/
arith.go
221 lines (212 loc) · 4.3 KB
/
arith.go
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// Copyright (c) 2017, Daniel Martí <mvdan@mvdan.cc>
// See LICENSE for licensing information
package expand
import (
"fmt"
"strconv"
"strings"
"mvdan.cc/sh/v3/syntax"
)
func Arithm(cfg *Config, expr syntax.ArithmExpr) (int, error) {
switch x := expr.(type) {
case *syntax.Word:
str, err := Literal(cfg, x)
if err != nil {
return 0, err
}
// recursively fetch vars
i := 0
for syntax.ValidName(str) {
val := cfg.envGet(str)
if val == "" {
break
}
if i++; i >= maxNameRefDepth {
break
}
str = val
}
// default to 0
return atoi(str), nil
case *syntax.ParenArithm:
return Arithm(cfg, x.X)
case *syntax.UnaryArithm:
switch x.Op {
case syntax.Inc, syntax.Dec:
name := x.X.(*syntax.Word).Lit()
old := atoi(cfg.envGet(name))
val := old
if x.Op == syntax.Inc {
val++
} else {
val--
}
if err := cfg.envSet(name, strconv.Itoa(val)); err != nil {
return 0, err
}
if x.Post {
return old, nil
}
return val, nil
}
val, err := Arithm(cfg, x.X)
if err != nil {
return 0, err
}
switch x.Op {
case syntax.Not:
return oneIf(val == 0), nil
case syntax.BitNegation:
return ^val, nil
case syntax.Plus:
return val, nil
default: // syntax.Minus
return -val, nil
}
case *syntax.BinaryArithm:
switch x.Op {
case syntax.Assgn, syntax.AddAssgn, syntax.SubAssgn,
syntax.MulAssgn, syntax.QuoAssgn, syntax.RemAssgn,
syntax.AndAssgn, syntax.OrAssgn, syntax.XorAssgn,
syntax.ShlAssgn, syntax.ShrAssgn:
return cfg.assgnArit(x)
case syntax.TernQuest: // TernColon can't happen here
cond, err := Arithm(cfg, x.X)
if err != nil {
return 0, err
}
b2 := x.Y.(*syntax.BinaryArithm) // must have Op==TernColon
if cond == 1 {
return Arithm(cfg, b2.X)
}
return Arithm(cfg, b2.Y)
}
left, err := Arithm(cfg, x.X)
if err != nil {
return 0, err
}
right, err := Arithm(cfg, x.Y)
if err != nil {
return 0, err
}
return binArit(x.Op, left, right)
default:
panic(fmt.Sprintf("unexpected arithm expr: %T", x))
}
}
func oneIf(b bool) int {
if b {
return 1
}
return 0
}
// atoi is like [strconv.Atoi], but it ignores errors and trims whitespace.
func atoi(s string) int {
s = strings.TrimSpace(s)
n, _ := strconv.Atoi(s)
return n
}
func (cfg *Config) assgnArit(b *syntax.BinaryArithm) (int, error) {
name := b.X.(*syntax.Word).Lit()
val := atoi(cfg.envGet(name))
arg, err := Arithm(cfg, b.Y)
if err != nil {
return 0, err
}
switch b.Op {
case syntax.Assgn:
val = arg
case syntax.AddAssgn:
val += arg
case syntax.SubAssgn:
val -= arg
case syntax.MulAssgn:
val *= arg
case syntax.QuoAssgn:
if arg == 0 {
return 0, fmt.Errorf("division by zero")
}
val /= arg
case syntax.RemAssgn:
if arg == 0 {
return 0, fmt.Errorf("division by zero")
}
val %= arg
case syntax.AndAssgn:
val &= arg
case syntax.OrAssgn:
val |= arg
case syntax.XorAssgn:
val ^= arg
case syntax.ShlAssgn:
val <<= uint(arg)
case syntax.ShrAssgn:
val >>= uint(arg)
}
if err := cfg.envSet(name, strconv.Itoa(val)); err != nil {
return 0, err
}
return val, nil
}
func intPow(a, b int) int {
p := 1
for b > 0 {
if b&1 != 0 {
p *= a
}
b >>= 1
a *= a
}
return p
}
func binArit(op syntax.BinAritOperator, x, y int) (int, error) {
switch op {
case syntax.Add:
return x + y, nil
case syntax.Sub:
return x - y, nil
case syntax.Mul:
return x * y, nil
case syntax.Quo:
if y == 0 {
return 0, fmt.Errorf("division by zero")
}
return x / y, nil
case syntax.Rem:
if y == 0 {
return 0, fmt.Errorf("division by zero")
}
return x % y, nil
case syntax.Pow:
return intPow(x, y), nil
case syntax.Eql:
return oneIf(x == y), nil
case syntax.Gtr:
return oneIf(x > y), nil
case syntax.Lss:
return oneIf(x < y), nil
case syntax.Neq:
return oneIf(x != y), nil
case syntax.Leq:
return oneIf(x <= y), nil
case syntax.Geq:
return oneIf(x >= y), nil
case syntax.And:
return x & y, nil
case syntax.Or:
return x | y, nil
case syntax.Xor:
return x ^ y, nil
case syntax.Shr:
return x >> uint(y), nil
case syntax.Shl:
return x << uint(y), nil
case syntax.AndArit:
return oneIf(x != 0 && y != 0), nil
case syntax.OrArit:
return oneIf(x != 0 || y != 0), nil
default: // syntax.Comma
// x is executed but its result discarded
return y, nil
}
}