Added initial C grader demo

custom-graders/DemoCGrader/README.md

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+# Demo C Custom Grader for Coursera
+
+## Instructions
+
+You have two options of testing the grader: with and without the [coursera_autograder](https://github.com/coursera/coursera_autograder) tool.
+
+### Without the coursera_autograder tool
+
+1. Build the Docker image:
+
+```
+docker build -t cgrader autograder/
+```
+
+2. 

custom-graders/DemoCGrader/autograder/Dockerfile

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+# Fetch ubuntu image
+FROM ubuntu:20.04
+
+# Install Python on your ubuntu image.
+RUN \
+  apt-get update && \
+  apt-get install -y python3 && \
+  apt-get install -y build-essential
+
+# Make directories for the submissions and grader/test programs
+RUN mkdir -p /grader/tests
+RUN mkdir -p /shared/submission
+
+# Copy the grader script into the Docker image
+COPY grader.py /grader/grader.py
+
+# Copy the C source code for the tests into the Docker image
+COPY tests/* /grader/tests/
+
+# Set grader directory to have read/write/execute permissions so we can copy in
+# submissions, compile them, and run them
+RUN chmod a+rwx -R /grader/
+
+# Setup the command that will be invoked when your docker image is run.
+#ENTRYPOINT ["grader/grader.py"]
+
+# For debugging (interactive terminal): comment out above and use empty entrypoint
+ENTRYPOINT []

custom-graders/DemoCGrader/autograder/grader.py

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+#!/usr/bin/python3
+
+# Demo autograder for C files submitted to Coursera. ENTRYPOINT for Dockerfile.
+
+# Dependencies
+import sys
+import os
+import stat
+import shutil
+import subprocess
+import json
+
+# Settings
+SUBMISSION_SRC = "/shared/submission/"  # Standard submission directory across all courses
+COMPILED_APP = "testapp"        # Name of the compiled program (must match in Makefile)
+COMPILER_TIMEOUT = 2.0          # How long to wait for the compiler to finish (seconds)
+RUN_TIMEOUT = 2.0               # How long to wait for the test program to run (seconds)
+
+# Define the test cases and each associated project directory and file
+TEST_CASES = {
+                "power": {
+                    "partId": "4b371f50",
+                    "project_dir": "/grader/tests/power",
+                    "submission_file": "power.c"
+                },
+                "get-bit": {
+                    "partId": "321da787",
+                    "project_dir": "/grader/tests/get-bit",
+                    "submission_file": "get-bit.c"
+                },
+            }
+
+# Helper function to send score and feedback to Coursera
+def send_feedback(score, msg):
+
+    # Combine score and feedback
+    post = {'fractionalScore': score, 'feedback': msg}
+
+    # Optional: this goes to container log and is best practice for debugging purpose
+    print(json.dumps(post))
+
+    # This is required for actual feedback to be surfaced
+    with open("/shared/feedback.json", "w") as outfile:
+        json.dump(post, outfile)
+
+# Main script that runs the given test
+def main(partId):
+
+    # Find the test that we are performing based on the partId
+    test = None
+    for key in TEST_CASES:
+        if partId == TEST_CASES[key]["partId"]:
+            print("Running test:", key)
+            test = TEST_CASES[key]
+            break
+
+    # Return with an error if we do not have a partId that matches to a test
+    if test == None:
+        msg = "Cannot find matching partId. Please double check your partId."
+        print(msg)
+        send_feedback(0.0, msg)
+        return
+
+    # Check to make sure that the student submitted a .c file
+    for file in os.listdir(SUBMISSION_SRC):
+        if file.endswith(".c"):
+            submitted_file = file
+        else:
+            send_feedback(0.0, "Your file must end with a .c extension.")
+            return
+    submitted_file_path = os.path.join(SUBMISSION_SRC, submitted_file)
+
+    # Copy the submitted file to the project folder (has executable permissions)
+    # and rename to the required filename.
+    uut_path = os.path.join(test["project_dir"], test["submission_file"])
+    shutil.copyfile(submitted_file_path, uut_path)
+
+    # Compile the program
+    print("Building...")
+    try:
+        ret = subprocess.run(   ["make", "-C", test["project_dir"]], 
+                                stdout=subprocess.PIPE,
+                                stderr=subprocess.PIPE,
+                                timeout=COMPILER_TIMEOUT)
+    except Exception as e:
+        msg = "ERROR: Compilation failed. " + str(e)
+        print(msg)
+        send_feedback(0.0, msg)
+        return
+
+    # Check to see if the program compiled successfully
+    if ret.returncode != 0:
+        msg = "Compilation failed. Try running on your computer first " \
+                    "before submitting. Compiler error:\r\n" + \
+                    ret.stderr.decode('utf-8')
+        print(msg)
+        send_feedback(0.0, msg)
+        return
+
+    # Run the compiled program
+    print("Running...")
+    app_path = os.path.join(test["project_dir"], COMPILED_APP)
+    try:
+        ret = subprocess.run(   [app_path],
+                                stdout=subprocess.PIPE,
+                                timeout=RUN_TIMEOUT)
+    except Exception as e:
+        msg = "ERROR: Runtime failed. " + str(e)
+        print(msg)
+        send_feedback(0.0, msg)
+        return
+
+    # Parse the output of the program (JSON)
+    try:
+        ret_json = json.loads(ret.stdout.decode('utf-8'))
+    except Exception as e:
+        msg = "ERROR: Could not parse JSON output. " + str(e)
+        print(msg)
+        send_feedback(0.0, msg)
+        return
+
+    # Get the individual scores from the test cases
+    scores = ret_json["scores"]
+
+    # Average the scores to produce a final score (between 0.0 and 1.0)
+    fractional_score = sum(scores) / len(scores)
+
+    # Provide some feedback based on the total score. Feel free to provide
+    # individual feedback based on the partId and which tests passed/failed.
+    if fractional_score > 0.8:
+        msg = "Great job!"
+    elif fractional_score > 0.0:
+        msg = "Close, but try again"
+    else:
+        msg = "Not quite. Try again."
+
+    # Provide score and feedback
+    send_feedback(fractional_score, msg)
+
+# Script entry point
+if __name__ == '__main__':
+    try:
+        partid = os.environ['partId']
+    except Exception as e:
+        msg = "Please provide the partId."
+        print(msg)
+        send_feedback(0.0, msg)
+    else:
+        main(partid)

custom-graders/DemoCGrader/autograder/tests/get-bit/Makefile

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+# Tool macro
+CC = gcc
+
+# Settings
+NAME = app
+
+# Search path for header files (current directory)
+CFLAGS = -I.
+
+# Other compiler flags
+CFLAGS += -Wall
+
+# Names for our output object files
+OBJS = main.o get-bit.o
+
+# Default rule to make our application
+.PHONY: all
+all: testapp
+
+# Compile library source code into object files
+testapp:${OBJS}
+	${CC} ${CFLAGS} -o $@ ${OBJS}
+
+# Remove compiled objects
+.PHONY: clean
+clean:
+	rm -r $(OBJS)

custom-graders/DemoCGrader/autograder/tests/get-bit/get-bit.h

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+#ifndef GET_BIT_H
+#define GET_BIT_H
+
+int getBit(unsigned char byte, unsigned char bit);
+
+#endif // GET_BIT_H

custom-graders/DemoCGrader/autograder/tests/get-bit/main.c

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+#include <stdio.h>
+
+// Include the user's submission
+#include "get-bit.h"
+
+// Define the number of tests to run
+#define NUM_TEST_CASES 5
+
+int main() {
+
+    int ans;
+
+    // Define the test cases
+    const unsigned char inputs[NUM_TEST_CASES][2] = { {0, 5},
+                                            {255, 0},
+                                            {0xAE, 4},
+                                            {0xAE, 5},
+                                            {15, 3}};
+    const unsigned char outputs[NUM_TEST_CASES] = {0, 1, 0, 1, 1};
+
+    // Store which answers were correct
+    float scores[NUM_TEST_CASES];
+
+    // Run the tests, giving a 100% score to each correct answer
+    for (int i = 0; i < NUM_TEST_CASES; i++) 
+    {
+        ans = getBit(inputs[i][0], inputs[i][1]);
+        if (ans == outputs[i])
+        {
+            scores[i] = 1.0;
+        }
+        else
+        {
+            scores[i] = 0.0;
+        }
+    }
+
+    // Print out the test results in JSON format
+    printf("{\"scores\":[");
+    for (int i = 0; i < NUM_TEST_CASES; i++)
+    {
+        printf("%f", scores[i]);
+        if (i < NUM_TEST_CASES - 1)
+        {
+            printf(",");
+        }
+    }
+    printf("]}\r\n");
+
+    return 0;
+}

custom-graders/DemoCGrader/autograder/tests/power/Makefile

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+# Tool macro
+CC = gcc
+
+# Settings
+NAME = app
+
+# Search path for header files (current directory)
+CFLAGS = -I.
+
+# Other compiler flags
+CFLAGS += -Wall
+
+# Names for our output object files
+OBJS = main.o power.o
+
+# Default rule to make our application
+.PHONY: all
+all: testapp
+
+# Compile library source code into object files
+testapp:${OBJS}
+	${CC} ${CFLAGS} -o $@ ${OBJS}
+
+# Remove compiled objects
+.PHONY: clean
+clean:
+	rm -r $(OBJS)

custom-graders/DemoCGrader/autograder/tests/power/main.c

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+#include <stdio.h>
+
+// Include the user's submission
+#include "power.h"
+
+// Define the number of tests to run
+#define NUM_TEST_CASES 5
+
+int main() {
+
+    int ans;
+
+    // Define the test cases
+    const int inputs[NUM_TEST_CASES][2] = { {0, 0},
+                                            {10, 0},
+                                            {1, 2},
+                                            {3, 3},
+                                            {3, 10}};
+    const int outputs[NUM_TEST_CASES] = {1, 1, 1, 27, 59049};
+
+    // Store which answers were correct
+    float scores[NUM_TEST_CASES];
+
+    // Run the tests, giving a 100% score to each correct answer
+    for (int i = 0; i < NUM_TEST_CASES; i++) 
+    {
+        ans = power(inputs[i][0], inputs[i][1]);
+        if (ans == outputs[i])
+        {
+            scores[i] = 1.0;
+        }
+        else
+        {
+            scores[i] = 0.0;
+        }
+    }
+
+    // Print out the test results in JSON format
+    printf("{\"scores\":[");
+    for (int i = 0; i < NUM_TEST_CASES; i++)
+    {
+        printf("%f", scores[i]);
+        if (i < NUM_TEST_CASES - 1)
+        {
+            printf(",");
+        }
+    }
+    printf("]}\r\n");
+
+    return 0;
+}

custom-graders/DemoCGrader/autograder/tests/power/power.h

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+#ifndef POWER_H
+#define POWER_H
+
+int power(int a, int b);
+
+#endif // POWER_H

custom-graders/DemoCGrader/sample-submissions/get-bit/get-bit.c

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+#include "get-bit.h"
+
+// Find the value (0 or 1) of the n-th bit in the provided byte
+int getBit(unsigned char byte, unsigned char bit)
+{
+    int bit_val;
+
+    // YOUR CODE HERE
+    // ---
+    bit_val = (byte >> bit) & 1;
+    // ---
+
+    return bit_val;
+}