--- /dev/null
+/*
+ * Copyright 2002-2015 Drew Noakes
+ *
+ * More information about this project is available at:
+ *
+ * https://drewnoakes.com/code/exif/
+ * https://github.com/drewnoakes/metadata-extractor
+ */
+
+package tim.prune.jpeg.drew;
+
+import java.io.IOException;
+
+
+/**
+ * Provides methods to read specific values from a byte array,
+ * with a consistent, checked exception structure for issues.
+ *
+ * @author Drew Noakes https://drewnoakes.com
+ */
+public class ByteArrayReader
+{
+ private final byte[] _buffer;
+ private boolean _isMotorolaByteOrder = true;
+
+ public ByteArrayReader(byte[] buffer)
+ {
+ if (buffer == null)
+ throw new NullPointerException();
+
+ _buffer = buffer;
+ }
+
+ public void setMotorolaByteOrder(boolean motorolaByteOrder)
+ {
+ _isMotorolaByteOrder = motorolaByteOrder;
+ }
+
+ public long getLength()
+ {
+ return _buffer.length;
+ }
+
+ protected byte getByte(int index)
+ {
+ return _buffer[index];
+ }
+
+ protected void validateIndex(int index, int bytesRequested) throws ExifException
+ {
+ if (!isValidIndex(index, bytesRequested))
+ throw new ExifException("Invalid index " + index);
+ }
+
+ private boolean isValidIndex(int index, int bytesRequested)
+ {
+ return bytesRequested >= 0
+ && index >= 0
+ && ((long)index + (long)bytesRequested) <= (long)_buffer.length;
+ }
+
+ public byte[] getBytes(int index, int count) throws ExifException
+ {
+ validateIndex(index, count);
+
+ byte[] bytes = new byte[count];
+ System.arraycopy(_buffer, index, bytes, 0, count);
+ return bytes;
+ }
+
+ /**
+ * Returns an unsigned 8-bit int calculated from one byte of data at the specified index.
+ *
+ * @param index position within the data buffer to read byte
+ * @return the 8 bit int value, between 0 and 255
+ * @throws IOException the buffer does not contain enough bytes to service the request, or index is negative
+ */
+ public short getUInt8(int index) throws ExifException
+ {
+ validateIndex(index, 1);
+
+ return (short) (getByte(index) & 0xFF);
+ }
+
+ /**
+ * Returns a signed 8-bit int calculated from one byte of data at the specified index.
+ *
+ * @param index position within the data buffer to read byte
+ * @return the 8 bit int value, between 0x00 and 0xFF
+ * @throws IOException the buffer does not contain enough bytes to service the request, or index is negative
+ */
+ public byte getInt8(int index) throws ExifException
+ {
+ validateIndex(index, 1);
+
+ return getByte(index);
+ }
+
+ /**
+ * Returns an unsigned 16-bit int calculated from two bytes of data at the specified index.
+ *
+ * @param index position within the data buffer to read first byte
+ * @return the 16 bit int value, between 0x0000 and 0xFFFF
+ * @throws IOException the buffer does not contain enough bytes to service the request, or index is negative
+ */
+ public int getUInt16(int index) throws ExifException
+ {
+ validateIndex(index, 2);
+
+ if (_isMotorolaByteOrder) {
+ // Motorola - MSB first
+ return (getByte(index ) << 8 & 0xFF00) |
+ (getByte(index + 1) & 0xFF);
+ } else {
+ // Intel ordering - LSB first
+ return (getByte(index + 1) << 8 & 0xFF00) |
+ (getByte(index ) & 0xFF);
+ }
+ }
+
+ /**
+ * Returns a signed 16-bit int calculated from two bytes of data at the specified index (MSB, LSB).
+ *
+ * @param index position within the data buffer to read first byte
+ * @return the 16 bit int value, between 0x0000 and 0xFFFF
+ * @throws IOException the buffer does not contain enough bytes to service the request, or index is negative
+ */
+ public short getInt16(int index) throws ExifException
+ {
+ validateIndex(index, 2);
+
+ if (_isMotorolaByteOrder) {
+ // Motorola - MSB first
+ return (short) (((short)getByte(index ) << 8 & (short)0xFF00) |
+ ((short)getByte(index + 1) & (short)0xFF));
+ } else {
+ // Intel ordering - LSB first
+ return (short) (((short)getByte(index + 1) << 8 & (short)0xFF00) |
+ ((short)getByte(index ) & (short)0xFF));
+ }
+ }
+
+ /**
+ * Get a 32-bit unsigned integer from the buffer, returning it as a long.
+ *
+ * @param index position within the data buffer to read first byte
+ * @return the unsigned 32-bit int value as a long, between 0x00000000 and 0xFFFFFFFF
+ * @throws IOException the buffer does not contain enough bytes to service the request, or index is negative
+ */
+ public long getUInt32(int index) throws ExifException
+ {
+ validateIndex(index, 4);
+
+ if (_isMotorolaByteOrder) {
+ // Motorola - MSB first (big endian)
+ return (((long)getByte(index )) << 24 & 0xFF000000L) |
+ (((long)getByte(index + 1)) << 16 & 0xFF0000L) |
+ (((long)getByte(index + 2)) << 8 & 0xFF00L) |
+ (((long)getByte(index + 3)) & 0xFFL);
+ } else {
+ // Intel ordering - LSB first (little endian)
+ return (((long)getByte(index + 3)) << 24 & 0xFF000000L) |
+ (((long)getByte(index + 2)) << 16 & 0xFF0000L) |
+ (((long)getByte(index + 1)) << 8 & 0xFF00L) |
+ (((long)getByte(index )) & 0xFFL);
+ }
+ }
+
+ /**
+ * Returns a signed 32-bit integer from four bytes of data at the specified index the buffer.
+ *
+ * @param index position within the data buffer to read first byte
+ * @return the signed 32 bit int value, between 0x00000000 and 0xFFFFFFFF
+ * @throws IOException the buffer does not contain enough bytes to service the request, or index is negative
+ */
+ public int getInt32(int index) throws ExifException
+ {
+ validateIndex(index, 4);
+
+ if (_isMotorolaByteOrder) {
+ // Motorola - MSB first (big endian)
+ return (getByte(index ) << 24 & 0xFF000000) |
+ (getByte(index + 1) << 16 & 0xFF0000) |
+ (getByte(index + 2) << 8 & 0xFF00) |
+ (getByte(index + 3) & 0xFF);
+ } else {
+ // Intel ordering - LSB first (little endian)
+ return (getByte(index + 3) << 24 & 0xFF000000) |
+ (getByte(index + 2) << 16 & 0xFF0000) |
+ (getByte(index + 1) << 8 & 0xFF00) |
+ (getByte(index ) & 0xFF);
+ }
+ }
+
+ /**
+ * Creates a String from the _data buffer starting at the specified index,
+ * and ending where <code>byte=='\0'</code> or where <code>length==maxLength</code>.
+ *
+ * @param index The index within the buffer at which to start reading the string.
+ * @param maxLengthBytes The maximum number of bytes to read. If a zero-byte is not reached within this limit,
+ * reading will stop and the string will be truncated to this length.
+ * @return The read string.
+ * @throws IOException The buffer does not contain enough bytes to satisfy this request.
+ */
+ public String getNullTerminatedString(int index, int maxLengthBytes) throws ExifException
+ {
+ // NOTE currently only really suited to single-byte character strings
+
+ byte[] bytes = getBytes(index, maxLengthBytes);
+
+ // Count the number of non-null bytes
+ int length = 0;
+ while (length < bytes.length && bytes[length] != '\0')
+ length++;
+
+ return new String(bytes, 0, length);
+ }
+
+ public String getString(int index, int bytesRequested) throws ExifException
+ {
+ // TODO: validate index
+ return new String(getBytes(index, bytesRequested));
+ }
+}
projects / GpsPrune.git / blobdiff