diff options
Diffstat (limited to 'base85.c')
| -rw-r--r-- | base85.c | 64 |
1 files changed, 35 insertions, 29 deletions
@@ -44,34 +44,38 @@ int decode_85(char *dst, char *buffer, int len) say2("decode 85 <%.*s>", len/4*5, buffer); while (len) { unsigned acc = 0; - int cnt; - for (cnt = 0; cnt < 5; cnt++, buffer++) { - int ch = *((unsigned char *)buffer); - int de = de85[ch]; - if (!de) + int de, cnt = 4; + unsigned char ch; + do { + ch = *buffer++; + de = de85[ch]; + if (--de < 0) return error("invalid base85 alphabet %c", ch); - de--; - if (cnt == 4) { - /* - * Detect overflow. The largest - * 5-letter possible is "|NsC0" to - * encode 0xffffffff, and "|NsC" gives - * 0x03030303 at this point (i.e. - * 0xffffffff = 0x03030303 * 85). - */ - if (0x03030303 < acc || - (0x03030303 == acc && de)) - error("invalid base85 sequence %.5s", - buffer-3); - } acc = acc * 85 + de; - say1(" <%08x>", acc); - } + } while (--cnt); + ch = *buffer++; + de = de85[ch]; + if (--de < 0) + return error("invalid base85 alphabet %c", ch); + /* + * Detect overflow. The largest + * 5-letter possible is "|NsC0" to + * encode 0xffffffff, and "|NsC" gives + * 0x03030303 at this point (i.e. + * 0xffffffff = 0x03030303 * 85). + */ + if (0x03030303 < acc || + 0xffffffff - de < (acc *= 85)) + error("invalid base85 sequence %.5s", buffer-5); + acc += de; say1(" %08x", acc); - for (cnt = 0; cnt < 4 && len; cnt++, len--) { - *dst++ = (acc >> 24) & 0xff; - acc = acc << 8; - } + + cnt = (len < 4) ? len : 4; + len -= cnt; + do { + acc = (acc << 8) | (acc >> 24); + *dst++ = acc; + } while (--cnt); } say("\n"); @@ -86,15 +90,17 @@ void encode_85(char *buf, unsigned char *data, int bytes) while (bytes) { unsigned acc = 0; int cnt; - for (cnt = 0; cnt < 4 && bytes; cnt++, bytes--) { + for (cnt = 24; cnt >= 0; cnt -= 8) { int ch = *data++; - acc |= ch << ((3-cnt)*8); + acc |= ch << cnt; + if (--bytes == 0) + break; } say1(" %08x", acc); - for (cnt = 0; cnt < 5; cnt++) { + for (cnt = 4; cnt >= 0; cnt--) { int val = acc % 85; acc /= 85; - buf[4-cnt] = en85[val]; + buf[cnt] = en85[val]; } buf += 5; } |