ATCmdParser: merge scanf and recv functions

Author: Marcin Tomczyk

platform/ATCmdParser.h

@@ -222,7 +222,23 @@ class ATCmdParser : private NonCopyable<ATCmdParser> {
      */
     bool recv(const char *response, ...) MBED_SCANF_METHOD(1, 2);
 
-    bool vrecv(const char *response, std::va_list args);
+    /**
+     * Receive an AT response
+     *
+     * Receives a formatted response using scanf style formatting
+     * @see scanf
+     *
+     * Responses are parsed line at a time.
+     * If multiline is set to false parse only one line otherwise parse multiline response
+     * Any received data that does not match the response is ignored until
+     * a timeout occurs.
+     *
+     * @param response scanf-like format string of response to expect
+     * @param ... all scanf-like arguments to extract from response
+     * @param multiline determinate if parse one or multiple lines.
+     * @return number of bytes read or -1 on failure
+     */
+    int vrecvscanf(const char *response, std::va_list args, bool multiline);
 
     /**
      * Write a single byte to the underlying stream
@@ -282,8 +298,6 @@ class ATCmdParser : private NonCopyable<ATCmdParser> {
      */
     int scanf(const char *format, ...) MBED_SCANF_METHOD(1, 2);
 
-    int vscanf(const char *format, std::va_list args);
-
     /**
      * Attach a callback for out-of-band data
      *

platform/source/ATCmdParser.cpp

@@ -124,68 +124,6 @@ int ATCmdParser::vprintf(const char *format, std::va_list args)
     return i;
 }
 
-int ATCmdParser::vscanf(const char *format, std::va_list args)
-{
-    // Since format is const, we need to copy it into our buffer to
-    // add the line's null terminator and clobber value-matches with asterisks.
-    //
-    // We just use the beginning of the buffer to avoid unnecessary allocations.
-    int i = 0;
-    int offset = 0;
-
-    while (format[i]) {
-        if (format[i] == '%' && format[i + 1] != '%' && format[i + 1] != '*') {
-            _buffer[offset++] = '%';
-            _buffer[offset++] = '*';
-            i++;
-        } else {
-            _buffer[offset++] = format[i++];
-        }
-    }
-
-    // Scanf has very poor support for catching errors
-    // fortunately, we can abuse the %n specifier to determine
-    // if the entire string was matched.
-    _buffer[offset++] = '%';
-    _buffer[offset++] = 'n';
-    _buffer[offset++] = 0;
-
-    // To workaround scanf's lack of error reporting, we actually
-    // make two passes. One checks the validity with the modified
-    // format string that only stores the matched characters (%n).
-    // The other reads in the actual matched values.
-    //
-    // We keep trying the match until we succeed or some other error
-    // derails us.
-    int j = 0;
-
-    while (true) {
-        // Ran out of space
-        if (j + 1 >= _buffer_size - offset) {
-            return false;
-        }
-        // Receive next character
-        int c = getc();
-        if (c < 0) {
-            return -1;
-        }
-        _buffer[offset + j++] = c;
-        _buffer[offset + j] = 0;
-
-        // Check for match
-        int count = -1;
-        sscanf(_buffer + offset, _buffer, &count);
-
-        // We only succeed if all characters in the response are matched
-        if (count == j) {
-            // Store the found results
-            vsscanf(_buffer + offset, format, args);
-            return j;
-        }
-    }
-}
-
-
 // Command parsing with line handling
 bool ATCmdParser::vsend(const char *command, std::va_list args)
 {
@@ -211,7 +149,7 @@ bool ATCmdParser::vsend(const char *command, std::va_list args)
     return true;
 }
 
-bool ATCmdParser::vrecv(const char *response, std::va_list args)
+int ATCmdParser::vrecvscanf(const char *response, std::va_list args, bool multiline)
 {
 restart:
     _aborted = false;
@@ -259,17 +197,24 @@ bool ATCmdParser::vrecv(const char *response, std::va_list args)
         int j = 0;
 
         while (true) {
+            // Ran out of space
+            if (j + 1 >= _buffer_size - offset) {
+                return -1;
+            }
+
             // If just peeking for OOBs, and at start of line, check
             // readability
             if (!response && j == 0 && !_fh->readable()) {
-                return false;
+                return -1;
             }
+
             // Receive next character
             int c = getc();
             if (c < 0) {
                 debug_if(_dbg_on, "AT(Timeout)\n");
-                return false;
+                return -1;
             }
+
             // Simplify newlines (borrowed from retarget.cpp)
             if ((c == CR && _in_prev != LF) ||
                     (c == LF && _in_prev != CR)) {
@@ -283,24 +228,27 @@ bool ATCmdParser::vrecv(const char *response, std::va_list args)
             } else {
                 _in_prev = c;
             }
+
             _buffer[offset + j++] = c;
             _buffer[offset + j] = 0;
 
             // Check for oob data
-            for (struct oob *oob = _oobs; oob; oob = oob->next) {
-                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) {
-                        debug_if(_dbg_on, "AT(Aborted)\n");
-                        return false;
+            if (multiline) {
+                for (struct oob *oob = _oobs; oob; oob = oob->next) {
+                    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) {
+                            debug_if(_dbg_on, "AT(Aborted)\n");
+                            return false;
+                        }
+                        // oob may have corrupted non-reentrant buffer,
+                        // so we need to set it up again
+                        goto restart;
                     }
-                    // oob may have corrupted non-reentrant buffer,
-                    // so we need to set it up again
-                    goto restart;
                 }
             }
 
@@ -323,6 +271,10 @@ bool ATCmdParser::vrecv(const char *response, std::va_list args)
                 // Store the found results
                 vsscanf(_buffer + offset, _buffer, args);
 
+                if (!multiline) {
+                    return j;
+                }
+
                 // Jump to next line and continue parsing
                 response += i;
                 break;
@@ -337,7 +289,7 @@ bool ATCmdParser::vrecv(const char *response, std::va_list args)
         }
     }
 
-    return true;
+    return 1;
 }
 
 // Mapping to vararg functions
@@ -354,7 +306,7 @@ int ATCmdParser::scanf(const char *format, ...)
 {
     std::va_list args;
     va_start(args, format);
-    int res = vscanf(format, args);
+    int res = vrecvscanf(format, args, false);
     va_end(args);
     return res;
 }
@@ -372,9 +324,9 @@ bool ATCmdParser::recv(const char *response, ...)
 {
     std::va_list args;
     va_start(args, response);
-    bool res = vrecv(response, args);
+    int res = vrecvscanf(response, args, true);
     va_end(args);
-    return res;
+    return (res > 0) ? true : false;
 }
 
 // oob registration