From bef91584508f9e381493ce38a21ec617d526f3e2 Mon Sep 17 00:00:00 2001
From: apio <blobs.trading@gmail.com>
Date: Fri, 21 Oct 2022 18:34:31 +0200
Subject: [PATCH] Kernel, libc: Add isatty() and F_ISTTY to fcntl()

---
 kernel/include/fs/FileDescriptor.h |  5 +++++
 kernel/include/fs/VFS.h            |  1 +
 kernel/src/fs/devices/Console.cpp  |  1 +
 kernel/src/fs/devices/Keyboard.cpp |  1 +
 kernel/src/sys/stdio.cpp           | 13 +++++++++++--
 libs/libc/include/fcntl.h          |  2 ++
 libs/libc/include/unistd.h         |  3 +++
 libs/libc/src/unistd.cpp           |  7 +++++++
 8 files changed, 31 insertions(+), 2 deletions(-)

diff --git a/kernel/include/fs/FileDescriptor.h b/kernel/include/fs/FileDescriptor.h
index b6ee909b..c7f0b62c 100644
--- a/kernel/include/fs/FileDescriptor.h
+++ b/kernel/include/fs/FileDescriptor.h
@@ -24,6 +24,11 @@ struct Descriptor
         m_is_open = false;
     }
 
+    VFS::Node* node()
+    {
+        return m_node;
+    }
+
     ssize_t read(size_t size, char* buffer);
     ssize_t write(size_t size, const char* buffer);
 
diff --git a/kernel/include/fs/VFS.h b/kernel/include/fs/VFS.h
index 6519ad59..c159fb11 100644
--- a/kernel/include/fs/VFS.h
+++ b/kernel/include/fs/VFS.h
@@ -30,6 +30,7 @@ namespace VFS
         node_finddir find_func;
         node_mkdir mkdir_func;
         node_write write_func;
+        int tty = 0;
         Node* link;
     };
 
diff --git a/kernel/src/fs/devices/Console.cpp b/kernel/src/fs/devices/Console.cpp
index a4c73ca0..d0157542 100644
--- a/kernel/src/fs/devices/Console.cpp
+++ b/kernel/src/fs/devices/Console.cpp
@@ -13,6 +13,7 @@ VFS::Node* ConsoleDevice::create_new(const char* devname)
     dev->length = 0;
     dev->type = VFS_DEVICE;
     dev->flags = 0;
+    dev->tty = 1;
     strncpy(dev->name, devname, sizeof(dev->name));
     return dev;
 }
diff --git a/kernel/src/fs/devices/Keyboard.cpp b/kernel/src/fs/devices/Keyboard.cpp
index 1a4af295..6907042c 100644
--- a/kernel/src/fs/devices/Keyboard.cpp
+++ b/kernel/src/fs/devices/Keyboard.cpp
@@ -19,6 +19,7 @@ VFS::Node* KeyboardDevice::create_new(const char* devname)
     dev->length = 0;
     dev->type = VFS_DEVICE;
     dev->flags = 0;
+    dev->tty = 1;
     strncpy(dev->name, devname, sizeof(dev->name));
     return dev;
 }
diff --git a/kernel/src/sys/stdio.cpp b/kernel/src/sys/stdio.cpp
index 9f041a66..a83c18d5 100644
--- a/kernel/src/sys/stdio.cpp
+++ b/kernel/src/sys/stdio.cpp
@@ -19,7 +19,8 @@
 #define SEEK_CUR 1
 #define SEEK_END 2
 
-#define FNCTL_DUPFD 0
+#define FCNTL_DUPFD 0
+#define FCNTL_ISTTY 1
 
 void sys_fcntl(Context* context, int fd, int command, uintptr_t arg)
 {
@@ -35,7 +36,7 @@ void sys_fcntl(Context* context, int fd, int command, uintptr_t arg)
         return;
     }
     Descriptor& file = current_task->files[fd];
-    if (command == FNCTL_DUPFD)
+    if (command == FCNTL_DUPFD)
     {
         if ((int)arg < 0 || (int)arg >= TASK_MAX_FDS)
         {
@@ -53,6 +54,14 @@ void sys_fcntl(Context* context, int fd, int command, uintptr_t arg)
         kdbgln("fcntl(F_DUPFD): duplicated fd %d, result is %d", fd, dupfd);
         return;
     }
+    else if (command == FCNTL_ISTTY)
+    {
+        VFS::Node* node = file.node();
+        if (node->tty) { context->rax = 1; }
+        else
+            context->rax = -ENOTTY;
+        return;
+    }
     else
     {
         context->rax = -EINVAL;
diff --git a/libs/libc/include/fcntl.h b/libs/libc/include/fcntl.h
index 1f4b2715..fb358446 100644
--- a/libs/libc/include/fcntl.h
+++ b/libs/libc/include/fcntl.h
@@ -10,6 +10,8 @@
 
 /* Duplicate a file descriptor. */
 #define F_DUPFD 0
+/* Is a file descriptor a TTY? */
+#define F_ISTTY 1
 
 #ifdef __cplusplus
 extern "C"
diff --git a/libs/libc/include/unistd.h b/libs/libc/include/unistd.h
index 54358f21..942302ca 100644
--- a/libs/libc/include/unistd.h
+++ b/libs/libc/include/unistd.h
@@ -66,6 +66,9 @@ extern "C"
     /* Checks if the current program can access the file or directory at path. */
     int access(const char* path, int amode);
 
+    /* Checks if the file descriptor fd refers to a terminal. */
+    int isatty(int fd);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/libs/libc/src/unistd.cpp b/libs/libc/src/unistd.cpp
index 43d9b5b3..2f64ef22 100644
--- a/libs/libc/src/unistd.cpp
+++ b/libs/libc/src/unistd.cpp
@@ -74,4 +74,11 @@ extern "C"
     {
         return (int)syscall(SYS_access, path, amode);
     }
+
+    int isatty(int fd)
+    {
+        int result = fcntl(fd, F_ISTTY);
+        if (result < 0) return 0;
+        return 1;
+    }
 }
\ No newline at end of file