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Core Jackson abstractions, basic JSON streaming API implementation
package com.fasterxml.jackson.core.io;
import java.io.*;
/**
* Since JDK does not come with UTF-32/UCS-4, let's implement a simple
* decoder to use.
*/
public class UTF32Reader extends Reader
{
/**
* JSON actually limits available Unicode range in the high end
* to the same as xml (to basically limit UTF-8 max byte sequence
* length to 4)
*/
final protected static int LAST_VALID_UNICODE_CHAR = 0x10FFFF;
final protected static char NC = (char) 0;
final protected IOContext _context;
protected InputStream _in;
protected byte[] _buffer;
protected int _ptr;
protected int _length;
protected final boolean _bigEndian;
/**
* Although input is fine with full Unicode set, Java still uses
* 16-bit chars, so we may have to split high-order chars into
* surrogate pairs.
*/
protected char _surrogate = NC;
/**
* Total read character count; used for error reporting purposes
*/
protected int _charCount = 0;
/**
* Total read byte count; used for error reporting purposes
*/
protected int _byteCount = 0;
protected final boolean _managedBuffers;
/*
/**********************************************************
/* Life-cycle
/**********************************************************
*/
public UTF32Reader(IOContext ctxt, InputStream in, byte[] buf, int ptr, int len, boolean isBigEndian) {
_context = ctxt;
_in = in;
_buffer = buf;
_ptr = ptr;
_length = len;
_bigEndian = isBigEndian;
_managedBuffers = (in != null);
}
/*
/**********************************************************
/* Public API
/**********************************************************
*/
@Override
public void close() throws IOException {
InputStream in = _in;
if (in != null) {
_in = null;
freeBuffers();
in.close();
}
}
protected char[] _tmpBuf = null;
/**
* Although this method is implemented by the base class, AND it should
* never be called by main code, let's still implement it bit more
* efficiently just in case
*/
@Override
public int read() throws IOException {
if (_tmpBuf == null) {
_tmpBuf = new char[1];
}
if (read(_tmpBuf, 0, 1) < 1) {
return -1;
}
return _tmpBuf[0];
}
@Override
public int read(char[] cbuf, int start, int len) throws IOException {
// Already EOF?
if (_buffer == null) { return -1; }
if (len < 1) { return len; }
// Let's then ensure there's enough room...
if (start < 0 || (start+len) > cbuf.length) {
reportBounds(cbuf, start, len);
}
len += start;
int outPtr = start;
// Ok, first; do we have a surrogate from last round?
if (_surrogate != NC) {
cbuf[outPtr++] = _surrogate;
_surrogate = NC;
// No need to load more, already got one char
} else {
/* Note: we'll try to avoid blocking as much as possible. As a
* result, we only need to get 4 bytes for a full char.
*/
int left = (_length - _ptr);
if (left < 4) {
if (!loadMore(left)) { // (legal) EOF?
return -1;
}
}
}
main_loop:
while (outPtr < len) {
int ptr = _ptr;
int ch;
if (_bigEndian) {
ch = (_buffer[ptr] << 24) | ((_buffer[ptr+1] & 0xFF) << 16)
| ((_buffer[ptr+2] & 0xFF) << 8) | (_buffer[ptr+3] & 0xFF);
} else {
ch = (_buffer[ptr] & 0xFF) | ((_buffer[ptr+1] & 0xFF) << 8)
| ((_buffer[ptr+2] & 0xFF) << 16) | (_buffer[ptr+3] << 24);
}
_ptr += 4;
// Does it need to be split to surrogates?
// (also, we can and need to verify illegal chars)
if (ch > 0xFFFF) { // need to split into surrogates?
if (ch > LAST_VALID_UNICODE_CHAR) {
reportInvalid(ch, outPtr-start,
"(above "+Integer.toHexString(LAST_VALID_UNICODE_CHAR)+") ");
}
ch -= 0x10000; // to normalize it starting with 0x0
cbuf[outPtr++] = (char) (0xD800 + (ch >> 10));
// hmmh. can this ever be 0? (not legal, at least?)
ch = (0xDC00 | (ch & 0x03FF));
// Room for second part?
if (outPtr >= len) { // nope
_surrogate = (char) ch;
break main_loop;
}
}
cbuf[outPtr++] = (char) ch;
if (_ptr >= _length) {
break main_loop;
}
}
len = outPtr - start;
_charCount += len;
return len;
}
/*
/**********************************************************
/* Internal methods
/**********************************************************
*/
private void reportUnexpectedEOF(int gotBytes, int needed) throws IOException {
int bytePos = _byteCount + gotBytes, charPos = _charCount;
throw new CharConversionException("Unexpected EOF in the middle of a 4-byte UTF-32 char: got "+gotBytes+", needed "+needed+", at char #"+charPos+", byte #"+bytePos+")");
}
private void reportInvalid(int value, int offset, String msg) throws IOException {
int bytePos = _byteCount + _ptr - 1, charPos = _charCount + offset;
throw new CharConversionException("Invalid UTF-32 character 0x"+Integer.toHexString(value)+msg+" at char #"+charPos+", byte #"+bytePos+")");
}
/**
* @param available Number of "unused" bytes in the input buffer
*
* @return True, if enough bytes were read to allow decoding of at least
* one full character; false if EOF was encountered instead.
*/
private boolean loadMore(int available) throws IOException {
_byteCount += (_length - available);
// Bytes that need to be moved to the beginning of buffer?
if (available > 0) {
if (_ptr > 0) {
System.arraycopy(_buffer, _ptr, _buffer, 0, available);
_ptr = 0;
}
_length = available;
} else {
/* Ok; here we can actually reasonably expect an EOF,
* so let's do a separate read right away:
*/
_ptr = 0;
int count = (_in == null) ? -1 : _in.read(_buffer);
if (count < 1) {
_length = 0;
if (count < 0) { // -1
if (_managedBuffers) {
freeBuffers(); // to help GC?
}
return false;
}
// 0 count is no good; let's err out
reportStrangeStream();
}
_length = count;
}
/* Need at least 4 bytes; if we don't get that many, it's an
* error.
*/
while (_length < 4) {
int count = (_in == null) ? -1 : _in.read(_buffer, _length, _buffer.length - _length);
if (count < 1) {
if (count < 0) { // -1, EOF... no good!
if (_managedBuffers) {
freeBuffers(); // to help GC?
}
reportUnexpectedEOF(_length, 4);
}
// 0 count is no good; let's err out
reportStrangeStream();
}
_length += count;
}
return true;
}
/**
* This method should be called along with (or instead of) normal
* close. After calling this method, no further reads should be tried.
* Method will try to recycle read buffers (if any).
*/
private void freeBuffers() {
byte[] buf = _buffer;
if (buf != null) {
_buffer = null;
_context.releaseReadIOBuffer(buf);
}
}
private void reportBounds(char[] cbuf, int start, int len) throws IOException {
throw new ArrayIndexOutOfBoundsException("read(buf,"+start+","+len+"), cbuf["+cbuf.length+"]");
}
private void reportStrangeStream() throws IOException {
throw new IOException("Strange I/O stream, returned 0 bytes on read");
}
}