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Title "BIO_s_mem 3"
way too many mistakes in technical documents.
.nh
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.
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
Memory BIOs support BIO_gets() and BIO_puts().
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.
Calling BIO_reset() 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.
\fIBIO_eof() is true if no data is in the \s-1BIO.\s0
\fIBIO_ctrl_pending() returns the number of bytes currently stored.
\fIBIO_set_mem_eof_return() sets the behaviour of memory \s-1BIO \s0b when it is empty. If the v 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 v is non zero then it will return v 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 v should be set to a negative value, typically -1.
\fIBIO_get_mem_data() sets pp 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.
\fIBIO_set_mem_buf() sets the internal \s-1BUF_MEM\s0 structure to bm and sets the close flag to c, that is c should be either \s-1BIO_CLOSE\s0 or \s-1BIO_NOCLOSE.\s0 It is a macro.
\fIBIO_get_mem_ptr() places the underlying \s-1BUF_MEM\s0 structure in pp. It is a macro.
\fIBIO_new_mem_buf() creates a memory \s-1BIO\s0 using len bytes of data at buf, if len is -1 then the buf is assumed to be nul terminated and its length is determined by strlen. 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 not copied first, so the supplied area of memory must be unchanged until the \s-1BIO\s0 is freed.
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.
There should be a way to \*(L"rewind\*(R" a read write \s-1BIO\s0 without destroying its contents.
The copying operation should not occur after every small read of a large \s-1BIO\s0 to improve efficiency.
.Vb 2 BIO *mem = BIO_new(BIO_s_mem()); BIO_puts(mem, "Hello World\en"); .Ve
Create a read only memory \s-1BIO:\s0
.Vb 3 char data[] = "Hello World"; BIO *mem; mem = BIO_new_mem_buf(data, -1); .Ve
Extract the \s-1BUF_MEM\s0 structure from a memory \s-1BIO\s0 and then free up the \s-1BIO:\s0
.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
Indexes created Sun Apr 26 00:22:38 UTC 2026