Porting: UTF-8

With the mod kit and steam workshop out there, I’ve been working on porting the game to OSX and Linux, cleaning up code, and writing some new code. I’ll still be fixing bugs and making small changes, but my focus now is going to be on ports, and building prototypes for new games.

I’ve built a new machine for developing on Linux, and bought some Mac’s, so I’m all set with hardware. And it’s been a while since I used makefiles, other IDEs, gcc/clang, or did any sort of *nix development, but I have done it so I’m not starting from ground zero.

But before I can actually go about working on the new hardware and compiling things, there are a few issues in the Banished code base that need fixing. I planned on porting the code base one day, so things are nicely setup into common code and platform specific code, but there are still some issues I didn’t properly account for.

There’s code portability issues. I want to make the code as portable as possible – there’s a chance I’ll be making games for more than just Windows, Mac, and Linux one day, so I might as well try to fix them now.

The first issue is with text.

When I wrote the code I assumed one day it would support more than just English. Back when I made console games I never worked on any of the text code, so all I really knew is that the system used two bytes per character in a string of text, and this was fine for all the languages that the game was translated into – generally EFIGS and maybe Japanese. Since windows API takes wchar_t for all filenames and text, that’s what I used, and I happily and naively coded away using wide strings. This probably would be okay if the game stayed on Windows.

But it’s sort of mistake for cross-platform code. I didn’t even use it correctly. The released game doesn’t currently use UTF-16, it’s just UCS-2, so there are some languages that have characters that are unrepresentable.

Not only that, but API calls on other systems generally don’t take wchar_t*, they take char* instead. Certainly I could make conversion functions and convert UCS-2 to UTF-8 as needed, but that’s not really ideal.

The final problem is that the size of wchar_t on Windows is 2 bytes, but this isn’t guaranteed to be the case on other platforms. The size issue shouldn’t really matter – but it’s possible somewhere I multiplied a string length by 2, instead of multiplying by sizeof(wchar_t); That would cause problems.

I’ve known about these issues for a while, but I generally code something that works first, and don’t refactor until I have to. And now I have to.

So my big fix recently was to remove the use of wchar_t and use char instead. (And make sure there’s no multiplies by 2). Not only that but all strings need to use UTF8 properly – when printing text, or reading text from resource files the right thing needs to be done to properly decode and show the right character.

The first step of doing this is easy. You can find and replace a bunch of stuff using a text editor.

wchar_t becomes char

L”string” becomes “string”

wsprintf(buffer, “%ls”, param) becomes sprintf(buffer, “%s”, param)

wcscpy, wcslen, wcscat becomes strcpy, strlen, strcat

Next I fixed my String class to properly use char. No big deal.

All the serialization code that previously written to serialize wchar_t became serialization of char. This conflicted with serialization of single byte signed values, which were already typed as char.

For example

void Serialize(char v); // serialize a signed 8 bit value void Serialize(unsigned char v); // serialize a unsigned 8 bit value void Serialize(wchar_t v); // serialize a character

Became

void Serialize(signed char v); // this looks ambiguous to me, because i think void Serialize(unsigned char v); // of 'char' as signed, even though it's void Serialize(char v); // compiler dependent and compiles ok...

This prompted me to redeclare all integers with typedefs and make a distinction between a character and an 8-bit integer.

signed int became int32

unsigned int became uint32

signed short became int16

unsigned short became uint16

signed char became int8

unsigned char because uint8

char stays the same, and is only used for characters and strings.

int64 and uint64 were already typedef’d. These typedefs are made in platform code, so per platform types can be declared using the right sizes, regardless of their names on each platform.

So the overloads then became

void Serialize(int8 v); // serialize a signed 8 bit value void Serialize(uint8 v); // serialize an unsigned 8 bit value void Serialize(char v); // serialize a character

This took care of the type conflict since the compiler treats ‘signed char‘ as a different type than ‘char‘. It also clarifies what the types are used for in the code. If I see a char in code, it means character, or char* means null terminated string. If you see int8 or uint8, it’s a number stored as 8 bits. This makes things a bit more clear.

This was also a big find and replace, except for char, which I had to go through and determine if they were int8, or actually ascii characters. This wasn’t too hard though, as most previous uses of text used wchar_t – so most char‘s became int8. I’ll probably take a few weeks getting used to typing int32 instead of just int.

One issue that came up with the type name change was the existing source data. If you’ve been modding the game, in the data you might see

int _value = 400;

with the new code, it would become

int32 _value = 400;

While I could version all the text data, I don’t really want to break peoples mods that they’ve already setup and have to do the find and replace on their own, so there’s some versioning code that reads the old typename. For the next game I’ll get rid of that versioning code, but it’s going to stay in Banished for now.

Next came the hard part. Input data could be in any format – generally text files would be in Ascii if I create them, or UTF8 I used a symbol like the Euro. But mod creators and translated strings could be in UTF8, UTF8 with a byte order mark, or UTF16 big-endian, or UTF16 little-endian. Really it shouldn’t matter what a mod creator uses as a text format – I just want the game to load it and do the right thing.

While there are libraries for dealing with this, I tend to write my own code since I don’t like different code styles mixed in my code, type conflicts, and dealing with crazy code licenses. So 400 or so lines of code later and lots of debugging I wrote two great functions. One detects character encoding using byte order marks and checking for valid UTF8. The other can convert any one text encoding to another. There’s also support functions for decoding strings one character at a time.

After that it was a simple matter to convert all text files to UTF8 as they are opened by the game engine.

Once I had all UTF8 strings in memory, they have to be decoded when used as output – the font rendering code now decodes UTF8 into actual characters using 1 to 4 bytes of a string at a time before looking up each glyph in the font texture.

The Windows API can be compiled to use either wide strings or not, but I left them as wide and made a WideString class to deal with the conversion to and from the internal UTF8 String format. The WideString class only exists on windows compilations, and is only used in files that would be rewritten per platform anyway.

After all that, the game compiled and ran just fine, but it wouldn’t load old data or save games. This is bad. I can’t go breaking save games when a new version comes out. And I’d like to keep all existing mods working.

So then I had to version old strings that are stored in saves and data on disk – strings are just written as an int32 length, followed by all the bytes of data. So new strings set the high bit on the length to mark it as the new version. I doubt that the game will have a string of text 4 gigabytes long so this will be okay. If an old string is detected when the high bit unset, it converts it from UCS-2 to UTF-8 on load, and the game happily continues loading older data.

Again this versioning code will hopefully go away when I make another game, since it won’t be needed.

So now the only wchar_t that exists is in platform code on Windows that won’t be compiled on OSX or Linux, and the game properly supports various character encodings.

Text encodings are one of those things I never really want to think about – and now that I’ve spent a while dealing with it, hopefully I never have to deal with it again. Phew.