include/openssl/bio.h

/* 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 <openssl/base.h>

#include <stdio.h>  /* For FILE */

#include <openssl/err.h> /* for ERR_print_errors_fp */
#include <openssl/ex_data.h>
#include <openssl/stack.h>
#include <openssl/thread.h>

#if defined(__cplusplus)
extern "C" {
#endif


/* BIO abstracts over a file-descriptor like interface. */


/* Allocation and freeing. */

/* BIO_new creates a new BIO with the given type and a reference count of one.
 * It returns the fresh |BIO|, or NULL on error. */
OPENSSL_EXPORT BIO *BIO_new(const BIO_METHOD *type);

/* BIO_free decrements the reference count of |bio|. If the reference count
 * drops to zero, it (optionally) calls the BIO's callback with |BIO_CB_FREE|,
 * frees the ex_data and then, if the BIO has a destroy callback for the
 * method, calls it. Finally it 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 it. */
OPENSSL_EXPORT BIO *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_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_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_SSL_X509_LOOKUP indicates that an SSL BIO blocked because the SSL
 * library returned with SSL_ERROR_WANT_X509_LOOKUP.
 *
 * TODO(fork): remove. */
#define BIO_RR_SSL_X509_LOOKUP 0x01

/* 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_RR_SSL_CHANNEL_ID_LOOKUP indicates that the ChannelID code cannot find
 * a private key for a TLS connection. */
#define BIO_RR_SSL_CHANNEL_ID_LOOKUP 0x04

/* 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_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);

/* 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 arbitary 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_set_callback sets a callback function that will be called before and
 * after most operations. See the comment above |bio_info_cb|. */
OPENSSL_EXPORT void BIO_set_callback(BIO *bio, bio_info_cb callback_func);

/* BIO_set_callback_arg sets the opaque pointer value that can be read within a
 * callback with |BIO_get_callback_arg|. */
OPENSSL_EXPORT void BIO_set_callback_arg(BIO *bio, char *arg);

/* BIO_get_callback_arg returns the last value of the opaque callback pointer
 * set by |BIO_set_callback_arg|. */
OPENSSL_EXPORT char *BIO_get_callback_arg(const BIO *bio);

/* 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);

/* BIO_print_errors prints the current contents of the error stack to |bio|
 * using human readable strings where possible. */
OPENSSL_EXPORT void BIO_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_get_mem_buf|). 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_eof| is true if no data is in the BIO.
 *
 * |BIO_ctrl_pending| returns the number of bytes currently stored. */

/* 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 BIO that reads and writes from |len| bytes at |buf|.
 * It does not take ownership of |buf|. It returns the BIO or NULL on error.
 *
 * 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(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_seek| sets the file pointer to position |off| from start of file using
 * |lseek|.
 *
 * |BIO_tell| returns the current file position. */

/* 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. */
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. */
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|.
 *
 * |BIO_seek| sets the file pointer to the given position from the start of
 * file using |fseek|.
 *
 * |BIO_eof| calls |feof|.
 *
 * 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
 * sucess 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);


/* Buffer BIOs.
 *
 * Buffer BIOs are a filter-type BIO, i.e. they are designed to be used in a
 * chain of BIOs. They provide buffering to reduce the number of operations on
 * the underlying BIOs. */

OPENSSL_EXPORT const BIO_METHOD *BIO_f_buffer(void);

/* BIO_set_read_buffer_size sets the size, in bytes, of the read buffer and
 * clears it. It returns one on success and zero on failure. */
OPENSSL_EXPORT int BIO_set_read_buffer_size(BIO *bio, int buffer_size);

/* BIO_set_write_buffer_size sets the size, in bytes, of the write buffer and
 * clears it. It returns one on success and zero on failure. */
OPENSSL_EXPORT int BIO_set_write_buffer_size(BIO *bio, int buffer_size);


/* Socket BIOs. */

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_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);


/* 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. */

#define BIO_CTRL_DGRAM_SET_NEXT_TIMEOUT \
  45 /* Next DTLS handshake timeout to adjust socket timeouts */

#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_new_bio_pair_external_buf is the same as |BIO_new_bio_pair| with the
 * difference that the caller keeps ownership of the write buffers
 * |ext_writebuf1_len| and |ext_writebuf2_len|. This is useful when using zero
 * copy API for read and write operations, in cases where the buffers need to
 * outlive the BIO pairs. It returns one on success and zero on error. */
OPENSSL_EXPORT int BIO_new_bio_pair_external_buf(BIO** bio1_p,
                                                 size_t writebuf1_len,
                                                 uint8_t* ext_writebuf1,
                                                 BIO** bio2_p,
                                                 size_t writebuf2_len,
                                                 uint8_t* ext_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);


/* Zero copy versions of BIO_read and BIO_write for BIO pairs. */

/* BIO_zero_copy_get_read_buf initiates a zero copy read operation.
 * |out_read_buf| is set to the internal read buffer, and |out_buf_offset| is
 * set to the current read position of |out_read_buf|. The number of bytes
 * available for read from |out_read_buf| + |out_buf_offset| is returned in
 * |out_available_bytes|. Note that this function might report fewer bytes
 * available than |BIO_pending|, if the internal ring buffer is wrapped. It
 * returns one on success. In case of error it returns zero and pushes to the
 * error stack.
 *
 * The zero copy read operation is completed by calling
 * |BIO_zero_copy_get_read_buf_done|. Neither |BIO_zero_copy_get_read_buf| nor
 * any other I/O read operation may be called while a zero copy read operation
 * is active. */
OPENSSL_EXPORT int BIO_zero_copy_get_read_buf(BIO* bio,
                                              uint8_t** out_read_buf,
                                              size_t* out_buf_offset,
                                              size_t* out_available_bytes);

/* BIO_zero_copy_get_read_buf_done must be called after reading from a BIO using
 * |BIO_zero_copy_get_read_buf| to finish the read operation. The |bytes_read|
 * argument is the number of bytes read.
 *
 * It returns one on success. In case of error it returns zero and pushes to the
 * error stack. */
OPENSSL_EXPORT int BIO_zero_copy_get_read_buf_done(BIO* bio, size_t bytes_read);

/* BIO_zero_copy_get_write_buf initiates a zero copy write operation.
 * |out_write_buf| is set to to the internal write buffer, and |out_buf_offset|
 * is set to the current write position of |out_write_buf|.
 * The number of bytes available for write from |out_write_buf| +
 * |out_buf_offset| is returned in |out_available_bytes|. Note that this
 * function might report fewer bytes available than
 * |BIO_ctrl_get_write_guarantee|, if the internal buffer is wrapped. It returns
 * one on success. In case of error it returns zero and pushes to the error
 * stack.
 *
 * The zero copy write operation is completed by calling
 * |BIO_zero_copy_get_write_buf_done|. Neither |BIO_zero_copy_get_write_buf|
 * nor any other I/O write operation may be called while a zero copy write
 * operation is active. */
OPENSSL_EXPORT int BIO_zero_copy_get_write_buf(BIO* bio,
                                               uint8_t** out_write_buf,
                                               size_t* out_buf_offset,
                                               size_t* out_available_bytes);

/* BIO_zero_copy_get_write_buf_done must be called after writing to a BIO using
 * |BIO_zero_copy_get_write_buf| to finish the write operation. The
 * |bytes_written| argument gives the number of bytes written.
 *
 * It returns one on success. In case of error it returns zero and pushes to the
 * error stack. */
OPENSSL_EXPORT int BIO_zero_copy_get_write_buf_done(BIO* bio,
                                                    size_t bytes_written);


/* 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

/* 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

/* These are values of the |cmd| argument to |BIO_ctrl|. */
#define BIO_CTRL_RESET		1  /* opt - rewind/zero etc */
#define BIO_CTRL_EOF		2  /* opt - are we at the eof */
#define BIO_CTRL_INFO		3  /* opt - extra tit-bits */
#define BIO_CTRL_SET		4  /* man - set the 'IO' type */
#define BIO_CTRL_GET		5  /* man - get the 'IO' type */
#define BIO_CTRL_GET_CLOSE	8  /* man - set the 'close' on free */
#define BIO_CTRL_SET_CLOSE	9  /* man - set the 'close' on free */
#define BIO_CTRL_PENDING	10  /* opt - is their more data buffered */
#define BIO_CTRL_FLUSH		11  /* opt - 'flush' buffered output */
#define BIO_CTRL_WPENDING	13  /* opt - number of bytes still to write */
/* callback is int cb(BIO *bio,state,ret); */
#define BIO_CTRL_SET_CALLBACK	14  /* opt - set callback function */
#define BIO_CTRL_GET_CALLBACK	15  /* opt - set callback function */
#define BIO_CTRL_SET_FILENAME	30	/* BIO_s_file special */


/* Android compatibility section.
 *
 * A previous version of BoringSSL used in Android renamed ERR_print_errors_fp
 * to BIO_print_errors_fp. It has subsequently been renamed back to
 * ERR_print_errors_fp. */
#define BIO_print_errors_fp ERR_print_errors_fp


/* 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. */
OPENSSL_EXPORT const BIO_METHOD *BIO_f_base64(void);

/* ERR_print_errors is an alias for |BIO_print_errors|. */
OPENSSL_EXPORT void ERR_print_errors(BIO *bio);


/* 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
/* This 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 */

#define BIO_TYPE_DESCRIPTOR 0x0100 /* socket, fd, connect or accept */
#define BIO_TYPE_FILTER 0x0200
#define BIO_TYPE_SOURCE_SINK 0x0400

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;
  /* bio, mode, argp, argi, argl, ret */
  long (*callback)(BIO *, int, const char *, int, long, long);
  char *cb_arg; /* first argument for the callback */

  /* 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 */
#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 */