kernel: Add basic file descriptor support

Signed-off-by: Ian Moffett <ian@osmora.org>

1 files changed, 123 insertions, 0 deletions

diff --git a/sys/kern/kern_filedesc.c b/sys/kern/kern_filedesc.c
new file mode 100644
index 0000000..a943714
--- /dev/null
+++ b/sys/kern/kern_filedesc.c
@@ -0,0 +1,123 @@
+/*
+ * Copyright (c) 2023-2024 Ian Marco Moffett and the Osmora Team.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of Hyra nor the names of its
+ *    contributors may be used to endorse or promote products derived from
+ *    this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <sys/filedesc.h>
+#include <sys/proc.h>
+#include <sys/sched.h>
+#include <vm/dynalloc.h>
+#include <assert.h>
+#include <string.h>
+
+/*
+ * Allocate a file descriptor.
+ *
+ * @td: Thread to allocate from, NULL for current thread.
+ */
+struct filedesc *
+fd_alloc(struct proc *td)
+{
+    struct filedesc *fd;
+
+    if (td == NULL) {
+        td = this_td();
+        __assert(td != NULL);
+    }
+
+    for (size_t i = 0; i < PROC_MAX_FDS; ++i) {
+        if (td->fds[i] != NULL) {
+            continue;
+        }
+
+        fd = dynalloc(sizeof(struct filedesc));
+        memset(fd, 0, sizeof(struct filedesc));
+
+        if (fd == NULL) {
+            return NULL;
+        }
+
+        fd->fdno = i;
+        td->fds[i] = fd;
+        return fd;
+    }
+
+    return NULL;
+}
+
+/*
+ * Fetch a file descriptor from a file descriptor
+ * number.
+ *
+ * @td: Thread to fetch from, NULL for current thread.
+ * @fdno: File descriptor to fetch
+ */
+struct filedesc *
+fd_from_fdnum(const struct proc *td, int fdno)
+{
+    if (td == NULL) {
+        td = this_td();
+        __assert(td != NULL);
+    }
+
+    if (fdno < 0 || fdno > PROC_MAX_FDS) {
+        return NULL;
+    }
+
+    for (size_t i = 0; i < PROC_MAX_FDS; ++i) {
+        if (i == fdno && td->fds[i] != NULL) {
+            return td->fds[i];
+        }
+    }
+
+    return NULL;
+}
+
+/*
+ * Close a file descriptor from its fd number.
+ *
+ * @td: Thread to fetch from, NULL for current thread.
+ * @fdno: File descriptor number to close.
+ */
+void
+fd_close_fdnum(struct proc *td, int fdno)
+{
+    struct filedesc *fd;
+
+    if (td == NULL) {
+        td = this_td();
+        __assert(td != NULL);
+    }
+
+    fd = fd_from_fdnum(td, fdno);
+    if (fd == NULL) {
+        return;
+    }
+
+    dynfree(fd);
+    td->fds[fdno] = NULL;
+}