gd_entry(3)

NAME
gd_entry — retrieve a Dirfile field's metadata

SYNOPSIS
#include <getdata.h>

int gd_entry(DIRFILE *dirfile, const char *field_code, gd_entry_t *entry);

DESCRIPTION
The function queries a dirfile(5) database specified by and retrieves the metadata associated with the field specified by If contains a valid representation suffix, the suffix will be ignored.

The argument must point to a valid DIRFILE object previously created by a call to

The entry will be stored in the gd_entry_t structure indicated by the argument, which must be allocated by the caller. Members available in this structure depend on the field type of the field queried. See below for a complete description of this data type.

Strings members in filled by this function (including, depending on field type: elements of the and arrays, the LINTERP member) will by dynamically allocated by Only strings provided by the gd_entry_t for the particular field type described will be allocated. By default, these strings are allocated using but this can be changed by specifying an alternate memory manager via The caller is responsible for deallocating these strings. The function is provided as a convenience to do this.

If the entry's metadata contains scalar field codes which cannot be dereferenced, the associated numerical field parameter will be initialised to zero. In this case, the GD_EN_CALC flag in the returned entry object will NOT be set.

The returned structure, including strings and their pointers may be freely modified by the caller.

RETURN VALUE
Upon successful completion, returns zero and writes the field metadata in the supplied gd_entry_t buffer. On error, the supplied gd_entry_t buffer is not modified. In this case, returns a negative-valued error code. Possible error codes are: The library was unable to allocate memory. The field specified by was not found in the database. The supplied dirfile was invalid.

The error code is also stored in the DIRFILE object and may be retrieved after this function returns by calling A descriptive error string for the error may be obtained by calling

THE ENTRY TYPE
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 member is the field code of the entry (i.e. its string name). If the call to is successful, this will be the field name specified as part of the argument.

The 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 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 may be obtained by calling 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 member is a bitwise or'd collection of the following entry flags: This bit is set only when the non-literal scalar parameter field codes specified in the 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 would fail on the specified with the error GD_E_BAD_SCALAR), then the unresolved numerical 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. 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. This bit is set only when the field has been hidden by the /HIDDEN directive (see

Remaining fields in the gd_entry_t structure depend on the value of Callers are advised to check 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 declared for the appropriate field type will have unspecified results.

  Scalar Parameter Members
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 and the second to 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 elements of these two sets are initialised. Notably, this means for < GD_MAX_LINCOM, there will be uninitialised elements in the middle of these arrays between the element corresponding to cm[n_fields - 1] and the element corresponding to

•   For MPLEX fields, the first element corresponds to and the second to The remainder are uninitialised.

•   For PHASE fields, the first element corresponds to The remainder are uninitialised.

•   For POLYNOM fields, these arrays correspond with the co-efficients Only the first + 1 elements are initialised.

•   For RAW fields, the first element corresponds to The remainder are uninitialised.

•   For RECIP fields, the first element corresponds to The remainder are uninitialised.

•   For WINDOW fields, the first element corresponds to 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 specifies a CARRAY field, the corresponding will indicate the element of the CARRAY used. For CONST fields, will be -1.

  BIT and SBIT Members
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 member is an array of length one containing the input field code.

The 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 will contain the field code itself, otherwise will be NULL.

The 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 will contain the field code itself, otherwise will be NULL.

  CARRAY Members
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 member indicates the data type of the constant value stored in the format file metadata. See for a list of valid values that a variable of type gd_type_t may take.

The member gives the number of elements in the array.

  CONST Members
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 member indicates the data type of the constant value stored in the format file metadata. See for a list of valid values that a variable of type gd_type_t may take.

  DIVIDE, INDIR, MULTIPLY, and SINDIR Members
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 member is an array of length two containing the input field codes.

  INDEX Members
A gd_entry_t describing an INDEX entry, which is used only for the implicit INDEX field, provides no additional data.

  LINCOM Members
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 member indicates the number of input fields. It will be between one and GD_MAX_LINCOM inclusive. GD_MAX_LINCOM is defined in getdata.h as the maximum number of input fields permitted by a LINCOM.

The member is an array of length GD_MAX_LINCOM containing the input field code(s). Only the first elements of this array are initialised. The remaining elements contain uninitialised data.

The and members are arrays of the scale factor(s) and offset term(s) for the LINCOM. Only the first 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 member will be NULL. See NOTES below on changes to the declaration of and when using the C89 GetData API.

The elements of and are the real parts of the corresponding elements of and

  LINTERP Members
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 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 version of this path, see

The member is an array of length one containing the input field code.

  MPLEX Members
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 member contains the field codes of the input field (element 0) and the multiplex index field (element 1).

The member is the value of the multiplex index field when the output field is stored in the input field.

The member is the number of samples between successive occurrances of in the index vector, 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

  PHASE Members
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 member is an array of length one containing the input field code.

The 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 specified as a scalar field code, this will be the numerical value of that field, and will contain the field code itself, otherwise will be NULL.

  POLYNOM Members
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 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 member is an array of length one containing the input field code.

The members are arrays of the co-efficient(s) for the POLYNOM. Only the first + 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 member will be NULL. See NOTES below on changes to the declaration of when using the C89 GetData API.

The elements of are the real parts of the corresponding elements of

  RAW Members
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 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 will contain the field code itself, otherwise will be NULL.

The member indicates the data type of the binary data on disk. See for a list of valid values that a variable of type gd_type_t may take.

  RECIP Members
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 member is an array of length one containing the input field code.

The member provides the constant dividend of the computed division. If this value was specified as a scalar field code, this will be the numerical value of that field, and will contain the field code itself, otherwise will be NULL. The member contains the real part of

  STRING Members
A gd_entry_t describing a STRING entry provides no additional data.

  WINDOW Members
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 member contains the field codes of the input field (element 0) and the check field (element 1).

The member equals one of the following symbols, indicating the particular comparison performed on the check field: data are extracted when the check field equals data are extracted when the check field is greater than or equal to data are extracted when the check field is strictly greater than data are extracted when the check field is less than or equal to data are extracted when the check field is strictly less than data are extracted when the check field is not equal to data are extracted when at least one bit in is also set in the check field; data are extracted when at least one bit in is not set in the check field.

The 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

•   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.

NOTES
When using the C89 GetData API (by defining GD_C89_API before including getdata.h), the data types and names of several of the entry parameters are different. The following table lists the correspondences between members in the C99 and C89 APIs.

C99 API | C89 API
int | bitnum | int | u.bit.bitnum
int | numbits | int | u.bit.numbits
int | n_fields | int | u.lincom.n_fields
double complex | cm[] | double | u.lincom.cm[][2]
double | m[] | double | u.lincom.m[]
double complex | cb[] | double | u.lincom.cb[][2]
double | b[] | double | u.lincom.b[]
const char* | table | const char* | u.linterp.table
int | count_val | int | u.mplex.count_val
int | period | int | u.mplex.period
gd_int64_t | shift | gd_int64_t | u.phase.shift
int | poly_ord | int | u.polynom.poly_ord
double complex | ca[] | double | u.polynom.ca[][2]
double | a[] | double | u.polynom.a[]
unsigned int | spf | unsigned int | u.raw.spf
gd_type_t | data_type | gd_type_t | u.raw.data_type
double complex | cdividend | double | u.recip.cdividend[2]
double | dividend | double | u.recip.dividend
gd_type_t | const_type | gd_type_t | u.scalar.const_type
size_t | array_len | size_t | u.scalar.array_len
gd_windop_t | windop | gd_windop_t | u.window.windop
gd_triplet_t | threshold | gd_triplet_t | u.window.threshold

In the case of complex valued data in the C89 API, the first element of the two-element array is the real part of the complex number, and the second element is the imaginary part.

HISTORY
The function appeared in GetData-0.3.0.

In GetData-0.7.0, this function was renamed to

In GetData-0.10.0, the error return from these functions changed from -1 to a negative-valued error code.

  Changes to the gd_entry_t structure
Field-type specific members have been added to the structure as support for those field types have been introduced to the library:

•   BIT, LINCOM, LINTERP, MULTIPLY, PHASE, and RAW were supported in GetData-0.3.0 (Dirfile Standards Version 5).

•   CONST and STRING entries were introduced in GetData-0.4.0 (Dirfile Standards Version 6); this is also the first version that treats INDEX as a normal field. In earlier versions, trying to retrieve the metadata for the INDEX field would fail.

•   POLYNOM and SBIT entries were introduced in GetData-0.6.0 (Dirfile Standards Version 7).

•   CARRAY, DIVIDE, and RECIP entries were introduced in GetData-0.7.0 (Dirfile Standards Version 8).

•   MPLEX and WINDOW entries were introduced in GetData-0.8.0 (Dirfile Standards Version 9).

•   INDIR, SARRAY, and SINDIR entries were introduced in GetData-0.10.0 (Dirfile Standards Version 10).

The member appeared in GetData-0.6.0. This release also introduced the complex-valued scalar members (cm, &c.)

The member appeared in GetData-0.7.0. This was also the first release with a working ANSI C (C89) conforming alternate definition.

Before Getdata-0.8.4, the member for MPLEX data was named

Before GetData-0.9.0, the member is missing. In it's place was:

    int comp_scal; /* Scalar parameters are complex-valued */

which was non-zero to indicate complex-valued parameters, which is now indicated by the GD_EN_COMPSCAL flag.

SEE ALSO
dirfile(5),