add man page and unit tests for scan_base64url

textcode/scan_base64url.c

@@ -15,17 +15,36 @@ static inline int dec(unsigned char x) {
 size_t scan_base64url(const char *src,char *dest,size_t *destlen) {
   unsigned short tmp=0,bits=0;
   register const unsigned char* s=(const unsigned char*) src;
-  const char* orig=dest;
-  for (;;) {
+  size_t i,j=0;
+  for (i=0;;) {
     int a=dec(*s);
-    if (a<0) break;
+    if (a<0) break;	/* base64url does not have padding */
     tmp=(tmp<<6)|a; bits+=6;
     ++s;
     if (bits>=8) {
-      *dest=(tmp>>(bits-=8));
-      ++dest;
+      bits-=8;
+      if (dest) dest[i]=(tmp>>bits);
+      ++i;
     }
   }
-  *destlen=dest-orig;
+  if (destlen) *destlen=i;
   return (const char*)s-src;
 }
+
+#ifdef UNITTEST
+#include <assert.h>
+#include <string.h>
+#include <stdio.h>
+
+int main() {
+  char buf[100];
+  size_t i,l;
+  /* check that we don't consume padding */
+  memset(buf,0,10); assert(scan_base64url("Zm5vcmQ=",buf,&l)==7 && l==5 && !memcmp(buf,"fnord",6));
+  /* check that we don't insist on the padding */
+  memset(buf,0,10); assert(scan_base64url("Zm5vcmQ",buf,&l)==7 && l==5 && !memcmp(buf,"fnord",6));
+  /* check the special non-isalnum chars :) */
+  memset(buf,0,10); assert(scan_base64url("_-8=",buf,&l)==3 && l==2 && !memcmp(buf,"\xff\xef",3));
+  return 0;
+}
+#endif