examples/unix/ffi_example: Clean up and update the ffi example.

1. Use uctypes.bytearray_at().

Implementation of the "ffi" module predates that of "uctypes", so
initially some convenience functions to access memory were added
to ffi. Later, they landed in uctypes (which follows CPython's
ctype module).

So, replace undocumented experimental functions from ffi to
documented ones from uctypes.

2. Use more suitable type codes for arguments (e.g. "P" (const void*)
instead of "p" (void*).

3. Some better var naming.

4. Clarify some messages printed by the example.
This commit is contained in:
Paul Sokolovsky 2018-10-20 12:36:48 +03:00 committed by Damien George
parent 42d0a28117
commit af5b509c75
1 changed files with 9 additions and 8 deletions

View File

@ -1,4 +1,5 @@
import ffi
import uctypes
libc = ffi.open("libc.so.6")
print("libc:", libc)
@ -8,7 +9,7 @@ print()
perror = libc.func("v", "perror", "s")
time = libc.func("i", "time", "p")
open = libc.func("i", "open", "si")
qsort = libc.func("v", "qsort", "piip")
qsort = libc.func("v", "qsort", "piiC")
# And one variable
errno = libc.var("i", "errno")
@ -16,23 +17,23 @@ print("time:", time)
print("UNIX time is:", time(None))
print()
perror("ffi before error")
perror("perror before error")
open("somethingnonexistent__", 0)
print("errno object:", errno)
print("errno value:", errno.get())
perror("ffi after error")
perror("perror after error")
print()
def cmp(pa, pb):
a = ffi.as_bytearray(pa, 1)
b = ffi.as_bytearray(pb, 1)
a = uctypes.bytearray_at(pa, 1)
b = uctypes.bytearray_at(pb, 1)
print("cmp:", a, b)
return a[0] - b[0]
cmp_c = ffi.callback("i", cmp, "pp")
print("callback:", cmp_c)
cmp_cb = ffi.callback("i", cmp, "PP")
print("callback:", cmp_cb)
s = bytearray(b"foobar")
print("org string:", s)
qsort(s, len(s), 1, cmp_c)
qsort(s, len(s), 1, cmp_cb)
print("qsort'ed string:", s)