CODEWITHSUNDEEP
cstringchar
Alex Matt
Alex Matt

Reputation: 209

Length of Greek character string is larger than it should be

I'm writing a program and I take a string of Greek characters as input and when I print its len, it outputs its double. For example, if ch="ΑΒ"(greek characters) or ch="αβ",

printf("%d",strlen(ch)); outputs 4 instead of 2. And if ch="ab", it outputs 2. What's going on?

Upvotes: 2

Views: 637

Answers (2)

Jinlye
Jinlye

Reputation: 2254

Probably because your string is encoded using variable-width character encoding.

In the good old days, we only bothered with 128 different characters: a-z, A-Z, 0-9, and some commas and brackets and control things. Everything was taken care of in 7 bits, and we called it ASCII. Then that wasn't enough and we added some other things like letters with lines or dots on top, and we went to 8 bits (1 byte) and could do any of 256 characters in one byte. (Although people's ideas of what should go in those extra 128 slots varied widely, based on what was most useful in their language - see comment from usr2564301 - and you then had to say whose version you were using for what should be in those extra slots.)

If you had 2 characters in your string, it would be 2 bytes long (plus a null terminator perhaps), always.

But then people woke up to the fact that English isn't the only language in the world, and there were in fact thousands of letters in hundreds of languages around the globe. Now what to do?

Well, we could say there are only about 65,000 characters that interest us, and encode all letters in two bytes. There are some encoding formats that do this. A two-letter string will then always be 4 bytes (um, perhaps with some byte order mark at the front, and maybe a null terminator at the end). Two problems: a) not very backwards compatible with ASCII, and b) wasteful of bytes if most text is stuff that is in the good ol' ASCII character set anyway.

Step in UTF-8, which I'll wager is what your string is using for its encoding, or something similar. ASCII characters, like 'a' and 'b', are encoded with one byte, and more exotic characters (--blush-- from an English-speaking perspective) take up more than one byte, of which the first byte is to say "what follows is to be taken along with this byte to represent a letter". So you get variable-width encoding. So the length of a two-letter string will be at least two bytes, but if it includes non-ASCII characters, it'll be more.

Upvotes: 1

purec
purec

Reputation: 318

You can use mbstowcs() function to convert multybite string to wide-character string. And then use wcslen() to determine it's length.

Upvotes: 1

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