PFW-1523 Refactor parsing quoted strings

My plan is to re-use this function in M79
in a later commit. The firmware doesn't
have a dedicated parser like Marlin 2.1
so this is my attempt to not duplicate the parsing of a quoted string in G-codes

Change in memory (MK3S+ Multilang):
Flash: -50 bytes
SRAM: 0 bytes

Firmware/util.cpp

@@ -385,36 +385,16 @@ void gcode_level_check(uint16_t nGcodeLevel) {
     );
 }
 
-#define GCODE_DELIMITER '"'
-
-char *code_string(const char *pStr, size_t *nLength) {
-char* pStrBegin;
-char* pStrEnd;
-
-pStrBegin=strchr(pStr,GCODE_DELIMITER);
-if(!pStrBegin)
-     return(NULL);
-pStrBegin++;
-pStrEnd=strchr(pStrBegin,GCODE_DELIMITER);
-if(!pStrEnd)
-     return(NULL);
-*nLength=pStrEnd-pStrBegin;
-return pStrBegin;
-}
 
 void printer_smodel_check(const char *pStrPos, const char *actualPrinterSModel) {
-    char* pResult;
+    unquoted_string smodel = unquoted_string(pStrPos);
-    size_t nLength;
-    size_t aLength;
 
-    pResult=code_string(pStrPos,&nLength);
+    if(smodel.WasFound()) {
-    if(pResult != NULL) {
+        const uint8_t compareLength = strlen_P(actualPrinterSModel);
-        aLength=strlen_P(actualPrinterSModel);
-        if(aLength > nLength) nLength = aLength;
 
-        // Only compare first 6 chars on MK3|MK3S if string longer than 4 characters
+        if(compareLength == smodel.GetLength()) {
-        if (nLength > 4 && strncmp_P(pResult, PSTR("MK3"), 3) == 0) nLength = 6;
+            if (strncmp_P(smodel.GetUnquotedString(), actualPrinterSModel, compareLength) == 0) return;
-        if (strncmp_P(pResult, actualPrinterSModel, nLength) == 0) return;
+        }
     }
 
     render_M862_warnings(

Firmware/util.h

@@ -1,5 +1,6 @@
 #pragma once
 #include <stdint.h>
+#include <string.h>
 
 extern const uint16_t FW_VERSION_NR[4];
 const char* FW_VERSION_STR_P();
@@ -84,6 +85,45 @@ enum class ClCompareValue:uint_least8_t
     _Greater=2
 };
 
+struct unquoted_string {
+public:
+    /// @brief Given a pointer to a quoted string, filter out the quotes
+    /// @param pStr A constant pointer to a constant string to be searched/filtered. Modifying the pointer is strictly forbidden.
+    unquoted_string(const char * const pStr)
+    : len(0)
+    , found(false)
+    {
+        char * pStrEnd = NULL;
+
+        // Start of the string
+        this->ptr = strchr(pStr, '"');
+        if (!this->ptr) {
+            // First quote not found
+            return;
+        }
+
+        // Skip the leading quote
+        this->ptr++; 
+
+        // End of the string
+        pStrEnd = strchr(this->ptr, '"');
+        if(!pStrEnd) {
+            // Second quote not found
+            return;
+        }
+        this->len = pStrEnd - this->ptr;
+        this->found = true;
+    }
+
+    bool WasFound() { return found; }
+    uint8_t GetLength() { return len; }
+    const char * GetUnquotedString() { return ptr; }
+private:
+    const char * ptr = NULL;
+    uint8_t len;
+    bool found;
+};
+
 extern ClNozzleDiameter oNozzleDiameter;
 extern ClCheckMode oCheckMode;
 extern ClCheckModel oCheckModel;