expatmm.h

/*
 * ExpatMM - C++ Wrapper for Expat available at http://expat.sourceforge.net/
 * Copyright (c) 2006, 2007, 2008, 2009 IntelliTree Solutions llc
 * Author: Coleman Kane <ckane@intellitree.com>
 *
 * Mutilated and forced into single-file solution by <jf@dockes.org>
 * Copyright (c) 2013-2023 J.F. Dockes
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General
 * Public License along with this library; if not, please feel free
 * to contact the author listed above.
 */
#ifndef _EXPATMM_EXPATXMLPARSER_H
#define _EXPATMM_EXPATXMLPARSER_H
 
#include <expat.h>
 
#include <cstring>
#include <map>
#include <sstream>
#include <string>
#include <vector>
 
#ifdef _MSC_VER
#define EXPATMM_SSIZE_T int
#else
#define EXPATMM_SSIZE_T ssize_t
#endif
 
class ExpatXMLParser {
public:
 
    /* Create a new parser, using the default Chunk Size */
    ExpatXMLParser(void) {
        init();
    }
 
    /* Create a new parser, using a user-supplied chunk size */
    explicit ExpatXMLParser(size_t chunk_size) {
        init(chunk_size);
    }
 
    /* Destructor that cleans up xml_buffer and parser */
    virtual ~ExpatXMLParser(void) {
        valid_parser = false;
        if(expat_parser != nullptr) {
            XML_ParserFree(expat_parser);
            expat_parser = nullptr;
        }
        if(xml_buffer != nullptr) {
            delete [] xml_buffer;
            xml_buffer = nullptr;
        }
    }
 
    ExpatXMLParser(const ExpatXMLParser&) = delete;
    ExpatXMLParser& operator=(const ExpatXMLParser&) = delete;
 
    /*
      Generic Parser. Most derivations will simply call this, rather
      than implement their own. This will loop, processing XML data
      and calling the necessary handler code until an error is encountered.
    */
    virtual bool Parse(void) {
        /* Ensure that the parser is ready */
        if(!Ready())
            return false;
 
        EXPATMM_SSIZE_T bytes_read;
        /* Loop, reading the XML source block by block */
        while((bytes_read = read_block()) >= 0) {
            if(bytes_read > 0) {
                XML_Status local_status =
                    XML_Parse(expat_parser, getReadBuffer(), int(bytes_read), XML_FALSE);
 
                if(local_status != XML_STATUS_OK) {
                    set_status(local_status);
                    break;
                }
 
                /* Break on successful "short read", in event of EOF */
                if(getLastError() == XML_ERROR_FINISHED)
                    break;
            }
        }
 
        /* Finalize the parser */
        if((getStatus() == XML_STATUS_OK) || (getLastError() == XML_ERROR_FINISHED)) {
            XML_Status local_status = XML_Parse(expat_parser, getBuffer(), 0, XML_TRUE);
            if(local_status != XML_STATUS_OK) {
                set_status(local_status);
                return false;
            }
            return true;
        }
 
        /* Return false in the event of an error. The parser is
           not finalized on error. */
        return false;
    }
 
    /* Expose status, error, and control codes to users */
    virtual bool Ready(void) const {
        return valid_parser;
    }
    virtual XML_Error getLastError(void) const {
        return last_error;
    }
    virtual XML_Status getStatus(void) const {
        return status;
    }
    virtual XML_Size getLastErrorLine(void) const {
        return last_error_line;
    }
    virtual XML_Size getLastErrorColumn(void) const {
        return last_error_column;
    }
    virtual std::string getLastErrorMessage(void) const {
        return last_error_message;
    }
 
protected:
    class StackEl {
    public:
        explicit StackEl(const char* nm) : name(nm) {}
        std::string name;
        XML_Size start_index;
        std::map<std::string,std::string> attributes;
        std::string data;
    };
    std::vector<StackEl> m_path;
 
    virtual XML_Char *getBuffer(void) {
        return xml_buffer;
    }
    virtual const char *getReadBuffer(void) {
        return xml_buffer;
    }
    virtual size_t getBlockSize(void) {
        return xml_buffer_size;
    }
 
    /* Read XML data.
     *
     * Override this to implement your container-specific parser.
     *
     * You must:
     * put new XML data into xml_buffer
     * set status
     * set last_error
     * return the amount of XML_Char's written to xml_buffer
     *
     * on error, return < 0. The contents of xml_buffer will be
     * thrown away in this event, so it is the derived class's
     * responsibility to reseek the "data cursor" to re-get any
     * data in the buffer on an error condition.
     *
     * Use setReadiness, setStatus, and setLastError to handle
     * error, status, and control events and codes.
     *
     * The default implementation returns "no elements" if it is
     * ever called. and should be overridden by the derived class.
     *
     * Note that, as the actual parser only uses
     * getBuffer()/getBlockSize()/read_block() (no direct access
     * to the buffer), you are free to use an entirely different
     * I/O mechanism, like what does the inputRefXMLParser below.
     */
    virtual EXPATMM_SSIZE_T read_block(void) {
        last_error = XML_ERROR_NO_ELEMENTS;
        status = XML_STATUS_ERROR;
        return -1;
    }
 
    virtual void setReadiness(bool ready) {
        valid_parser = ready;
    }
    virtual void setStatus(XML_Status new_status) {
        status = new_status;
    }
    virtual void setLastError(XML_Error new_last_error) {
        last_error = new_last_error;
    }
 
    /* Methods to be overriden */
    virtual void StartElement(const XML_Char *, const XML_Char **) {}
    virtual void EndElement(const XML_Char *) {}
    virtual void CharacterData(const XML_Char *, int) {}
    virtual void ProcessingInstruction(const XML_Char *, const XML_Char *) {}
    virtual void CommentData(const XML_Char *) {}
    virtual void DefaultHandler(const XML_Char *, int) {}
    virtual void CDataStart(void) {}
    virtual void CDataEnd(void) {}
 
    /* The handle for the parser (expat) */
    XML_Parser expat_parser;
 
private:
 
    /* Temporary buffer where data is streamed in */
    XML_Char *xml_buffer;
    size_t xml_buffer_size;
 
    /* Tells if the parser is ready to accept data */
    bool valid_parser;
 
    /* Status and Error codes in the event of unforseen events */
    void set_status(XML_Status ls) {
        status = ls;
        last_error = XML_GetErrorCode(expat_parser);
        last_error_line = XML_GetCurrentLineNumber(expat_parser);
        last_error_column= XML_GetCurrentColumnNumber(expat_parser);
        std::ostringstream oss;
        oss << XML_ErrorString(last_error) <<
            " at line " << last_error_line << " column " <<
            last_error_column;
        last_error_message = oss.str();
    }
 
    XML_Status status;
    XML_Error last_error;
    XML_Size last_error_line{0};
    XML_Size last_error_column{0};
    std::string last_error_message;
 
    /* Expat callbacks.
     * The expatmm protocol is to pass (this) as the userData argument
     * in the XML_Parser structure. These static methods will convert
     * handlers into upcalls to the instantiated class's virtual members
     * to do the actual handling work. */
    static void _element_start_handler(void *userData, const XML_Char *name,
                                       const XML_Char **atts) {
        auto me = static_cast<ExpatXMLParser*>(userData);
        if(me != nullptr) {
            me->m_path.emplace_back(name);
            StackEl& lastelt = me->m_path.back();
            lastelt.start_index = XML_GetCurrentByteIndex(me->expat_parser);
            for (int i = 0; atts[i] != nullptr; i += 2) {
                lastelt.attributes[atts[i]] = atts[i+1];
            }
            me->StartElement(name, atts);
        }
    }
    static void _element_end_handler(void *userData, const XML_Char *name) {
        auto me = static_cast<ExpatXMLParser*>(userData);
        if(me != nullptr) {
            me->EndElement(name);
            me->m_path.pop_back();
        }
    }
    static void _character_data_handler(void *userData,
                                        const XML_Char *s, int len) {
        auto me = static_cast<ExpatXMLParser*>(userData);
        if(me != nullptr) me->CharacterData(s, len);
    }
    static void _processing_instr_handler(void *userData,
                                          const XML_Char *target,
                                          const XML_Char *data) {
        auto me = static_cast<ExpatXMLParser*>(userData);
        if(me != nullptr) me->ProcessingInstruction(target, data);
    }
    static void _comment_handler(void *userData, const XML_Char *data) {
        auto me = static_cast<ExpatXMLParser*>(userData);
        if(me != nullptr) me->CommentData(data);
    }
    static void _default_handler(void *userData, const XML_Char *s, int len) {
        auto me = static_cast<ExpatXMLParser*>(userData);
        if(me != nullptr) me->DefaultHandler(s, len);
    }
    static void _cdata_start_handler(void *userData) {
        auto me = static_cast<ExpatXMLParser*>(userData);
        if(me != nullptr) me->CDataStart();
    }
    static void _cdata_end_handler(void *userData) {
        auto me = static_cast<ExpatXMLParser*>(userData);
        if(me != nullptr) me->CDataEnd();
    }
    /* Register our static handlers with the Expat events. */
    void register_default_handlers() {
        XML_SetElementHandler(expat_parser, &_element_start_handler,
                              &_element_end_handler);
        XML_SetCharacterDataHandler(expat_parser, &_character_data_handler);
        XML_SetProcessingInstructionHandler(expat_parser,
                                            &_processing_instr_handler);
        XML_SetCommentHandler(expat_parser, &_comment_handler);
        XML_SetCdataSectionHandler(expat_parser, &_cdata_start_handler,
                                   &_cdata_end_handler);
        XML_SetDefaultHandler(expat_parser, &_default_handler);
    }
    /* Constructor common code */
    void init(size_t chunk_size = 0) {
        valid_parser = false;
        expat_parser = nullptr;
        xml_buffer_size = chunk_size ? chunk_size : 10240;
        xml_buffer = new XML_Char[xml_buffer_size];
        if(xml_buffer == nullptr)
            return;
        expat_parser = XML_ParserCreate(nullptr);
 
        if(expat_parser == nullptr) {
            delete [] xml_buffer;
            xml_buffer = nullptr;
            return;
        }
        status = XML_STATUS_OK;
        last_error = XML_ERROR_NONE;
 
        memset(xml_buffer, 0, xml_buffer_size * sizeof(XML_Char));
 
        /* Set the "ready" flag on this parser */
        valid_parser = true;
        XML_SetUserData(expat_parser, this);
        register_default_handlers();
    }
};
 
class inputRefXMLParser : public ExpatXMLParser {
public:
    // Beware: we only use a ref to input to minimize copying. This means
    // that storage for the input parameter must persist until you are done
    // with the parser object !
    explicit inputRefXMLParser(const std::string& input)
        : ExpatXMLParser(1), // Have to allocate a small buf even if not used.
          m_input(input) {
    }
 
protected:
    EXPATMM_SSIZE_T read_block(void) override {
        if (getLastError() == XML_ERROR_FINISHED) {
            setStatus(XML_STATUS_OK);
            return -1;
        }
        setLastError(XML_ERROR_FINISHED);
        return m_input.size();
    }
    const char *getReadBuffer() override {
        return m_input.c_str();
    }
    size_t getBlockSize(void) override {
        return m_input.size();
    }
protected:
    const std::string& m_input;
};
 
#endif /* _EXPATMM_EXPATXMLPARSER_H */