AP_Logger: remove twin paths for writing FMT messages

This stops us tracking formats-written in two places.

The Write() method will now emit formats as required and set the relevant bit in the backend-owned bitmask of formats sent.

libraries/AP_Logger/AP_Logger.cpp

@@ -614,16 +614,6 @@ void AP_Logger::Write_MessageF(const char *fmt, ...)
 void AP_Logger::backend_starting_new_log(const AP_Logger_Backend *backend)
 {
     _log_start_count++;
-
-    for (uint8_t i=0; i<_next_backend; i++) {
-        if (backends[i] == backend) { // pointer comparison!
-            // reset sent masks
-            for (struct log_write_fmt *f = log_write_fmts; f; f=f->next) {
-                f->sent_mask &= ~(1<<i);
-            }
-            break;
-        }
-    }
 }
 
 bool AP_Logger::should_log(const uint32_t mask) const
@@ -950,12 +940,7 @@ void AP_Logger::Write_NamedValueFloat(const char *name, float value)
 void AP_Logger::Safe_Write_Emit_FMT(log_write_fmt *f)
 {
     for (uint8_t i=0; i<_next_backend; i++) {
-        if (!(f->sent_mask & (1U<<i))) {
-            if (!backends[i]->Write_Emit_FMT(f->msg_type)) {
-                continue;
-            }
-            f->sent_mask |= (1U<<i);
-        }
+        backends[i]->Safe_Write_Emit_FMT(f->msg_type);
     }
 }
 
@@ -1041,12 +1026,6 @@ void AP_Logger::WriteV(const char *name, const char *labels, const char *units,
     }
 
     for (uint8_t i=0; i<_next_backend; i++) {
-        if (!(f->sent_mask & (1U<<i))) {
-            if (!backends[i]->Write_Emit_FMT(f->msg_type)) {
-                continue;
-            }
-            f->sent_mask |= (1U<<i);
-        }
         va_list arg_copy;
         va_copy(arg_copy, arg_list);
         backends[i]->Write(f->msg_type, arg_copy, is_critical, is_streaming);
@@ -1313,8 +1292,15 @@ int16_t AP_Logger::find_free_msg_type() const
  * It is assumed that logstruct's char* variables are valid strings of
  * maximum lengths for those fields (given in LogStructure.h e.g. LS_NAME_SIZE)
  */
-bool AP_Logger::fill_log_write_logstructure(struct LogStructure &logstruct, const uint8_t msg_type) const
+bool AP_Logger::fill_logstructure(struct LogStructure &logstruct, const uint8_t msg_type) const
 {
+    // check the static lists first...
+    const LogStructure *found = structure_for_msg_type(msg_type);
+    if (found != nullptr) {
+        logstruct = *found;
+        return true;
+    }
+
     // find log structure information corresponding to msg_type:
     struct log_write_fmt *f;
     for (f = log_write_fmts; f; f=f->next) {

libraries/AP_Logger/AP_Logger.h

@@ -382,7 +382,6 @@ public:
         struct log_write_fmt *next;
         uint8_t msg_type;
         uint8_t msg_len;
-        uint8_t sent_mask; // bitmask of backends sent to
         const char *name;
         const char *fmt;
         const char *labels;
@@ -452,7 +451,7 @@ private:
     int16_t find_free_msg_type() const;
 
     // fill LogStructure with information about msg_type
-    bool fill_log_write_logstructure(struct LogStructure &logstruct, const uint8_t msg_type) const;
+    bool fill_logstructure(struct LogStructure &logstruct, const uint8_t msg_type) const;
 
     bool _armed;
 

libraries/AP_Logger/AP_Logger_Backend.cpp

@@ -145,6 +145,15 @@ void AP_Logger_Backend::WriteMoreStartupMessages()
  */
 
 
+// output a FMT message if not already done so
+void AP_Logger_Backend::Safe_Write_Emit_FMT(uint8_t msg_type)
+{
+    if (have_emitted_format_for_type(LogMessages(msg_type))) {
+        return;
+    }
+    Write_Emit_FMT(msg_type);
+}
+
 bool AP_Logger_Backend::Write_Emit_FMT(uint8_t msg_type)
 {
 #if APM_BUILD_TYPE(APM_BUILD_Replay)
@@ -166,7 +175,7 @@ bool AP_Logger_Backend::Write_Emit_FMT(uint8_t msg_type)
         ls.units,
         ls.multipliers
     };
-    if (!_front.fill_log_write_logstructure(logstruct, msg_type)) {
+    if (!_front.fill_logstructure(logstruct, msg_type)) {
         // this is a bug; we've been asked to write out the FMT
         // message for a msg_type, but the frontend can't supply the
         // required information
@@ -393,28 +402,6 @@ void AP_Logger_Backend::validate_WritePrioritisedBlock(const void *pBuffer,
 }
 #endif
 
-bool AP_Logger_Backend::emit_format_for_type(LogMessages a_type)
-{
-    // linearly scan the formats structure to find the format for the type:
-    for (uint8_t i=0; i< num_types(); i++) {
-        const auto &s { structure(i) };
-        if (s == nullptr) {
-            continue;
-        }
-        if (s->msg_type != a_type) {
-            continue;
-        }
-        // found the relevant structure.  Attempt to write it:
-        if (!Write_Format(s)) {
-            return false;
-        }
-        return true;
-    }
-    // didn't find the structure.  That's probably bad...
-    INTERNAL_ERROR(AP_InternalError::error_t::flow_of_control);
-    return false;
-}
-
 bool AP_Logger_Backend::ensure_format_emitted(const void *pBuffer, uint16_t size)
 {
 #if APM_BUILD_TYPE(APM_BUILD_Replay)
@@ -437,11 +424,11 @@ bool AP_Logger_Backend::ensure_format_emitted(const void *pBuffer, uint16_t size
         return true;
     }
     if (!have_emitted_format_for_type(LOG_FORMAT_MSG) &&
-        !emit_format_for_type(LOG_FORMAT_MSG)) {
+        !Write_Emit_FMT(LOG_FORMAT_MSG)) {
         return false;
     }
 
-    return emit_format_for_type(type);
+    return Write_Emit_FMT(type);
 }
 
 bool AP_Logger_Backend::WritePrioritisedBlock(const void *pBuffer, uint16_t size, bool is_critical, bool writev_streaming)

libraries/AP_Logger/AP_Logger_Backend.h

@@ -159,6 +159,9 @@ public:
     // Returns true if the FMT message has ever been written.
     bool Write_Emit_FMT(uint8_t msg_type);
 
+    // output a FMT message if not already done so
+    void Safe_Write_Emit_FMT(uint8_t msg_type);
+
     // write a log message out to the log of msg_type type, with
     // values contained in arg_list:
     bool Write(uint8_t msg_type, va_list arg_list, bool is_critical=false, bool is_streaming=false);