1=pod 2 3=head1 NAME 4 5BIO_s_secmem, 6BIO_s_mem, BIO_set_mem_eof_return, BIO_get_mem_data, BIO_set_mem_buf, 7BIO_get_mem_ptr, BIO_new_mem_buf - memory BIO 8 9=head1 SYNOPSIS 10 11 #include <openssl/bio.h> 12 13 const BIO_METHOD *BIO_s_mem(void); 14 const BIO_METHOD *BIO_s_secmem(void); 15 16 BIO_set_mem_eof_return(BIO *b, int v) 17 long BIO_get_mem_data(BIO *b, char **pp) 18 BIO_set_mem_buf(BIO *b, BUF_MEM *bm, int c) 19 BIO_get_mem_ptr(BIO *b, BUF_MEM **pp) 20 21 BIO *BIO_new_mem_buf(const void *buf, int len); 22 23=head1 DESCRIPTION 24 25BIO_s_mem() returns the memory BIO method function. 26 27A memory BIO is a source/sink BIO which uses memory for its I/O. Data 28written to a memory BIO is stored in a BUF_MEM structure which is extended 29as appropriate to accommodate the stored data. 30 31BIO_s_secmem() is like BIO_s_mem() except that the secure heap is used 32for buffer storage. 33 34Any data written to a memory BIO can be recalled by reading from it. 35Unless the memory BIO is read only any data read from it is deleted from 36the BIO. 37 38Memory BIOs support BIO_gets() and BIO_puts(). 39 40If the BIO_CLOSE flag is set when a memory BIO is freed then the underlying 41BUF_MEM structure is also freed. 42 43Calling BIO_reset() on a read write memory BIO clears any data in it if the 44flag BIO_FLAGS_NONCLEAR_RST is not set. On a read only BIO or if the flag 45BIO_FLAGS_NONCLEAR_RST is set it restores the BIO to its original state and 46the data can be read again. 47 48BIO_eof() is true if no data is in the BIO. 49 50BIO_ctrl_pending() returns the number of bytes currently stored. 51 52BIO_set_mem_eof_return() sets the behaviour of memory BIO B<b> when it is 53empty. If the B<v> is zero then an empty memory BIO will return EOF (that is 54it will return zero and BIO_should_retry(b) will be false. If B<v> is non 55zero then it will return B<v> when it is empty and it will set the read retry 56flag (that is BIO_read_retry(b) is true). To avoid ambiguity with a normal 57positive return value B<v> should be set to a negative value, typically -1. 58 59BIO_get_mem_data() sets *B<pp> to a pointer to the start of the memory BIOs data 60and returns the total amount of data available. It is implemented as a macro. 61 62BIO_set_mem_buf() sets the internal BUF_MEM structure to B<bm> and sets the 63close flag to B<c>, that is B<c> should be either BIO_CLOSE or BIO_NOCLOSE. 64It is a macro. 65 66BIO_get_mem_ptr() places the underlying BUF_MEM structure in *B<pp>. It is 67a macro. 68 69BIO_new_mem_buf() creates a memory BIO using B<len> bytes of data at B<buf>, 70if B<len> is -1 then the B<buf> is assumed to be nul terminated and its 71length is determined by B<strlen>. The BIO is set to a read only state and 72as a result cannot be written to. This is useful when some data needs to be 73made available from a static area of memory in the form of a BIO. The 74supplied data is read directly from the supplied buffer: it is B<not> copied 75first, so the supplied area of memory must be unchanged until the BIO is freed. 76 77=head1 NOTES 78 79Writes to memory BIOs will always succeed if memory is available: that is 80their size can grow indefinitely. 81 82Every read from a read write memory BIO will remove the data just read with 83an internal copy operation, if a BIO contains a lot of data and it is 84read in small chunks the operation can be very slow. The use of a read only 85memory BIO avoids this problem. If the BIO must be read write then adding 86a buffering BIO to the chain will speed up the process. 87 88Calling BIO_set_mem_buf() on a BIO created with BIO_new_secmem() will 89give undefined results, including perhaps a program crash. 90 91=head1 BUGS 92 93There should be an option to set the maximum size of a memory BIO. 94 95=head1 EXAMPLE 96 97Create a memory BIO and write some data to it: 98 99 BIO *mem = BIO_new(BIO_s_mem()); 100 101 BIO_puts(mem, "Hello World\n"); 102 103Create a read only memory BIO: 104 105 char data[] = "Hello World"; 106 BIO *mem = BIO_new_mem_buf(data, -1); 107 108Extract the BUF_MEM structure from a memory BIO and then free up the BIO: 109 110 BUF_MEM *bptr; 111 112 BIO_get_mem_ptr(mem, &bptr); 113 BIO_set_close(mem, BIO_NOCLOSE); /* So BIO_free() leaves BUF_MEM alone */ 114 BIO_free(mem); 115 116=head1 RETURN VALUES 117 118BIO_s_mem() and BIO_s_secmem() return a valid memory B<BIO_METHOD> structure. 119 120BIO_set_mem_eof_return(), BIO_get_mem_data(), BIO_set_mem_buf() and BIO_get_mem_ptr() 121return 1 on success or a value which is less than or equal to 0 if an error occurred. 122 123BIO_new_mem_buf() returns a valid B<BIO> structure on success or NULL on error. 124 125=head1 COPYRIGHT 126 127Copyright 2000-2018 The OpenSSL Project Authors. All Rights Reserved. 128 129Licensed under the OpenSSL license (the "License"). You may not use 130this file except in compliance with the License. You can obtain a copy 131in the file LICENSE in the source distribution or at 132L<https://www.openssl.org/source/license.html>. 133 134=cut 135