wosfs.c

很多仪器都输出同步时钟

//
// file: wosfs.c
//
// "Way Oversimplified File System"
// A flat memory-based file system
// which supports reading of files only,
// but not writing. (It could be easily
// extended to support appending, perhaps.)
//
// [e-mail] 2001 April 25
//


#include "wosfs.h"




// +-----------------------------
// | Local Prototypes

static void r_read_from_flash(long offset,long length,void *data_out);


// +----------------------------
// | Routines

static void r_read_from_flash(long offset,long length,void *data_out)
	{
	int i;
	for (i = 0; i < length; ++i)
		{
		((unsigned char*)data_out)[i] = ((unsigned char*)nk_wosfs_flash_begin)[i + offset];
		}
	}

long nr_wosfs_get_file_count(void)
  {
  ns_wosfs_volume_header vh;

  r_read_from_flash(0,sizeof(ns_wosfs_volume_header),&vh);
  if (nk_wosfs_signature != vh.signature)
  {
    return 0;
  }
  return vh.file_count;
  }

void nr_wosfs_get_directory_entry(long file_index,ns_wosfs_directory_entry *de_out)
  {
  r_read_from_flash(sizeof(ns_wosfs_volume_header) + file_index * sizeof(ns_wosfs_directory_entry),
      sizeof(ns_wosfs_directory_entry),de_out);
  }

int nr_wosfs_string_match(char *a, char *b) // return 1 if match
  {
  char *x = a;

  while(*a || *b)
    {
    if(*a++ != *b++)
      return 0;
    }
  return 1;
  }
 
long nr_wosfs_get_directory_entry_by_name(char *file_name,ns_wosfs_directory_entry *de_out)
  {
  ns_wosfs_directory_entry de;
  int file_index;
  int file_count;

  file_count = nr_wosfs_get_file_count();
  for(file_index = 0; file_index < file_count; file_index++)
    {
    nr_wosfs_get_directory_entry(file_index,&de);
    if(nr_wosfs_string_match(file_name,de.name))
    	{
	if(de_out)
		*de_out = de;
    	return file_index;
	}
    }
  return -1;
  }

void nr_wosfs_read(long file_index,long offset,long length,void *data_out)
  {
  ns_wosfs_directory_entry de;

  r_read_from_flash(sizeof(ns_wosfs_volume_header) + file_index * sizeof(ns_wosfs_directory_entry),
      sizeof(ns_wosfs_directory_entry),&de);

  r_read_from_flash(de.location + offset,length,data_out);
  }