usr: libc: Introduce POSIX fseek()

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

2 files changed, 44 insertions, 0 deletions

diff --git a/lib/libc/include/stdio.h b/lib/libc/include/stdio.h
index d721e4e..37931ce 100644
--- a/lib/libc/include/stdio.h
+++ b/lib/libc/include/stdio.h
@@ -34,6 +34,7 @@
 #define __need_NULL
 #define __need_size_t
 #include <stddef.h>
+#include <unistd.h>
 #define __need_va_list
 #include <stdarg.h>
 
@@ -79,6 +80,7 @@ long ftell(FILE *stream);
 char *fgets(char *__restrict s, int size, FILE *__restrict stream);
 
 FILE *fopen(const char *__restrict path, const char *__restrict mode);
+int fseek(FILE *stream, long offset, int whence);
 int fclose(FILE *stream);
 
 int vsnprintf(char *s, size_t size, const char *fmt, va_list ap);
diff --git a/lib/libc/src/stdio/fseek.c b/lib/libc/src/stdio/fseek.c
new file mode 100644
index 0000000..b783081
--- /dev/null
+++ b/lib/libc/src/stdio/fseek.c
@@ -0,0 +1,42 @@
+/*
+ * Copyright (c) 2023-2025 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/errno.h>
+#include <stdio.h>
+#include <unistd.h>
+
+int
+fseek(FILE *stream, long offset, int whence)
+{
+    if (stream == NULL) {
+        return -EINVAL;
+    }
+
+    return lseek(stream->fd, offset, whence);
+}