From aacf2324c7ba1893fb2eccd63c16208706910994 Mon Sep 17 00:00:00 2001
From: Eric <eric@wolf42.net>
Date: Thu, 29 May 2025 16:02:45 +0200
Subject: [PATCH] improve decode time

atob() has been replaced with a lookup table, removing previous
conditionals and function calls necessary to decode.
---
 encode.c | 76 +++++++++++++++++++++++++++++---------------------------
 encode.h |  2 +-
 main.c   |  6 ++---
 3 files changed, 44 insertions(+), 40 deletions(-)

diff --git a/encode.c b/encode.c
index 861bae9..08d50f8 100644
--- a/encode.c
+++ b/encode.c
@@ -2,15 +2,35 @@
 
 #define PADDING '='
 
-unsigned char b64[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ" \
-                      "abcdefghijklmnopqrstuvwxyz" \
-                      "0123456789" \
-                      "+/";
+static
+unsigned char b64toascii[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ" \
+                             "abcdefghijklmnopqrstuvwxyz" \
+                             "0123456789" \
+                             "+/";
+
+static
+unsigned char b64urltoascii[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ" \
+                                "abcdefghijklmnopqrstuvwxyz" \
+                                "0123456789" \
+                                "-_";
+
+static
+unsigned char asciitob64[] = {
+     0,  0,  0,  0,  0,  0,  0,  0,  0,  0,
+     0,  0,  0,  0,  0,  0,  0,  0,  0,  0,
+     0,  0,  0,  0,  0,  0,  0,  0,  0,  0,
+     0,  0,  0,  0,  0,  0,  0,  0,  0,  0,
+     0,  0,  0, 62,  0, 62,  0, 63, 52, 53,
+    54, 55, 56, 57, 58, 59, 60, 61,  0,  0,
+     0,  0,  0,  0,  0,  0,  1,  2,  3,  4,
+     5,  6,  7,  8,  9, 10, 11, 12, 13, 14,
+    15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
+    25,  0,  0,  0,  0, 63,  0, 26, 27, 28,
+    29, 30, 31, 32, 33, 34, 35, 36, 37, 38,
+    39, 40, 41, 42, 43, 44, 45, 46, 47, 48,
+    49, 50, 51
+};
 
-unsigned char b64url[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ" \
-                         "abcdefghijklmnopqrstuvwxyz" \
-                         "0123456789" \
-                         "-_";
 
 int
 encode(unsigned char *op, int olen, unsigned char *sp, int url)
@@ -20,7 +40,7 @@ encode(unsigned char *op, int olen, unsigned char *sp, int url)
     unsigned char *sbeg;
     unsigned char *tend;
 
-    table = (!url) ? b64 : b64url;
+    table = (!url) ? b64toascii : b64urltoascii;
 
     sbeg = sp;
     tend = op + olen - (olen % 3);
@@ -52,52 +72,36 @@ encode(unsigned char *op, int olen, unsigned char *sp, int url)
 }
 
 int
-decode(unsigned char *sp, int slen, unsigned char *op, int url)
+decode(unsigned char *sp, int slen, unsigned char *op)
 {
-    int tmp, b, atob(int c, int url);
+    int tmp, b;
     unsigned char *obeg;
     unsigned char *qend;
 
     obeg = op;
     qend = sp + slen - (slen % 4);
     while (sp < qend) {
-        tmp = atob(*sp++, url) << 2;
-        b = atob(*sp++, url);
+        tmp = asciitob64[*sp++] << 2;
+        b = asciitob64[*sp++];
         *op++ = tmp + ((b & ~15) >> 4);
         tmp = (b & 15) << 4;
-        b = atob(*sp++, url);
+        b = asciitob64[*sp++];
         *op++ = tmp + ((b & ~3) >> 2);
-        *op++ = ((b & 3) << 6) + atob(*sp++, url);
+        *op++ = ((b & 3) << 6) + asciitob64[*sp++];
     }
     switch (slen % 4) {
         case 3:
-            tmp = atob(*sp++, url) << 2;
-            b = atob(*sp++, url);
+            tmp = asciitob64[*sp++] << 2;
+            b = asciitob64[*sp++];
             *op++ = tmp + ((b & ~15) >> 4);
             tmp = (b & 15) << 4;
-            *op++ = tmp + ((atob(*sp++, url) & ~3) >> 2);
+            *op++ = tmp + ((asciitob64[*sp++] & ~3) >> 2);
             break;
         case 2:
-            tmp = atob(*sp++, url) << 2;
-            *op++ = tmp + ((atob(*sp++, url) & ~15) >> 4);
+            tmp = asciitob64[*sp++] << 2;
+            *op++ = tmp + ((asciitob64[*sp++] & ~15) >> 4);
             break;
     }
 
     return op-obeg;
 }
-
-int atob(int c, int url)
-{
-    if (c >= 'A' && c <= 'Z')
-        c -= 'A';
-    else if (c >= 'a' && c <= 'z')
-        c = c - 'a' + 26;
-    else if (c >= '0' && c <= '9')
-        c = c - '0' + 26 * 2;
-    else if (c == ((!url) ? '+' : '-'))
-        c = 62;
-    else
-        c = 63;
-
-    return c;
-}
diff --git a/encode.h b/encode.h
index 425038c..7e6f217 100644
--- a/encode.h
+++ b/encode.h
@@ -5,6 +5,6 @@ int
 encode(unsigned char *op, int olen, unsigned char *sp, int url);
 
 int
-decode(unsigned char *sp, int slen, unsigned char *op, int url);
+decode(unsigned char *sp, int slen, unsigned char *op);
 
 #endif
diff --git a/main.c b/main.c
index d7d8530..bc612d5 100644
--- a/main.c
+++ b/main.c
@@ -4,8 +4,8 @@
 #include "output.h"
 #include "encode.h"
 
-#define OCTETBUF  300
-#define SXTETBUF  400
+#define OCTETBUF  1500
+#define SXTETBUF  2000
 
 unsigned char obuf[OCTETBUF];
 unsigned char sbuf[SXTETBUF];
@@ -54,7 +54,7 @@ main(int argc, char *argv[])
         }
         if (dec) {
             while ((n = readb((in) ? in : stdin, sbuf, SXTETBUF))) {
-                n = decode(sbuf, n, obuf, url);
+                n = decode(sbuf, n, obuf);
                 fwrite(obuf, sizeof(*obuf), n, (out) ? out : stdout);
             }
         } else if (wrp) {