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BIO_ctrl.pod 4.8 KB

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  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 control operations
  7. =head1 SYNOPSIS
  8. #include <openssl/bio.h>
  9. long BIO_ctrl(BIO *bp,int cmd,long larg,void *parg);
  10. long BIO_callback_ctrl(BIO *b, int cmd, void (*fp)(struct bio_st *, int, const char *, int, long, long));
  11. char * BIO_ptr_ctrl(BIO *bp,int cmd,long larg);
  12. long BIO_int_ctrl(BIO *bp,int cmd,long larg,int iarg);
  13. int BIO_reset(BIO *b);
  14. int BIO_seek(BIO *b, int ofs);
  15. int BIO_tell(BIO *b);
  16. int BIO_flush(BIO *b);
  17. int BIO_eof(BIO *b);
  18. int BIO_set_close(BIO *b,long flag);
  19. int BIO_get_close(BIO *b);
  20. int BIO_pending(BIO *b);
  21. int BIO_wpending(BIO *b);
  22. size_t BIO_ctrl_pending(BIO *b);
  23. size_t BIO_ctrl_wpending(BIO *b);
  24. int BIO_get_info_callback(BIO *b,bio_info_cb **cbp);
  25. int BIO_set_info_callback(BIO *b,bio_info_cb *cb);
  26. typedef void bio_info_cb(BIO *b, int oper, const char *ptr, int arg1, long arg2, long arg3);
  27. =head1 DESCRIPTION
  28. BIO_ctrl(), BIO_callback_ctrl(), BIO_ptr_ctrl() and BIO_int_ctrl()
  29. are BIO "control" operations taking arguments of various types.
  30. These functions are not normally called directly, various macros
  31. are used instead. The standard macros are described below, macros
  32. specific to a particular type of BIO are described in the specific
  33. BIOs manual page as well as any special features of the standard
  34. calls.
  35. BIO_reset() typically resets a BIO to some initial state, in the case
  36. of file related BIOs for example it rewinds the file pointer to the
  37. start of the file.
  38. BIO_seek() resets a file related BIO's (that is file descriptor and
  39. FILE BIOs) file position pointer to B<ofs> bytes from start of file.
  40. BIO_tell() returns the current file position of a file related BIO.
  41. BIO_flush() normally writes out any internally buffered data, in some
  42. cases it is used to signal EOF and that no more data will be written.
  43. BIO_eof() returns 1 if the BIO has read EOF, the precise meaning of
  44. "EOF" varies according to the BIO type.
  45. BIO_set_close() sets the BIO B<b> close flag to B<flag>. B<flag> can
  46. take the value BIO_CLOSE or BIO_NOCLOSE. Typically BIO_CLOSE is used
  47. in a source/sink BIO to indicate that the underlying I/O stream should
  48. be closed when the BIO is freed.
  49. BIO_get_close() returns the BIOs close flag.
  50. BIO_pending(), BIO_ctrl_pending(), BIO_wpending() and BIO_ctrl_wpending()
  51. return the number of pending characters in the BIOs read and write buffers.
  52. Not all BIOs support these calls. BIO_ctrl_pending() and BIO_ctrl_wpending()
  53. return a size_t type and are functions, BIO_pending() and BIO_wpending() are
  54. macros which call BIO_ctrl().
  55. =head1 RETURN VALUES
  56. BIO_reset() normally returns 1 for success and 0 or -1 for failure. File
  57. BIOs are an exception, they return 0 for success and -1 for failure.
  58. BIO_seek() and BIO_tell() both return the current file position on success
  59. and -1 for failure, except file BIOs which for BIO_seek() always return 0
  60. for success and -1 for failure.
  61. BIO_flush() returns 1 for success and 0 or -1 for failure.
  62. BIO_eof() returns 1 if EOF has been reached 0 otherwise.
  63. BIO_set_close() always returns 1.
  64. BIO_get_close() returns the close flag value: BIO_CLOSE or BIO_NOCLOSE.
  65. BIO_pending(), BIO_ctrl_pending(), BIO_wpending() and BIO_ctrl_wpending()
  66. return the amount of pending data.
  67. =head1 NOTES
  68. BIO_flush(), because it can write data may return 0 or -1 indicating
  69. that the call should be retried later in a similar manner to BIO_write().
  70. The BIO_should_retry() call should be used and appropriate action taken
  71. is the call fails.
  72. The return values of BIO_pending() and BIO_wpending() may not reliably
  73. determine the amount of pending data in all cases. For example in the
  74. case of a file BIO some data may be available in the FILE structures
  75. internal buffers but it is not possible to determine this in a
  76. portably way. For other types of BIO they may not be supported.
  77. Filter BIOs if they do not internally handle a particular BIO_ctrl()
  78. operation usually pass the operation to the next BIO in the chain.
  79. This often means there is no need to locate the required BIO for
  80. a particular operation, it can be called on a chain and it will
  81. be automatically passed to the relevant BIO. However this can cause
  82. unexpected results: for example no current filter BIOs implement
  83. BIO_seek(), but this may still succeed if the chain ends in a FILE
  84. or file descriptor BIO.
  85. Source/sink BIOs return an 0 if they do not recognize the BIO_ctrl()
  86. operation.
  87. =head1 BUGS
  88. Some of the return values are ambiguous and care should be taken. In
  89. particular a return value of 0 can be returned if an operation is not
  90. supported, if an error occurred, if EOF has not been reached and in
  91. the case of BIO_seek() on a file BIO for a successful operation.
  92. =head1 SEE ALSO
  93. TBA