Crash demonstration for go-curl

curl-crash.go

package main

import (
	"github.com/andelf/go-curl"
	"log"
	"sync"
	"time"
)

const maxRequests = 100

var mutex = &sync.Mutex{}
var nActiveRequests int

func GetURL(url string, maxBytes int, timeout int) (result []byte, err error) {
	mutex.Lock()
	nActiveRequests++
	mutex.Unlock()

	easy := curl.EasyInit()
	defer easy.Cleanup()

	easy.Setopt(curl.OPT_URL, url)
	easy.Setopt(curl.OPT_CONNECTTIMEOUT, timeout)
	easy.Setopt(curl.OPT_TIMEOUT, timeout)
	easy.Setopt(curl.OPT_FOLLOWLOCATION, true)
	easy.Setopt(curl.OPT_MAXREDIRS, 3)
	easy.Setopt(curl.OPT_NOSIGNAL, 1)
	easy.Setopt(curl.OPT_VERBOSE, false)

	result = []byte{}

	// make a callback function
	writeFunc := func(buf []byte, userdata interface{}) bool {
		result = append(result, buf...)
		//log.Printf("DEBUG: size=> %v", len(result))
		//log.Printf("DEBUG: content=> %v", string(result))
		//log.Printf("DEBUG: userdata=> %v", userdata)
		if len(result) >= maxBytes {
			return false
		}
		return true
	}

	easy.Setopt(curl.OPT_WRITEFUNCTION, writeFunc)
	easy.Setopt(curl.OPT_NOPROGRESS, false)

	easy.Setopt(curl.OPT_PROGRESSFUNCTION, func(dltotal, dlnow, ultotal, ulnow float64, userdata interface{}) bool {
		//log.Printf("OPT_PROGRESSFUNCTION: dltotal %v dlnow %v ultotal %v ulnow %v", dltotal, dlnow, ultotal, ulnow)
		if int(dltotal) >= maxBytes {
			return false
		}
		return true
	})

	err = easy.Perform()
	if err != nil {
		if v, ok := err.(curl.CurlError); ok && v == curl.E_ABORTED_BY_CALLBACK {
			err = nil
		}
	}
	if err != nil {
		log.Printf("GetURL: %v", err)
	}

	mutex.Lock()
	nActiveRequests--
	mutex.Unlock()

	return result, err
}

func main() {
	var n int
	for {
		mutex.Lock()
		n = nActiveRequests
		mutex.Unlock()

		if n < maxRequests {
			go GetURL("https://assets-cdn.github.com/images/modules/site/universe-logo.png", 16, 8)
		} else {
			time.Sleep(20 * time.Millisecond)
		}

	}
}