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WFDB 10.3

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Changes in version 10.3.17 (20 August 2005)

This version is the first to support reading variable-layout records (multi-segment records in which the number, arrangement, gains, and baselines of the signals may vary from one segment to the next; see section Multi-Segment Records).

Rounding errors in the WFDB library’s mstimstr function have been reduced. Previous versions did not always round appropriately when the sampling frequency was much less than 1 Hz.

The maximum length for a record name (WFDB_MAXRNL, defined in ‘wfdb.h’) has been increased from 11 to 20.

A new constant, WFDB_INVALID_SAMPLE, is now defined in ‘wfdb.h’. It is used to identify padding inserted to fill in for missing data. When writing in any format that uses fewer than 16 bits per sample, putvec maps WFDB_INVALID_SAMPLE to the lowest (most negative) value expressible in that format; when reading a signal file in such a format, getframe performs the inverse mapping, so that missing data can be identified regardless of the data format.

A side effect of this change is that (for example) any samples that had the most negative value (for example, -2048 in a format 212 signal file) are now flagged as invalid. To treat such samples as invalid is reasonable, however, since these occur only when the input level falls below the working range of the analog-to-digital converter.

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Changes in version 10.3.16 (13 June 2005)

Benjamin Moody has added an interface between the WFDB library and libcurl as an alternative to the existing libwww interface, and has updated ‘configure’ and ‘conf/*.def’ to search for and use libcurl if it is available. The primary advantages of libcurl over libwww are that libcurl is smaller and faster, it supports access to password-protected files, and it is actively maintained. Both libraries are freely available on all popular platforms.

Isaac Henry has updated configure to support building a native MS-Windows version of the WFDB library using either Cygwin gcc or MinGW gcc.

A number of minor changes, mostly involving conditional use of ‘malloc.h’, ‘stdlib.h’, and ‘string.h’, were made to eliminate warnings from gcc 4.x.

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Changes in version 10.3.15 (31 January 2005)

Rules for generating the binary tarball for MS-Windows have been fixed so that the Cygwin DLLs are now included with correct permissions.

Installation of shared libraries under GNU/Linux requires an extra step if SELinux is enabled (as under Fedora Core 2 and later); this has been incorporated into ‘conf/linux-slib.def’.

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Changes in version 10.3.14 (29 December 2004)

Guido Muesch reported that getspf() did not always return correct results if the frame frequency does not have an exact representation as a double precision floating point number. This problem has now been corrected.

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Changes in version 10.3.13 (5 May 2004)

Using an indirect WFDB path (i.e., setting the WFDB environment variable to a value such as ‘@FILE’, where ‘FILE’ contains the desired path) was broken in WFDB library versions 10.3.9 through 10.3.12; it now works again, thanks to a patch contributed by Fred Geheb.

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Changes in version 10.3.12 (9 March 2004)

Okko Willeboordse pointed out an incompatibility between the native MS-Windows API and the ANSI/ISO C library function mkdir, which is used by the WFDB library. This does not present a problem when compiling the WFDB library using the supported Cygwin/gcc compiler under MS-Windows, nor does any related problem occur on any other platform. It should now be a little easier to compile the WFDB library using unsupported compilers, thanks to a new MKDIR macro that hides the incompatibility (see ‘lib/wfdblib.h0’).

Piotr Wlodarek initiated a discussion about memory leaks in the WFDB library, citing as an example the ’trivial example program in C’ from this Guide, which does not free memory it allocates in isigopen() when reading the signal specifications. This problem can be avoided by invoking wfdbquit() in the example program, just before exiting. Further discussion of this point has been added to this Guide following the presentation of the ’trivial example’, and in the description of wfdbquit.

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Changes in version 10.3.11 (17 October 2003)

In ‘signal.c’, several bugs have been identified and fixed. Thanks to Piotr Wlodarek, who found a buffer overrun in isigopen. Also, isgsettime sometimes performed incorrect seeks on multifrequency records that had been opened in high-resolution mode; this has been fixed, together with a related bug that caused the value returned by strtim("e") to be calculated incorrectly in some such cases.

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Changes in version 10.3.10 (3 August 2003)

In version 10.3.9, the functions setannstr, setanndesc, and setecgstr did not contain necessary checks to avoid invoking strcmp with a NULL argument. These checks have been added in version 10.3.10. Thanks to Thomas Heldt for reporting this problem.

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Changes in version 10.3.9 (16 July 2003)

The WFDB library functions setwfdb, setannstr, setanndesc, and setecgstr now copy their input string arguments, so that it is no longer necessary for WFDB applications to keep these strings valid. If you have created applications that rely on being able to modify these strings, it will be necessary to invoke the corresponding functions again before such changes will take effect within the WFDB library.

Previous versions of the WFDB library function putinfo did not flush their output until either a new header file was created (via setheader or newheader) or the process exited. This has now been corrected, and putinfo output is now flushed before putinfo returns. Thanks to Jonas Carlson for reporting this problem.

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Changes in version 10.3.8 (12 July 2003)

The WFDB library function setbasetime() now properly accepts arguments specifying midnight (e.g., ‘0:0:0’), which previous versions rejected, and the function setheader() records such times correctly in the ‘.hea’ files it creates.

(WFDB library version 10.3.7 was identical to 10.3.6.)

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Changes in version 10.3.6 (7 April 2003)

The fix applied in isigclose() in 10.3.5 was incomplete but is now (really!) fixed. Applications that use sample() should call wfdbquit() to be certain that sample’s buffer is freed before exiting.

Some long-standing problems in the code (in ‘lib/wfdbio.c’) that handles http range requests for NETFILES-enabled versions of the library have been partially addressed. The underlying issue is that http servers do not always return the range of bytes requested; when this happens, it is not difficult to determine that there is a problem, but it is tricky to figure out what to do about it. Based on experiments with several different http servers, the strategy for handling such problems within the WFDB NETFILES code has been improved substantially, but there may be further room for improvement.

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Changes in version 10.3.5 (31 March 2003)

Fixed a bug in WFDB library function isigclose() (in ‘lib/signal.c’) that had caused sample()’s buffer to be freed inappropriately when switching segments in a multi-segment record. Thanks to Dave Schaffer for the bug report and for a test case that illustrated the bug.

(WFDB library versions 10.3.3 and 10.3.4 were identical to 10.3.2.)

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Changes in version 10.3.2 (25 February 2003)

Fixed a WFDB library bug that caused annotation sorting to fail if a new header file had been written. Thanks to Winton Baker for reporting this problem and for providing an example that illustrated the bug.

(WFDB library version 10.3.1 was identical to 10.3.0.)

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Changes in version 10.3.0 (26 November 2002)

Fixed bugs in ‘lib/signal.c’ that caused improper accounting of signal group numbers when reading from two or more records at the same time (as in ‘nst’), a bug that caused a segfault in ‘nst’, and a bug that referenced uninitialized memory in newheader if nsig = 0.

The WFDB Software Package has been ported to Mac OS X (Darwin), version 10.2 (the port should also work under 10.1 but this has not been tested and will not be supported).

It is now possible to generate a shared WFDB library (DLL) under MS-Windows using Cygwin/gcc.

Added functions sample and sample_valid to the WFDB library (in ‘lib/signal.c’). sample(s, t) returns the sample at time (sample number) t from signal s, handling all necessary buffering internally and allowing the caller to treat the signal file as a virtual array of randomly accessible samples. sample_valid can be invoked to check if the most recent value returned by sample was valid (e.g., to see if the end of the input was reached). For an example of the use of these functions, see ‘app/wqrs.c’.

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George B. Moody (george@mit.edu)