HP OpenVMS Systems Documentation

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HP Open Source Security for OpenVMS Volume 2: HP SSL for OpenVMS > CRYPTO Application Programming Interface (API) Reference


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


#include <openssl/buffer.h>
BUF_MEM *BUF_MEM_new(void);
void BUF_MEM_free(BUF_MEM *a);
int BUF_MEM_grow(BUF_MEM *str, int len);
char * BUF_strdup(const char *str);


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 */

length is the current size of the buffer in bytes, 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_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 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.


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. len).




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.