/************************************************************************
   Auxiliary function for midi-file IO

   Copyright (C) 1994, 1995 by R.Harmsen

   Original date:  26 December 1994. Slight corrections, for
   portability to Linux, under standard C (C89, C90 or C99):
   7 March 2025.
 ***********************************************************************/

#include "stddef.h"
#include "midiutil.h"

/********************************************************************
  Puts the binary number in in the two-byte buffer out, in a
  little-endian fashion: most-significant left (low address),
  less significant more to the right (higher adresses).
  On little-endian processors (Motorola for example) this is
  just a binary copy, but on big-endians like Intel-80x86, it is
  physically a wordwise byte swap.

  Returns out.
 *******************************************************************/
unsigned char *int2twochars (unsigned char *out, int in)
{
   out[1] = (in >>  0) & 0xff;
   out[0] = (in >>  8) & 0xff;

   return out;
}


/********************************************************************
  Same for longs of 4 bytes.
  Returns out.
 *******************************************************************/
unsigned char *long2fourchars (unsigned char *out, long in)
{
   out[3] = (in >>  0) & 0xff;
   out[2] = (in >>  8) & 0xff;
   out[1] = (in >> 16) & 0xff;
   out[0] = (in >> 24) & 0xff;

   return out;
}


/********************************************************************

 *******************************************************************/
int twochars2int (unsigned char *in)
{
   return ((long)in[0] << (8 * 1)) | (long)in[1];
}


/********************************************************************

 *******************************************************************/
long fourchars2long (unsigned char *in)
{
   return ((long)in[0] << (8 * 3)) | ((long)in[1] << (8 * 2)) |
          ((long)in[2] << (8 * 1)) |  (long)in[3];
}


/********************************************************************
  Input is a 32 bit number. Output, in buf, is the same number split
  into 7-bits portions, where all but the rightmost character have
  their bit 7 set. The filled length  of the buffer (min 1, max 5)
  is returned.
  (This variable length count format is used frequently in MIDI-files,
    for delta-time, and the length of the data portion of meta-messages,
    starting with 0xff.)
 *******************************************************************/
int var_length (long in, unsigned char *buf)
{
   unsigned char *b = buf, *p, *e;
   ptrdiff_t cnt;

   *b++ = in & 0x7f;
   while (in >>= 7)
   {
      *b++ = (in & 0x7f) | 0x80;
   }
   cnt = b - buf;

   /* Buffer is now filled the wrong way round: therefore swap it */
   e = buf + (int)((b - buf) >> 1);
   for (p = buf; p < e; p++)
   {
      unsigned char c = *p;
      *p = *--b;
      *b = c;
   }

   return (int)cnt;
}


/********************************************************************
   Conversion the other way round.
 *******************************************************************/
long varlen2long (unsigned char *buf, int *p_bytes_used)
{
   long retval = 0;
   unsigned char *b;

   for (b = buf; *b & 0x80; b++)
   {
      retval += *b & 0x80;
      retval <<= 7;
   }
   retval += *b;

   *p_bytes_used = (b - buf) + 1;
   return retval;
}