通过fread和fseek读取文件 [英] Reading files by fread and fseek

问题描述

我使用fread和fseek逐字节读取一些文件，但是使用下面的代码，它只读取前七个字节。

我怎么能让它读取34个字节？



我尝试过：

i use fread and fseek to read some file byte by byte, but with the following code , it reads only the the first seven bytes.
how can i let it read 34 bytes?

What I have tried:

static FILE *fp;

static int u32FilePointer = 35;

static int u32FilePointer=35;

for(i = 0; i < 5; i++)
       {
         fseek(fp, u32FilePointer, SEEK_SET);
         u16BytesRead = fread(u8Buffer, 1, 7, fp);
         printf("u32FilePointer : %lu\n" ,u32FilePointer);

推荐答案

您已经问过大多数相同的问题：

返回fread函数 [ ^ ]

阅读fread文档怎么样？

You already asked mostly the same question:
Return of fread function[^]
What about reading fread documentation ?

您的问题对我来说不是很清楚，但您的代码执行以下操作：



循环5次：

fseek使用SEEK_SETsets文件位置从文件开头到35 。

fread从该位置读取7个字节。



如果你打算读取前35个字节，你可以这样做：

Your question isn't quite clear to me, but your code does the following:

Loop 5 times:
fseek with SEEK_SETsets the file position to 35 from the beginning of the file.
fread reads 7 bytes from that position.

If you intend to read the first 35 bytes, you can just do:

fread(u8Buffer, 1, 35, fp);

如果您指定要从文件中的哪个位置读取多少字节，这将有所帮助。

It would help if you specify how many bytes you want to read from which position in the file.

您正在使用 FSEEK（ ）在循环内，以便在读取之前始终将文件位置设置为相同的位置。这导致5次读取相同的数据。



您还必须更新搜索位置：

You are using fseek() within the loop so that the file position is always set to the same position before reading. That results in reading the same data 5 times.

You have to update the seek position too:

for(i = 0; i < 5; i++)
{
    fseek(fp, u32FilePointer, SEEK_SET);
    u16BytesRead = fread(u8Buffer, 1, 7, fp);
    // The read updates the internal position of the file pointer
    // If we want to track the position we have to do it also for our variable
    u32FilePointer += u16BytesRead;
    // Or use ftell() to get the internal position
    //u32FilePointer = ftell(fp);
    printf("u32FilePointer : %lu\n" ,u32FilePointer);
}

在最后一次读取数据后应始终继续读取时，您还可以将 seek（）移出循环：

When reading should always continue after the last read data, you can also move the seek() out of the loop:

fseek(fp, u32FilePointer, SEEK_SET);
for(i = 0; i < 5; i++)
{
    u16BytesRead = fread(u8Buffer, 1, 7, fp);
    printf("u32FilePointer : %lu\n", ftell(fp));
}

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