Lot of changes here.

1. check_classic_mac_basic.yml — update to latest macOS-latest
2. docker-on-push-tag-or-pr — dependant updates
3. FFTConvolver — fix a compilation warning when the DEBUG flag is turned off
4. Reorganise some source files — e.g. move most of the metadata stuff into a subdirectory
5. Remove unused special-purpose AirPlay 2 RC event handler.
6. Reorganise source files and source code relating to the standard event handler.
7. Check configuration settings a little more carefully to offer more meaningful diagnostics.
8. Add password to AirPlay 2 and reorganise initialisation to set AirPlay 2 flags accordingly.  Also, remove redundant airplay_pin.
9. Remove redundant debug facility definitions from common.h
10. Make it possible to omit all the dacp stuff from a build.
11. Make it possible to omit metadata multicast from a build.
12. Add AP2-native metadata by setting bit 50 of features to true.
13. Improve stability when pre-empting an existing play session.
14. Fix a few compiler warnings in the pair_ap library.
15. Ensure that the audio format is known before starting synchronisation.
16. Improve handle_configure to set/clear a new config setting. Doesn’t seem to do anything…
17. Experimentally turn off bit 46 of AirPlay 2 features — seems to stop failing pair-verify attempts.

utilities/debug.c

@@ -23,6 +23,7 @@ SOFTWARE.
 */
 
 #include "debug.h"
+#include <ctype.h> // for isprint()
 #include <inttypes.h>
 #include <pthread.h>
 #include <stdarg.h>
@@ -64,13 +65,9 @@ void debug_init(int level, int show_elapsed_time, int show_relative_time, int sh
   debugger_show_file_and_line = show_file_and_line;
 }
 
-int debug_level() {
-  return debuglev;
-};
+int debug_level() { return debuglev; };
 
-void set_debug_level(int level) {
-  debuglev = level;
-}
+void set_debug_level(int level) { debuglev = level; }
 
 void increase_debug_level() {
   if (debuglev < 3)
@@ -82,28 +79,15 @@ void decrease_debug_level() {
     debuglev--;
 }
 
-int get_show_elapsed_time() {
-  return debugger_show_elapsed_time;
-  
-}
-void set_show_elapsed_time(int setting) {
-  debugger_show_elapsed_time = setting;
-}
-int get_show_relative_timel() {
-  return debugger_show_relative_time;
-}
+int get_show_elapsed_time() { return debugger_show_elapsed_time; }
+void set_show_elapsed_time(int setting) { debugger_show_elapsed_time = setting; }
+int get_show_relative_timel() { return debugger_show_relative_time; }
 
-void set_show_relative_time(int setting) {
-  debugger_show_relative_time = setting;
-}
+void set_show_relative_time(int setting) { debugger_show_relative_time = setting; }
 
-int get_show_file_and_line() {
-  return debugger_show_file_and_line;
-}
+int get_show_file_and_line() { return debugger_show_file_and_line; }
 
-void set_show_file_and_line(int setting) {
-  debugger_show_file_and_line = setting;
-}
+void set_show_file_and_line(int setting) { debugger_show_file_and_line = setting; }
 
 char *generate_preliminary_string(char *buffer, size_t buffer_length, double tss, double tsl,
                                   const char *filename, const int linenumber, const char *prefix) {
@@ -244,10 +228,94 @@ void _inform(const char *filename, const int linenumber, const char *format, ...
   pthread_setcancelstate(oldState, NULL);
 }
 
+
+void _debug_print_buffer(const char *thefilename, const int linenumber, int level, void *ibuf,
+                         size_t buf_len) {
+
+  if (level > debuglev)
+    return;
+
+  char *vbuf = (char *)ibuf; // this to stop the compiler complaining about indexing through a void
+  unsigned int i;
+  unsigned int hexdump_cols = 16;
+  
+  // 0x123456: <hexdump_cols * 3> <hexdump_cols>\n
+  const size_t buffer_size = 2 + 6 + 2 + hexdump_cols * 3 + hexdump_cols + 1; 
+  char *buf = malloc(buffer_size);
+  if (buf) {
+    //char *bufp = buf;
+    // *buf = '\0';
+
+  // if (msg)
+  //   printf("%s", msg);
+  
+  #define ADDR_PREFIX_LEN 10  // "0x000000: "
+
+  // each complete row
+  for (i = 0; i < (buf_len / hexdump_cols); i++) {
+    char *bufp = buf;
+    *buf = '\0';
+    snprintf(bufp, ADDR_PREFIX_LEN + 1,"0x%06x  ", (i * hexdump_cols) & 0xFFFFFF);
+    bufp += ADDR_PREFIX_LEN;
+    
+    unsigned int j;
+    for (j = 0; j < hexdump_cols; j++) {
+      snprintf(bufp, strlen("12 ") + 1, "%02x ", 0xFF & vbuf[i * hexdump_cols + j]);
+      bufp += strlen("12 ");
+    }
+    
+    for (j = 0; j < hexdump_cols; j++) {
+      if (isprint(vbuf[i * hexdump_cols + j])) {
+          *bufp = 0xFF & vbuf[i * hexdump_cols + j];
+      } else {
+          *bufp = '.';
+      }
+      bufp++;
+    }
+    *bufp = '\0';
+      _debug(thefilename, linenumber, level, "%s", buf);
+  }
+
+  size_t remaining = buf_len % hexdump_cols;
+  if (remaining != 0) {
+    size_t starting_offset = buf_len - remaining;
+    char *bufp = buf;
+    *buf = '\0';
+    snprintf(bufp, ADDR_PREFIX_LEN + 1,"0x%06zx  ", starting_offset & 0xFFFFFF);
+    bufp += ADDR_PREFIX_LEN;
+
+    unsigned int j;
+    for (j = 0; j < hexdump_cols; j++) {
+      if (j < remaining) {
+        snprintf(bufp, strlen("12 ") + 1, "%02x ", 0xFF & vbuf[starting_offset + j]);
+      } else {
+        snprintf(bufp, strlen("   ") + 1, "   "); // fille with blanks
+      }
+      bufp += strlen("12 ");
+    }
+    
+    for (j = 0; j < remaining; j++) {
+      if (isprint(vbuf[i * hexdump_cols + j])) {
+          *bufp = 0xFF & vbuf[starting_offset + j];
+      } else {
+          *bufp = '.';
+      }
+      bufp++;
+    }
+    *bufp = '\0';
+      _debug(thefilename, linenumber, level, "%s", buf);
+  }
+  free(buf);
+  }
+}
+
+
+/*
 void _debug_print_buffer(const char *thefilename, const int linenumber, int level, void *vbuf,
                          size_t buf_len) {
   if (level > debuglev)
     return;
+  new_debug_print_buffer(thefilename, linenumber, level, vbuf, buf_len);
   char *buf = (char *)vbuf;
   char *obf =
       malloc(buf_len * 4 + 1); // to be on the safe side -- 4 characters on average for each byte
@@ -274,4 +342,5 @@ void _debug_print_buffer(const char *thefilename, const int linenumber, int leve
     _debug(thefilename, linenumber, level, "%s", obf);
     free(obf);
   }
-}
+}
+*/