137 lines
4.2 KiB
Java
137 lines
4.2 KiB
Java
/*
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* Copyright (c) 2011 Tony Garnock-Jones. All rights reserved.
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*/
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package hop;
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import java.io.IOException;
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import java.io.InputStream;
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public class SexpReader {
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public InputStream _input;
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public SexpReader(InputStream input) {
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_input = input;
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}
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/**
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* Reads a sexp length-prefix from _input.
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* @return The read length, or -1 if the end of stream is reached
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* @throws IOException
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* @throws SexpSyntaxError
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*/
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public int _readLength(int lengthSoFar) throws IOException {
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int length = lengthSoFar;
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while (true) {
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int c = _input.read();
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if (c == -1) return -1;
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if (c == ':') {
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return length;
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}
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if (!Character.isDigit(c)) {
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throw new SexpSyntaxError("Invalid length prefix");
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}
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length = length * 10 + (c - '0');
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}
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}
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/**
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* Reads a simple length-prefixed string from _input, given either zero or the value
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* of the first digit of the length-prefix being read.
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* @param lengthSoFar either zero or the first digit of the length prefix to use
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* @return the read string
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* @throws IOException
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* @throws SexpSyntaxError
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*/
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public byte[] _readSimpleString(int lengthSoFar) throws IOException {
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int length = _readLength(lengthSoFar);
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if (length == -1) return null;
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byte[] buf = new byte[length];
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int offset = 0;
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while (length > 0) {
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int count = _input.read(buf, offset, length);
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if (count == -1) {
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throw new SexpSyntaxError("End-of-stream in the middle of a simple string");
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}
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offset += count;
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length -= count;
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}
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return buf;
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}
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public byte[] readSimpleString() throws IOException {
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return _readSimpleString(0);
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}
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public SexpList _readList() throws IOException {
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SexpList list = new SexpList();
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while (true) {
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int c = _input.read();
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switch (c) {
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case -1:
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throw new SexpSyntaxError("Unclosed list");
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case ')':
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return list;
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default:
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list.add(_read(c));
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break;
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}
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}
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}
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public Object _read(int c) throws IOException {
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while (true) {
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switch (c) {
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case -1:
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return null;
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case '(':
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return _readList();
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case ')':
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throw new SexpSyntaxError("Unexpected close-paren");
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case '[':
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byte[] hint = readSimpleString();
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switch (_input.read()) {
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case -1:
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throw new SexpSyntaxError("End-of-stream between display hint and body");
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case ']':
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break;
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default:
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throw new SexpSyntaxError("Unexpected character after display hint");
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}
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byte[] body = readSimpleString();
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return new SexpDisplayHint(hint, body);
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default:
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if (Character.isDigit(c)) {
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return new SexpBytes(_readSimpleString(c - '0'));
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} else if (Character.isWhitespace(c)) {
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// Skip harmless (?) whitespace
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c = _input.read();
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continue;
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} else {
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throw new SexpSyntaxError("Unexpected character: " + c);
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}
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}
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}
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}
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public Object read() throws IOException {
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return _read(_input.read());
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}
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public SexpList readList() throws IOException {
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Object x = read();
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if (x != null && !(x instanceof SexpList)) {
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throw new SexpSyntaxError("Unexpected non-list");
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}
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return (SexpList) x;
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}
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public SexpBytes readBytes() throws IOException {
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Object x = read();
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if (x != null && !(x instanceof SexpBytes)) {
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throw new SexpSyntaxError("Unexpected non-bytes");
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}
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return (SexpBytes) x;
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}
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} |