/*------------------------------------------------------------------
 * getenv_s.c
 *
 * September 2017, Reini Urban
 * January 2022, Reini Urban
 * October 2022, Reini Urban
 *
 * Copyright (c) 2017,2022 by Reini Urban
 * All rights reserved.
 *
 * Permission is hereby granted, free of charge, to any person
 * obtaining a copy of this software and associated documentation
 * files (the "Software"), to deal in the Software without
 * restriction, including without limitation the rights to use,
 * copy, modify, merge, publish, distribute, sublicense, and/or
 * sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following
 * conditions:
 *
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
 * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT.  IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 *------------------------------------------------------------------
 */

#ifdef FOR_DOXYGEN
#include "safe_lib.h"
#else
#include "safeclib_private.h"
#endif

/**
 * @def getenv_s(len,dest,dmax,name)
 * @brief
 *    The \c getenv_s function searches for an environmental variable with
 *    name name in the host-specified environment list and returns a pointer
 *    to the string that is associated with the matched environment
 *    variable. The set of environmental variables and methods of altering it
 *    are implementation-defined.  The value of the environment variable is
 *    written to the user-provided buffer value (unless null) and the number
 *    of bytes written is stored in the user-provided location *len (unless
 *    null).
 *    If the environment variable is not set in the environment, zero
 *    is written to *len (unless null) and '\0' is written to value[0] (unless
 *    null).
 *    With SAFECLIB_STR_NULL_SLACK defined all elements following the
 *    terminating NUL character (if any) written in the
 *    array of dmax characters pointed to by dest are nulled.
 *    If \c secure_getenv() is available, it is used.
 *
 * @remark SPECIFIED IN
 *    * C11 standard (ISO/IEC 9899:2011):
 *    K.3.6.2.1 The getenv_s function (p: 607-607)
 *    http://en.cppreference.com/w/c/program/getenv
 *
 * @param[out] len    pointer to a size_t where getenv_s will store the length
 *                    of the found environment variable. Might be NULL.
 *                    Note that on Microsoft Windows we return len+1, the
 *                    size of the buffer, including the terminating NUL, to match
 *                    the wrong getenv_s implementation und usages in the wild there.
 * @param[out] dest   pointer to a string where getenv_s will store the
 *                    contents of the found environment variable. Might be NULL.
 * @param[in]  dmax   maximum number of characters that getenv_s is allowed
 *                    to write to dest (size of the buffer). Might be 0.
 * @param[in]  name   null-terminated character string identifying the name of
 *                    the environmental variable to look for.
 *
 * @pre name shall not be a null pointer.
 * @pre dmax shall not be greater than RSIZE_MAX_STR and size of dest.
 * @pre dmax shall be 0 if dest is NULL or greater than the strlen of the returned env value.
 *
 * @return zero if the environment variable was found, non-zero if it was not
 *         found of if a runtime constrant violation occurred. On any error,
 *         writes zero to *len, unless len is a null pointer.
 *
 * @retval  EOK        on success
 * @retval  ESNULLP    when name is a NULL pointer
 * @retval  ESLEMAX    when dmax > RSIZE_MAX_STR
 * @retval  EOVERFLOW  when dmax > size of dest (optionally, when the compiler
 *                     knows the object_size statically)
 * @retval  ESLEWRNG   when dmax != sizeof(dest) and --enable-error-dmax
 * @retval  ESNOSPC    when dmax is too small for the value
 * @retval  -1         when not found
 */

#ifdef FOR_DOXYGEN
errno_t getenv_s(size_t *restrict len, char *restrict dest,
                     rsize_t dmax, const char *restrict name)
#else
EXPORT errno_t _getenv_s_chk(size_t *restrict len, char *restrict dest,
                             rsize_t dmax, const char *restrict name,
                             const size_t destbos)
#endif
{
    const char *buf;
    size_t len1;

    if (likely(dest)) {
        if (destbos == BOS_UNKNOWN) {
            if (unlikely(dmax > RSIZE_MAX_STR)) {
                goto err_dmax;
            }
            BND_CHK_PTR_BOUNDS(dest, dmax);
        } else {
            if (unlikely(dmax > destbos)) {
            err_dmax:
                if (len)
                    *len = 0;
                invoke_safe_str_constraint_handler("getenv_s: dmax exceeds max",
                                                   (void *)dest, ESLEMAX);
                return RCNEGATE(ESLEMAX);
            }
        }
    }
    else {
        if (dmax != 0) { // with dest == NULL
            if (len)
                *len = 0;
            invoke_safe_str_constraint_handler("getenv_s: dmax must be 0",
                                               NULL, ESNULLP);
            return ESNULLP;
        }
    }
    if (unlikely(name == NULL)) {
        if (len)
            *len = 0;
        if (likely(dest)) {
            handle_error(dest, dmax, "getenv_s: name is null", ESNULLP);
        }
        else {
            invoke_safe_str_constraint_handler("getenv_s: name is null",
                                               NULL, ESNULLP);
        }
        return ESNULLP;
    }

    errno = 0;
#ifdef HAVE_SECURE_GETENV
    buf = secure_getenv(name);
#else
    buf = getenv(name);
#endif

    if (buf == NULL) {
        if (likely(dest)) {
#ifdef SAFECLIB_STR_NULL_SLACK
            memset(dest, 0, dmax);
#else
            *dest = '\0';
#endif
        }
        if (len)
            *len = 0;
        return -1;
    }

    len1 = strlen(buf);
    if (unlikely(dmax != 0 && len1 >= dmax)) {
        if (len)
            *len = 0;
        handle_error(dest, dmax, "getenv_s: dmax is too small", ESNOSPC);
        return RCNEGATE(ESNOSPC);
    } else {
        if (len)
#ifdef _WIN32
            *len = len1 + 1;
#else
            *len = len1;
#endif
        if (dest)
            strcpy_s(dest, dmax, buf);
    }

    return EOK;
}
