Avoid sscanf for parsing config lines

alc/alconfig.cpp

@@ -224,35 +224,28 @@ void LoadConfigFromFile(std::istream &f)
             continue;
         }
 
-        auto cmtpos = buffer.find('#');
-        if(cmtpos != std::string::npos)
-            buffer.resize(cmtpos);
-        while(!buffer.empty() && std::isspace(buffer.back()))
-            buffer.pop_back();
-        if(buffer.empty()) continue;
+        auto cmtpos = std::min(buffer.find('#'), buffer.size());
+        while(cmtpos > 0 && std::isspace(buffer[cmtpos-1]))
+            --cmtpos;
+        if(!cmtpos) continue;
+        buffer.erase(cmtpos);
 
-        const char *line{&buffer[0]};
-        char key[256]{};
-        char value[256]{};
-        if(std::sscanf(line, "%255[^=] = \"%255[^\"]\"", key, value) == 2 ||
-           std::sscanf(line, "%255[^=] = '%255[^\']'", key, value) == 2 ||
-           std::sscanf(line, "%255[^=] = %255[^\n]", key, value) == 2)
+        auto sep = buffer.find('=');
+        if(sep == std::string::npos)
         {
-            /* sscanf doesn't handle '' or "" as empty values, so clip it
-             * manually. */
-            if(std::strcmp(value, "\"\"") == 0 || std::strcmp(value, "''") == 0)
-                value[0] = 0;
-        }
-        else if(std::sscanf(line, "%255[^=] %255[=]", key, value) == 2)
-        {
-            /* Special case for 'key =' */
-            value[0] = 0;
-        }
-        else
-        {
-            ERR(" config parse error: malformed option line: \"%s\"\n\n", line);
+            ERR(" config parse error: malformed option line: \"%s\"\n", buffer.c_str());
             continue;
         }
+        auto keyend = sep++;
+        while(keyend > 0 && std::isspace(buffer[keyend-1]))
+            --keyend;
+        if(!keyend)
+        {
+            ERR(" config parse error: malformed option line: \"%s\"\n", buffer.c_str());
+            continue;
+        }
+        while(sep < buffer.size() && std::isspace(buffer[sep]))
+            sep++;
 
         std::string fullKey;
         if(!curSection.empty())
@@ -260,26 +253,34 @@ void LoadConfigFromFile(std::istream &f)
             fullKey += curSection;
             fullKey += '/';
         }
-        fullKey += key;
-        while(!fullKey.empty() && std::isspace(fullKey.back()))
-            fullKey.pop_back();
+        fullKey += buffer.substr(0u, keyend);
 
-        TRACE(" found '%s' = '%s'\n", fullKey.c_str(), value);
+        std::string value{(sep < buffer.size()) ? buffer.substr(sep) : std::string{}};
+        if(value.size() > 1)
+        {
+            if((value.front() == '"' && value.back() == '"')
+                || (value.front() == '\'' && value.back() == '\''))
+            {
+                value.pop_back();
+                value.erase(value.begin());
+            }
+        }
+
+        TRACE(" found '%s' = '%s'\n", fullKey.c_str(), value.c_str());
 
         /* Check if we already have this option set */
-        auto ent = std::find_if(ConfOpts.begin(), ConfOpts.end(),
-            [&fullKey](const ConfigEntry &entry) -> bool
-            { return entry.key == fullKey; }
-        );
+        auto find_key = [&fullKey](const ConfigEntry &entry) -> bool
+        { return entry.key == fullKey; };
+        auto ent = std::find_if(ConfOpts.begin(), ConfOpts.end(), find_key);
         if(ent != ConfOpts.end())
         {
-            if(value[0])
-                ent->value = expdup(value);
+            if(!value.empty())
+                ent->value = expdup(value.c_str());
             else
                 ConfOpts.erase(ent);
         }
-        else if(value[0])
-            ConfOpts.emplace_back(ConfigEntry{std::move(fullKey), expdup(value)});
+        else if(!value.empty())
+            ConfOpts.emplace_back(ConfigEntry{std::move(fullKey), expdup(value.c_str())});
     }
     ConfOpts.shrink_to_fit();
 }