ObjectLoader load()

in org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/Pack.java [775:917]
121 lines of code
26 McCabe index (conditional complexity)

	ObjectLoader load(WindowCursor curs, long pos)
			throws IOException, LargeObjectException {
		try {
			final byte[] ib = curs.tempId;
			Delta delta = null;
			byte[] data = null;
			int type = Constants.OBJ_BAD;
			boolean cached = false;

			SEARCH: for (;;) {
				readFully(pos, ib, 0, 20, curs);
				int c = ib[0] & 0xff;
				final int typeCode = (c >> 4) & 7;
				long sz = c & 15;
				int shift = 4;
				int p = 1;
				while ((c & 0x80) != 0) {
					c = ib[p++] & 0xff;
					sz += ((long) (c & 0x7f)) << shift;
					shift += 7;
				}

				switch (typeCode) {
				case Constants.OBJ_COMMIT:
				case Constants.OBJ_TREE:
				case Constants.OBJ_BLOB:
				case Constants.OBJ_TAG: {
					if (delta != null || sz < curs.getStreamFileThreshold()) {
						data = decompress(pos + p, (int) sz, curs);
					}

					if (delta != null) {
						type = typeCode;
						break SEARCH;
					}

					if (data != null) {
						return new ObjectLoader.SmallObject(typeCode, data);
					}
					return new LargePackedWholeObject(typeCode, sz, pos, p,
							this, curs.db);
				}

				case Constants.OBJ_OFS_DELTA: {
					c = ib[p++] & 0xff;
					long base = c & 127;
					while ((c & 128) != 0) {
						base += 1;
						c = ib[p++] & 0xff;
						base <<= 7;
						base += (c & 127);
					}
					base = pos - base;
					delta = new Delta(delta, pos, (int) sz, p, base);
					if (sz != delta.deltaSize)
						break SEARCH;

					DeltaBaseCache.Entry e = curs.getDeltaBaseCache().get(this, base);
					if (e != null) {
						type = e.type;
						data = e.data;
						cached = true;
						break SEARCH;
					}
					pos = base;
					continue SEARCH;
				}

				case Constants.OBJ_REF_DELTA: {
					readFully(pos + p, ib, 0, 20, curs);
					long base = findDeltaBase(ObjectId.fromRaw(ib));
					delta = new Delta(delta, pos, (int) sz, p + 20, base);
					if (sz != delta.deltaSize)
						break SEARCH;

					DeltaBaseCache.Entry e = curs.getDeltaBaseCache().get(this, base);
					if (e != null) {
						type = e.type;
						data = e.data;
						cached = true;
						break SEARCH;
					}
					pos = base;
					continue SEARCH;
				}

				default:
					throw new IOException(MessageFormat.format(
							JGitText.get().unknownObjectType,
							Integer.valueOf(typeCode)));
				}
			}

			// At this point there is at least one delta to apply to data.
			// (Whole objects with no deltas to apply return early above.)

			if (data == null)
				throw new IOException(JGitText.get().inMemoryBufferLimitExceeded);

			assert(delta != null);
			do {
				// Cache only the base immediately before desired object.
				if (cached)
					cached = false;
				else if (delta.next == null)
					curs.getDeltaBaseCache().store(this, delta.basePos, data, type);

				pos = delta.deltaPos;

				final byte[] cmds = decompress(pos + delta.hdrLen,
						delta.deltaSize, curs);
				if (cmds == null) {
					data = null; // Discard base in case of OutOfMemoryError
					throw new LargeObjectException.OutOfMemory(new OutOfMemoryError());
				}

				final long sz = BinaryDelta.getResultSize(cmds);
				if (Integer.MAX_VALUE <= sz)
					throw new LargeObjectException.ExceedsByteArrayLimit();

				final byte[] result;
				try {
					result = new byte[(int) sz];
				} catch (OutOfMemoryError tooBig) {
					data = null; // Discard base in case of OutOfMemoryError
					throw new LargeObjectException.OutOfMemory(tooBig);
				}

				BinaryDelta.apply(data, cmds, result);
				data = result;
				delta = delta.next;
			} while (delta != null);

			return new ObjectLoader.SmallObject(type, data);

		} catch (DataFormatException dfe) {
			throw new CorruptObjectException(
					MessageFormat.format(
							JGitText.get().objectAtHasBadZlibStream,
							Long.valueOf(pos), getPackFile()),
					dfe);
		}
	}