Add EncodeBase32() to Redbean (#856)

tool/net/help.txt

@@ -737,8 +737,20 @@ FUNCTIONS
           Turns ASCII base-16 hexadecimal byte string into binary string,
           case-insensitively. Non-hex characters may not appear in string.
 
+  DecodeBase32(ascii:str[, alphabet:str]) → binary:str
+          Turns ASCII into binary using provided alphabet. The default
+          decoding uses Crockford's base32 alphabet in a permissive way
+          that ignores whitespaces and dash ('-') and stops at the first
+          character outside of the alphabet.
+
+  EncodeBase32(binary:str[, alphabet:str]) → ascii:str
+          Turns binary into ASCII using provided alphabet (using Crockford's
+          base32 encoding by default). Any alphabet that has a power of 2
+          length (up to 128) may be supplied for encoding and decoding,
+          which allows to provide alternative base32 encodings.
+
   DecodeBase64(ascii:str) → binary:str
-          Turns ASCII into binary, in a permissive way that ignores
+          Turns ASCII into binary in a permissive way that ignores
           characters outside the base64 alphabet, such as whitespace. See
           decodebase64.c.
 

tool/net/lfuncs.c

@@ -605,6 +605,30 @@ int LuaEncodeLatin1(lua_State *L) {
   }
 }
 
+dontinline int LuaBase32Impl(lua_State *L,
+    char *B32(const char *, size_t, const char *, size_t, size_t *)) {
+  char *p;
+  size_t sl, al; // source/output and alphabet lengths
+  const char *s = luaL_checklstring(L, 1, &sl);
+  // use an empty string, as EncodeBase32 provides a default value
+  const char *a = luaL_optlstring(L, 2, "", &al);
+  if (!IS2POW(al) || al > 128 || al == 1)
+    return luaL_error(L, "alphabet length is not a power of 2 in range 2..128");
+  if (!(p = B32(s, sl, a, al, &sl)))
+    return luaL_error(L, "out of memory");
+  lua_pushlstring(L, p, sl);
+  free(p);
+  return 1;
+}
+
+int LuaEncodeBase32(lua_State *L) {
+  return LuaBase32Impl(L, EncodeBase32);
+}
+
+int LuaDecodeBase32(lua_State *L) {
+  return LuaBase32Impl(L, DecodeBase32);
+}
+
 int LuaEncodeHex(lua_State *L) {
   char *p;
   size_t n;

tool/net/lfuncs.h

@@ -20,10 +20,12 @@ int LuaCompress(lua_State *);
 int LuaCrc32(lua_State *);
 int LuaCrc32c(lua_State *);
 int LuaDecimate(lua_State *);
+int LuaDecodeBase32(lua_State *);
 int LuaDecodeBase64(lua_State *);
 int LuaDecodeHex(lua_State *);
 int LuaDecodeLatin1(lua_State *);
 int LuaDeflate(lua_State *);
+int LuaEncodeBase32(lua_State *);
 int LuaEncodeBase64(lua_State *);
 int LuaEncodeHex(lua_State *);
 int LuaEncodeLatin1(lua_State *);

tool/net/redbean.c

@@ -5126,11 +5126,13 @@ static const luaL_Reg kLuaFuncs[] = {
     {"Crc32", LuaCrc32},                                        //
     {"Crc32c", LuaCrc32c},                                      //
     {"Decimate", LuaDecimate},                                  //
+    {"DecodeBase32", LuaDecodeBase32},                          //
     {"DecodeBase64", LuaDecodeBase64},                          //
     {"DecodeHex", LuaDecodeHex},                                //
     {"DecodeJson", LuaDecodeJson},                              //
     {"DecodeLatin1", LuaDecodeLatin1},                          //
     {"Deflate", LuaDeflate},                                    //
+    {"EncodeBase32", LuaEncodeBase32},                          //
     {"EncodeBase64", LuaEncodeBase64},                          //
     {"EncodeHex", LuaEncodeHex},                                //
     {"EncodeJson", LuaEncodeJson},                              //