+static const char key_afm_prefix[] = "X-AFM-";
+static const char key_http_port[] = "http-port";
+
+#define HTTP_PORT_MIN 31000
+#define HTTP_PORT_MAX 32759
+#define HTTP_PORT_IS_VALID(port) (HTTP_PORT_MIN <= (port) && (port) <= HTTP_PORT_MAX)
+#define HTTP_PORT_COUNT (HTTP_PORT_MAX - HTTP_PORT_MIN + 1)
+#define HTTP_PORT_ACNT ((HTTP_PORT_COUNT + 31) >> 5)
+#define HTTP_PORT_ASFT(port) (((port) - HTTP_PORT_MIN) & 31)
+#define HTTP_PORT_AIDX(port) (((port) - HTTP_PORT_MIN) >> 5)
+#define HTTP_PORT_TEST(array,port) ((((array)[HTTP_PORT_AIDX(port)]) >> HTTP_PORT_ASFT(port)) & 1)
+#define HTTP_PORT_SET(array,port) (((array)[HTTP_PORT_AIDX(port)]) |= (((uint32_t)1) << HTTP_PORT_ASFT(port)))
+
+static uint32_t *port_bits = NULL;
+
+/*
+ * 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 (HTTP_PORT_IS_VALID(p))
+ HTTP_PORT_SET((uint32_t*)closure, p);
+ }
+ }
+ iter = strstr(iter, key_afm_prefix);
+ }
+ free(content);
+ return 0;
+}
+
+static int update_portbits(uint32_t *portbits)
+{
+ int rc;
+
+ memset(portbits, 0, HTTP_PORT_ACNT * sizeof(uint32_t));
+ rc = systemd_unit_list(0, get_port_cb, portbits);
+ if (rc >= 0)
+ rc = systemd_unit_list(1, get_port_cb, portbits);
+ if (rc < 0)
+ ERROR("troubles while updating ports");
+ return rc;
+}
+
+static int first_free_port(uint32_t *portbits)
+{
+ int port;
+
+ port = HTTP_PORT_MIN;
+ while (port <= HTTP_PORT_MAX && !~portbits[HTTP_PORT_AIDX(port)])
+ port += 32;
+ while (port <= HTTP_PORT_MAX && HTTP_PORT_TEST(portbits, port))
+ port++;
+ if (port > HTTP_PORT_MAX) {
+ ERROR("Can't compute a valid port");
+ errno = EADDRNOTAVAIL;
+ port = -1;
+ }
+ return port;
+}
+
+static int get_port()
+{
+ int port;
+
+ /* ensure existing port bitmap */
+ if (port_bits == NULL) {
+ port_bits = malloc(HTTP_PORT_ACNT * sizeof(uint32_t));
+ if (port_bits == NULL || update_portbits(port_bits) < 0)
+ return -1;
+ }
+
+ /* allocates the port */
+ port = first_free_port(port_bits);
+ if (port >= 0)
+ HTTP_PORT_SET(port_bits, port);
+
+ return port;
+}
+