/
numbers.go
139 lines (104 loc) · 3.01 KB
/
numbers.go
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// Copyright 2020 The OPA Authors. All rights reserved.
// Use of this source code is governed by an Apache2
// license that can be found in the LICENSE file.
package topdown
import (
"fmt"
"math/big"
"github.com/open-policy-agent/opa/ast"
"github.com/open-policy-agent/opa/topdown/builtins"
)
type randIntCachingKey string
var one = big.NewInt(1)
func builtinNumbersRange(bctx BuiltinContext, operands []*ast.Term, iter func(*ast.Term) error) error {
x, err := builtins.BigIntOperand(operands[0].Value, 1)
if err != nil {
return err
}
y, err := builtins.BigIntOperand(operands[1].Value, 2)
if err != nil {
return err
}
ast, err := generateRange(bctx, x, y, one, "numbers.range")
if err != nil {
return err
}
return iter(ast)
}
func builtinNumbersRangeStep(bctx BuiltinContext, operands []*ast.Term, iter func(*ast.Term) error) error {
x, err := builtins.BigIntOperand(operands[0].Value, 1)
if err != nil {
return err
}
y, err := builtins.BigIntOperand(operands[1].Value, 2)
if err != nil {
return err
}
step, err := builtins.BigIntOperand(operands[2].Value, 3)
if err != nil {
return err
}
if step.Cmp(big.NewInt(0)) <= 0 {
return fmt.Errorf("numbers.range_step: step must be a positive number above zero")
}
ast, err := generateRange(bctx, x, y, step, "numbers.range_step")
if err != nil {
return err
}
return iter(ast)
}
func generateRange(bctx BuiltinContext, x *big.Int, y *big.Int, step *big.Int, funcName string) (*ast.Term, error) {
cmp := x.Cmp(y)
comp := func(i *big.Int, y *big.Int) bool { return i.Cmp(y) <= 0 }
iter := func(i *big.Int) *big.Int { return i.Add(i, step) }
if cmp > 0 {
comp = func(i *big.Int, y *big.Int) bool { return i.Cmp(y) >= 0 }
iter = func(i *big.Int) *big.Int { return i.Sub(i, step) }
}
result := ast.NewArray()
haltErr := Halt{
Err: &Error{
Code: CancelErr,
Message: fmt.Sprintf("%s: timed out before generating all numbers in range", funcName),
},
}
for i := new(big.Int).Set(x); comp(i, y); i = iter(i) {
if bctx.Cancel != nil && bctx.Cancel.Cancelled() {
return nil, haltErr
}
result = result.Append(ast.NewTerm(builtins.IntToNumber(i)))
}
return ast.NewTerm(result), nil
}
func builtinRandIntn(bctx BuiltinContext, operands []*ast.Term, iter func(*ast.Term) error) error {
strOp, err := builtins.StringOperand(operands[0].Value, 1)
if err != nil {
return err
}
n, err := builtins.IntOperand(operands[1].Value, 2)
if err != nil {
return err
}
if n == 0 {
return iter(ast.IntNumberTerm(0))
}
if n < 0 {
n = -n
}
var key = randIntCachingKey(fmt.Sprintf("%s-%d", strOp, n))
if val, ok := bctx.Cache.Get(key); ok {
return iter(val.(*ast.Term))
}
r, err := bctx.Rand()
if err != nil {
return err
}
result := ast.IntNumberTerm(r.Intn(n))
bctx.Cache.Put(key, result)
return iter(result)
}
func init() {
RegisterBuiltinFunc(ast.NumbersRange.Name, builtinNumbersRange)
RegisterBuiltinFunc(ast.NumbersRangeStep.Name, builtinNumbersRangeStep)
RegisterBuiltinFunc(ast.RandIntn.Name, builtinRandIntn)
}