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Variable-width encodings can be used in both byte strings and wide strings. String length and offsets are measured in bytes or wchar_t, not in "characters", which can be confusing to beginning programmers. UTF-8 and Shift JIS are often used in C byte strings, while UTF-16 is often used in C wide strings when wchar_t is 16 bits.
Only a small subset of possible byte strings are error-free UTF-8: several bytes cannot appear; a byte with the high bit set cannot be alone; and in a truly random string a byte with a high bit set has only a 1 ⁄ 15 chance of starting a valid UTF-8 character. This has the (possibly unintended) consequence of making it easy to detect if a ...
[8] [9] [10] However, it is common to store the subset of ASCII or UTF-8 – every character except NUL – in null-terminated strings. Some systems use "modified UTF-8" which encodes NUL as two non-zero bytes (0xC0, 0x80) and thus allow all possible strings to be stored. This is not allowed by the UTF-8 standard, because it is an overlong ...
The std::string type is the main string datatype in standard C++ since 1998, but it was not always part of C++. From C, C++ inherited the convention of using null-terminated strings that are handled by a pointer to their first element, and a library of functions that manipulate such strings.
UTF-8-encoded, preceded by varint-encoded integer length of string in bytes Repeated value with the same tag or, for varint-encoded integers only, values packed contiguously and prefixed by tag and total byte length — Smile \x21
Instead of performing on individual bits, byte-level operators perform on strings of eight bits (known as bytes) at a time. The reason for this is that a byte is normally the smallest unit of addressable memory (i.e. data with a unique memory address).
In most encodings, this is translated to a single code unit with a zero value. For instance, in UTF-8 it is a single zero byte. However, in Modified UTF-8 the null character is encoded as two bytes: 0xC0,0x80. This allows the byte with the value of zero, which is now not used for any character, to be used as a string terminator.
The change was made "to clear the way for the potential future use of tag characters for a purpose other than to represent language tags". [8] Unicode states that "the use of tag characters to represent language tags in a plain text stream is still a deprecated mechanism for conveying language information about text. [8]