UnenclosedGeoJsonRecordReader.java

package com.esri.json.hadoop;

import java.io.IOException;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.conf.Configuration;

/**
 * 
 * Enumerates records from an Unenclosed GeoJSON file
 * 
 */
/*
 * The JSON will look like this (white-space ignored)
 * 
 * { // start record 1
 *  "type" : ""
 * 	"properties" : {}
 *  "geometry" : {}
 * } // end record 1
 * { // start record 2
 *  "type" : ""
 * 	"properties" : {}
 *  "geometry" : {}
 * } // end record 2
 */
public class UnenclosedGeoJsonRecordReader extends UnenclosedBaseJsonRecordReader {
	static final Log LOG = LogFactory.getLog(UnenclosedGeoJsonRecordReader.class.getName());

	public UnenclosedGeoJsonRecordReader() throws IOException {  // explicit just to declare exception
        super();
	}

	public UnenclosedGeoJsonRecordReader(org.apache.hadoop.mapred.InputSplit split,
										 Configuration conf) throws IOException {
		//attrLabel = "properties";
        super(split, conf);
	}



	// Record boundary defined as : \{\s*"(properties|geometry)"\s*:\s*\{ 
	protected boolean moveToRecordStart() throws IOException {
		// The case of split point exactly at whitespace between records, is
		// handled by forcing it to the split following, in the interest of
		// better balancing the splits, by consuming the whitespace in next().
		// The alternative of forcing it to the split preceding, could be
		// done like what is commented here.
		//   while (next != '{' || skipDup > 0) {  // skipDup>0 => record already consumed
		// 	  next = getChar();
		// 	  if (next < 0)  return false;   // end of stream, no good
		// 	  if (next == '}')  skipDup = -1;  // Definitely not
		// 	  else if (skipDup == 0) skipDup = 1;  // no info - Maybe so until refuted by '}'
		//   }

        final int START=0, BRACE=1, TYPE=2, FOUND=3, FAIL=4;
		int next = 0, state = START;
		long resetPosition = readerPosition;
		boolean inEscape = false;
		String fieldName = "";

		while (true) {
			switch(state) {
			case START:
				// scan until we reach a {
				while (next != '{') {
					next = getChar();
					// end of stream, no good
					if (next < 0) {
						return false;
					}
				}

				resetPosition = readerPosition;
				inputReader.mark(100);

				// ok last char was '{', skip till we get to a '"'
				next = getNonWhite();
				if (next < 0) {   // end of stream, no good
					return false;
				}
				if (next == '"') {
					state = BRACE;
				}  // else redo START
				break;

			case BRACE:
				fieldName = "";
				// Next should be a field name of "geometry" or "properties" or "type".

				// If we see another opening brace, the previous one must have been inside
				// a quoted string literal (after which the double quote we found, was a
				// closing quote mark rather than the opening quote mark) - start over.

				while (next != '{') {
					next = getChar();
					if (next < 0) {  // end of stream, no good
						return false;
					}

					inEscape = (!inEscape && next == '\\');
					if (!inEscape && next == '"') {
						break;
					}

					fieldName += (char)next;
				}

				if (fieldName.equals("properties") || fieldName.equals("geometry")) {
					// ok last char was '"', skip till we get to a ':'
					if ((next = getNonWhite()) < 0) {   // end of stream, no good
						return false;
					}
					if (next != ':') {
						state = START;
					} else {
						// and finally, if the next char is a {, we know for sure that this is a valid record
						if ((next = getNonWhite()) < 0) {   // end of stream, no good
							return false;
						}
						state = (next == '{') ? FOUND : START;
					}
				} else if (fieldName.equals("type")) {
					state = TYPE;
				} else {
					// not a field name we were expecting, start over
					state = START;
				}
				break;

			case TYPE:  // expect  :"Feature","
					if ((next = getNonWhite()) < 0) {   // end of stream, no good
						return false;
					}
					if (next != ':') {
						state = START;
					} else {
						if ((next = getNonWhite()) < 0) {   // end of stream, no good
							return false;
						}
						if (next != '"') {
							state = START;
						} else {
							fieldName = "";
							while (true) {
								if ((next = getChar()) < 0)  return false;  // end of stream, no good
								inEscape = (!inEscape && next == '\\');
								if (!inEscape && next == '"')  break;
								fieldName += (char)next;
							}
							if (!"feature".equals(fieldName.toLowerCase())) {
								state = START;
							} else {
								if ((next = getNonWhite()) < 0) {   // end of stream, no good
									return false;
								}
								if (next != ',') {
									state = START;
								} else {
									if ((next = getNonWhite()) < 0) {   // end of stream, no good
										return false;
									}
									state = (next == '"') ? BRACE : START;
								}
							}
						}
					}
				break;

			case FOUND:
				inputReader.reset();
				readerPosition = resetPosition;
				firstBraceConsumed = true;
				return true;

			case FAIL:
				return false;

			default:
				throw new RuntimeException("Internal error");
			}
		}

	}

}