From ea6d0aa1d47175c248368292bb2e687c73e1d37a Mon Sep 17 00:00:00 2001
From: Gunnar Beutner <gunnar@beutner.name>
Date: Wed, 14 Apr 2021 04:29:39 +0200
Subject: [PATCH] LibPthread: Implement semaphore functions

---
 Userland/Libraries/LibC/CMakeLists.txt        |  1 -
 Userland/Libraries/LibPthread/CMakeLists.txt  |  1 +
 .../{LibC => LibPthread}/semaphore.cpp        | 79 ++++++++++++++++---
 .../{LibC => LibPthread}/semaphore.h          |  7 +-
 4 files changed, 73 insertions(+), 15 deletions(-)
 rename Userland/Libraries/{LibC => LibPthread}/semaphore.cpp (57%)
 rename Userland/Libraries/{LibC => LibPthread}/semaphore.h (94%)

diff --git a/Userland/Libraries/LibC/CMakeLists.txt b/Userland/Libraries/LibC/CMakeLists.txt
index 1e2b7c4e83..56454f5609 100644
--- a/Userland/Libraries/LibC/CMakeLists.txt
+++ b/Userland/Libraries/LibC/CMakeLists.txt
@@ -24,7 +24,6 @@ set(LIBC_SOURCES
     qsort.cpp
     scanf.cpp
     sched.cpp
-    semaphore.cpp
     serenity.cpp
     signal.cpp
     spawn.cpp
diff --git a/Userland/Libraries/LibPthread/CMakeLists.txt b/Userland/Libraries/LibPthread/CMakeLists.txt
index c28f072b5e..0c29d56e60 100644
--- a/Userland/Libraries/LibPthread/CMakeLists.txt
+++ b/Userland/Libraries/LibPthread/CMakeLists.txt
@@ -1,6 +1,7 @@
 set(SOURCES
     pthread.cpp
     pthread_once.cpp
+    semaphore.cpp
 )
 
 serenity_libc(LibPthread pthread)
diff --git a/Userland/Libraries/LibC/semaphore.cpp b/Userland/Libraries/LibPthread/semaphore.cpp
similarity index 57%
rename from Userland/Libraries/LibC/semaphore.cpp
rename to Userland/Libraries/LibPthread/semaphore.cpp
index 618c3335f0..37361b4471 100644
--- a/Userland/Libraries/LibC/semaphore.cpp
+++ b/Userland/Libraries/LibPthread/semaphore.cpp
@@ -25,41 +25,94 @@
  */
 
 #include <AK/Assertions.h>
+#include <errno.h>
 #include <semaphore.h>
 
 int sem_close(sem_t*)
 {
-    VERIFY_NOT_REACHED();
+    errno = ENOSYS;
+    return -1;
 }
-int sem_destroy(sem_t*)
+
+int sem_destroy(sem_t* sem)
 {
-    VERIFY_NOT_REACHED();
+    pthread_mutex_destroy(&sem->mtx);
+    pthread_cond_destroy(&sem->cv);
+    return 0;
 }
+
 int sem_getvalue(sem_t*, int*)
 {
     VERIFY_NOT_REACHED();
 }
-int sem_init(sem_t*, int, unsigned int)
+
+int sem_init(sem_t* sem, int shared, unsigned int value)
 {
-    VERIFY_NOT_REACHED();
+    if (shared)
+        return ENOSYS;
+
+    if (pthread_mutex_init(&sem->mtx, nullptr) != 0)
+        return -1;
+
+    if (pthread_cond_init(&sem->cv, nullptr) != 0)
+        return -1;
+
+    sem->value = value;
+
+    return 0;
 }
+
 sem_t* sem_open(const char*, int, ...)
 {
-    VERIFY_NOT_REACHED();
+    errno = ENOSYS;
+    return nullptr;
 }
-int sem_post(sem_t*)
+
+int sem_post(sem_t* sem)
 {
-    VERIFY_NOT_REACHED();
+    sem->value++;
+
+    pthread_cond_signal(&sem->cv);
+
+    pthread_mutex_unlock(&sem->mtx);
+
+    return 0;
 }
-int sem_trywait(sem_t*)
+
+int sem_trywait(sem_t* sem)
 {
-    VERIFY_NOT_REACHED();
+    if (pthread_mutex_lock(&sem->mtx) != 0)
+        return -1;
+
+    if (sem->value == 0) {
+        pthread_mutex_unlock(&sem->mtx);
+        errno = EAGAIN;
+        return -1;
+    }
+
+    sem->value--;
+
+    return 0;
 }
+
 int sem_unlink(const char*)
 {
-    VERIFY_NOT_REACHED();
+    return ENOSYS;
 }
-int sem_wait(sem_t*)
+
+int sem_wait(sem_t* sem)
 {
-    VERIFY_NOT_REACHED();
+    if (pthread_mutex_lock(&sem->mtx) != 0)
+        return -1;
+
+    while (sem->value == 0) {
+        if (pthread_cond_wait(&sem->cv, &sem->mtx) != 0) {
+            pthread_mutex_unlock(&sem->mtx);
+            return -1;
+        }
+    }
+
+    sem->value--;
+
+    return 0;
 }
diff --git a/Userland/Libraries/LibC/semaphore.h b/Userland/Libraries/LibPthread/semaphore.h
similarity index 94%
rename from Userland/Libraries/LibC/semaphore.h
rename to Userland/Libraries/LibPthread/semaphore.h
index 4d0444bef5..9371e51215 100644
--- a/Userland/Libraries/LibC/semaphore.h
+++ b/Userland/Libraries/LibPthread/semaphore.h
@@ -26,12 +26,17 @@
 
 #pragma once
 
+#include <pthread.h>
 #include <sys/cdefs.h>
 #include <sys/types.h>
 
 __BEGIN_DECLS
 
-typedef int sem_t;
+typedef struct {
+    pthread_mutex_t mtx;
+    pthread_cond_t cv;
+    int value;
+} sem_t;
 
 int sem_close(sem_t*);
 int sem_destroy(sem_t*);