Java Utililty Methods RandomAccessFile Read

void appendFile(RandomAccessFile main, RandomAccessFile extra)
Append the contents of extra file to main.

byte[] buf = new byte[1024 * 1024]; 
main.seek(main.length());
extra.seek(0);
while (true) {
 int count = extra.read(buf);
 if (count == -1)
 break;
 main.write(buf, 0, count);
...

byte[] load(String f)
Loads an entire file from the filesystem.

return load(new File(f));

double[][] load(String fn, int type, int m, int n)
read a matrix from a binary file.

if (m <= 0 && n <= 0)
 return null;
RandomAccessFile file = new RandomAccessFile(fn, "r");
long l = file.length();
if (l < 0) {
 file.close();
 return null;
l /= dt_size[type];
if (m <= 0)
 m = (int) (l / n);
else if (n <= 0)
 n = (int) (l / m);
if (m <= 0 || n <= 0) {
 file.close();
 return null;
double[][] x = new double[m][n];
switch (type) {
case DT_BYTE: 
 for (int j = 0; j < n; j++)
 for (int i = 0; i < m; i++)
 x[i][j] = (double) (0xff & (int) file.readByte());
 break;
case DT_SHORT:
 for (int j = 0; j < n; j++)
 for (int i = 0; i < m; i++)
 x[i][j] = (double) file.readShort();
 break;
case DT_INT:
 for (int j = 0; j < n; j++)
 for (int i = 0; i < m; i++)
 x[i][j] = (double) file.readInt();
 break;
case DT_FLOAT:
 for (int j = 0; j < n; j++)
 for (int i = 0; i < m; i++)
 x[i][j] = (double) file.readFloat();
 break;
case DT_DOUBLE:
 for (int j = 0; j < n; j++)
 for (int i = 0; i < m; i++)
 x[i][j] = file.readDouble();
 break;
default:
 file.close();
 throw new IllegalArgumentException("Illegal data type");
file.close();
return x;

double[] LoadDspaceMapFile(String filename)
Get the array of diffractometer constants to map from time-of-flight to d-spacing, for each DAS ID.

int bytes_per_record = 8; 
CheckFile(filename);
File map_file = new File(filename);
long file_size = map_file.length();
if (file_size % bytes_per_record != 0)
 throw new IllegalArgumentException(filename + " is not a d-space map.");
long n_ids = file_size / bytes_per_record;
byte[] buffer = new byte[(int) file_size];
...

float[] LoadFloatFile(String filename)
Get an array of float values from a file of bytes, in PC order.

try {
 RandomAccessFile r_file = new RandomAccessFile(filename, "r");
 long num_bytes = r_file.length();
 if (num_bytes >= 4l * (long) (Integer.MAX_VALUE))
 throw new IllegalArgumentException("File has more than " + Integer.MAX_VALUE
 + " float values and can't be loaded into an array");
 int num_floats = (int) (num_bytes / 4);
 float[] list = new float[num_floats];
...

Vector LoadGhostMapFile(String filename, int n_ids, int n_ghosts)
Get the table of (id,weight) pairs from the specified file.

int bytes_per_record = n_ghosts * 12; 
CheckFile(filename);
File ghost_file = new File(filename);
long file_size = ghost_file.length();
if (file_size % bytes_per_record != 0)
 throw new IllegalArgumentException(filename + " is not a ghost map.");
if (file_size < bytes_per_record * n_ghosts)
 throw new IllegalArgumentException(filename + " only has records for " + file_size / bytes_per_record
...

HashMap read_arraydesc(final RandomAccessFile raf)
reaarraydesc

HashMap<String, Object> arraydesc = new HashMap<>();
arraydesc.put("arrstart", read_long(raf));
int arrStart = (int) arraydesc.get("arrstart");
switch (arrStart) {
case 8:
 skip_bytes(raf, 4);
 arraydesc.put("nbytes", read_long(raf));
 arraydesc.put("nelements", read_long(raf));
...

int read_int32(RandomAccessFile raf)
Reads an Integer (-2147483648 to 2147483647).

byte[] data = new byte[4];
int intData = -1;
try {
 raf.read(data);
 intData = ByteBuffer.wrap(data).getInt();
} catch (IOException e) {
return intData;
...

int read_long(final RandomAccessFile raf)
realong

byte[] data = new byte[4];
raf.read(data);
ByteBuffer bb = ByteBuffer.allocate(data.length);
bb.put(data);
return bb.getInt(0);

String read_string(final RandomAccessFile raf)
reastring

int length = read_long(raf);
String result;
if (length > 0) {
 byte[] data = new byte[length];
 raf.read(data);
 align_32(raf);
 result = new String(data, StandardCharsets.UTF_8);
} else {
...