lips/lips/Muncher.lua

local format = string.format

local data = require "lips.data"
local Muncher = require("lips.Class")()

function Muncher:error(msg)
    error(format('%s:%d: Error: %s', self.fn, self.line, msg), 2)
end

function Muncher:advance()
    self.i = self.i + 1
    local t = self.tokens[self.i]
    self.tt = t.tt
    self.tok = t.tok
    self.fn = t.fn
    self.line = t.line
    return t
end

function Muncher:is_EOL()
    return self.tt == 'EOL' or self.tt == 'EOF'
end

function Muncher:expect_EOL()
    if self:is_EOL() then
        self:advance()
        return
    end
    self:error('expected end of line')
end

function Muncher:optional_comma()
    if self.tt == 'SEP' and self.tok == ',' then
        self:advance()
        return true
    end
end

function Muncher:number()
    if self.tt ~= 'NUM' then
        self:error('expected number')
    end
    local value = self.tok
    self:advance()
    return value
end

function Muncher:string()
    if self.tt ~= 'STRING' then
        self:error('expected string')
    end
    local value = self.tok
    self:advance()
    return value
end

function Muncher:register(t)
    t = t or data.registers
    if self.tt ~= 'REG' then
        self:error('expected register')
    end
    local reg = self.tok
    if not t[reg] then
        self:error('wrong type of register')
    end
    self:advance()
    return reg
end

function Muncher:deref()
    if self.tt ~= 'OPEN' then
        self:error('expected opening parenthesis for dereferencing')
    end
    self:advance()
    if self.tt ~= 'REG' then
        self:error('expected register to dereference')
    end
    local reg = self.tok
    self:advance()
    if self.tt ~= 'CLOSE' then
        self:error('expected closing parenthesis for dereferencing')
    end
    self:advance()
    return reg
end

function Muncher:const(relative, no_label)
    if self.tt ~= 'NUM' and self.tt ~= 'LABELSYM' then
        self:error('expected constant')
    end
    if no_label and self.tt == 'LABELSYM' then
        self:error('labels are not allowed here')
    end
    if relative and self.tt == 'LABELSYM' then
        self.tt = 'LABELREL'
    end
    local t = {self.tt, self.tok}
    self:advance()
    return t
end

return Muncher