Fixes ATCmdParser OOB handling performance-wise

The issue is that the process_oob check would only return immediately
if no data at all on entry, or when receiving a known OOB. Any other
line noise or unknown OOBs could lead to a timeout delay - read the
noise or unknown OOB then timeout waiting for another line of input.

This revised version modifies the parser to recheck readable after each
line end when only looking for OOBs, so it can immediate exit.

Author: kjbracey

platform/ATCmdParser.cpp

@@ -215,7 +215,8 @@ bool ATCmdParser::vrecv(const char *response, std::va_list args)
 restart:
     _aborted = false;
     // Iterate through each line in the expected response
-    while (response[0]) {
+    // response being NULL means we just want to check for OOBs
+    while (!response || response[0]) {
         // Since response is const, we need to copy it into our buffer to
         // add the line's null terminator and clobber value-matches with asterisks.
         //
@@ -224,7 +225,7 @@ bool ATCmdParser::vrecv(const char *response, std::va_list args)
         int offset = 0;
         bool whole_line_wanted = false;
 
-        while (response[i]) {
+        while (response && response[i]) {
             if (response[i] == '%' && response[i + 1] != '%' && response[i + 1] != '*') {
                 _buffer[offset++] = '%';
                 _buffer[offset++] = '*';
@@ -257,6 +258,11 @@ bool ATCmdParser::vrecv(const char *response, std::va_list args)
         int j = 0;
 
         while (true) {
+            // If just peeking for OOBs, and at start of line, check
+            // readability
+            if (!response && j == 0 && !_fh->readable()) {
+                return false;
+            }
             // Receive next character
             int c = getc();
             if (c < 0) {
@@ -284,6 +290,7 @@ bool ATCmdParser::vrecv(const char *response, std::va_list args)
                 if ((unsigned)j == oob->len && memcmp(
                             oob->prefix, _buffer + offset, oob->len) == 0) {
                     debug_if(_dbg_on, "AT! %s\n", oob->prefix);
+                    _oob_cb_count++;
                     oob->cb();
 
                     if (_aborted) {
@@ -302,7 +309,7 @@ bool ATCmdParser::vrecv(const char *response, std::va_list args)
                 // Don't attempt scanning until we get delimiter if they included it in format
                 // This allows recv("Foo: %s\n") to work, and not match with just the first character of a string
                 // (scanf does not itself match whitespace in its format string, so \n is not significant to it)
-            } else {
+            } else if (response) {
                 sscanf(_buffer + offset, _buffer, &count);
             }
 
@@ -388,52 +395,9 @@ void ATCmdParser::abort()
 
 bool ATCmdParser::process_oob()
 {
-    if (!_fh->readable()) {
-        return false;
-    }
-
-    int i = 0;
-    while (true) {
-        // Receive next character
-        int c = getc();
-        if (c < 0) {
-            return false;
-        }
-        // Simplify newlines (borrowed from retarget.cpp)
-        if ((c == CR && _in_prev != LF) ||
-                (c == LF && _in_prev != CR)) {
-            _in_prev = c;
-            c = '\n';
-        } else if ((c == CR && _in_prev == LF) ||
-                   (c == LF && _in_prev == CR)) {
-            _in_prev = c;
-            // onto next character
-            continue;
-        } else {
-            _in_prev = c;
-        }
-        _buffer[i++] = c;
-        _buffer[i] = 0;
-
-        // Check for oob data
-        struct oob *oob = _oobs;
-        while (oob) {
-            if (i == (int)oob->len && memcmp(
-                        oob->prefix, _buffer, oob->len) == 0) {
-                debug_if(_dbg_on, "AT! %s\r\n", oob->prefix);
-                oob->cb();
-                return true;
-            }
-            oob = oob->next;
-        }
-
-        // Clear the buffer when we hit a newline or ran out of space
-        // running out of space usually means we ran into binary data
-        if (((i + 1) >= _buffer_size) || (c == '\n')) {
-            debug_if(_dbg_on, "AT< %s", _buffer);
-            i = 0;
-        }
-    }
+    int pre_count = _oob_cb_count;
+    recv(NULL);
+    return _oob_cb_count != pre_count;
 }
 
 }

platform/ATCmdParser.h

@@ -66,6 +66,7 @@ class ATCmdParser : private NonCopyable<ATCmdParser> {
     // Parsing information
     const char *_output_delimiter;
     int _output_delim_size;
+    int _oob_cb_count;
     char _in_prev;
     bool _dbg_on;
     bool _aborted;
@@ -91,7 +92,7 @@ class ATCmdParser : private NonCopyable<ATCmdParser> {
      */
     ATCmdParser(FileHandle *fh, const char *output_delimiter = "\r",
                 int buffer_size = 256, int timeout = 8000, bool debug = false)
-        : _fh(fh), _buffer_size(buffer_size), _in_prev(0), _oobs(NULL)
+        : _fh(fh), _buffer_size(buffer_size), _oob_cb_count(0), _in_prev(0), _oobs(NULL)
     {
         _buffer = new char[buffer_size];
         set_timeout(timeout);