23.8.7.34 mysql_hex_string()

unsigned long mysql_hex_string(char *to, const char *from, unsigned long length)

Description

This function is used to create a legal SQL string that you can use in an SQL statement. See Section 9.1.1, “String Literals”.

The string in from is encoded to hexadecimal format, with each character encoded as two hexadecimal digits. The result is placed in to and a terminating null byte is appended.

The string pointed to by from must be length bytes long. You must allocate the to buffer to be at least length*2+1 bytes long. When mysql_hex_string() returns, the contents of to is a null-terminated string. The return value is the length of the encoded string, not including the terminating null character.

The return value can be placed into an SQL statement using either 0xvalue or X'value' format. However, the return value does not include the 0x or X'...'. The caller must supply whichever of those is desired.

Example
char query[1000],*end;

end = strmov(query,"INSERT INTO test_table values(");
end = strmov(end,"0x");
end += mysql_hex_string(end,"What is this",12);
end = strmov(end,",0x");
end += mysql_hex_string(end,"binary data: \0\r\n",16);
*end++ = ')';

if (mysql_real_query(&mysql,query,(unsigned int) (end - query)))
{
   fprintf(stderr, "Failed to insert row, Error: %s\n",
           mysql_error(&mysql));
}

The strmov() function used in the example is included in the libmysqlclient library and works like strcpy() but returns a pointer to the terminating null of the first parameter.

Return Values

The length of the value placed into to, not including the terminating null character.

Errors

None.