/
ast.go
820 lines (755 loc) · 18.5 KB
/
ast.go
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/************************************************************************************
author: soforth
date: 2014-9-13
email: soforth@qq.com
description: a HTTP package filter, supported BNF as bellow:
grammer -> expr => RET grammer // if ( expr ) return RET else return grammer
| default => RET grammer // if grammer != 0 return grammer default: return RET
| expr grammer // if ( expr) return grammer else return 0
;
expr -> expr || term // logic OR operation
| expr && term // logic AND operation
| term
;
term -> factor @ ( list ) // variable/string/double is in list
| factor !@ ( list ) // variable/string/double is not in list
| factor > factor // left great than right
| factor < factor // left less than right
| factor == factor // left equal right
| factor != factor // left not equal right
| factor >= factor // left great than or equal right
| factor <= factor // left less than or equal right
| factor # REGEX // left regex match right pattern
| factor !# REGEX // left regex not match right pattern
| ( expr ) // term can be a expr in paren
;
list -> factor list; // list is recursive defined
factor -> DOUBLE_const // factor can be double immediate constant
| STRING_const // also can be string immediate constant
| VAR_str // also can be variable as symbol input by user
| func // also can be a internal function
;
func -> VAR_str ( list ); // function has zero or more arguments
*************************************************************************************/
package filter
import (
"crypto/md5"
"errors"
"fmt"
"io"
"math"
"regexp"
"strconv"
)
type GKind_t int // for Grammer
type EKind_t int // for Expr
type TKind_t int // for Term
type FKind_t int // for Factor & SymList
type FnKind_t int // for Func
const (
EGET = GKind_t(0)
DGET = GKind_t(1)
EEXPR = GKind_t(2)
AND = EKind_t(0)
OR = EKind_t(1)
TERM = EKind_t(2)
IN = TKind_t(0)
NI = TKind_t(1)
GT = TKind_t(2)
LT = TKind_t(3)
EQ = TKind_t(4)
NE = TKind_t(5)
GE = TKind_t(6)
LE = TKind_t(7)
MA = TKind_t(8)
NM = TKind_t(9)
EXPR = TKind_t(10)
DOUBLE = FKind_t(0)
STRING = FKind_t(1)
VARIABLE = FKind_t(2)
FUNCTION = FKind_t(3)
LEN = FnKind_t(0)
MD5 = FnKind_t(1)
COUNT = FnKind_t(2)
ATOI = FnKind_t(3)
ITOA = FnKind_t(4)
)
type Grammer struct {
Kind GKind_t // EGET, DGET, EEXPR
Expr *Expr
Ret float64
Grammer *Grammer
}
type Expr struct {
Kind EKind_t // AND, OR, TERM
Left *Expr
Right *Term
}
type Term struct {
Kind TKind_t // IN, NI, GT, LT, EQ, NE, GE, LE, MA, NM, EXPR
Left *Factor
Right interface{}
}
type Factor struct {
Kind FKind_t // DOUBLE, STRING, VARIABLE, FUNCTION
Value interface{}
}
type Func struct {
Kind FnKind_t // LEN, MD5, COUNT, ATOI, ITOA
List *List
}
type List struct {
Factor *Factor
Next *List
}
type SymList struct {
Kind FKind_t // DOUBLE, STRING
Name string
Value interface{}
Next *SymList
}
func gkind2str(kind GKind_t) string {
switch kind {
case EGET:
return "<expr> =>"
case DGET:
return "default =>"
case EEXPR:
return "<expr>"
}
return fmt.Sprintf("%d", int(kind))
}
func ekind2str(kind EKind_t) string {
switch kind {
case AND:
return "&&"
case OR:
return "||"
case TERM:
return "<term alone>"
}
return fmt.Sprintf("%d", int(kind))
}
func tkind2str(kind TKind_t) string {
switch kind {
case IN:
return "@"
case NI:
return "!@"
case GT:
return ">"
case LT:
return "<"
case GE:
return ">="
case LE:
return "<="
case EQ:
return "=="
case NE:
return "!="
case MA:
return "#"
case NM:
return "!#"
}
return fmt.Sprintf("%d", int(kind))
}
func fkind2str(kind FKind_t) string {
switch kind {
case DOUBLE:
return "float64"
case STRING:
return "string"
case VARIABLE:
return "var"
case FUNCTION:
return "func"
}
return fmt.Sprintf("%d", int(kind))
}
func fnkind2str(kind FnKind_t) string {
switch kind {
case LEN:
return "len"
case COUNT:
return "count"
case MD5:
return "md5"
case ITOA:
return "itoa"
case ATOI:
return "atoi"
}
return fmt.Sprintf("%d", int(kind))
}
func bool2int(v bool) int {
if v {
return 1
}
return 0
}
func cast2string(i interface{}) (string, error) {
if v, ok := i.(string); ok == true {
return v, nil
}
return "", errors.New("not a 'string'")
}
func cast2float64(i interface{}) (float64, error) {
if v, ok := i.(float64); ok == true {
return v, nil
}
return 0, errors.New("not a 'float64'")
}
func cast2func(i interface{}) (*Func, error) {
if v, ok := i.(*Func); ok == true {
return v, nil
}
return nil, errors.New("not a '*Func'")
}
func NewGrammer(kind GKind_t, expr *Expr, ret float64, grammer *Grammer) (*Grammer, error) {
g := new(Grammer)
g.Kind = kind
g.Expr = expr
g.Ret = ret
g.Grammer = grammer
return g, nil
}
func NewExpr(kind EKind_t, expr *Expr, term *Term) (*Expr, error) {
e := new(Expr)
e.Kind = kind
e.Left = expr
e.Right = term
return e, nil
}
func NewTerm(kind TKind_t, lfactor *Factor, list *List, rfactor *Factor, expr *Expr) (*Term, error) {
t := new(Term)
t.Kind = kind
switch kind {
case IN, NI:
t.Left = lfactor
t.Right = list
case GT, LT, EQ, NE, GE, LE:
t.Left = lfactor
t.Right = rfactor
case MA, NM:
t.Left = lfactor
if v, err := cast2string(rfactor.Value); err != nil {
return t, err
} else {
if t.Right, err = regexp.CompilePOSIX(v); err != nil {
return t, err
}
}
case EXPR:
t.Left = nil
t.Right = expr
}
return t, nil
}
func NewFactor(kind FKind_t, dbl float64, str string, vari string, fn *Func) (*Factor, error) {
f := new(Factor)
f.Kind = kind
switch kind {
case DOUBLE:
f.Value = dbl
case STRING:
f.Value = str
case VARIABLE:
f.Value = vari
case FUNCTION:
f.Value = fn
}
return f, nil
}
func NewFunc(kind FnKind_t, list *List) (*Func, error) {
fn := new(Func)
fn.Kind = kind
fn.List = list
return fn, nil
}
func NewList(factor *Factor, next *List) (*List, error) {
l := new(List)
l.Factor = factor
l.Next = next
return l, nil
}
func EvalGrammer(grammer *Grammer, symlist *SymList) (int, error) {
var err error
ret := -1
if grammer == nil {
return 0, nil
}
switch grammer.Kind {
case EGET:
ret, err = EvalExpr(grammer.Expr, symlist)
if err != nil {
return -1, err
}
if ret == 1 {
return int(grammer.Ret), nil
}
return EvalGrammer(grammer.Grammer, symlist)
case DGET:
ret, err = EvalGrammer(grammer.Grammer, symlist)
if err != nil {
return -1, err
}
if ret == 0 {
return int(grammer.Ret), nil
}
return ret, nil
case EEXPR:
ret, err = EvalExpr(grammer.Expr, symlist)
if err != nil {
return -1, err
}
if ret != 0 {
return ret, nil
}
return EvalGrammer(grammer.Grammer, symlist)
}
return -1, errors.New(fmt.Sprintf("grammer operator '%s' not supported", gkind2str(grammer.Kind)))
}
func EvalExpr(expr *Expr, symlist *SymList) (int, error) {
var err error
var left int
if expr == nil {
return -1, errors.New("expr with invalid parameter")
}
switch expr.Kind {
case AND:
if left, err = EvalExpr(expr.Left, symlist); err != nil {
return -1, err
}
if left <= 0 {
return left, nil
}
return EvalTerm((*Term)(expr.Right), symlist)
case OR:
if left, err = EvalExpr(expr.Left, symlist); err != nil {
return -1, err
}
if left != 0 {
return left, nil
}
return EvalTerm((*Term)(expr.Right), symlist)
case TERM:
return EvalTerm((*Term)(expr.Right), symlist)
}
return -1, errors.New(fmt.Sprintf("expr operator '%s' not supported", ekind2str(expr.Kind)))
}
func EvalTerm(term *Term, symlist *SymList) (int, error) {
if term == nil {
return -1, errors.New("term with invalid parameter")
}
switch term.Kind {
case IN, NI:
switch v := term.Right.(type) {
case *List:
return EvalList(term.Kind, term.Left, v, symlist)
}
case GT, LT, EQ, NE, GE, LE:
switch v := term.Right.(type) {
case *Factor:
return EvalCmp(term.Kind, term.Left, v, symlist)
}
case MA, NM:
switch v := term.Right.(type) {
case *regexp.Regexp:
return EvalRegex(term.Kind, term.Left, v, symlist)
}
case EXPR:
switch v := term.Right.(type) {
case *Expr:
return EvalExpr(v, symlist)
}
}
return -1, errors.New(fmt.Sprintf("term with invalid kind '%s'", tkind2str(term.Kind)))
}
func EvalList(kind TKind_t, factor *Factor, list *List, symlist *SymList) (int, error) {
found := false
for p := list; p != nil; p = p.Next {
if rc, err := EvalCmp(EQ, factor, p.Factor, symlist); err != nil {
return -1, err
} else if rc > 0 {
found = true
break
}
}
if kind == IN {
return bool2int(found), nil
}
return bool2int(!found), nil
}
func EvalRegex(kind TKind_t, lfactor *Factor, regex *regexp.Regexp, symlist *SymList) (int, error) {
if lfactor == nil || regex == nil {
return -1, errors.New("regexp with invalid parameter")
}
err := errors.New("regex match: parameter should be 'string'")
lv := lfactor
if lfactor.Kind == VARIABLE {
if v, err := cast2string(lfactor.Value); err != nil {
return -1, err
} else if lv, err = SymbolLookup(symlist, v); err != nil {
return -1, err
}
} else if lfactor.Kind == FUNCTION {
if v, ok := lfactor.Value.(*Func); ok != true {
return -1, err
} else {
var value *Factor
value, err := EvalFunc(v, symlist)
if err != nil {
return -1, err
}
if value.Kind != STRING {
return -1, errors.New("func ret should be 'string'")
}
lv = value
}
}
if lv.Kind != STRING {
return -1, err
}
if v, err := cast2string(lv.Value); err == nil {
rc := regex.MatchString(v)
return bool2int((kind == MA && rc == true) ||
(kind == NM && rc == false)), nil
}
return -1, errors.New("left value has invalid type")
}
func EvalLen(list *List, symlist *SymList) (*Factor, error) {
if list == nil || list.Factor == nil {
return nil, errors.New("len() with invalid parameter")
}
switch list.Factor.Kind {
case STRING:
if v, err := cast2string(list.Factor.Value); err != nil {
return nil, err
} else {
return NewFactor(DOUBLE, float64(len(v)), "", "", nil)
}
case VARIABLE:
if v, err := cast2string(list.Factor.Value); err != nil {
return nil, err
} else {
var value *Factor
if value, err = SymbolLookup(symlist, v); err != nil {
return nil, err
}
if value.Kind != STRING {
return nil, err
}
if v2, err := cast2string(value.Value); err != nil {
return nil, err
} else {
return NewFactor(DOUBLE, float64(len(v2)), "", "", nil)
}
}
case FUNCTION:
if v, ok := list.Factor.Value.(*Func); ok != true {
return nil, errors.New("len(): parameter should be 'Func'")
} else {
var value *Factor
value, err := EvalFunc(v, symlist)
if err != nil {
return nil, err
}
if value.Kind != STRING {
return nil, errors.New("func ret should be 'string'")
}
if v2, err := cast2string(value.Value); err != nil {
return nil, errors.New("func ret should be 'string'")
} else {
return NewFactor(DOUBLE, float64(len(v2)), "", "", nil)
}
}
}
return nil, errors.New(fmt.Sprintf("len with invalid kind '%s'", fkind2str(list.Factor.Kind)))
}
func EvalMD5(list *List, symlist *SymList) (*Factor, error) {
if list == nil || list.Factor == nil {
return nil, errors.New("md5() with invalid parameter")
}
deferr := errors.New("md5() parameter should be 'string'")
h := md5.New()
for p := list; p != nil; p = p.Next {
switch p.Factor.Kind {
case STRING:
if v, err := cast2string(p.Factor.Value); err != nil {
return nil, err
} else {
io.WriteString(h, v)
}
case VARIABLE:
if v, err := cast2string(p.Factor.Value); err != nil {
return nil, err
} else {
var value *Factor
value, err := SymbolLookup(symlist, v)
if err != nil {
return nil, err
}
if value.Kind != STRING {
return nil, deferr
}
if v2, err := cast2string(value.Value); err != nil {
return nil, err
} else {
io.WriteString(h, v2)
}
}
case FUNCTION:
if v, err := cast2func(p.Factor.Value); err != nil {
return nil, err
} else {
var value *Factor
if value, err = EvalFunc(v, symlist); err != nil {
return nil, err
}
if value.Kind != STRING {
return nil, deferr
}
if v2, err := cast2string(value.Value); err != nil {
return nil, err
} else {
io.WriteString(h, v2)
}
}
}
}
return NewFactor(STRING, 0, fmt.Sprintf("%x", h.Sum(nil)), "", nil)
}
func EvalCount(symlist *SymList) (*Factor, error) {
count := 0
for p := symlist; p != nil; p = p.Next {
count += 1
}
return NewFactor(DOUBLE, float64(count), "", "", nil)
}
func EvalAtoi(list *List, symlist *SymList) (*Factor, error) {
if list == nil || list.Factor == nil {
return nil, errors.New("atoi() with invalid parameter")
}
deferr := errors.New("atoi() parameter should be 'string'")
switch list.Factor.Kind {
case STRING:
if v, err := cast2string(list.Factor.Value); err != nil {
return nil, err
} else {
if dbl, err := strconv.ParseFloat(v, 64); err != nil {
return nil, err
} else {
return NewFactor(DOUBLE, dbl, "", "", nil)
}
}
case VARIABLE:
if v, err := cast2string(list.Factor.Value); err != nil {
return nil, err
} else {
var value *Factor
if value, err = SymbolLookup(symlist, v); err != nil {
return nil, err
}
if value.Kind != STRING {
return nil, deferr
}
if v2, err := cast2string(value.Value); err != nil {
return nil, err
} else {
if dbl, err := strconv.ParseFloat(v2, 64); err != nil {
return nil, err
} else {
return NewFactor(DOUBLE, dbl, "", "", nil)
}
}
}
case FUNCTION:
if v, err := cast2func(list.Factor.Value); err != nil {
return nil, err
} else {
var value *Factor
if value, err = EvalFunc(v, symlist); err != nil {
return nil, err
}
if value.Kind != STRING {
return nil, deferr
}
if v2, err := cast2string(value.Value); err != nil {
return nil, err
} else {
if dbl, err := strconv.ParseFloat(v2, 64); err != nil {
return nil, err
} else {
return NewFactor(DOUBLE, dbl, "", "", nil)
}
}
}
}
return nil, errors.New(fmt.Sprintf("atoi with invalid kind '%s'", fkind2str(list.Factor.Kind)))
}
func EvalItoa(list *List, symlist *SymList) (*Factor, error) {
if list == nil || symlist == nil {
return nil, errors.New("itoa() with invalid parameter")
}
deferr := errors.New("itoa() parameter should be 'double'")
switch list.Factor.Kind {
case DOUBLE:
if v, err := cast2float64(list.Factor.Value); err != nil {
return nil, err
} else {
return NewFactor(STRING, 0, fmt.Sprintf("%f", v), "", nil)
}
case VARIABLE:
if v, err := cast2string(list.Factor.Value); err != nil {
return nil, err
} else {
var value *Factor
if value, err = SymbolLookup(symlist, v); err != nil {
return nil, err
}
if value.Kind != DOUBLE {
return nil, deferr
}
if v2, err := cast2float64(value.Value); err != nil {
return nil, err
} else {
return NewFactor(STRING, 0, fmt.Sprintf("%.2f", v2), "", nil)
}
}
case FUNCTION:
var value *Factor
if v, err := cast2func(list.Factor.Value); err != nil {
return nil, err
} else {
if value, err = EvalFunc(v, symlist); err != nil {
return nil, err
}
if value.Kind != DOUBLE {
return nil, deferr
}
if v2, err := cast2float64(value.Value); err != nil {
return nil, err
} else {
return NewFactor(STRING, 0, fmt.Sprintf("%.2f", v2), "", nil)
}
}
}
return nil, errors.New(fmt.Sprintf("itoa with invalid kind '%s'", fkind2str(list.Factor.Kind)))
}
func EvalFunc(fn *Func, symlist *SymList) (*Factor, error) {
if fn == nil || symlist == nil {
return nil, errors.New(fmt.Sprintf("func '%s' with invalid parameter", fnkind2str(fn.Kind)))
}
switch fn.Kind {
case LEN:
return EvalLen(fn.List, symlist)
case MD5:
return EvalMD5(fn.List, symlist)
case COUNT:
return EvalCount(symlist)
case ATOI:
return EvalAtoi(fn.List, symlist)
case ITOA:
return EvalItoa(fn.List, symlist)
}
return nil, errors.New(fmt.Sprintf("function '%s' not supported", fnkind2str(fn.Kind)))
}
func EvalCmp(kind TKind_t, lfactor, rfactor *Factor, symlist *SymList) (int, error) {
lv := lfactor
rv := rfactor
if lfactor.Kind == VARIABLE {
if v, err := cast2string(lfactor.Value); err != nil {
return -1, err
} else {
if lv, err = SymbolLookup(symlist, v); err != nil {
return -1, err
}
}
} else if lfactor.Kind == FUNCTION {
if v, err := cast2func(lfactor.Value); err != nil {
return -1, err
} else {
if lv, err = EvalFunc(v, symlist); err != nil {
return -1, err
}
}
}
if rfactor.Kind == VARIABLE {
if v, err := cast2string(rfactor.Value); err != nil {
return -1, err
} else {
if rv, err = SymbolLookup(symlist, v); err != nil {
return -1, err
}
}
} else if rfactor.Kind == FUNCTION {
if v, err := cast2func(rfactor.Value); err != nil {
return -1, err
} else {
if rv, err = EvalFunc(v, symlist); err != nil {
return -1, err
}
}
}
if lv.Kind != rv.Kind {
return 0, nil // just ignore
}
if lv.Kind == DOUBLE {
if v1, err := cast2float64(lv.Value); err != nil {
return -1, err
} else {
if v2, err := cast2float64(rv.Value); err != nil {
return -1, err
} else {
return CmpDbl(kind, v1, v2)
}
}
} else if lv.Kind == STRING {
if v1, err := cast2string(lv.Value); err != nil {
return -1, err
} else {
if v2, err := cast2string(rv.Value); err != nil {
return -1, err
} else {
return CmpStr(kind, v1, v2)
}
}
}
return -1, errors.New(fmt.Sprintf("operator '%s' not supported", tkind2str(kind)))
}
func CmpDbl(kind TKind_t, d1, d2 float64) (int, error) {
switch kind {
case GT:
return bool2int(d1 > d2), nil
case LT:
return bool2int(d1 < d2), nil
case EQ:
return bool2int(math.Abs(d1-d2) < 0.001), nil
case NE:
return bool2int(math.Abs(d1-d2) > 0.001), nil
case GE:
return bool2int(d1 > d2 || math.Abs(d1-d2) < 0.001), nil
case LE:
return bool2int(d1 < d2 || math.Abs(d1-d2) < 0.001), nil
}
return -1, errors.New(fmt.Sprintf("double operator '%s' not supported", tkind2str(kind)))
}
func CmpStr(kind TKind_t, s1, s2 string) (int, error) {
switch kind {
case GT:
return bool2int(s1 > s2), nil
case LT:
return bool2int(s1 < s2), nil
case GE:
return bool2int(s1 >= s2), nil
case LE:
return bool2int(s1 <= s2), nil
case EQ:
return bool2int(s1 == s2), nil
case NE:
return bool2int(s1 != s2), nil
}
return -1, errors.New(fmt.Sprintf("string operator '%s' not supported", tkind2str(kind)))
}