| /************************************************* |
| * libucp - Unicode Property Table handler * |
| *************************************************/ |
| |
| /* Internal header file defining the layout of compact nodes in the tree. */ |
| |
| typedef struct cnode { |
| unsigned short int f0; |
| unsigned short int f1; |
| unsigned short int f2; |
| } cnode; |
| |
| /* Things for the f0 field */ |
| |
| #define f0_leftexists 0x8000 /* Left child exists */ |
| #define f0_typemask 0x3f00 /* Type bits */ |
| #define f0_typeshift 8 /* Type shift */ |
| #define f0_chhmask 0x00ff /* Character high bits */ |
| |
| /* Things for the f2 field */ |
| |
| #define f2_rightmask 0xf000 /* Mask for right offset bits */ |
| #define f2_rightshift 12 /* Shift for right offset */ |
| #define f2_casemask 0x0fff /* Mask for case offset */ |
| |
| /* The tree consists of a vector of structures of type cnode, with the root |
| node as the first element. The three short ints (16-bits) are used as follows: |
| |
| (f0) (1) The 0x8000 bit of f0 is set if a left child exists. The child's node |
| is the next node in the vector. |
| (2) The 0x4000 bits of f0 is spare. |
| (3) The 0x3f00 bits of f0 contain the character type; this is a number |
| defined by the enumeration in ucp.h (e.g. ucp_Lu). |
| (4) The bottom 8 bits of f0 contain the most significant byte of the |
| character's 24-bit codepoint. |
| |
| (f1) (1) The f1 field contains the two least significant bytes of the |
| codepoint. |
| |
| (f2) (1) The 0xf000 bits of f2 contain zero if there is no right child of this |
| node. Otherwise, they contain one plus the exponent of the power of |
| two of the offset to the right node (e.g. a value of 3 means 8). The |
| units of the offset are node items. |
| |
| (2) The 0x0fff bits of f2 contain the signed offset from this character to |
| its alternate cased value. They are zero if there is no such |
| character. |
| |
| |
| ----------------------------------------------------------------------------- |
| ||.|.| type (6) | ms char (8) || ls char (16) ||....| case offset (12) || |
| ----------------------------------------------------------------------------- |
| | | | |
| | |-> spare | |
| | exponent of right |
| |-> left child exists child offset |
| |
| |
| The upper/lower casing information is set only for characters that come in |
| pairs. There are (at present) four non-one-to-one mappings in the Unicode data. |
| These are ignored. They are: |
| |
| 1FBE Greek Prosgegrammeni (lower, with upper -> capital iota) |
| 2126 Ohm |
| 212A Kelvin |
| 212B Angstrom |
| |
| Certainly for the last three, having an alternate case would seem to be a |
| mistake. I don't know any Greek, so cannot comment on the first one. |
| |
| |
| When searching the tree, proceed as follows: |
| |
| (1) Start at the first node. |
| |
| (2) Extract the character value from f1 and the bottom 8 bits of f0; |
| |
| (3) Compare with the character being sought. If equal, we are done. |
| |
| (4) If the test character is smaller, inspect the f0_leftexists flag. If it is |
| not set, the character is not in the tree. If it is set, move to the next |
| node, and go to (2). |
| |
| (5) If the test character is bigger, extract the f2_rightmask bits from f2, and |
| shift them right by f2_rightshift. If the result is zero, the character is |
| not in the tree. Otherwise, calculate the number of nodes to skip by |
| shifting the value 1 left by this number minus one. Go to (2). |
| */ |
| |
| |
| /* End of internal.h */ |
