133 lines
2.6 KiB
NASM
133 lines
2.6 KiB
NASM
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; overlay framebuffer vfs stream routines
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overlay_vfs_stream_name: data.strz "ofb"
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; open an overlay framebuffer stream
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; inputs:
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; r0: pointer to null-terminated string "ofbXX" where XX is 0 - 31
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; r2: file struct: pointer to a blank file struct (stream)
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; outputs:
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; r0: non-zero
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open_stream_ofb:
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push r1
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push r2
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add r0, 3
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mov r1, 10
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call string_to_int
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mov.8 [r2], r0 ; write file_overlay
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inc r2
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mov.16 [r2], 0 ; write file_reserved_2
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add r2, 2
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mov [r2], 0 ; write file_seek_offset
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add r2, 4
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mov.8 [r2], 1 ; write file_system_type
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inc r2
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mov [r2], ofb_stream_read ; write file_read_call
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add r2, 4
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mov [r2], ofb_stream_write ; write file_write_call
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add r2, 4
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or r0, 0x80000100
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in r0, r0
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mov r1, r0
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srl r1, 16
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mul r1, r0
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mov [r2], r1 ; write file_size
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add r2, 4
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mov [r2], 0 ; write file_reserved_3
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add r2, 4
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mov [r2], 0 ; write file_reserved_4
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add r2, 4
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mov [r2], 0 ; write file_reserved_5
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pop r2
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pop r1
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mov r0, 1
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ret
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; read a byte from an overlay framebuffer
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; inputs:
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; r0: seek offset
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; r1: pointer to file struct + 8
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; outputs:
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; r0: byte
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ofb_stream_read:
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push r1
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push r2
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; get overlay framebuffer pointer in r2
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sub r1, 8 ; point to file_overlay (file_reserved_1)
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movz.8 r1, [r1]
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or r1, 0x80000200
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in r2, r1
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; get overlay size in r1
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sub r1, 0x100
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in r1, r1
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push r0
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mov r0, r1
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srl r0, 16
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and r1, 0x0000FFFF
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mul r1, r0
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mul r0, 4
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pop r0
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; ensure the seek offset is less than the overlay size
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cmp r0, r1
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ifgteq mov r0, r1
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ifgteq dec r0
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; fetch the byte
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add r0, r2
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movz.8 r0, [r0]
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pop r2
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pop r1
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ret
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; write a byte to an overlay framebuffer
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; inputs:
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; r0: pointer to source buffer
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; r1: seek offset
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; r3: pointer to file struct + 12
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; outputs:
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; none
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ofb_stream_write:
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push r1
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push r2
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push r3
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push r4
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; get overlay framebuffer pointer in r2
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sub r3, 12 ; point to file_overlay (file_reserved_1)
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movz.8 r3, [r3]
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or r3, 0x80000200
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in r2, r3
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; get overlay size in r4
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sub r3, 0x100
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in r4, r3
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push r0
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mov r0, r4
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srl r0, 16
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and r4, 0x0000FFFF
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mul r4, r0
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mul r4, 4
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pop r0
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; ensure the seek offset is less than the overlay size
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cmp r1, r4
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ifgteq mov r1, r4
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ifgteq dec r1
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; write the byte
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add r2, r1
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mov.8 [r2], [r0]
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pop r4
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pop r3
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pop r2
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pop r1
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ret
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