feat(iso): add open function

k/iso.c

@@ -0,0 +1,73 @@
+#include <k/iso9660.h>
+
+#include <k/types.h>
+
+#include "atapi.h"
+#include "fd.h"
+#include "iso.h"
+#include "stdio.h"
+#include "string.h"
+
+static u32 get_filename_length(const char *path, u32 *index)
+{
+    u32 len = 0;
+    for (; path[*index]; ++(*index))
+    {
+        if (path[*index] != '/')
+            ++len;
+        else {
+            while (path[*index] == '/')
+                ++(*index);
+            break;
+        }
+    }
+
+    return len;
+}
+
+int open(const char *pathname, int flags)
+{
+    if (flags != O_RDONLY)
+        return -1;
+
+    struct iso_prim_voldesc *iso_prim_block = read_block(ISO_PRIM_VOLDESC_BLOCK);
+    if (strncmp(iso_prim_block->std_identifier, "CD001", 5))
+        return -1;
+
+    struct iso_dir *root = &iso_prim_block->root_dir;
+    struct iso_dir *curr = read_block(root->data_blk.le);
+
+    u32 index = 0;
+    while (pathname[index] == '/')
+        ++index;
+
+    for (int depth = 0; depth < MAX_DIR_DEPTH; ++depth)
+    {
+        char found = 0;
+        u32 start = index;
+        u32 length = get_filename_length(pathname, &index);
+
+        // we found the file
+        if (!length)
+            return register_fd(curr->data_blk.le);
+
+        // iteration for one directory
+        while (curr->dir_size != 0)
+        {
+            if (length == curr->idf_len &&
+                    !strncmp(pathname + start, curr->idf, length))
+            {
+                curr = read_block(curr->data_blk.le);
+                found = 1;
+                break;
+            }
+            else
+                curr = (void *)curr + curr->dir_size;
+        }
+
+        if (!found)
+            return -1;
+    }
+
+    return -1;
+}

k/iso.h

@@ -0,0 +1,10 @@
+#ifndef ISO_H
+#define ISO_H
+
+#include <k/types.h>
+
+#define O_RDONLY    0
+
+int open(const char *path, int flags);
+
+#endif /* !ISO_H */