File lt_utils.c

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/* Copyright (c) Kuba Szczodrzyński 2022-04-29. */

#include "lt_utils.h"

void lt_rand_bytes(uint8_t *buf, size_t len) {
    int *data = (int *)buf;
    size_t i;
    for (i = 0; len >= sizeof(int); len -= sizeof(int)) {
        data[i++] = rand();
    }
    if (len) {
        int rem             = rand();
        unsigned char *pRem = (unsigned char *)&rem;
        memcpy(buf + i * sizeof(int), pRem, len);
    }
}

void hexdump(const uint8_t *buf, size_t len, uint32_t offset, uint8_t width) {
    uint16_t pos = 0;
    while (pos < len) {
        // print hex offset
        printf("%06lx ", offset + pos);
        // calculate current line width
        uint8_t lineWidth = MIN(width, len - pos);
        // print hexadecimal representation
        for (uint8_t i = 0; i < lineWidth; i++) {
            if (i % 8 == 0) {
                printf(" ");
            }
            printf("%02x ", buf[pos + i]);
        }
        // print ascii representation
        printf(" |");
        for (uint8_t i = 0; i < lineWidth; i++) {
            char c = buf[pos + i];
            putchar((c >= 0x20 && c <= 0x7f) ? c : '.');
        }
        puts("|\r");
        pos += lineWidth;
    }
}

char *lt_btox(const uint8_t *src, int len, char *dest) {
    // https://stackoverflow.com/a/53966346
    const char hex[] = "0123456789abcdef";
    len *= 2;
    dest[len] = '\0';
    while (--len >= 0)
        dest[len] = hex[(src[len >> 1] >> ((1 - (len & 1)) << 2)) & 0xF];
    return dest;
}

uint8_t *lt_xtob(const char *src, int len, uint8_t *dest) {
    // https://gist.github.com/vi/dd3b5569af8a26b97c8e20ae06e804cb

    // mapping of ASCII characters to hex values
    // (16-byte swapped to reduce XOR 0x10 operation)
    const uint8_t mapping[] = {
        0x00, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f, 0x00, // @ABCDEFG
        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // HIJKLMNO
        0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, // 01234567
        0x08, 0x09, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // 89:;<=>?
    };

    int j = 0;
    uint8_t idx0;
    uint8_t idx1;
    for (int i = 0; i < len; i += 2) {
        idx0      = ((uint8_t)src[i + 0] & 0x1F);
        idx1      = ((uint8_t)src[i + 1] & 0x1F);
        dest[j++] = (mapping[idx0] << 4) | (mapping[idx1] << 0);
    }
    return dest;
}