// Copyright 2017 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
package asm
import (
"fmt"
"math/big"
"os"
"strings"
"github.com/ethereum/go-ethereum/common/math"
"github.com/ethereum/go-ethereum/core/vm"
)
// Compiler contains information about the parsed source
// and holds the tokens for the program.
type Compiler struct {
tokens []token
binary []interface{}
labels map[string]int
pc, pos int
debug bool
}
// newCompiler returns a new allocated compiler.
func NewCompiler(debug bool) *Compiler {
return &Compiler{
labels: make(map[string]int),
debug: debug,
}
}
// Feed feeds tokens in to ch and are interpreted by
// the compiler.
//
// feed is the first pass in the compile stage as it
// collects the used labels in the program and keeps a
// program counter which is used to determine the locations
// of the jump dests. The labels can than be used in the
// second stage to push labels and determine the right
// position.
func (c *Compiler) Feed(ch <-chan token) {
for i := range ch {
switch i.typ {
case number:
num := math.MustParseBig256(i.text).Bytes()
if len(num) == 0 {
num = []byte{0}
}
c.pc += len(num)
case stringValue:
c.pc += len(i.text) - 2
case element:
c.pc++
case labelDef:
c.labels[i.text] = c.pc
c.pc++
case label:
c.pc += 5
}
c.tokens = append(c.tokens, i)
}
if c.debug {
fmt.Fprintln(os.Stderr, "found", len(c.labels), "labels")
}
}
// Compile compiles the current tokens and returns a
// binary string that can be interpreted by the EVM
// and an error if it failed.
//
// compile is the second stage in the compile phase
// which compiles the tokens to EVM instructions.
func (c *Compiler) Compile() (string, []error) {
var errors []error
// continue looping over the tokens until
// the stack has been exhausted.
for c.pos < len(c.tokens) {
if err := c.compileLine(); err != nil {
errors = append(errors, err)
}
}
// turn the binary to hex
var bin string
for _, v := range c.binary {
switch v := v.(type) {
case vm.OpCode:
bin += fmt.Sprintf("%x", []byte{byte(v)})
case []byte:
bin += fmt.Sprintf("%x", v)
}
}
return bin, errors
}
// next returns the next token and increments the
// position.
func (c *Compiler) next() token {
token := c.tokens[c.pos]
c.pos++
return token
}
// compileLine compiles a single line instruction e.g.
// "push 1", "jump @label".
func (c *Compiler) compileLine() error {
n := c.next()
if n.typ != lineStart {
return compileErr(n, n.typ.String(), lineStart.String())
}
lvalue := c.next()
switch lvalue.typ {
case eof:
return nil
case element:
if err := c.compileElement(lvalue); err != nil {
return err
}
case labelDef:
c.compileLabel()
case lineEnd:
return nil
default:
return compileErr(lvalue, lvalue.text, fmt.Sprintf("%v or %v", labelDef, element))
}
if n := c.next(); n.typ != lineEnd {
return compileErr(n, n.text, lineEnd.String())
}
return nil
}
// compileNumber compiles the number to bytes
func (c *Compiler) compileNumber(element token) (int, error) {
num := math.MustParseBig256(element.text).Bytes()
if len(num) == 0 {
num = []byte{0}
}
c.pushBin(num)
return len(num), nil
}
// compileElement compiles the element (push & label or both)
// to a binary representation and may error if incorrect statements
// where fed.
func (c *Compiler) compileElement(element token) error {
// check for a jump. jumps must be read and compiled
// from right to left.
if isJump(element.text) {
rvalue := c.next()
switch rvalue.typ {
case number:
// TODO figure out how to return the error properly
c.compileNumber(rvalue)
case stringValue:
// strings are quoted, remove them.
c.pushBin(rvalue.text[1 : len(rvalue.text)-2])
case label:
c.pushBin(vm.PUSH4)
pos := big.NewInt(int64(c.labels[rvalue.text])).Bytes()
pos = append(make([]byte, 4-len(pos)), pos...)
c.pushBin(pos)
default:
return compileErr(rvalue, rvalue.text, "number, string or label")
}
// push the operation
c.pushBin(toBinary(element.text))
return nil
} else if isPush(element.text) {
// handle pushes. pushes are read from left to right.
var value []byte
rvalue := c.next()
switch rvalue.typ {
case number:
value = math.MustParseBig256(rvalue.text).Bytes()
if len(value) == 0 {
value = []byte{0}
}
case stringValue:
value = []byte(rvalue.text[1 : len(rvalue.text)-1])
case label:
value = make([]byte, 4)
copy(value, big.NewInt(int64(c.labels[rvalue.text])).Bytes())
default:
return compileErr(rvalue, rvalue.text, "number, string or label")
}
if len(value) > 32 {
return fmt.Errorf("%d type error: unsupported string or number with size > 32", rvalue.lineno)
}
c.pushBin(vm.OpCode(int(vm.PUSH1) - 1 + len(value)))
c.pushBin(value)
} else {
c.pushBin(toBinary(element.text))
}
return nil
}
// compileLabel pushes a jumpdest to the binary slice.
func (c *Compiler) compileLabel() {
c.pushBin(vm.JUMPDEST)
}
// pushBin pushes the value v to the binary stack.
func (c *Compiler) pushBin(v interface{}) {
if c.debug {
fmt.Printf("%d: %v\n", len(c.binary), v)
}
c.binary = append(c.binary, v)
}
// isPush returns whether the string op is either any of
// push(N).
func isPush(op string) bool {
return strings.ToUpper(op) == "PUSH"
}
// isJump returns whether the string op is jump(i)
func isJump(op string) bool {
return strings.ToUpper(op) == "JUMPI" || strings.ToUpper(op) == "JUMP"
}
// toBinary converts text to a vm.OpCode
func toBinary(text string) vm.OpCode {
return vm.StringToOp(strings.ToUpper(text))
}
type compileError struct {
got string
want string
lineno int
}
func (err compileError) Error() string {
return fmt.Sprintf("%d syntax error: unexpected %v, expected %v", err.lineno, err.got, err.want)
}
func compileErr(c token, got, want string) error {
return compileError{
got: got,
want: want,
lineno: c.lineno,
}
}
