Re: [nmap-svn] r36095 - nmap

[Daniel Miller <bonsaiviking () gmail com>]

Tudor,

Can you explain this to me? The commit message was very terse and does not
offer any information about what has changed. I see that you changed from
using std::lower_bound to std::set::find, which in the case of std::set
means improving from linear to logarithmic time. In order to do this, you
use a comparison object, HssPredicate, to trick the find() function into
finding the element with a specific sockaddr value without instantiating a
whole HostScanStats object. Because of using the set's find method, you
can't pass a new comparison object to each call like you could with
std::lower_bound, so you use a static member of the comparison object's
class. This works for us because Nmap is not multithreaded.

Does that about cover it? Or am I missing something?

Dan



On Wed, Aug 10, 2016 at 10:39 AM, <commit-mailer () nmap org> wrote:

> Author: tudor
> Date: Wed Aug 10 08:39:19 2016
> New Revision: 36095
>
> Log:
> UltraScanInfo::findHost is now faster
>
> Modified:
>    nmap/scan_engine.cc
>    nmap/scan_engine.h
>
> Modified: nmap/scan_engine.cc
> ============================================================
> ==================
> --- nmap/scan_engine.cc (original)
> +++ nmap/scan_engine.cc Wed Aug 10 08:39:19 2016
> @@ -154,15 +154,12 @@
>
>
>  int HssPredicate::operator() (HostScanStats *lhs, HostScanStats *rhs) {
> -  return 0 > sockaddr_storage_cmp(lhs->target->TargetSockAddr(),
> rhs->target->TargetSockAddr());
> -}
> -
> -int SockAddrPredicate::operator() (HostScanStats *lhs, HostScanStats
> *rhs) {
>    const struct sockaddr_storage *lss, *rss;
>    lss = (lhs) ? lhs->target->TargetSockAddr() : ss;
>    rss = (rhs) ? rhs->target->TargetSockAddr() : ss;
>    return 0 > sockaddr_storage_cmp(lss, rss);
>  }
> +struct sockaddr_storage *HssPredicate::ss = NULL;
>
>  void UltraScanInfo::log_overall_rates(int logt) {
>    log_write(logt, "Overall sending rates: %.2f packets / s",
> send_rate_meter.getOverallPacketRate(&now));
> @@ -1139,17 +1136,17 @@
>  HostScanStats *UltraScanInfo::findHost(struct sockaddr_storage *ss) {
>    std::set<HostScanStats *>::iterator hss;
>
> -  SockAddrPredicate p(ss);
> +  HssPredicate::ss = ss;
>    HostScanStats *fakeHss = NULL;
>
> -  hss = std::lower_bound(incompleteHosts.begin(), incompleteHosts.end(),
> fakeHss, p);
> +  hss = incompleteHosts.find(fakeHss);
>    if (hss != incompleteHosts.end()) {
>      if (o.debugging > 2)
>        log_write(LOG_STDOUT, "Found %s in incomplete hosts list.\n",
> (*hss)->target->targetipstr());
>      return *hss;
>    }
>
> -  hss = std::lower_bound(completedHosts.begin(), completedHosts.end(),
> fakeHss, p);
> +  hss = completedHosts.find(fakeHss);
>    if (hss != completedHosts.end()) {
>      if (o.debugging > 2)
>        log_write(LOG_STDOUT, "Found %s in completed hosts list.\n",
> (*hss)->target->targetipstr());
>
> Modified: nmap/scan_engine.h
> ============================================================
> ==================
> --- nmap/scan_engine.h  (original)
> +++ nmap/scan_engine.h  Wed Aug 10 08:39:19 2016
> @@ -654,15 +654,7 @@
>  struct HssPredicate {
>  public:
>    int operator() (HostScanStats *lhs, HostScanStats *rhs);
> -};
> -
> -struct SockAddrPredicate {
> -public:
> -  SockAddrPredicate(struct sockaddr_storage *ss) {
> -    this->ss = ss;
> -  }
> -  int operator() (HostScanStats *lhs, HostScanStats *rhs);
> -  struct sockaddr_storage *ss;
> +  static struct sockaddr_storage *ss;
>  };
>
>  class UltraScanInfo {
>
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