hb_memory_mode_t

Data type holding the memory modes available to client programs.

Regarding these various memory-modes:

• In no case shall the HarfBuzz client modify memory that is passed to HarfBuzz in a blob. If there is any such possibility, @HB_MEMORY_MODE_DUPLICATE should be used such that HarfBuzz makes a copy immediately,
• Use @HB_MEMORY_MODE_READONLY otherwise, unless you really really really know what you are doing,
• @HB_MEMORY_MODE_WRITABLE is appropriate if you really made a copy of data solely for the purpose of passing to HarfBuzz and doing that just once (no reuse!),
• If the font is mmap()ed, it's okay to use @HB_MEMORY_MODE_READONLY_MAY_MAKE_WRITABLE, however, using that mode correctly is very tricky. Use @HB_MEMORY_MODE_READONLY instead.