Pikchr

How To Integrate Pikchr Into New Systems
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Pikchr is (currently) implemented in C.

Any existing Markdown or other wiki rendering engine that can invoke a C-language library should be able to integrate Pikchr quickly and easily. The code has been audited and fuzzed and is believed to be impervious to hostile inputs.

C-language interface.

There is a single interface function:

  char *pikchr(
    const char *zText,     /* Input PIKCHR source text.  zero-terminated */
    const char *zClass,    /* Add class="%s" to <svg> markup */
    unsigned int mFlags,   /* Flags used to influence rendering behavior */
    int *pnWidth,          /* Write width of <svg> here, if not NULL */
    int *pnHeight          /* Write height here, if not NULL */
  );

To convert Pikchr into SVG text ready to be inserted into the HTML output stream, simply invoke the pikchr() function, passing the source text as the first argument. The SVG output text is returned, and the desired width and height of that text is written into the *pnWidth and *pnHeight variables.

If the input Pikchr text contains errors, a negative number is written into *pnWidth and the returned text is an error message ready to be dropped into "<pre>...</pre>". Any "<" or ">" or "&" characters in the error message text have already been escaped, so the error message can be inserted directly into an HTML output stream without further processing.

The returned string is held in memory obtained from malloc(). The caller is responsible for freeing this memory to prevent a memory leak. It is possible (though unlikely) for pikchr() to return a NULL pointer, for example if it hits a malloc() failure.

If the zClass parameter is not NULL, then it is an extra class name (or names) that is inserted into the "<svg>" element of the returned string. The mFlags parameter is currently unused. Leave it at zero.

Example use of pikchr()

The "pikchr.c" source file itself contains an example use of the pikchr() function. If "pikchr.c" is compiled with the -DPIKCHR_SHELL compile-time option, it will include a main() that reads all the files named as arguments, runs each through pikchr() and outputs the result embedded in HTML. So if you want an example, look at the "main()" function at the bottom of the "pikchr.c" source file.

Performance considerations

Pikchr seems to use about 650 CPU cycles per byte of input. So even a slow core can handle on the order of 3 or 4 megabytes of Pikchr input per second. As most Pikchr scripts are less than 1000 bytes, the processing overhead of running Pikchr is likely to be too small to measure. Pikchr could perhaps be optimized to increase its performance, but it is so fast already (especially compared to the rest of the Markdown formatting stream) that we don't see any point in that. Contact the developers if you uncover evidence that contradicts anything in this paragraph.

Fuzz Testing

You can build a libFuzzer-based fuzz tester for Pikchr by compiling like this (or similarly):

   clang -g -O3 -fsanitize=fuzzer,undefined,address -o fuzz -DPIKCHR_FUZZ pikchr.c

Gather a bunch of Pikchr scripts to be used as seeds (perhaps from the tests/ or examples/ subdirectories of the source tree) and put them in a subdirectory, which we will call "fz". Then run:

   fuzz fz

We have run this for hundreds of millions of tests already. You are welcomed to run more.