How to hard code binary data to string

Question

I want to test serialized data conversion in my application, currently the object is stored in file and read the binary file and reloading the object.

In my unit test case I want to test this operation. As the file operations are costly I want to hard code the binary file content in the code itself.

How can I do this?

Currently I am trying like this,

std::string FileContent = "\00\00\00\00\00.........";

and it is not working.

Using std::string for binary data, beuhh... It would be simpler and cleaner to use a plain char array or if you don't like plain arrays a std::array or std::vector of characters. You would avoid stupid errors of stopping on first null when initializing from a const char *. — Serge Ballesta
– Serge Ballesta, Commented Jul 22, 2016 at 15:20
@GilsonPJ: try this: std::vector<uint8_t> FileContent = { 0x00, 0x00, 0x00, 0x00, 0x00, ... }; — lorro
– lorro, Commented Jul 22, 2016 at 15:42

lorro · Accepted Answer · 2016-07-22 15:22:40Z

2

You're right that a string can contain '\0', but here you're still initializing it from const char*, which, by definition, stops at the first '\0'. I'd recommend you to use uint8_t[] or even uint32_t[] (that is, without passing to std::string), even if the second might have up to 3 bytes of overhead (but it's more compact when in source). That's e.g. how X bitmaps are usually stored.

Another possibility is base64 encoding, which is printable but needs (a relatively quick) decoding.

If you really want to put the const char[] to a std::string, first convert the pointer to const char*, then use the two-iterator constructor of std::string. While it's true that std::string can hold '\0', it's somewhat an antipattern to store binary in a string, thus I'm not giving the exact code, just the hint.

edited Jul 22, 2016 at 15:22

answered Jul 22, 2016 at 15:17

lorro

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ctor · Accepted Answer · 2016-07-22 15:28:41Z

2

The following should do what you need, however probably not recommended as most people wouldn't expect an std::string to contain null bytes.

std::string FileContent { "\x00\x00\x00\x00\x00", 5 };

answered Jul 22, 2016 at 15:28

ctor

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