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rustdoc-search: add descriptive comments to bitmap class

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Michael Howell 2024-11-18 13:37:53 -07:00
parent 3fbcc1f4b9
commit 826d023561
1 changed files with 23 additions and 0 deletions
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23
src/librustdoc/html/static/js/search.js
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@ -988,6 +988,12 @@ class VlqHexDecoder {
} }
class RoaringBitmap { class RoaringBitmap {
constructor(str) { constructor(str) {
// https://github.com/RoaringBitmap/RoaringFormatSpec
//
// Roaring bitmaps are used for flags that can be kept in their
// compressed form, even when loaded into memory. This decoder
// turns the containers into objects, but uses byte array
// slices of the original format for the data payload.
const strdecoded = atob(str); const strdecoded = atob(str);
const u8array = new Uint8Array(strdecoded.length); const u8array = new Uint8Array(strdecoded.length);
for (let j = 0; j < strdecoded.length; ++j) { for (let j = 0; j < strdecoded.length; ++j) {
@ -1053,6 +1059,13 @@ class RoaringBitmap {
contains(keyvalue) { contains(keyvalue) {
const key = keyvalue >> 16; const key = keyvalue >> 16;
const value = keyvalue & 0xFFFF; const value = keyvalue & 0xFFFF;
// Binary search algorithm copied from
// https://en.wikipedia.org/wiki/Binary_search#Procedure
//
// Format is required by specification to be sorted.
// Because keys are 16 bits and unique, length can't be
// bigger than 2**16, and because we have 32 bits of safe int,
// left + right can't overflow.
let left = 0; let left = 0;
let right = this.keys.length - 1; let right = this.keys.length - 1;
while (left <= right) { while (left <= right) {
@ -1076,6 +1089,11 @@ class RoaringBitmapRun {
this.array = array; this.array = array;
} }
contains(value) { contains(value) {
// Binary search algorithm copied from
// https://en.wikipedia.org/wiki/Binary_search#Procedure
//
// Since runcount is stored as 16 bits, left + right
// can't overflow.
let left = 0; let left = 0;
let right = this.runcount - 1; let right = this.runcount - 1;
while (left <= right) { while (left <= right) {
@ -1100,6 +1118,11 @@ class RoaringBitmapArray {
this.array = array; this.array = array;
} }
contains(value) { contains(value) {
// Binary search algorithm copied from
// https://en.wikipedia.org/wiki/Binary_search#Procedure
//
// Since cardinality can't be higher than 4096, left + right
// cannot overflow.
let left = 0; let left = 0;
let right = this.cardinality - 1; let right = this.cardinality - 1;
while (left <= right) { while (left <= right) {