Function write_file_atomic

src/pipeline/artifact.c:160–210

Write buffer to file atomically (write to tmp, rename). Returns 0 on success. */

/* Write buffer to file atomically (write to tmp, rename). Returns 0 on success. */
static int write_file_atomic(const char *path, const char *data, size_t len,
                             artifact_file_error_t *out_err) {
    file_error_clear(out_err);

    char tmp[CBM_SZ_4K];
    int n = snprintf(tmp, sizeof(tmp), "%s.tmp", path);
    if (n < 0 || (size_t)n >= sizeof(tmp)) {
        file_error_set(out_err, "path_too_long", 0);
        return CBM_NOT_FOUND;
    }

    FILE *fp = fopen(tmp, "wb");
    if (!fp) {
        file_error_set(out_err, "open_temp", errno);
        return CBM_NOT_FOUND;
    }

    size_t wr = fwrite(data, ART_NUL, len, fp);
    if (wr != len) {
        int saved_errno = ferror(fp) ? errno : 0;
        (void)fclose(fp);
        cbm_unlink(tmp);
        file_error_set(out_err, "write_temp", saved_errno);
        return CBM_NOT_FOUND;
    }

    if (fclose(fp) != 0) {
        int saved_errno = errno;
        cbm_unlink(tmp);
        file_error_set(out_err, "close_temp", saved_errno);
        return CBM_NOT_FOUND;
    }

#ifdef _WIN32
    /* MoveFileEx replace approach suggested by @Ayush7Ranjan in #492. */
    if (!MoveFileExA(tmp, path, MOVEFILE_REPLACE_EXISTING | MOVEFILE_WRITE_THROUGH)) {
        DWORD saved_error = GetLastError();
        cbm_unlink(tmp);
        file_error_set(out_err, "rename_temp", (int)saved_error);
        return CBM_NOT_FOUND;
    }
#else
    if (rename(tmp, path) != 0) {
        int saved_errno = errno;
        cbm_unlink(tmp);
        file_error_set(out_err, "rename_temp", saved_errno);
        return CBM_NOT_FOUND;
    }
#endif
    return 0;
}

#ifdef _WIN32
#define ARTIFACT_NULL_DEV "NUL"