var readStateMachine = function()

in lib/cache.js [1215:1280]
43 lines of code
15 McCabe index (conditional complexity)

    var readStateMachine = function (operation, opTargetState, cacheState, data) {
        

        // Handle cancelation
        if (!cancelStateMachine(operation, opTargetState, cacheState, data)) {

            var transition = operation.transition;

            // Handle preemption
            if (cacheState !== CACHE_STATE_READ && opTargetState !== OPERATION_STATE_START) {
                if (cacheState === CACHE_STATE_DESTROY) {
                    if (opTargetState !== OPERATION_STATE_START) {
                        operation.cancel();
                    }
                } else if (cacheState !== CACHE_STATE_WRITE) {
                    // Signal the cache that a read operation is running.
                    djsassert(state == CACHE_STATE_IDLE || state === CACHE_STATE_PREFETCH, "DataCache.readStateMachine() - cache is not on the read or idle state.");
                    changeState(CACHE_STATE_READ);
                }

                return true;
            }

            switch (opTargetState) {
                case OPERATION_STATE_START:
                    // Initial state of the operation.
                    // Wait until the cache is idle or prefetching.
                    if (cacheState === CACHE_STATE_IDLE || cacheState === CACHE_STATE_PREFETCH) {
                        // Signal the cache that a read operation is running.
                        changeState(CACHE_STATE_READ);
                        if (operation.c >= 0) {
                            // Snap the requested range to a page boundary.
                            var range = snapToPageBoundaries(operation.i, operation.c, pageSize);
                            transition(READ_STATE_LOCAL, range.i);
                        } else {
                            transition(READ_STATE_DONE, operation);
                        }
                    }
                    break;

                case READ_STATE_DONE:
                    // State that determines if the operation can be resolved or has to
                    // continue processing.
                    // Data is expected to be the read page.
                    appendPage(operation, data);
                    var len = getJsonValueArraryLength(operation.d);
                    // Are we done?
                    if (operation.c === len || data.c < pageSize) {
                        // Update the stats, request for a prefetch operation.
                        stats.cacheReads++;
                        prefetch(data.i + data.c);
                        // Terminate the operation.
                        operation.complete();
                    } else {
                        // Continue processing the operation.
                        transition(READ_STATE_LOCAL, data.i + pageSize);
                    }
                    break;

                default:
                    return readSaveStateMachine(operation, opTargetState, cacheState, data, false);
            }
        }

        return true;
    };