Buf.cc

/***************************************************************************
 * Buf.cc -- The Buf class is reponsible for I/O buffer manipulation       *
 * and is based on the buffer code used in OpenSSH.                        *
 *                                                                         *
 ***********************IMPORTANT NMAP LICENSE TERMS************************
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 * also a registered trademark of Insecure.Com LLC.  This program is free  *
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 * included with Nmap.                                                     *
 *                                                                         *
 ***************************************************************************/

#include "Buf.h"

Buf::Buf()
{
	const u_int len = DEFAULT_BUF_SIZE;

	alloc = 0;
	buf = (u_char *)safe_malloc(len);
	alloc = len;
	offset = 0;
	end = 0;
}


/* Frees any memory used for the buffer. */
Buf::~Buf()
{
	if (alloc > 0) {
    free(buf);
    buf = NULL;
	}
}


/*
 * Clears any data from the buffer, making it empty.  This does not actually
 * zero the memory.
 */
void
Buf::clear(void)
{
	offset = 0;
	end = 0;
}


/* 
 * Similar to way snprintf works, but data get saved inside the buffer.
 * Warning: data won't get null terminated
 * the len argument is the real length of the _actual_ data
 */
void
Buf::snprintf(u_int len, const void *fmt, ...)
{

  void *p;
  va_list ap;

  /* Since vsnprintf always null terminates the data, we
   * allocate one extra byte for the trailing '\0' and then
   * drop it by decreasing 'end' by 1
   */
  p = append_space(len + 1);

  va_start(ap, fmt);
  vsnprintf((char *)p, len + 1, (char *)fmt, ap);
  va_end(ap);
  end--;

  //memcpy(p, data, len);

}



/* Appends data to the buffer, expanding it if necessary. */
void
Buf::append(const void *data, u_int len)
{
	void *p;
	p = append_space(len);
	memcpy(p, data, len);
}



/*
 * Appends space to the buffer, expanding the buffer if necessary. This does
 * not actually copy the data into the buffer, but instead returns a pointer
 * to the allocated region.
 */
void *
Buf::append_space(u_int len)
{
	u_int newlen;
	void *p;

	if (len > BUFFER_MAX_CHUNK)
		fatal("%s: len %u not supported", __func__, len);

	/* If the buffer is empty, start using it from the beginning. */
	if (offset == end) {
		offset = 0;
		end = 0;
	}
restart:
	/* If there is enough space to store all data, store it now. */
	if (end + len < alloc) {
		p = buf + end;
		end += len;
		return p;
	}

	/* Compact data back to the start of the buffer if necessary */
	if (compact())
		goto restart;

	/* Increase the size of the buffer and retry. */
	newlen = roundup(alloc + len, BUFFER_ALLOCSZ);
	if (newlen > BUFFER_MAX_LEN)
		fatal("%s: alloc %u not supported", __func__, newlen);
	buf = (u_char *)safe_realloc(buf, newlen);
	alloc = newlen;
	goto restart;
	/* NOTREACHED */
}


/*
 * Check whether an allocation of 'len' will fit in the buffer
 * This must follow the same math as buffer_append_space
 */
int
Buf::check_alloc(u_int len)
{
	if (offset == end) {
		offset = 0;
		end = 0;
	}
 restart:
	if (end + len < alloc)
		return (1);
	if (compact())
		goto restart;
	if (roundup(alloc + len, BUFFER_ALLOCSZ) <= BUFFER_MAX_LEN)
		return (1);
	return (0);
}


/* Returns the number of bytes of data in the buffer. */
u_int
Buf::get_len(void)
{
	return end - offset;
}


/* Gets data from the beginning of the buffer. */
int
Buf::get_data(void *dst, u_int len)
{
	if (len > end - offset) {
		error("%s: trying to get more bytes %d than in buffer %d",
		    __func__, len, end - offset);
		return (-1);
	}
  
  /* If dst is NULL then don't copy anything */
  if (dst)
  	memcpy(dst, buf + offset, len);

	offset += len;
	return (0);
}


int
Buf::compact(void)
{
	/*
	 * If the buffer is quite empty, but all data is at the end, move the
	 * data to the beginning.
	 */
	if (offset > MIN(alloc, BUFFER_MAX_CHUNK)) {
		memmove(buf, buf + offset, end - offset);
		end -= offset;
		offset = 0;
		return (1);
	}
	return (0);
}


/* Returns a pointer to the first used byte in the buffer. */
void *
Buf::get_dataptr(void)
{
	return buf + offset;
}


/* Dumps the contents of the buffer to stderr. */
void
Buf::data_dump(void)
{
	u_int i;
	u_char *ucp = buf;

	for (i = offset; i < end; i++) {
		fprintf(stderr, "%02x", ucp[i]);
		if ((i-offset)%16==15)
			fprintf(stderr, "\r\n");
		else if ((i-offset)%2==1)
			fprintf(stderr, " ");
	}
	fprintf(stderr, "\r\n");
}



/* Consumes the given number of bytes from the beginning of the buffer. */

#if 0
int
buffer_consume_ret(Buffer *buffer, u_int bytes)
{
	if (bytes > buffer->end - buffer->offset) {
		error("buffer_consume_ret: trying to get more bytes than in buffer");
		return (-1);
	}
	buffer->offset += bytes;
	return (0);
}

void
buffer_consume(Buffer *buffer, u_int bytes)
{
	if (buffer_consume_ret(buffer, bytes) == -1)
		fatal("buffer_consume: buffer error");
}

/* Consumes the given number of bytes from the end of the buffer. */

int
buffer_consume_end_ret(Buffer *buffer, u_int bytes)
{
	if (bytes > buffer->end - buffer->offset)
		return (-1);
	buffer->end -= bytes;
	return (0);
}

void
buffer_consume_end(Buffer *buffer, u_int bytes)
{
	if (buffer_consume_end_ret(buffer, bytes) == -1)
		fatal("buffer_consume_end: trying to get more bytes than in buffer");
}

#endif