From 9e9f268562195d747cdeb7fcc6ad7f88c56db27d Mon Sep 17 00:00:00 2001
From: apio <blobs.trading@gmail.com>
Date: Sun, 12 Mar 2023 17:36:04 +0100
Subject: [PATCH] libc: Make fopen() parse the mode string

---
 libc/src/stdio.cpp | 26 +++++++++++++++++++++++---
 1 file changed, 23 insertions(+), 3 deletions(-)

diff --git a/libc/src/stdio.cpp b/libc/src/stdio.cpp
index be4210f1..e34f59d0 100644
--- a/libc/src/stdio.cpp
+++ b/libc/src/stdio.cpp
@@ -10,6 +10,23 @@
 
 FILE* stderr = nullptr;
 
+static int fopen_parse_mode(const char* mode)
+{
+    int result = 0;
+    switch (*mode)
+    {
+    case 'r': result |= O_RDONLY; break;
+    case 'w': result |= (O_WRONLY | O_CREAT | O_TRUNC); break;
+    case 'a': result |= (O_WRONLY | O_CREAT | O_APPEND); break;
+
+    default: errno = EINVAL; return -1;
+    }
+
+    if (strchr(mode, '+')) result |= O_RDWR;
+
+    return result;
+}
+
 extern "C"
 {
     int console_write(const char* str, size_t size)
@@ -18,10 +35,13 @@ extern "C"
         __errno_return(rc, int);
     }
 
-    FILE* fopen(const char* path, const char*)
+    FILE* fopen(const char* path, const char* mode)
     {
-        // FIXME: Parse the mode string.
-        int fd = open(path, O_RDWR);
+        int flags;
+
+        if ((flags = fopen_parse_mode(mode)) < 0) return nullptr;
+
+        int fd = open(path, flags, 0666);
         if (fd < 0) return nullptr;
 
         FILE* f = (FILE*)malloc(sizeof(FILE));