- NAME
- SYNOPSIS
- DESCRIPTION
- RETURN VALUES
- SEE ALSO
- HISTORY

# NAME

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

# SYNOPSIS

     #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);

# 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;

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.

# 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. len).

# SEE ALSO

bio

# 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.