C语言 实现base64

it2022-05-07  0

#include <stdio.h> const char base[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/="; char* base64_encode(const char* data, int data_len); char *base64_decode(const char* data, int data_len); static char find_pos(char ch); int main(int argc, char* argv[]) { char *t = "那个abcd你好吗,哈哈,ANMOL"; int i = 0; int j = strlen(t); char *enc = base64_encode(t, j); int len = strlen(enc); char *dec = base64_decode(enc, len); printf("\noriginal: %s\n", t); printf("\nencoded : %s\n", enc); printf("\ndecoded : %s\n", dec); free(enc); free(dec); return 0; } /* */ 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 equal_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) == '=') { equal_count += 1; } if (*(data + data_len - 2) == '=') { equal_count += 1; } if (*(data + data_len - 3) == '=') {//seems impossible equal_count += 1; } switch (equal_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 - equal_count)) { temp = 0; prepare = 0; memset(need, 0, 4); while (temp < 4) { if (tmp >= (data_len - equal_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; } <script type="text/javascript"> $(function () { $('pre.prettyprint code').each(function () { var lines = $(this).text().split('\n').length; var $numbering = $('<ul/>').addClass('pre-numbering').hide(); $(this).addClass('has-numbering').parent().append($numbering); for (i = 1; i <= lines; i++) { $numbering.append($('<li/>').text(i)); }; $numbering.fadeIn(1700); }); }); </script>

转载于:https://www.cnblogs.com/lindexi/p/6949704.html

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