The signature prefix for a module.
The signature of a module is a set of prefixes. Prefixes are encoded as pairs of ordinary strings, where the second string, called the mask, if not `NULL`, must be of the same length as the first one and may contain ' ', '!', 'x', 'z', and 'n' to indicate bytes that must be matched, not matched, "don't-care"-bytes, zeros and non-zeros, respectively.
Each prefix has an associated integer that describes the relevance of the prefix, with 0 meaning a mismatch and 100 a "perfect match".
Starting with gdk-pixbuf 2.8, the first byte of the mask may be '*', indicating an unanchored pattern that matches not only at the beginning, but also in the middle. Versions prior to 2.8 will interpret the '*' like an 'x'.
The signature of a module is stored as an array of `GdkPixbufModulePatterns`. The array is terminated by a pattern where the `prefix` is `NULL`.
```c GdkPixbufModulePattern *signature[] = { { "abcdx", " !x z", 100 }, { "bla", NULL, 90 }, { NULL, NULL, 0 } }; ```
In the example above, the signature matches e.g. "auud\0" with relevance 100, and "blau" with relevance 90.