text: /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
   * All rights reserved.
   *
   * This package is an SSL implementation written
   * by Eric Young (eay@cryptsoft.com).
   * The implementation was written so as to conform with Netscapes SSL.
   *
   * This library is free for commercial and non-commercial use as long as
   * the following conditions are aheared to.  The following conditions
   * apply to all code found in this distribution, be it the RC4, RSA,
   * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
   * included with this distribution is covered by the same copyright terms
   * except that the holder is Tim Hudson (tjh@cryptsoft.com).
   *
   * Copyright remains Eric Young's, and as such any Copyright notices in
   * the code are not to be removed.
   * If this package is used in a product, Eric Young should be given attribution
   * as the author of the parts of the library used.
   * This can be in the form of a textual message at program startup or
   * in documentation (online or textual) provided with the package.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   * 1. Redistributions of source code must retain the copyright
   *    notice, this list of conditions and the following disclaimer.
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in the
   *    documentation and/or other materials provided with the distribution.
   * 3. All advertising materials mentioning features or use of this software
   *    must display the following acknowledgement:
   *    "This product includes cryptographic software written by
   *     Eric Young (eay@cryptsoft.com)"
   *    The word 'cryptographic' can be left out if the rouines from the library
   *    being used are not cryptographic related :-).
   * 4. If you include any Windows specific code (or a derivative thereof) from
   *    the apps directory (application code) you must include an acknowledgement:
   *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
   *
   * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
   * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
   * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   * SUCH DAMAGE.
   *
   * The licence and distribution terms for any publically available version or
   * derivative of this code cannot be changed.  i.e. this code cannot simply be
   * copied and put under another distribution licence
   * [including the GNU Public Licence.] */
  
  #ifndef OPENSSL_HEADER_BIO_H
  #define OPENSSL_HEADER_BIO_H
  
  #include "CJWTKitBoringSSL_base.h"
  
  #include <stdio.h>  // For FILE
  
  #include "CJWTKitBoringSSL_buffer.h"
  #include "CJWTKitBoringSSL_err.h"  // for ERR_print_errors_fp
  #include "CJWTKitBoringSSL_ex_data.h"
  #include "CJWTKitBoringSSL_stack.h"
  #include "CJWTKitBoringSSL_thread.h"
  
  #if defined(__cplusplus)
  extern "C" {
  #endif
  
  
  // BIO abstracts over a file-descriptor like interface.
  
  
  // Allocation and freeing.
  
  DEFINE_STACK_OF(BIO)
  
  // BIO_new creates a new BIO with the given method and a reference count of one.
  // It returns the fresh |BIO|, or NULL on error.
  OPENSSL_EXPORT BIO *BIO_new(const BIO_METHOD *method);
  
  // BIO_free decrements the reference count of |bio|. If the reference count
  // drops to zero, it calls the destroy callback, if present, on the method and
  // frees |bio| itself. It then repeats that for the next BIO in the chain, if
  // any.
  //
  // It returns one on success or zero otherwise.
  OPENSSL_EXPORT int BIO_free(BIO *bio);
  
  // BIO_vfree performs the same actions as |BIO_free|, but has a void return
  // value. This is provided for API-compat.
  //
  // TODO(fork): remove.
  OPENSSL_EXPORT void BIO_vfree(BIO *bio);
  
  // BIO_up_ref increments the reference count of |bio| and returns one.
  OPENSSL_EXPORT int BIO_up_ref(BIO *bio);
  
  
  // Basic I/O.
  
  // BIO_read attempts to read |len| bytes into |data|. It returns the number of
  // bytes read, zero on EOF, or a negative number on error.
  OPENSSL_EXPORT int BIO_read(BIO *bio, void *data, int len);
  
  // BIO_gets "reads a line" from |bio| and puts at most |size| bytes into |buf|.
  // It returns the number of bytes read or a negative number on error. The
  // phrase "reads a line" is in quotes in the previous sentence because the
  // exact operation depends on the BIO's method. For example, a digest BIO will
  // return the digest in response to a |BIO_gets| call.
  //
  // TODO(fork): audit the set of BIOs that we end up needing. If all actually
  // return a line for this call, remove the warning above.
  OPENSSL_EXPORT int BIO_gets(BIO *bio, char *buf, int size);
  
  // BIO_write writes |len| bytes from |data| to |bio|. It returns the number of
  // bytes written or a negative number on error.
  OPENSSL_EXPORT int BIO_write(BIO *bio, const void *data, int len);
  
  // BIO_write_all writes |len| bytes from |data| to |bio|, looping as necessary.
  // It returns one if all bytes were successfully written and zero on error.
  OPENSSL_EXPORT int BIO_write_all(BIO *bio, const void *data, size_t len);
  
  // BIO_puts writes a NUL terminated string from |buf| to |bio|. It returns the
  // number of bytes written or a negative number on error.
  OPENSSL_EXPORT int BIO_puts(BIO *bio, const char *buf);
  
  // BIO_flush flushes any buffered output. It returns one on success and zero
  // otherwise.
  OPENSSL_EXPORT int BIO_flush(BIO *bio);
  
  
  // Low-level control functions.
  //
  // These are generic functions for sending control requests to a BIO. In
  // general one should use the wrapper functions like |BIO_get_close|.
  
  // BIO_ctrl sends the control request |cmd| to |bio|. The |cmd| argument should
  // be one of the |BIO_C_*| values.
  OPENSSL_EXPORT long BIO_ctrl(BIO *bio, int cmd, long larg, void *parg);
  
  // BIO_ptr_ctrl acts like |BIO_ctrl| but passes the address of a |void*|
  // pointer as |parg| and returns the value that is written to it, or NULL if
  // the control request returns <= 0.
  OPENSSL_EXPORT char *BIO_ptr_ctrl(BIO *bp, int cmd, long larg);
  
  // BIO_int_ctrl acts like |BIO_ctrl| but passes the address of a copy of |iarg|
  // as |parg|.
  OPENSSL_EXPORT long BIO_int_ctrl(BIO *bp, int cmd, long larg, int iarg);
  
  // BIO_reset resets |bio| to its initial state, the precise meaning of which
  // depends on the concrete type of |bio|. It returns one on success and zero
  // otherwise.
  OPENSSL_EXPORT int BIO_reset(BIO *bio);
  
  // BIO_eof returns non-zero when |bio| has reached end-of-file. The precise
  // meaning of which depends on the concrete type of |bio|. Note that in the
  // case of BIO_pair this always returns non-zero.
  OPENSSL_EXPORT int BIO_eof(BIO *bio);
  
  // BIO_set_flags ORs |flags| with |bio->flags|.
  OPENSSL_EXPORT void BIO_set_flags(BIO *bio, int flags);
  
  // BIO_test_flags returns |bio->flags| AND |flags|.
  OPENSSL_EXPORT int BIO_test_flags(const BIO *bio, int flags);
  
  // BIO_should_read returns non-zero if |bio| encountered a temporary error
  // while reading (i.e. EAGAIN), indicating that the caller should retry the
  // read.
  OPENSSL_EXPORT int BIO_should_read(const BIO *bio);
  
  // BIO_should_write returns non-zero if |bio| encountered a temporary error
  // while writing (i.e. EAGAIN), indicating that the caller should retry the
  // write.
  OPENSSL_EXPORT int BIO_should_write(const BIO *bio);
  
  // BIO_should_retry returns non-zero if the reason that caused a failed I/O
  // operation is temporary and thus the operation should be retried. Otherwise,
  // it was a permanent error and it returns zero.
  OPENSSL_EXPORT int BIO_should_retry(const BIO *bio);
  
  // BIO_should_io_special returns non-zero if |bio| encountered a temporary
  // error while performing a special I/O operation, indicating that the caller
  // should retry. The operation that caused the error is returned by
  // |BIO_get_retry_reason|.
  OPENSSL_EXPORT int BIO_should_io_special(const BIO *bio);
  
  // BIO_RR_CONNECT indicates that a connect would have blocked
  #define BIO_RR_CONNECT 0x02
  
  // BIO_RR_ACCEPT indicates that an accept would have blocked
  #define BIO_RR_ACCEPT 0x03
  
  // BIO_get_retry_reason returns the special I/O operation that needs to be
  // retried. The return value is one of the |BIO_RR_*| values.
  OPENSSL_EXPORT int BIO_get_retry_reason(const BIO *bio);
  
  // BIO_set_retry_reason sets the special I/O operation that needs to be retried
  // to |reason|, which should be one of the |BIO_RR_*| values.
  OPENSSL_EXPORT void BIO_set_retry_reason(BIO *bio, int reason);
  
  // BIO_clear_flags ANDs |bio->flags| with the bitwise-complement of |flags|.
  OPENSSL_EXPORT void BIO_clear_flags(BIO *bio, int flags);
  
  // BIO_set_retry_read sets the |BIO_FLAGS_READ| and |BIO_FLAGS_SHOULD_RETRY|
  // flags on |bio|.
  OPENSSL_EXPORT void BIO_set_retry_read(BIO *bio);
  
  // BIO_set_retry_write sets the |BIO_FLAGS_WRITE| and |BIO_FLAGS_SHOULD_RETRY|
  // flags on |bio|.
  OPENSSL_EXPORT void BIO_set_retry_write(BIO *bio);
  
  // BIO_get_retry_flags gets the |BIO_FLAGS_READ|, |BIO_FLAGS_WRITE|,
  // |BIO_FLAGS_IO_SPECIAL| and |BIO_FLAGS_SHOULD_RETRY| flags from |bio|.
  OPENSSL_EXPORT int BIO_get_retry_flags(BIO *bio);
  
  // BIO_clear_retry_flags clears the |BIO_FLAGS_READ|, |BIO_FLAGS_WRITE|,
  // |BIO_FLAGS_IO_SPECIAL| and |BIO_FLAGS_SHOULD_RETRY| flags from |bio|.
  OPENSSL_EXPORT void BIO_clear_retry_flags(BIO *bio);
  
  // BIO_method_type returns the type of |bio|, which is one of the |BIO_TYPE_*|
  // values.
  OPENSSL_EXPORT int BIO_method_type(const BIO *bio);
  
  // These are passed to the BIO callback
  #define BIO_CB_FREE 0x01
  #define BIO_CB_READ 0x02
  #define BIO_CB_WRITE 0x03
  #define BIO_CB_PUTS 0x04
  #define BIO_CB_GETS 0x05
  #define BIO_CB_CTRL 0x06
  
  // The callback is called before and after the underling operation,
  // The BIO_CB_RETURN flag indicates if it is after the call
  #define BIO_CB_RETURN 0x80
  
  // bio_info_cb is the type of a callback function that can be called for most
  // BIO operations. The |event| argument is one of |BIO_CB_*| and can be ORed
  // with |BIO_CB_RETURN| if the callback is being made after the operation in
  // question. In that case, |return_value| will contain the return value from
  // the operation.
  typedef long (*bio_info_cb)(BIO *bio, int event, const char *parg, int cmd,
                              long larg, long return_value);
  
  // BIO_callback_ctrl allows the callback function to be manipulated. The |cmd|
  // arg will generally be |BIO_CTRL_SET_CALLBACK| but arbitrary command values
  // can be interpreted by the |BIO|.
  OPENSSL_EXPORT long BIO_callback_ctrl(BIO *bio, int cmd, bio_info_cb fp);
  
  // BIO_pending returns the number of bytes pending to be read.
  OPENSSL_EXPORT size_t BIO_pending(const BIO *bio);
  
  // BIO_ctrl_pending calls |BIO_pending| and exists only for compatibility with
  // OpenSSL.
  OPENSSL_EXPORT size_t BIO_ctrl_pending(const BIO *bio);
  
  // BIO_wpending returns the number of bytes pending to be written.
  OPENSSL_EXPORT size_t BIO_wpending(const BIO *bio);
  
  // BIO_set_close sets the close flag for |bio|. The meaning of which depends on
  // the type of |bio| but, for example, a memory BIO interprets the close flag
  // as meaning that it owns its buffer. It returns one on success and zero
  // otherwise.
  OPENSSL_EXPORT int BIO_set_close(BIO *bio, int close_flag);
  
  // BIO_number_read returns the number of bytes that have been read from
  // |bio|.
  OPENSSL_EXPORT size_t BIO_number_read(const BIO *bio);
  
  // BIO_number_written returns the number of bytes that have been written to
  // |bio|.
  OPENSSL_EXPORT size_t BIO_number_written(const BIO *bio);
  
  
  // Managing chains of BIOs.
  //
  // BIOs can be put into chains where the output of one is used as the input of
  // the next etc. The most common case is a buffering BIO, which accepts and
  // buffers writes until flushed into the next BIO in the chain.
  
  // BIO_push adds |appended_bio| to the end of the chain with |bio| at the head.
  // It returns |bio|. Note that |appended_bio| may be the head of a chain itself
  // and thus this function can be used to join two chains.
  //
  // BIO_push takes ownership of the caller's reference to |appended_bio|.
  OPENSSL_EXPORT BIO *BIO_push(BIO *bio, BIO *appended_bio);
  
  // BIO_pop removes |bio| from the head of a chain and returns the next BIO in
  // the chain, or NULL if there is no next BIO.
  //
  // The caller takes ownership of the chain's reference to |bio|.
  OPENSSL_EXPORT BIO *BIO_pop(BIO *bio);
  
  // BIO_next returns the next BIO in the chain after |bio|, or NULL if there is
  // no such BIO.
  OPENSSL_EXPORT BIO *BIO_next(BIO *bio);
  
  // BIO_free_all calls |BIO_free|.
  //
  // TODO(fork): update callers and remove.
  OPENSSL_EXPORT void BIO_free_all(BIO *bio);
  
  // BIO_find_type walks a chain of BIOs and returns the first that matches
  // |type|, which is one of the |BIO_TYPE_*| values.
  OPENSSL_EXPORT BIO *BIO_find_type(BIO *bio, int type);
  
  // BIO_copy_next_retry sets the retry flags and |retry_reason| of |bio| from
  // the next BIO in the chain.
  OPENSSL_EXPORT void BIO_copy_next_retry(BIO *bio);
  
  
  // Printf functions.
  
  // BIO_printf behaves like |printf| but outputs to |bio| rather than a |FILE|.
  // It returns the number of bytes written or a negative number on error.
  OPENSSL_EXPORT int BIO_printf(BIO *bio, const char *format, ...)
      OPENSSL_PRINTF_FORMAT_FUNC(2, 3);
  
  
  // Utility functions.
  
  // BIO_indent prints min(|indent|, |max_indent|) spaces. It returns one on
  // success and zero otherwise.
  OPENSSL_EXPORT int BIO_indent(BIO *bio, unsigned indent, unsigned max_indent);
  
  // BIO_hexdump writes a hex dump of |data| to |bio|. Each line will be indented
  // by |indent| spaces.
  OPENSSL_EXPORT int BIO_hexdump(BIO *bio, const uint8_t *data, size_t len,
                                 unsigned indent);
  
  // ERR_print_errors prints the current contents of the error stack to |bio|
  // using human readable strings where possible.
  OPENSSL_EXPORT void ERR_print_errors(BIO *bio);
  
  // BIO_read_asn1 reads a single ASN.1 object from |bio|. If successful it sets
  // |*out| to be an allocated buffer (that should be freed with |OPENSSL_free|),
  // |*out_size| to the length, in bytes, of that buffer and returns one.
  // Otherwise it returns zero.
  //
  // If the length of the object is greater than |max_len| or 2^32 then the
  // function will fail. Long-form tags are not supported. If the length of the
  // object is indefinite the full contents of |bio| are read, unless it would be
  // greater than |max_len|, in which case the function fails.
  //
  // If the function fails then some unknown amount of data may have been read
  // from |bio|.
  OPENSSL_EXPORT int BIO_read_asn1(BIO *bio, uint8_t **out, size_t *out_len,
                                   size_t max_len);
  
  
  // Memory BIOs.
  //
  // Memory BIOs can be used as a read-only source (with |BIO_new_mem_buf|) or a
  // writable sink (with |BIO_new|, |BIO_s_mem| and |BIO_mem_contents|). Data
  // written to a writable, memory BIO can be recalled by reading from it.
  //
  // Calling |BIO_reset| on a read-only BIO resets it to the original contents.
  // On a writable BIO, it clears any data.
  //
  // If the close flag is set to |BIO_NOCLOSE| (not the default) then the
  // underlying |BUF_MEM| will not be freed when the |BIO| is freed.
  //
  // Memory BIOs support |BIO_gets| and |BIO_puts|.
  //
  // |BIO_ctrl_pending| returns the number of bytes currently stored.
  
  // BIO_NOCLOSE and |BIO_CLOSE| can be used as symbolic arguments when a "close
  // flag" is passed to a BIO function.
  #define BIO_NOCLOSE 0
  #define BIO_CLOSE 1
  
  // BIO_s_mem returns a |BIO_METHOD| that uses a in-memory buffer.
  OPENSSL_EXPORT const BIO_METHOD *BIO_s_mem(void);
  
  // BIO_new_mem_buf creates read-only BIO that reads from |len| bytes at |buf|.
  // It returns the BIO or NULL on error. This function does not copy or take
  // ownership of |buf|. The caller must ensure the memory pointed to by |buf|
  // outlives the |BIO|.
  //
  // If |len| is negative, then |buf| is treated as a NUL-terminated string, but
  // don't depend on this in new code.
  OPENSSL_EXPORT BIO *BIO_new_mem_buf(const void *buf, int len);
  
  // BIO_mem_contents sets |*out_contents| to point to the current contents of
  // |bio| and |*out_len| to contain the length of that data. It returns one on
  // success and zero otherwise.
  OPENSSL_EXPORT int BIO_mem_contents(const BIO *bio,
                                      const uint8_t **out_contents,
                                      size_t *out_len);
  
  // BIO_get_mem_data sets |*contents| to point to the current contents of |bio|
  // and returns the length of the data.
  //
  // WARNING: don't use this, use |BIO_mem_contents|. A return value of zero from
  // this function can mean either that it failed or that the memory buffer is
  // empty.
  OPENSSL_EXPORT long BIO_get_mem_data(BIO *bio, char **contents);
  
  // BIO_get_mem_ptr sets |*out| to a BUF_MEM containing the current contents of
  // |bio|. It returns one on success or zero on error.
  OPENSSL_EXPORT int BIO_get_mem_ptr(BIO *bio, BUF_MEM **out);
  
  // BIO_set_mem_buf sets |b| as the contents of |bio|. If |take_ownership| is
  // non-zero, then |b| will be freed when |bio| is closed. Returns one on
  // success or zero otherwise.
  OPENSSL_EXPORT int BIO_set_mem_buf(BIO *bio, BUF_MEM *b, int take_ownership);
  
  // BIO_set_mem_eof_return sets the value that will be returned from reading
  // |bio| when empty. If |eof_value| is zero then an empty memory BIO will
  // return EOF (that is it will return zero and |BIO_should_retry| will be
  // false). If |eof_value| is non zero then it will return |eof_value| when it
  // is empty and it will set the read retry flag (that is |BIO_read_retry| is
  // true). To avoid ambiguity with a normal positive return value, |eof_value|
  // should be set to a negative value, typically -1.
  //
  // For a read-only BIO, the default is zero (EOF). For a writable BIO, the
  // default is -1 so that additional data can be written once exhausted.
  OPENSSL_EXPORT int BIO_set_mem_eof_return(BIO *bio, int eof_value);
  
  
  // File descriptor BIOs.
  //
  // File descriptor BIOs are wrappers around the system's |read| and |write|
  // functions. If the close flag is set then then |close| is called on the
  // underlying file descriptor when the BIO is freed.
  //
  // |BIO_reset| attempts to seek the file pointer to the start of file using
  // |lseek|.
  
  // BIO_s_fd returns a |BIO_METHOD| for file descriptor fds.
  OPENSSL_EXPORT const BIO_METHOD *BIO_s_fd(void);
  
  // BIO_new_fd creates a new file descriptor BIO wrapping |fd|. If |close_flag|
  // is non-zero, then |fd| will be closed when the BIO is.
  OPENSSL_EXPORT BIO *BIO_new_fd(int fd, int close_flag);
  
  // BIO_set_fd sets the file descriptor of |bio| to |fd|. If |close_flag| is
  // non-zero then |fd| will be closed when |bio| is. It returns one on success
  // or zero on error.
  //
  // This function may also be used with socket BIOs (see |BIO_s_socket| and
  // |BIO_new_socket|).
  OPENSSL_EXPORT int BIO_set_fd(BIO *bio, int fd, int close_flag);
  
  // BIO_get_fd returns the file descriptor currently in use by |bio| or -1 if
  // |bio| does not wrap a file descriptor. If there is a file descriptor and
  // |out_fd| is not NULL, it also sets |*out_fd| to the file descriptor.
  //
  // This function may also be used with socket BIOs (see |BIO_s_socket| and
  // |BIO_new_socket|).
  OPENSSL_EXPORT int BIO_get_fd(BIO *bio, int *out_fd);
  
  
  // File BIOs.
  //
  // File BIOs are wrappers around a C |FILE| object.
  //
  // |BIO_flush| on a file BIO calls |fflush| on the wrapped stream.
  //
  // |BIO_reset| attempts to seek the file pointer to the start of file using
  // |fseek|.
  //
  // Setting the close flag causes |fclose| to be called on the stream when the
  // BIO is freed.
  
  // BIO_s_file returns a BIO_METHOD that wraps a |FILE|.
  OPENSSL_EXPORT const BIO_METHOD *BIO_s_file(void);
  
  // BIO_new_file creates a file BIO by opening |filename| with the given mode.
  // See the |fopen| manual page for details of the mode argument.
  OPENSSL_EXPORT BIO *BIO_new_file(const char *filename, const char *mode);
  
  // BIO_new_fp creates a new file BIO that wraps the given |FILE|. If
  // |close_flag| is |BIO_CLOSE|, then |fclose| will be called on |stream| when
  // the BIO is closed.
  OPENSSL_EXPORT BIO *BIO_new_fp(FILE *stream, int close_flag);
  
  // BIO_get_fp sets |*out_file| to the current |FILE| for |bio|. It returns one
  // on success and zero otherwise.
  OPENSSL_EXPORT int BIO_get_fp(BIO *bio, FILE **out_file);
  
  // BIO_set_fp sets the |FILE| for |bio|. If |close_flag| is |BIO_CLOSE| then
  // |fclose| will be called on |file| when |bio| is closed. It returns one on
  // success and zero otherwise.
  OPENSSL_EXPORT int BIO_set_fp(BIO *bio, FILE *file, int close_flag);
  
  // BIO_read_filename opens |filename| for reading and sets the result as the
  // |FILE| for |bio|. It returns one on success and zero otherwise. The |FILE|
  // will be closed when |bio| is freed.
  OPENSSL_EXPORT int BIO_read_filename(BIO *bio, const char *filename);
  
  // BIO_write_filename opens |filename| for writing and sets the result as the
  // |FILE| for |bio|. It returns one on success and zero otherwise. The |FILE|
  // will be closed when |bio| is freed.
  OPENSSL_EXPORT int BIO_write_filename(BIO *bio, const char *filename);
  
  // BIO_append_filename opens |filename| for appending and sets the result as
  // the |FILE| for |bio|. It returns one on success and zero otherwise. The
  // |FILE| will be closed when |bio| is freed.
  OPENSSL_EXPORT int BIO_append_filename(BIO *bio, const char *filename);
  
  // BIO_rw_filename opens |filename| for reading and writing and sets the result
  // as the |FILE| for |bio|. It returns one on success and zero otherwise. The
  // |FILE| will be closed when |bio| is freed.
  OPENSSL_EXPORT int BIO_rw_filename(BIO *bio, const char *filename);
  
  
  // Socket BIOs.
  //
  // Socket BIOs behave like file descriptor BIOs but, on Windows systems, wrap
  // the system's |recv| and |send| functions instead of |read| and |write|. On
  // Windows, file descriptors are provided by C runtime and are not
  // interchangeable with sockets.
  //
  // Socket BIOs may be used with |BIO_set_fd| and |BIO_get_fd|.
  //
  // TODO(davidben): Add separate APIs and fix the internals to use |SOCKET|s
  // around rather than rely on int casts.
  
  OPENSSL_EXPORT const BIO_METHOD *BIO_s_socket(void);
  
  // BIO_new_socket allocates and initialises a fresh BIO which will read and
  // write to the socket |fd|. If |close_flag| is |BIO_CLOSE| then closing the
  // BIO will close |fd|. It returns the fresh |BIO| or NULL on error.
  OPENSSL_EXPORT BIO *BIO_new_socket(int fd, int close_flag);
  
  
  // Connect BIOs.
  //
  // A connection BIO creates a network connection and transfers data over the
  // resulting socket.
  
  OPENSSL_EXPORT const BIO_METHOD *BIO_s_connect(void);
  
  // BIO_new_connect returns a BIO that connects to the given hostname and port.
  // The |host_and_optional_port| argument should be of the form
  // "www.example.com" or "www.example.com:443". If the port is omitted, it must
  // be provided with |BIO_set_conn_port|.
  //
  // It returns the new BIO on success, or NULL on error.
  OPENSSL_EXPORT BIO *BIO_new_connect(const char *host_and_optional_port);
  
  // BIO_set_conn_hostname sets |host_and_optional_port| as the hostname and
  // optional port that |bio| will connect to. If the port is omitted, it must be
  // provided with |BIO_set_conn_port|.
  //
  // It returns one on success and zero otherwise.
  OPENSSL_EXPORT int BIO_set_conn_hostname(BIO *bio,
                                           const char *host_and_optional_port);
  
  // BIO_set_conn_port sets |port_str| as the port or service name that |bio|
  // will connect to. It returns one on success and zero otherwise.
  OPENSSL_EXPORT int BIO_set_conn_port(BIO *bio, const char *port_str);
  
  // BIO_set_conn_int_port sets |*port| as the port that |bio| will connect to.
  // It returns one on success and zero otherwise.
  OPENSSL_EXPORT int BIO_set_conn_int_port(BIO *bio, const int *port);
  
  // BIO_set_nbio sets whether |bio| will use non-blocking I/O operations. It
  // returns one on success and zero otherwise.
  OPENSSL_EXPORT int BIO_set_nbio(BIO *bio, int on);
  
  // BIO_do_connect connects |bio| if it has not been connected yet. It returns
  // one on success and <= 0 otherwise.
  OPENSSL_EXPORT int BIO_do_connect(BIO *bio);
  
  
  // Datagram BIOs.
  //
  // TODO(fork): not implemented.
  
  #define BIO_CTRL_DGRAM_QUERY_MTU 40  // as kernel for current MTU
  
  #define BIO_CTRL_DGRAM_SET_MTU 42 /* set cached value for  MTU. want to use
                                       this if asking the kernel fails */
  
  #define BIO_CTRL_DGRAM_MTU_EXCEEDED 43 /* check whether the MTU was exceed in
                                            the previous write operation. */
  
  // BIO_CTRL_DGRAM_SET_NEXT_TIMEOUT is unsupported as it is unused by consumers
  // and depends on |timeval|, which is not 2038-clean on all platforms.
  
  #define BIO_CTRL_DGRAM_GET_PEER           46
  
  #define BIO_CTRL_DGRAM_GET_FALLBACK_MTU   47
  
  
  // BIO Pairs.
  //
  // BIO pairs provide a "loopback" like system: a pair of BIOs where data
  // written to one can be read from the other and vice versa.
  
  // BIO_new_bio_pair sets |*out1| and |*out2| to two freshly created BIOs where
  // data written to one can be read from the other and vice versa. The
  // |writebuf1| argument gives the size of the buffer used in |*out1| and
  // |writebuf2| for |*out2|. It returns one on success and zero on error.
  OPENSSL_EXPORT int BIO_new_bio_pair(BIO **out1, size_t writebuf1, BIO **out2,
                                      size_t writebuf2);
  
  // BIO_ctrl_get_read_request returns the number of bytes that the other side of
  // |bio| tried (unsuccessfully) to read.
  OPENSSL_EXPORT size_t BIO_ctrl_get_read_request(BIO *bio);
  
  // BIO_ctrl_get_write_guarantee returns the number of bytes that |bio| (which
  // must have been returned by |BIO_new_bio_pair|) will accept on the next
  // |BIO_write| call.
  OPENSSL_EXPORT size_t BIO_ctrl_get_write_guarantee(BIO *bio);
  
  // BIO_shutdown_wr marks |bio| as closed, from the point of view of the other
  // side of the pair. Future |BIO_write| calls on |bio| will fail. It returns
  // one on success and zero otherwise.
  OPENSSL_EXPORT int BIO_shutdown_wr(BIO *bio);
  
  
  // Custom BIOs.
  //
  // Consumers can create custom |BIO|s by filling in a |BIO_METHOD| and using
  // low-level control functions to set state.
  
  // BIO_get_new_index returns a new "type" value for a custom |BIO|.
  OPENSSL_EXPORT int BIO_get_new_index(void);
  
  // BIO_meth_new returns a newly-allocated |BIO_METHOD| or NULL on allocation
  // error. The |type| specifies the type that will be returned by
  // |BIO_method_type|. If this is unnecessary, this value may be zero. The |name|
  // parameter is vestigial and may be NULL.
  //
  // Use the |BIO_meth_set_*| functions below to initialize the |BIO_METHOD|. The
  // function implementations may use |BIO_set_data| and |BIO_get_data| to add
  // method-specific state to associated |BIO|s. Additionally, |BIO_set_init| must
  // be called after an associated |BIO| is fully initialized. State set via
  // |BIO_set_data| may be released by configuring a destructor with
  // |BIO_meth_set_destroy|.
  OPENSSL_EXPORT BIO_METHOD *BIO_meth_new(int type, const char *name);
  
  // BIO_meth_free releases memory associated with |method|.
  OPENSSL_EXPORT void BIO_meth_free(BIO_METHOD *method);
  
  // BIO_meth_set_create sets a function to be called on |BIO_new| for |method|
  // and returns one. The function should return one on success and zero on
  // error.
  OPENSSL_EXPORT int BIO_meth_set_create(BIO_METHOD *method,
                                         int (*create)(BIO *));
  
  // BIO_meth_set_destroy sets a function to release data associated with a |BIO|
  // and returns one. The function's return value is ignored.
  OPENSSL_EXPORT int BIO_meth_set_destroy(BIO_METHOD *method,
                                          int (*destroy)(BIO *));
  
  // BIO_meth_set_write sets the implementation of |BIO_write| for |method| and
  // returns one. |BIO_METHOD|s which implement |BIO_write| should also implement
  // |BIO_CTRL_FLUSH|. (See |BIO_meth_set_ctrl|.)
  OPENSSL_EXPORT int BIO_meth_set_write(BIO_METHOD *method,
                                        int (*write)(BIO *, const char *, int));
  
  // BIO_meth_set_read sets the implementation of |BIO_read| for |method| and
  // returns one.
  OPENSSL_EXPORT int BIO_meth_set_read(BIO_METHOD *method,
                                       int (*read)(BIO *, char *, int));
  
  // BIO_meth_set_gets sets the implementation of |BIO_gets| for |method| and
  // returns one.
  OPENSSL_EXPORT int BIO_meth_set_gets(BIO_METHOD *method,
                                       int (*gets)(BIO *, char *, int));
  
  // BIO_meth_set_ctrl sets the implementation of |BIO_ctrl| for |method| and
  // returns one.
  OPENSSL_EXPORT int BIO_meth_set_ctrl(BIO_METHOD *method,
                                       long (*ctrl)(BIO *, int, long, void *));
  
  // BIO_set_data sets custom data on |bio|. It may be retried with
  // |BIO_get_data|.
  OPENSSL_EXPORT void BIO_set_data(BIO *bio, void *ptr);
  
  // BIO_get_data returns custom data on |bio| set by |BIO_get_data|.
  OPENSSL_EXPORT void *BIO_get_data(BIO *bio);
  
  // BIO_set_init sets whether |bio| has been fully initialized. Until fully
  // initialized, |BIO_read| and |BIO_write| will fail.
  OPENSSL_EXPORT void BIO_set_init(BIO *bio, int init);
  
  // BIO_get_init returns whether |bio| has been fully initialized.
  OPENSSL_EXPORT int BIO_get_init(BIO *bio);
  
  // These are values of the |cmd| argument to |BIO_ctrl|.
  
  // BIO_CTRL_RESET implements |BIO_reset|. The arguments are unused.
  #define BIO_CTRL_RESET 1
  
  // BIO_CTRL_EOF implements |BIO_eof|. The arguments are unused.
  #define BIO_CTRL_EOF 2
  
  // BIO_CTRL_INFO is a legacy command that returns information specific to the
  // type of |BIO|. It is not safe to call generically and should not be
  // implemented in new |BIO| types.
  #define BIO_CTRL_INFO 3
  
  // BIO_CTRL_GET_CLOSE returns the close flag set by |BIO_CTRL_SET_CLOSE|. The
  // arguments are unused.
  #define BIO_CTRL_GET_CLOSE 8
  
  // BIO_CTRL_SET_CLOSE implements |BIO_set_close|. The |larg| argument is the
  // close flag.
  #define BIO_CTRL_SET_CLOSE 9
  
  // BIO_CTRL_PENDING implements |BIO_pending|. The arguments are unused.
  #define BIO_CTRL_PENDING 10
  
  // BIO_CTRL_FLUSH implements |BIO_flush|. The arguments are unused.
  #define BIO_CTRL_FLUSH 11
  
  // BIO_CTRL_WPENDING implements |BIO_wpending|. The arguments are unused.
  #define BIO_CTRL_WPENDING 13
  
  // BIO_CTRL_SET_CALLBACK sets an informational callback of type
  // int cb(BIO *bio, int state, int ret)
  #define BIO_CTRL_SET_CALLBACK 14
  
  // BIO_CTRL_GET_CALLBACK returns the callback set by |BIO_CTRL_SET_CALLBACK|.
  #define BIO_CTRL_GET_CALLBACK 15
  
  // The following are never used, but are defined to aid porting existing code.
  #define BIO_CTRL_SET 4
  #define BIO_CTRL_GET 5
  #define BIO_CTRL_PUSH 6
  #define BIO_CTRL_POP 7
  #define BIO_CTRL_DUP 12
  #define BIO_CTRL_SET_FILENAME 30
  
  
  // Deprecated functions.
  
  // BIO_f_base64 returns a filter |BIO| that base64-encodes data written into
  // it, and decodes data read from it. |BIO_gets| is not supported. Call
  // |BIO_flush| when done writing, to signal that no more data are to be
  // encoded. The flag |BIO_FLAGS_BASE64_NO_NL| may be set to encode all the data
  // on one line.
  //
  // Use |EVP_EncodeBlock| and |EVP_DecodeBase64| instead.
  OPENSSL_EXPORT const BIO_METHOD *BIO_f_base64(void);
  
  OPENSSL_EXPORT void BIO_set_retry_special(BIO *bio);
  
  // BIO_set_write_buffer_size returns zero.
  OPENSSL_EXPORT int BIO_set_write_buffer_size(BIO *bio, int buffer_size);
  
  // BIO_set_shutdown sets a method-specific "shutdown" bit on |bio|.
  OPENSSL_EXPORT void BIO_set_shutdown(BIO *bio, int shutdown);
  
  // BIO_get_shutdown returns the method-specific "shutdown" bit.
  OPENSSL_EXPORT int BIO_get_shutdown(BIO *bio);
  
  // BIO_meth_set_puts returns one. |BIO_puts| is implemented with |BIO_write| in
  // BoringSSL.
  OPENSSL_EXPORT int BIO_meth_set_puts(BIO_METHOD *method,
                                       int (*puts)(BIO *, const char *));
  
  
  // Private functions
  
  #define BIO_FLAGS_READ 0x01
  #define BIO_FLAGS_WRITE 0x02
  #define BIO_FLAGS_IO_SPECIAL 0x04
  #define BIO_FLAGS_RWS (BIO_FLAGS_READ | BIO_FLAGS_WRITE | BIO_FLAGS_IO_SPECIAL)
  #define BIO_FLAGS_SHOULD_RETRY 0x08
  #define BIO_FLAGS_BASE64_NO_NL 0x100
  // BIO_FLAGS_MEM_RDONLY is used with memory BIOs. It means we shouldn't free up
  // or change the data in any way.
  #define BIO_FLAGS_MEM_RDONLY 0x200
  
  // These are the 'types' of BIOs
  #define BIO_TYPE_NONE 0
  #define BIO_TYPE_MEM (1 | 0x0400)
  #define BIO_TYPE_FILE (2 | 0x0400)
  #define BIO_TYPE_FD (4 | 0x0400 | 0x0100)
  #define BIO_TYPE_SOCKET (5 | 0x0400 | 0x0100)
  #define BIO_TYPE_NULL (6 | 0x0400)
  #define BIO_TYPE_SSL (7 | 0x0200)
  #define BIO_TYPE_MD (8 | 0x0200)                 // passive filter
  #define BIO_TYPE_BUFFER (9 | 0x0200)             // filter
  #define BIO_TYPE_CIPHER (10 | 0x0200)            // filter
  #define BIO_TYPE_BASE64 (11 | 0x0200)            // filter
  #define BIO_TYPE_CONNECT (12 | 0x0400 | 0x0100)  // socket - connect
  #define BIO_TYPE_ACCEPT (13 | 0x0400 | 0x0100)   // socket for accept
  #define BIO_TYPE_PROXY_CLIENT (14 | 0x0200)      // client proxy BIO
  #define BIO_TYPE_PROXY_SERVER (15 | 0x0200)      // server proxy BIO
  #define BIO_TYPE_NBIO_TEST (16 | 0x0200)         // server proxy BIO
  #define BIO_TYPE_NULL_FILTER (17 | 0x0200)
  #define BIO_TYPE_BER (18 | 0x0200)         // BER -> bin filter
  #define BIO_TYPE_BIO (19 | 0x0400)         // (half a) BIO pair
  #define BIO_TYPE_LINEBUFFER (20 | 0x0200)  // filter
  #define BIO_TYPE_DGRAM (21 | 0x0400 | 0x0100)
  #define BIO_TYPE_ASN1 (22 | 0x0200)  // filter
  #define BIO_TYPE_COMP (23 | 0x0200)  // filter
  
  // BIO_TYPE_DESCRIPTOR denotes that the |BIO| responds to the |BIO_C_SET_FD|
  // (|BIO_set_fd|) and |BIO_C_GET_FD| (|BIO_get_fd|) control hooks.
  #define BIO_TYPE_DESCRIPTOR 0x0100  // socket, fd, connect or accept
  #define BIO_TYPE_FILTER 0x0200
  #define BIO_TYPE_SOURCE_SINK 0x0400
  
  // BIO_TYPE_START is the first user-allocated |BIO| type. No pre-defined type,
  // flag bits aside, may exceed this value.
  #define BIO_TYPE_START 128
  
  struct bio_method_st {
    int type;
    const char *name;
    int (*bwrite)(BIO *, const char *, int);
    int (*bread)(BIO *, char *, int);
    // TODO(fork): remove bputs.
    int (*bputs)(BIO *, const char *);
    int (*bgets)(BIO *, char *, int);
    long (*ctrl)(BIO *, int, long, void *);
    int (*create)(BIO *);
    int (*destroy)(BIO *);
    long (*callback_ctrl)(BIO *, int, bio_info_cb);
  };
  
  struct bio_st {
    const BIO_METHOD *method;
  
    // init is non-zero if this |BIO| has been initialised.
    int init;
    // shutdown is often used by specific |BIO_METHOD|s to determine whether
    // they own some underlying resource. This flag can often by controlled by
    // |BIO_set_close|. For example, whether an fd BIO closes the underlying fd
    // when it, itself, is closed.
    int shutdown;
    int flags;
    int retry_reason;
    // num is a BIO-specific value. For example, in fd BIOs it's used to store a
    // file descriptor.
    int num;
    CRYPTO_refcount_t references;
    void *ptr;
    // next_bio points to the next |BIO| in a chain. This |BIO| owns a reference
    // to |next_bio|.
    BIO *next_bio;  // used by filter BIOs
    size_t num_read, num_write;
  };
  
  #define BIO_C_SET_CONNECT 100
  #define BIO_C_DO_STATE_MACHINE 101
  #define BIO_C_SET_NBIO 102
  #define BIO_C_SET_PROXY_PARAM 103
  #define BIO_C_SET_FD 104
  #define BIO_C_GET_FD 105
  #define BIO_C_SET_FILE_PTR 106
  #define BIO_C_GET_FILE_PTR 107
  #define BIO_C_SET_FILENAME 108
  #define BIO_C_SET_SSL 109
  #define BIO_C_GET_SSL 110
  #define BIO_C_SET_MD 111
  #define BIO_C_GET_MD 112
  #define BIO_C_GET_CIPHER_STATUS 113
  #define BIO_C_SET_BUF_MEM 114
  #define BIO_C_GET_BUF_MEM_PTR 115
  #define BIO_C_GET_BUFF_NUM_LINES 116
  #define BIO_C_SET_BUFF_SIZE 117
  #define BIO_C_SET_ACCEPT 118
  #define BIO_C_SSL_MODE 119
  #define BIO_C_GET_MD_CTX 120
  #define BIO_C_GET_PROXY_PARAM 121
  #define BIO_C_SET_BUFF_READ_DATA 122  // data to read first
  #define BIO_C_GET_ACCEPT 124
  #define BIO_C_SET_SSL_RENEGOTIATE_BYTES 125
  #define BIO_C_GET_SSL_NUM_RENEGOTIATES 126
  #define BIO_C_SET_SSL_RENEGOTIATE_TIMEOUT 127
  #define BIO_C_FILE_SEEK 128
  #define BIO_C_GET_CIPHER_CTX 129
  #define BIO_C_SET_BUF_MEM_EOF_RETURN 130  // return end of input value
  #define BIO_C_SET_BIND_MODE 131
  #define BIO_C_GET_BIND_MODE 132
  #define BIO_C_FILE_TELL 133
  #define BIO_C_GET_SOCKS 134
  #define BIO_C_SET_SOCKS 135
  
  #define BIO_C_SET_WRITE_BUF_SIZE 136  // for BIO_s_bio
  #define BIO_C_GET_WRITE_BUF_SIZE 137
  #define BIO_C_GET_WRITE_GUARANTEE 140
  #define BIO_C_GET_READ_REQUEST 141
  #define BIO_C_SHUTDOWN_WR 142
  #define BIO_C_NREAD0 143
  #define BIO_C_NREAD 144
  #define BIO_C_NWRITE0 145
  #define BIO_C_NWRITE 146
  #define BIO_C_RESET_READ_REQUEST 147
  #define BIO_C_SET_MD_CTX 148
  
  #define BIO_C_SET_PREFIX 149
  #define BIO_C_GET_PREFIX 150
  #define BIO_C_SET_SUFFIX 151
  #define BIO_C_GET_SUFFIX 152
  
  #define BIO_C_SET_EX_ARG 153
  #define BIO_C_GET_EX_ARG 154
  
  
  #if defined(__cplusplus)
  }  // extern C
  
  extern "C++" {
  
  BSSL_NAMESPACE_BEGIN
  
  BORINGSSL_MAKE_DELETER(BIO, BIO_free)
  BORINGSSL_MAKE_UP_REF(BIO, BIO_up_ref)
  BORINGSSL_MAKE_DELETER(BIO_METHOD, BIO_meth_free)
  
  BSSL_NAMESPACE_END
  
  }  // extern C++
  
  #endif
  
  #define BIO_R_BAD_FOPEN_MODE 100
  #define BIO_R_BROKEN_PIPE 101
  #define BIO_R_CONNECT_ERROR 102
  #define BIO_R_ERROR_SETTING_NBIO 103
  #define BIO_R_INVALID_ARGUMENT 104
  #define BIO_R_IN_USE 105
  #define BIO_R_KEEPALIVE 106
  #define BIO_R_NBIO_CONNECT_ERROR 107
  #define BIO_R_NO_HOSTNAME_SPECIFIED 108
  #define BIO_R_NO_PORT_SPECIFIED 109
  #define BIO_R_NO_SUCH_FILE 110
  #define BIO_R_NULL_PARAMETER 111
  #define BIO_R_SYS_LIB 112
  #define BIO_R_UNABLE_TO_CREATE_SOCKET 113
  #define BIO_R_UNINITIALIZED 114
  #define BIO_R_UNSUPPORTED_METHOD 115
  #define BIO_R_WRITE_TO_READ_ONLY_BIO 116
  
  #endif  // OPENSSL_HEADER_BIO_H
  