disk8: Initial commit

[pdp8.git] / sw / disk8 / src / file.c

/* File operations */

#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>

#include "logging.h"

#include "structures.h"

/* 
 * The following values are based on the address limitiations of OS/8.
 * That guarantees that we'll never encounter a legal image that's 
 * bigger then calculated here.
 */
#define MAX_BLOCKS 4096
#define WORDS_PER_BLOCK (129*2) /* Two physical 129 word DECTape blocks     */
#define BYTES_PER_WORD 2        /* That's the way we store 12 bit on the PC */
#define PARTITIONS 2            /* An RK05 holds the whole circus twice!    */
#define READIN_SIZE (MAX_BLOCKS * WORDS_PER_BLOCK * BYTES_PER_WORD * PARTITIONS)


/*!
 *\brief The file read buffer
 */
static char file_buf[READIN_SIZE];

/*!
 * \brief Clear a disk image
 * \arg image Pointer to an image_t structure.
 *
 * The image will be completely zeroed. 
 * Take care not to pass a bad pointer!
 */
void image_clear(image_t * image){
   memset (image,0, sizeof(image_t));
}


/*!
 * \brief Load and analyze an image file
 *  
 * The image file is loaded into the file buffer.
 * Then the data is copied into the image_t structure.
 * 129 word blocks (DECTape) are eliminiated before copying. 
 *
 * \param image Pointer to an allocated image_t structure.
 * If image is NULL, a new image_t structure will be allocated
 * and used.
 * \param filename Name of the file to load from disk
 * \return A Pointer to the initialized image_t structure.
 * If image was not NULL, this is identical to image. 
 * \retval NULL on errors.
 *
 */
image_t * image_load(image_t *image,
		     const char * filename
		     ){

  /* Allocate memory if desired */
  if (image==NULL){
    image=(image_t *)malloc(sizeof(image_t));
  }

  MESSAGE("Loading file \"%s\":\n",filename);

  /* We start with lots of zeroes.. */
  image_clear(image);

  int fd=open(filename,O_RDONLY);
  if (fd <0){
    ERROR("Could not open file! Reason:\"%s\"\n",strerror(errno));
    return NULL;
  } else DEBUG("File opened successfully.\n");

  DEBUG("READIN_SIZE:%i\n",READIN_SIZE);

  int res=0;
  int fill=0;
  
  do{
    res=read(fd,file_buf+fill,READIN_SIZE-fill);
    DBG ("Read %i bytes from file.\n",res);
    fill+=res;
  } while (res);
  
  close(fd);
  DBG("File closed.\n");
  DBG("Image size is %i bytes\n",fill);
  
  image->raw_size=fill;
  
  /* Now determine image type */

  if (fill%(sizeof(os8_block_t)+4)==0){
    MESSAGE("Image type: DECtape 129\n");
    image->size=fill/(sizeof(os8_block_t)+4);
    image->type=IT_DECTAPE;

    /* In this case, we have to eliminate word 129 of every block. */
    int block;
    for (block=0;block<image->size;block++){
      memcpy(image->data+block*sizeof(os8_block_t),file_buf+block*sizeof(os8_block_t)+4,fill); 
    }
    goto image_done;
  }

  if (fill%sizeof(os8_block_t)==0){
    MESSAGE("Image type: Disk 128\n");
    image->size=fill/sizeof(os8_block_t);
    image->type=IT_DISK;
    memcpy(image->data,file_buf,fill);
    goto image_done;
  }

   
  MESSAGE ("Image length does not fit! Assuming disk image. Hope that's ok...\n");
  image->type=IT_UNKNOWN;
  
  /* We have an incomplete block. Then we simply create one block more. */
  image->size=fill/(sizeof(os8_block_t))+1;
  memcpy(image->data,file_buf,fill);
  
 image_done:
  
  /* Return successfully to the caller. */
  return image;
}