[英]How to read contents of a file to a statically declared variable?
I have a data file in binary where the first four bytes are some integer that I want to read.我有一个二进制数据文件,其中前四个字节是我想读取的一些 integer。 I simply do:
我只是这样做:
int * num_rounters_p = malloc(sizeof(int));
fread(num_rounters_p, 4, 1, p_file);
printf("%d\n", *num_routers_p); // 10
This works fine (and please tell me if it doesn't,), however I do know the size of this particular value.这很好用(如果没有,请告诉我),但是我确实知道这个特定值的大小。 and so it isn't really necessary to store it dynamically.
因此实际上没有必要动态存储它。
Is it possible to do something like是否可以做类似的事情
int x = some_read_function(4, 1, p_file);
printf("%d\n", x); // 10
Basically storing the value on stack instead of the heap?基本上将值存储在堆栈而不是堆上? The code example above is of course not grounded in C, but I hope I got my point across:))
上面的代码示例当然不是基于 C,但我希望我明白我的意思:))
The most straightforward way would be最直接的方法是
int num_routers;
size_t items_read = fread( &num_routers, sizeof num_routers, 1, p_file );
if ( items_read < 1 )
{
// read error, handle as appropriate
}
else
{
// do something with num_routers
}
An int
is not guaranteed to be 4 bytes wide, it's only guaranteed to be at least 2 bytes wide, so it's safer to use sizeof num_routers
than a literal 4
.不保证
int
为 4 字节宽,仅保证至少为2 字节宽,因此使用sizeof num_routers
比使用文字4
更安全。 Of course, that assumes that the binary file was written on the same platform that you're reading from.当然,这假设二进制文件是在您正在读取的同一平台上编写的。
Nvm.非易失性。 Easy fix: Just do:
轻松修复:只需执行以下操作:
int num_routers;
fread(&num_routers, sizeof(int), 1, p_file);
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