Difference between revisions of "Hacker Guide/Variables"
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| + | {{Back to|Hacker Guide}} | ||
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== Introduction == | == Introduction == | ||
{{VLC}} has a powerful "object variable" infrastructure, that can be used to pass information between modules. | {{VLC}} has a powerful "object variable" infrastructure, that can be used to pass information between modules. | ||
| − | It can be compared to an [ | + | It can be compared to an [[wikipedia:Observer pattern|observer pattern]]. |
== Variable Functions == | == Variable Functions == | ||
| − | === var_Get === | + | === var_Get === |
| − | '''va_Get*''' functions will get the value if the variable exists (and will error otherwise). | + | '''va_Get*''' functions will get the value if the variable exists (and will error otherwise). |
var_Get ( vlc_object_t *, const char *, vlc_value_t * ); | var_Get ( vlc_object_t *, const char *, vlc_value_t * ); | ||
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var_GetAddress( p_obj, psz_name ); | var_GetAddress( p_obj, psz_name ); | ||
| − | === var_Inherit === | + | === var_Inherit === |
| − | '''var_Inherit*''' functions will get the default value (from configuration, for example) or the one set by the parent object. | + | '''var_Inherit*''' functions will get the default value (from configuration, for example) or the one set by the parent object. |
| + | |||
| + | This is the function you will want to use most of the time if you are unsure. | ||
| + | |||
| + | General prototype: | ||
| + | <type> var_Inherit<type>( vlc_object_t *obj, const char *name ); | ||
| + | |||
| + | You are responsible for freeing any strings used. | ||
| + | |||
var_Inherit | var_Inherit | ||
var_InheritBool | var_InheritBool | ||
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var_InheritURational | var_InheritURational | ||
| − | === | + | ====Example==== |
| − | + | Reading the "volume-step" configuration option: | |
| − | If the variable does exist before the call it will get the current value (and increment | + | float volumeStep = var_InheritFloat( p_this, "volume-step" ); |
| + | |||
| + | === var_CreateGet === | ||
| + | |||
| + | '''var_CreateGet*''' functions will create the variable and the get the default value if the variable wasn't already created. | ||
| + | |||
| + | If the variable does exist before the call it will get the current value (and increment its [[wikipedia:en:Refcount|refcount]]). | ||
var_Create(a,b,c) | var_Create(a,b,c) | ||
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var_CreateGetNonEmptyStringCommand(a,b) | var_CreateGetNonEmptyStringCommand(a,b) | ||
| − | A variable must be created if you want to add a callback or change the value (with var_Set) of a variable <br> | + | A variable must be created if you want to add a callback or change the value (with <code>var_Set</code>) of a variable <br> |
| + | |||
| + | {{Hacker_Guide}} | ||
Latest revision as of 08:23, 17 April 2019
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This page is under construction and may omit important points. |
Contents
Introduction
VLC media player has a powerful "object variable" infrastructure, that can be used to pass information between modules.
It can be compared to an observer pattern.
Variable Functions
var_Get
va_Get* functions will get the value if the variable exists (and will error otherwise).
var_Get ( vlc_object_t *, const char *, vlc_value_t * ); var_GetBool( p_obj, psz_name ); var_GetInteger( p_obj, psz_name ); var_GetTime( p_obj, psz_name ); var_GetFloat( p_obj, psz_name ); var_GetString( p_obj, psz_name ); var_GetNonEmptyString( p_obj, psz_name ); var_GetAddress( p_obj, psz_name );
var_Inherit
var_Inherit* functions will get the default value (from configuration, for example) or the one set by the parent object.
This is the function you will want to use most of the time if you are unsure.
General prototype:
<type> var_Inherit<type>( vlc_object_t *obj, const char *name );
You are responsible for freeing any strings used.
var_Inherit var_InheritBool var_InheritInteger var_InheritFloat var_InheritString var_InheritTime var_InheritAddress var_InheritURational
Example
Reading the "volume-step" configuration option:
float volumeStep = var_InheritFloat( p_this, "volume-step" );
var_CreateGet
var_CreateGet* functions will create the variable and the get the default value if the variable wasn't already created.
If the variable does exist before the call it will get the current value (and increment its refcount).
var_Create(a,b,c) var_CreateGetInteger(a,b) var_CreateGetBool(a,b) var_CreateGetTime(a,b) var_CreateGetFloat(a,b) var_CreateGetString(a,b) var_CreateGetNonEmptyString(a,b) var_CreateGetAddress(a,b) var_CreateGetIntegerCommand(a,b) var_CreateGetBoolCommand(a,b) var_CreateGetTimeCommand(a,b) var_CreateGetFloatCommand(a,b) var_CreateGetStringCommand(a,b) var_CreateGetNonEmptyStringCommand(a,b)
A variable must be created if you want to add a callback or change the value (with var_Set) of a variable
This page is part of official VLC media player Documentation (User Guide • Streaming HowTo • Hacker Guide • Modules)
Please read the Documentation Editing Guidelines before you edit the documentation
Please read the Documentation Editing Guidelines before you edit the documentation
Permission is granted to copy, distribute and/or modify this document under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.
