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MT(3) FreeBSD Library Functions Manual MT(3)
NAME
mt_start_element, mt_end_element, mt_char_handler, mt_status_tree_sbuf,
mt_status_tree_print, mt_status_entry_free, mt_status_free,
mt_entry_sbuf, mt_param_parent_print, mt_param_entry_print,
mt_protect_print, mt_param_list, mt_density_name, mt_density_bp,
mt_density_num, mt_get_xml_str, mt_get_status - Magnetic Tape library
LIBRARY
library "libmt"
SYNOPSIS
#include <sys/sbuf.h>
#include <bsdxml.h>
#include <mtlib.h>
void
mt_start_element(void *user_data, const char *name, const char **attr);
void
mt_end_element(void *user_data, const char *name);
void
mt_char_handler(void *user_data, const XML_Char *str, int len);
void
mt_status_tree_sbuf(struct sbuf *sb, struct mt_status_entry *entry,
int indent,
void (*sbuf_func)(struct sbuf *sb, struct mt_status_entry
*entry, void *arg), void *arg);
void
mt_status_tree_print(struct mt_status_entry *entry, int indent,
void (*print_func)(struct mt_status_entry *entry, void *arg),
void *arg);
struct mt_status_entry *
mt_entry_find(struct mt_status_entry *entry, char *name);
struct mt_status_entry *
mt_status_entry_find(struct mt_status_data *status_data, char *name);
void
mt_status_entry_free(struct mt_status_entry *entry));
void
mt_status_free(struct mt_status_data *status_data);
void
mt_entry_sbuf(struct sbuf *sb, struct mt_status_entry *entry, char *fmt);
void
mt_param_parent_sbuf(struct sbuf *sb, struct mt_status_entry *entry,
struct mt_print_params *print_params);
void
mt_param_parent_print(struct mt_status_entry *entry,
struct mt_print_params *print_params);
int
mt_protect_print(struct mt_status_data *status_data, int verbose);
int
mt_param_list(struct mt_status_data *status_data, char *param_name,
int quiet);
const char *
mt_density_name(int density_num);
int
mt_density_bp(int density_num, int bpi);
int
mt_density_num(const char *density_name);
int
mt_get_status(char *xml_str, struct mt_status_data *status_data);
DESCRIPTION
The MT library consists of a number of functions designed to aid in
interacting with the sa(4) driver. The sa(4) driver returns some status
data as XML-formatted strings, and the primary purpose of this library is
to make it easier for the software developer to parse those strings and
extract the status values.
The mt_start_element(), mt_end_element(), and mt_char_handler() functions
are designed to work with the libbsdxml(3) library, which is an XML
parsing library. The user data for the XML parser should be set with
XML_SetUserData() to a zeroed struct mt_status_data with the entries list
initialized. The element handlers for the XML parser should be set to
mt_start_element() and mt_end_element() with XML_SetElementHandler().
The character data handler should be set to mt_char_handler() with the
XML_SetCharacterDataHandler() function. The error member of the
status_data structure will be set to 0 if parsing is successful, and non-
zero if parsing failed. In the event of a failure, the error_str member
will contain an error message describing the failure. These functions
will build a tree of tape driver status data that can be searched and
printed using the other functions in this library.
mt_status_tree_sbuf() takes the root node of a tree of sa(4) driver
status information, and displays it in an sbuf(9). The sb argument is
the destination sbuf. The entry argument is the root of the tree. The
indent argument is the number of characters to indent the output. Each
recursive call to mt_status_tree_sbuf() will have the indent level
incremented by 2. The sbuf_func argument is for a user-supplied
alternate printing function. If it is non-NULL, it will be called
instead of the default output printing code. The arg argument is an
argument for the sbuf_func function.
The mt_status_tree_print() function is the same as the
mt_status_tree_sbuf() function, except that the tree is printed to
standard out instead of to a sbuf.
The mt_entry_find() function returns the first entry in the tree starting
at entry that matches name. The supplied node name can be a single level
name like "foo", or it can specify multiple node names that must be
matched, for instance "foo.bar.baz". In the case of a single level name,
below it instead of just an mt_status_entry structure.
The mt_status_entry_free() function frees the tree of status data
underneath entry.
The mt_status_free() function frees the tree of status data underneath
status_data.
The mt_entry_sbuf() function prints entry to the supplied sbuf sb,
optionally using the printf(3) format fmt. If fmt is NULL, then
mt_entry_sbuf() will render integer types in base 10 without special
formatting and all other types as they were rendered in the XML.
mt_param_parent_sbuf() prints the parents of the given entry to the
supplied sbuf sb subject to the print parameters print_params. The
result will be formatted with a period between each level, like
"foo.bar.baz".
mt_param_parent_print() is like mt_param_parent_sbuf() except that it
prints the results to standard output instead of an sbuf.
mt_param_entry_sbuf() prints the entry to the given sbuf sb. The
argument arg is a pointer to struct mt_print_params, which allows the
caller to control the printing output. This function is intended to be
supplied as an argument to mt_status_tree_sbuf().
mt_param_entry_print() is like mt_param_entry_sbuf() except that it
prints to standard output instead of an sbuf. It is intended to be used
as an argument to mt_status_tree_print().
mt_protect_print() prints tape drive protection information from the
supplied status_data beginning at the node name defined as the root node
for protection data. If the verbose argument is non-zero, protection
entry descriptions will be printed. If it is zero, protection entry
descriptions will not be printed.
mt_param_list() prints tape driver parameters information from the
supplied status_data. If the param_name is non-NULL, only the named
parameter will be printed. If quiet is non-zero, parameter descriptions
will be omitted in the output.
mt_density_name() Returns a text identifier for the supplied numeric
density_num. The density_num should currently be a value between 0 and
255 inclusive, since that is the valid range for SCSI density code
values. See below for notes on the return values.
mt_density_bp() Returns the bits per inch or bits per mm values for a
given density entry specified by the density_num. If the bpi argument is
non-zero, the bits per inch value is returned. Otherwise, the bits per
mm value is returned.
mt_density_num() returns a numeric value for a text density description.
It does a case-insensitive comparison of density names in the density
table to the supplied density name.
mt_get_xml_str() gets the current XML status / parameter string from the
sa(4) driver instance referenced by the open file descriptor mtfd. The
mtio(4) ioctl(2) to be used is supplied as the cmd argument. Currently
the mt_get_xml_str() function will work with the MTIOCEXTGET and
mt_entry_find() returns the first matching entry, or NULL if it fails to
find a match.
mt_status_entry_find() returns the first matching entry, or NULL if it
fails to find a match.
mt_protect_print() Returns 0 for success, and non-zero for failure.
mt_protect_print() can only fail if it cannot find protection information
in the supplied status data.
mt_param_list() Returns 0 for success and non-zero for failure.
mt_param_list() can only fail if it cannot find parameter information in
the supplied status data.
mt_density_name() returns a text description of a numeric density. The
special density value 0 is decoded as "default". The special density
value 0x7f is decoded as "same". If the density is not known,
mt_density_name() will return "UNKNOWN".
mt_density_bp() returns the bits per inch value for the given density (if
the bpi field is non-zero), the bits per mm value otherwise, or 0 if the
supplied density_num is not in the density table or the table entry does
not include bpi / bpmm values.
mt_density_num() returns a numeric density value between 0 and 255 for
the supplied density name. It returns 0 if the density name is not
recognized.
mt_get_xml_str() returns 0 for success, and -1 for failure.
SEE ALSO
mt(1), mtio(4), sa(4)
HISTORY
The MT library first appeared in FreeBSD 10.1.
AUTHORS
Ken Merry <ken@FreeBSD.org>
BUGS
The library interface is not complete, and may change in the future.
Application authors should not rely on the library interface to be
consistent in the immediate future.
FreeBSD 14.0-RELEASE-p6 February 13, 2015 FreeBSD 14.0-RELEASE-p6