From db7dd9d3d2c597c2f6740d3f11c4b4bb53d5cf65 Mon Sep 17 00:00:00 2001
From: Matthias Kruk <m@m10k.eu>
Date: Sat, 15 Aug 2020 15:20:11 +0900
Subject: [PATCH] sys/io: Add proc_get_fd() function implementation

---
 sys/io/proc.c | 36 ++++++++++++++++++++++++++++++++++++
 sys/io/proc.h |  1 +
 2 files changed, 37 insertions(+)

diff --git a/sys/io/proc.c b/sys/io/proc.c
index ef49397..7812102 100644
--- a/sys/io/proc.c
+++ b/sys/io/proc.c
@@ -235,3 +235,39 @@ int proc_add_fd(struct proc *proc, struct filedesc *fd)
 
 	return(ret_val);
 }
+
+/*
+ * proc_get_fd() - Look up a file descriptor using its number
+ *
+ * SYNOPSIS
+ *  int proc_get_fd(struct proc *proc, const int fd, struct filedesc **dst);
+ *
+ * DESCRIPTION
+ *  The proc_get_fd() function retrieves the file descriptor structure that is associated with the
+ *  descriptor number `fd' in the process pointed to by `proc'. Upon success, the pointer pointed
+ *  to by `dst' will be adjusted to point to the file descriptor.
+ *
+ * RETURN VALUE
+ *  Upon success, zero is returned. Otherwise, a negative error number is returned and the value
+ *  of `*dst' is undefined.
+ *
+ * ERRORS
+ *  -EINVAL Invalid arguments have been passed to the function
+ *  -ENOENT There is no file descriptor associated with the file descriptor number `fd'
+ */
+int proc_get_fd(struct proc *proc, const int fd, struct filedesc **dst)
+{
+	int ret_val;
+
+	ret_val = -EINVAL;
+
+	if(proc && fd >= 0 && dst) {
+		ret_val = -ENOENT;
+
+		if(!cx_array_get(proc->p_fds, fd, (void**)dst)) {
+			ret_val = 0;
+		}
+	}
+
+	return(ret_val);
+}
diff --git a/sys/io/proc.h b/sys/io/proc.h
index 8588823..7836544 100644
--- a/sys/io/proc.h
+++ b/sys/io/proc.h
@@ -12,5 +12,6 @@ int proc_new(const pid_t, struct proc**);
 void proc_free(struct proc*);
 
 int proc_add_fd(struct proc*, struct filedesc*);
+int proc_get_fd(struct proc*, const int, struct filedesc**);
 
 #endif /* PROC_H */
-- 
2.47.3