Guarantees needed to read several bytes from file to struct

Asked Oct 18 '21 at 21:47

Active Oct 18 '21 at 21:47

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I have a file that contains 7 bytes as little endian, where there is the following:

4 bytes for an int
2 bytes for an unsigned int16
1 byte for a char (signed)

Let's assume I have a struct :

struct A
{
int32_t a;
uint16_t b;
int8_t c;
}

What guarantees do I need on the compiler so that I'm ""alowed"" by the standard to just copy the memory from the file into the struct base adress, without reading member per member ? Is being little endian and having sizeof(A) == 7 enough ?

asked Oct 18 '21 at 21:47

lezebulon

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i think here is your answer, https://stackoverflow.com/questions/9127246/copy-struct-to-struct-in-c/9127315 – Danilo Mercado Oudalova Oct 18 '21 at 21:53
Padding could (almost certainly will) screw up that `sizeof(A) == 7` assumption. – user4581301 Oct 18 '21 at 22:19
Most compilers allow you to change the padding on a struct. But it isn't standard. – Jerry Jeremiah Oct 19 '21 at 01:49
Here is another question asking how to copy a character array to a struct that might help: https://stackoverflow.com/questions/11621836/copying-array-to-a-structure The answer to that questions answers your question really well. – Jerry Jeremiah Oct 19 '21 at 01:52

Guarantees needed to read several bytes from file to struct

0 Answers0