; =============================================================================
; VBoxGuest Driver for KolibriOS - Common Utilities
; Файл: common/utils.inc
; =============================================================================

; sf_utf8_to_cp866 — Конвертировать UTF-8 строку в CP866 (кириллица)
proc sf_utf8_to_cp866 uses ebx ecx edx esi edi, src:dword, dst:dword, src_len:dword
    mov esi, [src]
    mov edi, [dst]
    mov ecx, [src_len]
    xor edx, edx

.u8_loop:
    test ecx, ecx
    jle .u8_done

    movzx eax, byte [esi]

    cmp al, 0x80
    jb .u8_ascii

    cmp al, 0xC0
    jb .u8_skip1
    cmp al, 0xE0
    jb .u8_two_byte

    cmp al, 0xF0
    jb .u8_skip3

    mov byte [edi], '?'
    inc edi
    inc edx
    add esi, 4
    sub ecx, 4
    jmp .u8_loop

.u8_skip3:
    mov byte [edi], '?'
    inc edi
    inc edx
    add esi, 3
    sub ecx, 3
    jmp .u8_loop

.u8_ascii:
    mov [edi], al
    inc esi
    inc edi
    inc edx
    dec ecx
    jmp .u8_loop

.u8_two_byte:
    cmp ecx, 2
    jb .u8_done

    movzx eax, byte [esi]
    movzx ebx, byte [esi + 1]
    and eax, 0x1F
    shl eax, 6
    and ebx, 0x3F
    or eax, ebx

    cmp eax, 0x0401
    je .u8_yo_upper
    cmp eax, 0x0451
    je .u8_yo_lower

    cmp eax, 0x0410
    jb .u8_not_cyrillic
    cmp eax, 0x041F
    jbe .u8_upper1

    cmp eax, 0x042F
    jbe .u8_upper2

    cmp eax, 0x043F
    jbe .u8_lower1

    cmp eax, 0x044F
    jbe .u8_lower2

    jmp .u8_not_cyrillic

.u8_upper1:
    sub eax, 0x0410
    add eax, 0x80
    jmp .u8_store2

.u8_upper2:
    sub eax, 0x0420
    add eax, 0x90
    jmp .u8_store2

.u8_lower1:
    sub eax, 0x0430
    add eax, 0xA0
    jmp .u8_store2

.u8_lower2:
    sub eax, 0x0440
    add eax, 0xE0
    jmp .u8_store2

.u8_yo_upper:
    mov eax, 0xF0
    jmp .u8_store2

.u8_yo_lower:
    mov eax, 0xF1
    jmp .u8_store2

.u8_not_cyrillic:
    mov eax, '?'

.u8_store2:
    mov [edi], al
    add esi, 2
    sub ecx, 2
    inc edi
    inc edx
    jmp .u8_loop

.u8_skip1:
    inc esi
    dec ecx
    jmp .u8_loop

.u8_done:
    mov byte [edi], 0
    mov eax, edx
    ret
endp