hdf5：勾选创建组

Question

如果群组尚不存在，我想自动创建一个群组。但是，我没有成功检查该组是否存在。

失败尝试 1

#include <iostream>
#include <string>
#include "H5Cpp.h"

int main(void)
{
  H5::H5File file("test.h5",H5F_ACC_TRUNC);

  std::string group_name = "/test";

  H5::Group group = file.createGroup(group_name.c_str());

  if ( !file.attrExists(group_name.c_str()) )
    H5::Group group = file.createGroup(group_name.c_str());

  return 0;
}

编译

$ h5c++ -o test test.cpp

失败，因为 file.attrExists(name) 总是 returns false。作为参考，错误发生在createGroup:

... 

#006: H5L.c line 1733 in H5L_link_cb(): name already exists
  major: Symbol table
  minor: Object already exists

失败尝试 2

#include <iostream>
#include <string>
#include "H5Cpp.h"

int main(void)
{
  H5::H5File file("test.h5",H5F_ACC_TRUNC);

  std::string group_name = "/test";

  try         { H5::Group group = file.openGroup  (group_name.c_str()); }
  catch (...) { H5::Group group = file.createGroup(group_name.c_str()); }

  return 0;
}

编译

$ h5c++ -o test test.cpp

不知怎么的，catch不成功，openGroup失败时报错：

...

#005: H5Gloc.c line 385 in H5G_loc_find_cb(): object 'test' doesn't exist
  major: Symbol table
  minor: Object not found

Answer 1

您的 尝试 1 失败，因为 H5::Group 不是属性，所以

if ( !file.attrExists(group_name.c_str()) )

并不像您想象的那样。 AFAIK，没有比尝试打开组更简单的方法来检查组是否存在。这导致我们

你的 尝试 2 实际上 没有失败 ，但有效（你为什么不这么认为？）不幸的是，HDF5 吐出很多错误 blurb（除了抛出异常），但你可以抑制它

int main(void)
{
  H5::Exception::dontPrint();                             // suppress error messages
  H5::H5File file("test.h5",H5F_ACC_TRUNC);    
  std::string group_name = "/test";
  try         {
    H5::Group group = file.openGroup  (group_name.c_str());
    std::cerr<<" TEST: opened group\n";                   // for debugging
  } catch (...) {
    std::cerr<<" TEST: caught something\n";               // for debugging
    H5::Group group = file.createGroup(group_name.c_str());
    std::cerr<<" TEST: created group\n";                  // for debugging
  }
  H5::Group group = file.openGroup  (group_name.c_str()); // for debugging
  std::cerr<<" TEST: opened group\n";                     // for debugging
}

生成

TEST: caught something
TEST: created group
TEST: opened group

hdf5：勾选创建组

hdf5: Check to create group

c++

hdf5

失败尝试 1

失败尝试 2