/**----------------------------------------------------------------------------\
| Concatenates any number of C strings. |
+------------------------------------------------------------------------------+
| Usage: |
| printf("%s", concat("Concatenate", " ", "me", "!", "\n")); |
| |
| Result: |
| Concatenate me! |
+-----------+-------+---------+------------------------------------------------+
| @param | char | count | Number of arguments. |
| @variadic | char* | strings | Strings to concatenate. |
| @return | char* | | Concatenated strings. |
\-----------+-------+---------+-----------------------------------------------*/
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
unsigned char* concat(unsigned char count, ...){
/* Retrieve variadic arguments. */
va_list strings;
va_start(strings, count);
/* Build concatenated string. */
unsigned char* output = calloc(1, 1);
while(count > 0){
/* Get append and output string. */
unsigned char* append = va_arg(strings, unsigned char*);
/* Get strings' lengths. */
size_t append_size = strlen(append) + 1;
size_t original_size = strlen(output);
size_t total_size = original_size + append_size;
/* Allocate memory for new string. */
unsigned char* output_new = realloc(output, total_size);
if(output_new == NULL){
printf("Unable to allocate %u bytes at: %p.\n", (unsigned int)total_size, (void*)&output);
free(output_new);
continue;
}
output = output_new;
/* Append string to original. */
memcpy((void*)(output + original_size), append, append_size);
/* Decrement counter. */
count--;
}
/* Done. */
va_end(strings);
return output;
}
/* Automatic counting of arguments. */
#define NARG(...) NARG_(__VA_ARGS__, RSEQ_N())
#define NARG_(...) ARG_N(__VA_ARGS__)
#define ARG_N(_1, _2, _3, _4, _5, _6, _7, _8, _9, _10, _11, _12, _13, _14, _15, _16, _17, _18, _19, _20, _21, _22, _23, _24, _25, _26, _27, _28, _29, _30, _31, _32, _33, _34, _35, _36, _37, _38, _39, _40, _41, _42, _43, _44, _45, _46, _47, _48, _49, _50, _51, _52, _53, _54, _55, _56, _57, _58, _59, _60, _61, _62, _63, _64, _65, _66, _67, _68, _69, _70, _71, _72, _73, _74, _75, _76, _77, _78, _79, _80, _81, _82, _83, _84, _85, _86, _87, _88, _89, _90, _91, _92, _93, _94, _95, _96, _97, _98, _99, _100, _101, _102, _103, _104, _105, _106, _107, _108, _109, _110, _111, _112, _113, _114, _115, _116, _117, _118, _119, _120, _121, _122, _123, _124, _125, _126, _127, N, ...) N
#define RSEQ_N() 127, 126, 125, 124, 123, 122, 121, 120, 119, 118, 117, 116, 115, 114, 113, 112, 111, 110, 109, 108, 107, 106, 105, 104, 103, 102, 101, 100, 99, 98, 97, 96, 95, 94, 93, 92, 91, 90, 89, 88, 87, 86, 85, 84, 83, 82, 81, 80, 79, 78, 77, 76, 75, 74, 73, 72, 71, 70, 69, 68, 67, 66, 65, 64, 63, 62, 61, 60, 59, 58, 57, 56, 55, 54, 53, 52, 51, 50, 49, 48, 47, 46, 45, 44, 43, 42, 41, 40, 39, 38, 37, 36, 35, 34, 33, 32, 31, 30, 29, 28, 27, 26, 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0
#define concat(...) concat(NARG(__VA_ARGS__), __VA_ARGS__)
/**----------------------------------------------------------------------------\
| Example usage. |
\-----------------------------------------------------------------------------*/
#include <locale.h>
#include <unistd.h>
#include <wchar.h>
int main(int argc, char** argv){
/* Normal strings. */
printf("Normal strings: %s", concat("Concatenate", " ", "me", "!", "\n"));
/* Messed up strings. */
printf("Messed up strings: %s", concat("", "\0\1\2\3\4\5\6\7", "Hello\0this_text", calloc(1, 1), "\0\111wont_show", " \0\2\222", "world\0up? ", "!\n"));
/* Malicious string. */
printf("%s", concat("Malicious string: ", "%d%n", ".\n"));
/* One character. */
printf("One character: %s.\n", concat("a"));
/* Empty string. */
printf("Empty string: %s.\n", concat(""));
/* Junk data. */
printf("%s", concat("Junk data: ", malloc(1), ".\n"));
/* Done! */
return 0;
}