SDL2.0例子代码分析---代码运行平台检测

简介

SDL2.0例子程序中的 testplatform项目代码分析 ,针对不同的平台 检测字节序 CPU支持的指令集 类型宽度 以及断言

代码+注释

#include <stdio.h>#include "SDL.h"#include "SDL_endian.h"#include "SDL_cpuinfo.h"#include "SDL_assert.h"/* *  该例子代码检测运行平台 *///判断变量占用字节数 是否等于 hardcodetypestatic intbadsize(size_t sizeoftype, size_t hardcodetype){return sizeoftype != hardcodetype;}//检测系统是否出现错误类型   貌似用处不大这段坑爹代码 //如果平台类型错误 返回1 否则返回  0intTestTypes(SDL_bool verbose){int error = 0;//如果Uint8占用一个字节if (badsize(sizeof(Uint8), 1)){//如果Uint8不等于1那么输出 实际占用尺寸 if (verbose)SDL_Log("sizeof(Uint8) != 1, instead = %u\n",(unsigned int)sizeof(Uint8));//错误次数++++error;}//如如下类似 上述 if (badsize(sizeof(Uint16), 2)) {if (verbose)SDL_Log("sizeof(Uint16) != 2, instead = %u\n",(unsigned int)sizeof(Uint16));++error;}if (badsize(sizeof(Uint32), 4)) {if (verbose)SDL_Log("sizeof(Uint32) != 4, instead = %u\n",(unsigned int)sizeof(Uint32));++error;}if (badsize(sizeof(Uint64), 8)) {if (verbose)SDL_Log("sizeof(Uint64) != 8, instead = %u\n",(unsigned int)sizeof(Uint64));++error;}if (verbose && !error)SDL_Log("All data types are the expected size.\n");return (error ? 1 : 0);}//测试尾数  也就是机器的字节序  //windows默认是小端模式 //也就是 低位先存 原因是 堆栈是 由高地址向低地址扩展intTestEndian(SDL_bool verbose){int error = 0;Uint16 value = 0x1234;int real_byteorder;Uint16 value16 = 0xCDAB;Uint16 swapped16 = 0xABCD;Uint32 value32 = 0xEFBEADDE;Uint32 swapped32 = 0xDEADBEEF;Uint64 value64, swapped64;   //定义64位置 也就是 0x00000000EFBEADDEvalue64 = 0xEFBEADDE;//右移动32位  也就是四个字节value64 <<= 32;//将低位置为0xCDAB3412value64 |= 0xCDAB3412; //如下操作和value64雷同 swapped64 = 0x1234ABCD;swapped64 <<= 32;swapped64 |= 0xDEADBEEF;//打印机器字节序 是大端模式还是小端模式 if (verbose) {SDL_Log("Detected a %s endian machine.\n",(SDL_BYTEORDER == SDL_LIL_ENDIAN) ? "little" : "big");}//我们自己判断字节序 将value转换为 char类型之后 由于数据丢失 变成了0x34 在windows下低位先存 //所以 左移4位后变成了0x3了  也就是小端口模式if ((*((char *)&value) >> 4) == 0x1) {real_byteorder = SDL_BIG_ENDIAN;}else {real_byteorder = SDL_LIL_ENDIAN;}//如果我们分析的 真正的字节序不等于 SDL给出的字节序 那么 输出真正的字节序 error++if (real_byteorder != SDL_BYTEORDER) {if (verbose) {SDL_Log("Actually a %s endian machine!\n",(real_byteorder == SDL_LIL_ENDIAN) ? "little" : "big");}++error;}//交换字节序 输出 if (verbose) {SDL_Log("Value 16 = 0x%X, swapped = 0x%X\n", value16,SDL_Swap16(value16));}//如果交换后的值不等于 0xABCD if (SDL_Swap16(value16) != swapped16) {if (verbose) {SDL_Log("16 bit value swapped incorrectly!\n");}++error;}//交换32位高度字节序 if (verbose) {SDL_Log("Value 32 = 0x%X, swapped = 0x%X\n", value32,SDL_Swap32(value32));}if (SDL_Swap32(value32) != swapped32) {if (verbose) {SDL_Log("32 bit value swapped incorrectly!\n");}++error;}if (verbose) {  //如果是微软的编译器 也就是VC下 打印出64位的交换字节序之后的值#ifdef _MSC_VERSDL_Log("Value 64 = 0x%I64X, swapped = 0x%I64X\n", value64,SDL_Swap64(value64));#else  //如果是其他编译器 那么  64位置 ULONG 就需要定义为 unsigned long long 来代表 64位无符号 IntegerSDL_Log("Value 64 = 0x%llX, swapped = 0x%llX\n",(unsigned long long) value64,(unsigned long long) SDL_Swap64(value64));#endif}//判断交换后的值是否等于 0x1234ABCDDEADBEEF;if (SDL_Swap64(value64) != swapped64) {if (verbose) {SDL_Log("64 bit value swapped incorrectly!\n");}++error;}//返回错误状态return (error ? 1 : 0);}//检测CPU 的特性intTestCPUInfo(SDL_bool verbose){  if (verbose) {  //打印CPU数量SDL_Log("CPU count: %d\n", SDL_GetCPUCount()); //获取CPU Cache LIne的大小 即CPU 一次从主存Copy的内存大小SDL_Log("CPU cache line size: %d\n", SDL_GetCPUCacheLineSize());        //CPU是否支持RDTSC指令 读取时间标签计数器SDL_Log("RDTSC %s\n", SDL_HasRDTSC() ? "detected" : "not detected");///cpu 是否支持 Altivec  AltiVec提供了32个128比特向量暂存器,与之相比,SSE和SSE2只提供了8个SDL_Log("AltiVec %s\n", SDL_HasAltiVec() ? "detected" : "not detected");//cpu是否支持 MMX指令 SDL_Log("MMX %s\n", SDL_HasMMX() ? "detected" : "not detected"); //CPU是否支持SIMD ， 由AMD开发的一套SIMD多媒体指令集，支持单精度浮点数的矢量运算，用于增强x86架构的计算机在三维图像处理上的性能SDL_Log("3DNow! %s\n", SDL_Has3DNow() ? "detected" : "not detected"); //cpu是否支持SSESDL_Log("SSE %s\n", SDL_HasSSE() ? "detected" : "not detected");//SSE2是否支持 如下都是判断CPU是否支持一下加速指令集 SDL_Log("SSE2 %s\n", SDL_HasSSE2() ? "detected" : "not detected");SDL_Log("SSE3 %s\n", SDL_HasSSE3() ? "detected" : "not detected");SDL_Log("SSE4.1 %s\n", SDL_HasSSE41() ? "detected" : "not detected");SDL_Log("SSE4.2 %s\n", SDL_HasSSE42() ? "detected" : "not detected");SDL_Log("AVX %s\n", SDL_HasAVX() ? "detected" : "not detected");//获取系统RAM大小 也就是内存大小SDL_Log("System RAM %d MB\n", SDL_GetSystemRAM());}return (0);}intTestAssertions(SDL_bool verbose){  //sdl断言SDL_assert(0);SDL_assert_release(1);SDL_assert_paranoid(1);SDL_assert(0 || 1);SDL_assert_release(0 || 1);SDL_assert_paranoid(0 || 1);#if 0   /* enable this to test assertion failures. */SDL_assert_release(1 == 2);SDL_assert_release(5 < 4);SDL_assert_release(0 && "This is a test");#endif{  //获取所有的断言 链表  在调用SDL_GetAssertionReport 之前 /************************************************************************//*typedef struct SDL_assert_data{int always_ignore;unsigned int trigger_count;const char *condition;const char *filename;int linenum;const char *function;const struct SDL_assert_data *next;} SDL_assert_data;                                                                     *//************************************************************************/const SDL_assert_data *item = SDL_GetAssertionReport(); //我们发现就是取出所有的 断言结果 输出while (item) {SDL_Log("'%s', %s (%s:%d), triggered %u times, always ignore: %s.\n",item->condition, item->function, item->filename,item->linenum, item->trigger_count,item->always_ignore ? "yes" : "no");item = item->next;}}return (0);}intmain(int argc, char *argv[]){SDL_bool verbose = SDL_TRUE;int status = 0;/* 设置特定日志的优先级 这里是应用程序日志  */SDL_LogSetPriority(SDL_LOG_CATEGORY_APPLICATION, SDL_LOG_PRIORITY_INFO);//如果参数1= -q 那么设置 verbose=faslseif (argv[1] && (SDL_strcmp(argv[1], "-q") == 0)) {verbose = SDL_TRUE;}if (verbose) {SDL_Log("This system is running %s\n", SDL_GetPlatform());}//测试变量尺寸status += TestTypes(verbose);//测试尾数  也就是测试机器的字节序status += TestEndian(verbose);//测试CPU信息status += TestCPUInfo(verbose);//测试断言status += TestAssertions(verbose);return status;}

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