imd.C

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#include "imd.h"
#include "vmdsock.h"
#include <string.h>
#include <errno.h>
#include <stdlib.h>

typedef struct {
  int32 type;
  int32 length;
} IMDheader;

#define HEADERSIZE 8
#define IMDVERSION 2

static void swap4(char *data, int ndata) {
  int i;
  char *dataptr;
  char b0, b1;

  dataptr = data;
  for (i=0; i<ndata; i+=4) {
    b0 = dataptr[0];
    b1 = dataptr[1];
    dataptr[0] = dataptr[3];
    dataptr[1] = dataptr[2];
    dataptr[2] = b1;
    dataptr[3] = b0;
    dataptr += 4;
  }
}

typedef union {
  int32 i;
  struct {
    unsigned int highest : 8;
    unsigned int high    : 8;
    unsigned int low     : 8;
    unsigned int lowest  : 8;
  } b;
} netint;

static int32 imd_htonl(int32 h) {
  netint n;
  n.b.highest = h >> 24;
  n.b.high    = h >> 16;
  n.b.low     = h >> 8;
  n.b.lowest  = h;
  return n.i;
}

static int32 imd_ntohl(int32 n) {
  netint u;
  u.i = n;
  return (u.b.highest << 24 | u.b.high << 16 | u.b.low << 8 | u.b.lowest);
}

static void fill_header(IMDheader *header, IMDType type, int32 length) {
  header->type = imd_htonl((int32)type);
  header->length = imd_htonl(length);
}

static void swap_header(IMDheader *header) {
  header->type = imd_ntohl(header->type);
  header->length= imd_ntohl(header->length);
}

static int32 imd_readn(void *s, char *ptr, int32 n) {
  int32 nleft;
  int32 nread;
 
  nleft = n;
  while (nleft > 0) {
    if ((nread = vmdsock_read(s, ptr, nleft)) < 0) {
      if (errno == EINTR)
        nread = 0;         /* and call read() again */
      else
        return -1;
    } else if (nread == 0)
      break;               /* EOF */
    nleft -= nread;
    ptr += nread;
  }
  return n-nleft;
}

static int32 imd_writen(void *s, const char *ptr, int32 n) {
  int32 nleft;
  int32 nwritten;

  nleft = n;
  while (nleft > 0) {
    if ((nwritten = vmdsock_write(s, ptr, nleft)) <= 0) {
      if (errno == EINTR)
        nwritten = 0;
      else
        return -1;
    }
    nleft -= nwritten;
    ptr += nwritten;
  }
  return n;
}
 

int imd_disconnect(void *s) {
  IMDheader header;
  fill_header(&header, IMD_DISCONNECT, 0);
  return (imd_writen(s, (char *)&header, HEADERSIZE) != HEADERSIZE);
}

int imd_pause(void *s) {
  IMDheader header;
  fill_header(&header, IMD_PAUSE, 0);
  return (imd_writen(s, (char *)&header, HEADERSIZE) != HEADERSIZE);
}

int imd_kill(void *s) {
  IMDheader header;
  fill_header(&header, IMD_KILL, 0);
  return (imd_writen(s, (char *)&header, HEADERSIZE) != HEADERSIZE);
}

static int imd_go(void *s) {
  IMDheader header;
  fill_header(&header, IMD_GO, 0);
  return (imd_writen(s, (char *)&header, HEADERSIZE) != HEADERSIZE);
}


int imd_handshake(void *s) {
  IMDheader header;
  fill_header(&header, IMD_HANDSHAKE, 1);
  header.length = IMDVERSION;   // Not byteswapped!
  return (imd_writen(s, (char *)&header, HEADERSIZE) != HEADERSIZE);
}

int imd_trate(void *s, int32 rate) {
  IMDheader header;
  fill_header(&header, IMD_TRATE, rate);
  return (imd_writen(s, (char *)&header, HEADERSIZE) != HEADERSIZE);
}

// Data methods

int imd_send_mdcomm(void *s,int32 n,const int32 *indices,const float *forces) {
  int32 size = HEADERSIZE+16*n;
  char *buf = new char[size]; 
  fill_header((IMDheader *)buf, IMD_MDCOMM, n);
  memcpy((void *)(buf+HEADERSIZE), (const void *)indices, 4*n);
  memcpy((void *)(buf+HEADERSIZE+4*n), (const void *)forces, 12*n);
  int rc = (imd_writen(s, buf, size) != size);
  delete [] buf;
  return rc;
}

int imd_send_energies(void *s, const IMDEnergies *energies) {
  int32 size = HEADERSIZE+sizeof(IMDEnergies);
  char *buf = new char[size];
  fill_header((IMDheader *)buf, IMD_ENERGIES, 1);
  memcpy((void *)(buf+HEADERSIZE), (const void *)energies, sizeof(IMDEnergies));
  int rc = (imd_writen(s, buf, size) != size);
  delete [] buf;
  return rc;
}

int imd_send_fcoords(void *s, int32 n, const float *coords) {
  int32 size = HEADERSIZE+12*n;
  char *buf = new char[size];
  fill_header((IMDheader *)buf, IMD_FCOORDS, n);
  memcpy((void *)(buf+HEADERSIZE), (const void *)coords, 12*n);
  int rc = (imd_writen(s, buf, size) != size);
  delete [] buf;
  return rc;
}

// The IMD receive functions

// The IMD receive functions
IMDType imd_recv_header_nolengthswap(void *s, int32 *length) {
  IMDheader header;
  if (imd_readn(s, (char *)&header, HEADERSIZE) != HEADERSIZE)
    return IMD_IOERROR;
  *length = header.length;
  swap_header(&header);
  return IMDType(header.type);
}

int imd_recv_handshake(void *s) {
  // Wait 5 seconds for the handshake to come
  if (vmdsock_selread(s, 5) != 1) return -1;

  // Check to see that a valid handshake was received
  int32 buf;
  IMDType type = imd_recv_header_nolengthswap(s, &buf);
  if (type != IMD_HANDSHAKE) return -1;

  // Check its endianness, as well as the IMD version.
  if (buf == IMDVERSION) {
    if (!imd_go(s)) return 0;
    return -1;
  }
  swap4((char *)&buf, 4);
  if (buf == IMDVERSION) {
    if (!imd_go(s)) return 1;
  }
  
  // We failed to determine endianness.
  return -1; 
}

IMDType imd_recv_header(void *s, int32 *length) {
  IMDheader header;
  if (imd_readn(s, (char *)&header, HEADERSIZE) != HEADERSIZE)
    return IMD_IOERROR;
  int i;
  char *ch = (char*)(&header);
  swap_header(&header);
  *length = header.length;
  return IMDType(header.type); 
}

int imd_recv_mdcomm(void *s, int32 n, int32 *indices, float *forces) {
  if (imd_readn(s, (char *)indices, 4*n) != 4*n) return 1;
  if (imd_readn(s, (char *)forces, 12*n) != 12*n) return 1;
  return 0;
}

int imd_recv_energies(void *s, IMDEnergies *energies) {
  return (imd_readn(s, (char *)energies, sizeof(IMDEnergies))
          != sizeof(IMDEnergies));
}

int imd_recv_fcoords(void *s, int32 n, float *coords) {
  return (imd_readn(s, (char *)coords, 12*n) != 12*n);
}