MB ElementCount

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Synopsis

Header: fxcg/system.h
Syscall index: 0x1163
Function signature: int MB_ElementCount(const char* buf)

Counts the number of characters, as printed on screen, of a multi-byte string.

Parameters

  • buf - pointer to the string to measure.

Returns

The number of characters in the string, as printed by multi-byte-aware syscalls.

Comments

Here is a disassembly of the function.

! =============== S U B	R O U T	I N E =======================================


MB_ElementCount:
		tst	r4, r4		! Is r4	NULL?
		bt	MB_ElementCount_exit ! If yes, branch.
		mov	#0xFFFFFFE5, r1
		mov	#0xFFFFFFE6, r7
		extu.b	r1, r1		! r1=229
		mov	#0, r5
		bra	loc_801A3478
		extu.b	r7, r7		! r7=230
! ---------------------------------------------------------------------------

MB_ElementCount_charLoop:
		cmp/eq	#0x7F, r0
		bt	loc_801A3472
		cmp/eq	r1, r0
		bt	loc_801A3472
		cmp/eq	r7, r0
		bt	loc_801A3472
		mov	#0xFFFFFFE7, r2
		extu.b	r2, r2
		cmp/eq	r2, r0
		bt	loc_801A3472
		mov	#0xFFFFFFF7, r2
		extu.b	r2, r2
		cmp/eq	r2, r0
		bt	loc_801A3472
		mov	#0xFFFFFFF9, r2
		extu.b	r2, r2
		cmp/eq	r2, r0
		bf	loc_801A3474

loc_801A3472:
		add	#1, r4

loc_801A3474:
		add	#1, r4
		add	#1, r5

loc_801A3478:
		mov.b	@r4, r2
		extu.b	r2, r0
		tst	r0, r0
		bf	MB_ElementCount_charLoop ! Branch if the character has a non-zero value.
		rts
		mov	r5, r0
! ---------------------------------------------------------------------------

MB_ElementCount_exit:
		rts
		mov	#0, r0
! End of function MB_ElementCount

Example

The following example shows how a multi-byte string can take a memory space that's twice as large as the number of printed characters, and demonstrates how to count both size in bytes and graphical size:

const char*MBstring="\xe6\x92\xe6\x93\xe6\xa5"
int bytelen = strlen(MBstring);
// bytelen has a value of 6
int elemlen = MB_ElementCount(MBstring);
// elemlen has a value of 3

locate_OS(2,3);
Print_OS(MBstring, 0, 0); // will print three symbols on screen: an arrow up, an arrow down and a square.

Another example, which mixes standard and multi-byte characters:

const char*MBstring="Empty box: \xe6\xa5";
int bytelen = strlen(MBstring);
// bytelen has a value of 13
int elemlen = MB_ElementCount(MBstring);
// elemlen has a value of 12

locate_OS(2,3);
Print_OS(MBstring, 0, 0); // will print "Empty box: " followed by a square.