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BIO_get_mem_data.3ssl
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Always turn off hyphenation; it makes .\" way too many mistakes in technical documents. .if n .ad l .nh .SH "NAME" BIO_s_mem, BIO_set_mem_eof_return, BIO_get_mem_data, BIO_set_mem_buf, BIO_get_mem_ptr, BIO_new_mem_buf \- memory BIO .SH "SYNOPSIS" .IX Header "SYNOPSIS" .Vb 1 \& #include <openssl/bio.h> \& \& BIO_METHOD * BIO_s_mem(void); \& \& BIO_set_mem_eof_return(BIO *b,int v) \& long BIO_get_mem_data(BIO *b, char **pp) \& BIO_set_mem_buf(BIO *b,BUF_MEM *bm,int c) \& BIO_get_mem_ptr(BIO *b,BUF_MEM **pp) \& \& BIO *BIO_new_mem_buf(const void *buf, int len); .Ve .SH "DESCRIPTION" .IX Header "DESCRIPTION" \&\fBBIO_s_mem()\fR return the memory \s-1BIO\s0 method function. .PP A memory \s-1BIO\s0 is a source/sink \s-1BIO\s0 which uses memory for its I/O. Data written to a memory \s-1BIO\s0 is stored in a \s-1BUF_MEM\s0 structure which is extended as appropriate to accommodate the stored data. .PP Any data written to a memory \s-1BIO\s0 can be recalled by reading from it. Unless the memory \s-1BIO\s0 is read only any data read from it is deleted from the \s-1BIO.\s0 .PP Memory BIOs support \fBBIO_gets()\fR and \fBBIO_puts()\fR. .PP If the \s-1BIO_CLOSE\s0 flag is set when a memory \s-1BIO\s0 is freed then the underlying \&\s-1BUF_MEM\s0 structure is also freed. .PP Calling \fBBIO_reset()\fR on a read write memory \s-1BIO\s0 clears any data in it. On a read only \s-1BIO\s0 it restores the \s-1BIO\s0 to its original state and the read only data can be read again. .PP \&\fBBIO_eof()\fR is true if no data is in the \s-1BIO.\s0 .PP \&\fBBIO_ctrl_pending()\fR returns the number of bytes currently stored. .PP \&\fBBIO_set_mem_eof_return()\fR sets the behaviour of memory \s-1BIO\s0 \fBb\fR when it is empty. If the \fBv\fR is zero then an empty memory \s-1BIO\s0 will return \s-1EOF\s0 (that is it will return zero and BIO_should_retry(b) will be false. If \fBv\fR is non zero then it will return \fBv\fR when it is empty and it will set the read retry flag (that is BIO_read_retry(b) is true). To avoid ambiguity with a normal positive return value \fBv\fR should be set to a negative value, typically \-1. .PP \&\fBBIO_get_mem_data()\fR sets *\fBpp\fR to a pointer to the start of the memory BIOs data and returns the total amount of data available. It is implemented as a macro. .PP \&\fBBIO_set_mem_buf()\fR sets the internal \s-1BUF_MEM\s0 structure to \fBbm\fR and sets the close flag to \fBc\fR, that is \fBc\fR should be either \s-1BIO_CLOSE\s0 or \s-1BIO_NOCLOSE.\s0 It is a macro. .PP \&\fBBIO_get_mem_ptr()\fR places the underlying \s-1BUF_MEM\s0 structure in *\fBpp\fR. It is a macro. .PP \&\fBBIO_new_mem_buf()\fR creates a memory \s-1BIO\s0 using \fBlen\fR bytes of data at \fBbuf\fR, if \fBlen\fR is \-1 then the \fBbuf\fR is assumed to be nul terminated and its length is determined by \fBstrlen\fR. The \s-1BIO\s0 is set to a read only state and as a result cannot be written to. This is useful when some data needs to be made available from a static area of memory in the form of a \s-1BIO.\s0 The supplied data is read directly from the supplied buffer: it is \fBnot\fR copied first, so the supplied area of memory must be unchanged until the \s-1BIO\s0 is freed. .SH "NOTES" .IX Header "NOTES" Writes to memory BIOs will always succeed if memory is available: that is their size can grow indefinitely. .PP Every read from a read write memory \s-1BIO\s0 will remove the data just read with an internal copy operation, if a \s-1BIO\s0 contains a lot of data and it is read in small chunks the operation can be very slow. The use of a read only memory \s-1BIO\s0 avoids this problem. If the \s-1BIO\s0 must be read write then adding a buffering \s-1BIO\s0 to the chain will speed up the process. .SH "BUGS" .IX Header "BUGS" There should be an option to set the maximum size of a memory \s-1BIO.\s0 .PP There should be a way to \*(L"rewind\*(R" a read write \s-1BIO\s0 without destroying its contents. .PP The copying operation should not occur after every small read of a large \s-1BIO\s0 to improve efficiency. .SH "EXAMPLE" .IX Header "EXAMPLE" Create a memory \s-1BIO\s0 and write some data to it: .PP .Vb 2 \& BIO *mem = BIO_new(BIO_s_mem()); \& BIO_puts(mem, "Hello World\en"); .Ve .PP Create a read only memory \s-1BIO:\s0 .PP .Vb 3 \& char data[] = "Hello World"; \& BIO *mem; \& mem = BIO_new_mem_buf(data, \-1); .Ve .PP Extract the \s-1BUF_MEM\s0 structure from a memory \s-1BIO\s0 and then free up the \s-1BIO:\s0 .PP .Vb 4 \& BUF_MEM *bptr; \& BIO_get_mem_ptr(mem, &bptr); \& BIO_set_close(mem, BIO_NOCLOSE); /* So BIO_free() leaves BUF_MEM alone */ \& BIO_free(mem); .Ve .SH "SEE ALSO" .IX Header "SEE ALSO" \&\s-1TBA\s0
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