Members available in the gd_entry_t structure depend on the field type described. All gd_entry_t objects
are guaranteed to have at least:
typedef struct {
...
const char *field; /* field code */
gd_entype_t field_type; /* field type */
int fragment_index; /* format fragment index */
unsigned flags; /* entry flags */
...
} gd_entry_t;
The field member is the field code of the entry (i.e. its string name). If the call to gd_entry(3) is
successful, this will be the field name specified as part of the field_code argument.
The field_type member indicates the field type of the entry. This is an integer type equal to one of the
following symbols:
GD_BIT_ENTRY, GD_CARRAY_ENTRY, GD_CONST_ENTRY, GD_DIVIDE_ENTRY, GD_INDEX_ENTRY, GD_LINCOM_ENTRY,
GD_LINTERP_ENTRY, GD_MPLEX_ENTRY, GD_MULTIPLY_ENTRY, GD_PHASE_ENTRY, GD_POLYNOM_ENTRY,
GD_RAW_ENTRY, GD_RECIP_ENTRY, GD_SBIT_ENTRY, GD_STRING_ENTRY, GD_WINDOW_ENTRY.
GD_INDEX_ENTRY is a special field type used only for the implicit INDEX field. The other entry types are
explained in detail in dirfile-format(5).
The fragment_index member indicates the format specification fragment in which this field is defined.
This is an integer index to the Dirfile's list of parsed format specification fragments. The name of the
file corresponding to fragment_index may be obtained by calling gd_fragmentname(3). A value of zero for
this field indicates that the field is defined in the primary fragment, the file called format in the
root dirfile directory (see dirfile(5)).
The flags member is a bitwise or'd collection of the following entry flags:
GD_EN_CALC
This bit is set only when the non-literal scalar parameter field codes specified in the scalar
member have been resolved, and the corresponding numerical parameter have been initialised with
these data. When one or more field code does not exist, or is invalid (ie. when gd_validate(3)
would fail on the specified field_code with the error GD_E_BAD_SCALAR), then the unresolved nu‐
merical parameters are initialised to zero, and this flag is not be set. If the requested field
does not allow non-literal scalar parameters (CARRAY, CONST, DIVIDE, INDEX, LINTERP, MULTIPLY,
STRING), the value of this bit is unspecified.
GD_EN_COMPSCAL
For fields which permit complex valued parameters (LINCOM, POLYNOM, RECIP), this bit is set only
when at least one parameter is complex valued. For other field types, the value of this bit is
unspecified.
GD_EN_HIDDEN
This bit is set only when the field has been hidden by the /HIDDEN directive (see gd_hidden(3)).
Remaining fields in the gd_entry_t structure depend on the value of field_type. Callers are advised to
check field_type before attempting to access the remaining members. Members for different field types
may be stored in the same physical location in core. Accordingly, attempting to access a member not de‐
clared for the appropriate field type will have unspecified results.
ScalarParameterMembers
A gd_entry_t describing any field type which permits non-literal scalar field parameters (BIT, LINCOM,
MPLEX, PHASE, POLYNOM, RAW, RECIP, SBIT, or WINDOW) will also provide:
typedef struct {
...
const char *scalar[GD_MAX_POLY_ORD + 1]; /* param. fields */
int scalar_ind[GD_MAX_POLY_ORD + 1];
/* CARRAY indices */
...
} gd_entry_t;
Only certain elements of these arrays will be initialised:
• For BIT and SBIT fields, the first element corresponds to bitnum and the second to numbits. The
remainder are uninitialised.
• For LINCOM fields, the first GD_MAX_LINCOM elements correspond to the slopes (cm) and the next
GD_MAX_LINCOM elements correspond to the offsets (cb). Only the first n_fields elements of these
two sets are initialised. Notably, this means for n_fields < GD_MAX_LINCOM, there will be unini‐
tialised elements in the middle of these arrays between the element corresponding to cm[n_fields -
1] and the element corresponding to cb[0].
• For MPLEX fields, the first element corresponds to count_val and the second to period. The re‐
mainder are uninitialised.
• For PHASE fields, the first element corresponds to shift. The remainder are uninitialised.
• For POLYNOM fields, these arrays correspond with the co-efficients ca. Only the first poly_ord +
1 elements are initialised.
• For RAW fields, the first element corresponds to spf. The remainder are uninitialised.
• For RECIP fields, the first element corresponds to cdividend. The remainder are uninitialised.
• For WINDOW fields, the first element corresponds to threshold. The remainder are uninitialised.
The scalar parameters are NULL if a literal parameter was used, or else a field code specifying the
scalar parameters.
If an element of scalar specifies a CARRAY field, the corresponding scalar_ind will indicate the element
of the CARRAY used. For CONST fields, scalar_ind will be -1.
BITandSBITMembers
A gd_entry_t describing a BIT or SBIT entry, will also provide:
typedef struct {
...
const char *in_fields[1]; /* input field code */
int bitnum; /* first bit */
int numbits; /* bit length */
...
} gd_entry_t;
The in_fields member is an array of length one containing the input field code.
The bitnum member indicates the number of the first bit (counted from zero) extracted from the input. If
this value was specified as a scalar field code, this will be the numerical value of that field, and
scalar[0] will contain the field code itself, otherwise scalar[0] will be NULL.
The numbits member indicates the number of bits which are extracted from the input. If this value was
specified as a scalar field code, this will be the numerical value of that field, and scalar[1] will con‐
tain the field code itself, otherwise scalar[1] will be NULL.
CARRAYMembers
A gd_entry_t describing a CARRAY entry, will also provide:
typedef struct {
...
gd_type_t const_type; /* data type in format specification */
size_t array_len; /* length of array data */
...
} gd_entry_t;
The const_type member indicates the data type of the constant value stored in the format file metadata.
See gd_getdata(3) for a list of valid values that a variable of type gd_type_t may take.
The array_len member gives the number of elements in the array.
CONSTMembers
A gd_entry_t describing a CONST entry, will also provide:
typedef struct {
...
gd_type_t const_type; /* data type in format specification */
...
} gd_entry_t;
The const_type member indicates the data type of the constant value stored in the format file metadata.
See gd_getdata(3) for a list of valid values that a variable of type gd_type_t may take.
DIVIDE,INDIR,MULTIPLY,andSINDIRMembers
A gd_entry_t describing a DIVIDE, INDIR, MULTIPLY, or SINDIR entry, will also provide:
typedef struct {
...
const char *in_fields[2]; /* input field codes */
...
} gd_entry_t;
The in_fields member is an array of length two containing the input field codes.
INDEXMembers
A gd_entry_t describing an INDEX entry, which is used only for the implicit INDEX field, provides no ad‐
ditional data.
LINCOMMembers
A gd_entry_t describing a LINCOM entry, will also provide:
typedef struct {
...
int n_fields; /* # of inputs */
const char *in_fields[GD_MAX_LINCOM]; /* input fields(s) */
double complex cm[GD_MAX_LINCOM]; /* scale factor(s) */
double m[GD_MAX_LINCOM]; /* scale factor(s) */
double complex cb[GD_MAX_LINCOM]; /* offset terms(s) */
double b[GD_MAX_LINCOM]; /* offset terms(s) */
...
} gd_entry_t;
The n_fields member indicates the number of input fields. It will be between one and GD_MAX_LINCOM in‐
clusive. GD_MAX_LINCOM is defined in getdata.h as the maximum number of input fields permitted by a
LINCOM.
The in_fields member is an array of length GD_MAX_LINCOM containing the input field code(s). Only the
first n_fields elements of this array are initialised. The remaining elements contain uninitialised da‐
ta.
The cm and cb members are arrays of the scale factor(s) and offset term(s) for the LINCOM. Only the
first n_fields elements of these array contain meaningful data. If any of these values were specified as
a scalar field code, this will be the numerical value of that field. The field code corresponding to
cm[i] will be stored in scalar[i] and the field code associated with cb[i] will be stored in scalar[i +
GD_MAX_LINCOM]. Otherwise the corresponding scalar member will be NULL. See NOTES below on changes to
the declaration of cm and cb when using the C89 GetData API.
The elements of m and b are the real parts of the corresponding elements of cm and cb.
LINTERPMembers
A gd_entry_t describing a LINTERP entry, will also provide:
typedef struct {
...
const char *table /* linterp table filename */
const char *in_fields[1]; /* input field code */
...
} gd_entry_t;
The table member is the pathname to the look up table on disk. This the path as it appars in the format
specification. It may be a path relative to the fragment directory. For an canonicalised, absolute ver‐
sion of this path, see gd_linterp_tablename(3).
The in_fields member is an array of length one containing the input field code.
MPLEXMembers
A gd_entry_t describing a MPLEX entry, will also provide:
typedef struct {
...
const char *in_fields[2]; /* input field codes */
int count_val; /* value of the multiplex index */
int period; /* samples between successive
indices */
...
} gd_entry_t;
The in_fields member contains the field codes of the input field (element 0) and the multiplex index
field (element 1).
The count_val member is the value of the multiplex index field when the output field is stored in the in‐
put field.
The period member is the number of samples between successive occurrances of count_val in the index vec‐
tor, or zero, if this is not known or constant. This is only used to determine how far to look back for
a starting value for the output field; see gd_mplex_lookback(3).
PHASEMembers
A gd_entry_t describing a PHASE entry, will also provide:
typedef struct {
...
const char *in_fields[1]; /* input field code */
gd_int64_t shift; /* phase shift */
...
} gd_entry_t;
The in_fields member is an array of length one containing the input field code.
The shift member indicates the shift in samples. The gd_int64_t type is a 64-bit signed integer type. A
positive value indicates a shift forward in time (towards larger frame numbers). If this value was spec‐
ified as a scalar field code, this will be the numerical value of that field, and scalar[0] will contain
the field code itself, otherwise scalar[0] will be NULL.
POLYNOMMembers
A gd_entry_t describing a POLYNOM entry, will also provide:
typedef struct {
...
int poly_ord; /* polynomial order */
const char *in_fields[1]; /* input field(s) */
double complex ca[GD_MAX_POLY_ORD + 1]; /* co-efficients(s) */
double a[GD_MAX_POLY_ORD + 1]; /* co-efficients(s) */
...
} gd_entry_t;
The poly_ord member indicates the order of the polynomial. It will be between one and GD_MAX_POLY_ORD
inclusive. GD_MAX_POLY_ORD is defined in getdata.h as the maximum order of polynomial permitted by a
POLYNOM.
The in_fields member is an array of length one containing the input field code.
The ca members are arrays of the co-efficient(s) for the POLYNOM. Only the first poly_ord + 1 elements
of this array contains meaningful data. If any of these values were specified as a scalar field code,
this will be the numerical value of that field. The field code corresponding to ca[i] will be stored in
scalar[i]. Otherwise the corresponding scalar member will be NULL. See NOTES below on changes to the
declaration of ca when using the C89 GetData API.
The elements of a are the real parts of the corresponding elements of ca.
RAWMembers
A gd_entry_t describing a RAW entry, will also provide:
typedef struct {
...
unsigned int spf; /* samples per frame on disk */
gd_type_t data_type; /* data type on disk */
...
} gd_entry_t;
The spf member contains the samples per frame of the binary data on disk. If this value was specified as
a scalar field code, this will be the numerical value of that field, and scalar[0] will contain the field
code itself, otherwise scalar[0] will be NULL.
The data_type member indicates the data type of the binary data on disk. See gd_getdata(3) for a list of
valid values that a variable of type gd_type_t may take.
RECIPMembers
A gd_entry_t describing a RECIP entry, will also provide:
typedef struct {
...
const char *in_fields[1]; /* input field code */
double complex cdividend; /* scalar dividend */
double dividend; /* scalar dividend */
...
} gd_entry_t;
The in_fields member is an array of length one containing the input field code.
The cdividend member provides the constant dividend of the computed division. If this value was speci‐
fied as a scalar field code, this will be the numerical value of that field, and scalar[0] will contain
the field code itself, otherwise scalar[0] will be NULL. The dividend member contains the real part of
cdividend.
STRINGMembers
A gd_entry_t describing a STRING entry provides no additional data.
WINDOWMembers
A gd_entry_t describing a WINDOW entry, will also provide:
typedef struct {
...
const char *in_fields[2]; /* input field codes */
gd_windop_t windop; /* comparison operator */
gd_triplet_t threshold; /* the value compared against */
...
} gd_entry_t;
The in_fields member contains the field codes of the input field (element 0) and the check field (element
1).
The windop member equals one of the following symbols, indicating the particular comparison performed on
the check field:
GD_WINDOP_EQ
data are extracted when the check field equals threshold;
GD_WINDOP_GE
data are extracted when the check field is greater than or equal to threshold;
GD_WINDOP_GT
data are extracted when the check field is strictly greater than threshold;
GD_WINDOP_LE
data are extracted when the check field is less than or equal to threshold;
GD_WINDOP_LT
data are extracted when the check field is strictly less than threshold;
GD_WINDOP_NE
data are extracted when the check field is not equal to threshold;
GD_WINDOP_SET
data are extracted when at least one bit in threshold is also set in the check field;
GD_WINDOP_CLR
data are extracted when at least one bit in threshold is not set in the check field.
The threshold is the value against which the check field is compared. The gd_triplet_t type is defined
as:
typedef union {
gd_int64_t i;
gd_uint64_t u;
double r;
} gd_triplet_t;
The particular element of the union to use depends on the value of windop:
• For GD_WINDOP_EQ and GD_WINDOP_NE, the signed integer element, threshold.i, is set;
• For GD_WINDOP_SET and GD_WINDOP_CLR, the unsigned integer element, threshold.u, is set;
• For all other values of windop, the floating point element, threshold.r, is set.
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