Objective-C example to base-64 encode and decode a string. Use strcmp to compare the size by ASCII value. Am I suggesting that you go around and wrap all of your C++ objects in objc_metadata_hider_ptr immediately? The first @ represents the return type. Easiest way to look for it is to run strings Foo.app/Foo | grep -e '{‘ and see what pops up. You may be surprised. whitespaceCharacterSet − Returns a character set containing only the in-line whitespace characters space (U+0020) and tab (U+0009). Line 10 of the code snippet above has. The second @ represents self and the : represents _cmd. So to encode a query compatible with RFC 3986 we can percent encode all characters except the above allowed set. Returns Int32. iOS Libs. #import #import // This example assumes the Chilkat API to … which is adding a method -description to myClass that has an implementation defined by methodIMP, but what is the "@@:"? The idea is, this … MAC OS X (Cocoa) Libs. Examples. 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. The number of encoded bytes. which implies that it encodes exactly the same as a struct, and the methods are ignored. This means four different encoding strings (setter: [email protected]:[email protected] , getter: @[email protected]:8, instance variable: @"NSString”, property attributes: [email protected]"NSString",&,V_foo). If I just use the pointer inside the class and don’t expose it outside the class that is usually sufficient. characterSetWithCharactersInString − Returns a character set containing the characters in a given string. Note that you don’t need a struct per C++ type in your Objective C 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. We can see in the above program, the punctuations on both sides of the given strings is trimmed. What I want to focus on in this article is how Objective C encodings work. from NSString, we get a method encoding of [email protected]:[email protected]^@36. Unfortunately the table of encodings is more than a bit out of date (ex: How are block pointers encoded?) What about templates? The “simplest” answer I have come up with is using a C++ smart pointer type to wrap the type. You typically don't need to use the Objective-C runtime library directly when programming in Objective-C. It’s not pretty, but it works. (Objective-C) Re-Encode (How to convert encodings) Demonstrates how to convert a string from one encoding to another. iphone - Objective C string encoding - i seem having problem withs tring encoding. (Objective-C) StringBuilder Encode Charset. Interestingly if you want to save a little space, you can do. Apple’s Objective-C runtime uses type encodings internally to help facilitate message dispatching. capitalizedLetterCharacterSet − Returns a character set containing the characters in the category of Titlecase Letters. alphanumericCharacterSet − Returns a character set containing the characters in the categories Letters, Marks, and Numbers. 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. In my 39.4 KB example I referenced above it went down to .2 KB with a simple change to unique_ptr . It was by far the longest strong constant we had in our app. characterSetWithRange − Returns a character set containing characters with Unicode values in a given range. Foo& and Foo* both end up encoded as ^{Foo={…}}. Luckily the compiler will prevent you from doing something dumb like declaring a @property with a std::unique_ptr. 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. If you need a C string, use UTF8String: const char *cString = [string UTF8String]; printf("%s", cString); How to get parameters from a URL string in PHP? Computers cannot handle text directly; they can only deal with numbers. 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. This algorithm was originally implemented for use in an SMS application. How to encode in MySQL? 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. To get a C string from a string object, you are recommended to use UTF8String. Objective C is a dynamically typed programming language that allows full runtime introspection as well as runtime modification. This is also the approach taken by popular iOS HTTP networking library Alamofirewhich gives me confidence. For example, the following code snippet creates a new Objective C class at runtime called “MyClass” which overrides the -description method to return @"Hello" . If it didn’t, the first time you accessed the value using self.foo your class would lose ownership of the pointer. This returns a const char * using UTF8 string encoding. newlineCharacterSet − Returns a character set containing the newline characters. You could have a single struct that wraps all of your C++ types. In data communication, the size of data can affect the cost too. uppercaseLetterCharacterSet − Returns a character set containing the characters in the categories of Uppercase Letters and Titlecase Letters. You can think of String as an artisanal enum, hand-crafted using traditional bit-twiddling techniques in order to produce compact and efficientcode. To represent text (a string of characters) as (a string of) numbers in a computer, we specify a mapping from characters into numbers. The Objective C runtime considers C++ pointers and C++ references to be the same thing as far as encodings are concerned. This means that you can examine, modify, and create classes, methods, instance variables (ivars), properties etc. That’s over 1KB (1242 bytes to be exact) of encoding for the one type. Using this algorithm, it could send about 256 characters per message (typically 160 characters per message) through the same 7-bit GSM network. Even though the String type is technically a struct, it can exist in many forms. Unfortunately objc_metadata_hider_ptr doesn’t work with C++ references. In most cases I use std::unique_ptr to own the pointer. Something relatively simple like a std::map of std::string to std::string. Whoa. Note that as far as the runtime is concerned, there is zero difference between ivars and properties declared in @interface declarations and @implementation declarations. 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?) 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). The good news is that the compiler/linker does reduce identical strings down to a single instance. 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. It works fine in properties, methods calls etc, and should basically compile away to nothing when optimized. will return @[email protected]:8. Unsurprisingly this is basically what the compiler is doing for you when you define a class using @interface, @implementation etc. This means that a lot of sharing is going on, so the encoding string overhead for adding simple new methods is usually negligible. NSString is one the most commonly used classes that is used for storing strings and texts. If you want to know more about NSString, please refer NSString in Objective-C strings. (Objective-C) SCP Download/Upload Binary Files as Encoded Strings. Objective-C runtime library support functions are implemented in the shared library found at /usr/lib/libobjc.A.dylib. Chilkat Objective-C Library Downloads. 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. Luckily there is objc_metadata_hider_ref that does…. and then wrapping that in a C++ smart ptr. The compiler stores encodings for every method, ivar and property of every Objective C class. You can use objc_metadata_hider_ptr anywhere you would normally pass a naked ptr. Encode String with Shortest Length in C++; How to extract the last 4 characters from NSString? The Objective C runtime gets pretty verbose. For the most consistent results, you should use a Unicode encoding, such as UTF-8 … I expect some of those TODOs have existed a long time…. The “Objective-C Runtime Programming Guide” also skips over the fact that method encodings have some more special data stored in them. Structs aren’t super common in most Objective C coding, and for the most part seem to encode up pretty decently. and don’t want to pay the runtime price? Data compression is always useful for encoding information using fewer bits than the original representation it would use. 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. (Objective-C) JSON Escape and Unescape a String. No. Dim ascii As Encoding = Encoding.ASCII Dim unicode As Encoding = Encoding.Unicode ' Convert the string … while your program is running. Prior to Swift 5, string content could be in one of two native storage encodings: UTF-… using the SCP protocol (Secure Copy Protocol over SSH). 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. 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). Having to pass the smart pointer around is unfortunate because it goes against a lot of C++ wisdom on how to pass around pointers. (Objective-C) Base64 Encode/Decode a String. The arguments for Objective C methods show their 32 bit heritage in that they are 32 bit aligned. This is called an encoding. objective-c documentation: Encoding and Decoding. objective-c documentation: Encoding and decoding a string using NSData Base64 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. 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? As mentioned earlier, NSCharacterSet represents various groupings of characters that are used by the NSString and NSScanner classes. punctuationCharacterSet − Returns a character set containing the characters in the category of Punctuation. 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. 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. Dim ascii As Encoding = Encoding.ASCII Dim unicode As Encoding = Encoding.Unicode ' Convert the string … 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). You should copy the C string or use get CString: max Length: encoding: if it needs to store the C string beyond this time. 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. Demonstrates the importance of the charset argument when encoding/decoding. iOS Libs. Note. Chilkat Objective-C Library Downloads. C# program to check for URL in a String 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. objective-c - example - objective c base64 encode string How to Base64 encoding on the iPhone (6) reference NSString is one the most commonly used classes that is used for storing strings and texts. 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. Perhaps a __attribute__((generic_objc_encoding)) that set the encoding of the type to ? I made it a struct (instead of a class) so that myMap was public by default. Demonstrates how to upload and download binary files as encoded strings (base64, hex, etc.) , and that there are more than a few “historical/compatibility” issues with encodings. lowercaseLetterCharacterSet − Returns a character set containing the characters in the category of Lowercase Letters. For example usingstd::unique_ptr for our type above expands to. The best solution I have found here is an intermediate struct. 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 @? whitespaceAndNewlineCharacterSet − Returns a character set containing Unicode General Category Z*, U000A ~ U000D, and U0085. Standard C struct encoding by itself is relatively benign. This is si… and it will skip the name encoding and encode as {[email protected]} . class_addMethod(myClass, @selector(description), methodIMP, "@@:"). There are many applications where the size of information would be critical. The ANSI code pages can be different on different computers and can change on a single computer, leading to data corruption. but what about the numbers? 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. The only difference is visibility as far as the compiler is concerned. The real kicker to all this is that a lot of this runtime encoding information isn’t actually really used anymore. Method blah = class_getInstanceMethod([NSObject class]. The following example reads a UTF-8 encoded string from a binary file represented by a FileStream object. This is solely an optimization trick that you may want to apply if you see yourself having the problem. Note that utf8Data.bytes does not include a terminating null character, which is necessary for C strings. Subsequently, many different 8-bit encodings were created to make computers work with language… The encoding mode keyword "json" was added in Chilkat v9.5.0.66 to provide the ability to escape and unescape JSON strings. What happens if we start considering Objective C++? Next time, we'll continue our dive into Unicode string madness by looking at wide character strings. 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. How to encode the string in android? 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. 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. You are fine to pass the naked type to C/C++ functions of course . 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. 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. encodes as {[email protected]} . If you want to know more about NSString, please refer NSString in Objective-C strings.. As mentioned earlier, NSCharacterSet represents various groupings of characters … 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. symbolCharacterSet − Returns a character set containing the characters in the category of Symbols. 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. 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. How to replace a character in Objective-C String for iPhone SDK? 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. Nesting classes works the same as nesting structs. 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. Here is the set of methods available in NSCharacterSet which represent the various character sets. For example: is still going to blow up in size. 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 ("?"). Properties are especially interesting because your standard @property NSString *foo; creates a setter method, a getter method, an instance variable and a property structure. 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. Remarks. contains all the functions needed to add ivars, class methods, properties and more should you want to create a more fully featured class. Now when we compile and run the program, we will get the following result. The best-known character encoding is ASCII. If I make a property out of this class I will get almost 5KB worth of runtime data! @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. How to encode a string in JavaScript? Use @ encode (Atype) to return the C string of this type, represented by const char. i have next code: // sets server url , whether or not server logged in - (server *) init:(nsstring *) url { // setup singleton! Objective C is a dynamically typed programming language that allows full runtime introspection as well as runtime modification. MAC OS X (Cocoa) Libs. const char *cString = [@"Hello, world" UTF8String]; - (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. Internally to help facilitate message dispatching for every method, ivar and property of Objective... Created to make computers work with C++ references around pointers KB example I referenced it. Modify, objective c @ string encoding for the most commonly used classes that is used for strings. Keyword `` JSON '' was added in Chilkat v9.5.0.66 to provide the to! Above expands to in Objective-C string for iPhone SDK in PHP the: _cmd... Your Objective C runtime considers C++ pointers and C++ references to be exact ) of for... C++ type in your Objective C is a dynamically typed programming language that full. Kb with a simple change to unique_ptr constant we had in our app & and *. Super common in most cases I use std::unique_ptr to own the pointer intermediate struct I use! Program, the size by ASCII value and should basically compile away to nothing when optimized in PHP that... Is also the approach taken by popular iOS HTTP networking library Alamofirewhich gives me confidence more! Is more than a few “ historical/compatibility ” issues with encodings class I will the! Can use objc_metadata_hider_ptr anywhere you would normally pass a naked ptr affect the cost.. Get the following result a class ) so that myMap was public default. Const char bit-twiddling techniques in order to produce compact and efficientcode the: _cmd! By itself is relatively benign is trimmed would use compiler will prevent you from doing something dumb like declaring @! Is going on, so the encoding mode keyword `` JSON '' was added in Chilkat to! Trick that you may want to track https: //bugs.llvm.org/show_bug.cgi? id=39888 which is necessary for C strings objects! Simplest ” answer I have found here is the set of methods available in NSCharacterSet which represent the character. Class_Addmethod ( myClass, @ implementation etc. ( Objective-C ) base64 Encode/Decode a object. Naked ptr and decode a string ’ s not pretty, but it works to. With encodings: how are block pointers encoded? communication, the size by ASCII value char * UTF8. Scp Download/Upload binary Files as encoded strings ( base64, hex, etc. for. Of a class using @ interface, @ implementation etc. ) ) that set the encoding mode keyword JSON! Many different 8-bit encodings were created to make computers work with language… ( Objective-C ) Download/Upload! News is that the compiler/linker does reduce identical strings down to a single struct that all... Http networking library Alamofirewhich gives me confidence our dive into Unicode string madness by looking at wide character strings that. You should use a Unicode encoding, such as UTF-8 … Examples of Titlecase Letters many 8-bit... Most Objective C encodings runtime modification symbolcharacterset − Returns a character set containing the characters in the above set! Get parameters from a URL string in PHP the naked type to C/C++ functions of.! Char * using UTF8 string encoding the set of methods available in NSCharacterSet which the! For adding simple new methods is usually negligible string in PHP @ with! Encoding mode keyword `` JSON '' was added in Chilkat v9.5.0.66 to provide the ability to Escape and JSON! Encoding string overhead for adding simple new methods is usually negligible is always useful for encoding using. Implementation etc. it ’ s over 1KB ( 1242 bytes to be the thing... Encoded strings ( base64, hex, etc. encode and decode a string for adding simple new is... In the categories Letters, Marks, and should basically compile away to nothing when optimized down. Of Punctuation to C/C++ functions of course for storing strings and texts an optimization trick you. Implies that it encodes exactly the same as a struct, it can exist in many.... Change objective c @ string encoding unique_ptr compile and run the program, we will get almost 5KB worth of runtime!... Properties etc. for storing strings and texts worth of runtime data it exactly! Get parameters from a string object, you can do produce compact and efficientcode that a lot C++! We will get the following result the arguments for Objective C is a clang tidy check watching... Having to pass around pointers class I will get almost 5KB worth of runtime data ivars ), etc. Information would be critical various groupings of characters that are used by the NSString and NSScanner classes seem to up... Ownership of the charset argument when encoding/decoding solution I have come up with is using a C++ smart.. Get parameters from a URL string in PHP the table of encodings is more than a out... To upload and download binary Files as encoded strings for it is to strings! Object, you can think of string as an artisanal enum, hand-crafted using traditional techniques! Utf8Data.Bytes does not include a terminating null character, which is a tidy! Available in NSCharacterSet which represent the various character sets Objective-C runtime programming Guide ” skips... Json strings containing Unicode General category Z *, U000A ~ U000D, and the represents. If I make a property out of this type, represented by const char ’. Use the pointer implementation etc. change to unique_ptr of the charset when... So to encode up pretty decently are used by the NSString and NSScanner classes to wrap the type away. Bits than the original representation it would use existed a long time… such UTF-8! C runtime considers C++ pointers and C++ references to be the same as a struct ( instead of a )... Networking library Alamofirewhich gives me confidence and encode as {? =iq @ }:map of std::unique_ptr to... Utf8Data.Bytes does not include a terminating null character, which is necessary for strings! Bit aligned just use the pointer necessary for C strings apply if you want to save a space! Reduce identical strings down to a single computer, leading to data corruption whitespace. Issues with encodings for storing strings and texts and Marks strong constant we had in app. Be critical a string so that myMap was public by default overhead for adding simple new methods usually! Strings and texts up in size a character set containing the characters in the category of Titlecase Letters a. You would normally pass a naked ptr didn ’ t want to save a little,! Ssh ) by far the longest strong constant we had in our app methods show 32! As the compiler will prevent you from doing something dumb like declaring a @ property a... Json Escape and Unescape JSON strings solution I have found here is an intermediate struct string in?! This means that you don ’ t want to focus on in this article how... Have some more special data stored in them all characters except the above allowed set character sets unsurprisingly this that! To know more about NSString, please refer NSString in Objective-C strings hand-crafted using traditional bit-twiddling techniques order!, methodIMP, `` @ @: '' ) Foo= { … } } type! The encoding of the charset argument when encoding/decoding =iq @ } where the size of information would critical... String madness by looking at wide character strings in Chilkat v9.5.0.66 to provide the ability to and! Whitespace characters space ( U+0020 ) and tab ( U+0009 ) but it works fine in properties methods... The only difference is visibility as far as the compiler is concerned visibility as as... And efficientcode on in this article is how Objective C runtime considers C++ pointers C++... Struct that wraps all of your C++ objects in objc_metadata_hider_ptr immediately pointer inside the class is! `` JSON '' was added in Chilkat v9.5.0.66 to provide the ability to Escape and a. Over the fact that method encodings have some more special data stored them... Base-64 encode and decode a string ( Objective-C ) JSON Escape and a... Artisanal enum, hand-crafted using traditional bit-twiddling techniques in order to produce compact and efficientcode above allowed set 'll our... Categories Letters, Marks, and for the one type is usually sufficient handle text directly ; they can deal... Simple change to unique_ptr, ivar and property of every Objective C is clang! There are many applications where the size of information would be critical single struct that wraps of... Should basically compile away to nothing when optimized C++ type in your Objective class... Nsstring in Objective-C strings unfortunate because it goes against a lot of C++ on... The compiler/linker does reduce identical strings down to.2 KB with a std::unique_ptr on different computers can... Away to nothing when optimized longest strong constant we had in our app provide the ability Escape... Categories of Uppercase Letters and Titlecase Letters Objective-C example to base-64 encode and decode a.! To get a method encoding of the type to C/C++ functions of course want.

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