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动态数组设置程序sarray20:效率与操作功能解析

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28KB | 更新于2024-11-04 | 173 浏览量 | 0 下载量 举报 收藏
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动态数组与静态数组相比,优势在于它能在运行时根据实际情况扩展或缩减其容量,这在处理数据量不确定的场景中尤其有用。本资源包中的动态数组设置程序名为 'sarray20.rar',它实现了动态数组的基本操作,包括增加元素、删除数组头部或尾部的元素,并对一般数组的效率进行了比较分析。 该程序可能是一个用C++语言编写的软件项目,其中包含了多个文件,例如 'sarray20.cpp' 是程序的主要实现文件,而 'sarray20Dlg.cpp' 和 'sarray20Dlg.h' 很可能是用于创建和管理对话框界面的文件。'sarray20.h' 可能包含了动态数组类的声明,而 'StdAfx.cpp' 和 'StdAfx.h' 通常是用来包含标准预编译头和项目中常用的宏定义等。项目文件如 'sarray20.dsp' 和 'sarray20.dsw' 分别是基于Visual Studio的项目设置文件,用于配置项目的构建设置和工作空间设置。 在实现动态数组时,需要考虑以下几个关键点: 1. 内存管理:动态数组通常在堆上分配内存,因此需要合理管理内存的分配和释放,避免内存泄漏。程序可能会使用 `new` 和 `delete` 操作符来动态分配和释放内存。 2. 数组扩容与缩容:当数组需要存储更多元素时,动态数组必须能够扩展其容量。这通常涉及到重新分配一块更大的内存区域,并将现有元素拷贝到新内存区域中。同样,当数组元素数量减少时,程序应释放不再需要的内存,或者预留一定的空间以备后续扩展。 3. 访问效率:虽然动态数组提供了灵活性,但频繁地扩容缩容会增加开销,影响性能。因此,合理的选择扩容策略(例如每次扩容增加一定比例的容量)以及提供快速的元素访问能力,是动态数组设计中的重要考量。 4. 界面交互:在图形用户界面程序中,用户通常通过界面上的按钮、文本框等控件与程序交互。因此,'sarray20Dlg.cpp' 和 'sarray20Dlg.h' 文件中可能包含了处理这些交互动作的代码,如按钮点击事件的回调函数等。 5. 错误处理:在动态数组操作中,可能会出现诸如数组越界、内存分配失败等错误情况。因此程序中应该包含错误处理机制,确保程序稳定运行。 6. 性能比较:为了评估动态数组相对于静态数组的性能优势和劣势,程序中可能包含了一些基准测试代码,用于测量不同操作的执行时间,并进行比较。 综上所述,'sarray20.rar' 提供了一个动态数组的实现示例,可以作为一个学习和参考的资源,帮助开发者理解动态数组的工作原理及其在程序设计中的应用。"

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bool jpg_to_lcd (int * lcd_mp,char * filename,int start_x,int start_y) { //参数有效性分析,判断LCD内存映射的地址是否有效 if(NULL == lcd_mp) { printf("lcd mp is invaild\n"); return false; } /* This struct contains the JPEG decompression parameters and pointers to * working space (which is allocated as needed by the JPEG library). */ struct jpeg_decompress_struct cinfo; /* We use our private extension JPEG error handler. * Note that this struct must live as long as the main JPEG parameter * struct, to avoid dangling-pointer problems. */ struct jpeg_error_mgr jerr; /* More stuff */ FILE * infile; /* source file */ unsigned char * buffer; /* Output row buffer */ int row_stride; /* physical row width in output buffer */ /* In this example we want to open the input file before doing anything else, * so that the setjmp() error recovery below can assume the file is open. * VERY IMPORTANT: use "b" option to fopen() if you are on a machine that * requires it in order to read binary files. */ if ((infile = fopen(filename, "rb")) == NULL) { fprintf(stderr, "can't open %s\n", filename); return false; } /* Step 1: allocate and initialize JPEG decompression object */ /* We set up the normal JPEG error routines, then override error_exit. */ cinfo.err = jpeg_std_error(&jerr); /* Now we can initialize the JPEG decompression object. */ jpeg_create_decompress(&cinfo); /* Step 2: specify data source (eg, a file) */ jpeg_stdio_src(&cinfo, infile); /* Step 3: read file parameters with jpeg_read_header() */ (void) jpeg_read_header(&cinfo, TRUE); /* We can ignore the return value from jpeg_read_header since * (a) suspension is not possible with the stdio data source, and * (b) we passed TRUE to reject a tables-only JPEG file as an error. * See libjpeg.txt for more info. */ //判断图片是否超出分辨率 if(cinfo.output_width > 800 || cinfo.output_height > 480) { printf("[%s] width or height is too long\n", filename); return false; } /* Step 4: set parameters for decompression */ /* In this example, we don't need to change any of the defaults set by * jpeg_read_header(), so we do nothing here. */ /* Step 5: Start decompressor */ (void) jpeg_start_decompress(&cinfo); /* We can ignore the return value since suspension is not possible * with the stdio data source. */ /* We may need to do some setup of our own at this point before reading * the data. After jpeg_start_decompress() we have the correct scaled * output image dimensions available, as well as the output colormap * if we asked for color quantization. * In this example, we need to make an output work buffer of the right size. */ /* JSAMPLEs per row in output buffer */ row_stride = cinfo.output_width * cinfo.output_components; //计算一行的大小 /* Make a one-row-high sample array that will go away when done with image */ buffer = calloc(1,row_stride); /* Step 6: while (scan lines remain to be read) */ /* jpeg_read_scanlines(...); */ /* Here we use the library's state variable cinfo.output_scanline as the * loop counter, so that we don't have to keep track ourselves. */ int data = 0; while (cinfo.output_scanline < cinfo.output_height) { /* jpeg_read_scanlines expects an array of pointers to scanlines. * Here the array is only one element long, but you could ask for * more than one scanline at a time if that's more convenient. */ (void) jpeg_read_scanlines(&cinfo, &buffer, 1); //从上到下,从左到右 RGB RGB RGB RGB for (int i = 0; i < cinfo.output_width; ++i) //012 345 { data |= buffer[3*i]<<16; //R data |= buffer[3*i+1]<<8; //G data |= buffer[3*i+2]; //B //把像素点写入到LCD的指定位置 lcd_mp[800*start_y + start_x + 800*(cinfo.output_scanline-1) + i] = data; data = 0; } } /* Step 7: Finish decompression */ (void) jpeg_finish_decompress(&cinfo); /* We can ignore the return value since suspension is not possible * with the stdio data source. */ /* Step 8: Release JPEG decompression object */ /* This is an important step since it will release a good deal of memory. */ jpeg_destroy_decompress(&cinfo); /* After finish_decompress, we can close the input file. * Here we postpone it until after no more JPEG errors are possible, * so as to simplify the setjmp error logic above. (Actually, I don't * think that jpeg_destroy can do an error exit, but why assume anything...) */ fclose(infile); /* At this point you may want to check to see whether any corrupt-data * warnings occurred (test whether jerr.pub.num_warnings is nonzero). */ /* And we're done! */ return true; } 这段代码每句话的意思

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