setup_osutil_cffi.py

rbc: fix superfluous rebuilding from scratch - don't abuse self._rbcnamescount

The code used self._rbcnamescount as if it was the length of self._names ...
but actually it is just the number of good entries on disk. This caused the
cache to be populated inefficiently. In some cases very inefficiently.

Instead of checking the length before lookup, just try a lookup in self._names
- that is also in most cases faster.

Comments and debug messages are tweaked to help understanding the issue
and the fix.

from __future__ import absolute_import

import cffi

ffi = cffi.FFI()
ffi.set_source("_osutil_cffi", """
#include <sys/attr.h>
#include <sys/vnode.h>
#include <unistd.h>
#include <fcntl.h>
#include <time.h>

typedef struct val_attrs {
    uint32_t          length;
    attribute_set_t   returned;
    attrreference_t   name_info;
    fsobj_type_t      obj_type;
    struct timespec   mtime;
    uint32_t          accessmask;
    off_t             datalength;
} __attribute__((aligned(4), packed)) val_attrs_t;
""", include_dirs=['mercurial'])
ffi.cdef('''

typedef uint32_t attrgroup_t;

typedef struct attrlist {
    uint16_t     bitmapcount; /* number of attr. bit sets in list */
    uint16_t   reserved;    /* (to maintain 4-byte alignment) */
    attrgroup_t commonattr;  /* common attribute group */
    attrgroup_t volattr;     /* volume attribute group */
    attrgroup_t dirattr;     /* directory attribute group */
    attrgroup_t fileattr;    /* file attribute group */
    attrgroup_t forkattr;    /* fork attribute group */
    ...;
};

typedef struct attribute_set {
    ...;
} attribute_set_t;

typedef struct attrreference {
    int attr_dataoffset;
    int attr_length;
    ...;
} attrreference_t;

typedef struct val_attrs {
    uint32_t          length;
    attribute_set_t   returned;
    attrreference_t   name_info;
    uint32_t          obj_type;
    struct timespec   mtime;
    uint32_t          accessmask;
    int               datalength;
    ...;
} val_attrs_t;

/* the exact layout of the above struct will be figured out during build time */

typedef int ... time_t;
typedef int ... off_t;

typedef struct timespec {
    time_t tv_sec;
    ...;
};

int getattrlist(const char* path, struct attrlist * attrList, void * attrBuf,
                size_t attrBufSize, unsigned int options);

int getattrlistbulk(int dirfd, struct attrlist * attrList, void * attrBuf,
                    size_t attrBufSize, uint64_t options);

#define ATTR_BIT_MAP_COUNT ...
#define ATTR_CMN_NAME ...
#define ATTR_CMN_OBJTYPE ...
#define ATTR_CMN_MODTIME ...
#define ATTR_CMN_ACCESSMASK ...
#define ATTR_CMN_ERROR ...
#define ATTR_CMN_RETURNED_ATTRS ...
#define ATTR_FILE_DATALENGTH ...

#define VREG ...
#define VDIR ...
#define VLNK ...
#define VBLK ...
#define VCHR ...
#define VFIFO ...
#define VSOCK ...

#define S_IFMT ...

int open(const char *path, int oflag, int perm);
int close(int);

#define O_RDONLY ...
''')

if __name__ == '__main__':
    ffi.compile()