How to convert std::string to std::vector?

Question

The data format required to save games on google play game services is : std::vector<uint8_t> as specified under 'Data formats' on: https://developers.google.com/games/services/cpp/savedgames

I am assuming the vector represents some kind of byte array. Is that correct ? So how does one convert an std::string to std::vector<uint8_t> ?

If you want to do it char-by-char, you could loop and cast/add elements to a vector... — qxz, Jan 19 '17 at 08:40

score 44 · Accepted Answer · answered Jan 19 '17 at 08:41

44

std::vector has a constructor just for this purpose:

std::string str;
std::vector<uint8_t> vec(str.begin(), str.end());

answered Jan 19 '17 at 08:41

DeiDei

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Possible signed/unsigned conversion error/warning? Other than that, spot on. – StoryTeller - Unslander Monica Jan 19 '17 at 08:42
Don't you need to add `'\0'` if you want the whole content of a string ? – pSoLT Jan 19 '17 at 08:45
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@pSoLT- No. The NUL terminator is considered part of the string. `end` points one past it. – StoryTeller - Unslander Monica Jan 19 '17 at 08:47
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@pSoLT: the terminating zero is part of the C-style string convention, not part of the C++ string and normally `std::vector`should not be considered a string. – stefaanv Jan 19 '17 at 08:48
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@StoryTeller: I disagree (see previous comment) – stefaanv Jan 19 '17 at 08:48
@stefaanv - In the current standard, the `data` member must return a NUL terminated string. Ergo, `end` points one past it. – StoryTeller - Unslander Monica Jan 19 '17 at 08:49
Can you convert back to a string as well ? – Rahul Iyer Jan 19 '17 at 08:50
@stefaanv I guess the whole point is to store it byte-wise. Without null terminator, how do you distinguish the strings after reading if from file (assuming there can be many) ? – pSoLT Jan 19 '17 at 08:50
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Nope, I just did the test in [coliru](http://coliru.stacked-crooked.com/a/ec0c8286510593bd) – stefaanv Jan 19 '17 at 08:51
@stefaanv But if we need to convert back to a string, shouldn't we store the \0 as well ? – Rahul Iyer Jan 19 '17 at 08:52
Yes, but you have to do it yourself. Or store the size before. – stefaanv Jan 19 '17 at 08:53
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@StoryTeller Nope, `std::string`'s storage has an additional null byte at the end, but it's not part of the string proper. – T.C. Jan 19 '17 at 08:55
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@T.C. - Yes, I stand corrected. The [reference for `data()`](http://en.cppreference.com/w/cpp/string/basic_string/data) confirms it. – StoryTeller - Unslander Monica Jan 19 '17 at 08:57
Is this also working for std::vector vec(str.begin(), str.end()); ?? What would be a correct input for str? – sqp_125 Sep 11 '18 at 06:26
@sqp_125 It would assign a bunch of doubles with ASCII values. Same as `double a = 98; \\ 'b'` – DeiDei Sep 11 '18 at 11:02
Yeah true.... and how to convert these values than back to the originall double values? – sqp_125 Sep 11 '18 at 17:39

Jesse Jutson · Answer 2 · 2021-08-03T14:38:51.153

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Adding to DeiDei's answer, you can do the following if the vector is already constructed:

std::string str;
std::vector<uint8_t> vec;
...
vec.assign(str.begin(), str.end());

edited Aug 03 '21 at 14:38

answered Mar 29 '19 at 08:23

Jesse Jutson

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How to convert std::string to std::vector?

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