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// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.slime;
import com.yahoo.text.Text;
import java.nio.ByteBuffer;
import java.nio.charset.StandardCharsets;
/**
* A port of the C++ json decoder intended to be fast.
*
* @author Ulf Lilleengen
*/
public class JsonDecoder {
private BufferedInput in;
private byte c;
private final SlimeInserter slimeInserter = new SlimeInserter(null);
private final ArrayInserter arrayInserter = new ArrayInserter(null);
private final ObjectInserter objectInserter = new ObjectInserter(null, null);
private final BufferedOutput buf = new BufferedOutput();
private static final byte[] TRUE = {'t', 'r', 'u', 'e'};
private static final byte[] FALSE = {'f', 'a', 'l', 's', 'e'};
private static final byte[] NULL = {'n', 'u', 'l', 'l'};
private static final byte [] SQUARE_BRACKET_OPEN = { '[' };
private static final byte [] SQUARE_BRACKET_CLOSE = { ']' };
private static final byte [] CURLY_BRACE_OPEN = { '{' };
private static final byte [] CURLY_BRACE_CLOSE = { '}' };
private static final byte [] COLON = { ':' };
private static final byte COMMA = ',';
public JsonDecoder() {}
public Slime decode(Slime slime, byte[] bytes) {
return decode(slime, ByteBuffer.wrap(bytes));
}
public Slime decode(Slime slime, ByteBuffer buf) {
in = new BufferedInput(buf.array(), buf.arrayOffset()+buf.position(), buf.remaining());
next();
decodeValue(slimeInserter.adjust(slime));
if (in.failed()) {
slime.wrap("partial_result");
slime.get().setData("offending_input", in.getOffending());
slime.get().setString("error_message", in.getErrorMessage());
}
return slime;
}
/** Decode bytes as a UTF-8 JSON into Slime, or throw {@link JsonParseException} on invalid JSON. */
public Slime decodeOrThrow(Slime slime, byte[] bytes) {
in = new BufferedInput(bytes);
next();
decodeValue(slimeInserter.adjust(slime));
if (in.failed()) {
throw new JsonParseException(in);
}
return slime;
}
private void decodeValue(Inserter inserter) {
skipWhiteSpace();
switch (c) {
case '"': case '\'': decodeString(inserter); return;
case '{': decodeObject(inserter); return;
case '[': decodeArray(inserter); return;
case 't': expect(TRUE); inserter.insertBOOL(true); return;
case 'f': expect(FALSE); inserter.insertBOOL(false); return;
case 'n': expect(NULL); inserter.insertNIX(); return;
case '-': case '0': case '1': case '2': case '3': case '4': case '5':
case '6': case '7': case '8': case '9': decodeNumber(inserter); return;
}
in.fail("Expected start of value but got " + characterToReadableString(c));
}
@SuppressWarnings("fallthrough")
private void decodeNumber(Inserter inserter) {
buf.reset();
boolean likelyFloatingPoint = false;
for (;;) {
switch (c) {
case '.': case 'e': case 'E':
likelyFloatingPoint = true;
case '0': case '1': case '2': case '3': case '4':
case '5': case '6': case '7': case '8': case '9':
case '+': case '-':
buf.put(c);
next();
break;
default:
if (likelyFloatingPoint) {
double num = Double.parseDouble(buf.toString(StandardCharsets.UTF_8));
inserter.insertDOUBLE(num);
} else {
long num = Long.parseLong(buf.toString(StandardCharsets.UTF_8));
inserter.insertLONG(num);
}
return;
}
}
}
private void expect(byte[] expected) {
for (byte b : expected) {
if ( ! skip(b)) {
in.fail("Unexpected " + characterToReadableString(c));
return;
}
}
}
private void decodeArray(Inserter inserter) {
Cursor cursor = inserter.insertARRAY();
expect(SQUARE_BRACKET_OPEN);
skipWhiteSpace();
if (c != ']') {
do {
arrayInserter.adjust(cursor);
decodeValue(arrayInserter);
skipWhiteSpace();
} while (skip(COMMA));
}
expect(SQUARE_BRACKET_CLOSE);
}
private void decodeObject(Inserter inserter) {
Cursor cursor = inserter.insertOBJECT();
expect(CURLY_BRACE_OPEN);
skipWhiteSpace();
if (c != '}') {
do {
skipWhiteSpace();
String key = readKey();
skipWhiteSpace();
expect(COLON);
objectInserter.adjust(cursor, key);
decodeValue(objectInserter);
skipWhiteSpace();
} while (skip(COMMA));
}
expect(CURLY_BRACE_CLOSE);
}
private String readKey() {
buf.reset();
switch (c) {
case '"': case '\'': return readString();
default:
for (;;) {
switch (c) {
case ':': case ' ': case '\t': case '\n': case '\r': case '\0': return buf.toString(StandardCharsets.UTF_8);
default:
buf.put(c);
next();
break;
}
}
}
}
private void decodeString(Inserter inserter) {
String value = readString();
inserter.insertSTRING(value);
}
private String readString() {
buf.reset();
byte quote = c;
assert(quote == '"' || quote == '\'');
next();
for (;;) {
switch (c) {
case '\\':
next();
switch (c) {
case '"': case '\\': case '/': case '\'':
buf.put(c);
break;
case 'b': buf.put((byte) '\b'); break;
case 'f': buf.put((byte) '\f'); break;
case 'n': buf.put((byte) '\n'); break;
case 'r': buf.put((byte) '\r'); break;
case 't': buf.put((byte) '\t'); break;
case 'u': writeUtf8(dequoteUtf16(), buf, 0xffffff80); continue;
default:
in.fail("Invalid quoted char(" + c + ")");
break;
}
next();
break;
case '"': case '\'':
if (c == quote) {
next();
return buf.toString(StandardCharsets.UTF_8);
} else {
buf.put(c);
next();
}
break;
case '\0':
in.fail("Unterminated string");
return buf.toString(StandardCharsets.UTF_8);
default:
buf.put(c);
next();
break;
}
}
}
private static void writeUtf8(long codepoint, BufferedOutput buf, long mask) {
if ((codepoint & mask) == 0) {
buf.put((byte) ((mask << 1) | codepoint));
} else {
writeUtf8(codepoint >> 6, buf, mask >> (2 - ((mask >> 6) & 0x1)));
buf.put((byte) (0x80 | (codepoint & 0x3f)));
}
}
private final static byte[] unicodeStart = {'\\', 'u'};
private long dequoteUtf16() {
next();
long codepoint = readHexValue(4);
if (codepoint >= 0xd800) {
if (codepoint < 0xdc00) { // high
expect(unicodeStart);
long low = readHexValue(4);
if (low >= 0xdc00 && low < 0xe000) {
codepoint = 0x10000 + ((codepoint - 0xd800) << 10) + (low - 0xdc00);
} else {
in.fail("Missing low surrogate");
}
} else if (codepoint < 0xe000) { // low
in.fail("Unexpected low surrogate");
}
}
return codepoint;
}
private long readHexValue(int numBytes) {
long ret = 0;
for (long i = 0; i < numBytes; ++i) {
switch (c) {
case '0': ret = (ret << 4); break;
case '1': ret = (ret << 4) | 1; break;
case '2': ret = (ret << 4) | 2; break;
case '3': ret = (ret << 4) | 3; break;
case '4': ret = (ret << 4) | 4; break;
case '5': ret = (ret << 4) | 5; break;
case '6': ret = (ret << 4) | 6; break;
case '7': ret = (ret << 4) | 7; break;
case '8': ret = (ret << 4) | 8; break;
case '9': ret = (ret << 4) | 9; break;
case 'a': case 'A': ret = (ret << 4) | 0xa; break;
case 'b': case 'B': ret = (ret << 4) | 0xb; break;
case 'c': case 'C': ret = (ret << 4) | 0xc; break;
case 'd': case 'D': ret = (ret << 4) | 0xd; break;
case 'e': case 'E': ret = (ret << 4) | 0xe; break;
case 'f': case 'F': ret = (ret << 4) | 0xf; break;
default:
in.fail("Invalid hex character");
return 0;
}
next();
}
return ret;
}
private void next() {
if ( ! in.eof()) {
c = in.getByte();
} else {
c = 0;
}
}
private boolean skip(byte x) {
if (c != x) {
return false;
}
next();
return true;
}
private void skipWhiteSpace() {
for (;;) {
switch (c) {
case ' ': case '\t': case '\n': case '\r':
next();
break;
default: return;
}
}
}
private String characterToReadableString(int codePoint) {
if (codePoint == 0)
return "end of data";
else if (Text.isDisplayable(codePoint))
return "character '" + String.valueOf(Character.toChars(c)) + "'";
else
return "character code " + c;
}
}
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