Re: Lua-based applications get to Mactel faster

[Luiz Henrique de Figueiredo <lhf@...>]

> Isn't there some sort of issue with bytecode endianness that has to be
> overcome, or are y'all not distributing bytecode?

They're probably using a modified bytecode loader that does byte swap.
Here is a patch and a complete lundump.c that does that.
--lhf

--- lundump.c,orig	2006-02-16 13:53:49.000000000 -0200
+++ lundump.c	2006-02-21 16:03:32.000000000 -0300
@@ -25,6 +25,7 @@
  ZIO* Z;
  Mbuffer* b;
  const char* name;
+ int swap;
 } LoadState;
 
 #ifdef LUAC_TRUST_BINARIES
@@ -39,7 +40,6 @@
 }
 #endif
 
-#define LoadMem(S,b,n,size)	LoadBlock(S,b,(n)*(size))
 #define	LoadByte(S)		(lu_byte)LoadChar(S)
 #define LoadVar(S,x)		LoadMem(S,&x,1,sizeof(x))
 #define LoadVector(S,b,n,size)	LoadMem(S,b,n,size)
@@ -50,6 +50,49 @@
  IF (r!=0, "unexpected end");
 }
 
+static void LoadMem (LoadState* S, void* b, int n, size_t size)
+{
+ LoadBlock(S,b,n*size);
+ if (S->swap)
+ {
+  char* p=(char*) b;
+  char c;
+  switch (size)
+  {
+   case 1:
+  	break;
+   case 2:
+	while (n--)
+	{
+	 c=p[0]; p[0]=p[1]; p[1]=c;
+	 p+=2;
+	}
+  	break;
+   case 4:
+	while (n--)
+	{
+	 c=p[0]; p[0]=p[3]; p[3]=c;
+	 c=p[1]; p[1]=p[2]; p[2]=c;
+	 p+=4;
+	}
+  	break;
+   case 8:
+	while (n--)
+	{
+	 c=p[0]; p[0]=p[7]; p[7]=c;
+	 c=p[1]; p[1]=p[6]; p[6]=c;
+	 c=p[2]; p[2]=p[5]; p[5]=c;
+	 c=p[3]; p[3]=p[4]; p[4]=c;
+	 p+=8;
+	}
+  	break;
+   default:
+   	IF(1, "bad size");
+  	break;
+  }
+ }
+}
+
 static int LoadChar(LoadState* S)
 {
  char x;
@@ -182,6 +225,7 @@
  char s[LUAC_HEADERSIZE];
  luaU_header(h);
  LoadBlock(S,s,LUAC_HEADERSIZE);
+ S->swap=(s[6]!=h[6]); s[6]=h[6];
  IF (memcmp(h,s,LUAC_HEADERSIZE)!=0, "bad header");
 }
 

/*
** $Id: lundump.c,v 1.60 2006/02/16 15:53:49 lhf Exp $
** load precompiled Lua chunks
** See Copyright Notice in lua.h
*/

#include <string.h>

#define lundump_c
#define LUA_CORE

#include "lua.h"

#include "ldebug.h"
#include "ldo.h"
#include "lfunc.h"
#include "lmem.h"
#include "lobject.h"
#include "lstring.h"
#include "lundump.h"
#include "lzio.h"

typedef struct {
 lua_State* L;
 ZIO* Z;
 Mbuffer* b;
 const char* name;
 int swap;
} LoadState;

#ifdef LUAC_TRUST_BINARIES
#define IF(c,s)
#else
#define IF(c,s)		if (c) error(S,s)

static void error(LoadState* S, const char* why)
{
 luaO_pushfstring(S->L,"%s: %s in precompiled chunk",S->name,why);
 luaD_throw(S->L,LUA_ERRSYNTAX);
}
#endif

#define	LoadByte(S)		(lu_byte)LoadChar(S)
#define LoadVar(S,x)		LoadMem(S,&x,1,sizeof(x))
#define LoadVector(S,b,n,size)	LoadMem(S,b,n,size)

static void LoadBlock(LoadState* S, void* b, size_t size)
{
 size_t r=luaZ_read(S->Z,b,size);
 IF (r!=0, "unexpected end");
}

static void LoadMem (LoadState* S, void* b, int n, size_t size)
{
 LoadBlock(S,b,n*size);
 if (S->swap)
 {
  char* p=(char*) b;
  char c;
  switch (size)
  {
   case 1:
  	break;
   case 2:
	while (n--)
	{
	 c=p[0]; p[0]=p[1]; p[1]=c;
	 p+=2;
	}
  	break;
   case 4:
	while (n--)
	{
	 c=p[0]; p[0]=p[3]; p[3]=c;
	 c=p[1]; p[1]=p[2]; p[2]=c;
	 p+=4;
	}
  	break;
   case 8:
	while (n--)
	{
	 c=p[0]; p[0]=p[7]; p[7]=c;
	 c=p[1]; p[1]=p[6]; p[6]=c;
	 c=p[2]; p[2]=p[5]; p[5]=c;
	 c=p[3]; p[3]=p[4]; p[4]=c;
	 p+=8;
	}
  	break;
   default:
   	IF(1, "bad size");
  	break;
  }
 }
}

static int LoadChar(LoadState* S)
{
 char x;
 LoadVar(S,x);
 return x;
}

static int LoadInt(LoadState* S)
{
 int x;
 LoadVar(S,x);
 IF (x<0, "bad integer");
 return x;
}

static lua_Number LoadNumber(LoadState* S)
{
 lua_Number x;
 LoadVar(S,x);
 return x;
}

static TString* LoadString(LoadState* S)
{
 size_t size;
 LoadVar(S,size);
 if (size==0)
  return NULL;
 else
 {
  char* s=luaZ_openspace(S->L,S->b,size);
  LoadBlock(S,s,size);
  return luaS_newlstr(S->L,s,size-1);		/* remove trailing '\0' */
 }
}

static void LoadCode(LoadState* S, Proto* f)
{
 int n=LoadInt(S);
 f->code=luaM_newvector(S->L,n,Instruction);
 f->sizecode=n;
 LoadVector(S,f->code,n,sizeof(Instruction));
}

static Proto* LoadFunction(LoadState* S, TString* p);

static void LoadConstants(LoadState* S, Proto* f)
{
 int i,n;
 n=LoadInt(S);
 f->k=luaM_newvector(S->L,n,TValue);
 f->sizek=n;
 for (i=0; i<n; i++) setnilvalue(&f->k[i]);
 for (i=0; i<n; i++)
 {
  TValue* o=&f->k[i];
  int t=LoadChar(S);
  switch (t)
  {
   case LUA_TNIL:
   	setnilvalue(o);
	break;
   case LUA_TBOOLEAN:
   	setbvalue(o,LoadChar(S));
	break;
   case LUA_TNUMBER:
	setnvalue(o,LoadNumber(S));
	break;
   case LUA_TSTRING:
	setsvalue2n(S->L,o,LoadString(S));
	break;
   default:
	IF (1, "bad constant");
	break;
  }
 }
 n=LoadInt(S);
 f->p=luaM_newvector(S->L,n,Proto*);
 f->sizep=n;
 for (i=0; i<n; i++) f->p[i]=NULL;
 for (i=0; i<n; i++) f->p[i]=LoadFunction(S,f->source);
}

static void LoadDebug(LoadState* S, Proto* f)
{
 int i,n;
 n=LoadInt(S);
 f->lineinfo=luaM_newvector(S->L,n,int);
 f->sizelineinfo=n;
 LoadVector(S,f->lineinfo,n,sizeof(int));
 n=LoadInt(S);
 f->locvars=luaM_newvector(S->L,n,LocVar);
 f->sizelocvars=n;
 for (i=0; i<n; i++) f->locvars[i].varname=NULL;
 for (i=0; i<n; i++)
 {
  f->locvars[i].varname=LoadString(S);
  f->locvars[i].startpc=LoadInt(S);
  f->locvars[i].endpc=LoadInt(S);
 }
 n=LoadInt(S);
 f->upvalues=luaM_newvector(S->L,n,TString*);
 f->sizeupvalues=n;
 for (i=0; i<n; i++) f->upvalues[i]=NULL;
 for (i=0; i<n; i++) f->upvalues[i]=LoadString(S);
}

static Proto* LoadFunction(LoadState* S, TString* p)
{
 Proto* f=luaF_newproto(S->L);
 setptvalue2s(S->L,S->L->top,f); incr_top(S->L);
 f->source=LoadString(S); if (f->source==NULL) f->source=p;
 f->linedefined=LoadInt(S);
 f->lastlinedefined=LoadInt(S);
 f->nups=LoadByte(S);
 f->numparams=LoadByte(S);
 f->is_vararg=LoadByte(S);
 f->maxstacksize=LoadByte(S);
 LoadCode(S,f);
 LoadConstants(S,f);
 LoadDebug(S,f);
 IF (!luaG_checkcode(f), "bad code");
 S->L->top--;
 return f;
}

static void LoadHeader(LoadState* S)
{
 char h[LUAC_HEADERSIZE];
 char s[LUAC_HEADERSIZE];
 luaU_header(h);
 LoadBlock(S,s,LUAC_HEADERSIZE);
 S->swap=(s[6]!=h[6]); s[6]=h[6];
 IF (memcmp(h,s,LUAC_HEADERSIZE)!=0, "bad header");
}

/*
** load precompiled chunk
*/
Proto* luaU_undump (lua_State* L, ZIO* Z, Mbuffer* buff, const char* name)
{
 LoadState S;
 if (*name=='@' || *name=='=')
  S.name=name+1;
 else if (*name==LUA_SIGNATURE[0])
  S.name="binary string";
 else
  S.name=name;
 S.L=L;
 S.Z=Z;
 S.b=buff;
 LoadHeader(&S);
 return LoadFunction(&S,luaS_newliteral(L,"=?"));
}

/*
* make header
*/
void luaU_header (char* h)
{
 int x=1;
 memcpy(h,LUA_SIGNATURE,sizeof(LUA_SIGNATURE)-1);
 h+=sizeof(LUA_SIGNATURE)-1;
 *h++=(char)LUAC_VERSION;
 *h++=(char)LUAC_FORMAT;
 *h++=(char)*(char*)&x;				/* endianness */
 *h++=(char)sizeof(int);
 *h++=(char)sizeof(size_t);
 *h++=(char)sizeof(Instruction);
 *h++=(char)sizeof(lua_Number);
 *h++=(char)(((lua_Number)0.5)==0);		/* is lua_Number integral? */
}