Addition of encoder module with bas64 and hex encode/decode as per #925

app/include/user_modules.h

@@ -22,6 +22,7 @@
 #define LUA_USE_MODULES_COAP
 #define LUA_USE_MODULES_CRYPTO
 #define LUA_USE_MODULES_DHT
+#define LUA_USE_MODULES_ENCODER
 //#define LUA_USE_MODULES_ENDUSER_SETUP // USE_DNS in dhcpserver.h needs to be enabled for this module to work.
 #define LUA_USE_MODULES_FILE
 #define LUA_USE_MODULES_GPIO

app/modules/crypto.c

@@ -37,7 +37,29 @@ static int crypto_sha1( lua_State* L )
   return 1;
 }
 
+#ifdef LUA_USE_MODULES_ENCODER
+static int call_endcoder( lua_State* L, const char *function ) {
+  if (lua_gettop(L) != 1) { 
+    luaL_error(L, "%s must have one argument", function);
+  }
+  lua_getfield(L, LUA_GLOBALSINDEX, "encoder");
+  if (!lua_istable(L, -1) && !lua_isrotable(L, -1)) { // also need table just in case encoder has been overloaded
+    luaL_error(L, "Cannot find encoder.%s", function); 
+  }
+  lua_getfield(L, -1, function);
+  lua_insert(L, 1);    //move function below the argument
+  lua_pop(L, 1);       //and dump the encoder rotable from stack.
+  lua_call(L,1,1);     // call encoder.xxx(string)
+  return 1;
+}
 
+static int crypto_base64_encode (lua_State* L) { 
+  return call_endcoder(L, "toBase64"); 
+}
+static int crypto_hex_encode (lua_State* L) { 
+  return call_endcoder(L, "toHex"); 
+}
+#else
 static const char* bytes64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
 /**
   * encoded = crypto.toBase64(raw)
@@ -84,7 +106,7 @@ static int crypto_hex_encode( lua_State* L)
   c_free(out);
   return 1;
 }
-
+#endif
 /**
   * masked = crypto.mask(message, mask)
   *

app/modules/encoder.c

@@ -0,0 +1,154 @@
+// Module encoders
+
+#include "module.h"
+#include "lauxlib.h"
+#include "lmem.h"
+#include "c_string.h"
+#define BASE64_INVALID '\xff'
+#define BASE64_PADDING '='
+#define ISBASE64(c) (unbytes64[c] != BASE64_INVALID)
+
+static const char b64[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
+
+static char *toBase64 ( lua_State* L, const char *msg, size_t *len){
+  size_t i, n = *len;
+
+  if (!n)  // handle empty string case 
+    return NULL;
+
+  char* q, *out = (char*)luaM_malloc(L, (n + 2) / 3 * 4);
+  char bytes64[sizeof(b64)];
+  c_memcpy(bytes64, b64, sizeof(b64));   //Avoid lots of flash unaligned fetches
+
+  for (i = 0, q = out; i < n; i += 3) {
+    int a = msg[i];
+    int b = (i + 1 < n) ? msg[i + 1] : 0;
+    int c = (i + 2 < n) ? msg[i + 2] : 0;
+    *q++ = bytes64[a >> 2];
+    *q++ = bytes64[((a & 3) << 4) | (b >> 4)];
+    *q++ = (i + 1 < n) ? bytes64[((b & 15) << 2) | (c >> 6)] : BASE64_PADDING;
+    *q++ = (i + 2 < n) ? bytes64[(c & 63)] : BASE64_PADDING;
+  }
+  *len = q - out;
+  return out;
+}
+
+static char *fromBase64 ( lua_State* L, const char *enc_msg, size_t *len){
+  int i, n = *len, pad = 0;
+  unsigned const char *p;
+  unsigned char unbytes64[CHAR_MAX+1-CHAR_MIN], *msg, *q, a, b, c, d;
+
+  if (!n)  // handle empty string case 
+    return NULL;
+
+  if (n % 4)
+    luaL_error (L, "Invalid base64 string"); 
+
+  c_memset(unbytes64, BASE64_INVALID, sizeof(unbytes64));
+  for (i = 0; i < sizeof(b64)-1; i++) unbytes64[b64[i]] = i;  // sequential so no exceptions 
+
+  if (enc_msg[n-1] == BASE64_PADDING) {
+    pad =  (enc_msg[n-2] != BASE64_PADDING) ? 1 : 2;
+  }    
+
+ for (i = 0; i < n - pad; i++) if (!ISBASE64(enc_msg[i])) luaL_error (L, "Invalid base64 string");
+  unbytes64[BASE64_PADDING] = 0;
+
+  msg = q = (unsigned char*) luaM_malloc(L, 1+ (3 * n / 4)); 
+  for (i = 0, p = (unsigned char*) enc_msg;; i+=4)  {
+    a = unbytes64[*p++], b = unbytes64[*p++], c = unbytes64[*p++], d = unbytes64[*p++] ;
+    if (i > n-4) break;
+    *q++ = (a << 2) | (b >> 4);
+    *q++ = (b << 4) | (c >> 2);
+    *q++ = (c << 6) | d;
+  }
+
+  if (pad) {
+    *q++ = (a << 2) | (b >> 4);
+    if (pad == 1) *q++ = (b << 4) | (c >> 2);
+  }
+  *len = q - msg;
+  return (char *) msg;
+}
+
+static inline char to_hex_nibble(unsigned char b) {
+  return b + ( b < 10 ? '0' : 'a' - 10 );
+  }
+
+static char *toHex ( lua_State* L, const char *msg, size_t *len){
+  int i, n = *len;
+  char *q, *out = (char*)luaM_malloc(L, n * 2);
+  for (i = 0, q = out; i < n; i++) {
+    *q++ = to_hex_nibble(msg[i] >> 4);
+    *q++ = to_hex_nibble(msg[i] & 0xf);
+  }
+  *len = 2*n; 
+  return out;
+}
+
+static char *fromHex ( lua_State* L, const char *msg, size_t *len){
+  int i, n = *len;
+  const char *p;
+  char b, *q, *out = (char*)luaM_malloc(L, n * 2);
+  unsigned char c;
+
+  if (n &1)
+    luaL_error (L, "Invalid hex string");
+
+  for (i = 0, p = msg, q = out; i < n; i++) {
+     if (*p >= '0' && *p <= '9') {
+       b = *p++ - '0';
+     } else if (*p >= 'a' && *p <= 'f') {
+       b = *p++ - ('a' - 10);
+     } else if (*p >= 'A' && *p <= 'F') {
+       b = *p++ - ('A' - 10);
+     } else {
+       luaL_error (L, "Invalid hex string");
+     }
+     if ((i&1) == 0) {
+       c = b<<4;
+     } else {
+       *q++ = c+ b;
+     }    
+  }
+  *len = n>>1; 
+  return out;
+}
+
+// All encoder functions are of the form:
+// Lua:  output_string = encoder.function(input_string) 
+// Where input string maybe empty, but not nil
+// Hence these all chare the do_func wrapper
+static int do_func (lua_State *L, char * (*conv_func)(lua_State *, const char *, size_t *)) {
+  size_t l;
+  const char *input = luaL_checklstring(L, 1, &l);
+//  luaL_argcheck(L, l>0, 1, "input string empty");
+  char *output = conv_func(L, input, &l);
+
+  if (output) {
+    lua_pushlstring(L, output, l);
+    luaM_free(L, output);
+  } else {
+    lua_pushstring(L, "");
+  }
+  return 1;
+}
+
+#define DECLARE_FUNCTION(f) static int encoder_ ## f (lua_State *L) \
+{ return do_func(L, f); }
+
+  DECLARE_FUNCTION(fromBase64);
+  DECLARE_FUNCTION(toBase64);
+  DECLARE_FUNCTION(fromHex);
+  DECLARE_FUNCTION(toHex);
+
+// Module function map
+static const LUA_REG_TYPE encoder_map[] = {
+  { LSTRKEY("fromBase64"), LFUNCVAL(encoder_fromBase64)  },
+  { LSTRKEY("toBase64"),   LFUNCVAL(encoder_toBase64) },
+  { LSTRKEY("fromHex"),    LFUNCVAL(encoder_fromHex)  },
+  { LSTRKEY("toHex"),      LFUNCVAL(encoder_toHex) },
+  { LNILKEY, LNILVAL }
+};
+
+NODEMCU_MODULE(ENCODER, "encoder", encoder_map, NULL);

docs/en/modules/encoder.md

@@ -0,0 +1,75 @@
+# encoder Module
+
+The encoder modules provides various functions for encoding and decoding byte data.
+
+## encoder.toBase64()
+
+Provides a Base64 representation of a (binary) Lua string.
+
+#### Syntax
+`b64 = encoder.toBase64(binary)`
+
+#### Parameters
+`binary` input string to Base64 encode
+
+#### Return
+A Base64 encoded string.
+
+#### Example
+```lua
+print(encoder.toBase64(cyrpto.hash("sha1","abc")))
+```
+
+## encoder.fromBase64()
+
+Decodes a Base64 representation of a (binary) Lua string back into the original string.
+
+#### Syntax
+`binary_string = encoder.toBase64(b64)`
+
+#### Parameters
+`b64` Base64 encoded input string 
+
+#### Return
+The decoded Lua (binary) string.
+
+#### Example
+```lua
+print(encoder.fromBase64(encoder.toBase64("hello world")))
+```
+
+## encoder.toHex()
+
+Provides an ASCII hex representation of a (binary) Lua string. Each byte in the input string is represented as two hex characters in the output.
+
+#### Syntax
+`hexstr = encoder.toHex(binary)`
+
+#### Parameters
+`binary` input string to get hex representation for
+
+#### Returns
+An ASCII hex string.
+
+#### Example
+```lua
+print(encoder.toHex(crypto.hash("sha1","abc")))
+```
+
+## encoder.fromHex()
+
+Provides a Lua binary string decode of a ASCII hex string. Each byte in the output string is represented as two hex characters in the input.
+
+#### Syntax
+`binary = encoder.toHex(hexstr)`
+
+#### Parameters
+`hexstr`  An ASCII hex string.
+
+#### Returns
+Decoded string of hex representation.
+
+#### Example
+```lua
+print(encoder.fromHex("6a6a6a")))
+```

mkdocs.yml

@@ -42,6 +42,7 @@ pages:
         - 'coap': 'en/modules/coap.md'
         - 'crypto': 'en/modules/crypto.md'
         - 'dht': 'en/modules/dht.md'
+        - 'encoder': 'en/modules/encoder.md'
         - 'enduser setup': 'en/modules/enduser-setup.md'
         - 'file': 'en/modules/file.md'
         - 'gpio': 'en/modules/gpio.md'