daqreadCached

This version of daqread is modified to improve retrieval speed, particularly for large files.

This version of daqread (daqreadCached.m) is modified in two ways to improve retrieval speed, particularly for large files.

1) Instead of building a file index each time daqread is called, which can be very time-consuming for large files, this version caches the index (or 'chart') between calls in a persistent variable. Subsequent calls will use the cached chart if the .daq filename and the number of samples acquired is the same as for the previous call (if these change, a new chart will be built).

2) The cached chart now includes one additional table indicating the startsample for each data block in the file. This is then used for much faster random access (rather than sequential access) to retrieve data samples,which is particularly helpful for retrieving data late in the stored file. *** The robustness of this method has not been tested for multichannel or triggered acquisition ***