Forgot org files

src/trexio_hdf5.org

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+#+Title: HDF5 back end for the TREX Input/Ouput library (TREXIO)
+
+* File prefixes                                                     :noxport:
+
+  #+NAME:header
+  #+begin_src c 
+/* This file was generated from the trexio.org org-mode file.
+   To generate it, open trexio.org in Emacs and execute
+   M-x org-babel-tangle
+*/
+
+
+
+  #+end_src
+
+  #+begin_src c :tangle trexio_hdf5.h :noweb yes
+<<header>>
+#ifndef _TREXIO_HDF5_H
+#define _TREXIO_HDF5_H
+
+#include "trexio.h"
+#include "trexio_s.h"
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+#include <sys/stat.h>
+
+#include "hdf5.h"
+#include "hdf5_hl.h" // needed for high-level APIs like H5LT, requires additional linking in Makefile
+  #+end_src
+  
+  #+begin_src c :tangle trexio_hdf5.c :noweb yes
+<<header>>
+#include "trexio_hdf5.h"
+  #+end_src
+
+
+* HDF5 Back end
+
+** HDF5 definitions
+
+#+begin_src c :tangle trexio_hdf5.c
+  #define NUCLEUS_GROUP_NAME  "nucleus"
+  #define NUCLEUS_NUM_NAME    "nucleus_num"
+  #define NUCLEUS_CHARGE_NAME "nucleus_charge"
+  #define NUCLEUS_COORD_NAME  "nucleus_coord"
+  
+#+end_src
+
+** HDF5 structures
+
+  #+begin_src c :tangle trexio_hdf5.h
+
+typedef struct slab_s {
+  uint64_t a;
+  uint64_t b;
+  uint64_t c;
+  uint64_t d;
+} slab_t;
+
+typedef struct dset_s {
+  hid_t dset_id;
+  hid_t dspace_id;
+  hid_t dtype_id;
+  uint64_t* dims;
+  uint32_t rank;
+  const char* dset_name;
+} dset_t;
+
+typedef struct h5nucleus_s {
+  uint64_t   num;
+  double    *coord;
+  double    *charge;
+  dset_t*    h5_coord;
+  dset_t*    h5_charge;
+} h5nucleus_t;
+
+typedef struct h5electron_s {
+  uint64_t  alpha_num;
+  uint64_t  beta_num;
+} h5electron_t;
+
+typedef struct trexio_hdf5_s {
+  trexio_t     parent ;
+  hid_t      file_id;
+  hid_t      nucleus_group;
+  hid_t      electron_group;
+  //... other groups' id
+  const char* file_name;
+} trexio_hdf5_t;
+
+  #+end_src
+
+** HDF5 basic functions
+
+
+  #+begin_src c :tangle trexio_hdf5.h
+trexio_exit_code trexio_hdf5_init(trexio_t* file);
+  #+end_src
+
+
+  #+begin_src c :tangle trexio_hdf5.c
+
+/* 
+ * Currently H5LTread_dataset_ is used instead of this function 
+ * but keep it for later if we decide to get rid of the H5LT API 
+ */
+dset_t* trexio_hdf5_read_dset_low(const trexio_hdf5_t* file, const char *dset_name, void *buf) {
+
+  assert (file != NULL);
+  assert (dset_name != NULL);
+  assert (buf != NULL);
+  /*
+   * Low-level implementation. Involves dealing with all HDF5 handles and dimensions
+   */
+  dset_t* dset = (dset_t*) malloc(sizeof(dset_t));
+  assert (dset != NULL);
+
+  dset->dset_id = H5Dopen(file->nucleus_group, 
+                          dset_name, 
+                          H5P_DEFAULT);
+  assert (dset->dset_id > 0);
+  /*
+   * Get dataspace, datatype and dimensions
+   * dspace and dtype handles created below have to be closed when not used
+   */    
+  dset->dspace_id = H5Dget_space(dset->dset_id);
+  assert (dset->dspace_id > 0);
+  
+  dset->dtype_id = H5Dget_type(dset->dset_id);
+  assert (dset->dtype_id > 0);
+  
+  /* Check dimensions. Usefull, but then additional parameters 
+   * ranks and dims[] have to be passed to the function
+  int rrank;
+  const int rank = 1;
+  hsize_t dims[1] = {0};
+  rrank = H5Sget_simple_extent_dims(nucleus->h5_charge->dspace_id, 
+                                    dims, NULL);
+  assert (rrank == rank);
+  for (int i=0; i<rank; i++){
+    assert (dims[i] > 0);
+  }
+  */
+  herr_t status;
+  status = H5Dread(dset->dset_id, dset->dtype_id,
+               H5S_ALL, H5S_ALL, H5P_DEFAULT,
+	       buf);
+  assert (status >= 0);
+
+  return dset;
+
+}
+
+trexio_exit_code trexio_hdf5_init(trexio_t* file) {
+
+  trexio_hdf5_t* f = (trexio_hdf5_t*) file;
+
+  /* If file doesn't exist, create it */
+  int f_ishere = 0;
+  struct stat st;
+  
+  if (stat(file->file_name, &st) == 0) {
+    printf("%s \n","HDF5 file already exists");
+   // RDWR OR RDONLY ???
+    f->file_id = H5Fopen(file->file_name, H5F_ACC_RDWR, H5P_DEFAULT);
+    f_ishere = 1;
+  } else {
+    f->file_id = H5Fcreate(file->file_name, H5F_ACC_TRUNC, H5P_DEFAULT, H5P_DEFAULT);
+    f_ishere = 0;
+  }  
+
+  /* Create groups in the hdf5 file */
+  if (f_ishere == 0){
+    f->nucleus_group = H5Gcreate(f->file_id, NUCLEUS_GROUP_NAME, H5P_DEFAULT, H5P_DEFAULT, H5P_DEFAULT);
+    //f->electron_group = H5Gcreate(f->file_id, ELECTRON_GROUP_NAME, H5P_DEFAULT, H5P_DEFAULT, H5P_DEFAULT);
+  } else { 
+    f->nucleus_group = H5Gopen(f->file_id, NUCLEUS_GROUP_NAME, H5P_DEFAULT);
+    //f->electron_group = H5Gopen(f->file_id, ELECTRON_GROUP_NAME, H5P_DEFAULT);   
+  }
+  assert (f->nucleus_group > 0L);
+  //assert (f->electron_group > 0L);
+
+  return TREXIO_SUCCESS;
+}
+
+  #+end_src
+
+    
+  #+begin_src c :tangle trexio_hdf5.h
+trexio_exit_code trexio_hdf5_finalize(trexio_t* file);
+  #+end_src
+
+  #+begin_src c :tangle trexio_hdf5.c
+trexio_exit_code trexio_hdf5_finalize(trexio_t* file) {
+
+  trexio_hdf5_t* f = (trexio_hdf5_t*) file;
+
+  H5Gclose(f->nucleus_group);
+  f->nucleus_group = 0;
+
+/*
+  H5Gclose(f->electron_group);
+  f->electron_group = 0; 
+*/
+
+  H5Fclose(f->file_id);
+  f->file_id = 0;
+
+  return TREXIO_SUCCESS;
+}
+  #+end_src
+
+  
+  
+** Structs for sparse data structures
+    #+begin_src c :tangle trexio_hdf5.h
+typedef struct one_index_s {
+  double value;
+  int64_t i;
+} one_index_t;
+
+typedef struct two_index_s {
+  double value;
+  int64_t i;
+  int64_t j;
+} two_index_t;
+
+typedef struct three_index_s {
+  double value;
+  int64_t i;
+  int64_t j;
+  int64_t k;
+} three_index_t;
+
+typedef struct four_index_s {
+  double value;
+  int64_t i;
+  int64_t j;
+  int64_t k;
+  int64_t l;
+} four_index_t;
+
+    #+end_src
+  
+** Read/write the nucleus struct
+
+   #+begin_src c :tangle trexio_hdf5.c
+h5nucleus_t* trexio_hdf5_read_nucleus(const trexio_hdf5_t* file) {
+  
+  /* Allocate the data structure */
+  h5nucleus_t* nucleus = (h5nucleus_t*) malloc(sizeof(h5nucleus_t));
+  assert (nucleus != NULL);
+
+  nucleus->num    = 0;
+  nucleus->coord  = NULL;
+  nucleus->charge = NULL;
+  nucleus->h5_coord  = NULL;
+  nucleus->h5_charge = NULL;
+
+  /* Check that the file was opened/created correctly, return */ 
+  if (file->file_id < 0) return nucleus;
+
+  /* Quit if the dimensioning attribute is missing in the file */
+  if (H5Aexists(file->nucleus_group, NUCLEUS_NUM_NAME) == 0) return nucleus;
+
+  herr_t status;  
+  /* Read the nucleus_num attribute of nucleus group */
+  hid_t num_id;
+  num_id = H5Aopen(file->nucleus_group, NUCLEUS_NUM_NAME, H5P_DEFAULT);
+  assert (num_id > 0);
+
+  status = H5Aread(num_id, H5T_NATIVE_ULLONG, &(nucleus->num));
+  assert (status >= 0);
+
+  /* Allocate and read nucleus_charge array */
+  nucleus->charge = (double*) calloc(nucleus->num, sizeof(double));
+  assert (nucleus->charge != NULL);
+
+  /* High-level H5LT API. No need to deal with dataspaces and datatypes */
+  status = H5LTread_dataset_double(file->nucleus_group, 
+                                NUCLEUS_CHARGE_NAME, 
+				nucleus->charge);
+
+  /* Allocate and read nucleus_coord array */
+  nucleus->coord = (double*) calloc(3 * nucleus->num, sizeof(double));
+  assert (nucleus->coord != NULL);
+
+  /* High-level H5LT API. No need to deal with dataspaces and datatypes */
+  status = H5LTread_dataset_double(file->nucleus_group, 
+                                    NUCLEUS_COORD_NAME, 
+				    nucleus->coord);
+  assert (status >= 0);
+
+  /* Low-level read. Do not forget to close the associated IDs (dset,dtype,dspace) 
+   *  when not used anymore, see below. Note how this function is similar to H5LTread_dataset_double
+   */
+  /*
+  nucleus->h5_coord = trexio_hdf5_read_dset_low(file, NUCLEUS_COORD_NAME, 
+  		  		nucleus->coord); 
+
+  H5Sclose(nucleus->h5_coord->dspace_id);
+  H5Tclose(nucleus->h5_coord->dtype_id);
+  H5Dclose(nucleus->h5_coord->dset_id);
+  */
+
+  H5Aclose(num_id);
+
+  return nucleus;
+}
+
+
+trexio_exit_code trexio_hdf5_write_nucleus(const trexio_hdf5_t* file, h5nucleus_t* nucleus) {
+
+  assert (file != NULL);
+  assert (nucleus != NULL);
+
+  herr_t status;
+  hid_t dspace, dtype; 
+  hid_t attr_id;
+    
+  dtype = H5Tcopy(H5T_NATIVE_ULLONG);
+  /* Write the dimensioning variables */
+  if (H5Aexists(file->nucleus_group, NUCLEUS_NUM_NAME) == 0) {
+    dspace = H5Screate(H5S_SCALAR);
+    attr_id = H5Acreate(file->nucleus_group, NUCLEUS_NUM_NAME, dtype, dspace,
+                     H5P_DEFAULT, H5P_DEFAULT);
+    assert (attr_id > 0);
+
+    /* High-level routine does not work for some reason
+     * status = H5LTset_attribute_ulong (file->nucleus_group, "nucleus", NUCLEUS_NUM_NAME, 
+     *                                  &(nucleus->num), 1);
+     */
+  } else {
+    attr_id = H5Aopen(file->nucleus_group, NUCLEUS_NUM_NAME, H5P_DEFAULT);
+    assert (attr_id > 0);
+  }
+
+  status = H5Awrite(attr_id, dtype, &(nucleus->num));
+  assert (status >= 0); 
+
+  H5Aclose(attr_id);
+  
+  /* Write arrays */
+  hid_t dset_id;
+  int charge_rank = 1;
+  const hsize_t charge_dims[1] = {nucleus->num};
+
+  if ( H5LTfind_dataset(file->nucleus_group, NUCLEUS_CHARGE_NAME) != 1) { 
+    
+    status = H5LTmake_dataset_double (file->nucleus_group, NUCLEUS_CHARGE_NAME, 
+                                    charge_rank, charge_dims, nucleus->charge);
+    assert (status >= 0);
+
+  } else {   
+
+    dset_id = H5Dopen(file->nucleus_group, NUCLEUS_CHARGE_NAME, H5P_DEFAULT);
+    assert (dset_id > 0);
+    
+    dspace = H5Dget_space(dset_id);
+    assert (dspace > 0);
+
+    dtype = H5Dget_type(dset_id);
+    assert (dtype > 0);
+
+    
+    int rrank;
+    hsize_t dims[1] = {0};
+    rrank = H5Sget_simple_extent_dims(dspace,
+                                    dims, NULL);
+    assert (rrank == charge_rank);
+    // disabling asserts like this allows to overwrite _num variable
+    for (int i=0; i<rrank; i++){
+      assert (dims[i] == charge_dims[i]);
+    }
+
+    status = H5Dwrite(dset_id, H5T_NATIVE_DOUBLE, H5S_ALL, H5S_ALL, H5P_DEFAULT, nucleus->charge);
+    assert (status >= 0);
+
+    H5Sclose(dspace);
+    H5Tclose(dtype);
+    H5Dclose(dset_id);
+
+  }
+
+  int coord_rank = 2;
+  const hsize_t coord_dims[2] = {nucleus->num, 3};
+  if ( H5LTfind_dataset(file->nucleus_group, NUCLEUS_COORD_NAME) != 1) { 
+    status = H5LTmake_dataset_double (file->nucleus_group, NUCLEUS_COORD_NAME, 
+                                    coord_rank, coord_dims, nucleus->coord);
+    assert (status >= 0);
+
+  } else {   
+
+    dset_id = H5Dopen(file->nucleus_group, NUCLEUS_COORD_NAME, H5P_DEFAULT);
+    assert (dset_id > 0);
+    
+    dspace = H5Dget_space(dset_id);
+    assert (dspace > 0);
+
+    dtype = H5Dget_type(dset_id);
+    assert (dtype > 0);
+
+    
+    int rrank;
+    hsize_t dims[2] = {0, 0};
+    rrank = H5Sget_simple_extent_dims(dspace,
+                                    dims, NULL);
+    assert (rrank == coord_rank);
+    for (int i=0; i<rrank; i++){
+      assert (dims[i] == coord_dims[i]);
+    }
+
+    status = H5Dwrite(dset_id, H5T_NATIVE_DOUBLE, H5S_ALL, H5S_ALL, H5P_DEFAULT, nucleus->coord);
+    assert (status >= 0);
+
+    H5Sclose(dspace);
+    H5Tclose(dtype);
+    H5Dclose(dset_id);
+
+  }
+
+  return TREXIO_SUCCESS;
+}
+
+  #+end_src
+
+** Free memory
+
+    Memory is allocated when reading. The followig function frees memory.
+    
+   #+begin_src c :tangle trexio_hdf5.c
+trexio_exit_code trexio_hdf5_free_nucleus(h5nucleus_t* nucleus) {
+  
+  if (nucleus == NULL) return TREXIO_FAILURE;
+  
+  if (nucleus->coord != NULL) free (nucleus->coord);
+  nucleus->coord = NULL;
+  
+  if (nucleus->charge != NULL) free (nucleus->charge);
+  nucleus->charge = NULL;
+  
+  if (nucleus->h5_coord != NULL) free (nucleus->h5_coord);
+  nucleus->h5_coord = NULL;
+  
+  if (nucleus->h5_charge != NULL) free (nucleus->h5_charge);
+  nucleus->h5_charge = NULL;
+
+  free (nucleus);
+
+  return TREXIO_SUCCESS;
+}
+   #+end_src
+
+** Read/Write the num attribute
+
+   #+begin_src c :tangle trexio_hdf5.h
+trexio_exit_code trexio_hdf5_read_nucleus_num(const trexio_t* file, uint64_t* num);
+trexio_exit_code trexio_hdf5_write_nucleus_num(const trexio_t* file, const uint64_t num);
+  #+end_src
+
+   #+begin_src c :tangle trexio_hdf5.c
+trexio_exit_code trexio_hdf5_read_nucleus_num(const trexio_t* file, uint64_t* num) {
+
+  assert (file != NULL);
+  assert (num  != NULL);
+
+  h5nucleus_t* nucleus = trexio_hdf5_read_nucleus((trexio_hdf5_t*) file);
+  
+  if (nucleus == NULL) {
+    return TREXIO_FAILURE;
+  }
+
+  /**/ *num = nucleus->num;
+
+  trexio_hdf5_free_nucleus(nucleus);
+  return TREXIO_SUCCESS;
+}
+
+ 
+trexio_exit_code trexio_hdf5_write_nucleus_num(const trexio_t* file, const uint64_t num) {
+
+  assert (file != NULL);
+  assert (num > 0L);
+  
+  h5nucleus_t* nucleus = trexio_hdf5_read_nucleus((trexio_hdf5_t*) file);
+
+  assert (nucleus != NULL);
+  
+  if (nucleus->num != num) {
+
+    if (nucleus->num != 0) {
+	printf("%ld -> %ld %s \n", num, nucleus->num, 
+	       "This variable alreasy exists. Overwriting it is not supported");
+        trexio_hdf5_free_nucleus(nucleus);
+    	return TREXIO_FAILURE;
+    }
+
+    nucleus->num = num;
+
+    if (nucleus->charge != NULL) free(nucleus->charge);
+    nucleus->charge = NULL;
+
+    nucleus->charge = (double*) calloc(num, sizeof(double));
+    assert (nucleus->charge != NULL);
+    
+    if (nucleus->coord  != NULL) free(nucleus->coord );
+    nucleus->coord = NULL;
+
+    nucleus->coord = (double*) calloc(3*num, sizeof(double));
+    assert (nucleus->coord != NULL);
+
+  } else {
+    nucleus->num = num;
+  }
+  
+  trexio_exit_code rc = trexio_hdf5_write_nucleus((trexio_hdf5_t*) file, nucleus);
+  assert (rc == TREXIO_SUCCESS);
+
+  trexio_hdf5_free_nucleus(nucleus);
+  
+  return TREXIO_SUCCESS;
+}
+    #+end_src
+
+
+** Read/Write the coord attribute
+
+    The ~coord~ array is assumed allocated with the appropriate size.
+    
+   #+begin_src c :tangle trexio_hdf5.h
+trexio_exit_code trexio_hdf5_read_nucleus_coord(const trexio_t* file, double* coord);
+trexio_exit_code trexio_hdf5_write_nucleus_coord(const trexio_t* file, const double* coord);
+  #+end_src
+
+   #+begin_src c :tangle trexio_hdf5.c
+trexio_exit_code trexio_hdf5_read_nucleus_coord(const trexio_t* file, double* coord) {
+
+  assert (file != NULL);
+  assert (coord != NULL);
+
+  h5nucleus_t* nucleus = trexio_hdf5_read_nucleus((trexio_hdf5_t*) file);
+
+  if (nucleus == NULL) return TREXIO_FAILURE;
+  assert (nucleus->coord != NULL);
+  
+  for (size_t i=0 ; i<3*nucleus->num ; i++) {
+    coord[i] = nucleus->coord[i];
+  }
+
+  trexio_hdf5_free_nucleus(nucleus);
+  return TREXIO_SUCCESS;
+}
+
+ 
+trexio_exit_code trexio_hdf5_write_nucleus_coord(const trexio_t* file, const double* coord) {
+
+  assert (file != NULL);
+  assert (coord != NULL);
+  
+  h5nucleus_t* nucleus = trexio_hdf5_read_nucleus((trexio_hdf5_t*) file);
+
+  if (nucleus == NULL) return TREXIO_FAILURE;
+  assert (nucleus->coord != NULL); 
+ 
+  for (size_t i=0 ; i<3*nucleus->num ; i++) {
+    nucleus->coord[i] = coord[i];
+  }
+  
+  trexio_exit_code rc = trexio_hdf5_write_nucleus((trexio_hdf5_t*) file, nucleus);
+  assert (rc == TREXIO_SUCCESS);
+
+  trexio_hdf5_free_nucleus(nucleus);
+  
+  return TREXIO_SUCCESS;
+}
+
+    #+end_src
+** TODO Read/Write the charge attribute
+
+* File suffixes                                                     :noxport:
+
+  #+begin_src c :tangle trexio_hdf5.h
+#endif
+  #+end_src

src/trexio_text.org

@@ -0,0 +1,834 @@
+#+Title: TEXT back end of the TREX Input/Ouput library (TREXIO)
+
+* File prefixes                                                     :noxport:
+
+  #+NAME:header
+  #+begin_src c 
+/* This file was generated from the trexio.org org-mode file.
+   To generate it, open trexio.org in Emacs and execute
+   M-x org-babel-tangle
+*/
+
+
+
+  #+end_src
+
+  #+begin_src c :tangle trexio_text.h :noweb yes
+<<header>>
+#ifndef _TREXIO_TEXT_H
+#define _TREXIO_TEXT_H
+
+#include "trexio.h"
+#include "trexio_s.h"
+#include <errno.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <sys/stat.h>
+
+  #+end_src
+  
+  #+begin_src c :tangle trexio_text.c :noweb yes
+<<header>>
+#include "trexio_text.h"
+  #+end_src
+
+* TEXT Back end
+
+  The "file" produced by the text back end is a directory with one
+  file per group.
+  
+  When the file is open, it is locked by the current process. No other
+  process can read/write the same file. This guarantees that the
+  representation in memory is consistent with the file and avoid
+  re-reading the file before writing.
+  To lock the file, we lock the =.lock= file which is present in the
+  directory. 
+  
+  The file is written when closed, or when the flush function is called.
+  
+*** Structs for blocks
+    #+begin_src c :tangle trexio_text.h
+typedef struct nucleus_s {
+  FILE*    file;
+  uint64_t dim_coord;
+  uint64_t dim_charge;
+  double*  coord;
+  double*  charge;
+  uint64_t num;
+  int      to_flush;
+} nucleus_t;
+
+typedef struct electron_s {
+  FILE*    file;
+  uint64_t  alpha_num;
+  uint64_t  beta_num;
+  int       to_flush;
+} electron_t;
+
+typedef struct rdm_s {
+  FILE*    file;
+  uint64_t dim_one_e;
+  double*  one_e;
+  char*    two_e_file_name;
+  int      to_flush;
+} rdm_t;
+    #+end_src
+
+    
+*** TO DO
+    - to_flush = 1 in write
+    - to_flush = 0 when flushed
+    - name 
+
+*** Structs for the text back end
+    
+    #+begin_src c :tangle trexio_text.h
+typedef struct trexio_text_s {
+  trexio_t   parent ;
+  int        lock_file;
+
+  nucleus_t*  nucleus;
+  electron_t* electron;
+  rdm_t*      rdm;
+} trexio_text_t;
+
+    #+end_src
+
+
+    #+begin_src c :tangle trexio_text.h
+trexio_exit_code trexio_text_init(trexio_t* file);
+    #+end_src
+  
+    #+begin_src c :tangle trexio_text.c
+trexio_exit_code trexio_text_init(trexio_t* file) {
+  if (file == NULL) return TREXIO_INVALID_ARG_1;
+
+  trexio_text_t* f = (trexio_text_t*) file;
+
+  /* If directory doesn't exist, create it in write mode */
+  struct stat st;
+  
+  if (stat(file->file_name, &st) == 0 && S_ISDIR(st.st_mode)) {
+    /* Do nothing */
+  } else {
+    if (file->mode == 'r') return TREXIO_READONLY;
+    
+    if (mkdir(file->file_name, 0777) != 0) {
+      return TREXIO_FAILURE;
+    }
+  }  
+
+  /* Create the lock file in the directory */
+  const char* lock_file_name = "/.lock";
+  char* file_name = (char*)
+    calloc( strlen(file->file_name) + strlen(lock_file_name) + 1,
+            sizeof(char));
+  assert (file_name != NULL);
+  strcpy (file_name, file->file_name);
+  strcat (file_name, lock_file_name);
+
+  f->lock_file = open(file_name,O_WRONLY|O_CREAT|O_TRUNC, 0644);
+  assert (f->lock_file > 0);
+  free(file_name);
+
+  /* Lock the directory for the current process */
+  struct flock fl;
+  
+  fl.l_type   = F_WRLCK;
+  fl.l_whence = SEEK_SET;
+  fl.l_start  = 0;       
+  fl.l_len    = 0;       
+  fl.l_pid    = getpid();
+  
+  int rc = fcntl(f->lock_file, F_SETLKW, &fl);
+  if (rc == -1) return TREXIO_FAILURE;
+
+  trexio_text_t* f_child = (trexio_text_t*) file;
+
+  f_child->nucleus = NULL;
+  f_child->electron= NULL;
+  f_child->rdm     = NULL;
+  
+  return TREXIO_SUCCESS;
+}
+
+    #+end_src
+
+    
+    #+begin_src c :tangle trexio_text.h
+trexio_exit_code trexio_text_finalize(trexio_t* file);
+    #+end_src
+    
+    #+begin_src c :tangle trexio_text.c
+trexio_exit_code trexio_text_finalize(trexio_t* file) {
+  if (file  == NULL) return TREXIO_INVALID_ARG_1;
+
+  trexio_text_t* f = (trexio_text_t*) file;
+
+  trexio_exit_code rc;
+  rc = trexio_text_free_nucleus( (trexio_text_t*) file);
+  assert (rc == TREXIO_SUCCESS);
+
+  rc = trexio_text_free_rdm( (trexio_text_t*) file);
+  assert (rc == TREXIO_SUCCESS);
+  
+  /* Release lock */
+  struct flock fl;
+
+  fl.l_type   = F_WRLCK;
+  fl.l_whence = SEEK_SET;
+  fl.l_start  = 0;         
+  fl.l_len    = 0;         
+  fl.l_pid    = getpid();  
+  fl.l_type   = F_UNLCK;   
+  fcntl(f->lock_file, F_SETLK, &fl);
+    
+  close(f->lock_file);
+  return TREXIO_SUCCESS;
+}
+    #+end_src
+
+*** Nucleus struct
+
+**** Read the struct
+
+    #+begin_src c :tangle trexio_text.h
+nucleus_t* trexio_text_read_nucleus(trexio_text_t* file);
+    #+end_src
+
+    #+begin_src c :tangle trexio_text.c
+nucleus_t* trexio_text_read_nucleus(trexio_text_t* file) {
+  if (file == NULL) return NULL;
+
+  if (file->nucleus != NULL) return file->nucleus;
+  
+  /* Allocate the data structure */
+  nucleus_t* nucleus = (nucleus_t*) malloc(sizeof(nucleus_t));
+  assert (nucleus != NULL);
+
+  nucleus->file     = NULL;
+  nucleus->num      = 0;
+  nucleus->coord    = NULL;
+  nucleus->charge   = NULL;
+  nucleus->to_flush = 0;
+
+  /* Try to open the file. If the file does not exist, return */
+  const char* nucleus_file_name = "/nucleus.txt";
+  char * file_name = (char*)
+    calloc( strlen(file->parent.file_name) + strlen(nucleus_file_name) + 1,
+            sizeof(char));
+  assert (file_name != NULL);
+  strcpy (file_name, file->parent.file_name);
+  strcat (file_name, nucleus_file_name);
+
+  /* If the file exists, read it */
+  FILE* f = fopen(file_name,"r");
+  if (f != NULL) {
+    
+    /* Find size of file to allocate the max size of the string buffer */
+    fseek(f, 0L, SEEK_END);
+    size_t sz = ftell(f);
+    fseek(f, 0L, SEEK_SET);
+    char* buffer = (char*) malloc(sz*sizeof(char));
+    
+    /* Read the dimensioning variables */
+    int rc;
+    rc = fscanf(f, "%s", buffer);
+    assert (rc == 1);
+    assert (strcmp(buffer, "dim_charge") == 0);
+    
+    rc = fscanf(f, "%lu", &(nucleus->dim_charge));
+    assert (rc == 1);
+    
+    rc = fscanf(f, "%s", buffer);
+    assert (rc == 1);
+    assert (strcmp(buffer, "dim_coord") == 0);
+    
+    rc = fscanf(f, "%lu", &(nucleus->dim_coord));
+    assert (rc == 1);
+    
+    /* Allocate arrays */
+    nucleus->charge = (double*) calloc(nucleus->dim_charge, sizeof(double));
+    assert (nucleus->charge != NULL);
+    
+    nucleus->coord = (double*) calloc(nucleus->dim_coord, sizeof(double));
+    assert (nucleus->coord != NULL);
+    
+    /* Read data */
+    rc = fscanf(f, "%s", buffer);
+    assert (rc == 1);
+    assert (strcmp(buffer, "num") == 0);
+    
+    rc = fscanf(f, "%lu", &(nucleus->num));
+    assert (rc == 1);
+    
+    rc = fscanf(f, "%s", buffer);
+    assert (rc == 1);
+    assert (strcmp(buffer, "charge") == 0);
+    
+    for (uint64_t i=0 ; i<nucleus->dim_charge ; i++) {
+      rc = fscanf(f, "%lf", &(nucleus->charge[i]));
+      assert (rc == 1);
+    }
+    
+    rc = fscanf(f, "%s", buffer);
+    assert (rc == 1);
+    assert (strcmp(buffer, "coord") == 0);
+    
+    for (uint64_t i=0 ; i<nucleus->dim_coord ; i++) {
+      rc = fscanf(f, "%lf", &(nucleus->coord[i]));
+      assert (rc == 1);
+    }
+    free(buffer);
+    fclose(f);
+    f = NULL;
+  }
+  if (file->parent.mode == 'w') {
+    nucleus->file = fopen(file_name,"a");  
+  } else { 
+    nucleus->file = fopen(file_name,"r");  
+  }
+  free(file_name);
+  file->nucleus = nucleus;
+  return nucleus;
+}
+   #+end_src
+
+**** Flush the struct
+
+    #+begin_src c :tangle trexio_text.h
+trexio_exit_code trexio_text_flush_nucleus(const trexio_text_t* file);
+    #+end_src
+
+    #+begin_src c :tangle trexio_text.c
+trexio_exit_code trexio_text_flush_nucleus(const trexio_text_t* file) {
+  if (file == NULL) return TREXIO_INVALID_ARG_1;
+
+  if (file->parent.mode == 'r') return TREXIO_READONLY;
+
+  nucleus_t* nucleus = file->nucleus;
+  
+  if (nucleus == NULL) return TREXIO_SUCCESS;
+
+  if (nucleus->to_flush == 0) return TREXIO_SUCCESS;
+
+  FILE* f = nucleus->file;
+  assert (f != NULL);
+  rewind(f);
+
+  /* Write the dimensioning variables */
+  fprintf(f, "dim_charge %ld\n", nucleus->dim_charge);
+  fprintf(f, "dim_coord  %ld\n", nucleus->dim_coord );
+
+  /* Write arrays */
+  fprintf(f, "num %ld\n", nucleus->num);
+  fprintf(f, "charge\n");
+  for (uint64_t i=0 ; i<nucleus->dim_charge ; i++) {
+    fprintf(f, "%lf\n", nucleus->charge[i]);
+  }
+
+  fprintf(f, "coord\n");
+  for (uint64_t i=0 ; i<nucleus->dim_coord ; i++) {
+      fprintf(f, "%lf\n", nucleus->coord[i]);
+  }
+  fflush(f);
+  file->nucleus->to_flush = 0;
+  return TREXIO_SUCCESS;
+}
+   #+end_src
+
+**** Free memory
+
+     Memory is allocated when reading. The following function frees memory.
+    
+    #+begin_src c :tangle trexio_text.h
+trexio_exit_code trexio_text_free_nucleus(trexio_text_t* file);
+    #+end_src
+    
+    #+begin_src c :tangle trexio_text.c
+trexio_exit_code trexio_text_free_nucleus(trexio_text_t* file) {
+  if (file == NULL) return TREXIO_INVALID_ARG_1;
+  
+  trexio_exit_code rc;
+
+  if (file->parent.mode != 'r') {
+    rc = trexio_text_flush_nucleus(file);
+    if (rc != TREXIO_SUCCESS) return TREXIO_FAILURE;
+  }
+
+  nucleus_t* nucleus = file->nucleus;
+  if (nucleus == NULL) return TREXIO_SUCCESS;
+
+  if (nucleus->file != NULL) {
+    fclose(nucleus->file);
+    nucleus->file = NULL;
+  }
+
+  if (nucleus->coord != NULL) {
+    free (nucleus->coord);
+    nucleus->coord = NULL;
+  }
+  
+  if (nucleus->charge != NULL) {
+    free (nucleus->charge);
+    nucleus->charge = NULL;
+  }
+  
+  free (nucleus);
+  file->nucleus = NULL;
+  return TREXIO_SUCCESS;
+}
+    #+end_src
+
+**** Read/Write the num attribute
+
+    #+begin_src c :tangle trexio_text.h
+trexio_exit_code trexio_text_read_nucleus_num(const trexio_t* file, uint64_t* num);
+trexio_exit_code trexio_text_write_nucleus_num(const trexio_t* file, const uint64_t num);
+   #+end_src
+
+    #+begin_src c :tangle trexio_text.c
+trexio_exit_code trexio_text_read_nucleus_num(const trexio_t* file, uint64_t* num) {
+
+  if (file  == NULL) return TREXIO_INVALID_ARG_1;
+  if (num   == NULL) return TREXIO_INVALID_ARG_2;
+
+  nucleus_t* nucleus = trexio_text_read_nucleus((trexio_text_t*) file);
+  if (nucleus == NULL) return TREXIO_FAILURE;
+
+  /**/ *num = nucleus->num;
+
+  return TREXIO_SUCCESS;
+}
+
+ 
+trexio_exit_code trexio_text_write_nucleus_num(const trexio_t* file, const uint64_t num) {
+
+  if (file == NULL) return TREXIO_INVALID_ARG_1;
+
+  if (file->mode == 'r') return TREXIO_READONLY;
+  
+  nucleus_t* nucleus = trexio_text_read_nucleus((trexio_text_t*) file);
+  if (nucleus == NULL) return TREXIO_FAILURE;
+  
+  nucleus->num = num;
+  nucleus->to_flush = 1;
+  
+  return TREXIO_SUCCESS;
+}
+     #+end_src
+
+**** Read/Write the coord attribute
+
+     The ~coord~ array is assumed allocated with the appropriate size.
+    
+    #+begin_src c :tangle trexio_text.h
+trexio_exit_code trexio_text_read_nucleus_coord(const trexio_t* file, double* coord, const uint64_t dim_coord);
+trexio_exit_code trexio_text_write_nucleus_coord(const trexio_t* file, const double* coord, const uint64_t dim_coord);
+   #+end_src
+
+    #+begin_src c :tangle trexio_text.c
+trexio_exit_code trexio_text_read_nucleus_coord(const trexio_t* file, double* coord, const uint64_t dim_coord) {
+
+  if (file  == NULL) return TREXIO_INVALID_ARG_1;
+  if (coord == NULL) return TREXIO_INVALID_ARG_2;
+
+  nucleus_t* nucleus = trexio_text_read_nucleus((trexio_text_t*) file);
+  if (nucleus == NULL) return TREXIO_FAILURE;
+
+  if (dim_coord != nucleus->dim_coord) return TREXIO_INVALID_ARG_3;
+  
+  for (uint64_t i=0 ; i<dim_coord ; i++) {
+    coord[i] = nucleus->coord[i];
+  }
+
+  return TREXIO_SUCCESS;
+}
+
+ 
+trexio_exit_code trexio_text_write_nucleus_coord(const trexio_t* file, const double* coord, const uint64_t dim_coord) {
+  if (file  == NULL)  return TREXIO_INVALID_ARG_1;
+  if (coord == NULL)  return TREXIO_INVALID_ARG_2;
+
+  if (file->mode == 'r') return TREXIO_READONLY;
+
+  nucleus_t* nucleus = trexio_text_read_nucleus((trexio_text_t*) file);
+  if (nucleus == NULL) return TREXIO_FAILURE;
+  
+  if (nucleus->coord != NULL) {
+    free(nucleus->coord);
+    nucleus->coord = NULL;
+  }
+
+  nucleus->dim_coord = dim_coord;
+  nucleus->coord = (double*) calloc(dim_coord, sizeof(double));
+
+  for (uint64_t i=0 ; i<dim_coord ; i++) {
+    nucleus->coord[i] = coord[i];
+  }
+  
+  nucleus->to_flush = 1;
+  return TREXIO_SUCCESS;
+}
+     #+end_src
+**** Read/Write the charge attribute
+
+     The ~charge~ array is assumed allocated with the appropriate size.
+    
+    #+begin_src c :tangle trexio_text.h
+trexio_exit_code trexio_text_read_nucleus_charge(const trexio_t* file, double* charge, const uint64_t dim_charge);
+trexio_exit_code trexio_text_write_nucleus_charge(const trexio_t* file, const double* charge, const uint64_t dim_charge);
+   #+end_src
+
+    #+begin_src c :tangle trexio_text.c
+trexio_exit_code trexio_text_read_nucleus_charge(const trexio_t* file, double* charge, const uint64_t dim_charge) {
+
+  if (file   == NULL) return TREXIO_INVALID_ARG_1;
+  if (charge == NULL) return TREXIO_INVALID_ARG_2;
+
+  nucleus_t* nucleus = trexio_text_read_nucleus((trexio_text_t*) file);
+  if (nucleus == NULL) return TREXIO_FAILURE;
+
+  if (dim_charge != nucleus->dim_charge) return TREXIO_INVALID_ARG_3;
+  
+  for (uint64_t i=0 ; i<dim_charge ; i++) {
+    charge[i] = nucleus->charge[i];
+  }
+
+  return TREXIO_SUCCESS;
+}
+
+ 
+trexio_exit_code trexio_text_write_nucleus_charge(const trexio_t* file, const double* charge, const uint64_t dim_charge) {
+  if (file   == NULL)  return TREXIO_INVALID_ARG_1;
+  if (charge == NULL)  return TREXIO_INVALID_ARG_2;
+
+  if (file->mode == 'r') return TREXIO_READONLY;
+
+  nucleus_t* nucleus = trexio_text_read_nucleus((trexio_text_t*) file);
+  if (nucleus == NULL) return TREXIO_FAILURE;
+  
+  if (nucleus->charge != NULL) {
+    free(nucleus->charge);
+    nucleus->charge = NULL;
+  }
+
+  nucleus->dim_charge = dim_charge;
+  nucleus->charge = (double*) calloc(dim_charge, sizeof(double));
+
+  for (uint64_t i=0 ; i<dim_charge ; i++) {
+    nucleus->charge[i] = charge[i];
+  }
+  
+  nucleus->to_flush = 1;
+  return TREXIO_SUCCESS;
+}
+     #+end_src
+
+*** RDM struct
+**** Read the complete struct
+
+    #+begin_src c :tangle trexio_text.h
+rdm_t* trexio_text_read_rdm(trexio_text_t* file);
+    #+end_src
+    
+    #+begin_src c :tangle trexio_text.c
+rdm_t* trexio_text_read_rdm(trexio_text_t* file) {
+  if (file  == NULL) return NULL;
+
+  if (file->rdm != NULL) return file->rdm;
+
+  /* Allocate the data structure */
+  rdm_t* rdm = (rdm_t*) malloc(sizeof(rdm_t));
+  assert (rdm != NULL);
+
+  rdm->one_e           = NULL;
+  rdm->two_e_file_name = NULL;
+  rdm->file            = NULL;
+  rdm->to_flush        = 0;
+
+  /* Try to open the file. If the file does not exist, return */
+  const char* rdm_file_name = "/rdm.txt";
+  char * file_name = (char*)
+    calloc( strlen(file->parent.file_name) + strlen(rdm_file_name) + 1,
+            sizeof(char));
+  assert (file_name != NULL);
+  strcpy (file_name, file->parent.file_name);
+  strcat (file_name, rdm_file_name);
+
+  /* If the file exists, read it */
+  FILE* f = fopen(file_name,"r");
+  if (f != NULL) {
+    
+    /* Find size of file to allocate the max size of the string buffer */
+    fseek(f, 0L, SEEK_END);
+    size_t sz = ftell(f);
+    fseek(f, 0L, SEEK_SET);
+    char* buffer = (char*) malloc(sz*sizeof(char));
+    
+    /* Read the dimensioning variables */
+    int rc;
+    rc = fscanf(f, "%s", buffer);
+    assert (rc == 1);
+    assert (strcmp(buffer, "dim_one_e") == 0);
+    
+    rc = fscanf(f, "%lu", &(rdm->dim_one_e));
+    assert (rc == 1);
+    
+    /* Allocate arrays */
+    rdm->one_e = (double*) calloc(rdm->dim_one_e, sizeof(double));
+    assert (rdm->one_e != NULL);
+    
+    /* Read one_e */
+    rc = fscanf(f, "%s", buffer);
+    assert (rc == 1);
+    assert (strcmp(buffer, "one_e") == 0);
+    
+    for (uint64_t i=0 ; i<rdm->dim_one_e; i++) {
+      rc = fscanf(f, "%lf", &(rdm->one_e[i]));
+      assert (rc == 1);
+    }
+    
+    /* Read two_e */
+    rc = fscanf(f, "%s", buffer);
+    assert (rc == 1);
+    assert (strcmp(buffer, "two_e_file_name") == 0);
+    
+    rc = fscanf(f, "%s", buffer);
+    assert (rc == 1);
+    rdm->two_e_file_name = (char*) malloc (strlen(buffer)*sizeof(char));
+    strcpy(rdm->two_e_file_name, buffer);
+    
+    free(buffer);
+    fclose(f);
+    f = NULL;
+  }
+  if (file->parent.mode == 'w') {
+    rdm->file = fopen(file_name,"a");  
+  } else {
+    rdm->file = fopen(file_name,"");  
+  }
+  free(file_name);
+  file->rdm = rdm ;
+  return rdm;
+}
+   #+end_src
+
+**** Flush the complete struct
+
+    #+begin_src c :tangle trexio_text.h
+trexio_exit_code trexio_text_flush_rdm(const trexio_text_t* file);
+    #+end_src
+
+    #+begin_src c :tangle trexio_text.c
+trexio_exit_code trexio_text_flush_rdm(const trexio_text_t* file) {
+  if (file == NULL) return TREXIO_INVALID_ARG_1;
+
+  if (file->parent.mode == 'r') return TREXIO_READONLY;
+
+  rdm_t* rdm = file->rdm;
+  if (rdm == NULL) return TREXIO_SUCCESS;
+
+  if (rdm->to_flush == 0) return TREXIO_SUCCESS;
+
+  FILE* f = rdm->file;
+  assert (f != NULL);
+  rewind(f);
+
+  /* Write the dimensioning variables */
+  fprintf(f, "num %ld\n", rdm->dim_one_e);
+
+  /* Write arrays */
+  fprintf(f, "one_e\n");
+  for (uint64_t i=0 ; i< rdm->dim_one_e; i++) {
+    fprintf(f, "%lf\n", rdm->one_e[i]);
+  }
+
+  fprintf(f, "two_e_file_name\n");
+  fprintf(f, "%s\n", rdm->two_e_file_name);
+
+  fflush(f);
+  file->rdm->to_flush = 0;
+  return TREXIO_SUCCESS;
+}
+   #+end_src
+
+**** Free memory
+
+     Memory is allocated when reading. The followig function frees memory.
+    
+    #+begin_src c :tangle trexio_text.h
+trexio_exit_code trexio_text_free_rdm(trexio_text_t* file);
+    #+end_src
+    
+    #+begin_src c :tangle trexio_text.c
+trexio_exit_code trexio_text_free_rdm(trexio_text_t* file) {
+  if (file == NULL) return TREXIO_INVALID_ARG_1;
+  
+  trexio_exit_code rc;
+  if (file->parent.mode != 'r') {
+    rc = trexio_text_flush_rdm(file);
+    if (rc != TREXIO_SUCCESS) return TREXIO_FAILURE;
+  }
+
+  rdm_t* rdm = file->rdm;
+  if (rdm == NULL) return TREXIO_SUCCESS;
+
+  if (rdm->file != NULL) {
+    fclose(rdm->file);
+    rdm->file = NULL;
+  }
+  
+  if (rdm->one_e != NULL) {
+    free (rdm->one_e);
+    rdm->one_e = NULL;
+  }
+  
+  if (rdm->two_e_file_name != NULL) {
+    free (rdm->two_e_file_name);
+    rdm->two_e_file_name = NULL;
+  }
+  
+  free (rdm);
+  file->rdm = NULL;
+  return TREXIO_SUCCESS;
+}
+    #+end_src
+
+**** Read/Write the one_e attribute
+
+     The ~one_e~ array is assumed allocated with the appropriate size.
+    
+    #+begin_src c :tangle trexio_text.h
+trexio_exit_code trexio_text_read_rdm_one_e(const trexio_t* file, double* one_e, const uint64_t dim_one_e);
+trexio_exit_code trexio_text_write_rdm_one_e(const trexio_t* file, const double* one_e, const uint64_t dim_one_e);
+   #+end_src
+
+    #+begin_src c :tangle trexio_text.c
+trexio_exit_code trexio_text_read_rdm_one_e(const trexio_t* file, double* one_e, const uint64_t dim_one_e) {
+
+  if (file  == NULL) return TREXIO_INVALID_ARG_1;
+  if (one_e == NULL) return TREXIO_INVALID_ARG_2;
+
+  rdm_t* rdm = trexio_text_read_rdm((trexio_text_t*) file);
+  if (rdm == NULL) return TREXIO_FAILURE;
+
+  if (dim_one_e != rdm->dim_one_e) return TREXIO_INVALID_ARG_3;
+
+  for (uint64_t i=0 ; i<dim_one_e ; i++) {
+    one_e[i] = rdm->one_e[i];
+  }
+
+  return TREXIO_SUCCESS;
+}
+
+ 
+trexio_exit_code trexio_text_write_rdm_one_e(const trexio_t* file, const double* one_e, const uint64_t dim_one_e) {
+  if (file  == NULL)  return TREXIO_INVALID_ARG_1;
+  if (one_e == NULL)  return TREXIO_INVALID_ARG_2;
+  if (file->mode != 'r') return TREXIO_READONLY;
+
+  rdm_t* rdm = trexio_text_read_rdm((trexio_text_t*) file);
+  if (rdm == NULL) return TREXIO_FAILURE;
+  
+  rdm->dim_one_e = dim_one_e;
+  for (uint64_t i=0 ; i<dim_one_e ; i++) {
+    rdm->one_e[i] = one_e[i];
+  }
+  
+  rdm->to_flush = 1;
+  return TREXIO_SUCCESS;
+}
+     #+end_src
+
+**** Read/Write the two_e attribute
+
+     ~two_e~ is a sparse data structure, which can be too large to fit
+     in memory. So we provide functions to read and write it by
+     chunks.
+     In the text back end, the easiest way to do it is to create a
+     file for each sparse float structure.
+    
+    #+begin_src c :tangle trexio_text.h
+trexio_exit_code trexio_text_buffered_read_rdm_two_e(const trexio_t* file, const uint64_t offset, const uint64_t size, int64_t* index, double* value);
+trexio_exit_code trexio_text_buffered_write_rdm_two_e(const trexio_t* file, const uint64_t offset, const uint64_t size, const int64_t* index, const double* value);
+   #+end_src
+
+    #+begin_src c :tangle trexio_text.c
+trexio_exit_code trexio_text_buffered_read_rdm_two_e(const trexio_t* file, const uint64_t offset, const uint64_t size, int64_t* index, double* value) {
+
+  if (file  == NULL) return TREXIO_INVALID_ARG_1;
+  if (index == NULL) return TREXIO_INVALID_ARG_4;
+  if (value == NULL) return TREXIO_INVALID_ARG_5;
+
+  rdm_t* rdm = trexio_text_read_rdm((trexio_text_t*) file);
+  if (rdm == NULL) return TREXIO_FAILURE;
+
+  FILE* f = fopen(rdm->two_e_file_name, "r");
+  if (f == NULL) return TREXIO_END;
+
+  const uint64_t line_length = 64;
+  fseek(f, (long) offset * line_length, SEEK_SET);
+  
+  int rc;
+  for (uint64_t i=0 ; i<size ; i++) {
+    rc = fscanf(f, "%9ld %9ld %9ld %9ld %24le\n",
+           &index[4*i], 
+           &index[4*i+1], 
+           &index[4*i+2], 
+           &index[4*i+3], 
+           &value[i]);
+    if (rc == 5) {
+      /* Do nothing */
+    } else if (rc == EOF) {
+      return TREXIO_END;
+    } else if (rc == EOF) {
+      return TREXIO_FAILURE;
+    }
+  }
+
+  return TREXIO_SUCCESS;
+}
+
+ 
+trexio_exit_code trexio_text_buffered_write_rdm_two_e(const trexio_t* file, const uint64_t offset, const uint64_t size, const int64_t* index, const double* value) {
+  if (file  == NULL) return TREXIO_INVALID_ARG_1;
+  if (index == NULL) return TREXIO_INVALID_ARG_4;
+  if (value == NULL) return TREXIO_INVALID_ARG_5;
+  if (file->mode != 'r') return TREXIO_READONLY;
+
+  rdm_t* rdm = trexio_text_read_rdm((trexio_text_t*) file);
+  if (rdm == NULL) return TREXIO_FAILURE;
+
+  FILE* f = fopen(rdm->two_e_file_name, "w");
+  if (f == NULL) return TREXIO_FAILURE;
+
+  const uint64_t line_length = 64;
+  fseek(f, (long) offset * line_length, SEEK_SET);
+  
+  int rc;
+  for (uint64_t i=0 ; i<size ; i++) {
+    rc = fprintf(f, "%9ld %9ld %9ld %9ld %24le\n",
+           index[4*i], 
+           index[4*i+1], 
+           index[4*i+2], 
+           index[4*i+3], 
+           value[i]);
+    if (rc != 5) return TREXIO_FAILURE;
+  }
+
+  return TREXIO_SUCCESS;
+}
+     #+end_src
+
+* File suffixes                                                     :noxport:
+
+  #+begin_src c :tangle trexio_text.h
+#endif
+  #+end_src
+