Provided by: libgetdata-doc_0.11.0-3ubuntu1_all 
NAME
dirfile-format — the dirfile database format specification file
DESCRIPTION
The dirfile format specification fully specifies the raw and derived time streams and
auxiliary information for a dirfile(5) database.
The format specification is contained in one or more case-sensitive text files located in
the dirfile tree. Each file is known as a fragment. The primary fragment is the file
called format located in the base dirfile directory. This file may contain only part of
the format specification, and may reference other fragments (using the /INCLUDE directive)
containing further format specification. This inclusion mechanism may be nested
arbitrarily deep.
The explicit text encoding of these files is not specified by these Standards, but it must
be 7-bit ASCII compatible. Examples of acceptable character encodings include all the
ISO 8859 character sets (i.e. Latin-1 through Latin-10, among others), as well as the
UTF-8 encoding of Unicode and UCS.
This document primarily describes the latest version of the Standards (Version 10);
differences with previous versions are noted where relevant. A complete list of changes
between versions is given in the HISTORY section below.
SYNTAX
The format specification is composed of field specification lines and directive lines,
optionally separated by blank lines or lines containing only whitespace. Lines are
separated by the line-feed character (0x0A). Unless escaped (see below), the hash mark
(#) is the comment delimiter; the comment delimiter, and any text following it to the end
of the line, is ignored.
Tokens
Both field specification lines and directive lines consist of several tokens separated by
whitespace. Whitespace consists of one or more whitespace characters. These are: space
(0x20), horizontal tab (0x09), vertical tab (0x0B), form-feed (0x0C), and carriage return
(0x0D). The first token of a directive line is always a reserved word. The first token
of a field specification line is never a reserved word. Any amount of whitespace may
precede the first token on a line.
Since tokens are separated by whitespace, to include a whitespace character in a token, it
must either escaped by preceding it by a backslash character (\), or be replaced by a
character escape sequence (see below), or else the token must be enclosed in quotation
marks ("). The quotation marks themselves are stripped from the token. The null-token
(that is, the token consisting of zero characters) may be specified by a pair of quotation
marks with nothing between them (""). To include a literal quotation mark in a token, it
must be escaped (\"). Similarly, a hash mark may be included in a token by including it
in a quoted token or else by escaping it (\#), otherwise the hash mark is understood as
the comment delimiter.
It is a syntax error to have a line which contains unmatched quotation marks, or in which
the last character is the backslash character.
Several characters when escaped by a preceding backslash character are interpreted as
special characters in tokens. The character escape sequences are:
\a an alert (bell) character (ASCII 0x07 / U+0007)
\b a backspace character (ASCII 0x08 / U+0008)
\e an escape character (ASCII 0x1B / U+001B)
\f a form-feed character (ASCII 0x0C / U+000C)
\n a line-feed character (ASCII 0x0A / U+000A)
\r a carriage return character (ASCII 0x0D / U+000D)
\t a horizontal tab character (ASCII 0x09 / U+0009)
\v a vertical tab character (ASCII 0x0B / U+000B)
\\ a backslash character (ASCII 0x5C / U+005C)
\ooo the single byte given by the octal number ooo (1 to 3 octal digits).
\xhh the single byte given by the hexadecimal number hh (1 or 2 hexadecimal
digits).
\uhhhhhhh
the UTF-8 byte sequence encoding the Unicode code point given by the
hexadecimal number hhhhhhh (1 to 7 hexadecimal digits).
Any other character which is escaped is interpreted as the character itself. (i.e. \c is
interpreted as c; also, as pointed out above, \" and \# are interpreted as simply " and #,
without their special meanings).
No token may contain the NULL character (ASCII 0x00 / U+0000). Furthermore, although
support is present to create UTF-8 byte sequences, tokens are not required to be valid
UTF-8 sequences. Any byte sequence not containing the NULL character forms a valid token.
However, there may be further restrictions on allowed characters for a token in a
particular situation, (for example, when used as a field name).
Standards Version 5 and earlier do not recognise the character escape sequences, nor allow
quoting of tokens. As a result, they prohibit both whitespace and the comment delimiter
from being used in tokens.
DIRECTIVES
There are ten directives, each specified by a different reserved word, which cannot be
used as field names in the dirfile. As of Standards Version 8, all reserved words start
with an initial forward slash (/), to distinguish them from field names. Standards
Versions 5, 6, and 7 permitted the omission of the initial forward slash, while in
Standards Version 4 and earlier, reserved words may not have an initial forward slash.
Like the rest of the format specification, directives are case sensitive.
A number of the directives have fragment scope. A directive with fragment scope only
applies to the fragment in which it is present, plus any sub-fragments indicated by the
/INCLUDE directive, but only if those sub-fragments don't have their own corresponding
directive. Directives which have fragment scope are: /ENCODING, /ENDIAN, /FRAMEOFFSET,
and /PROTECT. Because of these scoping rules, different portions of the dirfile may have
different encodings, endiannesses, frame offsets, or protection levels.
If a directive with fragment scope appears more than once in a fragment, only the last
such directive is honoured, with the exception that the effect of a directive is not
propagated to sub-fragments if the directive line appears after the sub-fragment is
included. The scoping rules of the remaining directives are discussed below.
/ALIAS The /ALIAS directive defines an alternate name for a field defined elsewhere in the
format specification (called the "target"). Aliases may not be used as the parent
field in a /META directive, but are in most other ways indistinguishable from the
target's original, canonical name. Aliases may be chained (that is, the target
name appearing in an /ALIAS directive may itself be an alias). In this case, the
new alias is another name for the target's own target. Just as there is no
requirement that the input fields of a derived field exist, it is not an error for
the target of an alias to not exist. Syntax is:
/ALIAS <name> <target>
A metafield alias may defined using the <parent-field>/<alias-name> syntax for name
in the /ALIAS directive. No restriction is placed on target; specifically, a
metafield alias may target a top-level field, or a metafield of with a different
parent; conversely, a top-level alias may target a metafield.
A metafield alias may never appear as the parent part of a metafield field code,
even if it refers to a top-level field. That is, given the valid format:
aaaa RAW UINT8 1
aaaa/bbbb CONST FLOAT64 0.0
cccc RAW UINT8 1
/ALIAS cccc/dddd aaaa
the metafield aaaa/bbbb may not be referred to as cccc/dddd/bbbb, even though
cccc/dddd is a valid field code referring to aaaa.
This is not true of top-level aliases: if eeee is an alias of ffff, then ffff/gggg,
a metafield of ffff, may be referred to as eeee/gggg as well.
The /ALIAS directive has no scope: it is processed immediately. It appeared in
Standards Version 9.
/ENCODING
The /ENCODING directive specifies the encoding scheme used to encode binary files
in the dirfile. The encoding scheme may be one of the predefined names listed
below, which are described in more detail in dirfile-encoding(5), or any other
site-specific encoding scheme. The predefined scheme names are:
none The dirfile is unencoded.
bzip2 The dirfile is compressed using the bzip2 compression scheme.
flac The dirfile is compressed using the flac compression scheme.
gzip The dirfile is compressed using the gzip compression scheme.
lzma The dirfile is compressed using the LZMA compression scheme.
slim The dirfile is compressed using the slim compression scheme.
sie The dirfile is sample-index encoded (a variant of run-length encoding).
text The dirfile is text encoded.
zzip The dirfile is compressed and encapsulated using the zzip compression
scheme.
zzslim The dirfile is compressed and encapsulated using a combination of the zzip
and slim compression schemes.
Implementations should fail gracefully when encountering an unknown encoding
scheme. If no encoding scheme is specified, behaviour is implementation dependent.
Syntax is:
/ENCODING <scheme> [<enc-datum>]
The enc-datum token provides additional data for certain encoding schemes; see
dirfile-encoding(5) for details. The form of enc-datum is not specified.
The /ENCODING directive has fragment scope. It appeared in Standards Version 6.
The predefined schemes sie, zzip, and zzslim, and the optional enc-datum token,
appeared in Standards Version 9; the predefined scheme lzma appeared in Standards
Version 7; all other predefined schemes appeared in Standards Version 6.
/ENDIAN
The /ENDIAN directive specifies the endianness of the raw data in the database.
The assumed endianness of raw data in dirfiles which omit this directive is
implementation dependent. Syntax is:
/ENDIAN ( big | little ) [ arm ]
where the "arm" token should be included if double precision floating point data
are stored in the ARM middle-endian format. The /ENDIAN directive has fragment
scope. It appeared in Standards Version 5. The optional arm token appeared in
Standards Version 8.
/FRAMEOFFSET
The /FRAMEOFFSET directive specifies the frame number of the first frame for which
data exists in binary files associated with RAW fields. Syntax is:
/FRAMEOFFSET <integer>
The /FRAMEOFFSET directive has fragment scope. It appeared in Standards Version 1.
/HIDDEN
The /HIDDEN directive indicates that the specified field name is hidden. The
difference (if any) between a field name which is hidden and one that is not is
implementation dependent. Hiddenness is not inherited by metafields of the
specified field. Hiddenness applies to the name, not the field itself; it does not
hide all aliases of the field-name, and if field-name an alias, the alias is
hidden, not its target. Syntax is:
/HIDDEN <field-name>
A /HIDDEN directive must appear after the specification of field-name, (which
occurs either in a field specification line, or an /ALIAS directive, or a /META
directive) in the same fragment.
The /HIDDEN directive has no scope: it is processed immediately. It appeared in
Standards Version 9.
/INCLUDE
The /INCLUDE directive specifies another file (called a fragment) to parse for
additional format specification for the dirfile. The inclusion is processed
immediately, before the fragment containing the /INCLUDE directive (the parent
fragment) is parsed further. RAW fields specified in the included fragment are
located in the directory containing the fragment file, and not in the directory
containing the parent fragment, and the binary file encoding may be different for
each fragment. The fragment may be specified either with an absolute path, or else
a path relative to the directory containing the parent fragment.
The /INCLUDE directive may optionally specify a prefix and/or suffix to apply to
field names defined in the included fragment. If present, affixes are applied to
all field-names (including aliases) defined in the included fragment and any
fragments it further includes. Affixes nest, with the affixes of the deepest
inclusion innermost. Affixes are not applied to the names of binary files
associated with RAW fields. Syntax is:
/INCLUDE <file> [<namespace>.][<prefix>] [<suffix>]
To specify only suffix, the null-token ("") may be used as prefix.
A namespace may also be specified in an /INCLUDE directive by prepending it to
prefix. The namespace and prefix are separated by a dot (.). The dot is required
whenever a namespace is specified: if the prefix is empty, the third token should
be just the namespace followed by a trailing dot. If a namespace is specified,
that namespace, relative to the including fragment's root namespace, becomes the
root namespace of the included fragment. If no namespace is specified in the
/INCLUDE directive, then the current namespace (specified by a previous /NAMESPACE
directive) is used as the root namespace of the included fragment. That is, if the
current namespace is current_space, then the statement:
/INCLUDE file newspace.
is equivalent to
/NAMESPACE newspace
/INCLUDE file
/NAMESPACE current_space
As a result, if no namespace is provided, and there has been no previous /NAMESPACE
directive, the included fragment will have the same root namespace as the including
fragment.
The /INCLUDE directive has no scope: it is processed immediately. It appeared in
Standards Version 3. The optional prefix and suffix appeared in Standards Version
9. The optional namespace appeared in Standards Version 10.
/META The /META directive specifies a metafield attached to a particular parent field.
The field metadata may be of any allowed type except RAW. Metafields are retrieved
in exactly the same way as regular field data, but the field code specified
consists of the parent and metafield names joined with a forward slash:
<parent-field>/<meta-field>
META fields may not be specified before their parent field has been. Syntax is:
/META <parent-field> {field specification line}
The <parent-field> code may not be an alias. As an illustration of this concept,
/META pfield meta CONST FLOAT64 3.291882
provides a scalar metadatum called meta with value 3.291882 attached to the field
pfield. This particular metafield may be referred to by the field code
"pfield/meta". Note that different parent fields may have metafields with the same
name, since all references to metafields must include the parent field name.
Metafields may not themselves have further sub-metafields.
As an alternative to the /META directive, starting with Standards Version 7, a
metafield may be specified by a standard field specification line, using
<parent-field>/<meta-field>
as the field name. That is, the above example metafield could have also been
specified as:
pfield/meta CONST FLOAT64 3.291882
The /META directive has no scope: it is processed immediately. It appeared in
Standards Version 6.
/NAMESPACE
The /NAMESPACE directive changes the current
namespaceforsubsequentfieldspecificationlines. Syntax is:
/NAMESPACE <subspace>
The subspace specified is relative to the current fragment's root namespace. If
subspace is the null-token ("") the current namespace will be set back to the root
namespace. Otherwise, the current namespace will be changed to the concatenation
of the root namespace with subspace, with the two parts separated by a dot:
rootspace.subspace
If rootspace is empty, the intervening dot is omitted, and the current namespace is
simply subspace.
By default, all field codes, both field names for newly specified fields, and field
codes used as inputs to fields or targets for aliases, are placed in the current
namespace, unless they start with an initial dot, in which case the current
namespace is ignored, and they're placed instead in the fragment's root namespace.
See the Namespaces section for further details.
The /NAMESPACE directive has no scope: it is processed immediately. For the
effects of changing the current namespace on included fragments, see the /INCLUDE
directive above. The effects of a /NAMESPACE directive never propagate upwards to
parent fragments. It appeared in Standards Version 10.
/PROTECT
The /PROTECT directive specifies the advisory protection level of the current
fragment and of the RAW fields defined therein. The protection level indicates
whether writing to the fragment, or the binary data on disk is permitted. Syntax
is:
/PROTECT <level>
Four advisory protection levels are defined:
none No protection at all: data and metadata may be freely changed. This is the
default, if no /PROTECT directive is present.
format The dirfile metadata is protected from change, but RAW data on disk may be
modified.
data The RAW data on disk is protected from change, but metadata may be modified.
all Both metadata and data on disk are protected from change.
The /PROTECT directive has fragment scope. It appeared in Standards Version 6.
/REFERENCE
The /REFERENCE directive specifies the name of the field to use as the dirfile's
reference field (see dirfile(5)). If no /REFERENCE directive is specified, the
first RAW field encountered is used as the reference field. The /REFERENCE
directive must specify a RAW field. Syntax is:
/REFERENCE <field-code>
The /REFERENCE directive has global scope: if multiple /REFERENCE directives appear
in the dirfile metadata, only the last such is honoured. It appeared in Standards
Version 6.
/VERSION
The /VERSION directive specifies the particular version of the Dirfile Standards to
which the dirfile format specification conforms. This directive should occur
before any version dependent syntax is encountered. As of Standards Version 6, no
such syntax exists, and this directive is provided primarily to ease forward
compatibility. Syntax is:
/VERSION <integer>
The /VERSION directive has immediate scope: its effect is immediate, and it applies
only to metadata below it, including and propagating downwards to sub-fragments
after the directive.
In Standards Version 8 and earlier, its effect also propagates upwards back to the
parent fragment, and affects subsequent metadata. Starting with Standards Version
9, this no longer happens. As a result, a /VERSION directive which indicates a
version of 9 or later never propagates upwards; additionally, /VERSION directives
found in subfragments included in a Version 9 or later fragment aren't propagated
upwards into that fragment, regardless of the Version of the subfragments. The
/VERSION directive appeared in Standards Version 5.
FIELD SPECIFICATION LINES
Any line which does not start with a reserved word is assumed to be a field specification
line. A field specification line consists of at least two tokens. The first token is the
field name. The second token is the field type. Subsequent tokens are field parameters.
The meaning and number these parameters depends on the field type specified.
Field Names
The first token in a field specification line is the field name. The field name consists
of one or more characters, excluding both ASCII control characters (the bytes 0x01 through
0x1F), and the characters
& / ; < > | .
which are reserved (but see below for the use of / to specify metafields). The dot (.)
is allowed in Standards Version 5 and earlier. The ampersand, semicolon, less-than sign,
greater-than sign, and vertical line (& ; < > |) are allowed in Standards Version 4 and
earlier. Furthermore, due to the lack of an escape or quoting mechanism (see Tokens
above), Standards Version 5 and earlier also prohibit whitespace and the comment delimiter
(#) in field names.
The field name may not be INDEX, which is a special, implicit field which contains the
integer frame index. Standards Version 5 and earlier also prohibit FILEFRAM, which was an
alias for INDEX. Field names are case sensitive. Standards Version 3 and 4 restrict
field names to 50 characters. Standards Version 2 and earlier restrict field names to 16
characters. Additionally, the filesystem may put restrictions on the length and acceptable
characters of a RAW field name, regardless of Standards Version.
Starting in Standards Version 7, if the field name beginning a field specification line
contains exactly one forward slash character (/), the line is assumed to specify a
metafield. See the /META directive above for further details. A field name may not
contain more than one forward slash.
Starting in Standards Version 10, any field name may be preceded by a namespace tag. The
namespace tag and the field name are separated by a dot (.). See the Namespaces section,
following, for details.
Namespaces
Beginning with Standards Version 10, every field in a Dirfile is contained in a namespace.
Every namespace is identified by a namespace tag which consist of the same restricted set
of characters used for field names. Namespaces nest arbitrarily deep. Subnamespaces are
identified by concatenating all namespace tags, separating tags by dots (.), with the
outermost namespace leftmost:
topspace.subspace.subsubspace
Each fragment has an immutable root namespace. The root namespace of the primary format
file is the null namespace, identified by the null-token (""). The root namespace of
other fragments is specified when they are introduced (see the /INCLUDE directive). Each
fragment also has a current namespace which may be changed as often as needed using the
/NAMESPACE directive, and defaults to the root namespace. The current namespace is always
either the root namespace or else a subspace under the root namespace.
If a field name or field code starts with a leading dot, then that name or code is taken
to be relative to the fragment's root space. If it does not start with a dot, it is taken
to be relative to the current namespace.
For example, if the both the root namespace and current namespace of a fragment start off
as rootspace, then:
aaaa RAW UINT8 1
.bbbb RAW UINT8 1
cccc.dddd RAW UINT8 1
.eeee.ffff RAW UINT8 1
/NAMESPACE newspace
gggg RAW UINT8 1
.hhhh RAW UINT8 1
iiii.jjjj RAW UINT8 1
.kkkk.llll RAW UINT8 1
specifies, respectively, the fields:
rootspace.aaaa,
rootspace.bbbb,
rootspace.cccc.dddd,
rootspace.eeee.ffff,
rootspace.newspace.gggg,
rootspace.hhhh,
rootspace.newspace.iiii.jjjj, and
rootspace.kkkk.llll.
Note that a field may specify deeper subspaces under either the root namespace or the
current namespace (meaning it is never necessary to use the /NAMESPACE directive). Note
also that there is no way for metadata in a given fragment to refer to fields outside the
fragment's root space.
There is one exception to this namespace scoping rule: the implicit INDEX vector is always
in the null (top-level) namespace, and namespace tags specified with it, either explicitly
or implicitly, even a fragment root namespace, are ignored. So, in a fragment with root
namespace rootspace, and current namespace rootspace.subspace,
INDEX,
.INDEX,
namespace.INDEX, and
.namespace.INDEX,
all refer to the same INDEX field.
Field Types
There are eighteen field types. Of these, fourteen are of vector type (BIT, DIVIDE,
INDIR, LINCOM, LINTERP, MPLEX, MULTIPLY, PHASE, POLYNOM, RAW, RECIP, SBIT, SINDIR, and
WINDOW) and four are of scalar type (CARRAY, CONST, SARRAY, and STRING). The thirteen
vector field types other than RAW fields are also called derived fields, since they derive
their value from one or more input vector fields. Any other vector field may be used as
an input vector, including the implicit INDEX field, but excluding SINDIR string vectors.
Five of these derived fields (DIVIDE, LINCOM, MPLEX, MULTIPLY, and WINDOW) have more than
one vector input field. In situations where these input fields have differing sample
rates, the sample rate of the derived field is the same as the sample rate of the first
(left-most) input field specified. Furthermore, the input fields are synchronised by
aligning them on frame boundaries, assuming equally-spaced sampling throughout a frame,
and using the last sample of each input field which did not occur after the sample of the
derived field being computed. That is, if the first and second input fields have sample
rates s1 and s2, the derived field also has sample rate s1 and, for every sample of the
derived field, n, the n'th sample of the first field is used (since they have the same
sample rate by definition), and the sample number used of the second field, m, is computed
as:
m = floor((n * s2) / s1).
Starting in Standards Version 6, certain scalar field parameters in the field
specifications may be specified using CONST or CARRAY fields, instead of literal values.
A list of parameters for which this is allowed is given below in the Field Parameters
section.
The possible fields types are:
BIT The BIT vector field type extracts one or more bits out of an input vector field as
an unsigned number. Syntax is:
<fieldname> BIT <input> <first-bit> [<num-bits>]
which specifies fieldname to be num-bits bits extracted from the input vector field
input starting with bit number first-bit (counting from the least-significant bit,
which is numbered zero), after input has been converted from its native type to an
(endianness corrected) unsigned 64-bit integer. If num-bits is omitted, it is
assumed to be one.
The extracted bits are interpreted as an unsigned integer; the SBIT field type is a
signed version of this field type. The optional num-bits parameter appeared in
Standards Version 1.
CARRAY The CARRAY scalar field type is a list of constants fully specified in the format
specification metadata. Syntax is:
<fieldname> CARRAY <type> <value0> <value1> <value2> ...
where type may be any supported native data type (see the description of the RAW
field type below), and value0, value1, &c. are the values of successive elements in
the scalar list interpreted as indicated by type. No limit is placed on the number
of elements in a CARRAY. (Note: despite being multivalued, this is not considered
a vector field since the elements of the CARRAY are not indexed by frames.) CARRAY
appeared in Standards Version 8.
CONST The CONST scalar field type is a constant fully specified in the format
specification metadata. Syntax is:
<fieldname> CONST <type> <value>
where type may be any supported native data type (see the description of the RAW
field type below), and value is the numerical value of the constant interpreted as
indicated by type. CONST appeared in Standards Version 6.
DIVIDE The DIVIDE vector field type is the quotient of two vector fields. Syntax is:
<fieldname> DIVIDE <field1> <field1>
The derived field is computed as:
fieldname = field1 / field2.
It was introduced in Standards Version 8.
INDIR The INDIR vector field type performs an indirect translation of a CARRAY scalar
field to a derived vector field based on a vector index field. Syntax is:
<fieldname> INDIR <index> <array>
where index is the vector field, which is converted to an integer type, if
necessary, and array is the CARRAY field. The nth sample of the INDIR field is the
value of the mth element of array (counting from zero), where m is the value of the
nth sample of index. When index is not a valid element number of array, the
corresponding value of the INDIR is implementation dependent. INDIR appeared in
Standards Version 10.
LINCOM The LINCOM vector field type is the linear combination of one, two or three input
vector fields. Syntax is:
<fieldname> LINCOM [<n>] <field1> <a1> <b1> [<field2> <a2> <b2> [<field3>
<a3> <b3>]]
where n, if present, indicates the number of input vector fields (1, 2, or 3). The
derived field is computed as:
fieldname = (a1 * field1 + b1) + (a2 * field2 + b2) + (a3 * field3 + b3)
with the field2 and field3 terms included only if specified.
If n is not specified, the number of fields is determined by looking at the
supplied parameters. Since it is possible to create a field code which is
identical to a literal number, the third token on the line is assumed to be n if it
the entire token can be parsed as a literal number using the rules outlined in
strtod(3). That is, if the field code specifying field1 could be mistaken for a
literal number, n must be specified to prevent ambiguity. In standards Version 6
and earlier, n is mandatory.
LINTERP
The LINTERP vector field type specifies a table look up based on another vector
field. Syntax is:
<fieldname> LINTERP <input> <table>
where input is the input vector field for the table lookup, and table is the path
to the lookup table file for the field. If this path is relative, it is assumed to
be relative to the directory containing the fragment defining this field. The
lookup table file is an ASCII text file with two whitespace separated columns of x
and y values. Values are linearly interpolated between the points specified in the
lookup table.
MPLEX The MPLEX vector field type permits the multiplexing of several low sample rate
fields into a single data field of higher sample rate. Syntax is:
<fieldname> MPLEX <input> <index> <count> [<period>]
where input is the input vector containing the multiplexed fields, index is the
vector containing the mutliplex index, count is the value of the multiplex index
when the computed field is stored in input, and period, if present and non-zero, is
the number of samples between successive occurrances of the value count in the
index vector. A period of zero (or, equivalently, it's omission) indicates that
either the value count is not equally spaced in the index vector, or else that the
spacing is unknown. Both count and period are integers, and period may not be
negative.
At every sample n, the derived field is computed as:
fieldname[n] = (index == count) ? input[n] : fieldname[n - 1]
The index vector is converted to an integer type for comparison. The value of the
derived field before the first sample where index equals count is implementation
dependent.
The values of count and period place no restrictions on values contained in index.
Specifically, particular values of index (including count) need not be equally
spaced (neither by period nor any other spacing); index need not ever take on the
value count (in which case the value of the entirety of the derived field is
implementation dependent). Different MPLEX field definitions which use the same
index vector may specify different periods. MPLEX appeared in Standards Version 9.
MULTIPLY
The MULTIPLY vector field type is the product of two vector fields. Syntax is:
<fieldname> MULTIPLY <field1> <field2>
The derived field is computed as:
fieldname = field1 * field2.
MULTIPLY appeared in Standards Version 2.
PHASE The PHASE vector field type shifts an input vector field by the specified number of
samples. Syntax is:
<fieldname> PHASE <input> <shift>
which specifies fieldname to be the input vector field, input, shifted by shift
samples. A positive shift indicates a forward shift, towards the end-of-field.
Results of shifting past the beginning- or end-of-field is implementation
dependent. PHASE appeared in Standards Version 4.
POLYNOM
The POLYNOM vector field type specifies a polynomial function of a single input
vector field. Syntax is:
<field_name> POLYNOM <input> <a0> <a1> [<a2> [<a3> [<a4> [<a5>]]]]
where <input> is the input field code, and the order of the computed polynomial is
determined by how many co-efficients are present in the specification. The derived
field is computed as:
fieldname = a0 + a1 * input + a2 * input**2 + a3 * input**3 + a4 * input**4
+ a5 * input**5
where ** is the element-wise exponentiation operator, and the higher order terms
are computed only if the corresponding co-efficients ai are specified. POLYNOM
appeared in Standards Version 7.
RAW The RAW vector field type specifies raw time streams on disk. In this case, the
field name should correspond to the name of the file containing the time stream.
Syntax is:
<fieldname> RAW <type> <sample-rate>
where sample-rate is the number of samples per dirfile frame for the time stream
and type is a token specifying the native data type:
UINT8 unsigned 8-bit integer
INT8 two's complement signed 8-bit integer
UINT16 unsigned 16-bit integer
INT16 two's complement signed 16-bit integer
UINT32 unsigned 32-bit integer
INT32 two's complement signed 32-bit integer
UINT64 unsigned 64-bit integer
INT64 two's complement signed 64-bit integer
FLOAT32
IEEE-754 standard 32-bit single precision floating point number
FLOAT64
IEEE-754 standard 64-bit double precision floating point number
COMPLEX64
a 64-bit complex number consisting of two IEEE-754 standard 32-bit
single precision floating point numbers representing the real and
imaginary parts of the complex number (Standards Version 7 and later)
COMPLEX128
a 128-bit complex number consisting of two IEEE-754 standard 64-bit
double precision floating point numbers representing the real and
imaginary parts of the complex number (Standards Version 7 and
later).
For more information on the storage of complex valued data, see dirfile(5). Two
additional type names exist: FLOAT is equivalent to FLOAT32, and DOUBLE is
equivalent to FLOAT64. Standards Version 9 deprecates these two aliases, but still
allows them.
All these type names (except those for complex data, which came later) were
introduced in Standards Version 5. Earlier Standards Versions specified data types
with single-character type aliases:
c UINT8
u UINT16
s INT16
U UINT32
i, S INT32
f FLOAT32
d FLOAT64
Types INT8, UINT64, INT64, COMPLEX64, and COMPLEX128 are not supported before
Standards Version 5, so no single-character type aliases exist for these types.
These single-character type aliases were deprecated in Standards Version 5 and
removed in Standards Version 8.
RECIP The RECIP vector field type computes the reciprocal of a single input vector field.
Syntax is:
<field_name> RECIP <input> <dividend>
where <input> is the input field code and <dividend> is a scalar quantity. The
derived field is computed as:
fieldname = dividend / input.
RECIP appeared in Standards Version 8.
SARRAY The SARRAY scalar field type is a list of strings fully specified in the format
file metadata. Syntax is:
<fieldname> SARRAY <string0> <string1> <string2> ...
Each string is a single token. To include whitespace in a string, enclose it in
quotation marks ("), or else escape the whitespace with the backslash character
(\). No limit is placed on the number of elements in a SARRAY. SARRAY appeared in
Standards Version 10.
SBIT The SBIT vector field type extracts one or more bits out of an input vector field
as a (two's-complement) signed number. Syntax is:
<fieldname> SBIT <input> <first-bit> [<num-bits>]
which specifies fieldname to be num-bits bits extracted from the input vector field
input starting with bit number first-bit (counting from the least-significant bit,
which is numbered zero), after input has been converted from its native type to an
(endianness corrected) two's complement signed 64-bit integer. If num-bits is
omitted, it is assumed to be one.
The extracted bits are interpreted as a two's complement signed integer of the
specified width. (So, if num-bits is, for example, one, then the field can take on
the value zero or negative one.) The BIT field type is an unsigned version of this
field type. SBIT appeared in Standards Version 7.
SINDIR The SINDIR vector field type performs an indirect translation of a SARRAY scalar
field to a derived vector field of strings based on a vector index field. Syntax
is:
<fieldname> SINDIR <index> <array>
where index is the vector field, which is converted to an integer type, if
necessary, and array is the SARRAY field. The nth sample of the SINDIR field is
the string value of the mth element of array (counting from zero), where m is the
value of the nth sample of index. When index is not a valid element number of
array, the corresponding value of the SINDIR is implementation dependent. SINDIR
appeared in Standards Version 10.
STRING The STRING scalar field type is a character string fully specified in the format
file metadata. Syntax is:
<fieldname> STRING <string>
where string is the string value of the field. Note that string is a single token.
To include whitespace in the string, enclose string in quotation marks ("), or else
escape the whitespace with the backslash character (\). STRING appeared in
Standards Version 6.
WINDOW The WINDOW vector field type isolates a portion of an input vector based on a
comparison. Syntax is:
<fieldname> WINDOW <input> <check> <op> <threshold>
where input is the vector containing the data to extract, check is the vector on
which to test the comparison, threshold is the value against which check is
compared, and op is one of the following tokens indicating the particular
comparison performed:
EQ data are extracted where check, converted to a 64-bit signed integer,
equals threshold,
GE data are extracted where check, converted to a 64-bit floating-point
number, is greater than or equal to threshold,
GT data are extracted where check, converted to a 64-bit floating-point
number, is strictly greater than threshold,
LE data are extracted where check, converted to a 64-bit floating-point
number, is less than or equal to threshold,
LT data are extracted where check, converted to a 64-bit floating-point
number, is strictly less than threshold,
NE data are extracted where check, converted to a 64-bit signed integer,
is not equal to threshold,
SET data are extracted where at least one bit set in threshold is also
set in check, when converted to a 64-bit unsigned integer,
CLR data are extracted where at least one bit set in threshold is not set
in check, when converted to a 64-bit unsigned integer,
The storage type of threshold depends on the operator, and follows the
interpretation of check. It may never be complex valued.
Outside the region extracted, the value of the derived field is implementation
dependent.
Note: with the EQ operator, this derived field type is very similar to the MPLEX
field type above. The primary difference is that MPLEX mandates the value of the
derived field outside the extracted region, while WINDOW does not. WINDOW appeared
in Standards Version 9.
Field Parameters
All input vector field parameters should be field codes (see below). Additionally, the
scalar field parameters listed may be either literal numbers or else the field code of a
CONST field containing the value, or the field code of a CARRAY followed by a left angle
bracket (<), then an non-negative integer used as the CARRAY element index, then a right
angle bracket (>), that is:
fieldcode<n>
If the angle brackets and element index are omitted from a CARRAY field code used as a
parameter, the first element in the field (index zero) is assumed.
Field parameters which may be specified using a scalar field code are:
BIT, SBIT
bitnum, numbits
LINCOM any of the mi, or bi
MPLEX count, max
PHASE shift
POLYNOM
any of the ai
RAW spf
RECIP dividend
WINDOW threshold
Since it is possible to create a field code which is identical to a literal number, a
parameter is assumed to be the field code of a scalar field only if the entire token
cannot be parsed as a literal number using the rules outlined in strtod(3). For example,
a CONST field whose field code consists solely of digits can never be used as a parameter
in a field specification line.
Starting in Standards Version 7, literal complex number is specified as two real (floating
point) numbers separated by a semicolon (;) with no intervening whitespace. So, for
example, the tokens
1;0 0;1 4;0 0;5 9.313e2;74.1
represent, respectively, the real unit, the imaginary unit, the real number four, the
imaginary number 5i, and the complex number 931.3 + 74.1i. Because the semicolon
character cannot be used in field names, a complex valued literal can never be mistaken
for a field code. This allows, among other things, the composition of complex valued
fields from purely real input fields. For example, a complex valued field, z, may be
created from a real valued field re, representing the real part of the complex number, and
the real valued field im, representing the imaginary part of the complex number, with the
following LINCOM specification:
z LINCOM re 1 0 im 0;1 0
Starting in Standards Version 9, in additional to decimal notation, literal integer
parameters may be specified as hexadecimal numbers, by prefixing the number (after an
optional '+' or '-' sign) with 0x or 0X, or as octal numbers, by prefixing the number with
0, as described in strtol(3). Similarly, floating point literal numbers (both purely real
ones and components of complex literals) may be specified in hexadecimal by prefixing them
with 0x or 0X, and using p or P as the binary exponent prefix, as described in the C99
standard. Both uppercase and lowercase hexadecimal digits may be used. In cases where a
literal floating point number may apear, the tokens INF or INFINITY, optionally preceded
by a '+' or '-' sign, and NAN, optionally immediately followed by '(', then a sequence of
characters, then ')', and all disregarding case, will be interpreted as the special
floating point values explained in strtod(3).
Field Codes
When specifying the input to a field, either as a scalar parameter, or as an input vector
field to a non-RAW vector field, field codes are used. A field code consists of, in
order:
• (since Standards Version 10:) optonally, a leading dot (.), indicating this field code
is relative to the fragment's root namespace. Without the leading dot, the field code
is taken to be relative to the current namespace. (See the discussion in the
Namespaces section above for details.)
• (since Standards Version 10:) optionally, a non-null subnamespace followed by a dot
(.) indicating a subspace under the current or root namespace. The subnamespace may
be made up of any number of namespace tags separated by dots, to nest deeper in the
namespace tree.
• (since Standards Version 6:) if the field in question is a metafield (see the /META
directive above), the field name of the metafield's parent (which may be an alias)
followed by a forward slash (/).
• a simple field name, possibly an alias, indicating a vector or scalar field
• (since Standards Version 7:) optionally, a dot (.) followed by a representation
suffix.
A representation suffix may be used used to extract a real number from a complex value.
The available suffixes (listed here with their preceding dot) and their meanings are:
.a the argument of the input, that is, the angle (in radians) between the positive
real axis and the input. The argument is in the range [-pi, pi], and a branch cut
exists along the negative real axis. At the branch cut, -pi is returned if the
imaginary part is -0, and pi is returned if the imaginary part is +0. If the input
is zero, zero is returned.
.i the imaginary part of the input (i.e. the projection of the input onto the
imaginary axis)
.m the modulus of the input (i.e. its absolue value).
.r the real part of the input (i.e. the projection of the input onto the real axis)
.z (since Standards Version 10:) the identity representation: it returns the full
complex value, equivalent to simply omitting the suffix completely. It is only
needed in certain cases to force the correct interpretation of a field code in the
presence of a namespace tag. To wit, the field code
name.r
may be interpreted as the real-part (via the .r representation suffix) of the field
called name. (if such a field exists). To refer to a field called r in the name
namespace, the field code must be written:
name.r.z
NB: The first interpretation only occurs with valid representation suffixes; the
field code:
name.q
is interpreted as the field q in the name namespace because .q is not a valid
representation suffix. Furthermore, ambiguity arises only if both fields "name"
and "name.r" are defined. if the field "name" does not exist, but the field
"name.r" does, then the original field code is not ambiguous. This is the only
representation suffix allowed on SARRAY, SINDIR, and STRING field codes.
If the specified field is purely real, representations are calculated as if the imaginary
part were equal to +0.
HISTORY
This document describes Versions 10 and earlier of the Dirfile Standards.
Version 10 of the Standards (January 2017) added the INDIR, SARRAY, and SINDIR field
types, namespaces, the /NAMESPACE directive, the flac encoding scheme, and the .z
representation suffix.
Version 9 of the Standards (April 2012) added the MPLEX and WINDOW field types, the /ALIAS
and /HIDDEN directives, the affixes to /INCLUDE, the sie, zzip, and zzslim encoding
schemes, along with the optional enc_datum token to /ENCODING. It permitted specification
of integer literals in octal and hexadecimal. Finally, it deprecated the type aliases
FLOAT and DOUBLE.
Version 8 of the Standards (November 2010) added the DIVIDE, RECIP, and CARRAY field
types, made the forward slash on reserved words mandatory, and prohibited using the
single-character type aliases in the specification of RAW fields. It also introduced the
optional second (arm) token to the /ENDIAN directive.
Version 7 of the Standards (October 2009) added the SBIT and POLYNOM field types, and the
directive-less method of specifying metafields. It also introduced the data types
COMPLEX128 and COMPLEX64, along with the notion of representations, and the lzma encoding
scheme. Finally, it made the number of fields parameter for LINCOM optional.
Version 6 of the Standards (October 2008) added the /ENCODING, /META, /PROTECT, and
/REFERENCE directives, and the CONST and STRING field types. It permitted whitespace in
tokens and introduced the character escape sequences. It allowed CONST fields to be used
as parameters in field specification lines. It also removed FILEFRAM as an alias for
INDEX, and prohibited . but allowed # and \ in field names.
Version 5 of the Standards (August 2008) added VERSION and ENDIAN, slash demarcation of
reserved words, and removed the restriction on field name length. It introduced the data
types INT8, INT64, and UINT64, the new-style type specifiers, and increased the range of
the BIT field type from 32 to 64 bits. It also prohibited the characters &;<>\| in field
names.
Version 4 of the Standards (October 2006) added the PHASE field type.
Version 3 of the Standards (January 2006) added INCLUDE and increased the allowed length
of a field name from 16 to 50 characters.
Version 2 of the Standards (September 2005) added the MULTIPLY field type.
Version 1 of the Standards (November 2004) added FRAMEOFFSET and the optional fourth
argument to the BIT field type.
Version 0 of the Standards (before March 2003) refers to the dirfile standards supported
by the getdata(3) library originally introduced into the kst(1) sources, which contained
support for all other features covered by this document.
AUTHORS
The dirfile specification was developed by C. B. Netterfield
<netterfield@astro.utoronto.ca>.
Since Standards Version 3, the dirfile specification has been maintained by D. V. Wiebe
<getdata@ketiltrout.net>.
SEE ALSO
dirfile(5), dirfile-encoding(5)