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parse.go
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parse.go
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package compiler
import (
"bytes"
"encoding/hex"
"fmt"
"strconv"
"unicode"
)
// We have some function naming conventions.
//
// For terminals:
// scanX takes buf and position, returns new position (and maybe a value)
// peekX takes *parser, returns bool or string
// consumeX takes *parser and maybe a required literal, maybe returns value
// also updates the parser position
//
// For nonterminals:
// parseX takes *parser, returns AST node, updates parser position
type parser struct {
buf []byte
pos int
}
func (p *parser) errorf(format string, args ...interface{}) {
panic(parserErr{buf: p.buf, offset: p.pos, format: format, args: args})
}
// parse is the main entry point to the parser
func parse(buf []byte) (contracts []*Contract, err error) {
defer func() {
if val := recover(); val != nil {
if e, ok := val.(parserErr); ok {
err = e
} else {
panic(val)
}
}
}()
p := &parser{buf: buf}
contracts = parseContracts(p)
return
}
// parse functions
func parseContracts(p *parser) []*Contract {
var result []*Contract
if pos := scanKeyword(p.buf, p.pos, "contract"); pos < 0 {
p.errorf("expected contract")
}
for peekKeyword(p) == "contract" {
contract := parseContract(p)
result = append(result, contract)
}
return result
}
// contract name(p1, p2: t1, p3: t2) locks value { ... }
func parseContract(p *parser) *Contract {
consumeKeyword(p, "contract")
name := consumeIdentifier(p)
params := parseParams(p)
// locks amount of asset
consumeKeyword(p, "locks")
value := ValueInfo{}
value.Amount = consumeIdentifier(p)
consumeKeyword(p, "of")
value.Asset = consumeIdentifier(p)
consumeTok(p, "{")
clauses := parseClauses(p)
consumeTok(p, "}")
return &Contract{Name: name, Params: params, Clauses: clauses, Value: value}
}
// (p1, p2: t1, p3: t2)
func parseParams(p *parser) []*Param {
var params []*Param
consumeTok(p, "(")
first := true
for !peekTok(p, ")") {
if first {
first = false
} else {
consumeTok(p, ",")
}
pt := parseParamsType(p)
params = append(params, pt...)
}
consumeTok(p, ")")
return params
}
func parseClauses(p *parser) []*Clause {
var clauses []*Clause
for !peekTok(p, "}") {
c := parseClause(p)
clauses = append(clauses, c)
}
return clauses
}
func parseParamsType(p *parser) []*Param {
firstName := consumeIdentifier(p)
params := []*Param{&Param{Name: firstName}}
for peekTok(p, ",") {
consumeTok(p, ",")
name := consumeIdentifier(p)
params = append(params, &Param{Name: name})
}
consumeTok(p, ":")
typ := consumeIdentifier(p)
for _, parm := range params {
if tdesc, ok := types[typ]; ok {
parm.Type = tdesc
} else {
p.errorf("unknown type %s", typ)
}
}
return params
}
func parseClause(p *parser) *Clause {
var c Clause
consumeKeyword(p, "clause")
c.Name = consumeIdentifier(p)
c.Params = parseParams(p)
consumeTok(p, "{")
c.statements = parseStatements(p)
consumeTok(p, "}")
return &c
}
func parseStatements(p *parser) []statement {
var statements []statement
for !peekTok(p, "}") {
s := parseStatement(p)
statements = append(statements, s)
}
return statements
}
func parseStatement(p *parser) statement {
switch peekKeyword(p) {
case "if":
return parseIfStmt(p)
case "define":
return parseDefineStmt(p)
case "assign":
return parseAssignStmt(p)
case "verify":
return parseVerifyStmt(p)
case "lock":
return parseLockStmt(p)
case "unlock":
return parseUnlockStmt(p)
}
panic(parseErr(p.buf, p.pos, "unknown keyword \"%s\"", peekKeyword(p)))
}
func parseIfStmt(p *parser) *ifStatement {
consumeKeyword(p, "if")
condition := parseExpr(p)
body := &IfStatmentBody{}
consumeTok(p, "{")
body.trueBody = parseStatements(p)
consumeTok(p, "}")
if peekKeyword(p) == "else" {
consumeKeyword(p, "else")
consumeTok(p, "{")
body.falseBody = parseStatements(p)
consumeTok(p, "}")
}
return &ifStatement{condition: condition, body: body}
}
func parseDefineStmt(p *parser) *defineStatement {
defineStat := &defineStatement{}
consumeKeyword(p, "define")
param := &Param{}
param.Name = consumeIdentifier(p)
consumeTok(p, ":")
variableType := consumeIdentifier(p)
if tdesc, ok := types[variableType]; ok {
param.Type = tdesc
} else {
p.errorf("unknown type %s", variableType)
}
defineStat.variable = param
if peekTok(p, "=") {
consumeTok(p, "=")
defineStat.expr = parseExpr(p)
}
return defineStat
}
func parseAssignStmt(p *parser) *assignStatement {
consumeKeyword(p, "assign")
varName := consumeIdentifier(p)
consumeTok(p, "=")
expr := parseExpr(p)
return &assignStatement{variable: &Param{Name: varName}, expr: expr}
}
func parseVerifyStmt(p *parser) *verifyStatement {
consumeKeyword(p, "verify")
expr := parseExpr(p)
return &verifyStatement{expr: expr}
}
func parseLockStmt(p *parser) *lockStatement {
consumeKeyword(p, "lock")
lockedAmount := parseExpr(p)
consumeKeyword(p, "of")
lockedAsset := parseExpr(p)
consumeKeyword(p, "with")
program := parseExpr(p)
return &lockStatement{lockedAmount: lockedAmount, lockedAsset: lockedAsset, program: program}
}
func parseUnlockStmt(p *parser) *unlockStatement {
consumeKeyword(p, "unlock")
unlockedAmount := parseExpr(p)
consumeKeyword(p, "of")
unlockedAsset := parseExpr(p)
return &unlockStatement{unlockedAmount: unlockedAmount, unlockedAsset: unlockedAsset}
}
func parseExpr(p *parser) expression {
// Uses the precedence-climbing algorithm
// <https://en.wikipedia.org/wiki/Operator-precedence_parser#Precedence_climbing_method>
expr := parseUnaryExpr(p)
expr2, pos := parseExprCont(p, expr, 0)
if pos < 0 {
p.errorf("expected expression")
}
p.pos = pos
return expr2
}
func parseUnaryExpr(p *parser) expression {
op, pos := scanUnaryOp(p.buf, p.pos)
if pos < 0 {
return parseExpr2(p)
}
p.pos = pos
expr := parseUnaryExpr(p)
return &unaryExpr{op: op, expr: expr}
}
func parseExprCont(p *parser, lhs expression, minPrecedence int) (expression, int) {
for {
op, pos := scanBinaryOp(p.buf, p.pos)
if pos < 0 || op.precedence < minPrecedence {
break
}
p.pos = pos
rhs := parseUnaryExpr(p)
for {
op2, pos2 := scanBinaryOp(p.buf, p.pos)
if pos2 < 0 || op2.precedence <= op.precedence {
break
}
rhs, p.pos = parseExprCont(p, rhs, op2.precedence)
if p.pos < 0 {
return nil, -1 // or is this an error?
}
}
lhs = &binaryExpr{left: lhs, right: rhs, op: op}
}
return lhs, p.pos
}
func parseExpr2(p *parser) expression {
if expr, pos := scanLiteralExpr(p.buf, p.pos); pos >= 0 {
p.pos = pos
return expr
}
return parseExpr3(p)
}
func parseExpr3(p *parser) expression {
e := parseExpr4(p)
if peekTok(p, "(") {
args := parseArgs(p)
return &callExpr{fn: e, args: args}
}
return e
}
func parseExpr4(p *parser) expression {
if peekTok(p, "(") {
consumeTok(p, "(")
e := parseExpr(p)
consumeTok(p, ")")
return e
}
if peekTok(p, "[") {
var elts []expression
consumeTok(p, "[")
first := true
for !peekTok(p, "]") {
if first {
first = false
} else {
consumeTok(p, ",")
}
e := parseExpr(p)
elts = append(elts, e)
}
consumeTok(p, "]")
return listExpr(elts)
}
name := consumeIdentifier(p)
return varRef(name)
}
func parseArgs(p *parser) []expression {
var exprs []expression
consumeTok(p, "(")
first := true
for !peekTok(p, ")") {
if first {
first = false
} else {
consumeTok(p, ",")
}
e := parseExpr(p)
exprs = append(exprs, e)
}
consumeTok(p, ")")
return exprs
}
// peek functions
func peekKeyword(p *parser) string {
name, _ := scanIdentifier(p.buf, p.pos)
return name
}
func peekTok(p *parser, token string) bool {
pos := scanTok(p.buf, p.pos, token)
return pos >= 0
}
// consume functions
var keywords = []string{
"contract", "clause", "verify", "locks", "of",
"lock", "with", "unlock", "if", "else",
"define", "assign", "true", "false",
}
func consumeKeyword(p *parser, keyword string) {
pos := scanKeyword(p.buf, p.pos, keyword)
if pos < 0 {
p.errorf("expected keyword %s", keyword)
}
p.pos = pos
}
func consumeIdentifier(p *parser) string {
name, pos := scanIdentifier(p.buf, p.pos)
if pos < 0 {
p.errorf("expected identifier")
}
p.pos = pos
return name
}
func consumeTok(p *parser, token string) {
pos := scanTok(p.buf, p.pos, token)
if pos < 0 {
p.errorf("expected %s token", token)
}
p.pos = pos
}
// scan functions
func scanUnaryOp(buf []byte, offset int) (*unaryOp, int) {
// Maximum munch. Make sure "-3" scans as ("-3"), not ("-", "3").
if _, pos := scanIntLiteral(buf, offset); pos >= 0 {
return nil, -1
}
for _, op := range unaryOps {
newOffset := scanTok(buf, offset, op.op)
if newOffset >= 0 {
return &op, newOffset
}
}
return nil, -1
}
func scanBinaryOp(buf []byte, offset int) (*binaryOp, int) {
offset = skipWsAndComments(buf, offset)
var (
found *binaryOp
newOffset = -1
)
for i, op := range binaryOps {
offset2 := scanTok(buf, offset, op.op)
if offset2 >= 0 {
if found == nil || len(op.op) > len(found.op) {
found = &binaryOps[i]
newOffset = offset2
}
}
}
return found, newOffset
}
// TODO(bobg): boolean literals?
func scanLiteralExpr(buf []byte, offset int) (expression, int) {
offset = skipWsAndComments(buf, offset)
intliteral, newOffset := scanIntLiteral(buf, offset)
if newOffset >= 0 {
return intliteral, newOffset
}
strliteral, newOffset := scanStrLiteral(buf, offset)
if newOffset >= 0 {
return strliteral, newOffset
}
bytesliteral, newOffset := scanBytesLiteral(buf, offset) // 0x6c249a...
if newOffset >= 0 {
return bytesliteral, newOffset
}
booleanLiteral, newOffset := scanBoolLiteral(buf, offset) // true or false
if newOffset >= 0 {
return booleanLiteral, newOffset
}
return nil, -1
}
func scanIdentifier(buf []byte, offset int) (string, int) {
offset = skipWsAndComments(buf, offset)
i := offset
for ; i < len(buf) && isIDChar(buf[i], i == offset); i++ {
}
if i == offset {
return "", -1
}
return string(buf[offset:i]), i
}
func scanTok(buf []byte, offset int, s string) int {
offset = skipWsAndComments(buf, offset)
prefix := []byte(s)
if bytes.HasPrefix(buf[offset:], prefix) {
return offset + len(prefix)
}
return -1
}
func scanKeyword(buf []byte, offset int, keyword string) int {
id, newOffset := scanIdentifier(buf, offset)
if newOffset < 0 {
return -1
}
if id != keyword {
return -1
}
return newOffset
}
func scanIntLiteral(buf []byte, offset int) (integerLiteral, int) {
offset = skipWsAndComments(buf, offset)
start := offset
if offset < len(buf) && buf[offset] == '-' {
offset++
}
i := offset
for ; i < len(buf) && unicode.IsDigit(rune(buf[i])); i++ {
// the literal is BytesLiteral when it starts with 0x/0X
if buf[i] == '0' && i < len(buf)-1 && (buf[i+1] == 'x' || buf[i+1] == 'X') {
return 0, -1
}
}
if i > offset {
n, err := strconv.ParseInt(string(buf[start:i]), 10, 64)
if err != nil {
return 0, -1
}
return integerLiteral(n), i
}
return 0, -1
}
func scanStrLiteral(buf []byte, offset int) (bytesLiteral, int) {
offset = skipWsAndComments(buf, offset)
if offset >= len(buf) || buf[offset] != '\'' {
return bytesLiteral{}, -1
}
var byteBuf bytesLiteral
for i := offset + 1; i < len(buf); i++ {
if buf[i] == '\'' {
return byteBuf, i + 1
}
if buf[i] == '\\' && i < len(buf)-1 {
if c, ok := scanEscape(buf[i+1]); ok {
byteBuf = append(byteBuf, c)
i++
continue
}
}
byteBuf = append(byteBuf, buf[i])
}
panic(parseErr(buf, offset, "unterminated string literal"))
}
func scanBytesLiteral(buf []byte, offset int) (bytesLiteral, int) {
offset = skipWsAndComments(buf, offset)
if offset+4 >= len(buf) {
return nil, -1
}
if buf[offset] != '0' || (buf[offset+1] != 'x' && buf[offset+1] != 'X') {
return nil, -1
}
if !isHexDigit(buf[offset+2]) || !isHexDigit(buf[offset+3]) {
return nil, -1
}
i := offset + 4
for ; i < len(buf); i += 2 {
if i == len(buf)-1 {
panic(parseErr(buf, offset, "odd number of digits in hex literal"))
}
if !isHexDigit(buf[i]) {
break
}
if !isHexDigit(buf[i+1]) {
panic(parseErr(buf, offset, "odd number of digits in hex literal"))
}
}
decoded := make([]byte, hex.DecodedLen(i-(offset+2)))
_, err := hex.Decode(decoded, buf[offset+2:i])
if err != nil {
return bytesLiteral{}, -1
}
return bytesLiteral(decoded), i
}
func scanBoolLiteral(buf []byte, offset int) (booleanLiteral, int) {
offset = skipWsAndComments(buf, offset)
if offset >= len(buf) {
return false, -1
}
newOffset := scanKeyword(buf, offset, "true")
if newOffset < 0 {
if newOffset = scanKeyword(buf, offset, "false"); newOffset < 0 {
return false, -1
}
return false, newOffset
}
return true, newOffset
}
func skipWsAndComments(buf []byte, offset int) int {
var inComment bool
for ; offset < len(buf); offset++ {
c := buf[offset]
if inComment {
if c == '\n' {
inComment = false
}
} else {
if c == '/' && offset < len(buf)-1 && buf[offset+1] == '/' {
inComment = true
offset++ // skip two chars instead of one
} else if !unicode.IsSpace(rune(c)) {
break
}
}
}
return offset
}
func isHexDigit(b byte) bool {
return (b >= '0' && b <= '9') || (b >= 'a' && b <= 'f') || (b >= 'A' && b <= 'F')
}
func isIDChar(c byte, initial bool) bool {
if c >= 'a' && c <= 'z' {
return true
}
if c >= 'A' && c <= 'Z' {
return true
}
if c == '_' {
return true
}
if initial {
return false
}
return unicode.IsDigit(rune(c))
}
type parserErr struct {
buf []byte
offset int
format string
args []interface{}
}
func parseErr(buf []byte, offset int, format string, args ...interface{}) error {
return parserErr{buf: buf, offset: offset, format: format, args: args}
}
func (p parserErr) Error() string {
// Lines start at 1, columns start at 0, like nature intended.
line := 1
col := 0
for i := 0; i < p.offset; i++ {
if p.buf[i] == '\n' {
line++
col = 0
} else {
col++
}
}
args := []interface{}{line, col}
args = append(args, p.args...)
return fmt.Sprintf("line %d, col %d: "+p.format, args...)
}
func scanEscape(c byte) (byte, bool) {
escapeFlag := true
switch c {
case '\'', '"', '\\':
case 'b':
c = '\b'
case 'f':
c = '\f'
case 'n':
c = '\n'
case 'r':
c = '\r'
case 't':
c = '\t'
case 'v':
c = '\v'
default:
escapeFlag = false
}
return c, escapeFlag
}