source: mainline/uspace/app/bithenge/transform.h@ 04a7435f

/*
 * Copyright (c) 2012 Sean Bartell
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/** @addtogroup bithenge
 * @{
 */
/**
 * @file
 * Transforms.
 */

#ifndef BITHENGE_TRANSFORM_H_
#define BITHENGE_TRANSFORM_H_

#include "blob.h"
#include "tree.h"

/** A transform that creates a new tree from an old tree. */
typedef struct {
        /** @privatesection */
        const struct bithenge_transform_ops *ops;
        unsigned int refs;
} bithenge_transform_t;

/** Operations that may be provided by a transform. */
typedef struct bithenge_transform_ops {
        /** @copydoc bithenge_transform_t::bithenge_transform_apply */
        int (*apply)(bithenge_transform_t *xform, bithenge_node_t *in, bithenge_node_t **out);
        /** @copydoc bithenge_transform_t::bithenge_transform_prefix_length */
        int (*prefix_length)(bithenge_transform_t *xform, bithenge_blob_t *blob, aoff64_t *out);
        /** Destroy the transform.
         * @param xform The transform.
         * @return EOK on success or an error code from errno.h. */
        int (*destroy)(bithenge_transform_t *xform);
} bithenge_transform_ops_t;

/** Apply a transform.
 * @memberof bithenge_transform_t
 * @param xform The transform.
 * @param in The input tree.
 * @param[out] out Where the output tree will be stored.
 * @return EOK on success or an error code from errno.h. */
static inline int bithenge_transform_apply(bithenge_transform_t *xform,
    bithenge_node_t *in, bithenge_node_t **out)
{
        assert(xform);
        assert(xform->ops);
        return xform->ops->apply(xform, in, out);
}

/** Find the length of the prefix of a blob this transform can use as input. In
 * other words, figure out how many bytes this transform will use up.  This
 * method is optional and can return an error, but it must succeed for struct
 * subtransforms.
 * @memberof bithenge_transform_t
 * @param xform The transform.
 * @param blob The blob.
 * @param[out] out Where the prefix length will be stored.
 * @return EOK on success, ENOTSUP if not supported, or another error code from
 * errno.h. */
static inline int bithenge_transform_prefix_length(bithenge_transform_t *xform,
    bithenge_blob_t *blob, aoff64_t *out)
{
        assert(xform);
        assert(xform->ops);
        if (!xform->ops->prefix_length)
                return ENOTSUP;
        return xform->ops->prefix_length(xform, blob, out);
}

/** Increment a transform's reference count.
 * @param xform The transform to reference.
 * @return EOK on success or an error code from errno.h. */
static inline int bithenge_transform_inc_ref(bithenge_transform_t *xform)
{
        assert(xform);
        xform->refs++;
        return EOK;
}

/** Decrement a transform's reference count and free it if appropriate.
 * @param xform The transform to dereference, or NULL.
 * @return EOK on success or an error code from errno.h. */
static inline int bithenge_transform_dec_ref(bithenge_transform_t *xform)
{
        if (!xform)
                return EOK;
        assert(xform->ops);
        if (--xform->refs == 0)
                return xform->ops->destroy(xform);
        return EOK;
}

/** A transform with a name. */
typedef struct {
        const char *name;
        bithenge_transform_t *transform;
} bithenge_named_transform_t;

extern bithenge_transform_t bithenge_uint32le_transform;
extern bithenge_transform_t bithenge_uint32be_transform;
extern bithenge_named_transform_t *bithenge_primitive_transforms;

int bithenge_new_transform(bithenge_transform_t *xform,
    const bithenge_transform_ops_t *ops);

int bithenge_new_struct(bithenge_transform_t **out,
    bithenge_named_transform_t *subtransforms);

#endif

/** @}
 */