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// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.data.access.simple;
import com.yahoo.data.access.ArrayTraverser;
import com.yahoo.data.access.Inspectable;
import com.yahoo.data.access.Inspector;
import com.yahoo.data.access.ObjectTraverser;
/**
* Encodes json from an inspectable object.
*
* @author arnej27959
*/
public final class JsonRender {
public static StringBuilder render(Inspectable value,
StringBuilder target,
boolean compact) {
return render(value, new StringEncoder(target, compact));
}
/**
* Renders the given value to the target stringbuilder with a given encoder.
* This is useful to use an encoder where rendering of some value types is customized.
*/
public static StringBuilder render(Inspectable value, StringEncoder encoder) {
encoder.encode(value.inspect());
return encoder.target();
}
public static class StringEncoder implements ArrayTraverser, ObjectTraverser {
private final StringBuilder out;
private boolean head = true;
private final boolean compact;
private int level = 0;
public StringEncoder(StringBuilder out, boolean compact) {
this.out = out;
this.compact = compact;
}
public void encode(Inspector top) {
encodeValue(top);
if (!compact) {
out.append('\n');
}
}
protected void encodeEMPTY() {
out.append("null");
}
protected void encodeBOOL(boolean value) {
out.append(value ? "true" : "false");
}
protected void encodeLONG(long value) {
out.append(value);
}
protected void encodeDOUBLE(double value) {
if (Double.isFinite(value)) {
out.append(value);
} else {
out.append("null");
}
}
static final char[] hex = "0123456789ABCDEF".toCharArray();
protected void encodeSTRING(String value) {
out.append('"');
for (char c : value.toCharArray()) {
switch (c) {
case '"': out.append('\\').append('"'); break;
case '\\': out.append('\\').append('\\'); break;
case '\b': out.append('\\').append('b'); break;
case '\f': out.append('\\').append('f'); break;
case '\n': out.append('\\').append('n'); break;
case '\r': out.append('\\').append('r'); break;
case '\t': out.append('\\').append('t'); break;
default:
if (c > 0x1f && c < 127) {
out.append(c);
} else { // requires escaping according to RFC 4627
out.append('\\').append('u');
out.append(hex[(c >> 12) & 0xf]);
out.append(hex[(c >> 8) & 0xf]);
out.append(hex[(c >> 4) & 0xf]);
out.append(hex[c & 0xf]);
}
}
}
out.append('"');
}
protected void encodeDATA(byte[] value) {
out.append('"');
out.append("0x");
for (int pos = 0; pos < value.length; pos++) {
out.append(hex[(value[pos] >> 4) & 0xf]);
out.append(hex[value[pos] & 0xf]);
}
out.append('"');
}
protected void encodeARRAY(Inspector inspector) {
openScope("[");
ArrayTraverser at = this;
inspector.traverse(at);
closeScope("]");
}
protected void encodeOBJECT(Inspector inspector) {
openScope("{");
ObjectTraverser ot = this;
inspector.traverse(ot);
closeScope("}");
}
private void openScope(String opener) {
out.append(opener);
level++;
head = true;
}
private void closeScope(String closer) {
level--;
separate(false);
out.append(closer);
}
private void encodeValue(Inspector inspector) {
switch(inspector.type()) {
case EMPTY: encodeEMPTY(); return;
case BOOL: encodeBOOL(inspector.asBool()); return;
case LONG: encodeLONG(inspector.asLong()); return;
case DOUBLE: encodeDOUBLE(inspector.asDouble()); return;
case STRING: encodeSTRING(inspector.asString()); return;
case DATA: encodeDATA(inspector.asData()); return;
case ARRAY: encodeARRAY(inspector); return;
case OBJECT: encodeOBJECT(inspector); return;
}
assert false : "Should not be reached";
}
private void separate(boolean useComma) {
if (!head && useComma) {
out.append(',');
} else {
head = false;
}
if (!compact) {
out.append("\n");
for (int lvl = 0; lvl < level; lvl++) { out.append(" "); }
}
}
public void entry(int idx, Inspector inspector) {
separate(true);
encodeValue(inspector);
}
public void field(String name, Inspector inspector) {
separate(true);
encodeSTRING(name);
out.append(':');
if (!compact)
out.append(' ');
encodeValue(inspector);
}
/** Returns the target this is encoding values to */
public StringBuilder target() { return out; }
}
}
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