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C 中每个块复制一个文件块

发布于 2024-11-10 09:31:35 字数 62 浏览 1 评论 0原文

我试图将一个文件分成 x 个大小为 y （以字节为单位）的块，以便我可以单独复制每个块。我怎样才能做到这一点？

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愛上了 2024-11-17 09:31:35

尝试使用 fread 。

char buffer[ysize];
fread(buffer, ysize, 1, fp);

每次从文件中读取缓冲区中的 ysize 字节时，

Try using fread

char buffer[ysize];
fread(buffer, ysize, 1, fp);

Each time you read ysize bytes in buffer from the file.

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厌倦 2024-11-17 09:31:35

一些 struct stat 结构中包含其他成员，这些成员在复制文件时非常有用：

     st_blksize  The optimal I/O block size for the file.

     st_blocks   The actual number of blocks allocated for the file in
                 (check local system).

如果您读取的块大小是 st_blksize 的偶数倍，您往往会更有效地读取文件。

   size_t   desiredSize = 1E4;                // largest buffer size to read into
   size_t   blocks = desiredSize / st.st_blksize;
   if ( blocks < 1 )              // fail safe test
       blocks = 1;
   size_t   true_size = blocks * st.st_blksize;     // this is the size to read
   char *buffer = malloc(true_size);

st_blksize 失败，提供缓冲区大小的 BUFSIZ 宏。

Some struct stat structures have additional members in them that prove useful when copying files:

     st_blksize  The optimal I/O block size for the file.

     st_blocks   The actual number of blocks allocated for the file in
                 (check local system).

If the block size you read is an even multiple of st_blksize you tend to get more efficient reading of the file.

   size_t   desiredSize = 1E4;                // largest buffer size to read into
   size_t   blocks = desiredSize / st.st_blksize;
   if ( blocks < 1 )              // fail safe test
       blocks = 1;
   size_t   true_size = blocks * st.st_blksize;     // this is the size to read
   char *buffer = malloc(true_size);

Failing st_blksize, <stdio.h> provides a BUFSIZ macro for buffer size.

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拥醉 2024-11-17 09:31:35

x = fopen ( "x" , "rb");
if (x==NULL) {perror("file could not be opened"); exit(1);}

y = fopen ( "y" , "wb");
if (x==NULL) {perror("file could not be opened"); exit(1);}

char* buf = (char*) malloc (sizeof(char)*1024); //1024 is buffer size

要将 1024 个字符读入缓冲区：

fread(buf, sizeof(char), 1024, x);

您将完成其余的工作。

x = fopen ( "x" , "rb");
if (x==NULL) {perror("file could not be opened"); exit(1);}

y = fopen ( "y" , "wb");
if (x==NULL) {perror("file could not be opened"); exit(1);}

char* buf = (char*) malloc (sizeof(char)*1024); //1024 is buffer size

To read 1024 chars into the buffer: