Base64 code in C Language

C does not contain strings. It must be implemented using char *.

# Include <stdio. h> # include "base. H "const char base [] =" character +/= "; char * base64_encode (const char * data, int data_len) {// int data_len = strlen (data ); int prepare = 0; int ret_len; int temp = 0; char * ret = NULL; char * f = NULL; int TMP = 0; char changed [4]; int I = 0; ret_len = data_len/3; temp = data_len % 3; if (temp> 0) {ret_len + = 1;} ret_len = ret_len * 4 + 1; ret = (char *) malloc (ret_len); If (ret = NULL) {printf ("no enough memory. \ n "); exit (0);} memset (Ret, 0, ret_len); F = ret; while (TMP <data_len) {temp = 0; prepare = 0; memset (changed, '\ 0', 4); While (temp <3) {// printf ("tmp = % d \ n", TMP ); if (TMP> = data_len) {break;} prepare = (prepare <8) | (data [TMP] & 0xff); TMP ++; temp ++ ;} prepare = (prepare <(3-temp) * 8); // printf ("before for: temp = % d, prepare = % d \ n", temp, prepare); for (I = 0; I <4; I ++) {If (temp <I) {changed [I] = 0x40 ;} else {changed [I] = (prepare> (3-I) * 6) & 0x3f;} * f = base [changed [I]; // printf ("%. 2x ", changed [I]); F ++;} * f = '\ 0'; return ret;}/**/static char find_pos (char ch) {char * PTR = (char *) strrchr (base, CH); // the last position (the only) in base [] Return (PTR-base );} /**/char * base64_decode (const char * data, int data_len) {int ret_len = (data_len/4) * 3; int counter _count = 0; char * ret = NULL; char * f = NULL; int TMP = 0; int temp = 0; char need [3]; int prepare = 0; int I = 0; if (* (Data + data_len-1) = ') {response _count + = 1;} If (* (Data + data_len-2) = ') {export _count + = 1;} If (* (Data + data_len-3) = ') {// seems impossible export _count + = 1;} switch (export _count) {Case 0: ret_len + = 4; // 3 + 1 [1 for null] Break; Case 1: ret_len + = 4; // Ceil (6*3) /8) + 1 break; Case 2: ret_len + = 3; // Ceil (6*2)/8) + 1 break; Case 3: ret_len + = 2; // Ceil (6*1)/8) + 1 break;} ret = (char *) malloc (ret_len); If (ret = NULL) {printf ("no enough memory. \ n "); exit (0);} memset (Ret, 0, ret_len); F = ret; while (TMP <(data_len-assist_count) {temp = 0; prepare = 0; memset (need, 0, 4); While (temp <4) {If (TMP >=( data_len-keys _count) {break ;} prepare = (prepare <6) | (find_pos (data [TMP]); temp ++; TMP ++;} prepare = prepare <(4-temp) * 6); for (I = 0; I <3; I ++) {if (I = temp) {break;} * f = (char) (prepare> (2-I) * 8) & 0xff); F ++;} * f = '\ 0'; return ret ;}