arbitrary base convertions

4 files changed, 69 insertions, 0 deletions

diff --git a/docs/crypto.md b/docs/crypto.md
index 01fe7be..997ede9 100644
--- a/docs/crypto.md
+++ b/docs/crypto.md
@@ -77,3 +77,14 @@ all functions have 1 argument which is a string, unless noted otherwise
 llib.crypto.base64encode("purr") -- cHVycg==
 llib.crypto.base64decode("cHVycg==") -- purr
 ```
+
+## baseconvert 
+
+'accepts an array of integers
+
+converts an array from base N to base T (in reversed order)
+
+```lua
+--                      input                           N  T
+llib.crypto.baseconvert({1, 1, 0, 1, 0, 1, 0, 0, 0, 1}, 2, 10) -- {9, 4, 8} (which is 849)
+```
diff --git a/src/crypto.h b/src/crypto.h
index fc1101e..564ea58 100644
--- a/src/crypto.h
+++ b/src/crypto.h
@@ -28,6 +28,7 @@
 
 #include "encode/uuencode.h"
 #include "encode/base64.h"
+#include "encode/baseN.h"
 
 unsigned i_lr(unsigned, unsigned);
 unsigned i_rr(unsigned, unsigned);
@@ -63,6 +64,7 @@ static const luaL_Reg crypto_function_list [] = {
       {"base64encode",l_base64encode},
       {"base64decode",l_base64decode},
 
+      {"baseconvert",l_baseconvert},
 
       {NULL,NULL}
 };
diff --git a/src/encode/baseN.c b/src/encode/baseN.c
new file mode 100644
index 0000000..9c911c2
--- /dev/null
+++ b/src/encode/baseN.c
@@ -0,0 +1,53 @@
+/*
+local function to_base10(inp,basein)
+  local out = 0
+  for i=1,#inp do
+    out = out + (inp[i]*(basein^(#inp - i)))
+  end
+  return out
+end
+
+local function from_base10(inp,outbase)
+  local out = {}
+  while inp > 0 do
+    local rem = inp % outbase
+    inp = math.floor(inp / outbase)
+    table.insert(out,1,rem)
+  end
+  return out
+end
+local function baseT_to_N(inp,basein,baseout)
+  return from_base10(to_base10(inp,basein),baseout)
+end
+*/
+#include <math.h>
+#include <stdint.h>
+#include "../lua.h"
+#include "../table.h"
+
+int l_baseconvert(lua_State* L){  
+  luaL_checktype(L, 1, LUA_TTABLE);
+  int64_t base_import = luaL_checkinteger(L, 2);  
+  int64_t base_export = luaL_checkinteger(L, 3);  
+  size_t len = lua_objlen(L,1);
+  uint64_t out = 0;
+
+  for(size_t i = 1; i <= len; i++){
+    lua_pushnumber(L, i);
+    lua_gettable(L, 1);
+
+    out += luaL_checkinteger(L, -1) * pow(base_import, len - i); 
+  }
+
+  lua_newtable(L);
+  for(int i = 1; out > 0; i++){
+    uint64_t rem = out % base_export;
+    out /= base_export;
+        
+    lua_pushnumber(L,i);
+    lua_pushnumber(L, rem);
+    lua_settable(L, -3);
+  }
+
+  return 1;
+};
diff --git a/src/encode/baseN.h b/src/encode/baseN.h
new file mode 100644
index 0000000..dc4d875
--- /dev/null
+++ b/src/encode/baseN.h
@@ -0,0 +1,3 @@
+#include "../lua.h"
+
+int l_baseconvert(lua_State*);