IO/config: parse from XML/JSON formatted string

added Config specialization class (ConfigStringParser) to read and write
XML (or JSON) directly on c++ string. The class is useful to exhange  info without passing from filesystem each time.

Enhanced IO integration tests 2 e 4 to prove the capabilities of the new class.

Author: roccoarpa

src/IO/configuration.cpp

@@ -25,6 +25,7 @@
 
 #include "configuration.hpp"
 #include "configuration_XML.hpp"
+#include "compiler.hpp"
 
 #if HAS_RAPIDJSON_LIB
 #include "configuration_JSON.hpp"
@@ -360,4 +361,113 @@ namespace config {
 
 }
 
+/*!
+    \class ConfigStringParser
+    \ingroup Configuration
+    \brief Configuration parser to c++ string
+
+    This class implements a configuration parser to absorb/flush directly on 
+    c++ string buffers.
+*/
+
+
+/*!
+    Construct a new parser.
+
+    \param XMLorJSON false to activate XML format, true for JSON format if supported,
+    otherwise fallback automatically to XML.
+*/
+ConfigStringParser::ConfigStringParser(bool XMLorJSON)
+    : Config(false)
+{
+#if HAS_RAPIDJSON_LIB
+    m_xmlOrJson = XMLorJSON;
+#else
+    BITPIT_UNUSED(XMLorJSON);
+    //revert to default XML
+    m_xmlOrJson = false;
+#endif
+}
+
+/*!
+    Construct a new parser, activating multiSections support.
+
+    \param XMLorJSON false to activate XML format, true for JSON format if supported,
+    otherwise fallback automatically to XML.
+    \param multiSections if set to true the configuration parser will allow
+    multiple sections with the same name
+*/
+ConfigStringParser::ConfigStringParser(bool XMLorJSON, bool multiSections)
+    : Config(multiSections)
+{
+#if HAS_RAPIDJSON_LIB
+    m_xmlOrJson = XMLorJSON;
+#else
+    BITPIT_UNUSED(XMLorJSON)
+    //revert to default XML
+    m_xmlOrJson = false;
+#endif
+}
+
+/*!
+    Return a bool to identify the format targeted by the class to parse/write the 
+    buffer string. 0 is XML, 1 is JSON 
+
+    \return boolean identifying the target format 
+*/
+bool ConfigStringParser::getFormat()
+{
+    return m_xmlOrJson;
 }
+
+/*!
+    Absorb the targeted buffer string formatted as specified in class construction
+    (XML or JSON).
+
+    \param source target buffer string to read
+    \param append controls if the buffer string contents will be appended to the
+    current configuration or if the current configuration will be overwritten
+    by them.
+*/
+void ConfigStringParser::read(const std::string &source, bool append)
+{
+    // Processing not-append requests
+    if (!append) {
+        Config::clear();
+    }
+
+    if(m_xmlOrJson){
+#if HAS_RAPIDJSON_LIB
+        config::JSON::readBufferConfiguration(source, this);
+#endif
+    }else{
+        config::XML::readBufferConfiguration(source, this);
+    }
+}
+
+/*!
+    Flush the configuration to a buffer string, with the format specified
+    in class construction (XML or JSON).
+
+    \param source target buffer string to write on
+    \param append controls if the configuration contents will be appended to the
+    target string or if the string will be overwritten by them.
+*/
+void ConfigStringParser::write(std::string &source, bool append) const
+{
+    // Processing not-append requests
+    if (!append) {
+        source.clear();
+    }
+
+    if(m_xmlOrJson){
+#if HAS_RAPIDJSON_LIB
+        config::JSON::writeBufferConfiguration(source, this);
+#endif
+    }else{
+        config::XML::writeBufferConfiguration(source, this, "root");
+    }
+
+}
+
+}

src/IO/configuration.hpp

@@ -102,6 +102,23 @@ namespace config {
 
 };
 
+// Configuration parsing from/ writing to string 
+class ConfigStringParser : public Config
+{
+
+public:
+    ConfigStringParser(bool XMLorJSON = false);
+    ConfigStringParser(bool XMLorJSON, bool multiSections);
+
+    bool getFormat();
+
+    void read(const std::string &source, bool append = true);
+    void write(std::string & source, bool append = true) const;
+
+private:
+    bool m_xmlOrJson;
+};
+
 }
 
 #endif

src/IO/configuration_JSON.cpp

@@ -109,6 +109,42 @@ void readConfiguration(const std::string &filename, Config *rootConfig)
     readNode("", jsonRoot, rootConfig);
 }
 
+/*!
+    Reading a json dictionary from plain c++ string and fill a bitpit::Config tree
+    accordingly.
+
+    String Encoding is always considered of UTF-8 type .
+
+    \param[in] source string with JSON contents
+    \param[in,out] rootConfig is a pointer to Config tree that will be used
+    to store the data read from the string
+*/
+void readBufferConfiguration(const std::string &source, Config *rootConfig)
+{
+    if (!rootConfig) {
+        throw std::runtime_error("JSON::readDoc Null Config tree structure passed");
+    }
+
+    // Open a UTF-8 compliant rapidjson::StringStream
+    rapidjson::StringStream str(source.c_str());
+    // Parse stream directly
+    rapidjson::Document jsonRoot;
+    jsonRoot.ParseStream(str);
+
+    // Handle parse errors
+    if (jsonRoot.HasParseError()) {
+        std::string message = "JSON:readBufferConfiguration error of type : ";
+        message += std::string(rapidjson::GetParseError_En(jsonRoot.GetParseError()));
+        throw std::runtime_error(message.c_str());
+    }
+
+    // Root should be an object, bitpit doens't support root arrays.
+    assert(jsonRoot.IsObject() && "JSON:readBufferConfiguration parsed document root is not an object");
+
+    // Fill the configuration
+    readNode("", jsonRoot, rootConfig);
+}
+
 /*!
     Read recursively a json object content and fill accordingly the Config tree
     branch.
@@ -246,6 +282,43 @@ void writeConfiguration(const std::string &filename, const Config *rootConfig, b
     std::fclose(fp);
 }
 
+/*!
+    Write a bitpit::Config tree contents to json formatted c++ string.
+
+    NOTE: JSON root document object does not have a key name unlike XML.
+
+    Tree contents will be written to a plain c++ string, with UTF-8 standard encoding, and 
+    appended to any previous content of the source string.
+    
+    \param[in] source string to write JSON contents.
+    \param[in] rootConfig pointer to the Config tree to be written on target string
+*/
+void writeBufferConfiguration(std::string &source, const Config *rootConfig)
+{
+    if (!rootConfig) {
+        throw std::runtime_error("JSON::writeConfiguration Null Config tree structure passed");
+    }
+
+    // DOM Document is GenericDocument<UTF8<>>
+    rapidjson::Document jsonRoot;
+
+    // Get the allocator
+    rapidjson::Document::AllocatorType &allocator = jsonRoot.GetAllocator();
+
+    // Create a root node and recursively fill it
+    jsonRoot.SetObject();
+    writeNode(rootConfig, jsonRoot, allocator);
+
+    // Write on a buffer with initial capacity 1024
+    rapidjson::StringBuffer buffer(0, 1024);
+
+    // Use single-ultracompact UTF-8 JSON format
+    rapidjson::Writer<rapidjson::StringBuffer> writer(buffer);
+    jsonRoot.Accept(writer);
+
+    source += std::string(buffer.GetString());
+}
+
 /*!
     Write recursively Config tree contents to JSON objects
 

src/IO/configuration_JSON.hpp

@@ -36,9 +36,11 @@ namespace config {
 namespace JSON {
 
 void readConfiguration(const std::string &filename, Config *rootConfig);
+void readBufferConfiguration(const std::string &source, Config *rootConfig);
 void readNode(const std::string &key, const rapidjson::Value &value, Config *config);
 
 void writeConfiguration(const std::string &filename, const Config *rootConfig, bool prettify = true);
+void writeBufferConfiguration(std::string &source, const Config *rootConfig);
 void writeNode(const Config *config, rapidjson::Value &rootJSONData, rapidjson::Document::AllocatorType &allocator);
 
 std::string decodeValue(const rapidjson::Value &value);

src/IO/configuration_XML.cpp

@@ -26,6 +26,7 @@
 #include <libxml/parser.h>
 #include <stdexcept>
 #include <string>
+#include <cstring>
 
 #include "configuration_XML.hpp"
 
@@ -216,6 +217,41 @@ void readConfiguration(const std::string &filename, const std::string &rootname,
     xmlCleanupParser();
 }
 
+/*!
+    Read xml information from a plain xml-formatted std::string and fill the Config tree.
+    The method is meant for general-purpose xml info absorbing. So no version checking 
+    is done in this context, nor rootname one. 
+    \param source string containing all the info formatted in XML style.
+    \param rootConfig pointer to Config tree to store data parsed from the string.
+*/
+void readBufferConfiguration(const std::string &source, Config *rootConfig)
+{
+    if (!rootConfig) {
+        throw std::runtime_error("XML::readConfiguration Null Config tree structure passed");
+    }
+
+    // Macro to check API for match with the DLL we are using
+    LIBXML_TEST_VERSION
+
+    // Read the XML string
+    const char * cstr = source.c_str();
+    xmlDoc *doc = xmlParseMemory(cstr, strlen(cstr));
+    if (doc == nullptr) {
+        throw std::runtime_error("Could not parse XML configuration string: \"" + source + "\"");
+    }
+
+    // Get the root element
+    xmlNode * rootElement = xmlDocGetRootElement(doc);
+
+    //read it as usual
+    readNode(rootElement->children, rootConfig);
+
+    // Clean-up
+    xmlFreeDoc(doc);
+    xmlCleanupParser();
+}
+
+
 /*!
     Write the configuration to the specified file.
 
@@ -283,6 +319,75 @@ void writeConfiguration(const std::string &filename, const std::string &rootname
     xmlFreeTextWriter(writer);
 }
 
+/*!
+    Write the Config Tree to a c++ string (xml-stringfication). All contents will 
+    be appended to the target source string.
+    The method is meant for general-purpose xml info flushing.  
+    \param source string to write to
+    \param rootConfig pointer to the Config tree to be stringfied.
+    \param rootname (optional) name of the root section. Default is "root".
+*/
+void writeBufferConfiguration(std::string &source, const Config *rootConfig, const std::string &rootname)
+{
+    if (!rootConfig) {
+        throw std::runtime_error("XML::writeConfiguration Null Config tree structure passed");
+    }
+
+    int status;
+
+    xmlBufferPtr buffer = xmlBufferCreate();
+    if (buffer == NULL) {
+        throw std::runtime_error("Error creating the writing buffer");
+    }
+    // Create a new XmlWriter for DOM tree acting on memory buffer, with no compression
+    xmlTextWriterPtr writer = xmlNewTextWriterMemory(buffer, 0);
+    if (writer == NULL) {
+        throw std::runtime_error("Error creating the xml buffer writer");
+    }
+    //no indent.
+    xmlTextWriterSetIndent(writer, 0);
+
+    // Start the document
+    status = xmlTextWriterStartDocument(writer, NULL, DEFAULT_ENCODING.c_str(), NULL);
+    if (status < 0) {
+        throw std::runtime_error("Error at xmlTextWriterStartDocument");
+    }
+
+    // Start the root element
+    xmlChar *elementName = encodeString(rootname, DEFAULT_ENCODING);
+    status = xmlTextWriterStartElement(writer, BAD_CAST elementName);
+    if (status < 0) {
+        throw std::runtime_error("Error at xmlTextWriterStartElement");
+    }
+
+    // Attribute version is not relevant in this context.
+
+    // Write the configuration
+    writeNode(writer, rootConfig, DEFAULT_ENCODING);
+
+    // End section
+    status = xmlTextWriterEndElement(writer);
+    if (status < 0) {
+        throw std::runtime_error("Error at xmlTextWriterEndElement");
+    }
+
+    // Close the document
+    status = xmlTextWriterEndDocument(writer);
+    if (status < 0) {
+        throw std::runtime_error("Error at xmlTextWriterEndDocument");
+    }
+
+    // free the XML writer
+    xmlFreeTextWriter(writer);
+
+    //buffer is still hanging on, append its contents to the output string
+    //xmlChar (aka unsigned char) simple casting to char should be enough
+    source += std::string(reinterpret_cast<char*>(buffer->content));
+
+    //free the buffer
+    xmlBufferFree(buffer);
+}
+
 }
 
 }

src/IO/configuration_XML.hpp

@@ -38,9 +38,11 @@ namespace XML {
 extern const std::string DEFAULT_ENCODING;
 
 void readConfiguration(const std::string &filename, const std::string &rootname, bool checkVersion, int version, Config *rootConfig);
+void readBufferConfiguration(const std::string &source,  Config *rootConfig);
 void readNode(xmlNodePtr root, Config *config);
 
 void writeConfiguration(const std::string &filename, const std::string & rootname, int version, const Config *rootConfig);
+void writeBufferConfiguration(std::string &source, const Config *rootConfig, const std::string &rootname = "root");
 void writeNode(xmlTextWriterPtr writer, const Config *config, const std::string &encoding = DEFAULT_ENCODING);
 
 xmlChar * encodeString(const std::string &in, const std::string &encoding);