path: root/03/in02

// open input file
im
--IF
JA
zA
IA
im
##2.
sy
// open output file
im
--OF
JA
im
##241.
IA
im
##1ed.
DA
im
##2.
sy
// write ELF header
im
##4.
JA    output fd
im
##400000.  address of ELF header in this executable
IA
im
##78.  length
DA
im
##1.  write
sy
// read next line
::rl
im
--LI
RA    rbp pointer to line buffer
::rL  read loop
im
##3.  input file descriptor
JA
IR    where to read into
im
##1.
DA    read 1 byte
im
##0.  syscall 0 (read)
sy
// check how many bytes were read
BA
im
##1.
jg   if 1 greater than number of bytes read
:-ef    end of file
BR
DR   pointer to character we just read
im
##1.
+B
RA
BD
zA
lb
BA
im
##a.
jn
:-rL  keep looping
// we now have a full line from the file in ::LI
// the pointer to the end of the line is in rbp
// look at the first character
im
--LI
BA
zA
lb
BA
im
##3b.  ascii ';'
je    if it's a comment,
:-rl  jump back to read the next line
im
##a.  ascii '\n'
je    if it's a blank line,
:-rl  jump back to read the next line
im
##3a.  ascii ':'
je
:-ld   label definition
jm
:-ex
// label definition
::ld
// first, check if we're on the second pass.
im
--2P
BA
zA
lb
BA
zA
jn     if on second pass,
:-rl   ignore this (read next line)
// first get current address
im
##4. output fd
JA
zA
IA   offset = 0
im
##1. whence = SEEK_CUR
DA
im
##8. syscall 8 = lseek
sy
BA
im
##400000. address of start of file
+B
DA   put current address in rdx
im
--L$
BA
lq
JA
im
--LI
IA
// copy from rsi to rdi until a newline is reached
::lc  label copy
BI
zA
lb
BA
// store in rdi
AJ
xc
sb
CA put byte in rcx
// increment rdi,rsi
BJ
im
##1.
+B
JA
BI
im
##1.
+B
IA
BC
im
##a.
jn   if byte we read wasn't a newline,
:-lc keep looping
// store address of label in rdi
AD
BJ
sd
// increment rdi by 4, because we stored an 4-byte number
im
##4.
+B
JA
// now set L$ to rdi
im
--L$
BA
AJ
sq
// read the next line
jm
:-rl
// label lookup--set rax to address of label in rbx
::ll
RB  put ptr to label in rbp
// if it's the first pass, just return 0
im
--2P
BA
zA
lb
BA
zA
je
:-r0
// okay it's not the second pass
im
##a.
CA   terminator '\n'
// use rsi to keep track of position in label list
im
--LB
IA
::lL
// first, check if we've reached the end of the label list (rsi == *L$)
im
--L$
BA
lq
BI
je
:-bl  bad label if we've reached the end
JR
im
--s=
cl
BA
im
##1.
je
:-l=
// this isn't the label; advance
::l\
zA
BI
lb
DA
// increment rsi
BI
im
##1.
+B
IA
// check if that byte we looked at was a newline
BD
im
##a.
jn
:-l\  if not, keep looping
// now we need to increment rsi by another 4 bytes, to skip over the address
BI
im
##4.
+B
IA
jm
:-lL
re
::l=
// label found!
// first, increment rsi past newline:
BI
im
##1.
+B
IA
// then, read dword at rsi into rax
BI
zA
ld
// we're done!! 
re
// set rax to 1/0 depending on whether rsi and rdi have the same string, up to the terminator in rcx.
::s=
BI
zA
lb
DA
BJ
zA
lb
BD
jn
:-r0  1st characters are not equal
BC
je
:-r1  we reached the end of the string
// increment rsi, rdi
BI
im
##1.
+B
IA
BJ
im
##1.
+B
JA
jm
:-s= keep looping
// return 0
::r0
zA
re
// return 1
::r1
im
##1.
re
// exit with code in rax
::ex
JA
im
##3c.
sy
// convert string representation of number starting at rbx and ending with a newline to number in rax
::nu
DB
im
##1.
+B
IA  start by storing pointer to actual number (not including base) in rsi
BD
zA
lb
BA
im
##64. ascii 'd'
je
:-#d  decimal
im
##78. ascii 'x'
je
:-#x  hexadecimal
jm
:-bn  unrecognized number base
// convert newline-terminated decimal representation in rsi to number in rax
::#d
zA
JA   use rdi to store number
::dL  decimal loop
BI
zA
lb
BA
im
##a.
je
:-d$  newline reached
im
##30.
jg
:-bn  bad digit (<'0')
im
##39.
jl
:-bn  bad digit (>'9')
im
##ffffffffffffffd0.
+B
CA  put numerical value of digit in rcx
im
##a.
BA
AJ
+*  multiply by 10
BC
+B  add digit
JA
// increment rsi
BI
im
##1.
+B
IA
jm
:-dL  keep looping
::d$
AJ
re   return
::#x
zA
JA  use rdi to store number
::xL hexadecimal loop
BI
zA
lb
BA
im
##a.
je
:-x$  newline reached
im
##30. compare with ascii '0'
jg
:-bn  bad if < '0'
im
##39.
jl
:-af  probably a-f
im
##ffffffffffffffd0.  -48
jm
:-hX
::af
im
##61. ASCII 'a'
jg
:-bn  bad digit (not 0-9, and less than 'a')
im
##66. ASCII 'f'
jl
:-bn  bad digit (not 0-9, and greater than 'f')
im
##ffffffffffffffa9.  -87 (10 - 'a')
::hX
+B
BA
// digit's numerical value now in rbx
AJ
<I
04
+B   add digit
JA   store away
// increment rsi
BI
im
##1.
+B
IA
jm
:-xL
::x$
AJ
re  return
// bad number
::bn
im
##2. stderr
JA
im
--BN error message
IA
im
##b. length of error message
DA
im
##1. write
sy
im
##1.
jm
:-ex
// bad label
::bl
im
##2. stderr
JA
im
--BL error message
IA
im
##a. length of error message
DA
im
##1. write
sy
im
##1.
jm
:-ex
// end of file
::ef
// TODO: second pass
zA  exit code 0
jm
:-ex
::2P  second pass?
00
::IF  input file name
'i
'n
'0
'3
00
::OF  output file name
'o
'u
't
'0
'3
00
::BN  bad number error message
'B
'a
'd
20
'n
'u
'm
'b
'e
'r
\n
::BL  bad label error message
'B
'a
'd
20
'l
'a
'b
'e
'l
\n
::LI  line buffer
~~
::L$  end of current label list
--LB
::LB  labels
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~
~~