HEX Viewer

Page last updated 09 Dec 2009, by Rolf Meyer. 1 reply debug, hexview, stdout

The hexview.h is a simple file to add to your project to print out a hexview of a memory region with a given length. I've used it to debug Ethernet stuff and the lwip classes. It was very helpful, so I've decided to share it and make a more advanced version.

On the right you can see the demo application. You can find it on the bottom.

I'm pretty sure it is not only useful for Ethernet ;-)

/* Function: hexview
 *  Prints an array of char to stdout in hex.
 *  The data is grouped in two 8 byte groups per line.
 *  Each byte is displayed as 2 hex digits and every 
 *  line starts with the address of the first byte.
 *
 *  There is no text view of a line.
 *
 * Variables:
 *  buffer - The array to display.
 *  size - The length of buffer.
 * 
 * Author: rmeyer
 */
inline void hexview(const char *buffer, unsigned int size) {
    printf("\n");
    for(int i = 0; i < size; ++i) {
        if((i%16)!=0) {
            printf(" ");
        } else {
            printf("%04X:  ", (i));
        }
        printf("%02hhx", buffer[i]);
        if((i%16) ==  7) { 
            printf(" ");
        }
        if((i%16) == 15) {
            printf("\n");
        }
    }
    printf("\n\n\n");
}

An improved version which uses more RAM but less often printf. It prints the char representation of the data as well:

/* Function: hexview
 *  Prints an array of char to stdout in hex.
 *  The data is grouped in two 8 byte groups per line.
 *  Each byte is displayed as 2 hex digits and every 
 *  line starts with the address of the first byte.
 *  Each line ends ub with an ASCII representation 
 *  of the bytes.
 *
 *  This implementation takes more stack space than the other.
 *  It will allocate two char arrays with a agregated size of 70 bytes.
 *  Therefore its faster than the fierst implementation. 
 *  It operates directly on the char arrays and make no use of 
 *  string manipulation functions. printf is called one time a line.
 *
 * Variables:
 *  buffer - The array to display.
 *  size - The length of buffer.
 */
 inline void hexview(const char *buffer, unsigned int size) {
    char byte[50];
    char text[20];
    bool big = false;
    int i;
    for(i = 0; i < size; ++i) {
        if((i&0xF) == 0x0) {
            if(big)
                printf("%04X: %-49s: %-20s\n", (i&~0xF), byte, text);
            big = false;
            byte[0] = '\0';
            text[0] = '\0';
        } else if((i&0xF) == 0x8) {
            big = true;
            byte[(i&0xF) * 3] = ' ';
            text[(i&0xF)] = ' ';
        }
        unsigned char value = buffer[i];
        text[(i&0xF) + 0 + big] = (value < 0x20 || value > 0x7F)? '.': value;
        text[(i&0xF) + 1 + big] = '\0';
        value = (buffer[i] &0xF0) >> 4;
        byte[(i&0xF) * 3 + 0 + big] = (value < 0xA)? (value + 0x30): (value + 0x37);
        value = (buffer[i] &0x0F);
        byte[(i&0xF) * 3 + 1 + big] = (value < 0xA)? (value + 0x30): (value + 0x37);
        byte[(i&0xF) * 3 + 2 + big] = ' ';
        byte[(i&0xF) * 3 + 3 + big] = '\0';
    }
    if(byte[0]) {
        printf("%04X: %-49s: %-20s\n", (i&~0xF), byte, text);
    }
    printf("\n");
}

A demo how to use it with the Ethernet class is here: ethersniff_hex

1 comment

Andrew Harpin

# 02 Dec 2009

Useful keeps the bandwidth requirements down :)

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