+static const char key_afm_prefix[] = "X-AFM-";
+static const char key_http_port[] = "http-port";
+
+/*
+ * normalize unit files: remove comments, remove heading blanks,
+ * make single lines
+ */
+static void normalize_unit_file(char *content)
+{
+ char *read, *write, c;
+
+ read = write = content;
+ c = *read++;
+ while (c) {
+ switch (c) {
+ case '\n':
+ case ' ':
+ case '\t':
+ c = *read++;
+ break;
+ case '#':
+ case ';':
+ do { c = *read++; } while(c && c != '\n');
+ break;
+ default:
+ *write++ = c;
+ do { *write++ = c = *read++; } while(c && c != '\n');
+ if (write - content >= 2 && write[-2] == '\\')
+ (--write)[-1] = ' ';
+ break;
+ }
+ }
+ *write = c;
+}
+
+static int get_port_cb(void *closure, const char *name, const char *path, int isuser)
+{
+ char *iter;
+ char *content;
+ size_t length;
+ int rc, p;
+
+ /* reads the file */
+ rc = getfile(path, &content, &length);
+ if (rc < 0)
+ return rc;
+
+ /* normalize the unit file */
+ normalize_unit_file(content);
+
+ /* process the file */
+ iter = strstr(content, key_afm_prefix);
+ while (iter) {
+ iter += sizeof key_afm_prefix - 1;
+ if (*iter == '-')
+ iter++;
+ if (!strncmp(iter, key_http_port, sizeof key_http_port - 1)) {
+ iter += sizeof key_http_port - 1;
+ while(*iter && *iter != '=' && *iter != '\n')
+ iter++;
+ if (*iter == '=') {
+ while(*++iter == ' ');
+ p = atoi(iter);
+ if (p >= 0 && p < 32768)
+ ((uint32_t*)closure)[p >> 5] |= (uint32_t)1 << (p & 31);
+ }
+ }
+ iter = strstr(iter, key_afm_prefix);
+ }
+ free(content);
+ return 0;
+}
+
+static int get_port()
+{
+ int rc;
+ uint32_t ports[1024]; /* 1024 * 32 = 32768 */
+
+ memset(ports, 0, sizeof ports);
+ rc = systemd_unit_list(0, get_port_cb, &ports);
+ if (rc >= 0) {
+ rc = systemd_unit_list(1, get_port_cb, ports);
+ if (rc >= 0) {
+ for (rc = 1024 ; rc < 32768 && !~ports[rc >> 5] ; rc += 32);
+ if (rc == 32768) {
+ ERROR("Can't compute a valid port");
+ errno = EADDRNOTAVAIL;
+ rc = -1;
+ } else {
+ while (1 & (ports[rc >> 5] >> (rc & 31))) rc++;
+ }
+ }
+ }
+ return rc;
+}
+