text: /*
   * HTTP file download
   * 
   * Copyright (c) 2016-2017 Fabrice Bellard
   *
   * Permission is hereby granted, free of charge, to any person obtaining a copy
   * of this software and associated documentation files (the "Software"), to deal
   * in the Software without restriction, including without limitation the rights
   * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
   * copies of the Software, and to permit persons to whom the Software is
   * furnished to do so, subject to the following conditions:
   *
   * The above copyright notice and this permission notice shall be included in
   * all copies or substantial portions of the Software.
   *
   * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
   * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
   * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
   * THE SOFTWARE.
   */
  #if defined(EMSCRIPTEN)
  #define USE_BUILTIN_CRYPTO
  #endif
  
  #ifdef USE_BUILTIN_CRYPTO
  #include "aes.h"
  #include "sha256.h"
  #else
  #include <openssl/aes.h>
  #include <openssl/sha.h>
  #include <openssl/evp.h>
  #endif
  #ifdef _WIN32
  #include <winsock2.h>
  #endif
  
  #define LOG() printf("%s:%d\n", __func__, __LINE__)
  
  /* XHR */
  
  /* err < 0: error (no data provided)
     err = 0: end of transfer (data can be provided too)
     err = 1: data chunk
  */
  typedef void WGetWriteCallback(void *opaque, int err, void *data, size_t size);
  typedef size_t WGetReadCallback(void *opaque, void *data, size_t size);
  typedef struct XHRState XHRState;
  
  XHRState *fs_wget(const char *url, const char *user, const char *password,
                    void *opaque, WGetWriteCallback *cb, BOOL single_write);
  void fs_wget_free(XHRState *s);
  
  void fs_wget_init(void);
  void fs_wget_end(void);
  
  #ifndef EMSCRIPTEN
  typedef BOOL FSNetEventLoopCompletionFunc(void *opaque);
  void fs_net_set_fdset(int *pfd_max, fd_set *rfds, fd_set *wfds, fd_set *efds,
                        int *ptimeout);
  void fs_net_event_loop(FSNetEventLoopCompletionFunc *cb, void *opaque);
  #endif
  
  /* crypto */
  
  extern const uint8_t encrypted_file_magic[4];
  
  typedef int DecryptFileCB(void *opaque, const uint8_t *data, size_t len);
  typedef struct DecryptFileState DecryptFileState;
  
  DecryptFileState *decrypt_file_init(AES_KEY *aes_state,
                                      DecryptFileCB *write_cb,
                                      void *opaque);
  int decrypt_file(DecryptFileState *s, const uint8_t *data,
                   size_t size);
  int decrypt_file_flush(DecryptFileState *s);
  void decrypt_file_end(DecryptFileState *s);
  
  void pbkdf2_hmac_sha256(const uint8_t *pwd, int pwd_len,
                          const uint8_t *salt, int salt_len,
                          int iter, int key_len, uint8_t *out);
  
  /* XHR file */
  
  typedef void FSWGetFileCB(FSDevice *fs, FSFile *f, int64_t size, void *opaque);
  
  void fs_wget_file2(FSDevice *fs, FSFile *f, const char *url,
                     const char *user, const char *password,
                     FSFile *posted_file, uint64_t post_data_len,
                     FSWGetFileCB *cb, void *opaque,
                     AES_KEY *aes_state);
  