Simplify and improve Base64 decoding:
- drop whitespace handling
- check for invalid bytes
Adjust test cases accordingly
git-svn-id: https://svn.apache.org/repos/asf/commons/proper/fileupload/trunk@1458597 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/src/main/java/org/apache/commons/fileupload/util/mime/Base64Decoder.java b/src/main/java/org/apache/commons/fileupload/util/mime/Base64Decoder.java
index 9d205e7..f151c96 100644
--- a/src/main/java/org/apache/commons/fileupload/util/mime/Base64Decoder.java
+++ b/src/main/java/org/apache/commons/fileupload/util/mime/Base64Decoder.java
@@ -25,6 +25,21 @@
final class Base64Decoder {
/**
+ * Decoding table value for invalid bytes.
+ */
+ private static final int INVALID_BYTE = -1; // must be outside range 0-63
+
+ /**
+ * Mask to treat byte as unsigned integer.
+ */
+ private static final int MASK_BYTE_UNSIGNED = 0xFF;
+
+ /**
+ * Number of bytes per encoded chunk - 4 6bit bytes produce 3 8bit bytes on output.
+ */
+ private static final int INPUT_BYTES_PER_CHUNK = 4;
+
+ /**
* Set up the encoding table.
*/
private static final byte[] ENCODING_TABLE = {
@@ -54,6 +69,11 @@
private static final byte[] DECODING_TABLE = new byte[Byte.MAX_VALUE - Byte.MIN_VALUE + 1];
static {
+ // Initialise as all invalid characters
+ for (int i = 0; i < DECODING_TABLE.length; i++) {
+ DECODING_TABLE[i] = INVALID_BYTE;
+ }
+ // set up valid characters
for (int i = 0; i < ENCODING_TABLE.length; i++) {
DECODING_TABLE[ENCODING_TABLE[i]] = (byte) i;
}
@@ -67,17 +87,6 @@
}
/**
- * Checks if the input char must be skipped from the decode.
- * The method skips whitespace characters LF, CR, horizontal tab and space.
- *
- * @param c the char to be checked.
- * @return true, if the input char has to be skipped, false otherwise.
- */
- private static boolean ignore(char c) {
- return (c == '\n' || c == '\r' || c == '\t' || c == ' ');
- }
-
- /**
* Decode the base 64 encoded byte data writing it to the given output stream,
* whitespace characters will be ignored.
*
@@ -87,89 +96,46 @@
* @return the number of bytes produced.
*/
public static int decode(byte[] data, OutputStream out) throws IOException {
- byte b1, b2, b3, b4;
int outLen = 0;
+ byte [] cache = new byte[INPUT_BYTES_PER_CHUNK];
+ int cachedBytes = 0;
- if (data.length == 0) {
- return outLen;
- }
-
- int end = data.length;
-
- while (end > 0) {
- if (!ignore((char) data[end - 1])) {
+ for (byte b : data) {
+ if (b == PADDING) { // Padding means end of input
break;
}
-
- end--;
- }
-
- int i = 0;
- // CHECKSTYLE IGNORE MagicNumber FOR NEXT 1 LINE
- int finish = end - 4; // last set of 4 bytes might include padding
-
- while (i < finish) {
- while ((i < finish) && ignore((char) data[i])) {
- i++;
+ final byte d = DECODING_TABLE[MASK_BYTE_UNSIGNED & b];
+ if (d == INVALID_BYTE) {
+ throw new IOException("Invalid Base64 byte: " + b);
}
+ cache[cachedBytes++] = d;
+ if (cachedBytes == INPUT_BYTES_PER_CHUNK) {
+ // Convert 4 6-bit bytes to 3 8-bit bytes
+ // CHECKSTYLE IGNORE MagicNumber FOR NEXT 3 LINES
+ out.write((cache[0] << 2) | (cache[1] >> 4)); // 6 bits of b1 plus 2 bits of b2
+ out.write((cache[1] << 4) | (cache[2] >> 2)); // 4 bits of b2 plus 4 bits of b3
+ out.write((cache[2] << 6) | cache[3]); // 2 bits of b3 plus 6 bits of b4
- b1 = DECODING_TABLE[data[i++]];
-
- while ((i < finish) && ignore((char) data[i])) {
- i++;
- }
-
- b2 = DECODING_TABLE[data[i++]];
-
- while ((i < finish) && ignore((char) data[i])) {
- i++;
- }
-
- b3 = DECODING_TABLE[data[i++]];
-
- while ((i < finish) && ignore((char) data[i])) {
- i++;
- }
-
- b4 = DECODING_TABLE[data[i++]];
-
- // Convert 4 6-bit bytes to 3 8-bit bytes
- // CHECKSTYLE IGNORE MagicNumber FOR NEXT 3 LINES
- out.write((b1 << 2) | (b2 >> 4)); // 6 bits of b1 plus 2 bits of b2
- out.write((b2 << 4) | (b3 >> 2)); // 4 bits of b2 plus 4 bits of b3
- out.write((b3 << 6) | b4); // 2 bits of b3 plus 6 bits of b4
-
- // CHECKSTYLE IGNORE MagicNumber FOR NEXT 1 LINE
- outLen += 3;
- }
-
- // Get the last 4 bytes; only last two can be padding
- b1 = DECODING_TABLE[data[i++]];
- b2 = DECODING_TABLE[data[i++]];
-
- // always write the first byte
- // CHECKSTYLE IGNORE MagicNumber FOR NEXT 1 LINE
- out.write((b1 << 2) | (b2 >> 4)); // 6 bits of b1 plus 2 bits of b2
- outLen++;
-
- byte p1 = data[i++];
- byte p2 = data[i++];
-
- b3 = DECODING_TABLE[p1]; // may be needed later
-
- if (p1 != PADDING) { // Nothing more to do if p1 == PADDING
- // CHECKSTYLE IGNORE MagicNumber FOR NEXT 1 LINE
- out.write((b2 << 4) | (b3 >> 2)); // 4 bits of b2 plus 4 bits of b3
- outLen++;
- if (p2 != PADDING) { // Nothing more to do if p2 == PADDING
- b4 = DECODING_TABLE[p2];
// CHECKSTYLE IGNORE MagicNumber FOR NEXT 1 LINE
- out.write((b3 << 6) | b4); // 2 bits of b3 plus 6 bits of b4
- outLen++;
+ outLen += 3;
+ cachedBytes = 0;
}
}
-
+ // CHECKSTYLE IGNORE MagicNumber FOR NEXT 2 LINES
+ if (cachedBytes >= 2) {
+ out.write((cache[0] << 2) | (cache[1] >> 4)); // 6 bits of b1 plus 2 bits of b2
+ outLen++;
+ // CHECKSTYLE IGNORE MagicNumber FOR NEXT 2 LINES
+ if (cachedBytes >= 3) {
+ out.write((cache[1] << 4) | (cache[2] >> 2)); // 4 bits of b2 plus 4 bits of b3
+ outLen++;
+ // CHECKSTYLE IGNORE MagicNumber FOR NEXT 2 LINES
+ if (cachedBytes >= 4) {
+ out.write((cache[2] << 6) | cache[3]); // 2 bits of b3 plus 6 bits of b4
+ outLen++;
+ }
+ }
+ }
return outLen;
}
-
}
diff --git a/src/test/java/org/apache/commons/fileupload/util/mime/Base64DecoderTestCase.java b/src/test/java/org/apache/commons/fileupload/util/mime/Base64DecoderTestCase.java
index fa4beb4..94e0b8c 100644
--- a/src/test/java/org/apache/commons/fileupload/util/mime/Base64DecoderTestCase.java
+++ b/src/test/java/org/apache/commons/fileupload/util/mime/Base64DecoderTestCase.java
@@ -19,6 +19,7 @@
import static org.junit.Assert.assertArrayEquals;
import java.io.ByteArrayOutputStream;
+import java.io.IOException;
import org.junit.Test;
@@ -55,15 +56,15 @@
}
/**
- * Test our decode with a pad character in the middle.
+ * Test our decode with pad character in the middle.
+ * Returns data up to pad character.
*
- * Contrary to Apache Commons-Codec implementation, doesn't halt decode and return what we've got so far.
*
* @throws Exception if any error occurs while decoding the input string.
*/
@Test
public void decodeWithInnerPad() throws Exception {
- assertEncoded("Hello World\0Hello World", "SGVsbG8gV29ybGQ=SGVsbG8gV29ybGQ=");
+ assertEncoded("Hello World", "SGVsbG8gV29ybGQ=SGVsbG8gV29ybGQ=");
}
private static void assertEncoded(String clearText, String encoded) throws Exception {
@@ -78,16 +79,13 @@
}
/**
- * Throws ArrayIndexOutOfBoundsException on some non-BASE64 bytes.
- *
- * This is fixed in Apache Commons-Codec.
+ * Throws IOException for non-BASE64 bytes.
*
* @throws Exception
- * @see <a href="https://issues.apache.org/jira/browse/CODEC-68">CODEC-68</a>
*/
- @Test(expected = ArrayIndexOutOfBoundsException.class)
+ @Test(expected = IOException.class)
public void nonBase64Bytes() throws Exception {
- final byte[] x = new byte[]{'n', 'A', '=', '=', (byte) 0x9c};
+ final byte[] x = new byte[]{'n', 'A', (byte) 0x9c};
Base64Decoder.decode(x, new ByteArrayOutputStream());
}
