hexlify and unhexlify functions in C - c

Question

Please help... I'm trying to learn C types conversion.
This code works well only converting some hex chars as 1, 2, 3. For others, also changing string or reduce string length, the conversion fails...
I'll put the code below... Anyone can explain me where the code is wrong?
Thanks in advance!
#include <stdio.h>
int a2v(char c)
{
if ((c >= '0') && (c <= '9'))
{
return c - '0';
}
if ((c >= 'a') && (c <= 'f'))
{
return c - 'a' + 10;
}
else return 0;
}
char v2a(int c)
{
const char hex[] = "0123456789abcdef";
return hex[c];
}
char *unhexlify(char *hstr)
{
char *bstr = malloc((strlen(hstr) / 2) + 1);
char *pbstr = bstr;
for (int i = 0; i < strlen(hstr); i += 2)
{
*pbstr++ = (a2v(hstr[i]) << 4) + a2v(hstr[i + 1]);
}
*pbstr++ = '\0';
return bstr;
}
char *hexlify(char *bstr)
{
char *hstr = malloc((strlen(bstr) * 2) + 1);
char *phstr = hstr;
for (int i = 0; i < strlen(bstr); i++)
{
*phstr++ = v2a((bstr[i] >> 4) & 0xFF);
*phstr++ = v2a((bstr[i]) & 0xFF);
}
*phstr++ = '\0';
return hstr;
}
int main()
{
char *title = "... Trying to convert hex into binary string and back again ?! ...";
printf("%s\n\n", title);
char *input = "0123456789abcdef\0";
printf("Original: %s (%d)\n\n", input, (int)strlen(input));
char *input_bin = unhexlify(input);
printf("Bin: %s (%d)\n\n", input_bin, (int)strlen(input_bin));
char *input_hex = hexlify(input_bin);
printf("Hex: %s (%d)\n\n", input_hex, (int)strlen(input_hex));
system("pause");
return 0;
}

Answer 1

Updated Version of #Kevin's answer:
int a2v(char c) {
if ((c >= '0') && (c <= '9')) return c - '0';
if ((c >= 'a') && (c <= 'f')) return c - 'a' + 10;
if ((c >= 'A') && (c <= 'F')) return c - 'A' + 10;
else return 0;
}
char v2a(int c) {
const char hex[] = "0123456789abcdef";
return hex[c];
}
char *hexlify(char *bstr) {
char *hstr=malloc((strlen(bstr)*2)+1);
bzero(hstr,(strlen(bstr)*2)+1);
char *phstr=hstr;
for(int i=0; i<strlen(bstr);i++) {
*phstr++ =v2a((bstr[i]>>4)&0x0F);
*phstr++ =v2a((bstr[i])&0x0F);
}
*phstr++ ='\0';
return hstr;
}
char *hexlifyn(char *bstr, uint str_len) {
char *hstr=malloc((str_len*2)+1);
bzero(hstr,(str_len*2)+1);
char *phstr=hstr;
for(int i=0; i<str_len;i++) {
*phstr++ =v2a((bstr[i]>>4)&0x0F);
*phstr++ =v2a((bstr[i])&0x0F);
}
*phstr++ ='\0';
return hstr;
}
char *unhexlify(char *hstr) {
char *bstr=malloc((strlen(hstr)/2)+1);
bzero(bstr,(strlen(hstr)/2)+1);
char *pbstr=bstr;
for(int i=0;i<strlen(hstr); i += 2)
*pbstr++ =(a2v(hstr[i])<<4)+a2v(hstr[i+1]);
*pbstr++ ='\0';
return bstr;
}
char *unhexlifyn(char *hstr, uint str_len) {
char *bstr=malloc((str_len/2)+1);
bzero(bstr,(str_len/2)+1);
char *pbstr=bstr;
for(int i=0;i<str_len; i += 2)
*pbstr++ =(a2v(hstr[i])<<4)+a2v(hstr[i+1]);
*pbstr++ ='\0';
return bstr;
}

Answer 2

Thank you!
Based on chux's answer, the mistake was into hexlify function:
*phstr++ = v2a((bstr[i] >> 4) & 0x0F);
*phstr++ = v2a((bstr[i]) & 0x0F);
Masks was wrong! I will study much more!
PS = I added some code in order to handle NULL binary character (0), that truncates string.
#include <stdio.h>
int a2v(char c)
{
if ((c >= '0') && (c <= '9'))
{
return c - '0';
}
if ((c >= 'a') && (c <= 'f'))
{
return c - 'a' + 10;
}
else return 0;
}
char v2a(int c)
{
const char hex[] = "0123456789abcdef";
return hex[c];
}
char *unhexlify(char *hstr)
{
char *bstr = malloc((strlen(hstr) / 2) + 1);
char *pbstr = bstr;
for (int i = 0; i < strlen(hstr); i += 2)
{
char c = (a2v(hstr[i]) << 4) + a2v(hstr[i + 1]);
if (c == 0) {
*pbstr++ = -128;
} else {
*pbstr++ = c;
}
}
*pbstr++ = '\0';
return bstr;
}
char *hexlify(char *bstr)
{
char *hstr = malloc((strlen(bstr) * 2) + 1);
char *phstr = hstr;
for (int i = 0; i < strlen(bstr); i++)
{
if (bstr[i] == -128)
{
*phstr++ = '0';
*phstr++ = '0';
} else {
*phstr++ = v2a((bstr[i] >> 4) & 0x0F);
*phstr++ = v2a((bstr[i]) & 0x0F);
}
}
*phstr++ = '\0';
return hstr;
}
int main()
{
printf("... Trying to convert hex into binary string and back again ?! ...\n\n");
char *input = "070790ca8fd8058b455f13dd698a4eed028cb0efc13907f681604676d69e57affe299aae7c91fd000000005271266004e4cd7f52548153f8f78b76840aeca16e91bac0ebeb4d74ff3ce3c901\0";
char *input_bin = unhexlify(input);
char *input_hex = hexlify(input_bin);
printf("Input: %s (%d)\n\n", input, strlen(input));
printf("Output: %s (%d)\n\n", input_hex, strlen(input_hex));
if (strcmp(input, input_hex) == 0)
{
printf("Input and output are EQUALS !\n\n");
} else {
printf("Input and output are NOT EQUALS !\n\n");
}
system("pause");
return 0;
}
Regards, Kevin