/*
** {======================================================
** Library for packing/unpacking structures.
** $Id: struct.c,v 1.4 2012/07/04 18:54:29 roberto Exp $
** See Copyright Notice at the end of this file
**
** Small changes were made by Hadriel Kaplan - those changes 
** are in the Public Domain.
**
** Some changes are based on a patch to struct.h from
** Flemming Madsen, from here:
** http://lua-users.org/lists/lua-l/2009-10/msg00572.html
** In particular, these changes from him:
** -Can handle 'long long' integers (i8 / I8); though they're converted to doubles
** -Can insert/specify padding anywhere in a struct. ('X' eg. when a string is following a union)
** -Can report current offset in both pack and unpack ('=')
** -Can mask out return values when you only want to calculate sizes or unmarshal pascal-style strings. '(' & ')'
**
** Changes I made:
** -Added support for Int64/UIn64 being packed/unpacked, using 'e'/'E'
** -Made it follow Wireshark's conventions so we could get API docs
** =======================================================
*/
/*
** Valid formats:
** > - big endian
** < - little endian
** ![num] - alignment
** x[num]   - pad num bytes, default 1
** X[num]   - pad to num align, default MAXALIGN
**
** Following are system-dependent sizes:
** b/B - signed/unsigned byte
** h/H - signed/unsigned short
** i/I - signed/unsigned int
** l/L - signed/unsigned long
** f - float
** d - double
** T   - size_t
**
** Following are system-independent sizes:
** in/In - signed/unsigned integer of size `n' bytes
          Note: unpack of i/I is done to a Lua_number, typically a double,
          so unpacking a 64-bit field (i8/I8) will lose precision.
          Use e/E to unpack into a Wireshark Int64/UInt64 object/userdata instead.
** e/E - signed/unsigned eight-byte Integer (64bits, long long), to/from Int64/UInt64 object
** cn - sequence of `n' chars (from/to a string); when packing, n==0 means
        the whole string; when unpacking, n==0 means use the previous
        read number as the string length
** s - zero-terminated string
** ' ' - ignored
** '(' ')'  - stop assigning items. ')' start assigning (padding when packing)
** '='      - return current position / offset
*/


#include <assert.h>
#include <ctype.h>
#include <limits.h>
#include <stddef.h>
#include <string.h>

#include <stdio.h>

#include "config.h"

#include "wslua.h"

    /* WSLUA_MODULE Struct Binary encode/decode support */

/* TODO: figure out a way for wslua Module's to have (possibly long) description text */

/* The following line is here so that make-reg.pl does the right thing.  This 'Struct' class
  isn't really a class, so it doesn't have the checkStruct/pushStruct/etc. functions
  the following macro would generate; but it does need to be registered and such. 
  WSLUA_CLASS_DEFINE_BASE(Struct,NOP,NOP,0); 
  */

/* basic integer type - yes this is system-specific size - it's meant to be */
#if !defined(STRUCT_INT)
#define STRUCT_INT  long
#endif

typedef STRUCT_INT Inttype;

/* corresponding unsigned version */
typedef unsigned STRUCT_INT Uinttype;

/* maximum size (in bytes) for integral types */
#define MAXINTSIZE	32

/* is 'x' a power of 2? */
#define isp2(x)		((x) > 0 && ((x) & ((x) - 1)) == 0)

/* dummy structure to get padding/alignment requirements */
struct cD {
  gchar c;
  gdouble d;
};


#define PADDING		(sizeof(struct cD) - sizeof(gdouble))
#define MAXALIGN  	(PADDING > sizeof(int) ? PADDING : sizeof(int))


/* endian options */
#define BIG	0
#define LITTLE	1

/* trick to determine native endianess of system */
static union {
  int dummy;
  gchar endian;
} const native = {1};

/* settings info */
typedef struct Header {
  int endian;
  int align;
  gboolean noassign;
} Header;

/* For options that take a number argument, gets the number  */
static int getnum (const gchar **fmt, int df) {
  if (!isdigit(**fmt))  /* no number? */
    return df;  /* return default value */
  else {
    int a = 0;
    do {
      a = a*10 + *((*fmt)++) - '0';
    } while (isdigit(**fmt));
    return a;
  }
}


#define defaultoptions(h)	((h)->endian = native.endian, (h)->align = 1, (h)->noassign = FALSE)


/* gets size (number of bytes) for a given type */
static size_t optsize (lua_State *L, gchar opt, const gchar **fmt) {
  switch (opt) {
    case 'B': case 'b': return sizeof(gchar);
    case 'H': case 'h': return sizeof(gshort);
    case 'L': case 'l': return sizeof(glong);
    case 'E': case 'e': return sizeof(gint64);
    case 'T': return sizeof(size_t);
    case 'f': return sizeof(gfloat);
    case 'd': return sizeof(gdouble);
    case 'x': return getnum(fmt, 1);
    case 'X': return getnum(fmt, MAXALIGN);
    case 'c': return getnum(fmt, 1);
    case 'i': case 'I': {
      int sz = getnum(fmt, sizeof(int));
      if (sz > MAXINTSIZE)
        luaL_error(L, "integral size %d is larger than limit of %d",
                       sz, MAXINTSIZE);
      return sz;
    }
    case 's': case ' ':
    case '<': case '>':
    case '(': case ')':
    case '!': case '=':
              return 0;  /* these cases do not have a size */
    default: {
      const gchar *msg = lua_pushfstring(L, "invalid format option [%c]", opt);
      return luaL_argerror(L, 1, msg);
    }
  }
}


/*
** return number of bytes needed to align an element of size 'size'
** at current position 'len'
*/
static int gettoalign (size_t len, Header *h, int opt, size_t size) {
  if (size == 0 || opt == 'c' || opt == 's') return 0;
  if (size > (size_t)h->align)
    size = h->align;  /* respect max. alignment */
  return (int)((size - (len & (size - 1))) & (size - 1));
}


/*
** options to control endianess and alignment settings
*/
static void controloptions (lua_State *L, int opt, const gchar **fmt,
                            Header *h) {
  switch (opt) {
    case ' ': return;  /* ignore white spaces */
    case '>': h->endian = BIG; return;
    case '<': h->endian = LITTLE; return;
    case '(': h->noassign = TRUE; return;
    case ')': h->noassign = FALSE; return;
    case '!': {
      int a = getnum(fmt, MAXALIGN);
      if (!isp2(a))
        luaL_error(L, "alignment %d is not a power of 2", a);
      h->align = a;
      return;
    }
    default: {
      const char *msg = lua_pushfstring(L, "invalid format option '%c'", opt);
      luaL_argerror(L, 1, msg);
    }
  }
}

/* Encodes a Lua number as an integer of given size and endiannes into a string struct */
static void putinteger (lua_State *L, luaL_Buffer *b, int arg, int endian,
                        int size) {
  lua_Number n = luaL_checknumber(L, arg);
  /* this one's not system dependent size - it's a long long */
  gint64 value;
  gchar buff[MAXINTSIZE];
  if (n < 0)
    value = (guint64)(gint64)n;
  else
    value = (guint64)n;
  if (endian == LITTLE) {
    int i;
    for (i = 0; i < size; i++) {
      buff[i] = (value & 0xff);
      value >>= 8;
    }
  }
  else {
    int i;
    for (i = size - 1; i >= 0; i--) {
      buff[i] = (value & 0xff);
      value >>= 8;
    }
  }
  luaL_addlstring(b, buff, size);
}

/* corrects endiannes - usually done by other functions themselves, but is 
 * used for float/doubles, since on some platforms they're endian'ed as well
 */
static void correctbytes (gchar *b, int size, int endian) {
  if (endian != native.endian) {
    int i = 0;
    while (i < --size) {
      gchar temp = b[i];
      b[i++] = b[size];
      b[size] = temp;
    }
  }
}


WSLUA_CONSTRUCTOR Struct_pack (lua_State *L) {
  /* Returns a string containing the values arg1, arg2, etc. packed/encoded according to the format string. */
#define WSLUA_ARG_Struct_unpack_FORMAT 1 /* The format string */
#define WSLUA_ARG_Struct_unpack_STRUCT 2 /* One or more Lua value(s) to encode, based on the given format. */
  luaL_Buffer b;
  const char *fmt = luaL_checkstring(L, WSLUA_ARG_Struct_unpack_FORMAT);
  Header h;
  int poscnt = 0;
  int posBuf[10];
  int arg = 2;
  size_t totalsize = 0;
  defaultoptions(&h);
  lua_pushnil(L);  /* mark to separate arguments from string buffer */
  luaL_buffinit(L, &b);
  while (*fmt != '\0') {
    int opt = *fmt++;
    size_t size = optsize(L, opt, &fmt);
    int toalign = gettoalign(totalsize, &h, opt, size);
    totalsize += toalign;
    while (toalign-- > 0) luaL_addchar(&b, '\0');
    if (opt == 'X') size = 0; /* 'X' is about alignment, not size */
    if (h.noassign && size) opt = 'x'; /* for pack, "(i4)" is the same as "x4" */
    switch (opt) {
      case 'b': case 'B': case 'h': case 'H':
      case 'l': case 'L': case 'T': case 'i': case 'I': {  /* integer types */
        putinteger(L, &b, arg++, h.endian, (int)size);
        break;
      }
      case 'e': {
        Int64_pack(L, &b, arg++, h.endian == LITTLE);
        break;
      }
      case 'E': {
        UInt64_pack(L, &b, arg++, h.endian == LITTLE);
        break;
      }
      case 'x': case 'X': {
        size_t len = size;
        while (len-- > 0)
          luaL_addchar(&b, '\0');
        break;
      }
      case 'f': {
        gfloat f = (gfloat)luaL_checknumber(L, arg++);
        correctbytes((gchar *)&f, (int)size, h.endian);
        luaL_addlstring(&b, (gchar *)&f, size);
        break;
      }
      case 'd': {
        gdouble d = luaL_checknumber(L, arg++);
        correctbytes((gchar *)&d, (int)size, h.endian);
        luaL_addlstring(&b, (gchar *)&d, size);
        break;
      }
      case 'c': case 's': {
        size_t l;
        const gchar *s = luaL_checklstring(L, arg++, &l);
        if (size == 0) size = l;
        luaL_argcheck(L, l >= (size_t)size, arg, "string too short");
        luaL_addlstring(&b, s, size);
        if (opt == 's') {
          luaL_addchar(&b, '\0');  /* add zero at the end */
          size++;
        }
        break;
      }
      case '=': {
        if (poscnt < (int)(sizeof(posBuf)/sizeof(posBuf[0])))
          posBuf[poscnt++] = (int)totalsize + 1;
        break;
      }
      default: controloptions(L, opt, &fmt, &h);
    }
    totalsize += size;
  }
  luaL_pushresult(&b);
  for (arg = 0; arg < poscnt; arg++)
    lua_pushinteger(L, posBuf[arg]);
  return poscnt + 1;
}

/* Decodes an integer from a string struct into a Lua number, based on 
 * given endianess and size. If the integer type is signed, this makes
 * the Lua number be +/- correctly as well.
 */
static lua_Number getinteger (const gchar *buff, int endian,
                        int issigned, int size) {
  Uinttype l = 0;
  int i;
  if (endian == BIG) {
    for (i = 0; i < size; i++) {
      l <<= 8;
      l |= (Uinttype)(guchar)buff[i];
    }
  }
  else {
    for (i = size - 1; i >= 0; i--) {
      l <<= 8;
      l |= (Uinttype)(guchar)buff[i];
    }
  }
  if (!issigned)
    return (lua_Number)l;
  else {  /* signed format */
    Uinttype mask = (Uinttype)(~((Uinttype)0)) << (size*8 - 1);
    if (l & mask)  /* negative value? */
      l |= mask;  /* signal extension */
    return (lua_Number)(Inttype)l;
  }
}

#define b_pushnumber(n) { if (!h.noassign) lua_pushnumber(L, (lua_Number)(n)); }

WSLUA_CONSTRUCTOR Struct_unpack (lua_State *L) {
  /*  Unpacks/decodes multiple Lua values from a given struct-like binary Lua string. 
      The number of returned values depends on the format given, plus an addtional value of the position where it stopped reading is returned. */
#define WSLUA_ARG_Struct_unpack_FORMAT 1 /* The format string */
#define WSLUA_ARG_Struct_unpack_STRUCT 2 /* The binary Lua string to unpack */
#define WSLUA_OPTARG_Struct_unpack_BEGIN  3 /* The position to begin reading from (default=1) */
  Header h;
  const char *fmt = luaL_checkstring(L, WSLUA_ARG_Struct_unpack_FORMAT);
  size_t ld;
  const char *data = luaL_checklstring(L, WSLUA_ARG_Struct_unpack_STRUCT, &ld);
  size_t pos = luaL_optinteger(L, WSLUA_OPTARG_Struct_unpack_BEGIN, 1) - 1;
  defaultoptions(&h);
  lua_settop(L, 2);
  while (*fmt) {
    int opt = *fmt++;
    size_t size = optsize(L, opt, &fmt);
    pos += gettoalign(pos, &h, opt, size);
    luaL_argcheck(L, pos+size <= ld, 2, "data string too short");

    if (opt == 'X') size = 0;
    if (h.noassign && size > 0) {
      /* if we're not assigning, and the opt type has a size, then loop again */
      /* this will not be the case for controloptions, 'c0', 's', and '=' */
      pos += size;
      continue;
    }

    luaL_checkstack(L, 1, "too many results");
    switch (opt) {
      case 'b': case 'B': case 'h': case 'H':
      case 'l': case 'L': case 'T': case 'i':  case 'I': {  /* integer types */
        int issigned = islower(opt);
        lua_Number res = getinteger(data+pos, h.endian, issigned, (int)size);
        lua_pushnumber(L, res);
        break;
      }
      case 'e': {
        Int64_unpack(L, data+pos, h.endian == LITTLE);
        break;
      }
      case 'E': {
        UInt64_unpack(L, data+pos, h.endian == LITTLE);
        break;
      }
      case 'x': case 'X': {
        break;
      }
      case 'f': {
        gfloat f;
        memcpy(&f, data+pos, size);
        correctbytes((gchar *)&f, sizeof(f), h.endian);
        lua_pushnumber(L, f);
        break;
      }
      case 'd': {
        gdouble d;
        memcpy(&d, data+pos, size);
        correctbytes((gchar *)&d, sizeof(d), h.endian);
        lua_pushnumber(L, d);
        break;
      }
      case 'c': {
        if (size == 0) {
          if (!lua_isnumber(L, -1))
            luaL_error(L, "format `c0' needs a previous size");
          size = lua_tonumber(L, -1);
          lua_pop(L, 1);
          luaL_argcheck(L, pos+size <= ld, 2, "data string too short");
        }
        if (!h.noassign)
          lua_pushlstring(L, data+pos, size);
        break;
      }
      case 's': {
        const gchar *e = (const char *)memchr(data+pos, '\0', ld - pos);
        if (e == NULL)
          luaL_error(L, "unfinished string in data");
        size = (e - (data+pos)) + 1;
        if (!h.noassign)
          lua_pushlstring(L, data+pos, size - 1);
        break;
      }
      case '=': {
        lua_pushinteger(L, pos + 1);
        break;
      }
      default: controloptions(L, opt, &fmt, &h);
    }
    pos += size;
  }
  lua_pushinteger(L, pos + 1);
  return lua_gettop(L) - 2;
}


WSLUA_CONSTRUCTOR Struct_size (lua_State *L) {
  /* Returns the length of the binary string struct that would be consumed/handled by the given format string. */
  Header h;
  const gchar *fmt = luaL_checkstring(L, 1);
  size_t pos = 0;
  defaultoptions(&h);
  while (*fmt) {
    int opt = *fmt++;
    size_t size = optsize(L, opt, &fmt);
    pos += gettoalign(pos, &h, opt, size);
    if (opt == 's')
      luaL_argerror(L, 1, "option 's' has no fixed size");
    else if (opt == 'c' && size == 0)
      luaL_argerror(L, 1, "option 'c0' has no fixed size");
    if (!isalnum(opt))
      controloptions(L, opt, &fmt, &h);
    pos += size;
  }
  lua_pushinteger(L, pos);
  return 1;
}

/* }====================================================== */

/* Gets registered as metamethod automatically by WSLUA_REGISTER_CLASS/META */
static int Struct__gc(lua_State* L _U_) {
    return 0;
}

static const luaL_Reg Struct_methods[] = {
  {"pack", Struct_pack},
  {"unpack", Struct_unpack},
  {"size", Struct_size},
  {NULL, NULL}
};

static const luaL_Reg Struct_meta[] = {
    { NULL, NULL }
};

LUALIB_API int Struct_register(lua_State* L) {
    WSLUA_REGISTER_CLASS(Struct);
    return 0;
}


/******************************************************************************
* Copyright (C) 2010-2012 Lua.org, PUC-Rio.  All rights reserved.
*
* Permission is hereby granted, free of charge, to any person obtaining
* a copy of this software and associated documentation files (the
* "Software"), to deal in the Software without restriction, including
* without limitation the rights to use, copy, modify, merge, publish,
* distribute, sublicense, and/or sell copies of the Software, and to
* permit persons to whom the Software is furnished to do so, subject to
* the following conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
******************************************************************************/