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annopen | Opening input and output annotation files. | |
isigopen | Opening input signal files. | |
osigopen | Opening output signal files. | |
osigfopen | Opening output signal files by name. | |
wfdbinit | annopen and isigopen in one function.
|
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int annopen(char *record, WFDB_Anninfo *aiarray, unsigned int nann) |
Return:
Success
Failure: unable to open input annotation file
Failure: unable to open output annotation file
Failure: illegal stat
(in aiarray) specified for annotation file
This function opens input and output annotation files for a selected
record. If record begins with ‘+’, previously opened
annotation files are left open, and the record name is taken to be the
remainder of record after discarding the ‘+’. Otherwise,
annopen
closes any previously opened annotation files, and takes
all of record as the record name. aiarray is a pointer to
an array of WFDB_Anninfo
structures
(see section Annotator Information Structures),
one for each annotator to be opened. nann is the number of
WFDB_Anninfo
structures in aiarray. The caller must
fill in the WFDB_Anninfo
structures to specify the names of the
annotators, and to indicate which annotators are to be read, and which
are to be written. Input and output annotators may be listed in any
order in aiarray. Annotator numbers (for both input and
output annotators) are assigned in the order in which the annotators
appear in aiarray. For example, this code fragment
… char *record = "100s"; WFDB_Anninfo a[3]; a[0].name = "a"; a[0].stat = WFDB_READ; a[1].name = "b"; a[1].stat = WFDB_WRITE; a[2].name = "c"; a[2].stat = WFDB_READ; if (annopen(record, a, 3) < 0) … |
attempts to open three annotation files for record ‘100s’.
Annotator ‘a’ becomes input annotator 0, ‘b’ becomes output
annotator 0, and ‘c’ becomes input annotator 1. Thus
getann(1, &annot)
(see section getann
)
will read an annotation from annotator ‘c’, and
putann(0, &annot)
will write an annotation for annotator ‘b’.
Input annotation files will be found if they are located in any of the
directories specified by WFDB
(see section The Database Path and Other Environment Variables); output annotators
are created in the current directory (but note that, under Unix at
least, it is possible to specify annotator names such as ‘/here’ or
‘zzz/there’ or even ‘../somewhere/else’; see section Annotation Files, for details of how file names are constructed from annotator and
record names). Several of the example programs in chapter 6 illustrate
the use of annopen
; for example, see section Example 1: An Annotation Filter.
As a special case, if nann is 0, aiarray can be NULL
.
This can be useful to force open annotation files to be closed without
closing open signal files.
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int isigopen(char *record, WFDB_Siginfo *siarray, int nsig) |
Return:
Success: the returned value is the number of input signals (i.e., the number of valid entries in siarray)
Failure: no input signals available
Failure: unable to read header file (probably incorrect record name)
Failure: incorrect header file format
Failure: internal limits exceeded (all signal files closed)
This function opens input signal files for a selected record. If
record begins with ‘+’, previously opened input signal files
are left open, and the record name is taken to be the remainder of
record after discarding the ‘+’. Otherwise, isigopen
closes any previously opened input signal files, and takes all of
record as the record name. If the record name is ‘-’,
isigopen
reads the standard input rather than a ‘hea’
file. Siarray is a pointer to an array of WFDB_Siginfo
structures
(see section Signal Information Structures),
one for each signal to be opened.
As a special case, if nsig is 0, siarray can be NULL
.
In this case, isigopen
closes any open input signals, then
returns the number of signals in record without opening them. Use
this feature to determine the amount of storage needed for
signal-related variables, as in the example below, or to force open
input signal files to be closed without closing open annotation or
output signal files. This action also sets internal WFDB library
variables that record the base time and date, the length of the record,
and the sampling and counter frequencies, so that time conversion
functions such as strtim
that depend on these quantities will
work properly.
If nsig
is greater than 0, isigopen
normally returns the
number of input signals it actually opened, which may be less than
nsig but is never greater than nsig. The caller must
allocate storage for the WFDB_Siginfo
structures; isigopen
will fill them in with information about the signals. Signal
numbers are assigned in the order in which signals are specified in the
‘hea’ file for the record; on return from isigopen
,
information for signal i will be found in siarray[i]. For
example, we can read the gain
attributes of each signal in record
‘100s’ like this:
#include <stdio.h> #include <wfdb/wfdb.h> main() { int i, nsig; WFDB_Siginfo *siarray; nsig = isigopen("100s", NULL, 0); if (nsig < 1) exit(1); siarray = (WFDB_Siginfo *)malloc(nsig * sizeof(WFDB_Siginfo)); nsig = isigopen("100s", siarray, nsig); for (i = 0; i < nsig; i++) printf("signal %d gain = %g\n", i, siarray[i].gain); exit(0); } |
(See http://physionet.org/physiotools/wfdb/examples/pgain.c for a copy of this program.)
This program, unlike the example in the previous chapter, does not
assume that the number of signals is known. The first invocation of
isigopen
determines this number (and the program quits if there
are no signals). Next, the program allocates the array for the signal
information, and then it opens the signals using the second
invocation of isigopen
, passing in the pointer siarray
and the
number of signals determined from the first call (nsig
).
An error message is produced if isigopen
is unable to open
any of the signals listed in the header file. It is not
considered an error if only some of the signals can be opened, however.
A signal will not be opened if its signal file is unreadable, if an
input buffer cannot be allocated for it, or if opening all of the
signals in its group would exceed the limits defined by nsig.
(Note, however, that most records have only one signal group; as a
consequence, isigopen
fails if nsig is less than the
total number of signals in such cases.) If necessary, the caller can
inspect the file names and signal descriptions in siarray to
determine which signals were opened;
see section Signal Information Structures.
Several of the example programs in chapter 6
illustrate the use of isigopen
; for example, see section Example 5: Reading Signal Specifications.
If the overall set of open signals exceeds internal limits (for example, the
total number of samples per frame is greater than INT_MAX
),
isigopen
returns -3 and closes all previously-opened input
signals.
If nsig is less than 0, isigopen
fills in up to
-nsig
members of siarray, based on information from the header file
for record, but no signals are actually opened. The value
returned in this case is the number of signals named in the ‘hea’ file.
Note, however, that there is no guarantee that all (or indeed any) of the
signals named in the ‘hea’ file are available to be opened.
The features described in this paragraph were first introduced in
version 4.4 of the WFDB library.
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int osigopen(char *record, WFDB_Siginfo *siarray, unsigned int nsig) |
Return:
Success: the returned value is the number of output signals; this number should match nsig
Failure: unable to read header file
Failure: incorrect header file format
Failure: unable to open output signal(s)
This function opens output signal files. Use it only if signals are to
be written using putvec
. The signal specifications,
including the file names, are read from the header file for a
specified record. Unmodified MIT or AHA database ‘hea’ files
cannot be used, since osigopen
would attempt to overwrite the
(write-protected) signal files named within. If record begins
with ‘+’, previously opened output signal files are left open, and
the record name is taken to be the remainder of record after
discarding the ‘+’. Otherwise, osigopen
closes any
previously opened output signal files, and takes all of record as
the record name. If the record name is ‘-’, osigopen
reads
the standard input rather than a ‘hea’ file. siarray is a
pointer to an uninitialized array of WFDB_Siginfo
structures;
siarray must contain at least nsig members. The caller must
allocate storage for the WFDB_Siginfo
structures. On return,
osigopen
will have filled in the WFDB_Siginfo
structures with
the signal specifications.
No more than nsig (additional) output signals will be opened by
osigopen
, even if the header file contains specifications for
more than nsig signals. For example, this code fragment
… WFDB_Siginfo s[2]; int i, nsig; nsig = osigopen("8l", s, 2); for (i = 0; i < nsig; i++) printf("signal %d will be written into `%s'\n", i, s[i].fname); … |
creates 2 output signals named ‘data0’ and ‘data1’
(see section Piped and Local Records). See section Example 6: A Differentiator, and see section Example 7: A General-Purpose FIR Filter,
for illustrations of the use of osigopen
.
As a special case, if nsig is 0, siarray can be NULL
.
This can be useful to force open output signal files to be closed
without closing open annotation or input signal files.
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int osigfopen(WFDB_Siginfo *siarray, unsigned int nsig) |
Return:
Success: the returned value is the number of output signals; this number should match nsig
Failure: error in signal specification (fname
or desc
too
long, illegal fmt
or bsize
, or incorrect signal group
assignment)
Failure: unable to open output signal(s)
This function opens output signals as does osigopen
, but the
signal specifications, including the signal file names, are supplied by
the caller to osigfopen
, rather than read from a header
file as in osigopen
. Any previously open output signals are
closed by osigfopen
. siarray is a pointer to an array of
WFDB_Siginfo
structures
(see section Signal Information Structures),
one for each signal to be opened. nsig is the number of
WFDB_Siginfo
structures in siarray.
Before invoking osigfopen
, the caller must fill in the fields of
the WFDB_Siginfo
structures in siarray (see section Data Types;
the initval
, nsamp
, and cksum
fields may be left
uninitialized, however). To make a multiplexed signal file, specify the
same fname
and group
for each signal to be included
(see section Multiplexed Signal Files). For ordinary (non-multiplexed)
signal files, specify a unique fname
and group
for each
signal. See section Example 8: Creating a New Database Record, for an illustration of the use of
osigfopen
.
As a special case, if nsig is 0, siarray can be NULL
.
This can be useful to force open output signal files to be closed
without closing open annotation or input signal files.
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int wfdbinit(char *record, WFDB_Anninfo *aiarray, unsigned int nann, WFDB_Siginfo *siarray, unsigned int nsig) |
Return:
Success: the returned value is the number of input signals (i.e., the number of valid entries in siarray)
Annotation files opened successfully, input signals unavailable (not an error for programs that don’t need them; no error message is printed if nsig is 0)
Failure: unable to read header file (probably incorrect record name)
Failure: incorrect header file format
Failure: unable to open input annotation file
Failure: unable to open output annotation file
Failure: illegal stat
(in aiarray) specified for annotation file
(see section Annotator Information Structures)
This function opens database files other than output signal files for a selected record. The code
n = wfdbinit(record, a, na, s, ns); |
is exactly equivalent to
n = annopen(record, a, na); if (n == 0) n = isigopen(record, s, ns); |
Avoid using wfdbinit
and setifreq
in the same program.
See section Example 9: A Signal Averager, for an illustration of the use of wfdbinit
.
See section osigopen
, and see section osigfopen
,
for methods of opening output signal files.
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