Add PotentialFileReader and use it in PairSW

src/potential_file_reader.cpp

@@ -0,0 +1,82 @@
+/* -*- c++ -*- ----------------------------------------------------------
+   LAMMPS - Large-scale Atomic/Molecular Massively Parallel Simulator
+   http://lammps.sandia.gov, Sandia National Laboratories
+   Steve Plimpton, sjplimp@sandia.gov
+
+   Copyright (2003) Sandia Corporation.  Under the terms of Contract
+   DE-AC04-94AL85000 with Sandia Corporation, the U.S. Government retains
+   certain rights in this software.  This software is distributed under
+   the GNU General Public License.
+
+   See the README file in the top-level LAMMPS directory.
+------------------------------------------------------------------------- */
+
+/* ----------------------------------------------------------------------
+   Contributing authors: Richard Berger (Temple U)
+------------------------------------------------------------------------- */
+
+#include "lammps.h"
+#include "force.h"
+#include "error.h"
+#include "comm.h"
+#include "potential_file_reader.h"
+#include "utils.h"
+
+#include <cstring>
+
+using namespace LAMMPS_NS;
+
+PotentialFileReader::PotentialFileReader(LAMMPS *lmp,
+                                         const std::string &filename,
+                                         const std::string &potential_name) : Pointers(lmp) {
+  if (comm->me != 0) {
+    error->one(FLERR, "PotentialFileReader should only be called by proc 0!");
+  }
+
+  fp = force->open_potential(filename.c_str());
+
+  if (fp == NULL) {
+    char str[128];
+    snprintf(str, 128, "cannot open %s potential file %s", potential_name.c_str(), filename.c_str());
+    error->one(FLERR, str);
+  }
+}
+
+PotentialFileReader::~PotentialFileReader() {
+  fclose(fp);
+}
+
+char *PotentialFileReader::next_line(int nparams) {
+  // concatenate lines until have nparams words
+  int n = 0;
+  int nwords = 0;
+
+  do {
+    char *ptr = fgets(&line[n], MAXLINE - n, fp);
+
+    if (ptr == nullptr) {
+      // EOF
+      if (nwords > 0 && nwords < nparams)
+      {
+        char str[128];
+        snprintf(str, 128, "Incorrect format in %s potential file", potential_name.c_str());
+        error->all(FLERR, str);
+      }
+
+      return nullptr;
+    }
+
+    // strip comment
+    if ((ptr = strchr(line, '#'))) *ptr = '\0';
+
+    nwords = utils::count_words(line);
+
+    // skip line if blank
+    if (nwords == 0)
+      continue;
+
+    n = strlen(line) + 1;
+  } while (nwords < nparams);
+
+  return line;
+}