From a91be306b1fbe2534f9d8c8ceb7b143042fb1083 Mon Sep 17 00:00:00 2001
From: Eric <eric@wolf42.net>
Date: Mon, 26 May 2025 23:59:47 +0200
Subject: [PATCH] add base64url encoding option

---
 encode.c | 54 ++++++++++++++++++++++++++++++------------------------
 encode.h |  4 ++--
 main.c   | 11 +++++++----
 3 files changed, 39 insertions(+), 30 deletions(-)

diff --git a/encode.c b/encode.c
index 576f9f3..cee611f 100644
--- a/encode.c
+++ b/encode.c
@@ -7,32 +7,38 @@ unsigned char b64[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ" \
                       "0123456789" \
                       "+/";
 
+unsigned char b64u[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ" \
+                       "abcdefghijklmnopqrstuvwxyz" \
+                       "0123456789" \
+                       "-_";
+
 int
-encode(unsigned char *op, int olen, unsigned char *sp)
+encode(unsigned char *op, int olen, unsigned char *sp, int url)
 {
     int n;
-    unsigned char *sb;
+    unsigned char *sb, *enc;
 
     sb = sp;
+    enc = (!url) ? b64 : b64u;
     switch (olen) {
         case 3:
-            *sp++ = b64[(*op & ~3) >> 2];
+            *sp++ = enc[(*op & ~3) >> 2];
             n = (*op++ & 3) << 4;
-            *sp++ = b64[n + ((*op & ~15) >> 4)];
+            *sp++ = enc[n + ((*op & ~15) >> 4)];
             n = (*op++ & 15) << 2;
-            *sp++ = b64[n + ((*op & 192) >> 6)];
-            *sp = b64[*op & ~192];
+            *sp++ = enc[n + ((*op & 192) >> 6)];
+            *sp = enc[*op & ~192];
             break;
         case 2:
-            *sp++ = b64[(*op & ~3) >> 2];
+            *sp++ = enc[(*op & ~3) >> 2];
             n = (*op++ & 3) << 4;
-            *sp++ = b64[n + ((*op & ~15) >> 4)];
-            *sp++ = b64[(*op & 15) << 2];
+            *sp++ = enc[n + ((*op & ~15) >> 4)];
+            *sp++ = enc[(*op & 15) << 2];
             *sp = PADDING;
             break;
         case 1:
-            *sp++ = b64[(*op & ~3) >> 2];
-            *sp++ = b64[(*op & 3) << 4];
+            *sp++ = enc[(*op & ~3) >> 2];
+            *sp++ = enc[(*op & 3) << 4];
             *sp++ = PADDING;
             *sp = PADDING;
             break;
@@ -42,42 +48,42 @@ encode(unsigned char *op, int olen, unsigned char *sp)
 }
 
 int
-decode(unsigned char *sp, int slen, unsigned char *op)
+decode(unsigned char *sp, int slen, unsigned char *op, int url)
 {
-    int n, b, atob(int c);
+    int n, b, atob(int c, int url);
     unsigned char *ob;
 
     ob = op;
     switch (slen) {
         case 4:
-            n = atob(*sp++) << 2;
-            b = atob(*sp++);
+            n = atob(*sp++, url) << 2;
+            b = atob(*sp++, url);
             *op++ = n + ((b & ~15) >> 4);
 
             n = (b & 15) << 4;
-            b = atob(*sp++);
+            b = atob(*sp++, url);
             *op++ = n + ((b & ~3) >> 2);
 
-            *op = ((b & 3) << 6) + atob(*sp);
+            *op = ((b & 3) << 6) + atob(*sp, url);
             break;
         case 3:
-            n = atob(*sp++) << 2;
-            b = atob(*sp++);
+            n = atob(*sp++, url) << 2;
+            b = atob(*sp++, url);
             *op++ = n + ((b & ~15) >> 4);
 
             n = (b & 15) << 4;
-            *op = n + ((atob(*sp) & ~3) >> 2);
+            *op = n + ((atob(*sp, url) & ~3) >> 2);
             break;
         case 2:
-            n = atob(*sp++) << 2;
-            *op = n + ((atob(*sp) & ~15) >> 4);
+            n = atob(*sp++, url) << 2;
+            *op = n + ((atob(*sp, url) & ~15) >> 4);
             break;
     }
 
     return op-ob+1;
 }
 
-int atob(int c)
+int atob(int c, int url)
 {
     if (c >= 'A' && c <= 'Z')
         c -= 'A';
@@ -85,7 +91,7 @@ int atob(int c)
         c = c - 'a' + 26;
     else if (c >= '0' && c <= '9')
         c = c - '0' + 26 * 2;
-    else if (c == '+')
+    else if (c == ((!url) ? '+' : '-'))
         c = 62;
     else
         c = 63;
diff --git a/encode.h b/encode.h
index f211396..2ea285a 100644
--- a/encode.h
+++ b/encode.h
@@ -2,9 +2,9 @@
 #define HEADER_ENCODE
 
 int
-encode(unsigned char *op, int olen, unsigned char *sp);
+encode(unsigned char *op, int olen, unsigned char *sp, int url);
 
 int
-decode(unsigned char *sp, int slen, unsigned char *op);
+decode(unsigned char *sp, int slen, unsigned char *op, int url);
 
 #endif
diff --git a/main.c b/main.c
index ff16bf6..b48684c 100644
--- a/main.c
+++ b/main.c
@@ -12,17 +12,20 @@ unsigned char sbuf[SBUFSIZE];
 int
 main(int argc, char *argv[])
 {
-    int c, n, dec, hlp;
+    int c, n, dec, url, hlp;
     char *prog = *argv;
     FILE *in, *out;
 
-    dec = hlp = 0;
+    dec = url = hlp = 0;
     while (--argc > 0 && (*++argv)[0] == '-')
         while ((c = *++argv[0]))
             switch (c) {
                 case 'd':
                     dec = 1;
                     break;
+                case 'u':
+                    url = 1;
+                    break;
                 case 'h':
                     hlp = 1;
                     break;
@@ -44,12 +47,12 @@ main(int argc, char *argv[])
         }
         if (dec) {
             while ((n = getsxts((argc >= 1) ? in : stdin, sbuf, SBUFSIZE))) {
-                n = decode(sbuf, n, obuf);
+                n = decode(sbuf, n, obuf, url);
                 fwrite(obuf, sizeof(*obuf), n, (argc == 2) ? out : stdout);
             }
         } else {
             while ((n = getocts((argc >= 1) ? in : stdin, obuf, OBUFSIZE))) {
-                encode(obuf, n, sbuf);
+                encode(obuf, n, sbuf, url);
                 fprintf((argc == 2) ? out : stdout, "%s", sbuf);
             }
         }