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我一直认为WriteFile比fwrite更有效,因为fwrite在内部调用WriteFile,但是下面的测试代码告诉我fwrite比WriteFile更快.

写入成本为2毫秒,而WriteFile需要27000(FILE_ATTRIBUTE_NORMAL),每次写入调用后都会刷新.如果我用FILE_FLAG_WRITE_THROUGH调用WriteFile,并注释FlushFileBuffers(wfile)行,WriteFile会更快,成本为800.

那真的是fwrite调用WriteFile吗？是什么让这么大的差异？fwrite如何在内部工作？如何使用API​​比fwrite更有效地将数据写入文件？(unbufferd,synchronous).

   #include <Windows.h>
   #include <stdio.h>
   #include <iostream>

   int main() {
     FILE* cfile = fopen("file1.txt", "w");
     HANDLE wfile = CreateFile("file2.txt", GENERIC_WRITE, FILE_SHARE_READ, NULL, CREATE_ALWAYS, 
           /*FILE_ATTRIBUTE_NORMAL*/FILE_FLAG_WRITE_THROUGH, NULL);
     DWORD written = 0;

     DWORD start_time, end_time;
     char * text = "test message ha ha ha ha";
     int size = strlen(text);
     int times = 999;

     start_time = timeGetTime();
     for(int i = 0; i < times; ++i) {
       fwrite(text, 1, size, cfile);
       fflush(cfile);
     }
     end_time = timeGetTime();
     std::cout << end_time - start_time << '\n'; …