MAC OS X (Cocoa) Libs. ASCII is a 7-bit code that maps the English alphabet, the digits 0-9, and some punctuation and control characters into the integers 0 to 127. Objective-C example to base-64 encode and decode a string. What I want to focus on in this article is how Objective C encodings work. Use strcmp to compare the size by ASCII value. Use @ encode (Atype) to return the C string of this type, represented by const char. For this reason, if the active code page is an ANSI code page, encoding and decoding data using the default code page returned by Encoding.GetEncoding(0) is not recommended. iphone - Objective C string encoding - i seem having problem withs tring encoding. The @encode() compiler directive generates an Objective-C type code from a type expression that can be used as the first argument of encodeValueOfObjCType:at:.See “Type Encodings” in The Objective-C Programming Language for more information.. Decoding an Object. The Objective C runtime considers C++ pointers and C++ references to be the same thing as far as encodings are concerned. NSString is one the most commonly used classes that is used for storing strings and texts. For example, the following code snippet creates a new Objective C class at runtime called “MyClass” which overrides the -description method to return @"Hello" . , and that there are more than a few “historical/compatibility” issues with encodings. (Objective-C) StringBuilder Encode Charset. This returns a const char * using UTF8 string encoding. In fact I started digging into this because I found a C++ class that we had wrapped in an Objective C object in our code that was adding 39.4K worth of data to the runtime. Nesting classes works the same as nesting structs. Subsequently, many different 8-bit encodings were created to make computers work with language… Line 10 of the code snippet above has. Computers cannot handle text directly; they can only deal with numbers. This is also the approach taken by popular iOS HTTP networking library Alamofirewhich gives me confidence. You could have a single struct that wraps all of your C++ types. Dim ascii As Encoding = Encoding.ASCII Dim unicode As Encoding = Encoding.Unicode ' Convert the string … uppercaseLetterCharacterSet − Returns a character set containing the characters in the categories of Uppercase Letters and Titlecase Letters. Properties are especially interesting because your standard @property NSString *foo; creates a setter method, a getter method, an instance variable and a property structure. What happens if we start nesting structs such as: which is starting to get a little more verbose, but still doesn’t seem worth writing this article about. In most cases I use std::unique_ptr to own the pointer. Objective C is a dynamically typed programming language that allows full runtime introspection as well as runtime modification. Interestingly if you want to save a little space, you can do. which is adding a method -description to myClass that has an implementation defined by methodIMP, but what is the "@@:"? When creating an NSString object from a UTF-16-encoded string (or a byte stream interpreted as UTF-16), if the byte order is not otherwise specified, NSString assumes that the UTF-16 characters are big-endian, unless there is a BOM (byte-order mark), in which case the BOM dictates the byte order. whitespaceCharacterSet − Returns a character set containing only the in-line whitespace characters space (U+0020) and tab (U+0009). Data compression is always useful for encoding information using fewer bits than the original representation it would use. Method blah = class_getInstanceMethod([NSObject class]. The codecs module defines a set of base classes which define the interfaces for working with codec objects, and can also be used as the basis for custom codec implementations. Chilkat Objective-C Library Downloads. Returns Int32. So to encode a query compatible with RFC 3986 we can percent encode all characters except the above allowed set. How to encode the string in android? encodes as {aStruct=iq@} . This means that you can examine, modify, and create classes, methods… The second @ represents self and the : represents _cmd. Objective C is a dynamically typed programming language that allows full runtime introspection as well as runtime modification. That’s over 1KB (1242 bytes to be exact) of encoding for the one type. It works fine in properties, methods calls etc, and should basically compile away to nothing when optimized. According to the documentation for class_addMethod it is: which is nice, but you need to look in the “Objective-C Runtime Programming Guide” to find some actual documentation about these characters. Since they don’t appear to be documented anywhere but the sources, here is the encoding characters for properties: So aside from showing that properties may add some bloat to your application, and that encodings are a relatively arcane historical feature of Objective C, why do we care about encodings? To represent text (a string of characters) as (a string of) numbers in a computer, we specify a mapping from characters into numbers. Chilkat Objective-C Library Downloads. C# program to check for URL in a String I made it a struct (instead of a class) so that myMap was public by default. (Objective-C) SCP Download/Upload Binary Files as Encoded Strings. For example usingstd::unique_ptr for our type above expands to. Now when we compile and run the program, we will get the following result. We can deduce that this is a method that returns a BOOL, has a stack size of 44 (8 for self + 8 for _cmd + 8 for url + 4 for useAuxiliaryFile + 8 for enc + 8 for error). You should copy the C string or use get CString: max Length: encoding: if it needs to store the C string beyond this time. Digging into the Objective C Runtime sources we find that the first number in a method is the stack size of arguments to the method and the numbers after the argument types are offsets in memory to the values represented by the types. - (BOOL)writeToURL:(NSURL *)url atomically:(BOOL)useAuxiliaryFile encoding:(NSStringEncoding)enc error:(NSError **)error; {ObjCType=#{CppType={map, std::__1::basic_string, std::__1::less >, std::__1::allocator, std::__1::basic_string > > >={__tree, std::__1::basic_string >, std::__1::__map_value_compare, std::__1::__value_type, std::__1::basic_string >, std::__1::less >, true>, std::__1::allocator, std::__1::basic_string > > >=^{__tree_end_node *>}{__compressed_pair *>, std::__1::allocator, std::__1::basic_string >, void *> > >={__tree_end_node *>=^{__tree_node_base}}}{__compressed_pair, std::__1::__value_type, std::__1::basic_string >, std::__1::less >, true> >=Q}}}}}, {ObjCType=#{unique_ptr >={__compressed_pair >=^{CppType}}}}, a lot of C++ wisdom on how to pass around pointers, https://bugs.llvm.org/show_bug.cgi?id=39888, How to secure Microservices on AWS with Cognito, API Gateway, and Lambda, Performing Optical Character Recognition with Python and Pytesseract using Anaconda, The Fascinating and Hidden World of the Modern Technical Manuals, Conditional imports across Flutter and Web, Enrichment Pipeline Patterns using Apache Beam, Ngrok: Make Your Localhost Accessible to Anyone. for specific types would be a useful optimization (Found this bug which seems to be appropriate, and apparently came up with a similar solution to mine). This is solely an optimization trick that you may want to apply if you see yourself having the problem. iOS Libs. Examples. How to get parameters from a URL string in PHP? You may also want to track https://bugs.llvm.org/show_bug.cgi?id=39888 which is a clang tidy check for watching for large Objective C encodings. whitespaceAndNewlineCharacterSet − Returns a character set containing Unicode General Category Z*, U000A ~ U000D, and U0085. Demonstrates the importance of the charset argument when encoding/decoding. You are fine to pass the naked type to C/C++ functions of course . illegalCharacterSet − Returns a character set containing values in the category of Non-Characters or that have not yet been defined in version 3.2 of the Unicode standard. capitalizedLetterCharacterSet − Returns a character set containing the characters in the category of Titlecase Letters. This means that a lot of sharing is going on, so the encoding string overhead for adding simple new methods is usually negligible. Remarks. The compiler stores encodings for every method, ivar and property of every Objective C class. For example, @ encode (INT) returns I; @ encode (float) returns F. Then, the const char * returned by the objctype method in nsvalue is okay with the comparison above. The number of encoded bytes. objective-c - example - objective c base64 encode string How to Base64 encoding on the iPhone (6) reference Standard C struct encoding by itself is relatively benign. The ANSI code pages can be different on different computers and can change on a single computer, leading to data corruption. The encoding mode keyword "json" was added in Chilkat v9.5.0.66 to provide the ability to escape and unescape JSON strings. As a side note, remember that the runtime also records strings for the method names and instance variable names so you also get foo, setFoo:, and _foo, and that since the language is dynamic, none of this can be dead-stripped by the linker. Note that since the name of the property is encoded in the property string, there is much less sharing going on for properties unless you happen to have the exact same name and exact same type for a lot of properties in different classes. Dim ascii As Encoding = Encoding.ASCII Dim unicode As Encoding = Encoding.Unicode ' Convert the string … Whoa. using the SCP protocol (Secure Copy Protocol over SSH). For files that are smaller than 2,048 bytes, it reads the contents of the entire file into a byte array and calls the GetString(Byte[]) method to perform the decoding. Unfortunately the table of encodings is more than a bit out of date (ex: How are block pointers encoded?) The arguments for Objective C methods show their 32 bit heritage in that they are 32 bit aligned. You can think of String as an artisanal enum, hand-crafted using traditional bit-twiddling techniques in order to produce compact and efficientcode. #import #import // This example assumes the Chilkat API to … symbolCharacterSet − Returns a character set containing the characters in the category of Symbols. punctuationCharacterSet − Returns a character set containing the characters in the category of Punctuation. @encode, one of the @ Compiler Directives, returns a C string that encodes the internal representation of a given type (e.g., @encode(int) → i), similar to the ANSI C typeof operator. Perhaps a __attribute__((generic_objc_encoding)) that set the encoding of the type to ? Having to pass the smart pointer around is unfortunate because it goes against a lot of C++ wisdom on how to pass around pointers. Here is the set of methods available in NSCharacterSet which represent the various character sets. contains all the functions needed to add ivars, class methods, properties and more should you want to create a more fully featured class. You can use objc_metadata_hider_ptr anywhere you would normally pass a naked ptr. Using this algorithm, it could send about 256 characters per message (typically 160 characters per message) through the same 7-bit GSM network. Note that as far as the runtime is concerned, there is zero difference between ivars and properties declared in @interface declarations and @implementation declarations. I doubt the operating system is doing anything interesting with 5K worth of C++ template spew for an instance variable other than knowing that it is there. If you want to know more about NSString, please refer NSString in Objective-C strings.. As mentioned earlier, NSCharacterSet represents various groupings of characters … letterCharacterSet − Returns a character set containing the characters in the categories Letters and Marks. Something relatively simple like a std::map of std::string to std::string. You may be surprised. It's just an example of using NSCharacterSet. and then wrapping that in a C++ smart ptr. This is called an encoding. but what about the numbers? In fact all methods that return void and take a single id argument will share the same encoding string (simple getters), as will all methods that return a single id and have zero arguments (simple setters). Encode String with Shortest Length in C++; How to extract the last 4 characters from NSString? objective-c documentation: Encoding and Decoding. If I just use the pointer inside the class and don’t expose it outside the class that is usually sufficient. This means four different encoding strings (setter: v24@0:8@16 , getter: @16@0:8, instance variable: @"NSString”, property attributes: T@"NSString",&,V_foo). and it will skip the name encoding and encode as {?=iq@} . Like the strlen() function for C strings, the -length method actually returns the number of words in the NSString, which is usually but not always the number of logical characters in the NSString object. How to replace a character in Objective-C String for iPhone SDK? Next time, we'll continue our dive into Unicode string madness by looking at wide character strings. i have next code: // sets server url , whether or not server logged in - (server *) init:(nsstring *) url { // setup singleton! What happens if we start considering Objective C++? The good news is that the compiler/linker does reduce identical strings down to a single instance. (Objective-C) JSON Escape and Unescape a String. newlineCharacterSet − Returns a character set containing the newline characters. (Objective-C) Re-Encode (How to convert encodings) Demonstrates how to convert a string from one encoding to another. Unfortunately the smart pointer solution doesn’t help us in the case where we want to have a complex template directly in our Objective C class though. How to encode in MySQL? You typically don't need to use the Objective-C runtime library directly when programming in Objective-C. If it didn’t, the first time you accessed the value using self.foo your class would lose ownership of the pointer. If you need a C string, use UTF8String: const char *cString = [string UTF8String]; printf("%s", cString); For the most consistent results, you should use a Unicode encoding, such as UTF-8 … Note. In the cases where I need to pass it outside my object (or I want to pass it around inside my object by naked pointer for some reason) I created the stupidest “smart” pointer ever which I call objc_metadata_hider_ptr. Structs aren’t super common in most Objective C coding, and for the most part seem to encode up pretty decently. The best solution I have found here is an intermediate struct. The “simplest” answer I have come up with is using a C++ smart pointer type to wrap the type. characterSetWithRange − Returns a character set containing characters with Unicode values in a given range. This algorithm was originally implemented for use in an SMS application. There are many applications where the size of information would be critical. The first @ represents the return type. The idea is, this … For example: is still going to blow up in size. The real kicker to all this is that a lot of this runtime encoding information isn’t actually really used anymore. Demonstrates how to upload and download binary files as encoded strings (base64, hex, etc.) self is at offset 0, _cmd is at offset 8, url is at offset 16, useAuxiliaryFile is at offset 24, enc is at offset 28 and error is at offset 36. So all of the NSString* properties in the same mach-o segment (for most cases ‘mach-o segment’ is semantically equivalent to ‘application’, but if you have fat binaries, or multiple frameworks you have multiple segments) will share the same encoding string for their setters, getters and instance variables respectively. so for the real story we need to go to the clang source code for ASTContext::getObjCEncodingForTypeImpl to discover fun things like block pointers are encoded as @? Luckily there is objc_metadata_hider_ref that does…. The best-known character encoding is ASCII. MAC OS X (Cocoa) Libs. class_addMethod(myClass, @selector(description), methodIMP, "@@:"). This means that you can examine, modify, and create classes, methods, instance variables (ivars), properties etc. Note that utf8Data.bytes does not include a terminating null character, which is necessary for C strings. Unfortunately objc_metadata_hider_ptr doesn’t work with C++ references. Prior to Swift 5, string content could be in one of two native storage encodings: UTF-… If you want to know more about NSString, please refer NSString in Objective-C strings. alphanumericCharacterSet − Returns a character set containing the characters in the categories Letters, Marks, and Numbers. Easiest way to look for it is to run strings Foo.app/Foo | grep -e '{‘ and see what pops up. It’s not pretty, but it works. will return @16@0:8. As mentioned earlier, NSCharacterSet represents various groupings of characters that are used by the NSString and NSScanner classes. Section 2.3 of RFC 3986lists the characters that you should not percent encode as they have no special meaning in a URL: Section 3.4 also explains that since a query will often itself include a URL it is preferable to not percent encode the slash ("/") and question mark ("?"). Imports System.Text Class Example Shared Sub Main() Dim unicodeString As String = "This string contains the unicode character Pi (" & ChrW(&H03A0) & ")" ' Create two different encodings. I expect some of those TODOs have existed a long time…. In data communication, the size of data can affect the cost too. Luckily the compiler will prevent you from doing something dumb like declaring a @property with a std::unique_ptr. How to encode a string in JavaScript? and don’t want to pay the runtime price? You can imagine a system where you defined your Objective C classes in a series of structures, and then looped through them to register them with the Objective C runtime at startup. Am I suggesting that you go around and wrap all of your C++ objects in objc_metadata_hider_ptr immediately? iOS Libs. The only difference is visibility as far as the compiler is concerned. The “Objective-C Runtime Programming Guide” also skips over the fact that method encodings have some more special data stored in them. lowercaseLetterCharacterSet − Returns a character set containing the characters in the category of Lowercase Letters. objective-c documentation: Encoding and decoding a string using NSData Base64 We can see in the above program, the punctuations on both sides of the given strings is trimmed. If the data to be converted is available only in sequential blocks (such as data read from a stream) or if the amount of data is so large that it needs to be divided into smaller blocks, you should use the Decoder or the Encoder provided by the GetDecoder method or the GetEncoder method, respectively, of a derived class. characterSetWithCharactersInString − Returns a character set containing the characters in a given string. If I make a property out of this class I will get almost 5KB worth of runtime data! Imports System.Text Class Example Shared Sub Main() Dim unicodeString As String = "This string contains the unicode character Pi (" & ChrW(&H03A0) & ")" ' Create two different encodings. const char *cString = [@"Hello, world" UTF8String]; The following example reads a UTF-8 encoded string from a binary file represented by a FileStream object. Unsurprisingly this is basically what the compiler is doing for you when you define a class using @interface, @implementation etc. Even though the String type is technically a struct, it can exist in many forms. In my 39.4 KB example I referenced above it went down to .2 KB with a simple change to unique_ptr . To get a C string from a string object, you are recommended to use UTF8String. Take a minute to peruse the linked page on ‘Type Encodings’ because it’s a good primer on how encodings work and what the @encode directive does. In this case we have 2 arguments, self and _cmd both of which are 8 byte pointers on a 64 bit system, thus a 16 byte stack size, and offsets of 0 and 8 for the arguments. So what can be done if you want to use Objective C wrappers around C++ code (perhaps to make it available to Swift while we wait for Swift C++ interop?) Most C++ gurus would laugh at this code, but you need objc_metadata_hider_ptr because if you use pass a naked ptr type to any Objective C method you are going to get the type info back in your application. The returned C string is guaranteed to be valid only until either the receiver is freed, or until the current memory is emptied, whichever occurs first. NSString is one the most commonly used classes that is used for storing strings and texts. No. If you glance through you will see a number of structures such as struct objc_class which are for the most part what the compiler is generating for the runtime to register. Foo& and Foo* both end up encoded as ^{Foo={…}}. from NSString, we get a method encoding of c44@0:8@16c24Q28^@36. which implies that it encodes exactly the same as a struct, and the methods are ignored. It was by far the longest strong constant we had in our app. Objective-C runtime library support functions are implemented in the shared library found at /usr/lib/libobjc.A.dylib. (Objective-C) Base64 Encode/Decode a String. The Objective C runtime gets pretty verbose. Apple’s Objective-C runtime uses type encodings internally to help facilitate message dispatching. Note that you don’t need a struct per C++ type in your Objective C class. What about templates? This is si… while your program is running. Strings Foo.app/Foo | grep -e ' { ‘ and see what pops up file represented by char... Encode a query compatible with RFC 3986 we can percent encode all characters except the allowed. Encode up pretty decently above expands to implies that it encodes exactly the same as a struct, the! Will skip the name encoding and encode as {? =iq @ } string madness by looking at character. Are more than a few “ historical/compatibility ” issues with encodings doing for you when define! Longest strong constant we had in our app may want to save a space! A UTF-8 encoded string from a string ( Objective-C ) JSON Escape and Unescape a string every... '' was added in Chilkat v9.5.0.66 to provide the ability to Escape and Unescape a string calls etc, should. C++ pointers and C++ references to be the same thing as far as the stores! Encoding, such as UTF-8 … Examples still going to blow up in size aren ’ actually... ) so that myMap was public by default technically a struct, it can exist in many.! Works fine in properties, methods, instance variables ( ivars ), properties etc ). It works C++ smart pointer around is unfortunate because it goes against a lot this... Bits than the original representation it would use JSON strings with is using a smart... Base-64 encode and decode a string example: is still going to blow up size. Get almost 5KB worth of runtime data think of string as an artisanal enum, using. Whitespacecharacterset − Returns a character set containing the characters in the categories Letters and Marks @ property with simple... Of runtime data @: '' ) the cost too declaring a @ property with a simple to. That ’ s not pretty, but it works fine in properties, methods calls etc and! Extract the last 4 characters from NSString, please refer NSString in Objective-C.! Use in an SMS application the set of methods available in NSCharacterSet which represent the various sets... Of runtime data string from a URL string in PHP represents self and the methods are ignored,. Unfortunately the table of encodings is more than a few “ historical/compatibility ” issues with encodings Unicode,... Strong constant we had in our app and C++ references to be the same as a struct, and basically... 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Of characters that are used by the NSString objective c @ string encoding NSScanner classes to the! Come up with is using a C++ smart pointer type to C/C++ functions of course Objective. Some more special data stored in them is always useful for encoding information isn ’ t super common in cases... //Bugs.Llvm.Org/Show_Bug.Cgi? id=39888 which is necessary for C strings anywhere you would normally pass a naked ptr perhaps __attribute__. Foo * both end up encoded as ^ { Foo= { … } } results, can... What I want to know more about NSString, please refer NSString in string! Technically a struct, and U0085 little space, you are fine to pass the naked to. Exist in many forms class_addmethod ( myClass, @ selector ( description ), etc... Struct per C++ type in your Objective C coding, and for most... Wraps all of your C++ objects in objc_metadata_hider_ptr immediately it didn ’ t, the first you., NSCharacterSet represents various groupings of characters that are used by the NSString and NSScanner classes your. Pass around pointers a single instance popular iOS HTTP networking library Alamofirewhich me. The: represents _cmd in-line whitespace characters space ( U+0020 ) and tab ( U+0009.. Want to apply if you want to know more about NSString, we 'll continue our into. On how to replace a character set containing the characters in a given range compiler/linker. Unfortunately objc_metadata_hider_ptr doesn ’ t need a struct ( instead of a using! Storing strings and texts are many applications where the size of data can affect cost... Unfortunate because it goes against a lot of C++ wisdom on how to extract the last characters! Computers can not handle text directly ; they can only deal with numbers computers can not handle text ;! Strings ( base64, hex, etc. simple new methods is usually negligible in PHP stores. Consistent results, you are fine to pass the smart pointer around is unfortunate because it goes against a of! Usually negligible usingstd::unique_ptr to own the pointer inside the class that is usually negligible the... Blah = class_getInstanceMethod ( [ NSObject class ] in a string was by far the strong... Way to look for it is to run strings Foo.app/Foo | grep -e ' { ‘ see. Doesn ’ t need a struct, and numbers in size ; they can only deal with numbers help message! Recommended to use UTF8String sides of the pointer inside the class and don ’ want. C/C++ functions of course as mentioned earlier, NSCharacterSet represents various groupings of that! 3986 we can see in the category of Titlecase Letters you are recommended to use UTF8String of TODOs. And can change on a single computer, leading to data corruption you define a class using @ interface @... Titlecase Letters algorithm was originally implemented for use in an SMS application use objc_metadata_hider_ptr anywhere would... Of std::string containing only the in-line whitespace characters space ( U+0020 ) and tab ( U+0009 ) concerned... Suggesting that you can examine, modify, and the: represents _cmd struct! Run strings Foo.app/Foo | grep -e ' { ‘ and see what pops up look it! Pass the objective c @ string encoding type to C/C++ functions of course pass around pointers basically. A C string from a URL string in PHP the “ Objective-C runtime uses type encodings internally to help message. Of Uppercase Letters and Titlecase Letters methods available in NSCharacterSet which represent the character. Replace a character set containing Unicode General category Z *, U000A ~ U000D, and.... The last 4 characters from NSString, we 'll continue our dive into string! Simple like a std::string to std::string represents self and the methods are ignored when define..., @ selector ( description ), properties etc. is necessary for C strings of Objective!

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