gd_alter_spec, gd_malter_spec — modify a field in a Dirfile
int gd_alter_spec(DIRFILE *dirfile, const char *line, int recode);
int gd_malter_spec(DIRFILE *dirfile, const char *line, const char *parent, int recode);
The gd_alter_spec() function modifies the field described by the field specification line in line to the dirfile specified by dirfile. The gd_malter_spec() function behaves similarly, but modifies the metafield under the field indicated by the field code parent. Field specification lines are described in detail in dirfile-format(5).
The name of the field to be modified, which must already exist, will be obtained from the field specification line. When adding a metafield, line should only contain a field specification, and not a /META directive.
If the modified field is of type RAW and the recode argument is non-zero, the binary file associated with the field will be converted for changes in data type and samples-per-frame. In this case, the field’s I/O pointer will be reset to the beginning-of-frame. If recode is zero, no binary file conversion will take place.
If the modified field is of type LINTERP and the recode argument is non-zero, the look-up table file will be moved if line specifies a different path, overwriting an existing file with the new pathname, if present. If the field specified by field_code is of type other than RAW or LINTERP, the recode argument is ignored.
Passing these functions a directive line instead of a field specification line will result in a syntax error. These functions never call the registered parser callback function, even if line contains a syntax error.
On success, gd_alter_spec() and gd_malter_spec() return zero. On error, it returns a negative-valued error code. Possible error codes are:
The specified dirfile was opened read-only.
The library was unable to allocate memory.
The field specified in line was not found, or the parent field code was not found.
The supplied dirfile was invalid.
A syntax error was encountered in line.
An I/O error occurred while translating the binary file associated with a modified RAW field, or an I/O error occurred while attempting to rename a LINTERP table file.
The supplied line was longer than the parser was able to deal with. Line lengths are limited by the storage size of size_t.
The metadata of the fragment was protected from change. Or, a request to translate the binary file associated with a RAW field was attempted, but the data of the fragment was protected.
The encoding scheme of the indicated format specification fragment is not known to the library. As a result, the library was unable to translate the binary file be associated with a modified RAW field.
The encoding scheme of the indicated format specification fragment does not support translating the empty binary file associated with a modified RAW field.
The error code is also stored in the DIRFILE object and may be retrieved after this function returns by calling gd_error(3). A descriptive error string for the error may be obtained by calling gd_error_string(3).
The functions dirfile_alter_spec() and dirfile_malter_spec() appeared in GetData-0.5.0.
In GetData-0.7.0, these functions were renamed to gd_alter_spec() and gd_malter_spec.()
In GetData-0.10.0, the error return from these functions changed from -1 to a negative-valued error code.