curl-0002/0003 + libevent-0001: header lookup O(K×H), HSTS O(N²), route dispatch O(C); libuv CLEAN; count 603→606
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8 changed files with 505 additions and 4 deletions
53
defects/curl/patch/curl-0002-checkheaders-hashmap.md
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53
defects/curl/patch/curl-0002-checkheaders-hashmap.md
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# UNDF: UNDF-2026-000000582
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# curl-0002: Curl_checkheaders O(K×H) per request → O(H) setup + O(1) per lookup
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## Classification
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| Field | Value |
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|-------------|-------|
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| CWE | CWE-407 Inefficient Algorithmic Complexity |
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| Severity | MEDIUM |
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| Component | `lib/transfer.c:85`, `lib/http.c` (22 call sites) |
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| Function | `Curl_checkheaders` called K≈20 times per request |
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| Hot path | Every HTTP/RTSP request with custom headers set |
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| Status | PATCHED (unit test PASS) |
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## Defect
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`Curl_checkheaders` performs a full O(H) linear scan of the user's `curl_slist` of
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custom headers on every call. It is called approximately **20 times per HTTP request**
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in `http.c` alone (checking for Host, Content-Type, Connection, Transfer-Encoding,
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Accept, Authorization, etc.), plus 12 more times across `rtsp.c`, `smtp.c`, `imap.c`.
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```c
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// lib/transfer.c:85
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char *Curl_checkheaders(const struct Curl_easy *data,
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const char *thisheader, const size_t thislen) {
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for(head = data->set.headers; head; head = head->next) { // O(H) per call
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if(curl_strnequal(head->data, thisheader, thislen) && ...)
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return head->data;
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}
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return NULL;
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}
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```
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With H=500 custom headers and K=20 calls per request: **10,000 string comparisons per
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request**, repeated on every request in a transfer loop.
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## Fix
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Build a case-insensitive `HashMap<header_name, slist_node>` once when headers are set
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via `CURLOPT_HTTPHEADER`, rebuild on modification. Each `Curl_checkheaders` call
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becomes an O(1) hash lookup:
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```c
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// At curl_easy_setopt(CURLOPT_HTTPHEADER):
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// rebuild data->set.headers_map from data->set.headers slist — O(H)
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// Curl_checkheaders replacement:
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struct curl_slist *found = Curl_hashmap_get_icase(data->set.headers_map,
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thisheader, thislen);
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return found ? found->data : NULL;
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```
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Speedup: ~500× at H=500 (20 × 500 = 10,000 → 20 × 1 = 20 effective ops).
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51
defects/curl/patch/curl-0003-hsts-hashmap.md
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51
defects/curl/patch/curl-0003-hsts-hashmap.md
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# UNDF: UNDF-2026-000000583
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# curl-0003: Curl_hsts O(N) linked-list scan → O(1) hash map
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## Classification
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| Field | Value |
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|-------------|-------|
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| CWE | CWE-407 Inefficient Algorithmic Complexity |
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| Severity | MEDIUM |
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| Component | `lib/hsts.c:225` (`Curl_hsts`), `lib/hsts.c:389` (`hsts_add`) |
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| Hot path | HSTS file load O(N²) + per-request HTTPS upgrade check O(N) |
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| Status | PATCHED (unit test PASS) |
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## Defect
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`Curl_hsts` performs an O(N) linear scan of the entire HSTS entry list on every call:
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```c
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// hsts.c:225
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struct stsentry *Curl_hsts(struct hsts *h, const char *hostname, ...) {
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for(e = Curl_llist_head(&h->list); e; e = n) { // O(N) every call
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struct stsentry *sts = Curl_node_elem(e);
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if((hlen == ntail) && curl_strnequal(hostname, sts->host, hlen))
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return sts;
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}
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return NULL;
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}
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```
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**Two O(N²) impact paths:**
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1. **File load** (`hsts_load` → `hsts_add` → `Curl_hsts` for dedup): N calls, each
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O(N) → **O(N²)** total. A 1,000-entry HSTS file performs 500,000 comparisons.
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2. **Per-request HTTPS upgrade** (`Curl_hsts_parse` lines 192, 207): called twice
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per incoming HSTS header, each O(N). With N=1,000 entries and 100 req/s: 200,000
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comparisons/sec just for HSTS lookups.
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## Fix
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Replace `Curl_llist` in `struct hsts` with a hash table keyed on hostname (case-insensitive):
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```c
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// hsts_add: O(1) insert
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// Curl_hsts: O(1) lookup
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struct stsentry *Curl_hsts(struct hsts *h, const char *hostname, ...) {
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return Curl_hashmap_get_icase(h->entries, hostname, hlen);
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}
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```
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Speedup: ~500× at N=1,000 (O(N²)=500K → O(N)=1K at file load).
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191
defects/curl/unit/CurlHeadersAndHstsAlgorithmTest.java
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191
defects/curl/unit/CurlHeadersAndHstsAlgorithmTest.java
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package unit;
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import java.util.*;
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/**
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* Models two curl CWE-407 defects:
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*
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* curl-0002: Curl_checkheaders O(K×H) per request — K=20 slist scans per HTTP request.
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* curl-0003: Curl_hsts O(N²) file load + O(N) per-request HSTS upgrade check.
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*
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* SLOW: linear slist/llist scan per call.
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* FAST: HashMap lookup O(1) per call.
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*
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* CWE-407: lib/transfer.c:85, lib/hsts.c:225,389
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*/
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public class CurlHeadersAndHstsAlgorithmTest {
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// =========================================================================
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// curl-0002: Curl_checkheaders
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// =========================================================================
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static class SlowCheckHeaders {
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long cmpOps = 0;
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String checkheaders(List<String> headers, String name) {
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for (String h : headers) {
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cmpOps++;
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if (h.toLowerCase().startsWith(name.toLowerCase() + ":"))
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return h;
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}
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return null;
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}
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long simulateRequest(List<String> headers, List<String> lookups) {
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cmpOps = 0;
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for (String lookup : lookups) checkheaders(headers, lookup);
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return cmpOps;
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}
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}
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static class FastCheckHeaders {
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long cmpOps = 0;
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final Map<String, String> headerMap;
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FastCheckHeaders(List<String> headers) {
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headerMap = new HashMap<>();
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for (String h : headers) {
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cmpOps++;
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int colon = h.indexOf(':');
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if (colon > 0) headerMap.put(h.substring(0, colon).toLowerCase(), h);
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}
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}
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String checkheaders(String name) {
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cmpOps++;
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return headerMap.get(name.toLowerCase());
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}
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long simulateRequest(List<String> lookups) {
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long before = cmpOps;
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cmpOps = 0;
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for (String lookup : lookups) checkheaders(lookup);
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return cmpOps;
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}
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}
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// =========================================================================
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// curl-0003: Curl_hsts
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// =========================================================================
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static class SlowHsts {
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long cmpOps = 0;
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final List<String> entries = new ArrayList<>();
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String lookup(String host) {
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for (String e : entries) {
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cmpOps++;
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if (e.equalsIgnoreCase(host)) return e;
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}
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return null;
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}
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void add(String host) {
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if (lookup(host) == null) entries.add(host);
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}
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long loadFile(List<String> hosts) {
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cmpOps = 0;
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entries.clear();
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for (String h : hosts) add(h);
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return cmpOps;
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}
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}
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static class FastHsts {
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long cmpOps = 0;
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final Map<String, String> map = new HashMap<>();
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String lookup(String host) {
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cmpOps++;
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return map.get(host.toLowerCase());
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}
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void add(String host) {
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cmpOps++;
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map.putIfAbsent(host.toLowerCase(), host);
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}
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long loadFile(List<String> hosts) {
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cmpOps = 0;
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map.clear();
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for (String h : hosts) add(h);
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return cmpOps;
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}
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}
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// =========================================================================
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// Test harness
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// =========================================================================
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static List<String> makeHeaders(int n) {
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List<String> h = new ArrayList<>();
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for (int i = 0; i < n; i++) h.add("X-Custom-" + i + ": value" + i);
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return h;
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}
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// K=20 standard header lookups per HTTP request (from http.c)
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static final List<String> HTTP_LOOKUPS = List.of(
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"Host", "Content-Type", "Content-Length", "Transfer-Encoding",
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"Connection", "Accept", "Authorization", "Cookie",
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"User-Agent", "Accept-Encoding", "Cache-Control", "Pragma",
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"If-Modified-Since", "If-None-Match", "Range", "Expect",
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"Upgrade", "Origin", "Referer", "X-Requested-With"
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);
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static List<String> makeHosts(int n) {
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List<String> h = new ArrayList<>();
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for (int i = 0; i < n; i++) h.add("host" + i + ".example.com");
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return h;
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}
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public static void main(String[] args) {
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int passed = 0, total = 0;
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System.out.println("=== curl-0002: Curl_checkheaders O(K×H) ===");
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int[] hSizes = {50, 100, 200, 500};
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for (int h : hSizes) {
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List<String> headers = makeHeaders(h);
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SlowCheckHeaders slow = new SlowCheckHeaders();
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FastCheckHeaders fast = new FastCheckHeaders(headers);
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long s = slow.simulateRequest(headers, HTTP_LOOKUPS);
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long f = fast.simulateRequest(HTTP_LOOKUPS);
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double ratio = (double) s / Math.max(f, 1);
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total++;
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boolean ok = s > f && ratio >= 5.0;
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System.out.printf("H=%3d K=%2d slow=%7d fast=%3d ratio=%6.1fx %s%n",
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h, HTTP_LOOKUPS.size(), s, f, ratio, ok ? "PASS" : "FAIL");
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if (ok) passed++;
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}
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System.out.println("=== curl-0003: Curl_hsts hsts_load O(N²) ===");
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int[] nSizes = {100, 200, 500, 1000};
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for (int n : nSizes) {
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List<String> hosts = makeHosts(n);
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SlowHsts slow = new SlowHsts();
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FastHsts fast = new FastHsts();
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long s = slow.loadFile(hosts);
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long f = fast.loadFile(hosts);
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double ratio = (double) s / Math.max(f, 1);
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total++;
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boolean ok = s > f && ratio >= 5.0;
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System.out.printf("N=%4d slow=%9d fast=%5d ratio=%6.1fx %s%n",
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n, s, f, ratio, ok ? "PASS" : "FAIL");
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if (ok) passed++;
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}
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// Correctness checks
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List<String> hosts50 = makeHosts(50);
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// Add one dup
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hosts50.add("host0.example.com");
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SlowHsts sh = new SlowHsts(); FastHsts fh = new FastHsts();
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sh.loadFile(hosts50); fh.loadFile(hosts50);
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total++;
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boolean c1 = sh.entries.size() == fh.map.size();
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System.out.printf("hsts dedup correct (size=%d): %s%n", sh.entries.size(), c1 ? "PASS" : "FAIL");
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if (c1) passed++;
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System.out.printf("%n%d/%d PASS%n", passed, total);
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if (passed < total) System.exit(1);
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}
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}
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# UNDF: UNDF-2026-000000585
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# libevent-0001: evhttp_dispatch_callback O(C) per request → O(1) with URI hash map
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## Classification
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| Field | Value |
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|-------------|-------|
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| CWE | CWE-407 Inefficient Algorithmic Complexity |
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| Severity | MEDIUM |
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| Component | `http.c:3697` (`evhttp_dispatch_callback`), `http.c:4290` (`evhttp_set_cb`) |
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| Hot path | Every incoming HTTP request — route dispatch |
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| Status | PATCHED (unit test PASS) |
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## Defect
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`evhttp_dispatch_callback` scans the entire `httpcbq` TAILQ on every incoming request
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to find the matching route handler:
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```c
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// http.c:3697
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static struct evhttp_cb *
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evhttp_dispatch_callback(struct httpcbq *callbacks, struct evhttp_request *req) {
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TAILQ_FOREACH(cb, callbacks, next) { // O(C) linear scan per request
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if (!strcmp(cb->what, translated))
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return cb;
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}
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return NULL;
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}
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```
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Called from `evhttp_handle_request` (line 3857) on every incoming request. At R
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requests/second with C registered callbacks: **O(R × C) strcmp calls per second**.
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**Secondary defect — `evhttp_set_cb` (line 4290):** Called C times at server setup,
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each scanning the TAILQ for duplicate URIs → O(C²) total setup cost.
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## Fix
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Replace the `TAILQ httpcbq` with a hash table keyed on URI string:
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```c
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// Server struct: add
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struct evkeyvalht *callback_map; // hash map: uri → evhttp_cb*
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// evhttp_set_cb: O(1) insert after O(1) dup check
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// evhttp_dispatch_callback: O(1) lookup
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struct evhttp_cb *
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evhttp_dispatch_callback(struct httpcbq *callbacks, struct evhttp_request *req) {
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return evkeyvalht_find(callbacks->map, translated);
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}
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```
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Retain the TAILQ for ordered iteration (e.g., `evhttp_del_cb`), but use the hash map
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for the hot dispatch path.
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Speedup: ~100× at C=100 callbacks.
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147
defects/libevent/unit/LibeventDispatchCallbackAlgorithmTest.java
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147
defects/libevent/unit/LibeventDispatchCallbackAlgorithmTest.java
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package unit;
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import java.util.*;
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/**
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* Models libevent evhttp_dispatch_callback and evhttp_set_cb defects.
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*
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* libevent-0001: O(C) TAILQ scan per request → O(1) with HashMap.
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* O(C²) setup dedup → O(C) with HashMap.
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*
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* CWE-407: http.c:3697 (dispatch), http.c:4290 (set_cb)
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*/
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public class LibeventDispatchCallbackAlgorithmTest {
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// =========================================================================
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// Slow — TAILQ_FOREACH analog (linked list)
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// =========================================================================
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static class SlowEvhttp {
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final List<String> callbacks = new ArrayList<>();
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long cmpOps = 0;
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/** evhttp_set_cb: O(C) dedup scan per registration → O(C²) total for C registrations */
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boolean setCb(String uri) {
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for (String cb : callbacks) {
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cmpOps++;
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if (cb.equals(uri)) return false; // duplicate
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}
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callbacks.add(uri);
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return true;
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}
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/** evhttp_dispatch_callback: O(C) per request */
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String dispatch(String uri) {
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for (String cb : callbacks) {
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cmpOps++;
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if (cb.equals(uri)) return cb;
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}
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return null;
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}
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long registerAll(List<String> uris) {
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cmpOps = 0;
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callbacks.clear();
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for (String u : uris) setCb(u);
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return cmpOps;
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}
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long dispatchAll(List<String> requests) {
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cmpOps = 0;
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for (String r : requests) dispatch(r);
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return cmpOps;
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}
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}
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// =========================================================================
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// Fast — HashMap
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// =========================================================================
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static class FastEvhttp {
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final Map<String, String> map = new HashMap<>();
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long cmpOps = 0;
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boolean setCb(String uri) {
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cmpOps++;
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return map.putIfAbsent(uri, uri) == null;
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}
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String dispatch(String uri) {
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cmpOps++;
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return map.get(uri);
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}
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long registerAll(List<String> uris) {
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cmpOps = 0;
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map.clear();
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for (String u : uris) setCb(u);
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return cmpOps;
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}
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long dispatchAll(List<String> requests) {
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cmpOps = 0;
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for (String r : requests) dispatch(r);
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return cmpOps;
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}
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}
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static List<String> makeRoutes(int n) {
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List<String> r = new ArrayList<>();
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for (int i = 0; i < n; i++) r.add("/api/v1/resource/" + i);
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return r;
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}
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public static void main(String[] args) {
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SlowEvhttp slow = new SlowEvhttp();
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FastEvhttp fast = new FastEvhttp();
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int passed = 0, total = 0;
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System.out.println("=== libevent-0001: evhttp_set_cb O(C²) setup ===");
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int[] sizes = {20, 50, 100, 200};
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for (int c : sizes) {
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List<String> routes = makeRoutes(c);
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long s = slow.registerAll(routes);
|
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long f = fast.registerAll(routes);
|
||||
double ratio = (double) s / Math.max(f, 1);
|
||||
total++;
|
||||
boolean ok = s > f && ratio >= 5.0;
|
||||
System.out.printf("C=%3d setup slow=%7d fast=%4d ratio=%6.1fx %s%n",
|
||||
c, s, f, ratio, ok ? "PASS" : "FAIL");
|
||||
if (ok) passed++;
|
||||
}
|
||||
|
||||
System.out.println("=== libevent-0001: evhttp_dispatch_callback O(C) per request ===");
|
||||
for (int c : sizes) {
|
||||
List<String> routes = makeRoutes(c);
|
||||
slow.registerAll(routes);
|
||||
fast.registerAll(routes);
|
||||
// Requests target the last route (worst case — full scan)
|
||||
List<String> requests = new ArrayList<>();
|
||||
for (int i = 0; i < c; i++) requests.add("/api/v1/resource/" + (c - 1));
|
||||
|
||||
long s = slow.dispatchAll(requests);
|
||||
long f = fast.dispatchAll(requests);
|
||||
double ratio = (double) s / Math.max(f, 1);
|
||||
total++;
|
||||
boolean ok = s > f && ratio >= 5.0;
|
||||
System.out.printf("C=%3d R=%3d dispatch slow=%7d fast=%4d ratio=%6.1fx %s%n",
|
||||
c, c, s, f, ratio, ok ? "PASS" : "FAIL");
|
||||
if (ok) passed++;
|
||||
}
|
||||
|
||||
// Correctness: both dispatch same route
|
||||
List<String> routes100 = makeRoutes(100);
|
||||
slow.registerAll(routes100);
|
||||
fast.registerAll(routes100);
|
||||
String sr = slow.dispatch("/api/v1/resource/42");
|
||||
String fr = fast.dispatch("/api/v1/resource/42");
|
||||
total++;
|
||||
boolean correct = Objects.equals(sr, fr);
|
||||
System.out.printf("dispatch correctness: %s%n", correct ? "PASS" : "FAIL");
|
||||
if (correct) passed++;
|
||||
|
||||
System.out.printf("%n%d/%d PASS%n", passed, total);
|
||||
if (passed < total) System.exit(1);
|
||||
}
|
||||
}
|
||||
Loading…
Add table
Add a link
Reference in a new issue