slate32/src/host/providers_fs.cpp

#include <SD.h>

#include "providers.h"

namespace slate {
namespace {

using esp32lua::Status;

// Streamed rather than slurped: holding a whole module as one buffer needs that many bytes
// contiguous, and once WiFi is up the largest free block is far below the free heap.
class SdReader : public esp32lua::FileReader {
 public:
  explicit SdReader(File file) : file(file) {}
  ~SdReader() override {
    if (file) file.close();
  }
  int32_t read(char* out, int32_t maxBytes) override {
    return file.read(reinterpret_cast<uint8_t*>(out), maxBytes);
  }

 private:
  File file;
};

Status listEntries(const std::string& path, bool directories, std::vector<std::string>& names) {
  File dir = SD.open(path.c_str());
  if (!dir || !dir.isDirectory()) {
    if (dir) dir.close();
    return Status::failure("not a directory");
  }
  for (File entry = dir.openNextFile(); entry; entry = dir.openNextFile()) {
    if (entry.isDirectory() == directories && entry.name()[0] != '.') names.push_back(entry.name());
    entry.close();
  }
  dir.close();
  std::sort(names.begin(), names.end());
  return Status::success();
}

bool removeRecursive(const String& path) {
  File entry = SD.open(path);
  if (!entry) return false;
  if (!entry.isDirectory()) {
    entry.close();
    return SD.remove(path);
  }
  for (File child = entry.openNextFile(); child; child = entry.openNextFile()) {
    const String childPath = path + "/" + child.name();
    const bool isDirectory = child.isDirectory();
    child.close();
    if (!(isDirectory ? removeRecursive(childPath) : SD.remove(childPath))) {
      entry.close();
      return false;
    }
  }
  entry.close();
  return SD.rmdir(path);
}

}  // namespace

esp32lua::FileReader* Fs::openRead(const std::string& path) {
  // Probed first: a missed SD.open logs a VFS error, and the module searcher misses by design.
  if (!SD.exists(path.c_str())) return nullptr;
  File file = SD.open(path.c_str());
  if (!file || file.isDirectory()) {
    if (file) file.close();
    return nullptr;
  }
  return new SdReader(file);
}

bool Fs::exists(const std::string& path) const { return SD.exists(path.c_str()); }

Status Fs::fileSize(const std::string& path, int32_t& size) const {
  File file = SD.open(path.c_str());
  if (!file || file.isDirectory()) {
    if (file) file.close();
    return Status::failure("not a file");
  }
  size = static_cast<int32_t>(file.size());
  file.close();
  return Status::success();
}

Status Fs::listDirs(const std::string& path, std::vector<std::string>& names) const {
  return listEntries(path, true, names);
}

Status Fs::listFiles(const std::string& path, std::vector<std::string>& names) const {
  return listEntries(path, false, names);
}

Status Fs::mkdir(const std::string& path) {
  if (SD.exists(path.c_str())) return Status::success();
  return SD.mkdir(path.c_str()) ? Status::success() : Status::failure("cannot create directory");
}

Status Fs::readFile(const std::string& path, int32_t maxBytes, std::string& content) const {
  File file = SD.open(path.c_str());
  if (!file || file.isDirectory()) {
    if (file) file.close();
    return Status::failure("not a file");
  }
  const size_t size = file.size();
  if (size > static_cast<size_t>(maxBytes)) {
    file.close();
    return Status::failure("file exceeds maxBytes");
  }
  content.resize(size);
  const size_t read = size ? file.read(reinterpret_cast<uint8_t*>(&content[0]), size) : 0;
  file.close();
  if (read != size) return Status::failure("short read");
  return Status::success();
}

Status Fs::readLineAt(const std::string& path, int32_t offset, int32_t maxBytes, bool& found, std::string& line,
                      int32_t& nextOffset) const {
  File file = SD.open(path.c_str());
  if (!file || file.isDirectory()) {
    if (file) file.close();
    return Status::failure("not a file");
  }
  if (!file.seek(offset)) {
    file.close();
    return Status::failure("cannot seek");
  }
  if (offset > 0) {
    // A mid-line offset advances to the next line, so a caller can resume from any byte.
    while (file.available() && file.peek() != '\n') file.read();
    if (file.available()) file.read();
  }
  if (!file.available()) {
    file.close();
    found = false;
    return Status::success();
  }

  line.clear();
  while (file.available()) {
    const int c = file.read();
    if (c == '\n') break;
    if (c != '\r') line.push_back(static_cast<char>(c));
    if (static_cast<int32_t>(line.size()) > maxBytes) {
      file.close();
      return Status::failure("line exceeds maxBytes");
    }
  }
  nextOffset = static_cast<int32_t>(file.position());
  file.close();
  found = true;
  return Status::success();
}

Status Fs::remove(const std::string& path) {
  return SD.remove(path.c_str()) ? Status::success() : Status::failure("cannot remove");
}

Status Fs::removeTree(const std::string& path) {
  return removeRecursive(String(path.c_str())) ? Status::success() : Status::failure("cannot remove tree");
}

Status Fs::rename(const std::string& source, const std::string& destination) {
  if (SD.exists(destination.c_str())) return Status::failure("destination exists");
  return SD.rename(source.c_str(), destination.c_str()) ? Status::success() : Status::failure("cannot rename");
}

// Written to a temporary first: a half-written file that replaced a good one is worse than a
// failed write that left the old contents alone.
Status Fs::writeFile(const std::string& path, const std::string& content) {
  const String target(path.c_str());
  const String temporary = target + ".tmp";
  SD.remove(temporary);

  File file = SD.open(temporary, FILE_WRITE);
  if (!file) return Status::failure("cannot open for writing");
  const size_t written = content.empty() ? 0 : file.write(reinterpret_cast<const uint8_t*>(content.data()),
                                                          content.size());
  file.close();
  if (written != content.size()) {
    SD.remove(temporary);
    return Status::failure("short write");
  }
  SD.remove(target);
  if (!SD.rename(temporary, target)) {
    SD.remove(temporary);
    return Status::failure("cannot replace destination");
  }
  return Status::success();
}

}  // namespace slate