path: root/lib/ofpbuf.c

/*
 * Copyright (c) 2008, 2009 Nicira Networks.
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include <config.h>
#include "ofpbuf.h"
#include <assert.h>
#include <stdlib.h>
#include <string.h>
#include "util.h"

/* Initializes 'b' as an empty ofpbuf that contains the 'allocated' bytes of
 * memory starting at 'base'.
 *
 * 'base' should ordinarily be the first byte of a region obtained from
 * malloc(), but in circumstances where it can be guaranteed that 'b' will
 * never need to be expanded or freed, it can be a pointer into arbitrary
 * memory. */
void
ofpbuf_use(struct ofpbuf *b, void *base, size_t allocated)
{
    b->base = b->data = base;
    b->allocated = allocated;
    b->size = 0;
    b->l2 = b->l3 = b->l4 = b->l7 = NULL;
    b->next = NULL;
    b->private = NULL;
}

/* Initializes 'b' as an empty ofpbuf with an initial capacity of 'size'
 * bytes. */
void
ofpbuf_init(struct ofpbuf *b, size_t size)
{
    ofpbuf_use(b, size ? xmalloc(size) : NULL, size);
}

/* Frees memory that 'b' points to. */
void
ofpbuf_uninit(struct ofpbuf *b) 
{
    if (b) {
        free(b->base);
    }
}

/* Frees memory that 'b' points to and allocates a new ofpbuf */
void
ofpbuf_reinit(struct ofpbuf *b, size_t size)
{
    ofpbuf_uninit(b);
    ofpbuf_init(b, size);
}

/* Creates and returns a new ofpbuf with an initial capacity of 'size'
 * bytes. */
struct ofpbuf *
ofpbuf_new(size_t size)
{
    struct ofpbuf *b = xmalloc(sizeof *b);
    ofpbuf_init(b, size);
    return b;
}

struct ofpbuf *
ofpbuf_clone(const struct ofpbuf *buffer)
{
    return ofpbuf_clone_data(buffer->data, buffer->size);
}

struct ofpbuf *
ofpbuf_clone_data(const void *data, size_t size)
{
    struct ofpbuf *b = ofpbuf_new(size);
    ofpbuf_put(b, data, size);
    return b;
}

/* Frees memory that 'b' points to, as well as 'b' itself. */
void
ofpbuf_delete(struct ofpbuf *b) 
{
    if (b) {
        ofpbuf_uninit(b);
        free(b);
    }
}

/* Returns the number of bytes of headroom in 'b', that is, the number of bytes
 * of unused space in ofpbuf 'b' before the data that is in use.  (Most
 * commonly, the data in a ofpbuf is at its beginning, and thus the ofpbuf's
 * headroom is 0.) */
size_t
ofpbuf_headroom(struct ofpbuf *b) 
{
    return (char*)b->data - (char*)b->base;
}

/* Returns the number of bytes that may be appended to the tail end of ofpbuf
 * 'b' before the ofpbuf must be reallocated. */
size_t
ofpbuf_tailroom(struct ofpbuf *b) 
{
    return (char*)ofpbuf_end(b) - (char*)ofpbuf_tail(b);
}

/* Ensures that 'b' has room for at least 'size' bytes at its tail end,
 * reallocating and copying its data if necessary. */
void
ofpbuf_prealloc_tailroom(struct ofpbuf *b, size_t size) 
{
    if (size > ofpbuf_tailroom(b)) {
        size_t new_allocated = b->allocated + MAX(size, 64);
        void *new_base = xmalloc(new_allocated);
        uintptr_t base_delta = (char*)new_base - (char*)b->base;
        memcpy(new_base, b->base, b->allocated);
        free(b->base);
        b->base = new_base;
        b->allocated = new_allocated;
        b->data = (char*)b->data + base_delta;
        if (b->l2) {
            b->l2 = (char*)b->l2 + base_delta;
        }
        if (b->l3) {
            b->l3 = (char*)b->l3 + base_delta;
        }
        if (b->l4) {
            b->l4 = (char*)b->l4 + base_delta;
        }
        if (b->l7) {
            b->l7 = (char*)b->l7 + base_delta;
        }
    }
}

void
ofpbuf_prealloc_headroom(struct ofpbuf *b, size_t size) 
{
    assert(size <= ofpbuf_headroom(b));
}

/* Trims the size of 'b' to fit its actual content. */
void
ofpbuf_trim(struct ofpbuf *b)
{
    /* XXX These could be supported, but the current client doesn't care. */
    assert(b->data == b->base);
    assert(b->l2 == NULL && b->l3 == NULL && b->l4 == NULL && b->l7 == NULL);
    if (b->allocated > b->size) {
        b->base = b->data = xrealloc(b->base, b->size);
        b->allocated = b->size;
    }
}

/* Appends 'size' bytes of data to the tail end of 'b', reallocating and
 * copying its data if necessary.  Returns a pointer to the first byte of the
 * new data, which is left uninitialized. */
void *
ofpbuf_put_uninit(struct ofpbuf *b, size_t size) 
{
    void *p;
    ofpbuf_prealloc_tailroom(b, size);
    p = ofpbuf_tail(b);
    b->size += size;
    return p;
}

/* Appends 'size' zeroed bytes to the tail end of 'b'.  Data in 'b' is
 * reallocated and copied if necessary.  Returns a pointer to the first byte of
 * the data's location in the ofpbuf. */
void *
ofpbuf_put_zeros(struct ofpbuf *b, size_t size)
{
    void *dst = ofpbuf_put_uninit(b, size);
    memset(dst, 0, size);
    return dst;
}

/* Appends the 'size' bytes of data in 'p' to the tail end of 'b'.  Data in 'b'
 * is reallocated and copied if necessary.  Returns a pointer to the first
 * byte of the data's location in the ofpbuf. */
void *
ofpbuf_put(struct ofpbuf *b, const void *p, size_t size) 
{
    void *dst = ofpbuf_put_uninit(b, size);
    memcpy(dst, p, size);
    return dst;
}

/* Reserves 'size' bytes of headroom so that they can be later allocated with
 * ofpbuf_push_uninit() without reallocating the ofpbuf. */
void
ofpbuf_reserve(struct ofpbuf *b, size_t size) 
{
    assert(!b->size);
    ofpbuf_prealloc_tailroom(b, size);
    b->data = (char*)b->data + size;
}

void *
ofpbuf_push_uninit(struct ofpbuf *b, size_t size) 
{
    ofpbuf_prealloc_headroom(b, size);
    b->data = (char*)b->data - size;
    b->size += size;
    return b->data;
}

void *
ofpbuf_push(struct ofpbuf *b, const void *p, size_t size) 
{
    void *dst = ofpbuf_push_uninit(b, size);
    memcpy(dst, p, size);
    return dst;
}

/* If 'b' contains at least 'offset + size' bytes of data, returns a pointer to
 * byte 'offset'.  Otherwise, returns a null pointer. */
void *
ofpbuf_at(const struct ofpbuf *b, size_t offset, size_t size) 
{
    return offset + size <= b->size ? (char *) b->data + offset : NULL;
}

/* Returns a pointer to byte 'offset' in 'b', which must contain at least
 * 'offset + size' bytes of data. */
void *
ofpbuf_at_assert(const struct ofpbuf *b, size_t offset, size_t size) 
{
    assert(offset + size <= b->size);
    return ((char *) b->data) + offset;
}

/* Returns the byte following the last byte of data in use in 'b'. */
void *
ofpbuf_tail(const struct ofpbuf *b) 
{
    return (char *) b->data + b->size;
}

/* Returns the byte following the last byte allocated for use (but not
 * necessarily in use) by 'b'. */
void *
ofpbuf_end(const struct ofpbuf *b) 
{
    return (char *) b->base + b->allocated;
}

/* Clears any data from 'b'. */
void
ofpbuf_clear(struct ofpbuf *b) 
{
    b->data = b->base;
    b->size = 0;
}

/* Removes 'size' bytes from the head end of 'b', which must contain at least
 * 'size' bytes of data.  Returns the first byte of data removed. */
void *
ofpbuf_pull(struct ofpbuf *b, size_t size) 
{
    void *data = b->data;
    assert(b->size >= size);
    b->data = (char*)b->data + size;
    b->size -= size;
    return data;
}

/* If 'b' has at least 'size' bytes of data, removes that many bytes from the
 * head end of 'b' and returns the first byte removed.  Otherwise, returns a
 * null pointer without modifying 'b'. */
void *
ofpbuf_try_pull(struct ofpbuf *b, size_t size) 
{
    return b->size >= size ? ofpbuf_pull(b, size) : NULL;
}