Convert from IBM floating point to IEEE floating point standard and Vice Versa- In C #?

Question

Looking for a way to enter IEEE floating point numbers in the IBM floating point format for the old system we are using. Is there a general formula that we can use in C # for this purpose. Any tat libraries can help.

Answer 1

// http://en.wikipedia.org/wiki/IBM_Floating_Point_Architecture // float2ibm(-118.625F) == 0xC276A000 // 1 100 0010 0111 0110 1010 0000 0000 0000 // IBM/370 single precision, 4 bytes // xxxx.xxxx xxxx.xxxx xxxx.xxxx xxxx.xxxx // s|-exp--| |--------fraction-----------| // (7) (24) // value = (-1)**s * 16**(e - 64) * .f range = 5E-79 ... 7E+75 static int float2ibm(float from) { byte[] bytes = BitConverter.GetBytes(from); int fconv = (bytes[3] << 24) | (bytes[2] << 16) | (bytes[1] << 8)| bytes[0]; if (fconv == 0) return 0; int fmant = (0x007fffff & fconv) | 0x00800000; int t = (int)((0x7f800000 & fconv) >> 23) - 126; while (0 != (t & 0x3)) { ++t; fmant >>= 1; } fconv = (int)(0x80000000 & fconv) | (((t >> 2) + 64) << 24) | fmant; return fconv; // big endian order } 

I changed a piece of code called static void float_to_ibm (int from [], int to [], int n, int endian) the above code can be correctly run on a PC from a few floating point numbers. The return value is a large ibm serial number, but is stored in the int type.

Answer 2

An obvious approach would be to use a textual representation of the number as an exchange format.

Answer 3

I recently had to convert one swim to another. It appears that the XDR format uses an odd format for its floats. Therefore, when converting from XDR to standard floats, this code did this.

 #include <rpc/rpc.h> // Read in XDR float array, copy to standard float array // out array needs to be allocated before the function call bool convertFromXdrFloatArray(float *in, float *out, long size) { XDR xdrs; xdrmem_create(&xdrs,(char *)in, size*sizeof(float), XDR_DECODE); for(int i = 0; i < size; i++) { if(!xdr_float(&xdrs, out++)) { fprintf(stderr,"%s:%d:ERROR:xdr_float\n",__FILE__,__LINE__); exit(1); } } xdr_destroy(&xdrs); return true; } 

Answer 4

Using the first answer, I added the following, which may be useful in some cases:

///

  /// Converts an IEEE floating number to its string representation (4 or 8 ascii codes). /// Useful for SAS XPORT files format. /// </summary> /// <param name="from_">IEEE number</param> /// <param name="padTo8_">When true, output is 8 chars rather than 4</param> /// <returns>Printable string according to hardware endianness</returns> public static string Float2IbmAsAsciiCodes(float from_, bool padTo8_ = true) { StringBuilder sb = new StringBuilder(); string s; byte[] bytes = BitConverter.GetBytes(Float2Ibm(from_)); // big endian order if (BitConverter.IsLittleEndian) { // Revert bytes order for (int i = 3; i > -1; i--) sb.Append(Convert.ToChar(bytes[i])); s = sb.ToString(); if (padTo8_) s = s.PadRight(8, '\0'); return s; } else { for (int i = 0; i < 8; i++) sb.Append(Convert.ToChar(bytes[i])); s = sb.ToString(); if (padTo8_) s = s.PadRight(8, '\0'); return s; } }