expat & scew

從 PHP 中認識來的 Expat http://download1.csdn.net/down3/20070607/07111232845.gz

• Expat是一個XML的解析器, 透過它可以讓PHP程式解讀XML文件的結構和內容
  
  
• 一般XML解析器分為兩種基本類型
  • 樹狀解析器(Tree-based parser): XML文件轉換成樹狀結構. 這類解析器 分析整篇文章, 同時提供一個API來訪問所產生樹的每個元素. 其通用 的標準為DOM(文件物件模式)
    
    
  • 事件解析器(Event-based parser): 將XML文件視為一系列的事件來handler. 當一個特殊事件發生時, 解析器將透過程式所提供的函數來處理.
  
  
  
• 事件解析器 有一個XML文件的資料中心檢視(data-centric view), 也就是說, 它集中在 XML文件的資料部分, 而不是其結構. 這些解析器從頭到尾處理文件, 並將類似於－ 元素的開始、元素的結尾、特徵資料的開始等－事件通過回覆（callback）函數報 告給應用程式。
  
  
• 而Expat就是屬於 事件解析器 的一種。
  
  
• Expat是一個不會去判斷XML文件是否有效的解析器，因此可以忽略任何與文件關 聯的DTD，但是XML文件格式仍然需要完整（表示DTD還是得存在），否則Expat （和其他符合XML標準的解析器一樣）將會隨著出錯資訊而停止。
  
  
• 範例如下 
  藉由 SCEW(scew-0.3.2.tar.gz) 所直接處理的範例
  • scew_print.c : 用來解讀指定參數的 xml 檔案.
  • scew_write.c : 用來寫出指定參數的 xml 檔案.
    

/** * * @file     scew_print.c * @author   Aleix Conchillo Flaque <[e-mail]> * @date     Wed Dec 04, 2002 01:11 * @brief    SCEW usage example * * $Id: scew_print.c,v 1.20 2004/01/29 22:38:33 aleix Exp $ * * @if copyright * * Copyright (C) 2002, 2003, 2004 Aleix Conchillo Flaque * * SCEW 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. * * SCEW 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, write to the Free Software * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA. * * @endif * * This example shows the usage of the API provided by SCEW. It will * print an XML file given as the first program parameter. *//** * You will probably need to change this include to <scew/scew.h> in you * program. */#include <scew/scew.h>#include <stdio.h>/* indentation size (in whitespaces) */int const indent_size = 4;voidprint_indent(unsigned int indent){    if (indent > 0)    {        printf("%*s", indent * indent_size, " ");    }}voidprint_attributes(scew_element* element){    scew_attribute* attribute = NULL;    if (element != NULL)    {        /**         * Iterates through the element's attribute list, printing the         * pair name-value.         */        attribute = NULL;        while ((attribute = scew_attribute_next(element, attribute)) != NULL)        {            printf(" %s=/"%s/"", scew_attribute_name(attribute),                   scew_attribute_value(attribute));        }    }}voidprint_element(scew_element* element, unsigned int indent){    scew_element* child = NULL;    XML_Char const* contents = NULL;    if (element == NULL)    {        return;    }    /**     * Prints the starting element tag with its attributes.     */    print_indent(indent);    printf("<%s", scew_element_name(element));    print_attributes(element);    printf(">");    contents = scew_element_contents(element);    if (contents == NULL)    {        printf("/n");    }    /**     * Call print_element function again for each child of the     * current element.     */    child = NULL;    while ((child = scew_element_next(element, child)) != NULL)    {        print_element(child, indent + 1);    }    /* Prints element's content. */    if (contents != NULL)    {        printf("%s", contents);    }    else    {        print_indent(indent);    }    /**     * Prints the closing element tag.     */    printf("</%s>/n", scew_element_name(element));}intmain(int argc, char** argv){    scew_tree* tree = NULL;    scew_parser* parser = NULL;    if (argc < 2)    {        printf("usage: scew_print file.xml/n");        return EXIT_FAILURE;    }    /**     * Creates an SCEW parser. This is the first function to call.     */    parser = scew_parser_create();    scew_parser_ignore_whitespaces(parser, 1);    /* Loads an XML file */    if (!scew_parser_load_file(parser, argv[1]))    {        scew_error code = scew_error_code();        printf("Unable to load file (error #%d: %s)/n", code,               scew_error_string(code));        if (code == scew_error_expat)        {            enum XML_Error expat_code = scew_error_expat_code(parser);            printf("Expat error #%d (line %d, column %d): %s/n", expat_code,                   scew_error_expat_line(parser),                   scew_error_expat_column(parser),                   scew_error_expat_string(expat_code));        }        return EXIT_FAILURE;    }    tree = scew_parser_tree(parser);    /* Prints full tree */    print_element(scew_tree_root(tree), 0);    /* Remember to free tree (scew_parser_free does not free it) */    scew_tree_free(tree);    /* Frees the SCEW parser */    scew_parser_free(parser);    return 0;}

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/** * * @file     scew_write.c * @author   Aleix Conchillo Flaque <[e-mail]> * @date     Sun Mar 30, 2003 12:21 * @brief    SCEW usage example * * $Id: scew_write.c,v 1.5 2004/01/29 22:38:34 aleix Exp $ * * @if copyright * * Copyright (C) 2002, 2003, 2004 Aleix Conchillo Flaque * * SCEW 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. * * SCEW 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, write to the Free Software * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA. * * @endif * * This example shows the usage of the API provided by SCEW. It will * create a new XML and write it to a file. * * We will create an XML with the follwing structure: * *     <scew_test> *         <element> *             element contents. *         </element> *         <element attribute="value"/> *         <element attribute1="value1" attribute2="value2"/> *         <element> *             <sub_element attribute="value"/> *             <sub_element attribute1="value1" attribute2="value2"> *                 <sub_sub_element attribute="value"> *                   element contents. *                 </sub_sub_element> *             </sub_element> *         </element> *     </scew_test> *//** * You will probably need to change this include to <scew/scew.h> in you * program. */#include <scew/scew.h>#include <stdio.h>intmain(int argc, char** argv){    scew_tree* tree = NULL;    scew_element* root = NULL;    scew_element* element = NULL;    scew_element* sub_element = NULL;    scew_element* sub_sub_element = NULL;    scew_attribute* attribute = NULL;    if (argc < 2)    {        printf("usage: scew_write new_file.xml/n");        return EXIT_FAILURE;    }    /**     * Create an empty XML tree in memory, and add a root element     * "scew_test".     */    tree = scew_tree_create();    root = scew_tree_add_root(tree, "scew_test");    /* Add an element and set element contents. */    element = scew_element_add(root, "element");    scew_element_set_contents(element, "element contents.");    /* Add an element with an attribute pair (name, value). */    element = scew_element_add(root, "element");    scew_element_add_attr_pair(element, "attribute", "value");    element = scew_element_add(root, "element");    scew_element_add_attr_pair(element, "attribute1", "value1");    /**     * Another way to add an attribute. You loose attribute ownership,     * so there is no need to free it.     */    attribute = scew_attribute_create("attribute2", "value2");    scew_element_add_attr(element, attribute);    element = scew_element_add(root, "element");    sub_element = scew_element_add(element, "sub_element");    scew_element_add_attr_pair(sub_element, "attribute", "value");    sub_element = scew_element_add(element, "sub_element");    scew_element_add_attr_pair(sub_element, "attribute1", "value1");    scew_element_add_attr_pair(sub_element, "attribute2", "value2");    sub_sub_element = scew_element_add(sub_element, "sub_sub_element");    scew_element_add_attr_pair(sub_sub_element, "attribute", "value");    scew_element_set_contents(sub_sub_element, "element contents.");    /**     * Save an XML tree to a file.     */    if (!scew_writer_tree_file(tree, argv[1]))    {        printf("Unable to create %s/n", argv[1]);        return EXIT_FAILURE;    }    /* Frees the SCEW tree */    scew_tree_free(tree);    return 0;}