/* SPDX-License-Identifier: LGPL-3.0-or-later */
/* Copyright (C) 2014 OSCAR lab, Stony Brook University
 * 2017 University of North Carolina at Chapel Hill
 */

#ifndef HEX_H
#define HEX_H

#include <stddef.h>
#include <stdint.h>

#include "api.h"
#include "assert.h"

/* This function is a helper for debug printing.
 * It accepts a pointer to a numerical value, and
 * formats it as a hex string, for printing.
 * size is the number of bytes pointed to by hex.
 * str is the caller-provided buffer, len is the length of the buffer.
 * The len must be at least (size * 2)+1.
 */
static inline char* __bytes2hexstr(void* hex, size_t size, char* str, size_t len) {
    static const char* ch = "0123456789abcdef";
    __UNUSED(len);
    assert(len >= size * 2 + 1);

    for (size_t i = 0; i < size; i++) {
        unsigned char h = ((unsigned char*)hex)[i];
        str[i * 2]     = ch[h / 16];
        str[i * 2 + 1] = ch[h % 16];
    }

    str[size * 2] = 0;
    return str;
}

#define IS_CHAR_ARRAY(arg) (_Generic((arg), char*: 1, default: 0) && \
                            _Generic(&(arg), char**: 0, default: 1))
#define IS_UINT8_ARRAY(arg) (_Generic((arg), uint8_t*: 1, default: 0) && \
                             _Generic(&(arg), uint8_t**: 0, default: 1))

static inline int8_t hex2dec(char c) {
    if (c >= 'A' && c <= 'F')
        return c - 'A' + 10;
    else if (c >= 'a' && c <= 'f')
        return c - 'a' + 10;
    else if (c >= '0' && c <= '9')
        return c - '0';
    else
        return -1;
}

/*
 * BYTES2HEXSTR converts an array into a hexadecimal string and fills into a
 * given buffer. The buffer size is given as an extra argument.
 */
#define BYTES2HEXSTR(array, str, len) ({                         \
    static_assert(IS_CHAR_ARRAY(array) || IS_UINT8_ARRAY(array), \
                  "`array` must be a char or uint8_t array");    \
    __bytes2hexstr((array), sizeof(array), str, len);})

/*
 * ALLOCA_BYTES2HEXSTR uses __alloca to allocate a buffer on the current frame
 * and then fills the hexadecimal string into the buffer.
 * This buffer can only be used within the caller frame (function).
 */
#define ALLOCA_BYTES2HEXSTR(array) \
    (BYTES2HEXSTR(array, __alloca(sizeof(array) * 2 + 1), sizeof(array) * 2 + 1))

#endif // HEX_H