Metrologic Optimus R, Programming Manual

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Chapter 3 Terminal Specific Function Library 191
delete_top
Purpose To delete a specified number of bytes from the top (beginning-of-file position)
of a DAT file.
Syntax int delete_top (int fd, int count);
int fd; /* file handle of the target DAT file */
int count; /* number of bytes to be deleted */
Example delete_top (fd, 80);
Description This routine deletes the number of bytes (
count
) from a DAT file (
fd
).
Removal of data starts at the beginning-of-file position of the file, and the
file pointer position is adjusted accordingly.
For example, if initially the file pointer points to the tenth character, after
deleting eight characters from the file, the new file pointer will points to
the 2nd character of the file.
This routine will resize the file size automatically.
Return If successful, it returns the number of bytes actually removed from the file.
On error, it returns -1.
An error code is set to the global variable fErrorCode to indicate the error
condition encountered. Below are possible error codes and their interpretation.
Error Code Interpretation
2 File specified by fd does not exist.
4 File specified by
fd
is not a DAT file.
7 Invalid file handle.
8 File not opened.
9 The value of
count
is negative.
See Also delete_topln
delete_topln
Purpose To delete a line (null-terminated string) from the top (beginning-of-file
position) of a DAT file.
Syntax
int delete_topln (int fd);
int fd; /* file handle of the target DAT file */
Example delete_topln (fd);
Description This routine deletes a null-terminated string specified from a DAT file (
fd
).
Characters are removed from the file until a null character (\0) or
end-of-file is encountered. The null character is also removed from the
file.