way to convert char array to a hex string and print it in one line

Question

Here is a char array

char temp[] ={0x1f,0x2d,0x3c};

i want use the __android_log_print to print the temp ,how can convert it to "1f2d3c" and print it in one line without a for loop?

What i expected

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Reality

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You say that you want to print the characters, but your example is printing the hex value of the characters. — Wolph, Jan 05 '15 at 02:31
possible duplicate of [How do you convert buffer (byte array) to hex string in C?](http://stackoverflow.com/questions/6357031/how-do-you-convert-buffer-byte-array-to-hex-string-in-c) — Jonathon Reinhart, Jan 05 '15 at 03:44
Note that the word "hex" I added to your title is *crucial* for this question to be interpreted correctly! — Jonathon Reinhart, Jan 05 '15 at 03:45

score 0 · Answer 1 · edited Jan 05 '15 at 02:35

0

If the array is always of size 3, then:

__android_log_print(<whatever level>,"%02x%02x%02x", temp[0],temp[1],temp[2]);

edited Jan 05 '15 at 02:35

Meninx - メネンックス

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answered Jan 05 '15 at 02:32

OldProgrammer

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1

any other ways? what if the temp size is 128,that's crazy – log1000 Jan 05 '15 at 02:38
No, what is wrong with a loop then? You did not specify how big the array was. – OldProgrammer Jan 05 '15 at 02:39
the __android_log_print will add some addtional info and each loop it will create a newline – log1000 Jan 05 '15 at 02:41
so your main problem is `\n` not the `for` loop ! – Meninx - メネンックス Jan 05 '15 at 02:47
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So loop sprintf and append to a buffer, then print that with %s for the entire string. – OldProgrammer Jan 05 '15 at 02:51

score 0 · Accepted Answer · answered Jan 05 '15 at 03:03

0

Substitute your log function for printf in the printHex function. You may be able to get away with not passing the length of the array as long as it is 0 terminated and there are no 0 bytes in the middle of it so you could use strlen to find the length.

#include <stdio.h>
#include <string.h>

void printHex(char* digits, int len)
{
    int i;
    char* str;

    str = malloc(len * 2 + 1);
    memset(str, 0, len * 2 + 1);
    for(i = 0; i < len; ++i)
    {
        char temp[3];
        sprintf(temp, "%02x", digits[i]);
        strcat(str, temp);
    }
    printf("%s\n", str);
    free(str);
}

int main(void) 
{
    char temp[] ={0x1f,0x2d,0x3c,4,0,5,0,6,7,8};
    printHex(temp, sizeof(temp));
    return 0;
}

answered Jan 05 '15 at 03:03

Retired Ninja

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Given the example values in his array, I would interpret it as raw binary data, in which 0-values may appears, and `strlen()` would be inappropriate. – Jonathon Reinhart Jan 05 '15 at 03:47
Also, an optimization: You could `sprintf(&str[2*i], ...` directly. This avoids the `strcat` every iteration, which is expensive, as it must scan of the end of the string *every time*. You could also leave out the `memset` then. – Jonathon Reinhart Jan 05 '15 at 03:49

way to convert char array to a hex string and print it in one line

2 Answers2