/*
** Library for packing/unpacking structures.
**
** Valid formats:
** x - pading
** b/B - signed/unsigned byte
** h/H - signed/unsigned short
** l/L - signed/unsigned long
** i/In - signed/unsigned integer with size `n‘ (default is size of int)
** 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
** f - float
** d - doulbe
*/
#include <ctype.h>
#include <string.h>
#include "lua.h"
#include "lauxlib.h"
/* dummy structure to get alignment requirements */
struct cD {
char c;
double d;
};
static int getmaxalign (void) {
int ma = sizeof(int);
int e = sizeof(struct cD) - sizeof(double);
if (ma < e) ma = e;
return ma;
}
static int getendianess (const char **s, int *native_out) {
int endian; /* 0 = little; 1 = big */
int native = 1;
if (*(char *)&native == 1)
native = 0;
if (**s == ‘>‘) {
endian = 1;
(*s)++;
}
else if (**s == ‘<‘) {
endian = 0;
(*s)++;
}
else
endian = native;
*native_out = native;
return endian;
}
static int getnum (const char **fmt, int df) {
if (!isdigit(**fmt))
return df; /* no number */
else {
int a = 0;
do {
a = a*10 + *((*fmt)++) - ‘0‘;
} while (isdigit(**fmt));
return a;
}
}
static int optsize (char opt, const char **fmt) {
switch (opt) {
case ‘B‘: case ‘b‘: return 1;
case ‘H‘: case ‘h‘: return 2;
case ‘L‘: case ‘l‘: return 4;
case ‘f‘: return sizeof(float);
case ‘d‘: return sizeof(double);
case ‘x‘: return 1;
case ‘i‘: return getnum(fmt, sizeof(int));
case ‘c‘: return getnum(fmt, 1);
case ‘s‘: return 0;
default: return 1; /* invalid code */
}
}
static int getalign (const char **fmt) {
if (**fmt != ‘!‘) return 1; /* no alignment */
else {
(*fmt)++;
return getnum(fmt, getmaxalign());
}
}
static int gettoalign (lua_State *L, int align, int opt, int size) {
int toalign = (opt == ‘c‘ || opt == ‘s‘) ? 1 : size;
if (toalign > align) toalign = align;
if (toalign == 0 || (toalign & (toalign - 1)) != 0)
luaL_error(L, "alignment must be power of 2");
return toalign;
}
static void putinteger (lua_State *L, luaL_Buffer *b, int arg, int endian,
int size) {
unsigned char buff[sizeof(long)];
lua_Number n = luaL_checknumber(L, arg);
unsigned long value;
unsigned char *s;
int inc, i;
if (n < 0) {
value = (unsigned long)(-n);
value = (~value) + 1; /* 2‘s complement */
}
else
value = (unsigned long)n;
if (endian == 0) {
inc = 1;
s = buff;
}
else {
inc = -1;
s = buff+(size-1);
}
for (i=0; i<size; i++) {
*s = (unsigned char)(value & 0xff);
s += inc;
value >>= 8;
}
luaL_addlstring(b, (char *)buff, size);
}
static void invertbytes (char *b, int size) {
int i = 0;
while (i < --size) {
char temp = b[i];
b[i++] = b[size];
b[size] = temp;
}
}
static void invalidformat (lua_State *L, char c) {
const char *msg = lua_pushfstring(L, "invalid format option [%c]", c);
luaL_argerror(L, 1, msg);
}
static int b_size (lua_State *L) {
int native;
const char *fmt = luaL_checkstring(L, 1);
int align;
int totalsize = 0;
getendianess(&fmt, &native);
align = getalign(&fmt);
while (*fmt) {
int opt = *fmt++;
int size = optsize(opt, &fmt);
int toalign = gettoalign(L, align, opt, size);
if (size == 0)
luaL_error(L, "options `c0‘ - `s‘ have undefined sizes");
totalsize += toalign - 1;
totalsize -= totalsize&(toalign-1);
totalsize += size;
}
lua_pushnumber(L, totalsize);
return 1;
}
static int b_pack (lua_State *L) {
luaL_Buffer b;
int native;
const char *fmt = luaL_checkstring(L, 1);
int endian = getendianess(&fmt, &native);
int align = getalign(&fmt);
int arg = 2;
int totalsize = 0;
lua_pushnil(L); /* mark to separate arguments from string buffer */
luaL_buffinit(L, &b);
for (; *fmt; arg++) {
int opt = *fmt++;
int size = optsize(opt, &fmt);
int toalign = gettoalign(L, align, opt, size);
while ((totalsize&(toalign-1)) != 0) {
//luaL_putchar(&b, ‘\0‘);
luaL_addchar(&b, ‘\0‘);
totalsize++;
}
switch (opt) {
case ‘ ‘: break; /* ignore white spaces */
case ‘b‘: case ‘B‘: case ‘h‘: case ‘H‘:
case ‘l‘: case ‘L‘: case ‘i‘: case ‘I‘: { /* integer types */
putinteger(L, &b, arg, endian, size);
break;
}
case ‘x‘: {
arg--; /* undo increment */
//luaL_putchar(&b, ‘\0‘);
luaL_addchar(&b, ‘\0‘);
break;
}
case ‘f‘: {
float f = (float)luaL_checknumber(L, arg);
if (endian != native) invertbytes((char *)&f, size);
luaL_addlstring(&b, (char *)&f, size);
break;
}
case ‘d‘: {
double d = luaL_checknumber(L, arg);
if (endian != native) invertbytes((char *)&d, size);
luaL_addlstring(&b, (char *)&d, size);
break;
}
case ‘c‘: case ‘s‘: {
size_t l;
const char *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_putchar(&b, ‘\0‘); /* add zero at the end */
luaL_addchar(&b, ‘\0‘);
size++;
}
break;
}
default: invalidformat(L, opt);
}
totalsize += size;
}
luaL_pushresult(&b);
return 1;
}
static void getinteger (lua_State *L, const char *buff, int endian,
int withsign, int size) {
unsigned long l = 0;
int i, inc;
if (endian == 1)
inc = 1;
else {
inc = -1;
buff += size-1;
}
for (i=0; i<size; i++) {
l = (l<<8) + (unsigned char)(*buff);
buff += inc;
}
if (withsign) { /* signed format? */
unsigned long mask = ~(0UL) << (size*8 - 1);
if (l & mask) { /* negative value? */
l = (l^~(mask<<1)) + 1;
lua_pushnumber(L, -(lua_Number)l);
return;
}
}
lua_pushnumber(L, l);
}
static int b_unpack (lua_State *L) {
int native;
const char *fmt = luaL_checkstring(L, 1);
size_t ld;
int pos, align, endian;
const char *data;
if(lua_isuserdata(L, 2)) {
data = (const char*)lua_touserdata(L, 2);
ld = (size_t)luaL_checkinteger(L, 3);
pos = 0;
} else {
data = luaL_checklstring(L, 2, &ld);
//pos = luaL_optint(L, 3, 1) - 1;
pos = luaL_optinteger(L, 3, 1) - 1;
}
endian = getendianess(&fmt, &native);
align = getalign(&fmt);
lua_settop(L, 2);
while (*fmt) {
int opt = *fmt++;
int size = optsize(opt, &fmt);
int toalign = gettoalign(L, align, opt, size);
pos += toalign - 1;
pos -= pos&(toalign-1);
luaL_argcheck(L, pos+size <= (int)ld, 2, "data string too short");
switch (opt) {
case ‘ ‘: break; /* ignore white spaces */
case ‘b‘: case ‘B‘: case ‘h‘: case ‘H‘:
case ‘l‘: case ‘L‘: case ‘i‘: case ‘I‘: { /* integer types */
int withsign = islower(opt);
getinteger(L, data+pos, endian, withsign, size);
break;
}
case ‘x‘: {
break;
}
case ‘f‘: {
float f;
memcpy(&f, data+pos, size);
if (endian != native) invertbytes((char *)&f, sizeof(f));
lua_pushnumber(L, f);
break;
}
case ‘d‘: {
double d;
memcpy(&d, data+pos, size);
if (endian != native) invertbytes((char *)&d, sizeof(d));
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 <= (int)ld, 2, "data string too short");
}
lua_pushlstring(L, data+pos, size);
break;
}
case ‘s‘: {
const char *e = (const char *)memchr(data+pos, ‘\0‘, ld - pos);
if (e == NULL)
luaL_error(L, "unfinished string in data");
size = (e - (data+pos)) + 1;
lua_pushlstring(L, data+pos, size - 1);
break;
}
default: invalidformat(L, opt);
}
pos += size;
}
lua_pushnumber(L, pos + 1);
return lua_gettop(L) - 2;
}
static const struct luaL_Reg thislib[] = {
{"pack", b_pack},
{"unpack", b_unpack},
{"size", b_size},
{NULL, NULL}
};
LUALIB_API int luaopen_alien_struct (lua_State *L) {
lua_getglobal(L, "alien");
if(lua_isnil(L, -1)) {
lua_newtable(L);
lua_pushvalue(L, -1);
lua_setglobal(L, "alien");
}
lua_newtable(L);
lua_pushvalue(L, -1);
lua_setfield(L, -3, "struct");
luaL_newlib(L, thislib);
return 1;
}