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Angala/angala.asm

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NASM
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;ThingamaTerm: A simple terminal emulator
;***
;Check for input and incoming data
;Load the masks
check: load r2, #1
load r3, #20
;Load the input status
chklop: load r0, fff8
xor r1, r1
xor r1, r0
;Mask out unnecessary data
and r0, r2
and r1, r3
;Branch
breq r0, r2, input
breq r1, r3, recv
breq r0, r0, chklop
;***
;Input a line
;Restore the buffer start address
;High byte
input: load r0, bfstrt
store chstor + 1, r0
;Low byte
load r0, bfstrt + 1
store chstor + 2, r0
;Initialise the character counter
xor r0, r0
;Check for an initial end-of-file
load r1, ffff
load r2, #1a
brneq r1, r2, chknul
;Print a newline and halt
cleq r0, r0, newln
halt
;Read a character
inloop: load r1, ffff
;Check for control characters and the buffer end
;Null
chknul: load r2, #0
breq r1, r2, inloop
;FF
load r2, #ff
breq r1, r2, inloop
;Delete
load r2, #7f
breq r1, r2, delbr
;Escape
load r2, #1b
breq r1, r2, escbr
;End-of-file
load r2, #1a
breq r1, r2, eofbr
;Carriage return
load r2, #d
breq r1, r2, crbr
;Line feed
load r2, #a
breq r1, r2, lfbr
;Buffer end
load r2, bfsize
brneq r0, r2, chstor
;Backtrack if at the buffer end
load r2, #8
store ffff, r2
breq r0, r0, inloop
;Store the character in the buffer
chstor: store buffer, r1
;Increment the character counter and store it in r3
;Increment
load r2, #1
cleq r0, r0, sum
;Store
xor r3, r3
xor r3, r0
;Increment the buffer address
;Low byte
load r0, chstor + 2
load r2, #1
cleq r0, r0, sum
store chstor + 2, r0
;Add the overflow to the high byte
load r0, chstor + 1
xor r2, r2
xor r2, r1
cleq r0, r0, sum
store chstor + 1, r0
;Reload the character counter to r0
xor r0, r0
xor r0, r3
;Read the next character
breq r0, r0, inloop
;Print an underscore
delbr: load r2, #5f
store ffff, r2
;Check for buffer start
xor r2, r2
breq r0, r2, inloop
;Decrement the character counter and store it in r3
;Decrement
load r2, #ff
cleq r0, r0, sum
;Store
xor r3, r3
xor r3, r0
;Decrement the buffer address
;High byte
load r0, chstor + 1
load r2, #ff
cleq r0, r0, sum
store chstor + 1, r0
;Low byte
load r0, chstor + 2
load r2, #ff
cleq r0, r0, sum
store chstor + 2, r0
;Add the overflow to the high byte
load r0, chstor + 1
xor r2, r2
xor r2, r1
cleq r0, r0, sum
store chstor + 1, r0
;Reload the character counter to r0
xor r0, r0
xor r0, r3
;Read the next character
breq r0, r0, inloop
;Print a backslash and a newline and re-input the line
;Backslash
escbr: load r0, #20
store ffff, r0
load r0, #5c
store ffff, r0
;Newline
cleq r0, r0, newln
;Re-input the line
breq r0, r0, input
;Print a newline and exit input mode
eofbr: cleq r0, r0, newln
breq r0, r0, check
;Print a line feed
crbr: load r1, #a
store ffff, r1
breq r0, r0, endnl
;Print a carriage return and a null
lfbr: load r1, #d
store ffff, r1
load r1, #0
store ffff, r1
;Get the buffer address
endnl: load r1, chstor + 1
store endcr + 1, r1
load r1, chstor + 2
store endcr + 2, r1
;Store the CR of a newline in the buffer
load r0, #d
endcr: store 0, r0
;Increment the buffer address
;Load the address
load r0, chstor + 1
load r1, chstor + 2
;Increment
cleq r0, r0, incdw
;Store the address
store endlf + 1, r0
store endlf + 2, r1
;Store the LF of a newline in the buffer
load r0, #a
endlf: store 0, r0
;***
;Send the line
;Restore the buffer start address
;High byte
load r0, bfstrt
store lodmsg + 1, r0
;Low byte
load r0, bfstrt + 1
store lodmsg + 2, r0
;Send a character
;Send
lodmsg: load r0, 0
store fffa, r0
;Check for line feed
load r1, #a
breq r0, r1, check
;Increment the buffer address
load r0, lodmsg + 1
load r1, lodmsg + 2
cleq r0, r0, incdw
store lodmsg + 1, r0
store lodmsg + 2, r1
;Send the next character
breq r0, r0, lodmsg
;***
;Recieve a character
;Check for connection
recv: load r1, fff9
load r2, #1
brneq r1, r2, noconn
;Read and print a character
load r1, fffa
store ffff, r1
;Check for input and incoming data
breq r0, r0, check
;Print a newline and halt
noconn: cleq r0, r0, newln
halt
;***
;Print a newline
newln: load r0, #d
store ffff, r0
load r0, #a
store ffff, r0
ret
;***
;Add r2 to r0 with the overflow stored in r1
;Reset overflow
sum: xor r1, r1
store ovrflw, r1
;Copy the first argument to r1
sumlop: xor r1, r1
xor r1, r0
;Calculate the sum and carry and copy the pre-shift carry to r1
;Sum
xor r0, r2
;Carry
and r2, r1
;Copy the pre-shift carry
xor r1, r1
xor r1, r2
;Shift the carry
shl r2, 1
;Check for and store overflow if any
;Check
rol r1, 1
breq r1, r2, nvrflw
;Store
load r1, #1
store ovrflw, r1
;Check for no carry
nvrflw: xor r1, r1
breq r1, r2, sumend
;Loop
breq r0, r0, sumlop
;Load overflow and return
sumend: load r1, ovrflw
ret
;***
;Increment a value stored in r0 and r1
;Store the high byte in r3
incdw: xor r3, r3
xor r3, r0
;Load the low byte to r0
xor r0, r0
xor r0, r1
;Increment the low byte
load r2, #1
cleq r0, r0, sum
;Load the high byte to r0 and store the low byte in r3
;Move the high byte to r2
xor r2, r2
xor r2, r3
;Store the low byte to r3
xor r3, r3
xor r3, r0
;Load the high byte to r0
xor r0, r0
xor r0, r2
;Add the overflow to the high byte
xor r2, r2
xor r2, r1
cleq r0, r0, sum
;Load the low byte in r1
xor r1, r1
xor r1, r3
;Return
ret
;***
;Data
;Ping
pingst: addr ping
ping: data 50
data 49
data 4e
data 47
data 20
data 3a
;Variables
ovrflw: data 0
;Buffer
bfstrt: addr buffer
bfsize: data fe
buffer:

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