add tool to regularize/reformat/reindent JSON files

tools/json/reformat-json.cpp

@@ -0,0 +1,47 @@
+
+#include "json.h"
+
+#include <cerrno>
+#include <cstdio>
+#include <string>
+
+using json = LAMMPS_NS::json;
+
+int main(int argc, char **argv)
+{
+  if (argc < 3) {
+    printf("Usage: %s <indent-width> <json-file-1> [<json-file-2> ...]\n", argv[0]);
+    return 1;
+  }
+
+  int indent = std::stoi(argv[1]);
+
+  // loop over files
+
+  for (int i=2; i < argc; ++i) {
+    std::string file = argv[i];
+    std::string backup = file + ".bak";
+
+    FILE *fp = fopen(file.c_str(), "r");
+    if (!fp) {
+      printf("Cannot open file %s for reading: %s\n", file.c_str(), strerror(errno));
+      return 2;
+    }
+
+    auto jsondata = json::parse(fp, nullptr, true, true);
+    fclose(fp);
+
+    rename(file.c_str(), backup.c_str());
+
+    fp = fopen(file.c_str(), "w");
+    if (!fp) {
+      printf("Cannot open file %s for writing: %s\n", file.c_str(), strerror(errno));
+      return 3;
+    }
+    std::string data = jsondata.dump(indent);
+    data += '\n';
+    fputs(data.c_str(), fp);
+    fclose(fp);
+  }
+  return 0;
+}