+
+     If the `vfs` entry is set then:
+
+     - Its `struct` property's registerVfs() is called. The
+       `vfs` entry may optionally have an `asDefault` property, which
+       gets passed as the argument to registerVfs().
+
+     - If `struct.$zName` is falsy and the entry has a string-type
+       `name` property, `struct.$zName` is set to the C-string form of
+       that `name` value before registerVfs() is called. That string
+       gets added to the on-dispose state of the struct.
+
+     On success returns this object. Throws on error.
+  */
+  vfs.installVfs = function(opt){
+    let count = 0;
+    const propList = ['io','vfs'];
+    for(const key of propList){
+      const o = opt[key];
+      if(o){
+        ++count;
+        o.struct.installMethods(o.methods, !!o.applyArgcCheck);
+        if('vfs'===key){
+          if(!o.struct.$zName && 'string'===typeof o.name){
+            o.struct.addOnDispose(
+              o.struct.$zName = wasm.allocCString(o.name)
+            );
+          }
+          o.struct.registerVfs(!!o.asDefault);
+        }
+      }
+    }
+    if(!count) toss("Misuse: installVfs() options object requires at least",
+                    "one of:", propList);
+    return this;
+  };
+}/*sqlite3ApiBootstrap.initializers.push()*/);