2
0

BIO_ctrl.pod 5.1 KB

123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136
  1. =pod
  2. =head1 NAME
  3. BIO_ctrl, BIO_callback_ctrl, BIO_ptr_ctrl, BIO_int_ctrl, BIO_reset,
  4. BIO_seek, BIO_tell, BIO_flush, BIO_eof, BIO_set_close, BIO_get_close,
  5. BIO_pending, BIO_wpending, BIO_ctrl_pending, BIO_ctrl_wpending,
  6. BIO_get_info_callback, BIO_set_info_callback, BIO_info_cb
  7. - BIO control operations
  8. =head1 SYNOPSIS
  9. #include <openssl/bio.h>
  10. typedef int BIO_info_cb(BIO *b, int state, int res);
  11. long BIO_ctrl(BIO *bp, int cmd, long larg, void *parg);
  12. long BIO_callback_ctrl(BIO *b, int cmd, BIO_info_cb *cb);
  13. char *BIO_ptr_ctrl(BIO *bp, int cmd, long larg);
  14. long BIO_int_ctrl(BIO *bp, int cmd, long larg, int iarg);
  15. int BIO_reset(BIO *b);
  16. int BIO_seek(BIO *b, int ofs);
  17. int BIO_tell(BIO *b);
  18. int BIO_flush(BIO *b);
  19. int BIO_eof(BIO *b);
  20. int BIO_set_close(BIO *b, long flag);
  21. int BIO_get_close(BIO *b);
  22. int BIO_pending(BIO *b);
  23. int BIO_wpending(BIO *b);
  24. size_t BIO_ctrl_pending(BIO *b);
  25. size_t BIO_ctrl_wpending(BIO *b);
  26. int BIO_get_info_callback(BIO *b, BIO_info_cb **cbp);
  27. int BIO_set_info_callback(BIO *b, BIO_info_cb *cb);
  28. =head1 DESCRIPTION
  29. BIO_ctrl(), BIO_callback_ctrl(), BIO_ptr_ctrl() and BIO_int_ctrl()
  30. are BIO "control" operations taking arguments of various types.
  31. These functions are not normally called directly, various macros
  32. are used instead. The standard macros are described below, macros
  33. specific to a particular type of BIO are described in the specific
  34. BIOs manual page as well as any special features of the standard
  35. calls.
  36. BIO_reset() typically resets a BIO to some initial state, in the case
  37. of file related BIOs for example it rewinds the file pointer to the
  38. start of the file.
  39. BIO_seek() resets a file related BIO's (that is file descriptor and
  40. FILE BIOs) file position pointer to B<ofs> bytes from start of file.
  41. BIO_tell() returns the current file position of a file related BIO.
  42. BIO_flush() normally writes out any internally buffered data, in some
  43. cases it is used to signal EOF and that no more data will be written.
  44. BIO_eof() returns 1 if the BIO has read EOF, the precise meaning of
  45. "EOF" varies according to the BIO type.
  46. BIO_set_close() sets the BIO B<b> close flag to B<flag>. B<flag> can
  47. take the value BIO_CLOSE or BIO_NOCLOSE. Typically BIO_CLOSE is used
  48. in a source/sink BIO to indicate that the underlying I/O stream should
  49. be closed when the BIO is freed.
  50. BIO_get_close() returns the BIOs close flag.
  51. BIO_pending(), BIO_ctrl_pending(), BIO_wpending() and BIO_ctrl_wpending()
  52. return the number of pending characters in the BIOs read and write buffers.
  53. Not all BIOs support these calls. BIO_ctrl_pending() and BIO_ctrl_wpending()
  54. return a size_t type and are functions, BIO_pending() and BIO_wpending() are
  55. macros which call BIO_ctrl().
  56. =head1 RETURN VALUES
  57. BIO_reset() normally returns 1 for success and 0 or -1 for failure. File
  58. BIOs are an exception, they return 0 for success and -1 for failure.
  59. BIO_seek() and BIO_tell() both return the current file position on success
  60. and -1 for failure, except file BIOs which for BIO_seek() always return 0
  61. for success and -1 for failure.
  62. BIO_flush() returns 1 for success and 0 or -1 for failure.
  63. BIO_eof() returns 1 if EOF has been reached 0 otherwise.
  64. BIO_set_close() always returns 1.
  65. BIO_get_close() returns the close flag value: BIO_CLOSE or BIO_NOCLOSE.
  66. BIO_pending(), BIO_ctrl_pending(), BIO_wpending() and BIO_ctrl_wpending()
  67. return the amount of pending data.
  68. =head1 NOTES
  69. BIO_flush(), because it can write data may return 0 or -1 indicating
  70. that the call should be retried later in a similar manner to BIO_write_ex().
  71. The BIO_should_retry() call should be used and appropriate action taken
  72. is the call fails.
  73. The return values of BIO_pending() and BIO_wpending() may not reliably
  74. determine the amount of pending data in all cases. For example in the
  75. case of a file BIO some data may be available in the FILE structures
  76. internal buffers but it is not possible to determine this in a
  77. portably way. For other types of BIO they may not be supported.
  78. Filter BIOs if they do not internally handle a particular BIO_ctrl()
  79. operation usually pass the operation to the next BIO in the chain.
  80. This often means there is no need to locate the required BIO for
  81. a particular operation, it can be called on a chain and it will
  82. be automatically passed to the relevant BIO. However this can cause
  83. unexpected results: for example no current filter BIOs implement
  84. BIO_seek(), but this may still succeed if the chain ends in a FILE
  85. or file descriptor BIO.
  86. Source/sink BIOs return an 0 if they do not recognize the BIO_ctrl()
  87. operation.
  88. =head1 BUGS
  89. Some of the return values are ambiguous and care should be taken. In
  90. particular a return value of 0 can be returned if an operation is not
  91. supported, if an error occurred, if EOF has not been reached and in
  92. the case of BIO_seek() on a file BIO for a successful operation.
  93. =head1 COPYRIGHT
  94. Copyright 2000-2016 The OpenSSL Project Authors. All Rights Reserved.
  95. Licensed under the OpenSSL license (the "License"). You may not use
  96. this file except in compliance with the License. You can obtain a copy
  97. in the file LICENSE in the source distribution or at
  98. L<https://www.openssl.org/source/license.html>.
  99. =cut