VFS mountpoint backing device system

kernel/fs/tarfs.c

@@ -0,0 +1,142 @@
+#include <fs/path.h>
+#include <fs/tarfs.h>
+#include <fs/vfs.h>
+#include <libk/align.h>
+#include <libk/minmax.h>
+#include <libk/std.h>
+#include <libk/string.h>
+#include <limine/requests.h>
+#include <m/fs_desc_buffer.h>
+#include <m/path.h>
+#include <m/status.h>
+#include <m/xdrv_device.h>
+#include <mm/liballoc.h>
+#include <sys/debug.h>
+
+static struct tar_file* tar_get_file (struct tarfs* tarfs, const char* filename) {
+  for (size_t i = 0; i < TARFS_FILES_MAX; i++) {
+    if ((tarfs->tarfs_files[i].header != NULL) &&
+        (strncmp (tarfs->tarfs_files[i].header->filename, filename, MAX_PATH) == 0))
+      return &tarfs->tarfs_files[i];
+  }
+  return NULL;
+}
+
+static size_t tar_get_size (uint8_t* in) {
+  size_t size = 0;
+  size_t j;
+  size_t count = 1;
+
+  for (j = 11; j > 0; j--, count *= 8)
+    size += ((in[j - 1] - '0') * count);
+
+  return size;
+}
+
+static size_t tar_parse (struct tarfs* tarfs, uint8_t* addr) {
+  size_t i;
+
+  for (i = 0; i < TARFS_FILES_MAX; i++) {
+    struct tar_header* hdr = (struct tar_header*)addr;
+
+    if (hdr->filename[0] == '\0')
+      break;
+
+    size_t size = tar_get_size (hdr->size);
+
+    tarfs->tarfs_files[i].header = hdr;
+    tarfs->tarfs_files[i].content = (uint8_t*)((uintptr_t)hdr + 512);
+    tarfs->tarfs_files[i].size = tar_get_size ((uint8_t*)hdr->size);
+
+    addr += 512 + ((size + 511) & ~511);
+  }
+
+  return i;
+}
+
+int tarfs_mount (struct vfs_mountpoint* mountpoint, struct device_op_ctx* op_ctx) {
+  struct tarfs* tarfs = malloc (sizeof (*tarfs));
+
+  if (tarfs == NULL)
+    return -ST_OOM_ERROR;
+
+  memset (tarfs, 0, sizeof (*tarfs));
+
+  mountpoint->udata = tarfs;
+
+  struct device* back_device = mountpoint->back_device;
+  size_t total_size;
+  int ret;
+
+  spin_lock (&back_device->lock);
+
+  ret = back_device->ops[XDRV_GET_SIZE](back_device, op_ctx, &total_size, NULL, NULL, NULL);
+  if (ret < 0) {
+    spin_unlock (&back_device->lock);
+    free (mountpoint->udata);
+    return ret;
+  }
+
+  uint8_t* buffer = malloc (total_size);
+
+  if (buffer == NULL) {
+    spin_unlock (&back_device->lock);
+    free (mountpoint->udata);
+    return ret;
+  }
+
+  size_t pos = 0;
+  ret = back_device->ops[XDRV_READ](back_device, op_ctx, &pos, &total_size, buffer, NULL);
+
+  spin_unlock (&back_device->lock);
+
+  if (ret < 0) {
+    free (buffer);
+    return ret;
+  }
+
+  tarfs->buffer = buffer;
+
+  tar_parse (tarfs, tarfs->buffer);
+
+  return ret;
+}
+
+int tarfs_describe (struct vfs_mountpoint* mountpoint, const char* path,
+                    struct fs_desc_buffer* desc) {
+  (void)mountpoint;
+
+  const char* filename = path_basename (path);
+
+  if (filename == NULL)
+    return -ST_BAD_PATH;
+
+  struct tar_file* file = tar_get_file ((struct tarfs*)mountpoint->udata, filename);
+
+  if (file == NULL)
+    return -ST_NOT_FOUND;
+
+  desc->size = file->size;
+  desc->type = FS_FILE;
+
+  return ST_OK;
+}
+
+int tarfs_read (struct vfs_mountpoint* mountpoint, const char* path, uint8_t* buffer, size_t off,
+                size_t size) {
+  (void)mountpoint;
+
+  const char* filename = path_basename (path);
+
+  if (filename == NULL)
+    return -ST_BAD_PATH;
+
+  struct tar_file* file = tar_get_file ((struct tarfs*)mountpoint->udata, filename);
+
+  if (file == NULL)
+    return -ST_NOT_FOUND;
+
+  memcpy (buffer, (void*)((uintptr_t)file->content + off), min (size, file->size));
+
+  return ST_OK;
+}