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A more efficient encoding for short strings, raws, lists and maps. Now we can encode a list of three small integers in 4 bytes like MessagePack does, should that ever turn out to be useful.

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This commit is contained in:
akwizgran
2011-07-18 16:06:09 +01:00
parent 0bc8a31749
commit 7a4171f3ba
4 changed files with 293 additions and 118 deletions
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127
components/net/sf/briar/serial/ReaderImpl.java
View File

@@ -15,6 +15,8 @@ import net.sf.briar.api.serial.Tag;
class ReaderImpl implements Reader {
private static final byte[] EMPTY_BUFFER = new byte[] {};
private final InputStream in;
private Consumer[] consumers = new Consumer[] {};
private boolean started = false, eof = false;
@@ -143,18 +145,21 @@ class ReaderImpl implements Reader {
}
private void readIntoBuffer(int length) throws IOException {
assert length > 0;
if(buf == null || buf.length < length) buf = new byte[length];
buf[0] = next;
readIntoBuffer(buf, length);
}
private void readIntoBuffer(byte[] b, int length) throws IOException {
b[0] = next;
int offset = 1;
while(offset < length) {
int read = in.read(buf, offset, length - offset);
int read = in.read(b, offset, length - offset);
if(read == -1) break;
offset += read;
}
if(offset < length) throw new FormatException();
// Feed the hungry mouths
for(Consumer c : consumers) c.write(buf, 0, length);
for(Consumer c : consumers) c.write(b, 0, length);
// Read the lookahead byte
int i = in.read();
if(i == -1) eof = true;
@@ -226,24 +231,27 @@ class ReaderImpl implements Reader {
public boolean hasString() throws IOException {
if(!started) readNext(true);
if(eof) return false;
return next == Tag.STRING;
return next == Tag.STRING
|| (next & Tag.SHORT_MASK) == Tag.SHORT_STRING;
}
public String readString() throws IOException {
if(!hasString()) throw new FormatException();
readNext(false);
int length = readLength();
if(length == 0) return "";
checkLimit(length);
readIntoBuffer(length);
return new String(buf, 0, length, "UTF-8");
if(next == Tag.STRING) {
readNext(false);
return readString(readLength());
} else {
int length = 0xFF & next ^ Tag.SHORT_STRING;
readNext(length == 0);
return readString(length);
}
}
private boolean hasLength() throws IOException {
if(!started) readNext(true);
if(eof) return false;
return next >= 0 || next == Tag.INT8 || next == Tag.INT16
|| next == Tag.INT32;
private String readString(int length) throws IOException {
assert length >= 0;
if(length == 0) return "";
readIntoBuffer(length);
return new String(buf, 0, length, "UTF-8");
}
private int readLength() throws IOException {
@@ -255,32 +263,44 @@ class ReaderImpl implements Reader {
throw new IllegalStateException();
}
private void checkLimit(long bytes) throws FormatException {
// FIXME
private boolean hasLength() throws IOException {
if(!started) readNext(true);
if(eof) return false;
return next >= 0 || next == Tag.INT8 || next == Tag.INT16
|| next == Tag.INT32;
}
public boolean hasRaw() throws IOException {
if(!started) readNext(true);
if(eof) return false;
return next == Tag.RAW;
return next == Tag.RAW || (next & Tag.SHORT_MASK) == Tag.SHORT_RAW;
}
public byte[] readRaw() throws IOException {
if(!hasRaw()) throw new FormatException();
readNext(false);
int length = readLength();
if(length == 0) return new byte[] {};
checkLimit(length);
readIntoBuffer(length);
byte[] b = buf;
buf = null;
if(next == Tag.RAW) {
readNext(false);
return readRaw(readLength());
} else {
int length = 0xFF & next ^ Tag.SHORT_RAW;
readNext(length == 0);
return readRaw(length);
}
}
private byte[] readRaw(int length) throws IOException {
assert length >= 0;
if(length == 0) return EMPTY_BUFFER;
byte[] b = new byte[length];
readIntoBuffer(b, length);
return b;
}
public boolean hasList() throws IOException {
if(!started) readNext(true);
if(eof) return false;
return next == Tag.LIST || next == Tag.LIST_START;
return next == Tag.LIST || next == Tag.LIST_START
|| (next & Tag.SHORT_MASK) == Tag.SHORT_LIST;
}
public List<Object> readList() throws IOException {
@@ -289,16 +309,26 @@ class ReaderImpl implements Reader {
public <E> List<E> readList(Class<E> e) throws IOException {
if(!hasList()) throw new FormatException();
boolean definite = next == Tag.LIST;
readNext(false);
List<E> list = new ArrayList<E>();
if(definite) {
int length = readLength();
for(int i = 0; i < length; i++) list.add(readObject(e));
} else {
if(next == Tag.LIST) {
readNext(false);
return readList(e, readLength());
} else if(next == Tag.LIST_START) {
readNext(false);
List<E> list = new ArrayList<E>();
while(!hasEnd()) list.add(readObject(e));
readEnd();
return list;
} else {
int length = 0xFF & next ^ Tag.SHORT_LIST;
readNext(length == 0);
return readList(e, length);
}
}
private <E> List<E> readList(Class<E> e, int length) throws IOException {
assert length >= 0;
List<E> list = new ArrayList<E>();
for(int i = 0; i < length; i++) list.add(readObject(e));
return list;
}
@@ -315,7 +345,6 @@ class ReaderImpl implements Reader {
}
private Object readObject() throws IOException {
// FIXME: Use a switch statement
if(!started) throw new IllegalStateException();
if(hasBoolean()) return Boolean.valueOf(readBoolean());
if(hasUint7()) return Byte.valueOf(readUint7());
@@ -367,7 +396,8 @@ class ReaderImpl implements Reader {
public boolean hasMap() throws IOException {
if(!started) readNext(true);
if(eof) return false;
return next == Tag.MAP || next == Tag.MAP_START;
return next == Tag.MAP || next == Tag.MAP_START
|| (next & Tag.SHORT_MASK) == Tag.SHORT_MAP;
}
public Map<Object, Object> readMap() throws IOException {
@@ -376,16 +406,27 @@ class ReaderImpl implements Reader {
public <K, V> Map<K, V> readMap(Class<K> k, Class<V> v) throws IOException {
if(!hasMap()) throw new FormatException();
boolean definite = next == Tag.MAP;
readNext(false);
Map<K, V> m = new HashMap<K, V>();
if(definite) {
int length = readLength();
for(int i = 0; i < length; i++) m.put(readObject(k), readObject(v));
} else {
if(next == Tag.MAP) {
readNext(false);
return readMap(k, v, readLength());
} else if(next == Tag.MAP_START) {
readNext(false);
Map<K, V> m = new HashMap<K, V>();
while(!hasEnd()) m.put(readObject(k), readObject(v));
readEnd();
return m;
} else {
int size = 0xFF & next ^ Tag.SHORT_MAP;
readNext(size == 0);
return readMap(k, v, size);
}
}
private <K, V> Map<K, V> readMap(Class<K> k, Class<V> v, int size)
throws IOException {
assert size >= 0;
Map<K, V> m = new HashMap<K, V>();
for(int i = 0; i < size; i++) m.put(readObject(k), readObject(v));
return m;
}

50
components/net/sf/briar/serial/WriterImpl.java
View File

@@ -108,16 +108,38 @@ class WriterImpl implements Writer {
}
public void writeString(String s) throws IOException {
out.write(Tag.STRING);
byte[] b = s.getBytes("UTF-8");
writeIntAny(b.length);
if(b.length < 16) out.write(intToByte(Tag.SHORT_STRING | b.length));
else {
out.write(Tag.STRING);
writeLength(b.length);
}
out.write(b);
bytesWritten += b.length + 1;
}
private byte intToByte(int i) {
assert i >= 0;
assert i <= 255;
return (byte) (i > 127 ? i - 256 : i);
}
private void writeLength(int i) throws IOException {
if(i >= 0 && i <= Byte.MAX_VALUE)
writeUint7((byte) i);
else if(i >= Byte.MIN_VALUE && i <= Byte.MAX_VALUE)
writeInt8((byte) i);
else if(i >= Short.MIN_VALUE && i <= Short.MAX_VALUE)
writeInt16((short) i);
else writeInt32(i);
}
public void writeRaw(byte[] b) throws IOException {
out.write(Tag.RAW);
writeIntAny(b.length);
if(b.length < 16) out.write(intToByte(Tag.SHORT_RAW | b.length));
else {
out.write(Tag.RAW);
writeLength(b.length);
}
out.write(b);
bytesWritten += b.length + 1;
}
@@ -127,10 +149,14 @@ class WriterImpl implements Writer {
}
public void writeList(List<?> l) throws IOException {
out.write(Tag.LIST);
bytesWritten++;
writeIntAny(l.size());
int length = l.size();
if(length < 16) out.write(intToByte(Tag.SHORT_LIST | length));
else {
out.write(Tag.LIST);
writeLength(length);
}
for(Object o : l) writeObject(o);
bytesWritten++;
}
private void writeObject(Object o) throws IOException {
@@ -160,13 +186,17 @@ class WriterImpl implements Writer {
}
public void writeMap(Map<?, ?> m) throws IOException {
out.write(Tag.MAP);
bytesWritten++;
writeIntAny(m.size());
int length = m.size();
if(length < 16) out.write(intToByte(Tag.SHORT_MAP | length));
else {
out.write(Tag.MAP);
writeLength(length);
}
for(Entry<?, ?> e : m.entrySet()) {
writeObject(e.getKey());
writeObject(e.getValue());
}
bytesWritten++;
}
public void writeMapStart() throws IOException {