org.apache.commons.codec.binary.BaseNCodec Maven / Gradle / Ivy
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.commons.codec.binary;
import java.util.Arrays;
import java.util.Objects;
import java.util.function.Supplier;
import org.apache.commons.codec.BinaryDecoder;
import org.apache.commons.codec.BinaryEncoder;
import org.apache.commons.codec.CodecPolicy;
import org.apache.commons.codec.DecoderException;
import org.apache.commons.codec.EncoderException;
/**
* Abstract superclass for Base-N encoders and decoders.
*
*
* This class is thread-safe.
*
*
* You can set the decoding behavior when the input bytes contain leftover trailing bits that cannot be created by a
* valid encoding. These can be bits that are unused from the final character or entire characters. The default mode is
* lenient decoding.
*
*
* - Lenient: Any trailing bits are composed into 8-bit bytes where possible. The remainder are discarded.
*
- Strict: The decoding will raise an {@link IllegalArgumentException} if trailing bits are not part of a valid
* encoding. Any unused bits from the final character must be zero. Impossible counts of entire final characters are not
* allowed.
*
*
* When strict decoding is enabled it is expected that the decoded bytes will be re-encoded to a byte array that matches
* the original, i.e. no changes occur on the final character. This requires that the input bytes use the same padding
* and alphabet as the encoder.
*
*/
public abstract class BaseNCodec implements BinaryEncoder, BinaryDecoder {
/**
* Builds {@link Base64} instances.
*
* @param the codec type to build.
* @param the codec builder subtype.
* @since 1.17.0
*/
public abstract static class AbstractBuilder> implements Supplier {
private CodecPolicy decodingPolicy = DECODING_POLICY_DEFAULT;
private int lineLength;
private byte[] lineSeparator = CHUNK_SEPARATOR;
private final byte[] defaultEncodeTable;
private byte[] encodeTable;
/** Padding byte. */
private byte padding = PAD_DEFAULT;
AbstractBuilder(final byte[] defaultEncodeTable) {
this.defaultEncodeTable = defaultEncodeTable;
this.encodeTable = defaultEncodeTable;
}
@SuppressWarnings("unchecked")
B asThis() {
return (B) this;
}
CodecPolicy getDecodingPolicy() {
return decodingPolicy;
}
byte[] getEncodeTable() {
return encodeTable;
}
int getLineLength() {
return lineLength;
}
byte[] getLineSeparator() {
return lineSeparator;
}
byte getPadding() {
return padding;
}
/**
* Sets the decoding policy.
*
* @param decodingPolicy the decoding policy, null resets to the default.
* @return {@code this} instance.
*/
public B setDecodingPolicy(final CodecPolicy decodingPolicy) {
this.decodingPolicy = decodingPolicy != null ? decodingPolicy : DECODING_POLICY_DEFAULT;
return asThis();
}
/**
* Sets the encode table.
*
* @param encodeTable the encode table, null resets to the default.
* @return {@code this} instance.
*/
public B setEncodeTable(final byte... encodeTable) {
this.encodeTable = encodeTable != null ? encodeTable : defaultEncodeTable;
return asThis();
}
/**
* Sets the line length.
*
* @param lineLength the line length, less than 0 resets to the default.
* @return {@code this} instance.
*/
public B setLineLength(final int lineLength) {
this.lineLength = Math.max(0, lineLength);
return asThis();
}
/**
* Sets the line separator.
*
* @param lineSeparator the line separator, null resets to the default.
* @return {@code this} instance.
*/
public B setLineSeparator(final byte... lineSeparator) {
this.lineSeparator = lineSeparator != null ? lineSeparator : CHUNK_SEPARATOR;
return asThis();
}
/**
* Sets the padding byte.
*
* @param padding the padding byte.
* @return {@code this} instance.
*/
public B setPadding(final byte padding) {
this.padding = padding;
return asThis();
}
}
/**
* Holds thread context so classes can be thread-safe.
*
* This class is not itself thread-safe; each thread must allocate its own copy.
*/
static class Context {
/**
* Placeholder for the bytes we're dealing with for our based logic.
* Bitwise operations store and extract the encoding or decoding from this variable.
*/
int ibitWorkArea;
/**
* Placeholder for the bytes we're dealing with for our based logic.
* Bitwise operations store and extract the encoding or decoding from this variable.
*/
long lbitWorkArea;
/**
* Buffer for streaming.
*/
byte[] buffer;
/**
* Position where next character should be written in the buffer.
*/
int pos;
/**
* Position where next character should be read from the buffer.
*/
int readPos;
/**
* Boolean flag to indicate the EOF has been reached. Once EOF has been reached, this object becomes useless,
* and must be thrown away.
*/
boolean eof;
/**
* Variable tracks how many characters have been written to the current line. Only used when encoding. We use
* it to make sure each encoded line never goes beyond lineLength (if lineLength > 0).
*/
int currentLinePos;
/**
* Writes to the buffer only occur after every 3/5 reads when encoding, and every 4/8 reads when decoding. This
* variable helps track that.
*/
int modulus;
/**
* Returns a String useful for debugging (especially within a debugger.)
*
* @return a String useful for debugging.
*/
@Override
public String toString() {
return String.format("%s[buffer=%s, currentLinePos=%s, eof=%s, ibitWorkArea=%s, lbitWorkArea=%s, " +
"modulus=%s, pos=%s, readPos=%s]", this.getClass().getSimpleName(), Arrays.toString(buffer),
currentLinePos, eof, ibitWorkArea, lbitWorkArea, modulus, pos, readPos);
}
}
/**
* EOF
*
* @since 1.7
*/
static final int EOF = -1;
/**
* MIME chunk size per RFC 2045 section 6.8.
*
*
* The {@value} character limit does not count the trailing CRLF, but counts all other characters, including any
* equal signs.
*
*
* @see RFC 2045 section 6.8
*/
public static final int MIME_CHUNK_SIZE = 76;
/**
* PEM chunk size per RFC 1421 section 4.3.2.4.
*
*
* The {@value} character limit does not count the trailing CRLF, but counts all other characters, including any
* equal signs.
*
*
* @see RFC 1421 section 4.3.2.4
*/
public static final int PEM_CHUNK_SIZE = 64;
private static final int DEFAULT_BUFFER_RESIZE_FACTOR = 2;
/**
* Defines the default buffer size - currently {@value}
* - must be large enough for at least one encoded block+separator
*/
private static final int DEFAULT_BUFFER_SIZE = 8192;
/**
* The maximum size buffer to allocate.
*
* This is set to the same size used in the JDK {@link java.util.ArrayList}:
*
* Some VMs reserve some header words in an array.
* Attempts to allocate larger arrays may result in
* OutOfMemoryError: Requested array size exceeds VM limit.
*
*/
private static final int MAX_BUFFER_SIZE = Integer.MAX_VALUE - 8;
/** Mask used to extract 8 bits, used in decoding bytes */
protected static final int MASK_8BITS = 0xff;
/**
* Byte used to pad output.
*/
protected static final byte PAD_DEFAULT = '='; // Allow static access to default
/**
* The default decoding policy.
* @since 1.15
*/
protected static final CodecPolicy DECODING_POLICY_DEFAULT = CodecPolicy.LENIENT;
/**
* Chunk separator per RFC 2045 section 2.1.
*
* @see RFC 2045 section 2.1
*/
static final byte[] CHUNK_SEPARATOR = {'\r', '\n'};
/**
* Create a positive capacity at least as large the minimum required capacity.
* If the minimum capacity is negative then this throws an OutOfMemoryError as no array
* can be allocated.
*
* @param minCapacity the minimum capacity
* @return the capacity
* @throws OutOfMemoryError if the {@code minCapacity} is negative
*/
private static int createPositiveCapacity(final int minCapacity) {
if (minCapacity < 0) {
// overflow
throw new OutOfMemoryError("Unable to allocate array size: " + (minCapacity & 0xffffffffL));
}
// This is called when we require buffer expansion to a very big array.
// Use the conservative maximum buffer size if possible, otherwise the biggest required.
//
// Note: In this situation JDK 1.8 java.util.ArrayList returns Integer.MAX_VALUE.
// This excludes some VMs that can exceed MAX_BUFFER_SIZE but not allocate a full
// Integer.MAX_VALUE length array.
// The result is that we may have to allocate an array of this size more than once if
// the capacity must be expanded again.
return Math.max(minCapacity, MAX_BUFFER_SIZE);
}
/**
* Gets a copy of the chunk separator per RFC 2045 section 2.1.
*
* @return the chunk separator
* @see RFC 2045 section 2.1
* @since 1.15
*/
public static byte[] getChunkSeparator() {
return CHUNK_SEPARATOR.clone();
}
/**
* Checks if a byte value is whitespace or not.
* @param byteToCheck
* the byte to check
* @return true if byte is whitespace, false otherwise
* @see Character#isWhitespace(int)
* @deprecated Use {@link Character#isWhitespace(int)}.
*/
@Deprecated
protected static boolean isWhiteSpace(final byte byteToCheck) {
return Character.isWhitespace(byteToCheck);
}
/**
* Increases our buffer by the {@link #DEFAULT_BUFFER_RESIZE_FACTOR}.
* @param context the context to be used
* @param minCapacity the minimum required capacity
* @return the resized byte[] buffer
* @throws OutOfMemoryError if the {@code minCapacity} is negative
*/
private static byte[] resizeBuffer(final Context context, final int minCapacity) {
// Overflow-conscious code treats the min and new capacity as unsigned.
final int oldCapacity = context.buffer.length;
int newCapacity = oldCapacity * DEFAULT_BUFFER_RESIZE_FACTOR;
if (Integer.compareUnsigned(newCapacity, minCapacity) < 0) {
newCapacity = minCapacity;
}
if (Integer.compareUnsigned(newCapacity, MAX_BUFFER_SIZE) > 0) {
newCapacity = createPositiveCapacity(minCapacity);
}
final byte[] b = Arrays.copyOf(context.buffer, newCapacity);
context.buffer = b;
return b;
}
/**
* Gets the array length or 0 if null.
*
* @param array the array or null.
* @return the array length or 0 if null.
*/
static int toLength(final byte[] array) {
return array == null ? 0 : array.length;
}
/**
* @deprecated Use {@link #pad}. Will be removed in 2.0.
*/
@Deprecated
protected final byte PAD = PAD_DEFAULT; // instance variable just in case it needs to vary later
/** Pad byte. Instance variable just in case it needs to vary later. */
protected final byte pad;
/** Number of bytes in each full block of unencoded data, e.g. 4 for Base64 and 5 for Base32 */
private final int unencodedBlockSize;
/** Number of bytes in each full block of encoded data, e.g. 3 for Base64 and 8 for Base32 */
private final int encodedBlockSize;
/**
* Chunksize for encoding. Not used when decoding.
* A value of zero or less implies no chunking of the encoded data.
* Rounded down to the nearest multiple of encodedBlockSize.
*/
protected final int lineLength;
/**
* Size of chunk separator. Not used unless {@link #lineLength} > 0.
*/
private final int chunkSeparatorLength;
/**
* Defines the decoding behavior when the input bytes contain leftover trailing bits that
* cannot be created by a valid encoding. These can be bits that are unused from the final
* character or entire characters. The default mode is lenient decoding. Set this to
* {@code true} to enable strict decoding.
*
* - Lenient: Any trailing bits are composed into 8-bit bytes where possible.
* The remainder are discarded.
*
- Strict: The decoding will raise an {@link IllegalArgumentException} if trailing bits
* are not part of a valid encoding. Any unused bits from the final character must
* be zero. Impossible counts of entire final characters are not allowed.
*
*
* When strict decoding is enabled it is expected that the decoded bytes will be re-encoded
* to a byte array that matches the original, i.e. no changes occur on the final
* character. This requires that the input bytes use the same padding and alphabet
* as the encoder.
*
*/
private final CodecPolicy decodingPolicy;
/**
* Constructs a new instance.
*
* Note {@code lineLength} is rounded down to the nearest multiple of the encoded block size.
* If {@code chunkSeparatorLength} is zero, then chunking is disabled.
*
*
* @param unencodedBlockSize the size of an unencoded block (e.g. Base64 = 3)
* @param encodedBlockSize the size of an encoded block (e.g. Base64 = 4)
* @param lineLength if > 0, use chunking with a length {@code lineLength}
* @param chunkSeparatorLength the chunk separator length, if relevant
*/
protected BaseNCodec(final int unencodedBlockSize, final int encodedBlockSize, final int lineLength, final int chunkSeparatorLength) {
this(unencodedBlockSize, encodedBlockSize, lineLength, chunkSeparatorLength, PAD_DEFAULT);
}
/**
* Constructs a new instance.
*
* Note {@code lineLength} is rounded down to the nearest multiple of the encoded block size.
* If {@code chunkSeparatorLength} is zero, then chunking is disabled.
*
*
* @param unencodedBlockSize the size of an unencoded block (e.g. Base64 = 3)
* @param encodedBlockSize the size of an encoded block (e.g. Base64 = 4)
* @param lineLength if > 0, use chunking with a length {@code lineLength}
* @param chunkSeparatorLength the chunk separator length, if relevant
* @param pad byte used as padding byte.
*/
protected BaseNCodec(final int unencodedBlockSize, final int encodedBlockSize, final int lineLength, final int chunkSeparatorLength, final byte pad) {
this(unencodedBlockSize, encodedBlockSize, lineLength, chunkSeparatorLength, pad, DECODING_POLICY_DEFAULT);
}
/**
* Constructs a new instance.
*
* Note {@code lineLength} is rounded down to the nearest multiple of the encoded block size.
* If {@code chunkSeparatorLength} is zero, then chunking is disabled.
*
*
* @param unencodedBlockSize the size of an unencoded block (e.g. Base64 = 3)
* @param encodedBlockSize the size of an encoded block (e.g. Base64 = 4)
* @param lineLength if > 0, use chunking with a length {@code lineLength}
* @param chunkSeparatorLength the chunk separator length, if relevant
* @param pad byte used as padding byte.
* @param decodingPolicy Decoding policy.
* @since 1.15
*/
protected BaseNCodec(final int unencodedBlockSize, final int encodedBlockSize, final int lineLength, final int chunkSeparatorLength, final byte pad,
final CodecPolicy decodingPolicy) {
this.unencodedBlockSize = unencodedBlockSize;
this.encodedBlockSize = encodedBlockSize;
final boolean useChunking = lineLength > 0 && chunkSeparatorLength > 0;
this.lineLength = useChunking ? lineLength / encodedBlockSize * encodedBlockSize : 0;
this.chunkSeparatorLength = chunkSeparatorLength;
this.pad = pad;
this.decodingPolicy = Objects.requireNonNull(decodingPolicy, "codecPolicy");
}
/**
* Returns the amount of buffered data available for reading.
*
* @param context the context to be used
* @return The amount of buffered data available for reading.
*/
int available(final Context context) { // package protected for access from I/O streams
return hasData(context) ? context.pos - context.readPos : 0;
}
/**
* Tests a given byte array to see if it contains any characters within the alphabet or PAD.
*
* Intended for use in checking line-ending arrays
*
* @param arrayOctet
* byte array to test
* @return {@code true} if any byte is a valid character in the alphabet or PAD; {@code false} otherwise
*/
protected boolean containsAlphabetOrPad(final byte[] arrayOctet) {
if (arrayOctet != null) {
for (final byte element : arrayOctet) {
if (pad == element || isInAlphabet(element)) {
return true;
}
}
}
return false;
}
/**
* Decodes a byte[] containing characters in the Base-N alphabet.
*
* @param pArray
* A byte array containing Base-N character data
* @return a byte array containing binary data
*/
@Override
public byte[] decode(final byte[] pArray) {
if (BinaryCodec.isEmpty(pArray)) {
return pArray;
}
final Context context = new Context();
decode(pArray, 0, pArray.length, context);
decode(pArray, 0, EOF, context); // Notify decoder of EOF.
final byte[] result = new byte[context.pos];
readResults(result, 0, result.length, context);
return result;
}
// package protected for access from I/O streams
abstract void decode(byte[] pArray, int i, int length, Context context);
/**
* Decodes an Object using the Base-N algorithm. This method is provided in order to satisfy the requirements of
* the Decoder interface, and will throw a DecoderException if the supplied object is not of type byte[] or String.
*
* @param obj
* Object to decode
* @return An object (of type byte[]) containing the binary data which corresponds to the byte[] or String
* supplied.
* @throws DecoderException
* if the parameter supplied is not of type byte[]
*/
@Override
public Object decode(final Object obj) throws DecoderException {
if (obj instanceof byte[]) {
return decode((byte[]) obj);
}
if (obj instanceof String) {
return decode((String) obj);
}
throw new DecoderException("Parameter supplied to Base-N decode is not a byte[] or a String");
}
/**
* Decodes a String containing characters in the Base-N alphabet.
*
* @param pArray
* A String containing Base-N character data
* @return a byte array containing binary data
*/
public byte[] decode(final String pArray) {
return decode(StringUtils.getBytesUtf8(pArray));
}
/**
* Encodes a byte[] containing binary data, into a byte[] containing characters in the alphabet.
*
* @param pArray
* a byte array containing binary data
* @return A byte array containing only the base N alphabetic character data
*/
@Override
public byte[] encode(final byte[] pArray) {
if (BinaryCodec.isEmpty(pArray)) {
return pArray;
}
return encode(pArray, 0, pArray.length);
}
/**
* Encodes a byte[] containing binary data, into a byte[] containing
* characters in the alphabet.
*
* @param pArray
* a byte array containing binary data
* @param offset
* initial offset of the subarray.
* @param length
* length of the subarray.
* @return A byte array containing only the base N alphabetic character data
* @since 1.11
*/
public byte[] encode(final byte[] pArray, final int offset, final int length) {
if (BinaryCodec.isEmpty(pArray)) {
return pArray;
}
final Context context = new Context();
encode(pArray, offset, length, context);
encode(pArray, offset, EOF, context); // Notify encoder of EOF.
final byte[] buf = new byte[context.pos - context.readPos];
readResults(buf, 0, buf.length, context);
return buf;
}
// package protected for access from I/O streams
abstract void encode(byte[] pArray, int i, int length, Context context);
/**
* Encodes an Object using the Base-N algorithm. This method is provided in order to satisfy the requirements of
* the Encoder interface, and will throw an EncoderException if the supplied object is not of type byte[].
*
* @param obj
* Object to encode
* @return An object (of type byte[]) containing the Base-N encoded data which corresponds to the byte[] supplied.
* @throws EncoderException
* if the parameter supplied is not of type byte[]
*/
@Override
public Object encode(final Object obj) throws EncoderException {
if (!(obj instanceof byte[])) {
throw new EncoderException("Parameter supplied to Base-N encode is not a byte[]");
}
return encode((byte[]) obj);
}
/**
* Encodes a byte[] containing binary data, into a String containing characters in the appropriate alphabet.
* Uses UTF8 encoding.
*
* This is a duplicate of {@link #encodeToString(byte[])}; it was merged during refactoring.
*
*
* @param pArray a byte array containing binary data
* @return String containing only character data in the appropriate alphabet.
* @since 1.5
*/
public String encodeAsString(final byte[] pArray) {
return StringUtils.newStringUtf8(encode(pArray));
}
/**
* Encodes a byte[] containing binary data, into a String containing characters in the Base-N alphabet.
* Uses UTF8 encoding.
*
* @param pArray
* a byte array containing binary data
* @return A String containing only Base-N character data
*/
public String encodeToString(final byte[] pArray) {
return StringUtils.newStringUtf8(encode(pArray));
}
/**
* Ensure that the buffer has room for {@code size} bytes
*
* @param size minimum spare space required
* @param context the context to be used
* @return the buffer
*/
protected byte[] ensureBufferSize(final int size, final Context context) {
if (context.buffer == null) {
context.buffer = new byte[Math.max(size, getDefaultBufferSize())];
context.pos = 0;
context.readPos = 0;
// Overflow-conscious:
// x + y > z == x + y - z > 0
} else if (context.pos + size - context.buffer.length > 0) {
return resizeBuffer(context, context.pos + size);
}
return context.buffer;
}
/**
* Returns the decoding behavior policy.
*
*
* The default is lenient. If the decoding policy is strict, then decoding will raise an
* {@link IllegalArgumentException} if trailing bits are not part of a valid encoding. Decoding will compose
* trailing bits into 8-bit bytes and discard the remainder.
*
*
* @return true if using strict decoding
* @since 1.15
*/
public CodecPolicy getCodecPolicy() {
return decodingPolicy;
}
/**
* Gets the default buffer size. Can be overridden.
*
* @return the default buffer size.
*/
protected int getDefaultBufferSize() {
return DEFAULT_BUFFER_SIZE;
}
/**
* Calculates the amount of space needed to encode the supplied array.
*
* @param pArray byte[] array which will later be encoded
*
* @return amount of space needed to encode the supplied array.
* Returns a long since a max-len array will require > Integer.MAX_VALUE
*/
public long getEncodedLength(final byte[] pArray) {
// Calculate non-chunked size - rounded up to allow for padding
// cast to long is needed to avoid possibility of overflow
long len = (pArray.length + unencodedBlockSize - 1) / unencodedBlockSize * (long) encodedBlockSize;
if (lineLength > 0) { // We're using chunking
// Round up to nearest multiple
len += (len + lineLength - 1) / lineLength * chunkSeparatorLength;
}
return len;
}
/**
* Returns true if this object has buffered data for reading.
*
* @param context the context to be used
* @return true if there is data still available for reading.
*/
boolean hasData(final Context context) { // package protected for access from I/O streams
return context.pos > context.readPos;
}
/**
* Returns whether or not the {@code octet} is in the current alphabet.
* Does not allow whitespace or pad.
*
* @param value The value to test
*
* @return {@code true} if the value is defined in the current alphabet, {@code false} otherwise.
*/
protected abstract boolean isInAlphabet(byte value);
/**
* Tests a given byte array to see if it contains only valid characters within the alphabet.
* The method optionally treats whitespace and pad as valid.
*
* @param arrayOctet byte array to test
* @param allowWSPad if {@code true}, then whitespace and PAD are also allowed
*
* @return {@code true} if all bytes are valid characters in the alphabet or if the byte array is empty;
* {@code false}, otherwise
*/
public boolean isInAlphabet(final byte[] arrayOctet, final boolean allowWSPad) {
for (final byte octet : arrayOctet) {
if (!isInAlphabet(octet) && (!allowWSPad || octet != pad && !Character.isWhitespace(octet))) {
return false;
}
}
return true;
}
/**
* Tests a given String to see if it contains only valid characters within the alphabet.
* The method treats whitespace and PAD as valid.
*
* @param basen String to test
* @return {@code true} if all characters in the String are valid characters in the alphabet or if
* the String is empty; {@code false}, otherwise
* @see #isInAlphabet(byte[], boolean)
*/
public boolean isInAlphabet(final String basen) {
return isInAlphabet(StringUtils.getBytesUtf8(basen), true);
}
/**
* Returns true if decoding behavior is strict. Decoding will raise an {@link IllegalArgumentException} if trailing
* bits are not part of a valid encoding.
*
*
* The default is false for lenient decoding. Decoding will compose trailing bits into 8-bit bytes and discard the
* remainder.
*
*
* @return true if using strict decoding
* @since 1.15
*/
public boolean isStrictDecoding() {
return decodingPolicy == CodecPolicy.STRICT;
}
/**
* Extracts buffered data into the provided byte[] array, starting at position bPos, up to a maximum of bAvail
* bytes. Returns how many bytes were actually extracted.
*
* Package private for access from I/O streams.
*
*
* @param b
* byte[] array to extract the buffered data into.
* @param bPos
* position in byte[] array to start extraction at.
* @param bAvail
* amount of bytes we're allowed to extract. We may extract fewer (if fewer are available).
* @param context
* the context to be used
* @return The number of bytes successfully extracted into the provided byte[] array.
*/
int readResults(final byte[] b, final int bPos, final int bAvail, final Context context) {
if (hasData(context)) {
final int len = Math.min(available(context), bAvail);
System.arraycopy(context.buffer, context.readPos, b, bPos, len);
context.readPos += len;
if (!hasData(context)) {
// All data read.
// Reset position markers but do not set buffer to null to allow its reuse.
// hasData(context) will still return false, and this method will return 0 until
// more data is available, or -1 if EOF.
context.pos = context.readPos = 0;
}
return len;
}
return context.eof ? EOF : 0;
}
}
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