{"id":501,"date":"2005-12-14T09:36:23","date_gmt":"2005-12-14T09:36:23","guid":{"rendered":"http:\/\/beta.robertprice.co.uk\/robblog\/2005\/12\/adding_class_variables_to_object_orientated_inline_c-shtml\/"},"modified":"2005-12-14T09:36:23","modified_gmt":"2005-12-14T09:36:23","slug":"adding_class_variables_to_object_orientated_inline_c-shtml","status":"publish","type":"post","link":"https:\/\/www.robertprice.co.uk\/robblog\/adding_class_variables_to_object_orientated_inline_c-shtml\/","title":{"rendered":"Adding Class Variables To Object Orientated Inline::C"},"content":{"rendered":"

\nI’ve been working using the Perl<\/a> module Inline::C<\/a> lately.\n<\/p>\n

\nI’ve been using it for some Object Orientated code, and I’ve had the need to have a shared class variable between various C classes. I thought I’d share how I’d accomplished this.\n<\/p>\n

\nThe code I’m using here is based on the object example in Inline::C-Cookbook<\/a>.\n<\/p>\n

\nI’m going to add a class variable called count<\/var> to the example Soldier<\/var> class.\n<\/p>\n

\nFirstly we need to add a new line of code to declare this variable\n<\/p>\n

## class variable
\nstatic int counter = 0;
\n<\/code><\/div>\n

\nNoticed I’ve made the variable static<\/code> to ensure only one copy of it exists. I’ve also initialised it to 0.\n<\/p>\n

\nOne thing I’ve done, that isn’t really necessary is to add it to the Soldier object. The new Soldier object looks like this…\n<\/p>\n

typedef struct {
\nchar* name;
\nchar* rank;
\nlong serial;
\nint* count;
\n} Soldier;
\n<\/code><\/div>\n

\nThe new line here is int* count<\/code>, a pointer to an integer called count. We’ll point this at our static counter variable.\n<\/p>\n

\nTo point count<\/var> to counter<\/var> we modify the new<\/code> function to add the following…\n<\/p>\n

solder->serial = serial; ## existing code
\nsoldier->count = &counter;
\n<\/code><\/div>\n

\nHere we’re specifically saying that our pointer count should point to the address of counter<\/var>.\n<\/p>\n

\nGreat, but we need a way of accessing this data. We’ll create a new method called get_count<\/code> to return the current value of count.\n<\/p>\n

int get_count(SV* obj) {
\nreturn *((Soldier*)SvIV(SvRV(obj)))->count;
\n}
\n<\/code><\/div>\n

\nGreat, now we can just call get_count<\/code> from our Soldier object.\n<\/p>\n

\nBy itself this isn’t really much use as we never manipulate the value of counter<\/var>. To prove this works, just modify the new<\/code> method to add a line that increments counter<\/var>. For example,\n<\/p>\n

## increment counter
\ncounter++;
\n<\/code><\/div>\n

\nVoila! We we have a static class variable that can now be used with Inline::C objects!<\/p>\n","protected":false},"excerpt":{"rendered":"

I’ve been working using the Perl module Inline::C lately. I’ve been using it for some Object Orientated code, and I’ve had the need to have a shared class variable between various C classes. I thought I’d share how I’d accomplished this. The code I’m using here is based on the object example in Inline::C-Cookbook. I’m … Continue reading “Adding Class Variables To Object Orientated Inline::C”<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"inline_featured_image":false,"footnotes":""},"categories":[2],"tags":[17,47],"class_list":["post-501","post","type-post","status-publish","format-standard","hentry","category-dev","tag-dev","tag-perl"],"yoast_head":"\nAdding Class Variables To Object Orientated Inline::C - Robert Price<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.robertprice.co.uk\/robblog\/adding_class_variables_to_object_orientated_inline_c-shtml\/\" \/>\n<meta property=\"og:locale\" content=\"en_GB\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Adding Class Variables To Object Orientated Inline::C - Robert Price\" \/>\n<meta property=\"og:description\" content=\"I’ve been working using the Perl module Inline::C lately. I’ve been using it for some Object Orientated code, and I’ve had the need to have a shared class variable between various C classes. I thought I’d share how I’d accomplished this. The code I’m using here is based on the object example in Inline::C-Cookbook. I’m … Continue reading "Adding Class Variables To Object Orientated Inline::C"\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.robertprice.co.uk\/robblog\/adding_class_variables_to_object_orientated_inline_c-shtml\/\" \/>\n<meta property=\"og:site_name\" content=\"Robert Price\" \/>\n<meta property=\"article:published_time\" content=\"2005-12-14T09:36:23+00:00\" \/>\n<meta name=\"author\" content=\"rob\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:label1\" content=\"Written by\" \/>\n\t<meta name=\"twitter:data1\" content=\"rob\" \/>\n\t<meta name=\"twitter:label2\" content=\"Estimated reading time\" \/>\n\t<meta name=\"twitter:data2\" content=\"2 minutes\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\\\/\\\/schema.org\",\"@graph\":[{\"@type\":\"Article\",\"@id\":\"https:\\\/\\\/www.robertprice.co.uk\\\/robblog\\\/adding_class_variables_to_object_orientated_inline_c-shtml\\\/#article\",\"isPartOf\":{\"@id\":\"https:\\\/\\\/www.robertprice.co.uk\\\/robblog\\\/adding_class_variables_to_object_orientated_inline_c-shtml\\\/\"},\"author\":{\"name\":\"rob\",\"@id\":\"https:\\\/\\\/www.robertprice.co.uk\\\/robblog\\\/#\\\/schema\\\/person\\\/fac6d5b076e0e14e1fb13e15b542a6c5\"},\"headline\":\"Adding Class Variables To Object Orientated Inline::C\",\"datePublished\":\"2005-12-14T09:36:23+00:00\",\"mainEntityOfPage\":{\"@id\":\"https:\\\/\\\/www.robertprice.co.uk\\\/robblog\\\/adding_class_variables_to_object_orientated_inline_c-shtml\\\/\"},\"wordCount\":278,\"keywords\":[\"Dev\",\"Perl\"],\"articleSection\":[\"Dev\"],\"inLanguage\":\"en-GB\"},{\"@type\":\"WebPage\",\"@id\":\"https:\\\/\\\/www.robertprice.co.uk\\\/robblog\\\/adding_class_variables_to_object_orientated_inline_c-shtml\\\/\",\"url\":\"https:\\\/\\\/www.robertprice.co.uk\\\/robblog\\\/adding_class_variables_to_object_orientated_inline_c-shtml\\\/\",\"name\":\"Adding Class Variables To Object Orientated Inline::C - Robert Price\",\"isPartOf\":{\"@id\":\"https:\\\/\\\/www.robertprice.co.uk\\\/robblog\\\/#website\"},\"datePublished\":\"2005-12-14T09:36:23+00:00\",\"author\":{\"@id\":\"https:\\\/\\\/www.robertprice.co.uk\\\/robblog\\\/#\\\/schema\\\/person\\\/fac6d5b076e0e14e1fb13e15b542a6c5\"},\"breadcrumb\":{\"@id\":\"https:\\\/\\\/www.robertprice.co.uk\\\/robblog\\\/adding_class_variables_to_object_orientated_inline_c-shtml\\\/#breadcrumb\"},\"inLanguage\":\"en-GB\",\"potentialAction\":[{\"@type\":\"ReadAction\",\"target\":[\"https:\\\/\\\/www.robertprice.co.uk\\\/robblog\\\/adding_class_variables_to_object_orientated_inline_c-shtml\\\/\"]}]},{\"@type\":\"BreadcrumbList\",\"@id\":\"https:\\\/\\\/www.robertprice.co.uk\\\/robblog\\\/adding_class_variables_to_object_orientated_inline_c-shtml\\\/#breadcrumb\",\"itemListElement\":[{\"@type\":\"ListItem\",\"position\":1,\"name\":\"Home\",\"item\":\"https:\\\/\\\/www.robertprice.co.uk\\\/robblog\\\/\"},{\"@type\":\"ListItem\",\"position\":2,\"name\":\"Adding Class Variables To Object Orientated Inline::C\"}]},{\"@type\":\"WebSite\",\"@id\":\"https:\\\/\\\/www.robertprice.co.uk\\\/robblog\\\/#website\",\"url\":\"https:\\\/\\\/www.robertprice.co.uk\\\/robblog\\\/\",\"name\":\"Robert Price\",\"description\":\"\",\"potentialAction\":[{\"@type\":\"SearchAction\",\"target\":{\"@type\":\"EntryPoint\",\"urlTemplate\":\"https:\\\/\\\/www.robertprice.co.uk\\\/robblog\\\/?s={search_term_string}\"},\"query-input\":{\"@type\":\"PropertyValueSpecification\",\"valueRequired\":true,\"valueName\":\"search_term_string\"}}],\"inLanguage\":\"en-GB\"},{\"@type\":\"Person\",\"@id\":\"https:\\\/\\\/www.robertprice.co.uk\\\/robblog\\\/#\\\/schema\\\/person\\\/fac6d5b076e0e14e1fb13e15b542a6c5\",\"name\":\"rob\",\"image\":{\"@type\":\"ImageObject\",\"inLanguage\":\"en-GB\",\"@id\":\"https:\\\/\\\/secure.gravatar.com\\\/avatar\\\/6f0eb511179100a4e968abc70403e33686e6ab3e992e392bedd2ccac01da666c?s=96&d=mm&r=g\",\"url\":\"https:\\\/\\\/secure.gravatar.com\\\/avatar\\\/6f0eb511179100a4e968abc70403e33686e6ab3e992e392bedd2ccac01da666c?s=96&d=mm&r=g\",\"contentUrl\":\"https:\\\/\\\/secure.gravatar.com\\\/avatar\\\/6f0eb511179100a4e968abc70403e33686e6ab3e992e392bedd2ccac01da666c?s=96&d=mm&r=g\",\"caption\":\"rob\"}}]}<\/script>\n<!-- \/ Yoast SEO plugin. -->","yoast_head_json":{"title":"Adding Class Variables To Object Orientated Inline::C - Robert Price","robots":{"index":"index","follow":"follow","max-snippet":"max-snippet:-1","max-image-preview":"max-image-preview:large","max-video-preview":"max-video-preview:-1"},"canonical":"https:\/\/www.robertprice.co.uk\/robblog\/adding_class_variables_to_object_orientated_inline_c-shtml\/","og_locale":"en_GB","og_type":"article","og_title":"Adding Class Variables To Object Orientated Inline::C - Robert Price","og_description":"I’ve been working using the Perl module Inline::C lately. 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