janl commented on issue #3517:
URL: https://github.com/apache/couchdb/issues/3517#issuecomment-905412556
I’ve attempted a quick demo that caches the transpilation inside the JS
process, this would still do one transpile per couchjs process, but should
still be a lot better.
@konrad-ohms or @nickva would you be able to retry this with the original
setup?
```
diff --git a/share/server/60/rewrite_fun.js b/share/server/60/rewrite_fun.js
index 1b27a9d14..9b85f953f 100644
--- a/share/server/60/rewrite_fun.js
+++ b/share/server/60/rewrite_fun.js
@@ -15,30 +15,39 @@
//
//
https://github.com/dmunch/couch-chakra/blob/master/js/normalizeFunction.js
+
+const cache = {}
function rewriteFunInt(fun) {
- const ast = esprima.parse(fun);
- let idx = ast.body.length - 1;
- let decl = {};
-
- // Search for the first FunctionDeclaration beginning from the end
- do {
- decl = ast.body[idx--];
- } while (idx >= 0 && decl.type !== "FunctionDeclaration");
- idx++;
-
- // If we have a function declaration without an Id, wrap it
- // in an ExpressionStatement and change it into
- // a FuntionExpression
- if (decl.type == "FunctionDeclaration" && decl.id == null) {
- decl.type = "FunctionExpression";
- ast.body[idx] = {
- type: "ExpressionStatement",
- expression: decl
- };
- }
+ const crc = crc32_str(fun)
+ if (cache[crc]) {
+ return cache[crc];
+ } else {
+ const ast = esprima.parse(fun);
+ let idx = ast.body.length - 1;
+ let decl = {};
+
+ // Search for the first FunctionDeclaration beginning from the end
+ do {
+ decl = ast.body[idx--];
+ } while (idx >= 0 && decl.type !== "FunctionDeclaration");
+ idx++;
+
+ // If we have a function declaration without an Id, wrap it
+ // in an ExpressionStatement and change it into
+ // a FuntionExpression
+ if (decl.type == "FunctionDeclaration" && decl.id == null) {
+ decl.type = "FunctionExpression";
+ ast.body[idx] = {
+ type: "ExpressionStatement",
+ expression: decl
+ };
+ }
- // Generate source from the rewritten AST
- return escodegen.generate(ast);
+ // Generate source from the rewritten AST
+ const gen = escodegen.generate(ast);
+ cache[crc] = gen;
+ return gen;
+ }
}
@@ -53,4 +62,51 @@ function rewriteFuns(funsJSON) {
return rewriteFunInt(fun);
});
return JSON.stringify(results);
-}
\ No newline at end of file
+}
+
+// nicked from https://github.com/SheetJS/js-crc32/blob/master/crc32.js
+
+function signed_crc_table() {
+ var c = 0, table = new Array(256);
+
+ for(var n =0; n != 256; ++n){
+ c = n;
+ c = ((c&1) ? (-306674912 ^ (c >>> 1)) : (c >>> 1));
+ c = ((c&1) ? (-306674912 ^ (c >>> 1)) : (c >>> 1));
+ c = ((c&1) ? (-306674912 ^ (c >>> 1)) : (c >>> 1));
+ c = ((c&1) ? (-306674912 ^ (c >>> 1)) : (c >>> 1));
+ c = ((c&1) ? (-306674912 ^ (c >>> 1)) : (c >>> 1));
+ c = ((c&1) ? (-306674912 ^ (c >>> 1)) : (c >>> 1));
+ c = ((c&1) ? (-306674912 ^ (c >>> 1)) : (c >>> 1));
+ c = ((c&1) ? (-306674912 ^ (c >>> 1)) : (c >>> 1));
+ table[n] = c;
+ }
+
+ return typeof Int32Array !== 'undefined' ? new Int32Array(table) :
table;
+}
+
+var T = signed_crc_table();
+
+function crc32_str(str, seed) {
+ var C = seed ^ -1;
+ for(var i = 0, L=str.length, c, d; i < L;) {
+ c = str.charCodeAt(i++);
+ if(c < 0x80) {
+ C = (C>>>8) ^ T[(C ^ c)&0xFF];
+ } else if(c < 0x800) {
+ C = (C>>>8) ^ T[(C ^ (192|((c>>6)&31)))&0xFF];
+ C = (C>>>8) ^ T[(C ^ (128|(c&63)))&0xFF];
+ } else if(c >= 0xD800 && c < 0xE000) {
+ c = (c&1023)+64; d = str.charCodeAt(i++)&1023;
+ C = (C>>>8) ^ T[(C ^ (240|((c>>8)&7)))&0xFF];
+ C = (C>>>8) ^ T[(C ^ (128|((c>>2)&63)))&0xFF];
+ C = (C>>>8) ^ T[(C ^
(128|((d>>6)&15)|((c&3)<<4)))&0xFF];
+ C = (C>>>8) ^ T[(C ^ (128|(d&63)))&0xFF];
+ } else {
+ C = (C>>>8) ^ T[(C ^ (224|((c>>12)&15)))&0xFF];
+ C = (C>>>8) ^ T[(C ^ (128|((c>>6)&63)))&0xFF];
+ C = (C>>>8) ^ T[(C ^ (128|(c&63)))&0xFF];
+ }
+ }
+ return C ^ -1;
+}
```
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