From 4d20950dfab31528f959e6053729e19226c37ae3 Mon Sep 17 00:00:00 2001
From: gorhill <rhill@raymondhill.net>
Date: Sun, 5 Nov 2017 12:33:46 -0500
Subject: [PATCH] save investigative work for the future re. wasm

---
 src/js/hntrie.js | 123 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 123 insertions(+)

diff --git a/src/js/hntrie.js b/src/js/hntrie.js
index 3afe60ad1..7ba879c37 100644
--- a/src/js/hntrie.js
+++ b/src/js/hntrie.js
@@ -475,3 +475,126 @@ HNTrieBuilder.prototype.HNTrie32.prototype.matches = function(needle) {
         }
     }
 };
+
+/*******************************************************************************
+
+  Experimenting: WebAssembly version.
+  Developed using this simple online tool: https://wasdk.github.io/WasmFiddle/
+
+  >>> start of C code
+    unsigned short buffer[0];
+    int matches(int id, int cclen)
+    {
+        unsigned short* cc0 = &buffer[0];
+        unsigned short* cc = cc0 + cclen;
+        unsigned short* cell0 = &buffer[512+id];
+        unsigned short* cell = cell0;
+        unsigned short* ww;
+        int c1, c2, ccnt;
+        for (;;) {
+            c1 = cc <= cc0 ? 0 : *--cc;
+            for (;;) {
+                c2 = cell[2];
+                if ( c2 == c1 ) { break; }
+                if ( c2 == 0 && c1 == 0x2E ) { return 1; }
+                if ( cell[0] == 0 ) { return 0; }
+                cell = cell0 + cell[0];
+            }
+            if ( c1 == 0 ) { return 1; }
+            ccnt = cell[3];
+            if ( ccnt != 0 ) {
+                if ( cc - ccnt < cc0 ) { return 0; }
+                ww = cell + 4;
+                while ( ccnt-- ) {
+                    if ( *--cc != *ww++ ) { return 0; }
+                }
+            }
+            if ( cell[1] == 0 ) {
+                if ( cc == cc0 ) { return 1; }
+                if ( *--cc == 0x2E ) { return 1; }
+                return 0;
+            }
+            cell = cell0 + cell[1];
+        }
+    }
+    int getLinearMemoryOffset() {
+      return (int)&buffer[0];
+    }
+  <<< end of C code
+
+  Observations:
+  - When growing memory, we must re-create the typed array js-side. The content
+    of the array is preserved by grow().
+  - It's slower than the javascript version... Possible explanations:
+    - Call overhead: https://github.com/WebAssembly/design/issues/1120
+    - Having to copy whole input string in buffer before call.
+
+var HNTrie16wasm = (function() {
+    var module;
+    var instance;
+    var memory;
+    var memoryOrigin = 0;
+    var memoryUsed = 1024;
+    var cbuffer;
+    var tbuffer;
+    var tbufferSize = 0;
+    var matchesFn;
+
+    var init = function() {
+        module = new WebAssembly.Module(new Uint8Array([0,97,115,109,1,0,0,0,1,139,128,128,128,0,2,96,2,127,127,1,127,96,0,1,127,3,131,128,128,128,0,2,0,1,4,132,128,128,128,0,1,112,0,0,5,131,128,128,128,0,1,0,1,6,129,128,128,128,0,0,7,172,128,128,128,0,3,6,109,101,109,111,114,121,2,0,7,109,97,116,99,104,101,115,0,0,21,103,101,116,76,105,110,101,97,114,77,101,109,111,114,121,79,102,102,115,101,116,0,1,10,217,130,128,128,0,2,202,130,128,128,0,1,5,127,32,1,65,1,116,65,12,106,33,3,32,0,65,1,116,65,140,8,106,34,2,33,0,2,64,2,64,2,64,2,64,2,64,2,64,3,64,65,0,33,5,2,64,32,3,65,12,77,13,0,32,3,65,126,106,34,3,47,1,0,33,5,11,2,64,32,5,32,0,47,1,4,34,1,70,13,0,2,64,32,5,65,46,71,13,0,3,64,32,1,65,255,255,3,113,69,13,5,32,0,47,1,0,34,1,69,13,6,32,2,32,1,65,1,116,106,34,0,47,1,4,34,1,65,46,71,13,0,12,2,11,11,3,64,32,0,47,1,0,34,1,69,13,3,32,5,32,2,32,1,65,1,116,106,34,0,47,1,4,71,13,0,11,11,65,1,33,6,32,5,69,13,5,2,64,2,64,32,0,47,1,6,34,1,69,13,0,32,3,32,1,65,1,116,107,65,12,73,13,8,32,1,65,127,115,33,5,32,0,65,8,106,33,1,3,64,32,5,65,1,106,34,5,69,13,1,32,1,47,1,0,33,4,32,1,65,2,106,33,1,32,4,32,3,65,126,106,34,3,47,1,0,70,13,0,12,2,11,11,32,0,47,1,2,34,1,69,13,5,32,2,32,1,65,1,116,106,33,0,12,1,11,11,65,0,15,11,65,0,15,11,65,1,15,11,65,0,15,11,32,3,65,12,70,13,0,32,3,65,126,106,47,1,0,65,46,70,33,6,11,32,6,15,11,65,0,11,132,128,128,128,0,0,65,12,11]));
+        instance = new WebAssembly.Instance(module);
+        memory = instance.exports.memory;
+        memoryOrigin = instance.exports.getLinearMemoryOffset();
+        cbuffer = new Uint16Array(memory.buffer, memoryOrigin, 512);
+        tbuffer = new Uint16Array(memory.buffer, memoryOrigin + 1024);
+        memoryUsed = memoryOrigin + 1024;
+        matchesFn = instance.exports.matches;
+    };
+
+    return {
+        create: function(data) {
+            if ( module === undefined ) { init(); }
+            var bytesNeeded = memoryUsed + ((data.length * 2 + 3) & ~3);
+            if ( bytesNeeded > memory.buffer.byteLength ) {
+                memory.grow((bytesNeeded - memory.buffer.byteLength + 65535) >>> 16);
+                cbuffer = new Uint16Array(memory.buffer, memoryOrigin, 512);
+                tbuffer = new Uint16Array(memory.buffer, memoryOrigin + 1024);
+            }
+            for ( var i = 0, j = tbufferSize; i < data.length; i++, j++ ) {
+                tbuffer[j] = data[i];
+            }
+            var id = tbufferSize;
+            tbufferSize += data.length;
+            if ( tbufferSize & 1 ) { tbufferSize += 1; }
+            memoryUsed += tbufferSize * 2;
+            return id;
+        },
+        reset: function() {
+            module = undefined;
+            instance = undefined;
+            memory = undefined;
+            memory.grow(1);
+            memoryUsed = 1024;
+            cbuffer = undefined;
+            tbuffer = undefined;
+            tbufferSize = 0;
+        },
+        matches: function(id, hn) {
+            var len = hn.length;
+            if ( len > 512 ) {
+                hn = hn.slice(-512);
+                var pos = hn.indexOf('.');
+                if ( pos !== 0 ) {
+                    hn = hn.slice(pos + 1);
+                }
+                len = hn.length;
+            }
+            var needle = cbuffer, i = len;
+            while ( i-- ) {
+                needle[i] = hn.charCodeAt(i);
+            }
+            return matchesFn(id, len) === 1;
+        }
+    };
+})();
+*/