From 1695418dcb32ee2dc1ae21a05772e9ad8ec8a2cb Mon Sep 17 00:00:00 2001
From: EnderIce2 <enderice2@protonmail.com>
Date: Thu, 26 Dec 2024 03:20:27 +0200
Subject: [PATCH] kernel/syscalls: Implement sys_tell & sys_seek

Signed-off-by: EnderIce2 <enderice2@protonmail.com>
---
 Kernel/include/interface/syscalls.h | 53 +++++++++++++++++++++++++++++
 Kernel/syscalls/native.cpp          | 18 ++++++++++
 2 files changed, 71 insertions(+)

diff --git a/Kernel/include/interface/syscalls.h b/Kernel/include/interface/syscalls.h
index 74cb8105..34913e77 100644
--- a/Kernel/include/interface/syscalls.h
+++ b/Kernel/include/interface/syscalls.h
@@ -232,6 +232,13 @@ typedef enum
 	__SYS_SET_FS = 3,
 } prctl_options_t;
 
+typedef enum
+{
+	__SYS_SEEK_SET = 0,
+	__SYS_SEEK_CUR = 1,
+	__SYS_SEEK_END = 2
+} seek_whence_t;
+
 typedef enum
 {
 	__SYS_SIGNULL = 0,
@@ -685,6 +692,46 @@ typedef enum
 	 * - #EINVAL if `length` is invalid
 	 */
 	SYS_FTRUNCATE,
+	/**
+	 * @brief Get the current file offset
+	 *
+	 * @code
+	 * off_t tell(int fd);
+	 * @endcode
+	 *
+	 * @details Returns the current file offset for the file referred to by `fd`.
+	 *
+	 * @param fd File descriptor
+	 *
+	 * @return
+	 * - Current file offset on success
+	 * - #EBADF if `fd` is not a valid file descriptor
+	 */
+	SYS_TELL,
+	/**
+	 * @brief Set the file offset
+	 *
+	 * @code
+	 * off_t seek(int fd, off_t offset, int whence);
+	 * @endcode
+	 *
+	 * @details Sets the file offset for the file referred to by `fd` to the
+	 * specified `offset` according to the directive `whence`.
+	 *
+	 * @param fd File descriptor
+	 * @param offset Offset to set
+	 * @param whence Directive for setting the offset\n
+	 *               Supported values:
+	 *               - #__SYS_SEEK_SET: Set the offset to `offset` bytes
+	 *               - #__SYS_SEEK_CUR: Set the offset to the current offset plus `offset`
+	 *               - #__SYS_SEEK_END: Set the offset to the size of the file plus `offset`
+	 *
+	 * @return
+	 * - New file offset on success
+	 * - #EBADF if `fd` is not a valid file descriptor
+	 * - #EINVAL if `whence` is invalid
+	 */
+	SYS_SEEK,
 
 	/* Process Control */
 
@@ -1376,6 +1423,12 @@ typedef enum
 /** @copydoc SYS_FTRUNCATE */
 #define call_ftruncate(fd, length) syscall2(SYS_FTRUNCATE, (scarg)fd, (scarg)length)
 
+/** @copydoc SYS_TELL */
+#define call_tell(fd) syscall1(SYS_TELL, (scarg)fd)
+
+/** @copydoc SYS_SEEK */
+#define call_seek(fd, offset, whence) syscall3(SYS_SEEK, (scarg)fd, (scarg)offset, (scarg)whence)
+
 /* Process Control */
 
 /** @copydoc SYS_EXIT */
diff --git a/Kernel/syscalls/native.cpp b/Kernel/syscalls/native.cpp
index 088ea40e..9a8649c8 100644
--- a/Kernel/syscalls/native.cpp
+++ b/Kernel/syscalls/native.cpp
@@ -159,6 +159,22 @@ static int sys_access(SysFrm *Frame, const char *pathname, int mode)
 static int sys_truncate(SysFrm *Frame, const char *pathname, off_t length) { return -ENOSYS; }
 static int sys_ftruncate(SysFrm *Frame, int fd, off_t length) { return -ENOSYS; }
 
+static int sys_tell(SysFrm *Frame, int fd)
+{
+	PCB *pcb = thisProcess;
+	vfs::FileDescriptorTable *fdt = pcb->FileDescriptors;
+
+	return fdt->usr_lseek(fd, 0, SEEK_CUR);
+}
+
+static off_t sys_seek(SysFrm *Frame, int fd, off_t offset, int whence)
+{
+	PCB *pcb = thisProcess;
+	vfs::FileDescriptorTable *fdt = pcb->FileDescriptors;
+
+	return fdt->usr_lseek(fd, offset, whence);
+}
+
 static __noreturn void sys_exit(SysFrm *Frame, int status)
 {
 	TCB *t = thisThread;
@@ -333,6 +349,8 @@ __constructor void __init_native_syscalls(void)
 	scTbl[SYS_ACCESS] = {"SYS_ACCESS", (void *)sys_access};
 	scTbl[SYS_TRUNCATE] = {"SYS_TRUNCATE", (void *)sys_truncate};
 	scTbl[SYS_FTRUNCATE] = {"SYS_FTRUNCATE", (void *)sys_ftruncate};
+	scTbl[SYS_TELL] = {"SYS_TELL", (void *)sys_tell};
+	scTbl[SYS_SEEK] = {"SYS_SEEK", (void *)sys_seek};
 
 	/* Process Control */
 	scTbl[SYS_EXIT] = {"SYS_EXIT", (void *)sys_exit};