utf8: Update to match current version
* utf8/LICENSE, utf8/utf8/cpp11.h, utf8/utf8/cpp17.h: New files. * Makefile.am: Distribute them. * utf8/README.md, utf8/utf8/checked.h, utf8/utf8/core.h, utf8/utf8/unchecked.h: Update to the current version of utfcpp. * README: Add a link to the upstream github.
This commit is contained in:
Alexandre Duret-Lutz
parent
efee1c4130
commit
ff89601306
9 changed files with 897 additions and 194 deletions
681
utf8/README.md
681
utf8/README.md
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@ -3,9 +3,9 @@
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## Introduction
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Many C++ developers miss an easy and portable way of handling Unicode encoded strings. The original C++ Standard (known as C++98 or C++03) is Unicode agnostic. C++11 provides some support for Unicode on core language and library level: u8, u, and U character and string literals, char16_t and char32_t character types, u16string and u32string library classes, and codecvt support for conversions between Unicode encoding forms. In the meantime, developers use third party libraries like ICU, OS specific capabilities, or simply roll out their own solutions.
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C++ developers miss an easy and portable way of handling Unicode encoded strings. The original C++ Standard (known as C++98 or C++03) is Unicode agnostic. C++11 provides some support for Unicode on core language and library level: u8, u, and U character and string literals, char16_t and char32_t character types, u16string and u32string library classes, and codecvt support for conversions between Unicode encoding forms. In the meantime, developers use third party libraries like ICU, OS specific capabilities, or simply roll out their own solutions.
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In order to easily handle UTF-8 encoded Unicode strings, I came up with a small, C++98 compatible generic library. For anybody used to work with STL algorithms and iterators, it should be easy and natural to use. The code is freely available for any purpose - check out the license at the beginning of the utf8.h file. The library has been used a lot in the past ten years both in commercial and open-source projects and is considered feature-complete now. If you run into bugs or performance issues, please let me know and I'll do my best to address them.
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In order to easily handle UTF-8 encoded Unicode strings, I came up with a small, C++98 compatible generic library. For anybody used to work with STL algorithms and iterators, it should be easy and natural to use. The code is freely available for any purpose - check out the [license](./LICENSE). The library has been used a lot in the past ten years both in commercial and open-source projects and is considered feature-complete now. If you run into bugs or performance issues, please let me know and I'll do my best to address them.
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The purpose of this article is not to offer an introduction to Unicode in general, and UTF-8 in particular. If you are not familiar with Unicode, be sure to check out [Unicode Home Page](http://www.unicode.org/) or some other source of information for Unicode. Also, it is not my aim to advocate the use of UTF-8 encoded strings in C++ programs; if you want to handle UTF-8 encoded strings from C++, I am sure you have good reasons for it.
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@ -28,50 +28,78 @@ int main(int argc, char** argv)
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cout << "\nUsage: docsample filename\n";
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return 0;
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}
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const char* test_file_path = argv[1];
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// Open the test file (contains UTF-8 encoded text)
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// Open the test file (must be UTF-8 encoded)
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ifstream fs8(test_file_path);
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if (!fs8.is_open()) {
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cout << "Could not open " << test_file_path << endl;
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return 0;
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cout << "Could not open " << test_file_path << endl;
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return 0;
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}
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unsigned line_count = 1;
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string line;
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// Play with all the lines in the file
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while (getline(fs8, line)) {
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// check for invalid utf-8 (for a simple yes/no check, there is also utf8::is_valid function)
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// check for invalid utf-8 (for a simple yes/no check, there is also utf8::is_valid function)
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#if __cplusplus >= 201103L // C++ 11 or later
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auto end_it = utf8::find_invalid(line.begin(), line.end());
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#else
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string::iterator end_it = utf8::find_invalid(line.begin(), line.end());
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#endif // C++ 11
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if (end_it != line.end()) {
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cout << "Invalid UTF-8 encoding detected at line " << line_count << "\n";
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cout << "This part is fine: " << string(line.begin(), end_it) << "\n";
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}
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// Get the line length (at least for the valid part)
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int length = utf8::distance(line.begin(), end_it);
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cout << "Length of line " << line_count << " is " << length << "\n";
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// Convert it to utf-16
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#if __cplusplus >= 201103L // C++ 11 or later
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u16string utf16line = utf8::utf8to16(line);
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#else
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vector<unsigned short> utf16line;
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utf8::utf8to16(line.begin(), end_it, back_inserter(utf16line));
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// And back to utf-8
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#endif // C++ 11
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// And back to utf-8;
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#if __cplusplus >= 201103L // C++ 11 or later
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string utf8line = utf8::utf16to8(utf16line);
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#else
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string utf8line;
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utf8::utf16to8(utf16line.begin(), utf16line.end(), back_inserter(utf8line));
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#endif // C++ 11
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// Confirm that the conversion went OK:
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if (utf8line != string(line.begin(), end_it))
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cout << "Error in UTF-16 conversion at line: " << line_count << "\n";
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line_count++;
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}
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}
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return 0;
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}
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```
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In the previous code sample, for each line we performed a detection of invalid UTF-8 sequences with `find_invalid`; the number of characters (more precisely - the number of Unicode code points, including the end of line and even BOM if there is one) in each line was determined with a use of `utf8::distance`; finally, we have converted each line to UTF-16 encoding with `utf8to16` and back to UTF-8 with `utf16to8`.
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Note a different pattern of usage for old compilers. For instance, this is how we convert
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a UTF-8 encoded string to a UTF-16 encoded one with a pre - C++11 compiler:
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```cpp
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vector<unsigned short> utf16line;
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utf8::utf8to16(line.begin(), end_it, back_inserter(utf16line));
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```
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With a more modern compiler, the same operation would look like:
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```cpp
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u16string utf16line = utf8::utf8to16(line);
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```
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If `__cplusplus` macro points to a C++ 11 or later, the library exposes API that takes into
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account C++ standard Unicode strings and move semantics. With an older compiler, it is still
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possible to use the same functionality, just in a little less convenient way
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In case you do not trust the `__cplusplus` macro or, for instance, do not want to include
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the C++ 11 helper functions even with a modern compiler, define `UTF_CPP_CPLUSPLUS` macro
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before including `utf8.h` and assign it a value for the standard you want to use - the values are the same as for the `__cplusplus` macro. This can be also useful with compilers that are conservative in setting the `__cplusplus` macro even if they have a good support for a recent standard edition - Microsoft's Visual C++ is one example.
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### Checking if a file contains valid UTF-8 text
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Here is a function that checks whether the content of a file is valid UTF-8 encoded text without reading the content into the memory:
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@ -90,7 +118,7 @@ bool valid_utf8_file(const char* file_name)
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}
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```
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Because the function `utf8::is_valid()` works with input iterators, we were able to pass an `istreambuf_iterator` to it and read the content of the file directly without loading it to the memory first.
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Because the function `utf8::is_valid()` works with input iterators, we were able to pass an `istreambuf_iterator` to `it` and read the content of the file directly without loading it to the memory first.
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Note that other functions that take input iterator arguments can be used in a similar way. For instance, to read the content of a UTF-8 encoded text file and convert the text to UTF-16, just do something like:
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@ -113,10 +141,56 @@ void fix_utf8_string(std::string& str)
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The function will replace any invalid UTF-8 sequence with a Unicode replacement character. There is an overloaded function that enables the caller to supply their own replacement character.
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## Points of interest
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#### Design goals and decisions
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The library was designed to be:
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1. Generic: for better or worse, there are many C++ string classes out there, and the library should work with as many of them as possible.
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2. Portable: the library should be portable both accross different platforms and compilers. The only non-portable code is a small section that declares unsigned integers of different sizes: three typedefs. They can be changed by the users of the library if they don't match their platform. The default setting should work for Windows (both 32 and 64 bit), and most 32 bit and 64 bit Unix derivatives. Support for post C++03 language features is included for modern compilers at API level only, so the library should work even with pretty old compilers.
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3. Lightweight: follow the "pay only for what you use" guideline.
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4. Unintrusive: avoid forcing any particular design or even programming style on the user. This is a library, not a framework.
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#### Alternatives
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In case you want to look into other means of working with UTF-8 strings from C++, here is the list of solutions I am aware of:
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1. [ICU Library](http://icu.sourceforge.net/). It is very powerful, complete, feature-rich, mature, and widely used. Also big, intrusive, non-generic, and doesn't play well with the Standard Library. I definitelly recommend looking at ICU even if you don't plan to use it.
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2. C++11 language and library features. Still far from complete, and not easy to use.
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3. [Glib::ustring](http://www.gtkmm.org/gtkmm2/docs/tutorial/html/ch03s04.html). A class specifically made to work with UTF-8 strings, and also feel like `std::string`. If you prefer to have yet another string class in your code, it may be worth a look. Be aware of the licensing issues, though.
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4. Platform dependent solutions: Windows and POSIX have functions to convert strings from one encoding to another. That is only a subset of what my library offers, but if that is all you need it may be good enough.
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## Reference
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### Functions From utf8 Namespace
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#### utf8::append
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Available in version 3.0 and later. Requires a C++ 11 compliant compiler.
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Encodes a 32 bit code point as a UTF-8 sequence of octets and appends the sequence to a UTF-8 string.
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```cpp
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void append(char32_t cp, std::string& s);
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```
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`cp`: a code point to append to the string.
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`s`: a utf-8 encoded string to append the code point to.
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Example of use:
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```cpp
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std::string u;
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append(0x0448, u);
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assert (u[0] == char(0xd1) && u[1] == char(0x88) && u.length() == 2);
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```
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In case of an invalid code point, a `utf8::invalid_code_point` exception is thrown.
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#### utf8::append
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Available in version 1.0 and later.
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In case `start` equals `it`, a `not_enough_room` exception is thrown.
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#### utf8::previous
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Deprecated in version 1.02 and later.
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Given a reference to an iterator pointing to an octet in a UTF-8 seqence, it decreases the iterator until it hits the beginning of the previous UTF-8 encoded code point and returns the 32 bits representation of the code point.
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```cpp
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template <typename octet_iterator>
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uint32_t previous(octet_iterator& it, octet_iterator pass_start);
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```
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`octet_iterator`: a random access iterator.
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`it`: a reference pointing to an octet within a UTF-8 encoded string. After the function returns, it is decremented to point to the beginning of the previous code point.
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`pass_start`: an iterator to the point in the sequence where the search for the beginning of a code point is aborted if no result was reached. It is a safety measure to prevent passing the beginning of the string in the search for a UTF-8 lead octet.
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Return value: the 32 bit representation of the previous code point.
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Example of use:
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```cpp
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char* twochars = "\xe6\x97\xa5\xd1\x88";
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unsigned char* w = twochars + 3;
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int cp = previous (w, twochars - 1);
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assert (cp == 0x65e5);
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assert (w == twochars);
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```
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`utf8::previous` is deprecated, and `utf8::prior` should be used instead, although the existing code can continue using this function. The problem is the parameter `pass_start` that points to the position just before the beginning of the sequence. Standard containers don't have the concept of "pass start" and the function can not be used with their iterators.
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`it` will typically point to the beginning of a code point, and `pass_start` will point to the octet just before the beginning of the string to ensure we don't go backwards too far. `it` is decreased until it points to a lead UTF-8 octet, and then the UTF-8 sequence beginning with that octet is decoded to a 32 bit representation and returned.
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In case `pass_start` is reached before a UTF-8 lead octet is hit, or if an invalid UTF-8 sequence is started by the lead octet, an `invalid_utf8` exception is thrown
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#### utf8::advance
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Available in version 1.0 and later.
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`octet_iterator`: an input iterator.
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`distance_type`: an integral type convertible to `octet_iterator`'s difference type.
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`it`: a reference to an iterator pointing to the beginning of an UTF-8 encoded code point. After the function returns, it is incremented to point to the nth following code point.
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`n`: a positive integer that shows how many code points we want to advance.
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`end`: end of the UTF-8 sequence to be processed. If `it` gets equal to `end` during the extraction of a code point, an `utf8::not_enough_room` exception is thrown.
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`n`: number of code points `it` should be advanced. A negative value means decrement.
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`end`: limit of the UTF-8 sequence to be processed. If `n` is positive and `it` gets equal to `end` during the extraction of a code point, an `utf8::not_enough_room` exception is thrown. If `n` is negative and `it` reaches `end` while `it` points t a trail byte of a UTF-8 sequence, a `utf8::invalid_code_point` exception is thrown.
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Example of use:
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@ -294,10 +335,10 @@ char* twochars = "\xe6\x97\xa5\xd1\x88";
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unsigned char* w = twochars;
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advance (w, 2, twochars + 6);
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assert (w == twochars + 5);
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advance (w, -2, twochars);
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assert (w == twochars);
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```
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This function works only "forward". In case of a negative `n`, there is no effect.
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In case of an invalid code point, a `utf8::invalid_code_point` exception is thrown.
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#### utf8::distance
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@ -328,6 +369,54 @@ This function is used to find the length (in code points) of a UTF-8 encoded str
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In case of an invalid UTF-8 seqence, a `utf8::invalid_utf8` exception is thrown. If `last` does not point to the past-of-end of a UTF-8 seqence, a `utf8::not_enough_room` exception is thrown.
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#### utf8::utf16to8
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Available in version 3.0 and later. Requires a C++ 11 compliant compiler.
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Converts a UTF-16 encoded string to UTF-8.
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```cpp
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std::string utf16to8(const std::u16string& s);
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```
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`s`: a UTF-16 encoded string.
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Return value: A UTF-8 encoded string.
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Example of use:
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```cpp
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u16string utf16string = {0x41, 0x0448, 0x65e5, 0xd834, 0xdd1e};
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string u = utf16to8(utf16string);
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assert (u.size() == 10);
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```
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In case of invalid UTF-16 sequence, a `utf8::invalid_utf16` exception is thrown.
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#### utf8::utf16to8
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Available in version 3.2 and later. Requires a C++ 17 compliant compiler.
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Converts a UTF-16 encoded string to UTF-8.
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```cpp
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std::string utf16to8(std::u16string_view s);
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```
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`s`: a UTF-16 encoded string.
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Return value: A UTF-8 encoded string.
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Example of use:
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```cpp
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u16string utf16string = {0x41, 0x0448, 0x65e5, 0xd834, 0xdd1e};
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u16string_view utf16stringview(u16string);
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string u = utf16to8(utf16string);
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assert (u.size() == 10);
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```
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In case of invalid UTF-16 sequence, a `utf8::invalid_utf16` exception is thrown.
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#### utf8::utf16to8
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Available in version 1.0 and later.
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@ -357,6 +446,57 @@ assert (utf8result.size() == 10);
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In case of invalid UTF-16 sequence, a `utf8::invalid_utf16` exception is thrown.
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#### utf8::utf8to16
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Available in version 3.0 and later. Requires a C++ 11 compliant compiler.
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Converts an UTF-8 encoded string to UTF-16.
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```cpp
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std::u16string utf8to16(const std::string& s);
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```
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`s`: an UTF-8 encoded string to convert.
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Return value: A UTF-16 encoded string
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Example of use:
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```cpp
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string utf8_with_surrogates = "\xe6\x97\xa5\xd1\x88\xf0\x9d\x84\x9e";
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u16string utf16result = utf8to16(utf8_with_surrogates);
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assert (utf16result.length() == 4);
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assert (utf16result[2] == 0xd834);
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assert (utf16result[3] == 0xdd1e);
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```
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In case of an invalid UTF-8 seqence, a `utf8::invalid_utf8` exception is thrown.
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#### utf8::utf8to16
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Available in version 3.2 and later. Requires a C++ 17 compliant compiler.
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Converts an UTF-8 encoded string to UTF-16.
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```cpp
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std::u16string utf8to16(std::string_view s);
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```
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`s`: an UTF-8 encoded string to convert.
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Return value: A UTF-16 encoded string
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Example of use:
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```cpp
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string_view utf8_with_surrogates = "\xe6\x97\xa5\xd1\x88\xf0\x9d\x84\x9e";
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u16string utf16result = utf8to16(utf8_with_surrogates);
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assert (utf16result.length() == 4);
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assert (utf16result[2] == 0xd834);
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assert (utf16result[3] == 0xdd1e);
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```
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In case of an invalid UTF-8 seqence, a `utf8::invalid_utf8` exception is thrown.
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#### utf8::utf8to16
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Available in version 1.0 and later.
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@ -387,6 +527,54 @@ assert (utf16result[3] == 0xdd1e);
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In case of an invalid UTF-8 seqence, a `utf8::invalid_utf8` exception is thrown. If `end` does not point to the past-of-end of a UTF-8 seqence, a `utf8::not_enough_room` exception is thrown.
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#### utf8::utf32to8
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Available in version 3.0 and later. Requires a C++ 11 compliant compiler.
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Converts a UTF-32 encoded string to UTF-8.
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```cpp
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std::string utf32to8(const std::u32string& s);
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```
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`s`: a UTF-32 encoded string.
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Return value: a UTF-8 encoded string.
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Example of use:
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```cpp
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u32string utf32string = {0x448, 0x65E5, 0x10346};
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string utf8result = utf32to8(utf32string);
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assert (utf8result.size() == 9);
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```
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In case of invalid UTF-32 string, a `utf8::invalid_code_point` exception is thrown.
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#### utf8::utf32to8
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Available in version 3.2 and later. Requires a C++ 17 compliant compiler.
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Converts a UTF-32 encoded string to UTF-8.
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```cpp
|
||||
std::string utf32to8(std::u32string_view s);
|
||||
```
|
||||
|
||||
`s`: a UTF-32 encoded string.
|
||||
Return value: a UTF-8 encoded string.
|
||||
|
||||
Example of use:
|
||||
|
||||
```cpp
|
||||
u32string utf32string = {0x448, 0x65E5, 0x10346};
|
||||
u32string_view utf32stringview(utf32string);
|
||||
string utf8result = utf32to8(utf32stringview);
|
||||
assert (utf8result.size() == 9);
|
||||
```
|
||||
|
||||
In case of invalid UTF-32 string, a `utf8::invalid_code_point` exception is thrown.
|
||||
|
||||
|
||||
#### utf8::utf32to8
|
||||
|
||||
Available in version 1.0 and later.
|
||||
|
|
@ -407,7 +595,7 @@ Return value: An iterator pointing to the place after the appended UTF-8 string.
|
|||
|
||||
Example of use:
|
||||
|
||||
```
|
||||
```cpp
|
||||
int utf32string[] = {0x448, 0x65E5, 0x10346, 0};
|
||||
vector<unsigned char> utf8result;
|
||||
utf32to8(utf32string, utf32string + 3, back_inserter(utf8result));
|
||||
|
|
@ -416,6 +604,53 @@ assert (utf8result.size() == 9);
|
|||
|
||||
In case of invalid UTF-32 string, a `utf8::invalid_code_point` exception is thrown.
|
||||
|
||||
#### utf8::utf8to32
|
||||
|
||||
Available in version 3.0 and later. Requires a C++ 11 compliant compiler.
|
||||
|
||||
Converts a UTF-8 encoded string to UTF-32.
|
||||
|
||||
```cpp
|
||||
std::u32string utf8to32(const std::string& s);
|
||||
```
|
||||
|
||||
`s`: a UTF-8 encoded string.
|
||||
Return value: a UTF-32 encoded string.
|
||||
|
||||
Example of use:
|
||||
|
||||
```cpp
|
||||
const char* twochars = "\xe6\x97\xa5\xd1\x88";
|
||||
u32string utf32result = utf8to32(twochars);
|
||||
assert (utf32result.size() == 2);
|
||||
```
|
||||
|
||||
In case of an invalid UTF-8 seqence, a `utf8::invalid_utf8` exception is thrown.
|
||||
|
||||
#### utf8::utf8to32
|
||||
|
||||
Available in version 3.2 and later. Requires a C++ 17 compliant compiler.
|
||||
|
||||
Converts a UTF-8 encoded string to UTF-32.
|
||||
|
||||
```cpp
|
||||
std::u32string utf8to32(std::string_view s);
|
||||
```
|
||||
|
||||
`s`: a UTF-8 encoded string.
|
||||
Return value: a UTF-32 encoded string.
|
||||
|
||||
Example of use:
|
||||
|
||||
```cpp
|
||||
string_view twochars = "\xe6\x97\xa5\xd1\x88";
|
||||
u32string utf32result = utf8to32(twochars);
|
||||
assert (utf32result.size() == 2);
|
||||
```
|
||||
|
||||
In case of an invalid UTF-8 seqence, a `utf8::invalid_utf8` exception is thrown.
|
||||
|
||||
|
||||
#### utf8::utf8to32
|
||||
|
||||
Available in version 1.0 and later.
|
||||
|
|
@ -445,6 +680,53 @@ assert (utf32result.size() == 2);
|
|||
|
||||
In case of an invalid UTF-8 seqence, a `utf8::invalid_utf8` exception is thrown. If `end` does not point to the past-of-end of a UTF-8 seqence, a `utf8::not_enough_room` exception is thrown.
|
||||
|
||||
#### utf8::find_invalid
|
||||
|
||||
Available in version 3.0 and later. Requires a C++ 11 compliant compiler.
|
||||
|
||||
Detects an invalid sequence within a UTF-8 string.
|
||||
|
||||
```cpp
|
||||
std::size_t find_invalid(const std::string& s);
|
||||
```
|
||||
|
||||
`s`: a UTF-8 encoded string.
|
||||
Return value: the index of the first invalid octet in the UTF-8 string. In case none were found, equals `std::string::npos`.
|
||||
|
||||
Example of use:
|
||||
|
||||
```cpp
|
||||
string utf_invalid = "\xe6\x97\xa5\xd1\x88\xfa";
|
||||
auto invalid = find_invalid(utf_invalid);
|
||||
assert (invalid == 5);
|
||||
```
|
||||
|
||||
This function is typically used to make sure a UTF-8 string is valid before processing it with other functions. It is especially important to call it if before doing any of the _unchecked_ operations on it.
|
||||
|
||||
#### utf8::find_invalid
|
||||
|
||||
Available in version 3.2 and later. Requires a C++ 17 compliant compiler.
|
||||
|
||||
Detects an invalid sequence within a UTF-8 string.
|
||||
|
||||
```cpp
|
||||
std::size_t find_invalid(std::string_view s);
|
||||
```
|
||||
|
||||
`s`: a UTF-8 encoded string.
|
||||
Return value: the index of the first invalid octet in the UTF-8 string. In case none were found, equals `std::string_view::npos`.
|
||||
|
||||
Example of use:
|
||||
|
||||
```cpp
|
||||
string_view utf_invalid = "\xe6\x97\xa5\xd1\x88\xfa";
|
||||
auto invalid = find_invalid(utf_invalid);
|
||||
assert (invalid == 5);
|
||||
```
|
||||
|
||||
This function is typically used to make sure a UTF-8 string is valid before processing it with other functions. It is especially important to call it if before doing any of the _unchecked_ operations on it.
|
||||
|
||||
|
||||
#### utf8::find_invalid
|
||||
|
||||
Available in version 1.0 and later.
|
||||
|
|
@ -471,6 +753,53 @@ assert (invalid == utf_invalid + 5);
|
|||
|
||||
This function is typically used to make sure a UTF-8 string is valid before processing it with other functions. It is especially important to call it if before doing any of the _unchecked_ operations on it.
|
||||
|
||||
#### utf8::is_valid
|
||||
|
||||
Available in version 3.0 and later. Requires a C++ 11 compliant compiler.
|
||||
|
||||
Checks whether a string object contains valid UTF-8 encoded text.
|
||||
|
||||
```cpp
|
||||
bool is_valid(const std::string& s);
|
||||
```
|
||||
|
||||
`s`: a UTF-8 encoded string.
|
||||
Return value: `true` if the string contains valid UTF-8 encoded text; `false` if not.
|
||||
|
||||
Example of use:
|
||||
|
||||
```cpp
|
||||
char utf_invalid[] = "\xe6\x97\xa5\xd1\x88\xfa";
|
||||
bool bvalid = is_valid(utf_invalid);
|
||||
assert (bvalid == false);
|
||||
```
|
||||
|
||||
You may want to use `is_valid` to make sure that a string contains valid UTF-8 text without the need to know where it fails if it is not valid.
|
||||
|
||||
#### utf8::is_valid
|
||||
|
||||
Available in version 3.2 and later. Requires a C++ 17 compliant compiler.
|
||||
|
||||
Checks whether a string object contains valid UTF-8 encoded text.
|
||||
|
||||
```cpp
|
||||
bool is_valid(std::string_view s);
|
||||
```
|
||||
|
||||
`s`: a UTF-8 encoded string.
|
||||
Return value: `true` if the string contains valid UTF-8 encoded text; `false` if not.
|
||||
|
||||
Example of use:
|
||||
|
||||
```cpp
|
||||
string_view utf_invalid = "\xe6\x97\xa5\xd1\x88\xfa";
|
||||
bool bvalid = is_valid(utf_invalid);
|
||||
assert (bvalid == false);
|
||||
```
|
||||
|
||||
You may want to use `is_valid` to make sure that a string contains valid UTF-8 text without the need to know where it fails if it is not valid.
|
||||
|
||||
|
||||
#### utf8::is_valid
|
||||
|
||||
Available in version 1.0 and later.
|
||||
|
|
@ -497,6 +826,59 @@ assert (bvalid == false);
|
|||
|
||||
`is_valid` is a shorthand for `find_invalid(start, end) == end;`. You may want to use it to make sure that a byte seqence is a valid UTF-8 string without the need to know where it fails if it is not valid.
|
||||
|
||||
#### utf8::replace_invalid
|
||||
|
||||
Available in version 3.0 and later. Requires a C++ 11 compliant compiler.
|
||||
|
||||
Replaces all invalid UTF-8 sequences within a string with a replacement marker.
|
||||
|
||||
```cpp
|
||||
std::string replace_invalid(const std::string& s, char32_t replacement);
|
||||
std::string replace_invalid(const std::string& s);
|
||||
```
|
||||
|
||||
`s`: a UTF-8 encoded string.
|
||||
`replacement`: A Unicode code point for the replacement marker. The version without this parameter assumes the value `0xfffd`
|
||||
Return value: A UTF-8 encoded string with replaced invalid sequences.
|
||||
|
||||
Example of use:
|
||||
|
||||
```cpp
|
||||
string invalid_sequence = "a\x80\xe0\xa0\xc0\xaf\xed\xa0\x80z";
|
||||
string replace_invalid_result = replace_invalid(invalid_sequence, '?');
|
||||
bvalid = is_valid(replace_invalid_result);
|
||||
assert (bvalid);
|
||||
const string fixed_invalid_sequence = "a????z";
|
||||
assert (fixed_invalid_sequence == replace_invalid_result);
|
||||
```
|
||||
|
||||
#### utf8::replace_invalid
|
||||
|
||||
Available in version 3.2 and later. Requires a C++ 17 compliant compiler.
|
||||
|
||||
Replaces all invalid UTF-8 sequences within a string with a replacement marker.
|
||||
|
||||
```cpp
|
||||
std::string replace_invalid(std::string_view s, char32_t replacement);
|
||||
std::string replace_invalid(std::string_view s);
|
||||
```
|
||||
|
||||
`s`: a UTF-8 encoded string.
|
||||
`replacement`: A Unicode code point for the replacement marker. The version without this parameter assumes the value `0xfffd`
|
||||
Return value: A UTF-8 encoded string with replaced invalid sequences.
|
||||
|
||||
Example of use:
|
||||
|
||||
```cpp
|
||||
string_view invalid_sequence = "a\x80\xe0\xa0\xc0\xaf\xed\xa0\x80z";
|
||||
string replace_invalid_result = replace_invalid(invalid_sequence, '?');
|
||||
bool bvalid = is_valid(replace_invalid_result);
|
||||
assert (bvalid);
|
||||
const string fixed_invalid_sequence = "a????z";
|
||||
assert(fixed_invalid_sequence, replace_invalid_result);
|
||||
```
|
||||
|
||||
|
||||
#### utf8::replace_invalid
|
||||
|
||||
Available in version 2.0 and later.
|
||||
|
|
@ -532,11 +914,64 @@ assert (std::equal(replace_invalid_result.begin(), replace_invalid_result.end(),
|
|||
|
||||
`replace_invalid` does not perform in-place replacement of invalid sequences. Rather, it produces a copy of the original string with the invalid sequences replaced with a replacement marker. Therefore, `out` must not be in the `[start, end]` range.
|
||||
|
||||
If `end` does not point to the past-of-end of a UTF-8 sequence, a `utf8::not_enough_room` exception is thrown.
|
||||
#### utf8::starts_with_bom
|
||||
|
||||
Available in version 3.0 and later. Requires a C++ 11 compliant compiler.
|
||||
|
||||
Checks whether a string starts with a UTF-8 byte order mark (BOM)
|
||||
|
||||
```cpp
|
||||
bool starts_with_bom(const std::string& s);
|
||||
```
|
||||
|
||||
`s`: a UTF-8 encoded string.
|
||||
Return value: `true` if the string starts with a UTF-8 byte order mark; `false` if not.
|
||||
|
||||
Example of use:
|
||||
|
||||
```cpp
|
||||
string byte_order_mark = {char(0xef), char(0xbb), char(0xbf)};
|
||||
bool bbom = starts_with_bom(byte_order_mark);
|
||||
assert (bbom == true);
|
||||
string threechars = "\xf0\x90\x8d\x86\xe6\x97\xa5\xd1\x88";
|
||||
bool no_bbom = starts_with_bom(threechars);
|
||||
assert (no_bbom == false);
|
||||
```
|
||||
|
||||
The typical use of this function is to check the first three bytes of a file. If they form the UTF-8 BOM, we want to skip them before processing the actual UTF-8 encoded text.
|
||||
|
||||
|
||||
#### utf8::starts_with_bom
|
||||
|
||||
Available in version 2.3 and later. Relaces deprecated `is_bom()` function.
|
||||
Available in version 3.2 and later. Requires a C++ 17 compliant compiler.
|
||||
|
||||
Checks whether a string starts with a UTF-8 byte order mark (BOM)
|
||||
|
||||
```cpp
|
||||
bool starts_with_bom(std::string_view s);
|
||||
```
|
||||
|
||||
`s`: a UTF-8 encoded string.
|
||||
Return value: `true` if the string starts with a UTF-8 byte order mark; `false` if not.
|
||||
|
||||
Example of use:
|
||||
|
||||
```cpp
|
||||
string byte_order_mark = {char(0xef), char(0xbb), char(0xbf)};
|
||||
string_view byte_order_mark_view(byte_order_mark);
|
||||
bool bbom = starts_with_bom(byte_order_mark_view);
|
||||
assert (bbom);
|
||||
string_view threechars = "\xf0\x90\x8d\x86\xe6\x97\xa5\xd1\x88";
|
||||
bool no_bbom = starts_with_bom(threechars);
|
||||
assert (!no_bbom);
|
||||
```
|
||||
|
||||
The typical use of this function is to check the first three bytes of a file. If they form the UTF-8 BOM, we want to skip them before processing the actual UTF-8 encoded text.
|
||||
|
||||
|
||||
#### utf8::starts_with_bom
|
||||
|
||||
Available in version 2.3 and later.
|
||||
|
||||
Checks whether an octet sequence starts with a UTF-8 byte order mark (BOM)
|
||||
|
||||
|
|
@ -560,33 +995,6 @@ assert (bbom == true);
|
|||
|
||||
The typical use of this function is to check the first three bytes of a file. If they form the UTF-8 BOM, we want to skip them before processing the actual UTF-8 encoded text.
|
||||
|
||||
#### utf8::is_bom
|
||||
|
||||
Available in version 1.0 and later. Deprecated in version 2.3\. `starts_with_bom()` should be used instead.
|
||||
|
||||
Checks whether a sequence of three octets is a UTF-8 byte order mark (BOM)
|
||||
|
||||
```cpp
|
||||
template <typename octet_iterator>
|
||||
bool is_bom (octet_iterator it); // Deprecated
|
||||
```
|
||||
|
||||
`octet_iterator`: an input iterator.
|
||||
`it`: beginning of the 3-octet sequence to check
|
||||
Return value: `true` if the sequence is UTF-8 byte order mark; `false` if not.
|
||||
|
||||
Example of use:
|
||||
|
||||
```cpp
|
||||
unsigned char byte_order_mark[] = {0xef, 0xbb, 0xbf};
|
||||
bool bbom = is_bom(byte_order_mark);
|
||||
assert (bbom == true);
|
||||
```
|
||||
|
||||
The typical use of this function is to check the first three bytes of a file. If they form the UTF-8 BOM, we want to skip them before processing the actual UTF-8 encoded text.
|
||||
|
||||
If a sequence is shorter than three bytes, an invalid iterator will be dereferenced. Therefore, this function is deprecated in favor of `starts_with_bom()`that takes the end of sequence as an argument.
|
||||
|
||||
### Types From utf8 Namespace
|
||||
|
||||
#### utf8::exception
|
||||
|
|
@ -678,15 +1086,24 @@ class iterator;
|
|||
|
||||
##### Member functions
|
||||
|
||||
`iterator();` the deafult constructor; the underlying octet_iterator is constructed with its default constructor.
|
||||
`iterator();` the deafult constructor; the underlying octet_iterator is constructed with its default constructor.
|
||||
|
||||
`explicit iterator (const octet_iterator& octet_it, const octet_iterator& range_start, const octet_iterator& range_end);` a constructor that initializes the underlying octet_iterator with octet_it and sets the range in which the iterator is considered valid.
|
||||
|
||||
`octet_iterator base () const;` returns the underlying octet_iterator.
|
||||
|
||||
`uint32_t operator * () const;` decodes the utf-8 sequence the underlying octet_iterator is pointing to and returns the code point.
|
||||
|
||||
`bool operator == (const iterator& rhs) const;` returns `true` if the two underlaying iterators are equal.
|
||||
|
||||
`bool operator != (const iterator& rhs) const;` returns `true` if the two underlaying iterators are not equal.
|
||||
|
||||
`iterator& operator ++ ();` the prefix increment - moves the iterator to the next UTF-8 encoded code point.
|
||||
|
||||
`iterator operator ++ (int);` the postfix increment - moves the iterator to the next UTF-8 encoded code point and returns the current one.
|
||||
|
||||
`iterator& operator -- ();` the prefix decrement - moves the iterator to the previous UTF-8 encoded code point.
|
||||
|
||||
`iterator operator -- (int);` the postfix decrement - moves the iterator to the previous UTF-8 encoded code point and returns the current one.
|
||||
|
||||
Example of use:
|
||||
|
|
@ -824,34 +1241,6 @@ assert (w == twochars);
|
|||
|
||||
This is a faster but less safe version of `utf8::prior`. It does not check for validity of the supplied UTF-8 sequence and offers no boundary checking.
|
||||
|
||||
#### utf8::unchecked::previous (deprecated, see utf8::unchecked::prior)
|
||||
|
||||
Deprecated in version 1.02 and later.
|
||||
|
||||
Given a reference to an iterator pointing to an octet in a UTF-8 seqence, it decreases the iterator until it hits the beginning of the previous UTF-8 encoded code point and returns the 32 bits representation of the code point.
|
||||
|
||||
```cpp
|
||||
template <typename octet_iterator>
|
||||
uint32_t previous(octet_iterator& it);
|
||||
```
|
||||
|
||||
`it`: a reference pointing to an octet within a UTF-8 encoded string. After the function returns, it is decremented to point to the beginning of the previous code point.
|
||||
Return value: the 32 bit representation of the previous code point.
|
||||
|
||||
Example of use:
|
||||
|
||||
```cpp
|
||||
char* twochars = "\xe6\x97\xa5\xd1\x88";
|
||||
char* w = twochars + 3;
|
||||
int cp = unchecked::previous (w);
|
||||
assert (cp == 0x65e5);
|
||||
assert (w == twochars);
|
||||
```
|
||||
|
||||
The reason this function is deprecated is just the consistency with the "checked" versions, where `prior` should be used instead of `previous`. In fact, `unchecked::previous` behaves exactly the same as `unchecked::prior`
|
||||
|
||||
This is a faster but less safe version of `utf8::previous`. It does not check for validity of the supplied UTF-8 sequence and offers no boundary checking.
|
||||
|
||||
#### utf8::unchecked::advance
|
||||
|
||||
Available in version 1.0 and later.
|
||||
|
|
@ -863,8 +1252,8 @@ template <typename octet_iterator, typename distance_type>
|
|||
void advance (octet_iterator& it, distance_type n);
|
||||
```
|
||||
|
||||
`it`: a reference to an iterator pointing to the beginning of an UTF-8 encoded code point. After the function returns, it is incremented to point to the nth following code point.
|
||||
`n`: a positive integer that shows how many code points we want to advance.
|
||||
`it`: a reference to an iterator pointing to the beginning of an UTF-8 encoded code point. After the function returns, it is incremented to point to the nth following code point.
|
||||
`n`: number of code points `it` should be advanced. A negative value means decrement.
|
||||
|
||||
Example of use:
|
||||
|
||||
|
|
@ -875,8 +1264,6 @@ unchecked::advance (w, 2);
|
|||
assert (w == twochars + 5);
|
||||
```
|
||||
|
||||
This function works only "forward". In case of a negative `n`, there is no effect.
|
||||
|
||||
This is a faster but less safe version of `utf8::advance`. It does not check for validity of the supplied UTF-8 sequence and offers no boundary checking.
|
||||
|
||||
#### utf8::unchecked::distance
|
||||
|
|
@ -1013,6 +1400,43 @@ assert (utf32result.size() == 2);
|
|||
|
||||
This is a faster but less safe version of `utf8::utf8to32`. It does not check for validity of the supplied UTF-8 sequence.
|
||||
|
||||
#### utf8::unchecked::replace_invalid
|
||||
|
||||
Available in version 3.1 and later.
|
||||
|
||||
Replaces all invalid UTF-8 sequences within a string with a replacement marker.
|
||||
|
||||
```cpp
|
||||
template <typename octet_iterator, typename output_iterator>
|
||||
output_iterator replace_invalid(octet_iterator start, octet_iterator end, output_iterator out, uint32_t replacement);
|
||||
template <typename octet_iterator, typename output_iterator>
|
||||
output_iterator replace_invalid(octet_iterator start, octet_iterator end, output_iterator out);
|
||||
```
|
||||
|
||||
`octet_iterator`: an input iterator.
|
||||
`output_iterator`: an output iterator.
|
||||
`start`: an iterator pointing to the beginning of the UTF-8 string to look for invalid UTF-8 sequences.
|
||||
`end`: an iterator pointing to pass-the-end of the UTF-8 string to look for invalid UTF-8 sequences.
|
||||
`out`: An output iterator to the range where the result of replacement is stored.
|
||||
`replacement`: A Unicode code point for the replacement marker. The version without this parameter assumes the value `0xfffd`
|
||||
Return value: An iterator pointing to the place after the UTF-8 string with replaced invalid sequences.
|
||||
|
||||
Example of use:
|
||||
|
||||
```cpp
|
||||
char invalid_sequence[] = "a\x80\xe0\xa0\xc0\xaf\xed\xa0\x80z";
|
||||
vector<char> replace_invalid_result;
|
||||
unchecked::replace_invalid (invalid_sequence, invalid_sequence + sizeof(invalid_sequence), back_inserter(replace_invalid_result), '?');
|
||||
bvalid = utf8::is_valid(replace_invalid_result.begin(), replace_invalid_result.end());
|
||||
assert (bvalid);
|
||||
char* fixed_invalid_sequence = "a????z";
|
||||
assert (std::equal(replace_invalid_result.begin(), replace_invalid_result.end(), fixed_invalid_sequence));
|
||||
```
|
||||
|
||||
`replace_invalid` does not perform in-place replacement of invalid sequences. Rather, it produces a copy of the original string with the invalid sequences replaced with a replacement marker. Therefore, `out` must not be in the `[start, end]` range.
|
||||
|
||||
Unlike `utf8::replace_invalid`, this function does not verify validity of the replacement marker.
|
||||
|
||||
### Types From utf8::unchecked Namespace
|
||||
|
||||
#### utf8::iterator
|
||||
|
|
@ -1029,14 +1453,23 @@ class iterator;
|
|||
##### Member functions
|
||||
|
||||
`iterator();` the deafult constructor; the underlying octet_iterator is constructed with its default constructor.
|
||||
`explicit iterator (const octet_iterator& octet_it);` a constructor that initializes the underlying octet_iterator with `octet_it`
|
||||
|
||||
`explicit iterator (const octet_iterator& octet_it);` a constructor that initializes the underlying octet_iterator with `octet_it`.
|
||||
|
||||
`octet_iterator base () const;` returns the underlying octet_iterator.
|
||||
|
||||
`uint32_t operator * () const;` decodes the utf-8 sequence the underlying octet_iterator is pointing to and returns the code point.
|
||||
|
||||
`bool operator == (const iterator& rhs) const;` returns `true` if the two underlaying iterators are equal.
|
||||
|
||||
`bool operator != (const iterator& rhs) const;` returns `true` if the two underlaying iterators are not equal.
|
||||
|
||||
`iterator& operator ++ ();` the prefix increment - moves the iterator to the next UTF-8 encoded code point.
|
||||
|
||||
`iterator operator ++ (int);` the postfix increment - moves the iterator to the next UTF-8 encoded code point and returns the current one.
|
||||
|
||||
`iterator& operator -- ();` the prefix decrement - moves the iterator to the previous UTF-8 encoded code point.
|
||||
|
||||
`iterator operator -- (int);` the postfix decrement - moves the iterator to the previous UTF-8 encoded code point and returns the current one.
|
||||
|
||||
Example of use:
|
||||
|
|
@ -1062,26 +1495,6 @@ assert (*un_it == 0x10346);
|
|||
|
||||
This is an unchecked version of `utf8::iterator`. It is faster in many cases, but offers no validity or range checks.
|
||||
|
||||
## Points of interest
|
||||
|
||||
#### Design goals and decisions
|
||||
|
||||
The library was designed to be:
|
||||
|
||||
1. Generic: for better or worse, there are many C++ string classes out there, and the library should work with as many of them as possible.
|
||||
2. Portable: the library should be portable both accross different platforms and compilers. The only non-portable code is a small section that declares unsigned integers of different sizes: three typedefs. They can be changed by the users of the library if they don't match their platform. The default setting should work for Windows (both 32 and 64 bit), and most 32 bit and 64 bit Unix derivatives. At this point I don't plan to use any post C++03 features, so the library should work even with pretty old compilers.
|
||||
3. Lightweight: follow the "pay only for what you use" guideline.
|
||||
4. Unintrusive: avoid forcing any particular design or even programming style on the user. This is a library, not a framework.
|
||||
|
||||
#### Alternatives
|
||||
|
||||
In case you want to look into other means of working with UTF-8 strings from C++, here is the list of solutions I am aware of:
|
||||
|
||||
1. [ICU Library](http://icu.sourceforge.net/). It is very powerful, complete, feature-rich, mature, and widely used. Also big, intrusive, non-generic, and doesn't play well with the Standard Library. I definitelly recommend looking at ICU even if you don't plan to use it.
|
||||
2. C++11 language and library features. Still far from complete, and not easy to use.
|
||||
3. [Glib::ustring](http://www.gtkmm.org/gtkmm2/docs/tutorial/html/ch03s04.html). A class specifically made to work with UTF-8 strings, and also feel like `std::string`. If you prefer to have yet another string class in your code, it may be worth a look. Be aware of the licensing issues, though.
|
||||
4. Platform dependent solutions: Windows and POSIX have functions to convert strings from one encoding to another. That is only a subset of what my library offers, but if that is all you need it may be good enough.
|
||||
|
||||
## Links
|
||||
|
||||
1. [The Unicode Consortium](http://www.unicode.org/).
|
||||
|
|
|
|||
Loading…
Add table
Add a link
Reference in a new issue