Add µBlock.staticNetFilteringEngine.bucketHistogram() as investigative dev tool

Additionally, lower the treshold of trieability to 4 for FilterPlainPrefix1.

src/js/static-net-filtering.js

@@ -1286,7 +1286,7 @@ const FilterBucket = class {
                     FilterPlainPrefix1.trieableStringFromArgs(fdata)
                 );
             }
-            if ( this.plainPrefix1Count === 7 ) {
+            if ( this.plainPrefix1Count === 3 ) {
                 this.plainPrefix1Trie = FilterBucket.trieContainer.createOne();
                 this._transferTrieable(
                     this.plainPrefix1Id,
@@ -2867,6 +2867,23 @@ FilterContainer.prototype.benchmark = function(action) {
 
 /******************************************************************************/
 
+FilterContainer.prototype.bucketHistogram = function() {
+    const results = [];
+    for ( const [ bits, category ] of this.categories ) {
+        for ( const [ th, f ] of category ) {
+            if ( f instanceof FilterBucket === false ) { continue; }
+            const token = µBlock.urlTokenizer.stringFromTokenHash(th);
+            results.push({ bits, token, size: f.size, f });
+        }
+    }
+    results.sort((a, b) => {
+        return b.size - a.size;
+    });
+    console.log(results);
+};
+
+/******************************************************************************/
+
 return new FilterContainer();
 
 /******************************************************************************/

src/js/utils.js

@@ -75,6 +75,19 @@
         return th;
     },
 
+    stringFromTokenHash: function(th) {
+        if ( th === 0 ) { return ''; }
+        if ( th === 63 ) { return '*'; }
+        if ( th === 62 ) { return '.'; }
+        const chars = '0123456789%abcdefghijklmnopqrstuvwxyz';
+        let s = '';
+        while ( th > 0 ) {
+            s = `${chars.charAt((th & 0b111111)-1)}${s}`;
+            th /= 64;
+        }
+        return s;
+    },
+
     // https://github.com/chrisaljoudi/uBlock/issues/1118
     // We limit to a maximum number of tokens.