From 5c0104111d7b13fab7d96dfe9c38dd47155448db Mon Sep 17 00:00:00 2001
From: apio <blobs.trading@gmail.com>
Date: Sun, 12 Mar 2023 10:23:08 +0100
Subject: [PATCH] libc: Implement fopen, fclose, fread, feof, ferror, and
 clearerr

---
 libc/include/stdio.h | 25 ++++++++++++++---
 libc/src/stdio.cpp   | 65 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 86 insertions(+), 4 deletions(-)

diff --git a/libc/include/stdio.h b/libc/include/stdio.h
index a5a1d5df..942eecd8 100644
--- a/libc/include/stdio.h
+++ b/libc/include/stdio.h
@@ -8,10 +8,13 @@
 
 typedef struct
 {
-    int __unused;
+    int _fd;
+    int _err;
+    int _eof;
 } FILE;
 
 #define SEEK_SET 0
+#define EOF -1
 
 extern FILE* stderr;
 #define stderr stderr
@@ -23,15 +26,29 @@ extern "C"
 
     int fflush(FILE*);
 
-    FILE* fopen(const char*, const char*);
-    int fclose(FILE*);
+    /* Opens a file and binds a stream to it. */
+    FILE* fopen(const char* path, const char* mode);
+
+    /* Closes a file and frees up its stream. */
+    int fclose(FILE* stream);
+
+    /* Reads arbitrarily sized items from a stream. */
+    size_t fread(void* buf, size_t size, size_t nmemb, FILE* stream);
 
-    size_t fread(void*, size_t, size_t, FILE*);
     size_t fwrite(const void*, size_t, size_t, FILE*);
 
     int fseek(FILE*, long, int);
     long ftell(FILE*);
 
+    /* Returns whether the error indicator was set in stream. */
+    int ferror(FILE* stream);
+
+    /* Returns whether the end-of-file indicator was set in stream. */
+    int feof(FILE* stream);
+
+    /* Clears the error and end-of-file indicators in stream. */
+    void clearerr(FILE* stream);
+
     void setbuf(FILE*, char*);
 
     int fprintf(FILE*, const char*, ...);
diff --git a/libc/src/stdio.cpp b/libc/src/stdio.cpp
index ec90cac1..5305abbd 100644
--- a/libc/src/stdio.cpp
+++ b/libc/src/stdio.cpp
@@ -1,7 +1,9 @@
 #define _LUNA_SYSTEM_ERROR_EXTENSIONS
 #include <bits/errno-return.h>
+#include <fcntl.h>
 #include <luna/Format.h>
 #include <stdio.h>
+#include <stdlib.h>
 #include <string.h>
 #include <sys/syscall.h>
 #include <unistd.h>
@@ -16,6 +18,69 @@ extern "C"
         __errno_return(rc, int);
     }
 
+    FILE* fopen(const char* path, const char*)
+    {
+        // FIXME: Parse the mode string.
+        int fd = open(path, 0);
+        if (fd < 0) return nullptr;
+
+        FILE* f = (FILE*)malloc(sizeof(FILE));
+        if (!f)
+        {
+            close(fd);
+            return nullptr;
+        }
+
+        f->_fd = fd;
+        clearerr(f);
+
+        return f;
+    }
+
+    int fclose(FILE* stream)
+    {
+        if (close(stream->_fd) < 0) return EOF;
+
+        free(stream);
+
+        return 0;
+    }
+
+    size_t fread(void* buf, size_t size, size_t nmemb, FILE* stream)
+    {
+        if (size * nmemb == 0) return 0;
+
+        ssize_t nread = read(stream->_fd, buf, size * nmemb);
+
+        if (nread < 0)
+        {
+            stream->_err = 1;
+            return 0;
+        }
+        else if (nread == 0)
+        {
+            stream->_eof = 1;
+            return 0;
+        }
+        else
+            return (size_t)nread / size;
+    }
+
+    int ferror(FILE* stream)
+    {
+        return stream->_err;
+    }
+
+    int feof(FILE* stream)
+    {
+        return stream->_eof;
+    }
+
+    void clearerr(FILE* stream)
+    {
+        stream->_eof = stream->_err = 0;
+    }
+
     int vsnprintf(char* buf, size_t max, const char* format, va_list ap)
     {
         return (int)vstring_format(buf, max, format, ap);