1*2175Sjp161948=pod 2*2175Sjp161948 3*2175Sjp161948=head1 NAME 4*2175Sjp161948 5*2175Sjp161948BIO_s_mem, BIO_set_mem_eof_return, BIO_get_mem_data, BIO_set_mem_buf, 6*2175Sjp161948BIO_get_mem_ptr, BIO_new_mem_buf - memory BIO 7*2175Sjp161948 8*2175Sjp161948=head1 SYNOPSIS 9*2175Sjp161948 10*2175Sjp161948 #include <openssl/bio.h> 11*2175Sjp161948 12*2175Sjp161948 BIO_METHOD * BIO_s_mem(void); 13*2175Sjp161948 14*2175Sjp161948 BIO_set_mem_eof_return(BIO *b,int v) 15*2175Sjp161948 long BIO_get_mem_data(BIO *b, char **pp) 16*2175Sjp161948 BIO_set_mem_buf(BIO *b,BUF_MEM *bm,int c) 17*2175Sjp161948 BIO_get_mem_ptr(BIO *b,BUF_MEM **pp) 18*2175Sjp161948 19*2175Sjp161948 BIO *BIO_new_mem_buf(void *buf, int len); 20*2175Sjp161948 21*2175Sjp161948=head1 DESCRIPTION 22*2175Sjp161948 23*2175Sjp161948BIO_s_mem() return the memory BIO method function. 24*2175Sjp161948 25*2175Sjp161948A memory BIO is a source/sink BIO which uses memory for its I/O. Data 26*2175Sjp161948written to a memory BIO is stored in a BUF_MEM structure which is extended 27*2175Sjp161948as appropriate to accommodate the stored data. 28*2175Sjp161948 29*2175Sjp161948Any data written to a memory BIO can be recalled by reading from it. 30*2175Sjp161948Unless the memory BIO is read only any data read from it is deleted from 31*2175Sjp161948the BIO. 32*2175Sjp161948 33*2175Sjp161948Memory BIOs support BIO_gets() and BIO_puts(). 34*2175Sjp161948 35*2175Sjp161948If the BIO_CLOSE flag is set when a memory BIO is freed then the underlying 36*2175Sjp161948BUF_MEM structure is also freed. 37*2175Sjp161948 38*2175Sjp161948Calling BIO_reset() on a read write memory BIO clears any data in it. On a 39*2175Sjp161948read only BIO it restores the BIO to its original state and the read only 40*2175Sjp161948data can be read again. 41*2175Sjp161948 42*2175Sjp161948BIO_eof() is true if no data is in the BIO. 43*2175Sjp161948 44*2175Sjp161948BIO_ctrl_pending() returns the number of bytes currently stored. 45*2175Sjp161948 46*2175Sjp161948BIO_set_mem_eof_return() sets the behaviour of memory BIO B<b> when it is 47*2175Sjp161948empty. If the B<v> is zero then an empty memory BIO will return EOF (that is 48*2175Sjp161948it will return zero and BIO_should_retry(b) will be false. If B<v> is non 49*2175Sjp161948zero then it will return B<v> when it is empty and it will set the read retry 50*2175Sjp161948flag (that is BIO_read_retry(b) is true). To avoid ambiguity with a normal 51*2175Sjp161948positive return value B<v> should be set to a negative value, typically -1. 52*2175Sjp161948 53*2175Sjp161948BIO_get_mem_data() sets B<pp> to a pointer to the start of the memory BIOs data 54*2175Sjp161948and returns the total amount of data available. It is implemented as a macro. 55*2175Sjp161948 56*2175Sjp161948BIO_set_mem_buf() sets the internal BUF_MEM structure to B<bm> and sets the 57*2175Sjp161948close flag to B<c>, that is B<c> should be either BIO_CLOSE or BIO_NOCLOSE. 58*2175Sjp161948It is a macro. 59*2175Sjp161948 60*2175Sjp161948BIO_get_mem_ptr() places the underlying BUF_MEM structure in B<pp>. It is 61*2175Sjp161948a macro. 62*2175Sjp161948 63*2175Sjp161948BIO_new_mem_buf() creates a memory BIO using B<len> bytes of data at B<buf>, 64*2175Sjp161948if B<len> is -1 then the B<buf> is assumed to be null terminated and its 65*2175Sjp161948length is determined by B<strlen>. The BIO is set to a read only state and 66*2175Sjp161948as a result cannot be written to. This is useful when some data needs to be 67*2175Sjp161948made available from a static area of memory in the form of a BIO. The 68*2175Sjp161948supplied data is read directly from the supplied buffer: it is B<not> copied 69*2175Sjp161948first, so the supplied area of memory must be unchanged until the BIO is freed. 70*2175Sjp161948 71*2175Sjp161948=head1 NOTES 72*2175Sjp161948 73*2175Sjp161948Writes to memory BIOs will always succeed if memory is available: that is 74*2175Sjp161948their size can grow indefinitely. 75*2175Sjp161948 76*2175Sjp161948Every read from a read write memory BIO will remove the data just read with 77*2175Sjp161948an internal copy operation, if a BIO contains a lots of data and it is 78*2175Sjp161948read in small chunks the operation can be very slow. The use of a read only 79*2175Sjp161948memory BIO avoids this problem. If the BIO must be read write then adding 80*2175Sjp161948a buffering BIO to the chain will speed up the process. 81*2175Sjp161948 82*2175Sjp161948=head1 BUGS 83*2175Sjp161948 84*2175Sjp161948There should be an option to set the maximum size of a memory BIO. 85*2175Sjp161948 86*2175Sjp161948There should be a way to "rewind" a read write BIO without destroying 87*2175Sjp161948its contents. 88*2175Sjp161948 89*2175Sjp161948The copying operation should not occur after every small read of a large BIO 90*2175Sjp161948to improve efficiency. 91*2175Sjp161948 92*2175Sjp161948=head1 EXAMPLE 93*2175Sjp161948 94*2175Sjp161948Create a memory BIO and write some data to it: 95*2175Sjp161948 96*2175Sjp161948 BIO *mem = BIO_new(BIO_s_mem()); 97*2175Sjp161948 BIO_puts(mem, "Hello World\n"); 98*2175Sjp161948 99*2175Sjp161948Create a read only memory BIO: 100*2175Sjp161948 101*2175Sjp161948 char data[] = "Hello World"; 102*2175Sjp161948 BIO *mem; 103*2175Sjp161948 mem = BIO_new_mem_buf(data, -1); 104*2175Sjp161948 105*2175Sjp161948Extract the BUF_MEM structure from a memory BIO and then free up the BIO: 106*2175Sjp161948 107*2175Sjp161948 BUF_MEM *bptr; 108*2175Sjp161948 BIO_get_mem_ptr(mem, &bptr); 109*2175Sjp161948 BIO_set_close(mem, BIO_NOCLOSE); /* So BIO_free() leaves BUF_MEM alone */ 110*2175Sjp161948 BIO_free(mem); 111*2175Sjp161948 112*2175Sjp161948 113*2175Sjp161948=head1 SEE ALSO 114*2175Sjp161948 115*2175Sjp161948TBA 116