/*****************************************************************************
*
* LoadBMP
*
* Uses GS/OS native I/O routines to read in a windows BMP file.  We only
* support 4-bit, uncompressed images
*
*****************************************************************************/

#include <Memory.h>
#include <GSOS.h>
#include "bmp.h"

Handle LoadBMP( char *filename, LocInfo *locInfo, Word *colorTable )
{
   FileInfoRec fiRec;            /* GetFileInfo record */
   RefNumRecGS clRec;            /* CloseGS record */
   OpenRecGS opRec;              /* OpenGS record */
   IORecGS rdRec;                /* ReadGS record */
   SetPositionRecGS spRec;       /* SetMarkGS record */
   GSString255 fileStr;          

   BMPHeader bmpHeader;
   BMPInfo   bmpInfo;
   RGBTuple  bmpColor;
   Pointer   imagePtr;
   Handle    imageHndl = NULL;      /* handle to the memory it's in */
   LongWord  buffsize;
   int i;

   /* Convert the filename to a p-string */
   fileStr.length = strlen( filename );
   strcpy( fileStr.text, filename );

   /* Only open binary files (Filetype $06) */
   fiRec.pCount   = 4;
   fiRec.pathname = &fileStr;
   GetFileInfoGS(&fiRec);

   /* If we cannot get the file information, fail */
   if (toolerror()) 
      return NULL;
   
   /* Verify the filetype and auxtype match */
   if ( fiRec.fileType != 0x06 )
      return NULL;

   /* We've verified it is a binary file, open the file */
   opRec.pCount         = 12;
   opRec.pathname       = &fileStr;
   opRec.requestAccess  = 1;
   opRec.resourceNumber = 0;
   opRec.optionList     = NULL;

   OpenGS(&opRec);
   if (toolerror())
      return NULL;

   /* Fill in part of other records with data from the open record */
   clRec.pCount = 1;
   clRec.refNum = opRec.refNum;

   /* These parameters remain the same in the inner loop */
   spRec.pCount = 3;
   spRec.refNum = opRec.refNum;
   spRec.base   = startPlus;
   spRec.displacement = 0;

   rdRec.pCount = 4;
   rdRec.refNum = opRec.refNum;

   /* Read in the BMP header */
   rdRec.dataBuffer   = (Pointer) &bmpHeader;
   rdRec.requestCount = 14;

   ReadGS(&rdRec);
   if (toolerror() != 0)
      goto fail;

   /* Signature 'BM' */
   if ( bmpHeader.type != 0x4D42 )
      goto fail;

   /* Read the BMP Info record */
   rdRec.dataBuffer   = (Pointer) &bmpInfo;
   rdRec.requestCount = 40;

   ReadGS(&rdRec);
   if (toolerror() != 0)
      goto fail;

   /**
    * We only support 4 bits per pixel, 1 graphics plane and image sizes
    * less than 64K
    */
   if ( bmpInfo.planes != 1 || bmpInfo.compression != BMP_NO_COMPRESS ||
        bmpInfo.bits != 4 || bmpInfo.imagesize >= 0x010000 )
      goto fail;

   /* Everything is fine.  */
   if ( colorTable != NULL ) {

      for ( i = 0; i < bmpInfo.ncolors; i++ )
      {
         /* Read in the color */
         rdRec.dataBuffer   = (Pointer) &bmpColor;
         rdRec.requestCount = 4;
         ReadGS(&rdRec);

         colorTable[i] = (bmpColor.b >> 4) | (bmpColor.g & 0xF0) |
                         ((bmpColor.r & 0xF0) << 4);
      }
   }

   /* Fill in the locInfo record and allocate the memory, round width to */
   /* the nearest multiple of eight byte                                 */
   locInfo->portSCB = 0x00;
   locInfo->width = ((bmpInfo.width + 15) / 2) & 0xFFF8;
   locInfo->boundsRect.v1 = 0;
   locInfo->boundsRect.h1 = 0;
   locInfo->boundsRect.v2 = bmpInfo.height;
   locInfo->boundsRect.h2 = bmpInfo.width;

   buffsize = bmpInfo.height * locInfo->width;

   /* Allocate the memory */
   imageHndl = NewHandle( buffsize, userid(), 0x8014, NULL );
   if ( toolerror() )
      goto fail;

   /* Finish filling in the locInfo record */
   imagePtr = *imageHndl;
   locInfo->ptrToPixImage = imagePtr;

   /* Move the the data */
   spRec.base         = startPlus;
   spRec.displacement = bmpHeader.offset;
   SetMarkGS( &spRec );

   /* Read in the data. It is stored bottom-up, left-to-right */
   imagePtr += (bmpInfo.height - 1) * locInfo->width;

   for (i = 0; i < bmpInfo.height; i++)
   {
      rdRec.dataBuffer   = (Pointer) imagePtr;
      rdRec.requestCount = bmpInfo.width / 2;
      ReadGS(&rdRec);

      if ( toolerror() )
         break;

      imagePtr -= locInfo->width;
   }

 fail:
   CloseGS(&clRec);                  /* close the file */
   return imageHndl;
}