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api:non-standard-lua-libs [2016/06/20 17:27] payonel [Modules] |
api:non-standard-lua-libs [2020/05/23 17:38] (current) payonel [Operating System Facilities] |
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| if the user tries to load "foobar" | if the user tries to load "foobar" | ||
| - | `local foobar = require(*foobar")` | + | `local foobar = require("foobar")` |
| Following is the order of files `require` looks for to resolve require("foobar"). To make it interesting, we are assuming the current working directory is /tmp/ | Following is the order of files `require` looks for to resolve require("foobar"). To make it interesting, we are assuming the current working directory is /tmp/ | ||
| Line 66: | Line 66: | ||
| Contains the source of cached libraries in a table, keyed by the library name (as given to `require`), and whose value is the cached library itself. Setting a value to `nil` in this table essentially removes the library from the cache. Some libraries are assumed to remain loaded for the proper execution of the operating system. | Contains the source of cached libraries in a table, keyed by the library name (as given to `require`), and whose value is the cached library itself. Setting a value to `nil` in this table essentially removes the library from the cache. Some libraries are assumed to remain loaded for the proper execution of the operating system. | ||
| - | |||
| - | * ''delayloaded-start'', ''delayloaded-end'' | ||
| - | |||
| - | This is an advanced library loading feature built for memory optimizations in OpenOS. We don't expect users to ever need to use this feature, nor should there be a need to understand it. But it is here because it deserves some documentation. | ||
| - | |||
| - | This specially formatted comment, called a delayload annotation, guides the `package` loader to only partially store a library in memory along with sufficient metadata about which functions have not been loaded. The returned library table uses metatable redirection to lazy-load these not-yet-loaded methods, giving the user the experience that all methods are available form the start. This unusual optimization was done to reduce memory costs on boot of OpenOS. To include a method for delay loading 3 things are required: proper delayload annotation syntax, proper environment boxing, and marking `package.delayed[libname]` to true for the library before loading (i.e. before `require`). | ||
| - | |||
| - | - delayload annotation syntax | ||
| - | |||
| - | This exact text, `--[[@delayloaded-start@]]`, must come after `function` and before the function name. The method must be at least one generation below the library table, e.g. `lib.methodName` or `lib.a.b.methodName`, but not just `methodName`. | ||
| - | |||
| - | `end` must be on a new line, with no text before it, followed by this exact text `--[[@delayloaded-end@]]` followed by a newline. | ||
| - | |||
| - | - delayloaded method environments | ||
| - | |||
| - | Delay loaded methods may expect closure around local identifiers. In order to pass the local environment (and because the oc sandbox does not give sufficient debug hooks), you must return a second table from the library lua file that holds locals needed. For example, if your delay loaded method is using a local function `foobar`, you'll return a env table at the end of your library file, as a second return, of at least `{foobar=foobar}` | ||
| - | |||
| - | - ''package.delayed'' | ||
| - | |||
| - | `package.delayed` is a table whose keys are the library names and values of `true` to indicate to the package loader to attempt to delay load the methods. Note that failed delay load parsing falls back to a normal load of the library. | ||
| - | |||
| - | ```lua | ||
| - | function --[[@delayloaded-start@]] lib.name(...) | ||
| - | body(1,2,3) | ||
| - | end --[[@delayloaded-end@]] | ||
| - | |||
| - | return lib, {body=body} | ||
| - | ``` | ||
| - | |||
| - | ```lua | ||
| - | package.delayed["foobar"] = true | ||
| - | local foobar = require("foobar") | ||
| - | ``` | ||
| - | |||
| String Manipulation | String Manipulation | ||
| Line 135: | Line 101: | ||
| - **binary mode** | - **binary mode** | ||
| - | Streams given by `io.open(path, "rb")` or `filesystem.open(path)` are in binary mode. `filesystem.open(path, "rb")` also works, but streams returned by `filesystem.open` are **always** in binary mode. `stream:read(1)` in binary mode reads a single byte. Reading a numerical value via `buffered_stream:read("*n")` considers the `string.char()` of each byte (buffered streams are returned from `io.open`, and support interpreting numerical values from a stream) | + | Streams given by `io.open(path, "rb")` or `filesystem.open(path)` are in binary mode. `filesystem.open(path, "rb")` also works, but streams returned by `filesystem.open` are **always** in binary mode. `stream:read(1)` in binary mode reads a single byte. Reading a numerical value via `buffered_stream:read("*n")` reads the data as single-byte characters. (buffered streams are returned from `io.open`, and support interpreting numerical values from a stream) |
| - **text mode** | - **text mode** | ||
| - | Only streams given by `io.open` that specifically do not use "b" in the mode are in text mode. Examples are `io.open(path)` and `io.open(path, "r")`. No type of handle given by `filesystem.open` is a stream in text mode. `stream:read(1)` in text mode reads a single unicode-aware char. This could be a single byte, or even 3 bytes - depending on the text. Reading a numerical value via `buffered_stream:read("*n")` considers the `unicode.char()` of the series of bytes (buffered streams are returned from `io.open`, and support interpreting numerical values from a stream) | + | Only streams given by `io.open` that specifically do not use "b" in the mode are in text mode. Examples are `io.open(path)` and `io.open(path, "r")`. No type of handle given by `filesystem.open` is a stream in text mode. `stream:read(1)` in text mode reads a single unicode-aware char. This could be a single byte, or even 3 bytes - depending on the text. Reading a numerical value via `buffered_stream:read("*n")` reads the data as unicode chars. (buffered streams are returned from `io.open`, and support interpreting numerical values from a stream) |
| * `io.open(path, "r")` is equivalent to `io.open(path)`, which opens a file in text read-only mode. | * `io.open(path, "r")` is equivalent to `io.open(path)`, which opens a file in text read-only mode. | ||
| Line 184: | Line 150: | ||
| One additional function has been added: | One additional function has been added: | ||
| - | - `os.sleep(seconds: number)` which allows pausing a script for the specified amount of time. Note that signals will still be processed by event handlers while the sleep is active, i.e. you cannot pull signals that were accumulated during the sleep after it ended, since no signals will remain in the queue (or at least not all of them). | + | - `os.sleep(seconds: number)` which allows pausing a script for the specified amount of time. `os.sleep` consumes events but registered event handlers and threads are still receiving events during the sleep. Rephrased, signals will still be processed by event handlers while the sleep is active, i.e. you cannot pull signals that were accumulated during the sleep after it ended, since no signals will remain in the queue (or at least not all of them). |
| Some new functions that kind of fall into this category are available in [[api:computer|the computer API]]. | Some new functions that kind of fall into this category are available in [[api:computer|the computer API]]. | ||