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/*
=begin
= Class MultiBitNums
Class of multiple multi-bit data packed in a C string.
The number of bits is fixed to an arbitrary value.
For example, it can accommodate 11-bit integers (but cannot
a mixture of integers with different lengths).
=== Function overview
Integer encoding/decoding (so far only decoding has been implemented):
* Each segment of data is assumed to be multi-bit (fixed-length)
unsigned integer in network byte order (big endian).
* Note: integers of the system does not have to be big-endian (Only
the binary data is interpreted as unsigned big-endian).
===Class Methods
---MultiBitNums.new( str, nbit [, nint] )
Creates a new object from a binary data (string) containing multi-bit
segments.
ARGUMENTS
* str (String): binary data containing multi-bit data
* nbit (Integer): length in bits of each segments contained in str
* nint (Integer, can be omitted): number of nbit-bit data in str. If
omitted, derived automatically from the length of str.
RETURN VALUE
* a MultiBitNums object
ERRORS
* exception is raised if nint is too large for the length of str.
===Instance Methods
---to_int32str
Converts into a string containing binary data of 32-bit integers
of the system. Useful with NArray.
ARGUMENTS
(none)
RETURN VALUE
* a String (Its binary expression depends on the integer
expression of the system).
ERRORS
* exception is raised if nbit (see ((<MultiBitNums.new>))) is greater than 32.
EXAMPLE
mb = MultiBitNums.new(str, nbits)
require "narray" # download it from RAA at www.ruby-lang.org
ary = NArray.to_na( mb, "int" ) # the data is read into a NArray ary
=end
*/
/* ruby.h for rb_raise */
#include "ruby.h"
/* sys/typed.h : should be configured whether the system has this or not */
#include <sys/types.h>
#ifndef HAVE_INT32_T
typedef long int32_t;
#endif
#ifndef RSTRING_PTR
#define RSTRNG_PTR(s) (RSTRING(s)->ptr)
#endif
#ifndef RSTRING_LEN
#define RSTRING_LEN(a) (RSTRING(a)->len)
#endif
static VALUE mNumRu;
static VALUE cMultiBitNums;
struct MultiBitNums {
unsigned char *ptr; /* holds data */
long len_ptr; /* length of ptr (in bytes) */
int nbit; /* length in bits of each integer in str */
long nint; /* number of data contained (<= len_str*8/static) */
};
static void
mltbtnm_free(struct MultiBitNums *mbs)
{
xfree(mbs->ptr);
mbs->len_ptr = 0;
mbs->nbit = 0;
mbs->nint = 0;
xfree(mbs);
}
static VALUE
mltbtnm_s_new(int argc, VALUE *argv, VALUE klass)
{
/* [ actual arguments --> */
VALUE str;
VALUE nbit;
VALUE nint; /* can be omitted */
/* <-- actual arguments ] */
struct MultiBitNums *mbs;
long c_nint, nintmax;
if (argc < 2 || argc >3){
rb_raise(rb_eArgError,
"Usage: MultiBitNums.new(str, nbit [,nint]) -- nint is omittable");
}
str = argv[0];
nbit = argv[1];
mbs = ALLOC(struct MultiBitNums);
mbs->nbit = NUM2INT(nbit);
mbs->len_ptr = RSTRING_LEN(str);
mbs->ptr = ALLOC_N(char, mbs->len_ptr);
memcpy( mbs->ptr, RSTRING_PTR(str), mbs->len_ptr);
nintmax = ((mbs->len_ptr*8.0)/mbs->nbit + 0.1);
if ( argc != 3 ){
mbs->nint = nintmax;
} else {
nint = argv[2];
c_nint = NUM2LONG(nint);
if (c_nint > nintmax) {
rb_raise(rb_eArgError, "nint is too long");
} else {
mbs->nint = c_nint;
}
}
return Data_Wrap_Struct(klass, 0, mltbtnm_free, mbs);
}
static int32_t *
mltbtnm_read_int32(unsigned char *ptr, long len_ptr, int nbit, long *nint)
/*
unsigned char *ptr // holds data
long len_ptr // length of ptr (in bytes)
int nbit // number of bits
long *nint // number of integers to read (if <= 0, determined
// from len_ptr)
*/
{
int32_t *result;
long nintmax, i, n0, n1, k0, k1, w;
long j, j2, nm;
unsigned char cn[4],mk0,mb;
nintmax = ((len_ptr*8.0)/nbit + 0.1);
/* double was used here to prevent overflow. 0.1 is for round errs */
if ( *nint <= 0 ){
*nint = nintmax;
} else if (*nint > nintmax) {
rb_raise(rb_eArgError, "*nint is too long");
}
if ( nbit > 32 ){
rb_raise(rb_eArgError, "nbit must be 32 or less");
}
result = (int32_t *) malloc((*nint)*sizeof(int32_t));
for(i=0; i<(*nint); i++){
w = (i % 8) * nbit;
n0 = (i / 8) * nbit + (w / 8); /* overflow-free i*nbit/8 */
k0 = w % 8; /* == (i*nbit) % 8 */
w = k0 + nbit - 1;
n1 = n0 + (w/8);
k1 = w % 8;
mk0 = 0xff >> k0; /* to mask 0..k0-1 bits */
for(j=n1; j>= n1-3; j--){
j2 = j - n1 + 3; /* 3,2,1,0 */
mb = (nm = (8-nbit+(3-j2)*8)) > 0 ? (0xff>>nm): 0xff;
if (j > n0) {
cn[j2] = ptr[j] >> (7-k1);
if (j != n0+1){
cn[j2] += ptr[j-1] << (k1+1);
} else {
cn[j2] += (ptr[j-1] & mk0) << (k1+1);
}
cn[j2] &= mb;
} else if (j == n0) {
cn[j2] = (ptr[j] & mk0) >> (7-k1);
cn[j2] &= mb;
} else {
/* j < n0 --> blank */
cn[j2] = 0x00;
}
}
result[i] = 0x1000000*cn[0] + 0x10000*cn[1] + 0x100*cn[2] + cn[3];
}
return(result);
}
static VALUE
mltbtnm_to_int32str(VALUE obj){
struct MultiBitNums *mbs;
int32_t *buff;
Data_Get_Struct(obj, struct MultiBitNums, mbs);
buff = mltbtnm_read_int32(mbs->ptr, mbs->len_ptr, mbs->nbit, &(mbs->nint));
return rb_str_new( (char *) buff, mbs->nint * sizeof(int32_t) );
}
void
Init_multibitnums()
{
extern VALUE ruby_class;
mNumRu = rb_define_module("NumRu");
cMultiBitNums = rb_define_class_under(mNumRu, "MultiBitNums", rb_cObject);
rb_define_singleton_method(cMultiBitNums,"new",mltbtnm_s_new,-1);
rb_define_method(cMultiBitNums, "to_int32str", mltbtnm_to_int32str,0);
}
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