vmode: Virtual storage mode

In ff: Memory-Efficient Storage of Large Data on Disk and Fast Access Functions

Virtual storage mode

Description

Function vmode returns virtual storage modes of 'ram' or 'ff' objects, the generic vmode<- sets the vmode of ram objects (vmode of ff objects cannot be changed).

Usage

vmode(x, ...)
vmode(x) <- value
## Default S3 method:
vmode(x, ...)
## S3 method for class 'ff'
vmode(x, ...)
## Default S3 replacement method:
vmode(x) <- value
## S3 replacement method for class 'ff'
vmode(x) <- value
 regtest.vmode()

Arguments

x	any object
value	a vmode from .vmode
...	The ... don't have a function yet, they are only defined to keep the generic flexible.

Details

vmode is generic with default and ff methods. The following meta data vectors can be queried by .vmode or .ffmode:

.vmode	virtual mode
.vunsigned	TRUE if unsigned vmode
.vvalues	number of possible values (incl. NA)
.vimplemented	TRUE if this vmode is available in ff (initialized .onLoad and stored in globalenv )
.rammode	storage mode of this vmode
.ffmode	integer used to code the vmode in C-code
.vvalues	number of possible integers incl. NA in this vmode (or NA for other vmodes)
.vmin	min integer in this vmode (or NA for other vmodes)
.vmax	max integer in this vmode (or NA for other vmodes)
.vNA	NA or 0 if no NA for this vmode
.rambytes	bytes needed in ram
.ffbytes	bytes needed by ff on disk
.vcoerceable	list of vectors with those vmodes that can absorb this vmode

the following functions relate to vmode:

vector.vmode	creating (ram) vector of some vmode
as.vmode	generic for coercing to some vmode (dropping other attributes)
vmode<-	generic for coercing to some vmode (keeping other attributes)
maxffmode	determine lowest .ffmode that can absorb all input vmodes without information loss

some of those call the vmode-specific functions:

creation	coercion	vmode description
boolean	as.boolean	1 bit logical without NA
logical	as.logical	2 bit logical with NA
quad	as.quad	2 bit unsigned integer without NA
nibble	as.nibble	4 bit unsigned integer without NA
byte	as.byte	8 bit signed integer with NA
ubyte	as.ubyte	8 bit unsigned integer without NA
short	as.short	16 bit signed integer with NA
ushort	as.ushort	16 bit unsigned integer without NA
integer	as.integer	32 bit signed integer with NA
single	as.single	32 bit float
double	as.double	64 bit float
complex	as.complex	2x64 bit float
raw	as.raw	8 bit unsigned char
character	as.character	character

Value

vmode returns a character scalar from .vmode or "NULL" for NULL
rambytes returns a vector of byte counts required by each of the vmodes

Note

regtest.vmode checks correctness of some vmode features

Author(s)

Jens Oehlschlägel

See Also

ff, storage.mode, mode

Examples

 data.frame(.vmode=.vmode, .vimplemented=.vimplemented, .rammode=.rammode, .ffmode=.ffmode
, .vmin=.vmin, .vmax=.vmax, .vNA=.vNA, .rambytes=.rambytes, .ffbytes=.ffbytes)
  vmode(1)
  vmode(1L)
  .vcoerceable[["byte"]]
  .vcoerceable[["ubyte"]]

ff documentation built on Sept. 30, 2024, 9:38 a.m.