ff: vmode – R documentation

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vmode

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

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

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

v4.0.4

GPL-2 | GPL-3 | file LICENSE

Authors

Daniel Adler [aut], Christian Gläser [aut], Oleg Nenadic [aut], Jens Oehlschlägel [aut, cre], Martijn Schuemie [aut], Walter Zucchini [aut]

Initial release

2020-10-13