openssl/doc/crypto/buffer.pod

=pod

=head1 NAME

BUF_MEM_new, BUF_MEM_free, BUF_MEM_grow, BUF_strdup - simple
character arrays structure

=head1 SYNOPSIS

 #include <openssl/buffer.h>

 BUF_MEM *BUF_MEM_new(void);

 #define BUF_MEM_FLAG_SECURE

 BUF_MEM * BUF_MEM_new_ex(unsigned long flags);

 void	BUF_MEM_free(BUF_MEM *a);

 int	BUF_MEM_grow(BUF_MEM *str, int len);

 char *	BUF_strdup(const char *str);

=head1 DESCRIPTION

The buffer library handles simple character arrays. Buffers are used for
various purposes in the library, most notably memory BIOs.

The library uses the BUF_MEM structure defined in buffer.h:

 typedef struct buf_mem_st
 {
        int length;     /* current number of bytes */
        char *data;
        int max;        /* size of buffer */
 } BUF_MEM;

B<length> is the current size of the buffer in bytes, B<max> is the amount of
memory allocated to the buffer. There are three functions which handle these
and one "miscellaneous" function.

BUF_MEM_new() allocates a new buffer of zero size.

BUF_MEM_new_ex() allocates a buffer with the specified flags.
The flag B<BUF_MEM_FLAG_SECURE> specifies that the B<data> pointer
should be allocated on the secure heap; see L<CRYPTO_secure_malloc(3)>.

BUF_MEM_free() frees up an already existing buffer. The data is zeroed
before freeing up in case the buffer contains sensitive data.

BUF_MEM_grow() changes the size of an already existing buffer to
B<len>. Any data already in the buffer is preserved if it increases in
size.

BUF_strdup() copies a null terminated string into a block of allocated
memory and returns a pointer to the allocated block.
Unlike the standard C library strdup() this function uses OPENSSL_malloc() and so
should be used in preference to the standard library strdup() because it can
be used for memory leak checking or replacing the malloc() function.

The memory allocated from BUF_strdup() should be freed up using the OPENSSL_free()
function.

=head1 RETURN VALUES

BUF_MEM_new() returns the buffer or NULL on error.

BUF_MEM_free() has no return value.

BUF_MEM_grow() returns zero on error or the new size (i.e. B<len>).

=head1 SEE ALSO

L<bio(3)|bio(3)>,
L<CRYPTO_secure_malloc(3)>.

=head1 HISTORY

BUF_MEM_new(), BUF_MEM_free() and BUF_MEM_grow() are available in all
versions of SSLeay and OpenSSL. BUF_strdup() was added in SSLeay 0.8.

BUF_MEM_new_ex() was contributed to OpenSSL by Akamai Technologies
in May, 2014.

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