base64_from.c

   1 #include <stddef.h>
   2 #include <stdint.h>
   3 #include "types.h"
   4 #include "base64.h"
   5
   6 static const u8 base64f[256] = {
   7         //00    01    02    03    04    05    06    07
   8         //08    09    0A    0B    0C    0D    0E    0F
   9         // 0x00..0x3F
  10         0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 0x00
  11         0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 0x08
  12         0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 0x10
  13         0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 0x18
  14         0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 0x20
  15         0xFF, 0xFF, 0xFF, 0x3E, 0xFF, 0xFF, 0xFF, 0x3F, // 0x28
  16         0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x3A, 0x3B, // 0x30
  17         0x3C, 0x3D, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 0x38
  18         // 0x40..0x7F
  19         0xFF, 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, // 0x40
  20         0x07, 0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, // 0x48
  21         0x0F, 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, // 0x50
  22         0x17, 0x18, 0x19, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 0x58
  23         0xFF, 0x1A, 0x1B, 0x1C, 0x1D, 0x1E, 0x1F, 0x20, // 0x60
  24         0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28, // 0x68
  25         0x29, 0x2A, 0x2B, 0x2C, 0x2D, 0x2E, 0x2F, 0x30, // 0x70
  26         0x31, 0x32, 0x33, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 0x78
  27         // 0x80..0xBF
  28         0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
  29         0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
  30         0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
  31         0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
  32         0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
  33         0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
  34         0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
  35         0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
  36         // 0xC0..0xFF
  37         0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
  38         0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
  39         0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
  40         0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
  41         0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
  42         0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
  43         0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
  44         0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
  45 };
  46
  47 size_t base64_from(u8 *dst,const char *src,size_t srclen)
  48 {
  49         if (srclen % 4) {
  50                 return -1;
  51         } else if (!srclen) {
  52                 return 0;
  53         }
  54
  55         size_t dstlen = BASE64_FROM_LEN(srclen);
  56         dstlen -= (src[srclen - 1] == '=');
  57         dstlen -= (src[srclen - 2] == '=');
  58
  59         for (size_t i = 0, j = 0; i < srclen;) {
  60                 u32 sixbits[4];
  61
  62                 sixbits[0] = base64f[(unsigned char)src[i++]];
  63                 sixbits[1] = base64f[(unsigned char)src[i++]];
  64                 sixbits[2] = (src[i] == '=' ? (0 & i++) : base64f[(unsigned char)src[i++]]);
  65                 sixbits[3] = (src[i] == '=' ? (0 & i++) : base64f[(unsigned char)src[i++]]);
  66
  67                 u32 threebytes = 0
  68                         | (sixbits[0] << (3 * 6))
  69                         | (sixbits[1] << (2 * 6))
  70                         | (sixbits[2] << (1 * 6))
  71                         | (sixbits[3] << (0 * 6));
  72
  73                 if (j < dstlen) dst[j++] = (threebytes >> (2 * 8));
  74                 if (j < dstlen) dst[j++] = (threebytes >> (1 * 8)) & 0xff;
  75                 if (j < dstlen) dst[j++] = (threebytes >> (0 * 8)) & 0xff;
  76         }
  77         return dstlen;
  78 }
  79
  80 int base64_valid(const char *src,size_t *count)
  81 {
  82         const char *p;
  83
  84         for (p = src;base64f[(u8)*p] != 0xFF;++p)
  85                 ;
  86
  87         for (;((size_t) (p - src)) % 4 != 0 && *p == '=';++p)
  88                 ;
  89
  90         if (count)
  91                 *count = (size_t) (p - src);
  92         return !*p && ((size_t) (p - src)) % 4 == 0;
  93 }