h5exists: 10-100x speedup, scalar variable

Author: scivision

+stdlib/+hdf5nc/h5exists.m

@@ -1,13 +1,27 @@
-function exists = h5exists(file, vars)
+function exists = h5exists(file, variable)
 
 arguments
   file (1,1) string {mustBeFile}
-  vars string
+  variable string {mustBeScalarOrEmpty}
 end
 
-i = startsWith(vars, "/");
-vars(i) = extractAfter(vars(i), 1);
-% NOT contains because we want exact string match
-exists = ismember(vars, stdlib.hdf5nc.h5variables(file));
+exists = false;
+
+if(strlength(variable) == 0)
+  return
+end
+
+if ~startsWith(variable, "/")
+  variable = "/" + variable;
+end
+
+try
+  h5info(file, variable);
+  exists = true;
+catch e
+  if e.identifier ~= "MATLAB:imagesci:h5info:unableToFind"
+    rethrow(e)
+  end
+end
 
 end

+stdlib/h5exists.m

@@ -1,19 +1,19 @@
-function exists = h5exists(file, vars)
+function exists = h5exists(file, variable)
 %% H5EXISTS(file, vars)
 % check if object(s) exists in HDF5 file
 %
 %%% Inputs
 % * file: data filename
-% * varname: path(s) of variable in file
+% * variable: path of variable in file
 %
 %%% Outputs
-% * exists: boolean (scalar or vector)
+% * exists: boolean
 
 arguments
     file (1,1) string {mustBeFile}
-    vars string
+    variable string {mustBeScalarOrEmpty}
 end
 
-exists = stdlib.hdf5nc.h5exists(file, vars);
+exists = stdlib.hdf5nc.h5exists(file, variable);
 
 end

test/TestHDF5.m

@@ -97,23 +97,14 @@ function test_exists(tc)
 import matlab.unittest.constraints.IsScalar
 basic = tc.TestData.basic;
 
-tc.verifyEmpty(stdlib.h5exists(basic, string.empty))
-
 e = stdlib.h5exists(basic, "");
 
 tc.verifyThat(e, IsScalar)
 tc.verifyFalse(e)
 
-vars = {'A0', 'A1', 'A2', 'A3', 'A4', '/A0'};
-
-e = stdlib.h5exists(basic, vars);
-tc.verifyTrue(isvector(e))
-tc.verifyTrue(all(e))
+tc.verifyTrue(stdlib.h5exists(basic, "/A0"));
+tc.verifyTrue(stdlib.h5exists(basic, "A0"));
 
-% vector
-e = stdlib.h5exists(basic, ["/A1", "oops"]);
-tc.verifyTrue(isrow(e))
-tc.verifyEqual(e, [true, false])
 end