lc3asm 0.1.2

LC-3 assembly parser & assembler
Documentation 
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WHITESPACE = _{ (" " | "\t" | "\r" | "\n") }
COMMENT = _{";" ~ (!NEWLINE ~ ANY)* }

decimal = @{ "#"? ~ "-"? ~ ASCII_DIGIT+ }
hexadecimal = @{ ^"x" ~ "-"? ~ ASCII_HEX_DIGIT+ }
number = @{ decimal | hexadecimal }
register = @{ ^"r" ~ ASCII_DIGIT }
label = @{ (!ASCII_DIGIT ~ !WHITESPACE) ~ (!WHITESPACE ~ ASCII_ALPHANUMERIC)+ }
addressable = _{ label | number }

// https://pest.rs/book/examples/json.html#writing-the-grammar
string = ${ "\"" ~ inner ~ "\"" }
inner = @{ char* }
char = {
    !("\"" | "\\") ~ ANY
    | "\\" ~ ("\"" | "\\" | "/" | "b" | "f" | "n" | "r" | "t")
    | "\\" ~ ("u" ~ ASCII_HEX_DIGIT{4})
}

comma = _{ "," }

label_decl = { label }

// Instructions
add = { ( ^"ADD " | ^"ADD\t") ~ register ~ comma ~ register ~ comma ~ register }
add_immd = { ( ^"ADD " | ^"ADD\t") ~ register ~ comma ~ register ~ comma ~ (decimal | hexadecimal) }
and = { ( ^"AND " | ^"AND\t") ~ register ~ comma ~ register ~ comma ~ register }
and_immd = { ( ^"AND " | ^"AND\t") ~ register ~ comma ~ register ~ comma ~ (decimal | hexadecimal) }
not = { ( ^"NOT " | ^"NOT\t") ~ register ~ comma ~ register }
br = ${ ^"BR" ~ br_option ~ (!NEWLINE ~ WHITESPACE)+ ~ addressable}
jmp = { ( ^"JMP " | ^"JMP\t") ~ register }
jsr = { ( ^"JSR " | ^"JSR\t") ~ addressable }
jsrr = { ( ^"JSRR " | ^"JSRR\t") ~ register }
ld = { ( ^"LD " | ^"LD\t") ~ register ~ comma ~ addressable }
ldi = { ( ^"LDI " | ^"LDI\t") ~ register ~ comma ~ addressable }
ldr = { ( ^"LDR " | ^"LDR\t") ~ register ~ comma ~ register ~ comma ~ number }
st = { ( ^"ST " | ^"ST\t") ~ register ~ comma ~ addressable }
sti = { ( ^"STI " | ^"STI\t") ~ register ~ comma ~ addressable }
str = { ( ^"STR " | ^"STR\t") ~ register ~ comma ~ register ~ comma ~ number }
lea = { ( ^"LEA " | ^"LEA\t") ~ register ~ comma ~ addressable }
rti = { ^"RTI" }
ret = { ^"RET" }
trap = { ( ^"TRAP " | ^"TRAP\t") ~ number }
nop = { ^"NOP" }

br_n = @{ ("z" | "p")? ~ "n" ~ ("z" | "p")? }
br_z = @{ ("p" | "n")? ~ "z" ~ ("p" | "n")? }
br_p = @{ ("n" | "z")? ~ "p" ~ ("n" | "z")? }
br_option = @{ br_n? ~ br_z? ~ br_p? }

instruction = { add
                | add_immd
                | and
                | and_immd
                | not
                | br
                | jmp
                | jsr
                | jsrr
                | ld
                | ldi
                | ldr
                | st
                | sti
                | str
                | lea
                | rti
                | ret
                | trap
                | nop }

// Pseudo-operations
orig = ${ ^".orig" ~ ( " " | "\t" )+ ~ number }
end = ${ ^".end" }
blkw = ${ ^".blkw" ~ ( " " | "\t" )+ ~ number }
fill = ${ ^".fill" ~ ( " " | "\t" )+ ~ number}
stringz = ${ ^".stringz" ~ ( " " | "\t" )+ ~  string }

pseudo_op = _{ /* orig
                | end
                | */ blkw
                | fill
                | stringz }

// Trap codes
trap_code = ${ (^"halt" | ^"in" | ^"out" | ^"puts" | ^"putsp" | ^"getc") ~ WHITESPACE+ }
code = _{ instruction | pseudo_op | trap_code }
file = _{ SOI ~ orig ~ (!end ~ (code | label_decl))* ~ end ~ EOI }