3. MCP Server Reference › 3.3 Engine › Element files

The engine_files_* section works with the files attached to the store’s rows: a product photo, a certificate, a supplier’s price list. The template styling files — images, fonts, icons — are the “Images” section.

Where the File Lies

An element file is a row of the files_<entity> table and the file itself on the server’s disk:

files/<year>/<month_day>/<hour_minute>/<table>_<user>_<id>.<extension>

The engine builds the folder out of the upload time down to the minute, and makes up the name itself. The name people see the file under is kept in real_name.

The extension stays in the name only if it is one of the safe ones: images, documents, archives, sound and video, fonts, design files. A file of another type — php, html or svg, for example — goes onto the disk without an extension: that way the web server will not execute it and will not show it as a page. The former name is kept in real_name.

The Entity

entity is the name of the owner table, and everything else follows from it:

From `entity`	What comes out	Example for `store`
the owner table	`<entity>`	`store`
the files table	`files_<entity>`	`files_store`
the registry of kinds	`key_value` rows with `key_code = 'FILES_<ENTITY>'`	`FILES_STORE`

An entity will do if the store has a files_<entity> table with a generator. In this version there are thirteen of them: store, info, info_value, brand, topic, key_value, lang, field, advert_text, order_option, order_option_value, web_key, web_key_value. A product photo is store.

Kind and Order

kind_key divides an element’s files into groups, kBase by default. If the table’s registry of kinds has rows, another kind is refused with a list of the allowed ones; if the registry is empty, any one will do. The order pos is counted inside the group: a new file goes to its end.

What Is Not There

Editing a file. A replacement is a new file and the removed row of the old one: the names are unique, nothing is written over.
Deleting from the disk. Deletion removes the row, and the file stays on the server’s disk. The space is freed by the audit module for unused files, which the owner runs. The only exception is the attachments of tool_run: the files a command has not named as its own the store wipes from the disk itself, right after the call.
Reduced copies. They are made by the program’s image processing; the tool puts only the source file.

The Table in Work

Adding and removing take files_<entity> into work for the duration of the call and mark it for the storefront’s cache. If somebody else is holding the table — most often an open window of the program — both refuse, having written nothing. Loading only reads, and a busy table does not get in its way.

In the Markup

The path to a file is assembled out of the row’s fields, not out of a ready-made folder:

<img src="{IMG:UPLOAD_TIME|path}{IMG:FILE_NAME}">

The path modifier is described in “Modifiers”.