Diff: main.cpp

Revision:

0:301a83d3eeb4

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Thu Mar 19 17:08:55 2015 +0000
@@ -0,0 +1,158 @@
+#include "mbed.h"
+
+Serial pc(USBTX,USBRX);
+
+int taskCount = 0;
+const int maxTasks = 16;
+void *taskList[maxTasks];
+
+typedef void function_t(void);
+
+//runs the next task. Avoid calling from a ticker since that would block all interrupts while running.
+void nextTask(void)
+{
+    static int taskID = 0;
+    if (taskCount) {
+        if (taskID >= taskCount) // a task could have been removed.
+            taskID = 0;
+
+        ((function_t*)taskList[taskID])();
+        taskID++;
+        if (taskID == taskCount)
+            taskID = 0;
+    }
+}
+
+// add a task to the list
+bool addTask(void (*function)(void))
+{
+    if ((taskCount < maxTasks) && function) {
+        taskList[taskCount] = (void *)function;
+        taskCount++;
+        return true;
+    } else
+        return false;
+}
+
+// finds a task in the list or -1 if not in the list. Mainly used for removing tasks.
+int findTask(void (*function)(void))
+{
+    if (!function)
+        return -1;
+    int number = 0;
+    while (number < taskCount) {
+        if (taskList[number] == (void *)function)
+            return number;
+        number++;
+    }
+    return -1;
+}
+
+// remove a task. returns false if the task wasn't in the list.
+bool removeTask(void (*function)(void))
+{
+    int taskToRemove = findTask(function);
+    if (taskToRemove == -1)
+        return false;
+
+    for (int i = taskToRemove; i<(taskCount-1); i++) {
+        taskList[i] = taskList[i+1];
+    }
+    taskCount--;
+    return true;
+}
+
+// simple example task.
+void task1(void)
+{
+    const int NumberOfStates = 5;
+    static int state = 0;
+    switch (state) {
+        case 0:
+            pc.putc('A');
+            break;
+        case 1:
+            pc.putc('B');
+            break;
+        case 2:
+            pc.putc('C');
+            break;
+        case 3:
+            pc.putc('D');
+            break;
+        case 4:
+            pc.putc('E');
+            break;
+        default:
+            state = 0;
+            break;
+    }
+    state++;
+    if (state == NumberOfStates)
+        state = 0;
+}
+
+// simple example task.
+void task2(void)
+{
+    const int NumberOfStates = 2;
+    static int state = 0;
+    switch (state) {
+        case 0:
+            pc.putc('1');
+            break;
+        case 1:
+            pc.putc('2');
+            break;
+        default:
+            state = 0;
+            break;
+    }
+    state++;
+    if (state == NumberOfStates)
+        state = 0;
+}
+
+// simple example task using enum for current state.
+void task3(void)
+{
+    static enum {firstState,secondState} state = firstState;
+    switch (state) {
+        case firstState:
+            pc.putc('X');
+            state = secondState;
+            break;
+        case secondState:
+            pc.putc('Y');
+            state = firstState;
+            break;
+        default:
+            state = firstState;
+            break;
+    }
+}
+
+main ()
+{
+
+    addTask(&task1);
+    addTask(&task2);
+    pc.printf("\r\nTasks 1 & 2\r\n");
+    for (int i = 0; i < 20; i++)
+        nextTask();
+
+
+    addTask(&task1);
+    addTask(&task3);
+    pc.printf("\r\nTasks 1,2,1,3\r\n");
+    for (int i = 0; i < 20; i++)
+        nextTask();
+
+    removeTask(&task1); // removes the first instance of task 1 in the list.
+    pc.printf("\r\nTasks 2,1,3\r\n");
+    for (int i = 0; i < 20; i++)
+        nextTask();
+
+    pc.printf("\r\nDone\r\n");
+
+}
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