feat: assignment 3

assignment3/default.nix

@@ -0,0 +1,21 @@
+let
+  basicC = subdir: name: { stdenv }:
+    stdenv.mkDerivation {
+      inherit name;
+      src = ./.;
+      buildPhase = ''
+        runHook preBuild
+        gcc ${subdir}/${name}.c -o ${name}.bin -pthread -lrt
+        runHook postBuild
+      '';
+      installPhase = ''
+        runHook preInstall
+        mkdir -p $out/bin
+        install ${name}.bin $out/bin/${name}
+        runHook postInstall
+      '';
+    };
+in {
+  a3-producer = basicC "src" "producer";
+  a3-consumer = basicC "src" "consumer";
+}

assignment3/src/buffer.h

@@ -0,0 +1,22 @@
+#ifndef BUFFER_H_
+#define BUFFER_H_
+
+#define BUFFER_SIZE 10
+#define SHM_KEY 0x1234
+#define SEM_MUTEX "/sem_mutex"
+#define SEM_EMPTY "/sem_empty"
+#define SEM_FULL "/sem_full"
+
+typedef struct item_t {
+  int value;       // Data value
+  int producer_id; // Which producer created this
+} item_t;
+
+typedef struct shared_buffer_t {
+  item_t buffer[BUFFER_SIZE];
+  int head;  // Next write position
+  int tail;  // Next read position
+  int count; // Current items in buffer
+} shared_buffer_t;
+
+#endif // BUFFER_H_

assignment3/src/consumer.c

@@ -0,0 +1,91 @@
+#include "buffer.h"
+#include <fcntl.h>
+#include <semaphore.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/shm.h>
+#include <unistd.h>
+
+shared_buffer_t *buffer = NULL;
+sem_t *mutex = NULL;
+sem_t *empty = NULL;
+sem_t *full = NULL;
+int shm_id = -1;
+
+void cleanup() {
+  // Detach shared memory
+  if (buffer != NULL) {
+    shmdt(buffer);
+  }
+
+  // Close semaphores (don't unlink - other processes may be using)
+  if (mutex != SEM_FAILED)
+    sem_close(mutex);
+  if (empty != SEM_FAILED)
+    sem_close(empty);
+  if (full != SEM_FAILED)
+    sem_close(full);
+}
+
+void signal_handler(int sig) {
+  printf("\nProducer: Caught signal %d, cleaning up...\n", sig);
+  cleanup();
+  exit(2);
+}
+
+int main(int argc, char *argv[]) {
+  // Argument parsing
+  if (argc != 3) {
+    printf("Usage: %s <id> <number of msgs>\n", argv[0]);
+    return 1;
+  }
+  int id = atoi(argv[1]);
+  int num_items = atoi(argv[2]);
+
+  // Setup shared memory
+  shm_id = shmget(SHM_KEY, sizeof(shared_buffer_t), IPC_CREAT | 0666);
+  if (shm_id < 0) {
+    perror("shmget-failed");
+    return 1;
+  }
+
+  buffer = (shared_buffer_t *)shmat(shm_id, NULL, 0);
+  if (buffer == (void *)-1) {
+    perror("shmat-failed");
+    return 1;
+  }
+
+  // Open semaphores
+  mutex = sem_open(SEM_MUTEX, 0, 0644, 1);
+  empty = sem_open(SEM_EMPTY, 0, 0644, BUFFER_SIZE);
+  full = sem_open(SEM_FULL, 0, 0644, 0);
+
+  if (mutex == SEM_FAILED || empty == SEM_FAILED || full == SEM_FAILED) {
+    perror("sem_open-failed");
+    return 1;
+  }
+
+  // Primary logic
+  for (int i = 0; i < num_items; i++) {
+    sem_wait(full);  // Wait for item
+    sem_wait(mutex); // Enter critical section
+
+    // Remove from buffer
+    item_t item = buffer->buffer[buffer->tail];
+    buffer->tail = (buffer->tail + 1) % BUFFER_SIZE;
+    buffer->count--;
+
+    printf("Consumer %d: Consumed value %d from Producer %d\n", id, item.value,
+           item.producer_id);
+
+    sem_post(mutex); // Exit critical section
+    sem_post(empty); // Signal slot available
+
+    usleep(rand() % 100000); // Simulate work
+  }
+
+  // Cleanup
+  printf("Consumer %d: Finished consuming %d items\n", id, num_items);
+  cleanup();
+  return 0;
+}

assignment3/src/producer.c

@@ -0,0 +1,99 @@
+#include "buffer.h"
+#include <fcntl.h>
+#include <semaphore.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/shm.h>
+#include <time.h>
+#include <unistd.h>
+
+shared_buffer_t *buffer = NULL;
+sem_t *mutex = NULL;
+sem_t *empty = NULL;
+sem_t *full = NULL;
+int shm_id = -1;
+
+void cleanup() {
+  // Detach shared memory
+  if (buffer != NULL) {
+    shmdt(buffer);
+  }
+
+  // Close semaphores (don't unlink - other processes may be using)
+  if (mutex != SEM_FAILED)
+    sem_close(mutex);
+  if (empty != SEM_FAILED)
+    sem_close(empty);
+  if (full != SEM_FAILED)
+    sem_close(full);
+}
+
+void signal_handler(int sig) {
+  printf("\nProducer: Caught signal %d, cleaning up...\n", sig);
+  cleanup();
+  exit(2);
+}
+
+int main(int argc, char *argv[]) {
+  // Argument parsing
+  if (argc != 3) {
+    printf("Usage: %s <id> <number of msgs>\n", argv[0]);
+    return 1;
+  }
+  int id = atoi(argv[1]);
+  int num_items = atoi(argv[2]);
+
+  // Signal handlers
+  signal(SIGINT, signal_handler);
+  signal(SIGTERM, signal_handler);
+
+  // Setup shared memory
+  shm_id = shmget(SHM_KEY, sizeof(shared_buffer_t), IPC_CREAT | 0666);
+  if (shm_id < 0) {
+    perror("shmget-failed");
+    return 1;
+  }
+
+  buffer = (shared_buffer_t *)shmat(shm_id, NULL, 0);
+  if (buffer == (void *)-1) {
+    perror("shmat-failed");
+    return 1;
+  }
+
+  // Open semaphores
+  mutex = sem_open(SEM_MUTEX, O_CREAT, 0644, 1);
+  empty = sem_open(SEM_EMPTY, O_CREAT, 0644, BUFFER_SIZE);
+  full = sem_open(SEM_FULL, O_CREAT, 0644, 0);
+
+  if (mutex == SEM_FAILED || empty == SEM_FAILED || full == SEM_FAILED) {
+    perror("sem_open-failed");
+    return 1;
+  }
+
+  // Primary logic
+  unsigned int seed = time(NULL) + id;
+  for (int i = 0; i < num_items; i++) {
+    item_t item = {.producer_id = id, .value = rand_r(&seed) % 1000};
+
+    sem_wait(empty); // Wait for empty slot
+    sem_wait(mutex); // Enter critical section
+
+    // Add to buffer
+    buffer->buffer[buffer->head] = item;
+    buffer->head = (buffer->head + 1) % BUFFER_SIZE;
+    buffer->count++;
+
+    printf("Producer %d: Produced value %d\n", id, item.value);
+
+    sem_post(mutex); // Exit critical section
+    sem_post(full);  // Signal item available
+
+    usleep(rand_r(&seed) % 100000); // Simulate work
+  }
+
+  // Cleanup
+  printf("Producer %d: Finished producing %d items\n", id, num_items);
+  cleanup();
+  return 0;
+}

assignment3/test

@@ -0,0 +1,38 @@
+#!/usr/bin/env bash
+
+echo "Building executables..."
+
+cd "${FLAKE:-$(dirname $0)}"
+if command -v nix; then
+    producer="$(nix build --no-link --print-out-paths .#a3-producer)/bin/producer"
+    consumer="$(nix build --no-link --print-out-paths .#a3-consumer)/bin/consumer"
+else
+    mkdir build
+    gcc src/producer.c -o build/producer -pthread -lrt
+    gcc src/consumer.c -o build/consumer -pthread -lrt
+    producer="./build/producer"
+    consumer="./build/consumer"
+fi
+
+echo -e "\nTEST - Basic Functionality"
+"${producer}" 1 5 &
+"${consumer}" 1 5 &
+wait
+
+echo -e "\nTEST - Multiple Producers"
+"${producer}" 1 10 &
+"${producer}" 2 10 &
+"${producer}" 3 10 &
+"${consumer}" 1 30 &
+wait
+
+echo -e "\nTEST - Multiple Consumers"
+"${producer}" 1 20 &
+"${consumer}" 1 10 &
+"${consumer}" 2 10 &
+wait
+
+# Cleanup
+ipcrm -M 0x1234
+rm /dev/shm/sem*
+rm -rf build

assignment3/test.nix

@@ -0,0 +1,9 @@
+{
+  a3 = { runCommandLocal, makeWrapper }:
+    runCommandLocal "a3-test" { nativeBuildInputs = [ makeWrapper ]; }
+      ''
+        mkdir -p $out/bin
+        install ${./test} $out/bin/a3-test
+        wrapProgram "$out/bin/a3-test" --set FLAKE ${../.}
+      '';
+}

flake.nix

@@ -11,6 +11,7 @@
       subdirs = [
         "assignment1"
         "assignment2"
+        "assignment3"
         "project1"
         "project2"
       ];