/*  SPDX-License-Identifier: MIT */
/*
 *  Copyright (c) 2008 Bo Berry
 *  Copyright (c) 2008-2011 Cisco Systems
 */

#include "safeclib_private.h"
#include "safe_mem_constraint.h"
#include "mem_primitives_lib.h"
#include "safe_mem_lib.h"

/**
 * NAME
 *    memcpy_s
 *
 * SYNOPSIS
 *    #include "safe_mem_lib.h"
 *    errno_t
 *    memcpy_s(void *dest, rsize_t dmax, const void *src, rsize_t smax)
 *
 * DESCRIPTION
 *    This function copies at most smax bytes from src to dest, up to
 *    dmax. The size values are unsigned values.
 *
 *    AR: Dave - verify ISO spec requires unsigned
 *
 * SPECIFIED IN
 *    ISO/IEC JTC1 SC22 WG14 N1172, Programming languages, environments
 *    and system software interfaces, Extensions to the C Library,
 *    Part I: Bounds-checking interfaces
 *
 * INPUT PARAMETERS
 *    dest      pointer to memory that will be replaced by src.
 *
 *    dmax      maximum length of the resulting dest
 *
 *    src       pointer to the memory that will be copied to dest
 *
 *    smax      maximum number bytes of src to copy
 *
 *  OUTPUT PARAMETERS
 *    dest      is updated
 *
 * RUNTIME CONSTRAINTS
 *    Neither dest nor src shall be a null pointer.
 *    Neither dmax nor smax shall be zero.
 *    dmax shall not be greater than RSIZE_MAX_MEM.
 *    smax shall not be greater than dmax.
 *    Copying shall not take place between regions that overlap.
 *    If there is a runtime-constraint violation, the memcpy_s function
 *    stores zeros in the first dmax bytes of the region pointed to
 *    by dest if dest is not a null pointer and smax is valid.
 *
 * RETURN VALUE
 *    EOK        successful operation
 *    ESNULLP    NULL pointer
 *    ESZEROL    zero length
 *    ESLEMAX    length exceeds max limit
 *    ESOVRLP    source memory overlaps destination
 *
 * ALSO SEE
 *    memcpy16_s(), memcpy32_s(), memmove_s(), memmove16_s(),
 *     memmove32_s()
 *
 */
errno_t
memcpy_s (void *dest, rsize_t dmax, const void *src, rsize_t smax)
{
    uint8_t *dp;
    const uint8_t  *sp;

    dp = dest;
    sp = src;

    if (dp == NULL) {
        invoke_safe_mem_constraint_handler("memcpy_s: dest is NULL",
                   NULL, ESNULLP);
        return RCNEGATE(ESNULLP);
    }

    if (dmax == 0) {
        invoke_safe_mem_constraint_handler("memcpy_s: dmax is 0",
                   NULL, ESZEROL);
        return RCNEGATE(ESZEROL);
    }

    if (dmax > RSIZE_MAX_MEM) {
        invoke_safe_mem_constraint_handler("memcpy_s: dmax exceeds max",
                   NULL, ESLEMAX);
        return RCNEGATE(ESLEMAX);
    }

    // AR: This is not a requirement according to the ISO spec - Change?
    // AR: documentation needed on use of the error handlers -
    // AR: default err handler should output to stderr on DEBUG
    // AR: update docs to define return RCNEGATE of the error number
    if (smax == 0) {
        mem_prim_set(dp, dmax, 0);
        invoke_safe_mem_constraint_handler("memcpy_s: smax is 0",
                   NULL, ESZEROL);
        return RCNEGATE(ESZEROL);
    }

    if (smax > dmax) {
        mem_prim_set(dp, dmax, 0);
        invoke_safe_mem_constraint_handler("memcpy_s: smax exceeds dmax",
                   NULL, ESLEMAX);
        return RCNEGATE(ESLEMAX);
    }

    if (sp == NULL) {
        mem_prim_set(dp, dmax, 0);
        invoke_safe_mem_constraint_handler("memcpy_s: src is NULL",
                   NULL, ESNULLP);
        return RCNEGATE(ESNULLP);
    }


    /*
     * overlap is undefined behavior, do not allow
     */
    if( ((dp > sp) && (dp < (sp+smax))) ||
        ((sp > dp) && (sp < (dp+dmax))) ) {
        mem_prim_set(dp, dmax, 0);
        invoke_safe_mem_constraint_handler("memcpy_s: overlap undefined",
                   NULL, ESOVRLP);
        return RCNEGATE(ESOVRLP);
    }

    /*
     * now perform the copy
     */
    mem_prim_move(dp, sp, smax);

    return RCNEGATE(EOK);
}
EXPORT_SYMBOL(memcpy_s)
