Category : Files from Magazines
Archive   : CUJ9306.ZIP
Filename : 1106113A

enum File_state { UNOPENED, BUFFER_ALLOCATED, FILE_OPEN,
RECORD_READ};
char * File_state_strings[] = {"Unopened", "Buffer allocation",
"File open", "File reading"};

typedef struct
{
enum File_state state; // Current state of file
int file_id; // Id from open
char *buffer; // Buffer for read
} File;

int File_initialize(File * file, char *filename, char *purpose);
void File_terminate(File * file);

#define SUCCESS 1
#define FAILURE 0

main()
{
File file;
int return_code;
if (File_initialize(&file, "filename", "purpose") == SUCCESS)
{
return_code = 0;
/* Do whatever required */
}
else
return_code = 1;
File_terminate(&file);
exit(return_code);
}

int File_initialize(File * file, char *filename, char *purpose)
{
int read_count;
int return_code = FAILURE;
file->state = UNOPENED;
if (Buffer_initialize(&file->buffer, BUFSIZ, "file buffer")
== SUCCESS)
file->state = BUFFER_ALLOCATED;
if (file->state == BUFFER_ALLOCATED)
{
file->file_id = open(filename, O_RDONLY);
if (file->file_id >= 0)

file->state = FILE_OPEN;
}
if (file->state == FILE_OPEN)
{
read_count = read(file->file_id, file->buffer, BUFSIZ);
if (read_count > 0)
{
file->state = RECORD_READ;
return_code = SUCCESS;
}
}
if (return_code != SUCCESS)
fprintf(stderr, "Filename %s purpose %s error at %s",
filename, purpose, File_state_strings[file->state]);
return return_code;
}

void File_terminate(File * file)
{
/*** Maintenance note - fall through required ***/
switch(file->state)
{
case RECORD_READ:
case FILE_OPEN:
close(file->file_id);
case BUFFER_ALLOCATED:
Buffer_terminate(&file->buffer);
case UNOPENED:
break;
default:
fprintf("Error in File_terminate -- illegal state");
}
return;
}