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BIO_new_mem_buf.3
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.\" Automatically generated by Pod::Man 4.11 (Pod::Simple 3.35) .\" .\" Standard preamble: .\" ======================================================================== .de Sp \" Vertical space (when we can't use .PP) .if t .sp .5v .if n .sp .. .de Vb \" Begin verbatim text .ft CW .nf .ne \\$1 .. .de Ve \" End verbatim text .ft R .fi .. .\" Set up some character translations and predefined strings. \*(-- will .\" give an unbreakable dash, \*(PI will give pi, \*(L" will give a left .\" double quote, and \*(R" will give a right double quote. \*(C+ will .\" give a nicer C++. Capital omega is used to do unbreakable dashes and .\" therefore won't be available. \*(C` and \*(C' expand to `' in nroff, .\" nothing in troff, for use with C<>. .tr \(*W- .ds C+ C\v'-.1v'\h'-1p'\s-2+\h'-1p'+\s0\v'.1v'\h'-1p' .ie n \{\ . ds -- \(*W- . ds PI pi . if (\n(.H=4u)&(1m=24u) .ds -- \(*W\h'-12u'\(*W\h'-12u'-\" diablo 10 pitch . if (\n(.H=4u)&(1m=20u) .ds -- \(*W\h'-12u'\(*W\h'-8u'-\" diablo 12 pitch . ds L" "" . ds R" "" . ds C` "" . ds C' "" 'br\} .el\{\ . ds -- \|\(em\| . ds PI \(*p . ds L" `` . ds R" '' . ds C` . ds C' 'br\} .\" .\" Escape single quotes in literal strings from groff's Unicode transform. .ie \n(.g .ds Aq \(aq .el .ds Aq ' .\" .\" If the F register is >0, we'll generate index entries on stderr for .\" titles (.TH), headers (.SH), subsections (.SS), items (.Ip), and index .\" entries marked with X<> in POD. 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No user-serviceable parts. . \" fudge factors for nroff and troff .if n \{\ . ds #H 0 . ds #V .8m . ds #F .3m . ds #[ \f1 . ds #] \fP .\} .if t \{\ . ds #H ((1u-(\\\\n(.fu%2u))*.13m) . ds #V .6m . ds #F 0 . ds #[ \& . ds #] \& .\} . \" simple accents for nroff and troff .if n \{\ . ds ' \& . ds ` \& . ds ^ \& . ds , \& . ds ~ ~ . ds / .\} .if t \{\ . ds ' \\k:\h'-(\\n(.wu*8/10-\*(#H)'\'\h"|\\n:u" . ds ` \\k:\h'-(\\n(.wu*8/10-\*(#H)'\`\h'|\\n:u' . ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'^\h'|\\n:u' . ds , \\k:\h'-(\\n(.wu*8/10)',\h'|\\n:u' . ds ~ \\k:\h'-(\\n(.wu-\*(#H-.1m)'~\h'|\\n:u' . ds / \\k:\h'-(\\n(.wu*8/10-\*(#H)'\z\(sl\h'|\\n:u' .\} . \" troff and (daisy-wheel) nroff accents .ds : \\k:\h'-(\\n(.wu*8/10-\*(#H+.1m+\*(#F)'\v'-\*(#V'\z.\h'.2m+\*(#F'.\h'|\\n:u'\v'\*(#V' .ds 8 \h'\*(#H'\(*b\h'-\*(#H' .ds o \\k:\h'-(\\n(.wu+\w'\(de'u-\*(#H)/2u'\v'-.3n'\*(#[\z\(de\v'.3n'\h'|\\n:u'\*(#] .ds d- \h'\*(#H'\(pd\h'-\w'~'u'\v'-.25m'\f2\(hy\fP\v'.25m'\h'-\*(#H' .ds D- D\\k:\h'-\w'D'u'\v'-.11m'\z\(hy\v'.11m'\h'|\\n:u' .ds th \*(#[\v'.3m'\s+1I\s-1\v'-.3m'\h'-(\w'I'u*2/3)'\s-1o\s+1\*(#] .ds Th \*(#[\s+2I\s-2\h'-\w'I'u*3/5'\v'-.3m'o\v'.3m'\*(#] .ds ae a\h'-(\w'a'u*4/10)'e .ds Ae A\h'-(\w'A'u*4/10)'E . \" corrections for vroff .if v .ds ~ \\k:\h'-(\\n(.wu*9/10-\*(#H)'\s-2\u~\d\s+2\h'|\\n:u' .if v .ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'\v'-.4m'^\v'.4m'\h'|\\n:u' . \" for low resolution devices (crt and lpr) .if \n(.H>23 .if \n(.V>19 \ \{\ . ds : e . ds 8 ss . ds o a . ds d- d\h'-1'\(ga . ds D- D\h'-1'\(hy . ds th \o'bp' . ds Th \o'LP' . ds ae ae . ds Ae AE .\} .rm #[ #] #H #V #F C .\" ======================================================================== .\" .IX Title "BIO_s_mem 3" .TH BIO_s_mem 3 "2019-12-20" "1.0.2u" "OpenSSL" .\" For nroff, turn off justification. 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