Writes `len` bytes of reader progress to ` /progress.bin` without ever leaving the canonical file half-written. The bytes go to a temporary `progress.bin.tmp` first; only once that is fully written and closed is it renamed over progress.bin. An interrupted write (power loss or a crash mid-SPI) therefore damages only the throwaway temp file. Previously a truncate-in-place write that was
| 30 | // |
| 31 | // Returns true only if the new progress.bin is fully in place. |
| 32 | inline bool writeAtomic(const std::string& cachePath, const uint8_t* data, size_t len) { |
| 33 | const std::string finalPath = cachePath + "/progress.bin"; |
| 34 | const std::string tmpPath = cachePath + "/progress.bin.tmp"; |
| 35 | |
| 36 | { |
| 37 | HalFile f; |
| 38 | if (!Storage.openFileForWrite("PRG", tmpPath, f)) { |
| 39 | LOG_ERR("PRG", "Could not open temp progress file for write: %s", tmpPath.c_str()); |
| 40 | return false; |
| 41 | } |
| 42 | const size_t written = f.write(data, len); |
| 43 | if (written != len) { |
| 44 | LOG_ERR("PRG", "Short write saving progress to %s: %u/%u bytes", tmpPath.c_str(), (unsigned)written, |
| 45 | (unsigned)len); |
| 46 | return false; |
| 47 | } |
| 48 | f.flush(); |
| 49 | // f (the temp file) is closed at scope exit (DESTRUCTOR_CLOSES_FILE=1) before |
| 50 | // the rename below -- SdFat must not rename a path that still has an open FsFile. |
| 51 | } |
| 52 | |
| 53 | // SdFat's rename does not overwrite an existing destination, so drop the old |
| 54 | // canonical file first. The brief window where neither file exists reads as |
| 55 | // "no saved progress" on next launch -- never a corrupt, unclearable file. |
| 56 | Storage.remove(finalPath.c_str()); |
| 57 | if (!Storage.rename(tmpPath.c_str(), finalPath.c_str())) { |
| 58 | LOG_ERR("PRG", "Failed to rename temp progress into place: %s", finalPath.c_str()); |
| 59 | return false; |
| 60 | } |
| 61 | return true; |
| 62 | } |
| 63 | |
| 64 | } // namespace ProgressFile |
no test coverage detected