fetch and pull: learn --progress

diff --git a/base85.c b/base85.c
index b97f7f933a745c80dd02e04828380513a5a8df2e..e459feebbf90c6557dbf3ff913f83a57a8afb210 100644 (file)
--- a/base85.c
+++ b/base85.c
@@ -37,64 +37,62 @@ static void prep_base85(void)
        }
 }
 
-int decode_85(char *dst, char *buffer, int len)
+int decode_85(char *dst, const char *buffer, int len)
 {
        prep_base85();
 
        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. */
+               if (0xffffffff / 85 < acc ||
+                   0xffffffff - de < (acc *= 85))
+                       return 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");
 
        return 0;
 }
 
-void encode_85(char *buf, unsigned char *data, int bytes)
+void encode_85(char *buf, const unsigned char *data, int bytes)
 {
-       prep_base85();
-
        say("encode 85");
        while (bytes) {
                unsigned acc = 0;
                int cnt;
-               for (cnt = 0; cnt < 4 && bytes; cnt++, bytes--) {
-                       int ch = *data++;
-                       acc |= ch << ((3-cnt)*8);
+               for (cnt = 24; cnt >= 0; cnt -= 8) {
+                       unsigned ch = *data++;
+                       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;
        }
@@ -112,7 +110,7 @@ int main(int ac, char **av)
                int len = strlen(av[2]);
                encode_85(buf, av[2], len);
                if (len <= 26) len = len + 'A' - 1;
-               else len = len + 'a' - 26 + 1;
+               else len = len + 'a' - 26 - 1;
                printf("encoded: %c%s\n", len, buf);
                return 0;
        }