syscalls needed for doom (tell/eof/draw_fb) + minor fixes, compiler shut up etc

src/syscall/files.c

@@ -0,0 +1,252 @@
+/*
+ * @author  xamidev <xamidev@riseup.net>
+ * @brief   File-related system calls
+ * @license GPL-3.0-only
+ */
+
+#include <stddef.h>
+#include <kernel.h>
+#include <config.h>
+#include <sched/process.h>
+#include <string/string.h>
+#include <fs/initfs.h>
+#include <io/kbd/ps2.h>
+
+extern struct process* current_process;
+
+/*
+ * normalize_path - remove leading slashes from a path
+ * @path: path to normalize
+ *
+ * Return:
+ * %path - normalized path
+ * %NULL - if bad argument
+ */
+static const char* normalize_path(const char* path)
+{
+    if (!path) return NULL;
+
+    while (*path == '/') {
+        path++;
+    }
+
+    return path;
+}
+
+/*
+ * sys_open - Open a file
+ * @filename: Absolute path to file
+ * @flags:    (Not implemented)
+ *
+ * This system call opens a file in read-only mode,
+ * because of the TAR filesystem.
+ *
+ * Return:
+ * %fd - file descriptor refering to file
+ * On error, a negative number representing the error code is returned.
+ */
+int sys_open(const char* filename, int flags)
+{
+    // TODO: support flags (right now everything is read only, O_RDONLY)
+    (void)flags; // gcc shut up
+    const char* path = normalize_path(filename);
+
+    if (tar_exists(path) < 0) {
+        return -ENOENT; // file doesn't exist..
+    }
+    // file exists here!
+    if (current_process->next_free_fd >= FDT_MAX) {
+        return -EMFILE;
+    }
+    int fd = current_process->next_free_fd++;
+    current_process->fdt[fd].fd = fd;
+    current_process->fdt[fd].open = true;
+    current_process->fdt[fd].cursor = 0;
+    strncpy(current_process->fdt[fd].filename, path, PROCESS_NAME_MAX - 1);
+    return fd;
+}
+
+/*
+ * sys_close - Close a file
+ * @fd: file descriptor
+ *
+ * This system call closes the file referred to by
+ * the file descriptor @fd.
+ *
+ * Return:
+ * %0       - file closed
+ * %-EBADFD - bad file descriptor
+ */
+int sys_close(int fd)
+{
+    if (fd < 0 || fd >= FDT_MAX) {
+        return -EBADFD;
+    }
+
+    if (!current_process->fdt[fd].open) {
+        return -EBADFD; // FD not opened in the first place
+    }
+
+    current_process->fdt[fd].open = false;
+    current_process->fdt[fd].filename[0] = '\0';
+    current_process->fdt[fd].cursor = 0;
+    return 0;
+}
+
+/*
+ * sys_lseek - reposition file cursor
+ * @fd:     file descriptor referring to file
+ * @offset: byte amount to be used according to @whence
+ * @whence: resposition directive
+ *
+ * This system call repositions the cursor for @fd by @offset,
+ * from somewhere in the file, depending on the value of @whence:
+ * SEEK_SET (0) -> from the beginning
+ * SEEK_CUR (1) -> from the actual value of the cursor
+ * SEEK_END (2) -> from the end of the file
+ *
+ * Return:
+ * %new_cursor - the new cursor value
+ * On error, a negative value corresponding to an error code is returned.
+ */
+int sys_lseek(int fd, int offset, int whence)
+{
+    if (fd < 0 || fd >= FDT_MAX) {
+        return -EBADFD;
+    }
+    if (!current_process->fdt[fd].open) {
+        return -EBADFD;
+    }
+
+    int filesize = tar_exists(current_process->fdt[fd].filename);
+    if (filesize < 0) {
+        return -ENOENT;
+    }
+
+    int cursor = current_process->fdt[fd].cursor;
+    int base;
+    switch (whence) {
+        case SEEK_SET: base = 0; break;
+        case SEEK_CUR: base = cursor; break;
+        case SEEK_END: base = filesize; break;
+        default: return -EINVAL;
+    }
+
+    int new_cursor = base + offset;
+    if (new_cursor < 0) new_cursor = 0;
+    if (new_cursor > filesize) new_cursor = filesize;
+
+    current_process->fdt[fd].cursor = new_cursor;
+    return new_cursor;
+}
+
+/*
+ * sys_tell - Get cursor position for a file
+ * @fd: file descriptor to use
+ *
+ * Return:
+ * %cursor - cursor position of the file descriptor
+ * On error, a negative value with the corresponding error code is set.
+ */
+int sys_tell(int fd)
+{
+    if (fd < 0 || fd >= FDT_MAX) {
+        return -EBADFD;
+    }
+    if (!current_process->fdt[fd].open) {
+        return -EBADFD;
+    }
+    return current_process->fdt[fd].cursor;
+}
+
+/*
+ * sys_eof - Are we at the end of the file yet?
+ * @fd: file descriptor to use
+ *
+ * This function determines if the cursor for the
+ * file descriptor @fd is at or past the end of
+ * the file it refers to.
+ *
+ * Return:
+ * %>0 - we are at or past EOF
+ * %0  - not yet (still have bytes to read)
+ */
+int sys_eof(int fd)
+{
+    if (fd < 0 || fd >= FDT_MAX) {
+        return -EBADFD;
+    }
+    if (!current_process->fdt[fd].open) {
+        return -EBADFD;
+    }
+
+    int filesize = tar_exists(current_process->fdt[fd].filename);
+    if (filesize < 0) {
+        return -ENOENT;
+    }
+
+    return current_process->fdt[fd].cursor >= (uint64_t)filesize;
+}
+
+/*
+ * sys_read - read from an open file
+ * @fd:    file descriptor to use
+ * @buf:   out buffer for read data
+ * @count: amount of bytes to read
+ *
+ * Return:
+ * %sz - amount of bytes read (on success)
+ * On error, a negative value with an error code is returned.
+ */
+int sys_read(unsigned int fd, char* buf, size_t count)
+{
+    size_t i;
+    switch (fd) {
+        case 0: //read from stdin (keyboard)
+            for (i=0; i<count; i++) {
+                buf[i] = keyboard_getchar();
+            }
+            return i;
+        case 1: // from stdout
+        case 2: // from stderr
+            return -EBADFD;
+        default: // from an open file?
+            if (current_process->fdt[fd].open == false) {
+                return -EBADFD; // File descriptor wasn't open
+            }
+            // Here fd refers to a valid opened file..
+            int sz = tar_read(current_process->fdt[fd].filename, buf, count,
+                            current_process->fdt[fd].cursor);
+            if (sz == 0) {
+                return -ENOENT;
+            } else {
+                current_process->fdt[fd].cursor += sz;
+                return sz;
+            }
+    }
+    return -EBADFD;
+}
+
+/*
+ * sys_write - write to a file
+ * @fd:    file descriptor to write to
+ * @buf:   buffer of bytes to write
+ * @count: number of bytes to write
+ *
+ * Return:
+ * %count - number of bytes written
+ * On error, a negative value with corresponding error code is returned.
+ */
+int sys_write(unsigned int fd, const char* buf, size_t count)
+{
+    switch (fd) {
+        case 1: //stdout
+        case 2: //stderr
+            for (size_t i=0; i<count; i++) {
+                internal_putc(buf[i], NULL);
+            }
+            return count;
+        default:
+            return -EBADFD;
+    }
+}