Lua-System

• Index

Contents

• Bit flags

Classes

• bitflags

Modules

• system

Topics

• 1. Introduction
• 2. Development
• 3. Terminal functionality
• CHANGELOG
• MIT License

Examples

• compat.lua
• flag_debugging.lua
• password_input.lua
• read.lua
• readline.lua
• spinner.lua
• spiral_snake.lua
• terminalsize.lua

Class bitflags

Bitflags module.

The bitflag object makes it easy to manipulate flags in a bitmask.

It has metamethods that do the hard work, adding flags sets them, substracting unsets them. Comparing flags checks if all flags in the second set are also set in the first set. The has method checks if all flags in the second set are also set in the first set, but behaves slightly different.

Indexing allows checking values or setting them by bit index (eg. 0-7 for flags in the first byte).

NOTE: unavailable flags (eg. Windows flags on a Posix system) should not be omitted, but be assigned a value of 0. This is because the has method will return false if the flags are checked and the value is 0.

See system.bitflag (the constructor) for extensive examples on usage.

Bit flags

Bit flags

bitflag:has_all_of (subset)

Checks if all the flags in the given subset are set. If the flags to check has a value 0, it will always return false. So if there are flags that are unsupported on a platform, they can be set to 0 and the has_all_of function will return false if the flags are checked.

Parameters:

• subset bitflag the flags to check for.

Returns:

boolean true if all the flags are set, false otherwise.

Usage:

local sys = require 'system'
local flags = sys.bitflag(12)     -- b1100
local myflags = sys.bitflag(15)   -- b1111
print(flags:has_all_of(myflags))  -- false, not all bits in myflags are set in flags
print(myflags:has_all_of(flags))  -- true, all bits in flags are set in myflags

bitflag:has_any_of (subset)

Checks if any of the flags in the given subset are set. If the flags to check has a value 0, it will always return false. So if there are flags that are unsupported on a platform, they can be set to 0 and the has_any_of function will return false if the flags are checked.

Parameters:

• subset bitflag the flags to check for.

Returns:

boolean true if any of the flags are set, false otherwise.

Usage:

local sys = require 'system'
local flags = sys.bitflag(12)     -- b1100
local myflags = sys.bitflag(7)    -- b0111
print(flags:has_any_of(myflags))  -- true, some bits in myflags are set in flags
print(myflags:has_any_of(flags))  -- true, some bits in flags are set in myflags

bitflag:value ()

Retrieves the numeric value of the bitflag object.

Returns:

number the numeric value of the bitflags.

Usage:

local sys = require 'system'
local flags = sys.bitflag()     -- b0000
flags[0] = true                 -- b0001
flags[2] = true                 -- b0101
print(flags:value())            -- 5

system.bitflag ([value=0])

Creates a new bitflag object from the given value.

Parameters:

• value number the value to create the bitflag object from. (default 0)

Returns:

bitflag bitflag object with the given values set.

Usage:

local sys = require 'system'
local flags = sys.bitflag(2)    -- b0010

-- get state of individual bits
print(flags[0])                 -- false
print(flags[1])                 -- true

-- set individual bits
flags[0] = true                 -- b0011
print(flags:value())            -- 3
print(flags)                    -- "bitflags: 3"

-- adding flags (bitwise OR)
local flags1 = sys.bitflag(1)   -- b0001
local flags2 = sys.bitflag(2)   -- b0010
local flags3 = flags1 + flags2  -- b0011

-- substracting flags (bitwise AND NOT)
print(flags3:value())           -- 3
flag3 = flag3 - flag3           -- b0000
print(flags3:value())           -- 0

-- comparing flags
local flags4 = sys.bitflag(7)   -- b0111
local flags5 = sys.bitflag(255) -- b11111111
print(flags5 ~= flags4)         -- true, not the same flags
local flags6 = sys.bitflag(7)   -- b0111
print(flags6 == flags4)         -- true, same flags

-- comparison of subsets
local flags7 = sys.bitflag(0)    -- b0000
local flags8 = sys.bitflag(3)    -- b0011
local flags9 = sys.bitflag(7)    -- b0111
print(flags9:has_all_of(flags8)) -- true, flags8 bits are all set in flags9
print(flags8:has_any_of(flags9)) -- true, some of flags9 bits are set in flags8
print(flags8:has_all_of(flags7)) -- false, flags7 (== 0) is not set in flags8