Add getPeerName; wraps getpeername + getnameinfo from C std library

Author: d-torrance

Diff for: M2/Macaulay2/d/actors2.dd

@@ -4,6 +4,8 @@ use evaluate;
 use struct;
 use sets;
 
+header "#include <netdb.h>"; -- for NI_MAXHOST and NI_MAXSERV
+
 dbmfirst(e:Expr):Expr := (
      when e
      is f:Database do dbmfirst(f)
@@ -510,6 +512,19 @@ isListener(e:Expr):Expr := (
      is f:file do toExpr(f.listener)
      else False);
 setupfun("isListener",isListener);
+getPeerName(e:Expr):Expr := (
+    when e
+    is f:file do (
+	if f.input then (
+	    host := new string len Ccode(int, "NI_MAXHOST") do provide ' ';
+	    serv := new string len Ccode(int, "NI_MAXSERV") do provide ' ';
+	    r := getpeername(f.infd, host, serv);
+	    if r < 0 then buildErrorPacket(
+		"can't get peer name: " + netstrerror(r))
+	    else seq(toExpr(host), toExpr(serv)))
+	else WrongArg("an input file"))
+    else WrongArg("a file"));
+setupfun("getPeerName", getPeerName);
 
 header "
     #if WITH_MYSQL

Diff for: M2/Macaulay2/d/scclib.c

@@ -781,6 +781,28 @@ int system_openlistener(M2_string interface0,M2_string serv) {
      return sd;
      }
 
+int system_getpeername(int sockfd, M2_string host, M2_string serv) {
+  struct sockaddr addr;
+  socklen_t addrlen;
+  int r;
+  char hostbuf[NI_MAXHOST], servbuf[NI_MAXSERV];
+
+  addrlen = sizeof addr;
+  r = getpeername(sockfd, &addr, &addrlen);
+  if (r == ERROR)
+    return ERROR;
+
+  r = getnameinfo(&addr, addrlen, hostbuf, sizeof hostbuf,
+		  servbuf, sizeof servbuf, 0);
+  if (r != 0)
+    return r + ERROR; /* see note above system_netstrerror */
+
+  strncpy(host->array, hostbuf, host->len);
+  strncpy(serv->array, servbuf, serv->len);
+
+  return 0;
+}
+
 int system_errno(void) {
   return 
 #ifdef HAVE_HERROR

Diff for: M2/Macaulay2/d/system.d

@@ -108,6 +108,7 @@ import openlistener(interface:string,serv:string):int;
 import netstrerror(errcode:int):string;
 import acceptBlocking(sd:int):int;
 import acceptNonblocking(sd:int):int;
+import getpeername(sockd:int,host:string,serv:string):int;
 import syserrmsg():string;				    -- uses errno
 import atend(f:function():void):void;
 import run(command:string):int;

Diff for: M2/Macaulay2/m2/exports.m2

@@ -731,6 +731,7 @@ export {
 	"getIOThreadMode",
 	"getNetFile",
 	"getNonUnit",
+	"getPeerName",
 	"getPrimeWithRootOfUnity",
 	"getSymbol",
 	"getWWW",