| 1 | #
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| 2 | ! This file contains two specialized assembly code routines to update the
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| 3 | ! video memory. The routines can copy from user to video memory, or from
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| 4 | ! video to video memory.
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| 5 |
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| 6 | ! sections
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| 7 |
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| 8 | .sect .text; .sect .rom; .sect .data; .sect .bss
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| 9 |
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| 10 | ! exported functions
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| 11 |
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| 12 | .define _mem_vid_copy ! copy data to video ram
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| 13 | .define _vid_vid_copy ! move data in video ram
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| 14 |
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| 15 | ! The routines only guarantee to preserve the registers the C compiler
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| 16 | ! expects to be preserved (ebx, esi, edi, ebp, esp, segment registers, and
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| 17 | ! direction bit in the flags).
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| 18 |
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| 19 | .sect .text
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| 20 | !*===========================================================================*
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| 21 | !* mem_vid_copy *
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| 22 | !*===========================================================================*
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| 23 | ! PUBLIC void mem_vid_copy(u16 *src, unsigned dst, unsigned count);
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| 24 | !
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| 25 | ! Copy count characters from kernel memory to video memory. Src is an ordinary
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| 26 | ! pointer to a word, but dst and count are character (word) based video offset
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| 27 | ! and count. If src is null then screen memory is blanked by filling it with
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| 28 | ! blank_color.
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| 29 |
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| 30 | _mem_vid_copy:
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| 31 | push ebp
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| 32 | mov ebp, esp
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| 33 | push esi
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| 34 | push edi
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| 35 | push es
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| 36 | mov esi, 8(ebp) ! source
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| 37 | mov edi, 12(ebp) ! destination
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| 38 | mov edx, 16(ebp) ! count
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| 39 | mov es, (_vid_seg) ! segment containing video memory
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| 40 | cld ! make sure direction is up
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| 41 | mvc_loop:
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| 42 | and edi, (_vid_mask) ! wrap address
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| 43 | mov ecx, edx ! one chunk to copy
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| 44 | mov eax, (_vid_size)
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| 45 | sub eax, edi
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| 46 | cmp ecx, eax
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| 47 | jbe 0f
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| 48 | mov ecx, eax ! ecx = min(ecx, vid_size - edi)
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| 49 | 0: sub edx, ecx ! count -= ecx
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| 50 | shl edi, 1 ! byte address
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| 51 | add edi, (_vid_off) ! in video memory
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| 52 | test esi, esi ! source == 0 means blank the screen
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| 53 | jz mvc_blank
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| 54 | mvc_copy:
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| 55 | rep ! copy words to video memory
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| 56 | o16 movs
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| 57 | jmp mvc_test
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| 58 | mvc_blank:
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| 59 | mov eax, (_blank_color) ! ax = blanking character
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| 60 | rep
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| 61 | o16 stos ! copy blanks to video memory
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| 62 | !jmp mvc_test
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| 63 | mvc_test:
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| 64 | sub edi, (_vid_off)
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| 65 | shr edi, 1 ! back to a word address
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| 66 | test edx, edx
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| 67 | jnz mvc_loop
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| 68 | mvc_done:
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| 69 | pop es
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| 70 | pop edi
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| 71 | pop esi
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| 72 | pop ebp
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| 73 | ret
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| 74 |
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| 75 |
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| 76 | !*===========================================================================*
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| 77 | !* vid_vid_copy *
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| 78 | !*===========================================================================*
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| 79 | ! PUBLIC void vid_vid_copy(unsigned src, unsigned dst, unsigned count);
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| 80 | !
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| 81 | ! Copy count characters from video memory to video memory. Handle overlap.
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| 82 | ! Used for scrolling, line or character insertion and deletion. Src, dst
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| 83 | ! and count are character (word) based video offsets and count.
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| 84 |
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| 85 | _vid_vid_copy:
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| 86 | push ebp
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| 87 | mov ebp, esp
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| 88 | push esi
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| 89 | push edi
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| 90 | push es
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| 91 | mov esi, 8(ebp) ! source
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| 92 | mov edi, 12(ebp) ! destination
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| 93 | mov edx, 16(ebp) ! count
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| 94 | mov es, (_vid_seg) ! segment containing video memory
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| 95 | cmp esi, edi ! copy up or down?
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| 96 | jb vvc_down
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| 97 | vvc_up:
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| 98 | cld ! direction is up
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| 99 | vvc_uploop:
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| 100 | and esi, (_vid_mask) ! wrap addresses
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| 101 | and edi, (_vid_mask)
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| 102 | mov ecx, edx ! one chunk to copy
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| 103 | mov eax, (_vid_size)
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| 104 | sub eax, esi
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| 105 | cmp ecx, eax
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| 106 | jbe 0f
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| 107 | mov ecx, eax ! ecx = min(ecx, vid_size - esi)
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| 108 | 0: mov eax, (_vid_size)
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| 109 | sub eax, edi
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| 110 | cmp ecx, eax
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| 111 | jbe 0f
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| 112 | mov ecx, eax ! ecx = min(ecx, vid_size - edi)
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| 113 | 0: sub edx, ecx ! count -= ecx
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| 114 | call vvc_copy ! copy video words
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| 115 | test edx, edx
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| 116 | jnz vvc_uploop ! again?
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| 117 | jmp vvc_done
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| 118 | vvc_down:
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| 119 | std ! direction is down
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| 120 | lea esi, -1(esi)(edx*1) ! start copying at the top
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| 121 | lea edi, -1(edi)(edx*1)
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| 122 | vvc_downloop:
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| 123 | and esi, (_vid_mask) ! wrap addresses
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| 124 | and edi, (_vid_mask)
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| 125 | mov ecx, edx ! one chunk to copy
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| 126 | lea eax, 1(esi)
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| 127 | cmp ecx, eax
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| 128 | jbe 0f
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| 129 | mov ecx, eax ! ecx = min(ecx, esi + 1)
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| 130 | 0: lea eax, 1(edi)
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| 131 | cmp ecx, eax
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| 132 | jbe 0f
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| 133 | mov ecx, eax ! ecx = min(ecx, edi + 1)
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| 134 | 0: sub edx, ecx ! count -= ecx
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| 135 | call vvc_copy
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| 136 | test edx, edx
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| 137 | jnz vvc_downloop ! again?
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| 138 | cld ! C compiler expects up
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| 139 | !jmp vvc_done
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| 140 | vvc_done:
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| 141 | pop es
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| 142 | pop edi
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| 143 | pop esi
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| 144 | pop ebp
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| 145 | ret
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| 146 |
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| 147 | ! Copy video words. (Inner code of both the up and downcopying loop.)
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| 148 | vvc_copy:
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| 149 | shl esi, 1
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| 150 | shl edi, 1 ! byte addresses
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| 151 | add esi, (_vid_off)
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| 152 | add edi, (_vid_off) ! in video memory
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| 153 | rep
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| 154 | eseg o16 movs ! copy video words
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| 155 | sub esi, (_vid_off)
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| 156 | sub edi, (_vid_off)
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| 157 | shr esi, 1
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| 158 | shr edi, 1 ! back to word addresses
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| 159 | ret
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| 160 |
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