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Testing if hostname is numeric IPv4

Posted on August 31, 2010

I had to resort this hack when testing a hybrid web/mobile site which uses site hostname based device discrimination. In production mode we can have m.yoursite.com and www.yoursite.com hostnames. However, when running the site locally, on your development computer and in LAN this does not work very well: one cannot spoof hostnames for web browsers in devices like iPhone/iPod/other mobile phone unless you install a DNS server. And installing a DNS server for LAN is something you don’t want to do…

So, I figured out that I can use  hostname spoofing on desktop computers (/etc/hosts file) and I always access the site via numeric IP (IPv4 over ethernet) when testing over WLAN on mobile devices.

  • The site is rendered in web mode when it is being accessed via textual hostname (localhost, yourpcname)
  • The site is rendered in mobile mode when it is being accessed via IPv4 numeric hostname (127.0.0.1, 196.168.200.1)

And,… dadaa,… here is my magical code to test whether hostname is numeric IPv4. I couldn’t find a ready function from Python standard library

import re

ipv4_regex_source = "^(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)$"
ipv4_regex = re.compile(ipv4_regex_source)

def is_numeric_ipv4(str):
    """

http://answers.oreilly.com/topic/318-how-to-match-ipv4-addresses-with-regular-expressions/

    @param str: Hostname as a string.

    @return: True if the given string is numeric IPv4 address
    """
    # ^(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)$
    return ipv4_regex.match(str)

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UIScrollView & setContentOffset random scrolling on iOS 4

Posted on August 30, 2010

We encountered a nasty bug with UIScrollView while porting app to iOS 4. The following code worked just fine on old iPhone versions:

// Update view with new content
[self updateContent:...]

// We want the view to be on top every time the it is shown
[scrollView setContentOffset:CGPointMake(0,0) animated:NO];

// And set the correct size to enable scrolling.
// contentHeight is updated when setting the content of subviews.
[scrollView setContentSize:CGSizeMake(self.view.frame.size.width, contentheight)];

No problems. But on iOS 4 the UIScrollView decided to do something fancy and scroll to random position depending on where it was left when the view was hidden the last time. After spending expensive manpower to solve the issue by trying numerous ways to tell the scrollView to go to top using setContentOffset, the final solution was simple yet very different what one might think: to fix this we had to set the contentSize to zero before updating any of the content.

// Need to do this on iOS 4 or the view scrolls to random position
[scrollView setContentSize:CGSizeMake(0,0)];

// Update view with new content
[self updateContent:...]

// We want the view to be on top every time it is shown
[scrollView setContentOffset:CGPointMake(0,0) animated:NO];

// And set the correct size to enable scrolling.
// contentHeight is updated when setting the content of subviews.
[scrollView setContentSize:CGSizeMake(self.view.frame.size.width, contentheight)];

Hopefully there is more logical way to update scrollview’s content without being scrolled around.

Xcode and iPhone simulator: The application won’t launch

Posted on August 26, 2010

This is another migration issue from iOS 3.x to iOS 4.x projects.

The application does not launch in XCode when running Simulator – Debug. Instead it dies (SIGABRT) before entering main().

#0     0x91a02ef6 in __kill
#1     0x91a02ee8 in kill$UNIX2003
#2     0x91a9562d in raise
#3     0x91aab6e4 in abort
#4     0x0245e8c9 in __springboard_unimplemented
#5     0x0246d6b2 in mcount
#6     0x00002298 in main at main.m:11

The answer lies here. mcount() function is profiling function. Profiling is available only on iPhone device build. The setting “Generate Profile Code” somehow gets into foobar state when you migrate the project from older XCode. Note the setting is present under both Project and Target settings so you might need to fix it under the both sections.

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CodeSign error: a valid provisioning profile is required problem in XCode

Posted on August 17, 2010

The above error pop-ups when you try to build iPhone application for the device. It means that the provision name in XCode project settings does not match .provision file installed in XCode Organizer (device manager). Usually this happens when you have downloaded XCode project created by someone else.

It should be possible just to go to XCode -> Project -> Project settings and chose a valid code signing profile (Code signing -> Code signing identity drop down should have been populated from the choices available in XCode organizer). However, it seems that there is a bug and always changing this setting does not have effect. Based on reports, it looks XCode project setting updater is confused about something and does not update the setting correctly.

The hardcode workaround is to edit your XCode project .xcodeproj file manually. You do not need to close down XCode for this (it will automatically ask to reload after the file is saved). You may see duplicate entries of  XCBuildConfiguration. You need to hunt down one with old (incorrect) values and manually copy-paste in correct values. You can get the correct values from XCode organizer.

For example, I had to edit in :

	CODE_SIGN_IDENTITY = "iPhone Developer: Mikko Ohtamaa (XXXYYY)";
	"CODE_SIGN_IDENTITY[sdk=iphoneos*]" = "iPhone Developer: Mikko Ohtamaa (XXXXYYY)";
...
                PROVISIONING_PROFILE = "7572BAC6-4F0C-46D3-B96F-XXXXXYYY";
	"PROVISIONING_PROFILE[sdk=iphoneos*]" = "7572BAC6-4F0C-46D3-B96F-XXXXXYYYY";

manually to the file, replacing the old values for these settings. Note that values may be in many lines.

Hope this helps someone.

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