// Copyright (c) 2013-2014 The btcsuite developers
// Use of this source code is governed by an ISC
// license that can be found in the LICENSE file.

// +build !windows,!plan9

package limits

import (
	"fmt"
	"syscall"
)

const (
	fileLimitWant = 2048 * 12
	fileLimitMin  = 2048 * 8
)

// SetLimits raises some process limits to values which allow btcd and
// associated utilities to run.
func SetLimits() error {
	var rLimit syscall.Rlimit

	err := syscall.Getrlimit(syscall.RLIMIT_NOFILE, &rLimit)
	if err != nil {
		return err
	}
	if rLimit.Cur > fileLimitWant {
		return nil
	}
	if rLimit.Max < fileLimitMin {
		err = fmt.Errorf("need at least %v file descriptors",
			fileLimitMin)
		return err
	}
	if rLimit.Max < fileLimitWant {
		rLimit.Cur = rLimit.Max
	} else {
		rLimit.Cur = fileLimitWant
	}
	err = syscall.Setrlimit(syscall.RLIMIT_NOFILE, &rLimit)
	if err != nil {
		// try min value
		rLimit.Cur = fileLimitMin
		err = syscall.Setrlimit(syscall.RLIMIT_NOFILE, &rLimit)
		if err != nil {
			return err
		}
	}

	return nil
}