Method readBufferExtent

runtime/Log.cc:1181–1226

* Read in the next buffer fragment from the compressed log. If an error occurs * the file descriptor will be in an undefined state. * * \param fd * File stream to read it from * \param[out] wrapAround * Indicates whether a wrap around was indicated in the log or not. * * \return * indicates whether the operation succeeded (true) or failed due to * a malformed log data

 *      a malformed log data.
 */
bool
Log::Decoder::BufferFragment::readBufferExtent(FILE *fd, bool *wrapAround) {
    validBytes = fread(storage, 1, sizeof(BufferExtent), fd);
    BufferExtent *be = reinterpret_cast<BufferExtent*>(storage);

    if (be->entryType != EntryType::BUFFER_EXTENT ||
            validBytes < sizeof(BufferExtent) ||
            be->length > sizeof(storage)) {
        reset();
        return false;
    }

    assert(be->length >= validBytes);
    uint64_t remaining = be->length - validBytes;
    validBytes += fread(storage + validBytes, 1, remaining, fd);

    if (validBytes != be->length) {
        reset();
        return false;
    }

    readPos = storage + sizeof(BufferExtent);
    endOfBuffer = storage + validBytes;

    if (be->isShort)
        runtimeId = be->threadIdOrPackNibble;
    else
        runtimeId = BufferUtils::unpack<uint32_t>(
                                            &readPos, be->threadIdOrPackNibble);

    if (wrapAround)
        *wrapAround = be->wrapAround;

    // The buffer has no log messages, skip it (this may be possible in cases
    // where we want to mark wrapArounds or the output buffer ran out of space).
    if (readPos == endOfBuffer) {
        hasMoreLogs = false;
        return true;
    }

    hasMoreLogs = decompressLogHeader(&readPos, 0, nextLogId, nextLogTimestamp);
    if (!hasMoreLogs)
        reset();

    return hasMoreLogs;
}

/**
 * Helper to decompressNextLogStatement to print a single PrintFragment