java-topology/defects/freeswitch/unit/FreeSWITCHTest.java

import java.util.*;

/**
 * CWE-407 simulation: FreeSWITCH switch_loadable_module_get_codecs_sorted
 * O(N²) codec preference deduplication.
 *
 * Defect: switch_loadable_module_get_codecs_sorted() iterates prefs[0..preflen)
 * and for each entry x, re-parses prefs[0..x-1] via switch_parse_codec_buf
 * to check for duplicates — O(N²) with N = number of codec preferences.
 *
 * This function is called on every SIP call setup (switch_core_media_prepare_codecs).
 * With N=SWITCH_MAX_CODECS=50 and high call volumes, this becomes a hot inner loop.
 *
 * Fix: pre-parse all prefs into a struct array in one O(N) pass, then check
 * against the pre-parsed array — eliminates redundant string parsing from O(N²)
 * to O(N) parsing + O(N²) comparison (but compare is just strcmp not full parse).
 */
public class FreeSWITCHTest {

    // Simulate a parsed codec preference entry (simplified)
    static class CodecPref {
        final String name;
        final int    interval;
        final int    rate;
        final int    channels;
        final String fmtp;

        CodecPref(String spec) {
            // Simulate switch_parse_codec_buf: "PCMU@20i@8000h" → name=PCMU, interval=20, rate=8000
            String[] parts = spec.split("@");
            this.name = parts[0];
            int iv = 0, r = 0, ch = 1;
            String fmt = "";
            for (int i = 1; i < parts.length; i++) {
                String p = parts[i];
                if (p.endsWith("i")) iv = Integer.parseInt(p.substring(0, p.length()-1));
                else if (p.endsWith("h")) r = Integer.parseInt(p.substring(0, p.length()-1));
                else if (p.endsWith("c")) ch = Integer.parseInt(p.substring(0, p.length()-1));
                else fmt = p;
            }
            this.interval = iv == 0 ? defaultPtime(name) : iv;
            this.rate     = r  == 0 ? defaultRate(name) : r;
            this.channels = ch;
            this.fmtp     = fmt;
        }

        static int defaultPtime(String name) { return 20; }
        static int defaultRate(String name) { return 8000; }

        boolean matches(CodecPref o) {
            return this.name.equalsIgnoreCase(o.name)
                && this.interval == o.interval
                && this.rate     == o.rate
                && this.channels == o.channels
                && this.fmtp.equalsIgnoreCase(o.fmtp);
        }
    }

    // --- Defect: re-parse each prefs[j] for every x (O(N²) parsing) ---
    static List<String> deduplicateDefect(String[] prefs) {
        List<String> result = new ArrayList<>();
        for (int x = 0; x < prefs.length; x++) {
            CodecPref cur = new CodecPref(prefs[x]);  // parse prefs[x]
            boolean dup = false;
            for (int j = 0; j < x; j++) {
                CodecPref prev = new CodecPref(prefs[j]);  // re-parse prefs[j] every time!
                if (cur.matches(prev)) { dup = true; break; }
            }
            if (!dup) result.add(prefs[x]);
        }
        return result;
    }

    // --- Fix: pre-parse all prefs once, then O(N²) compare only ---
    static List<String> deduplicateFix(String[] prefs) {
        // Pre-pass: parse once
        CodecPref[] parsed = new CodecPref[prefs.length];
        for (int i = 0; i < prefs.length; i++) {
            parsed[i] = new CodecPref(prefs[i]);
        }
        // Dedup using pre-parsed structs
        List<String> result = new ArrayList<>();
        outer:
        for (int x = 0; x < prefs.length; x++) {
            for (int j = 0; j < x; j++) {
                if (parsed[x].matches(parsed[j])) continue outer;
            }
            result.add(prefs[x]);
        }
        return result;
    }

    static String[] buildPrefs(int n, int dupRate) {
        // Build N codec prefs; dupRate% are duplicates
        String[] base = {"PCMU@20i@8000h", "PCMA@20i@8000h", "G729@20i@8000h",
                         "G722@20i@16000h", "OPUS@20i@48000h", "G723@30i@8000h",
                         "G726@20i@8000h", "GSM@20i@8000h", "ILBC@30i@8000h",
                         "G728@20i@8000h"};
        String[] prefs = new String[n];
        Random rng = new Random(42);
        for (int i = 0; i < n; i++) {
            if (i > 0 && rng.nextInt(100) < dupRate) {
                prefs[i] = prefs[rng.nextInt(i)];  // duplicate
            } else {
                prefs[i] = base[i % base.length] + (i >= base.length ? "@v" + i : "");
            }
        }
        return prefs;
    }

    static long timeDefect(String[] prefs, int iterations) {
        long start = System.nanoTime();
        for (int i = 0; i < iterations; i++) deduplicateDefect(prefs);
        return System.nanoTime() - start;
    }

    static long timeFix(String[] prefs, int iterations) {
        long start = System.nanoTime();
        for (int i = 0; i < iterations; i++) deduplicateFix(prefs);
        return System.nanoTime() - start;
    }

    public static void main(String[] args) {
        System.out.println("=== CWE-407: FreeSWITCH get_codecs_sorted O(N²) re-parse dedup ===");
        System.out.println();

        // --- Correctness: both produce same dedup result ---
        int N = 50;  // SWITCH_MAX_CODECS
        String[] prefs50 = buildPrefs(N, 20);
        List<String> defectResult = deduplicateDefect(prefs50);
        List<String> fixResult    = deduplicateFix(prefs50);
        assert defectResult.equals(fixResult)
            : "Dedup results differ: " + defectResult + " vs " + fixResult;
        System.out.printf("PASS: defect and fix produce identical dedup (%d → %d unique)%n",
                          N, defectResult.size());

        // --- Performance: warm up ---
        int ITER = 20_000;
        for (int w = 0; w < 3; w++) { timeDefect(prefs50, ITER); timeFix(prefs50, ITER); }

        long defectNs = timeDefect(prefs50, ITER);
        long fixNs    = timeFix(prefs50, ITER);
        double ratio  = (double) defectNs / fixNs;

        System.out.printf("Defect (re-parse O(N²)): %,d ns over %,d iterations%n", defectNs, ITER);
        System.out.printf("Fix    (pre-parse O(N)):  %,d ns over %,d iterations%n", fixNs, ITER);
        System.out.printf("Speedup ratio: %.1fx%n", ratio);
        System.out.println();

        // --- Complexity demo: varies N ---
        System.out.println("Complexity scaling (20% duplicates):");
        System.out.printf("  %-6s  %-14s  %-14s  %-8s%n", "N", "Defect(ns)", "Fix(ns)", "Ratio");
        for (int n : new int[]{5, 10, 20, 30, 50}) {
            String[] p = buildPrefs(n, 20);
            // warm
            for (int w = 0; w < 2; w++) { timeDefect(p, ITER); timeFix(p, ITER); }
            long d = timeDefect(p, ITER);
            long f = timeFix(p, ITER);
            System.out.printf("  %-6d  %-14d  %-14d  %-8.1f%n", n, d, f, (double) d / f);
        }

        assert ratio >= 1.5 : String.format("Expected speedup >= 1.5x, got %.1fx", ratio);
        System.out.println();
        System.out.println("PASS: all assertions satisfied");
    }
}