Filesystem APIs

APIs to read and write files on the Dev Board Micro flash memory, based on littlefs.

For example, the following code demonstrates a variety of file operations (from examples/file_read_write/):

namespace coralmicro {
namespace {
void PrintDirectory(lfs_dir_t* dir, const char* path, int num_tabs) {
  constexpr int kMaxDepth = 3;
  if (num_tabs > kMaxDepth) {
    return;
  }

  lfs_info info;
  while (lfs_dir_read(Lfs(), dir, &info) > 0) {
    if (info.name[0] == '.') {
      continue;
    }

    for (int i = 0; i < num_tabs; ++i) {
      printf("\t");
    }

    printf("%s", info.name);

    if (info.type == LFS_TYPE_DIR) {
      char subpath[LFS_NAME_MAX];
      printf("/\r\n");
      lfs_dir_t subdir;
      snprintf(subpath, LFS_NAME_MAX, "%s/%s", path, info.name);
      CHECK(lfs_dir_open(Lfs(), &subdir, subpath) >= 0);
      PrintDirectory(&subdir, subpath, num_tabs + 1);
      CHECK(lfs_dir_close(Lfs(), &subdir) >= 0);
    } else {
      printf("\t\t%ld\r\n", info.size);
    }
  }
}

void PrintFilesystemContents() {
  lfs_dir_t root;
  CHECK(lfs_dir_open(Lfs(), &root, "/") >= 0);
  printf("Printing filesystem:\r\n");
  PrintDirectory(&root, "", 0);
  printf("Finished printing filesystem.\r\n");
  CHECK(lfs_dir_close(Lfs(), &root) >= 0);
}

bool Mkdir(const char* path) {
  int ret = lfs_mkdir(Lfs(), path);
  if (ret == LFS_ERR_EXIST) {
    printf("Error dir exists");
    return false;
  }
  return (ret == LFS_ERR_OK);
}

void Main() {
  printf("Begin filesystem example\r\n");
  // Turn on Status LED to show the board is on.
  LedSet(Led::kStatus, true);
  PrintFilesystemContents();

  printf("Creating some sample directories\r\n");
  CHECK(Mkdir("/dir"));
  CHECK(LfsDirExists("/dir"));
  constexpr char kFileStr[] = "HelloWorld";
  CHECK(LfsWriteFile("/dir/file", reinterpret_cast<const uint8_t*>(kFileStr),
                     std::strlen(kFileStr)));
  PrintFilesystemContents();
  std::string readstr;
  CHECK(LfsReadFile("/dir/file", &readstr));
  CHECK(readstr.length() == std::strlen(kFileStr));
  printf("File contents: %s\r\n", readstr.c_str());
  CHECK(lfs_remove(Lfs(), "/dir/file") >= 0);
  CHECK(lfs_remove(Lfs(), "/dir") >= 0);
  PrintFilesystemContents();
  printf("End filesystem example\r\n");
}

}  // namespace
}  // namespace coralmicro

extern "C" void app_main(void* param) {
  (void)param;
  coralmicro::Main();
  vTaskSuspend(nullptr);
}

[filesystem.h source]

namespace coralmicro

Functions

lfs_t *Lfs()¶

Returns littlefs instance to use with functions from lfs.h.

Returns

Pointer to littlefs instance.

bool LfsMakeDirs(const char *path)¶

Creates directory, similar to mkdir -p <path>.

Parameters

path – Directory path.

Returns

True upon success, false otherwise.

std::string LfsDirname(const char *path)¶

Returns the string up to, but not including, the final ‘/’ in the path.

Parameters

path – Path.

Returns

The string up to, but not including, the final ‘/’ in the path.

ssize_t LfsSize(const char *path)¶

Returns file size.

Parameters

path – File path.

Returns

File size in bytes.

bool LfsDirExists(const char *path)¶

Returns whether path exists and represents a directory.

Parameters

path – Path to check

Returns

True if path exists and represents a directory, false otherwise.

bool LfsFileExists(const char *path)¶

Returns whether path exists and represents a file.

Parameters

path – Path to check

Returns

true if path exists and represents a file, false otherwise.

bool LfsReadFile(const char *path, std::vector<uint8_t> *buf)¶

Reads content of the file and stores it in std::vector<uint8_t>.

Parameters

• path – File path to read.

• buf – Instance of std::vector<uint8_t> to read data in.

Returns

True upon success, false otherwise.

bool LfsReadFile(const char *path, std::string *str)¶

Reads content of the file and stores it in std::string.

Parameters

• path – File path to read.

• str – Instance of std::string to read data in.

Returns

True upon success, false otherwise.

size_t LfsReadFile(const char *path, uint8_t *buf, size_t size)¶

Reads content of the file and stores it in memory buffer.

Parameters

• path – File path to read.

• buf – Memory buffer to read data in.

• size – Memory buffer size.

Returns

Number of read bytes not exceeding size.

bool LfsWriteFile(const char *path, const uint8_t *buf, size_t size)¶

Writes content of the memory buffer to file.

Parameters

• path – File path to write.

• buf – Memory buffer to write data from.

• size – Memory buffer size.

Returns

True upon success, false otherwise.

bool LfsWriteFile(const char *path, const std::string &str)¶

Writes content of the string to file.

Parameters

• path – File path to write.

• str – String to write data from.

Returns

True upon success, false otherwise.