src/cx/utils.h

/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 *
 * Copyright 2021 Mike Becker, Olaf Wintermann All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *   1. Redistributions of source code must retain the above copyright
 *      notice, this list of conditions and the following disclaimer.
 *
 *   2. 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "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 COPYRIGHT HOLDER OR CONTRIBUTORS 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.
 */

/**
 * \file utils.h
 *
 * \brief General purpose utility functions.
 *
 * \author Mike Becker
 * \author Olaf Wintermann
 * \copyright 2-Clause BSD License
 */

#ifndef UCX_UTILS_H
#define UCX_UTILS_H

#include "common.h"

#ifdef __cplusplus
extern "C" {
#endif

/**
 * Convenience macro for a for loop that counts from zero to n-1.
 */
#define cx_for_n(varname, n) for (size_t varname = 0 ; (varname) < (n) ; (varname)++)

/**
 * Convenience macro for swapping two pointers.
 */
#ifdef __cplusplus
#define cx_swap_ptr(left, right) do {auto cx_tmp_swap_var = left; left = right; right = cx_tmp_swap_var;} while(0)
#else
#define cx_swap_ptr(left, right) do {void *cx_tmp_swap_var = left; left = right; right = cx_tmp_swap_var;} while(0)
#endif

// cx_szmul() definition

#if (__GNUC__ >= 5 || defined(__clang__)) && !defined(CX_NO_SZMUL_BUILTIN)
#define CX_SZMUL_BUILTIN

/**
 * Alias for \c __builtin_mul_overflow.
 *
 * Performs a multiplication of size_t values and checks for overflow.
 *
 * @param a first operand
 * @param b second operand
 * @param result a pointer to a size_t, where the result should
 * be stored
 * @return zero, if no overflow occurred and the result is correct, non-zero
 * otherwise
 */
#define cx_szmul(a, b, result) __builtin_mul_overflow(a, b, result)

#else // no GNUC or clang bultin

/**
 * Performs a multiplication of size_t values and checks for overflow.
  *
 * @param a first operand
 * @param b second operand
 * @param result a pointer to a size_t, where the result should
 * be stored
 * @return zero, if no overflow occurred and the result is correct, non-zero
 * otherwise
 */
#define cx_szmul(a, b, result) cx_szmul_impl(a, b, result)

/**
 * Performs a multiplication of size_t values and checks for overflow.
 *
 * This is a custom implementation in case there is no compiler builtin
 * available.
 *
 * @param a first operand
 * @param b second operand
 * @param result a pointer to a size_t where the result should be stored
 * @return zero, if no overflow occurred and the result is correct, non-zero
 * otherwise
 */
int cx_szmul_impl(size_t a, size_t b, size_t *result);

#endif // cx_szmul


/**
 * Reads data from a stream and writes it to another stream.
 *
 * @param src the source stream
 * @param dest the destination stream
 * @param rfnc the read function
 * @param wfnc the write function
 * @param buf a pointer to the copy buffer or \c NULL if a buffer
 * shall be implicitly created on the heap
 * @param bufsize the size of the copy buffer - if \p buf is \c NULL you can
 * set this to zero to let the implementation decide
 * @param n the maximum number of bytes that shall be copied.
 * If this is larger than \p bufsize, the content is copied over multiple
 * iterations.
 * @return the total number of bytes copied
 */
__attribute__((__nonnull__(1, 2, 3, 4)))
size_t cx_stream_bncopy(
        void *src,
        void *dest,
        cx_read_func rfnc,
        cx_write_func wfnc,
        char *buf,
        size_t bufsize,
        size_t n
);

/**
 * Reads data from a stream and writes it to another stream.
 *
 * @param src the source stream
 * @param dest the destination stream
 * @param rfnc the read function
 * @param wfnc the write function
 * @param buf a pointer to the copy buffer or \c NULL if a buffer
 * shall be implicitly created on the heap
 * @param bufsize the size of the copy buffer - if \p buf is \c NULL you can
 * set this to zero to let the implementation decide
 * @return total number of bytes copied
 */
#define cx_stream_bcopy(src, dest, rfnc, wfnc, buf, bufsize) \
    cx_stream_bncopy(src, dest, rfnc, wfnc, buf, bufsize, SIZE_MAX)

/**
 * Reads data from a stream and writes it to another stream.
 *
 * The data is temporarily stored in a stack allocated buffer.
 *
 * @param src the source stream
 * @param dest the destination stream
 * @param rfnc the read function
 * @param wfnc the write function
 * @param n the maximum number of bytes that shall be copied.
 * @return total number of bytes copied
 */
__attribute__((__nonnull__))
size_t cx_stream_ncopy(
        void *src,
        void *dest,
        cx_read_func rfnc,
        cx_write_func wfnc,
        size_t n
);

/**
 * Reads data from a stream and writes it to another stream.
 *
 * The data is temporarily stored in a stack allocated buffer.
 *
 * @param src the source stream
 * @param dest the destination stream
 * @param rfnc the read function
 * @param wfnc the write function
 * @return total number of bytes copied
 */
#define cx_stream_copy(src, dest, rfnc, wfnc) \
    cx_stream_ncopy(src, dest, rfnc, wfnc, SIZE_MAX)

#ifdef __cplusplus
}
#endif

#endif // UCX_UTILS_H