From 23d859e793cc169974d66ea5ef991910f56bb4b6 Mon Sep 17 00:00:00 2001
From: bumbread <thebumboni@gmail.com>
Date: Fri, 29 Jul 2022 01:16:23 +1100
Subject: [PATCH] Stream positioning funcs

---
 inc/stdio.h      |  2 +-
 src/_win/stdio.c | 17 +++++++++++++++--
 2 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/inc/stdio.h b/inc/stdio.h
index 4560745..852ae2e 100644
--- a/inc/stdio.h
+++ b/inc/stdio.h
@@ -43,9 +43,9 @@ typedef struct {
 
 #define L_tmpnam FILENAME_MAX
 
+#define SEEK_SET 0
 #define SEEK_CUR 1
 #define SEEK_END 2
-#define SEEK_SET 0
 
 #ifdef _os_win
     #define TMP_MAX  SHORT_MAX
diff --git a/src/_win/stdio.c b/src/_win/stdio.c
index 4739233..347648d 100644
--- a/src/_win/stdio.c
+++ b/src/_win/stdio.c
@@ -426,6 +426,13 @@ int fgetpos(FILE *restrict stream, fpos_t *restrict pos) {
 }
 
 int fseek(FILE *stream, long int offset, int whence) {
+    // Note(bumbread): the SEEK_SET, SEEK_CUR and SEEK_END are defined to match
+    // Windows' constants, so no conversion is requierd between them.
+    LONG pos_hi = 0;
+    DWORD pos_lo = SetFilePointer(stream->handle, offset, &pos_hi, whence);
+    if(pos_lo == INVALID_SET_FILE_POINTER) {
+        return -1L;
+    }
     return 0;
 }
 
@@ -441,11 +448,17 @@ int fsetpos(FILE *stream, const fpos_t *pos) {
 }
 
 long int ftell(FILE *stream) {
-    return 0;
+    LONG pos_hi = 0;
+    DWORD pos_lo = SetFilePointer(stream->handle, 0, &pos_hi, FILE_CURRENT);
+    if(pos_lo == INVALID_SET_FILE_POINTER) {
+        return -1L;
+    }
+    int64_t offset = ((int64_t)pos_hi << 32) | (int64_t)pos_lo;
+    return offset;
 }
 
 void rewind(FILE *stream) {
-
+    fseek(stream, 0, SEEK_SET);
 }
 
 int getchar(void) {