libc: Implement the start of a FILE* API (the standard, portable C way of doing file stuff)

apps/src/init.c

@@ -1,4 +1,4 @@
-#include <fcntl.h>
+#include <errno.h>
 #include <luna.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -32,19 +32,21 @@ int main()
 
     printf("Opening %s for reading...\n", filename);
 
-    int fd = open(filename, O_RDONLY);
+    FILE* config = fopen(filename, "r");
-    if (fd < 0)
+    if (!config)
     {
-        perror("open");
+        perror("fopen");
         // return 1;
     }
 
     char buf[4096];
 
-    ssize_t nread = read(fd, buf, sizeof(buf));
+    size_t nread = fread(buf, sizeof(buf), 1, config);
-    if (nread < 0)
+    if (nread == 0 && errno != 0) // FIXME: looks like our only way of checking whether a zero-read is an error or eof
+                                  // right now is checking errno, since fread() does not differentiate between the two,
+                                  // and feof() and ferror() are not yet implemented
     {
-        perror("read");
+        perror("fread");
         // return 1;
     }
     else
@@ -56,9 +58,9 @@ int main()
         printf("%s", buf);
     }
 
-    if (close(fd) < 0)
+    if (fclose(config) < 0)
     {
-        perror("close");
+        perror("fclose");
         // return 1;
     }
 

libs/libc/include/bits/error.h

@@ -10,6 +10,7 @@
             errno = (int)(-rc);                                                                                        \
             return -1;                                                                                                 \
         }                                                                                                              \
+        errno = 0;                                                                                                     \
         return (type)rc;                                                                                               \
     } while (0)
 
@@ -20,6 +21,7 @@
             errno = (int)((rc)&0xff);                                                                                  \
             return (type)-1;                                                                                           \
         }                                                                                                              \
+        errno = 0;                                                                                                     \
         return (type)rc;                                                                                               \
     } while (0)
 

libs/libc/include/stdio.h

@@ -8,7 +8,7 @@
 
 typedef struct
 {
-    int unused;
+    int fd;
 } FILE;
 
 #ifdef __cplusplus

libs/libc/src/file.cpp

@@ -0,0 +1,61 @@
+#include <fcntl.h>
+#include <luna.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+extern "C"
+{
+    int fclose(FILE* stream)
+    {
+        int status = close(stream->fd);
+        free(stream); // We do not want to leak memory. man fclose(3) says that whether fclose() fails or not, any
+                      // further operation on the stream results in undefined behavior. So we are free to free the
+                      // stream.
+        return status;
+    }
+
+    int fflush(FILE*)
+    {
+        return 0; // FIXME: Implement buffered IO.
+    }
+
+    FILE* fopen(const char* pathname, const char*)
+    {
+        int fd = open(pathname, O_RDONLY); // FIXME: Use the mode string.
+        if (fd < 0) { return 0; }
+        FILE* stream = (FILE*)malloc(sizeof(FILE));
+        stream->fd = fd;
+        return stream;
+    }
+
+    size_t fread(void* buf, size_t size, size_t nmemb, FILE* stream)
+    {
+        ssize_t status = read(stream->fd, buf, size * nmemb);
+        if (status < 0)
+            return 0; // FIXME: The manual says that fread() does not differentiate between EOF and error, and that
+                      // ferror() and feof() should be called to determine such. So right now, we just mask the error,
+                      // until that is implemented.
+        return (size_t)status;
+    }
+
+    int fseek(FILE*, long, int)
+    {
+        NOT_IMPLEMENTED("fseek");
+    }
+
+    long ftell(FILE*)
+    {
+        NOT_IMPLEMENTED("ftell");
+    }
+
+    size_t fwrite(const void*, size_t, size_t, FILE*)
+    {
+        NOT_IMPLEMENTED("fwrite");
+    }
+
+    void setbuf(FILE*, char*)
+    {
+        NOT_IMPLEMENTED("setbuf");
+    }
+}

libs/libc/src/printf.cpp

@@ -329,4 +329,46 @@ extern "C"
             },
             max == 0 ? 0 : max - 1, ap);
     }
+
+    int snprintf(char* str, size_t max, const char* format, ...)
+    {
+        va_list ap;
+        va_start(ap, format);
+        int written = vsnprintf(str, max, format, ap);
+        va_end(ap);
+        return written;
+    }
+
+    int sprintf(char* str, const char* format, ...)
+    {
+        va_list ap;
+        va_start(ap, format);
+        int written = vsprintf(str, format, ap);
+        va_end(ap);
+        return written;
+    }
+
+    int printf(const char* format, ...)
+    {
+        va_list ap;
+        va_start(ap, format);
+        int written = vprintf(format, ap);
+        va_end(ap);
+        return written;
+    }
+
+    int fprintf(FILE*, const char* format, ...) // FIXME: Make fprintf print to the selected file instead of stdout.
+    {
+        va_list ap;
+        va_start(ap, format);
+        int written = vprintf(format, ap);
+        va_end(ap);
+        return written;
+    }
+
+    int vfprintf(FILE*, const char* format,
+                 va_list ap) // FIXME: Make vfprintf print to the selected file instead of stdout.
+    {
+        return vprintf(format, ap);
+    }
 }

libs/libc/src/stdio.cpp

@@ -8,51 +8,6 @@
 
 extern "C"
 {
-    int fclose(FILE*)
-    {
-        NOT_IMPLEMENTED("fclose");
-    }
-    int fflush(FILE*)
-    {
-        NOT_IMPLEMENTED("fflush");
-    }
-    FILE* fopen(const char*, const char*)
-    {
-        NOT_IMPLEMENTED("fopen");
-    }
-    int fprintf(FILE*, const char* format, ...) // FIXME: Make fprintf print to the selected file instead of stdout.
-    {
-        va_list ap;
-        va_start(ap, format);
-        int written = vprintf(format, ap);
-        va_end(ap);
-        return written;
-    }
-    size_t fread(void*, size_t, size_t, FILE*)
-    {
-        NOT_IMPLEMENTED("fread");
-    }
-    int fseek(FILE*, long, int)
-    {
-        NOT_IMPLEMENTED("fseek");
-    }
-    long ftell(FILE*)
-    {
-        NOT_IMPLEMENTED("ftell");
-    }
-    size_t fwrite(const void*, size_t, size_t, FILE*)
-    {
-        NOT_IMPLEMENTED("fwrite");
-    }
-    void setbuf(FILE*, char*)
-    {
-        NOT_IMPLEMENTED("setbuf");
-    }
-    int vfprintf(FILE*, const char* format,
-                 va_list ap) // FIXME: Make vfprintf print to the selected file instead of stdout.
-    {
-        return vprintf(format, ap);
-    }
     int puts(const char* s)
     {
         long nwritten = syscall(SYS_write, s, strlen(s));
@@ -60,33 +15,11 @@ extern "C"
         nwritten += syscall(SYS_write, "\n", 1);
         return (int)nwritten;
     }
-    int snprintf(char* str, size_t max, const char* format, ...)
-    {
-        va_list ap;
-        va_start(ap, format);
-        int written = vsnprintf(str, max, format, ap);
-        va_end(ap);
-        return written;
-    }
-    int sprintf(char* str, const char* format, ...)
-    {
-        va_list ap;
-        va_start(ap, format);
-        int written = vsprintf(str, format, ap);
-        va_end(ap);
-        return written;
-    }
-    int printf(const char* format, ...)
-    {
-        va_list ap;
-        va_start(ap, format);
-        int written = vprintf(format, ap);
-        va_end(ap);
-        return written;
-    }
     void perror(const char* s) // FIXME: Print to stderr, whenever we have an stderr.
     {
+        int savederr =
+            errno; // This was necessary before, but even more now since we clear errno on successful syscalls now.
         if (s && *s) { printf("%s: ", s); }
-        printf("%s\n", strerror(errno));
+        printf("%s\n", strerror(savederr));
     }
 }