VFS

[David Laur]

At the risk of being a bit object-oriented, it seems to me that
maintaining a context, an "object" if you like, for each virtual
share makes things a lot more manageable.

So, I think that Tim's connection_struct is on the right track.

The "obvious" alternative to specifying it as an argument in every
routine would be a C++ object which would implement the various
open(), close(), etc, methods.

However, given that plain-old-C is in use, you can still simplify
everything via a struct typedef which maintains the appropriate
pointers for a given share type.

For example:


---------- cut here ------------------------

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

/* --------------------------------------------------------- */

typedef struct VFS_Context_s {
	struct connection_struct *conn;  /* or it's elements directly */
	int (*open) (const char *path, int oflag, ... /* mode_t mode */);
	int (*read) (int fildes, void *buf, size_t nbyte);
	int (*close) (int fd);
	/*  ...  */
} VFS_Context;

/* --------------------------------------------------------- */
VFS_Context *
new_VFS_CRunTimeFile (void)
{
	VFS_Context *ctx = (VFS_Context*) malloc( sizeof(VFS_Context) );

	/* ctx->conn =  xyz;  ... whatever is req'd */

	ctx->open = open;
	ctx->read = read;
	ctx->close = close;

	/*  ...  */

	return( ctx );
}

/* --------------------------------------------------------- */
void
delete_VFS_context (VFS_Context *ctx)
{
	if (ctx) {
		/* do sensible clean-ups, etc */
		free(ctx);
	}
}

/* --------------------------------------------------------- */
int main ()
{
	VFS_Context *vfs;
	int fd;
	char buf[128];
	
	vfs = new_VFS_CRunTimeFile();

	fd = vfs->open("/etc/hosts", O_RDONLY);

	vfs->read(fd, buf, 100);
	buf[100] = 0;

	vfs->close(fd);

	delete_VFS_context(vfs);

	printf("buf = '%s'\n", buf);
	return 0;
}

/* --------------------------------------------------------- */