Tweaking Base85 with a different charset, and a lookup table.

1 files changed, 32 insertions, 10 deletions

diff --git a/lib/Base85.cc b/lib/Base85.cc
index c228022..d1f4baa 100644
--- a/lib/Base85.cc
+++ b/lib/Base85.cc
@@ -19,6 +19,28 @@
 
 #include <Base85.h>
 
+// Banned chars: ",/:.[\]
+static char cb85[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789!#$%&'()*+-;<=>?@^_`{|}";
+static char lookup[] = {
+//  x0  x1  x2  x3  x4  x5  x6  x7  x8  x9  xA  xB  xC  xD  xE  xF
+     0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  // 0x
+     0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  // 1x
+     0, 62,  0, 63, 64, 65, 66, 67, 68, 69, 70, 71,  0, 72,  0,  0,  // 2x
+    52, 53, 54, 55, 56, 57, 58, 59, 60, 61,  0, 73, 74, 75, 76, 77,  // 3x
+    78,  0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14,  // 4x
+    15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25,  0,  0,  0, 79, 80,  // 5x
+    81, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,  // 6x
+    41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 82, 83, 84,  0,  0,  // 7x
+     0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  // 8x
+     0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  // 9x
+     0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  // Ax
+     0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  // Bx
+     0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  // Cx
+     0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  // Dx
+     0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  // Ex
+     0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  // Fx
+};
+
 String Base85::encode_block(unsigned char in_tab[4], int len) {
     unsigned int tuple;
     char r[6];
@@ -28,15 +50,15 @@ String Base85::encode_block(unsigned char in_tab[4], int len) {
     tuple |= in_tab[2] << 16;
     tuple |= in_tab[3] << 24;
     
-    r[0] = (tuple % 85) + '!';
+    r[0] = cb85[tuple % 85];
     tuple /= 85;
-    r[1] = (tuple % 85) + '!';
+    r[1] = cb85[tuple % 85];
     tuple /= 85;
-    r[2] = len > 1 ? (tuple % 85) + '!' : '~';
+    r[2] = len > 1 ? cb85[tuple % 85] : '~';
     tuple /= 85;
-    r[3] = len > 2 ? (tuple % 85) + '!' : '~';
+    r[3] = len > 2 ? cb85[tuple % 85] : '~';
     tuple /= 85;
-    r[4] = len > 3 ? (tuple % 85) + '!' : '~';
+    r[4] = len > 3 ? cb85[tuple % 85] : '~';
     r[5] = 0;
     
     return r;
@@ -79,11 +101,11 @@ int Base85::decode_block(char s1, char s2, char s3, char s4, char s5, unsigned c
     s4 = (s4 == '~') || (s4 == 0) ? '!' : s4;
     s5 = (s5 == '~') || (s5 == 0) ? '!' : s5;
     
-    sb1 = s1 - '!';
-    sb2 = s2 - '!';
-    sb3 = s3 - '!';
-    sb4 = s4 - '!';
-    sb5 = s5 - '!';
+    sb1 = lookup[s1];
+    sb2 = lookup[s2];
+    sb3 = lookup[s3];
+    sb4 = lookup[s4];
+    sb5 = lookup[s5];
     
     tuple  = sb5; tuple *= 85;
     tuple += sb4; tuple *= 85;