8000 GH-99554: `marshal` bytecode more efficiently by brandtbucher · Pull Request #99555 · python/cpython · GitHub
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GH-99554: marshal bytecode more efficiently #99555

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GH-99554: marshal bytecode more efficiently #99555

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4034318
Compress marshalled bytecode
brandtbucher Nov 15, 2022
8b6b393
blurb add
brandtbucher Nov 16, 2022
5f81b82
Add opcode_for_build
brandtbucher Nov 16, 2022
e34c460
Catch up with main
brandtbucher Dec 15, 2022
23ba802
fixup
brandtbucher Dec 15, 2022
6ed83af
Catch up with main
brandtbucher Dec 17, 2022
5534112
Address review comments
brandtbucher Dec 17, 2022
ead8f26
Catch up with main
brandtbucher Dec 17, 2022
bcd7980
Terminate the compressed bytecode with two zeros
brandtbucher Dec 18, 2022
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Terminate the compressed bytecode with two zeros
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@brandtbucher
brandtbucher committed Dec 18, 2022
commit bcd798058296083c29ff46ae52af3b569c7b44d4
48 changes: 24 additions & 24 deletions Programs/test_frozenmain.h
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14 changes: 11 additions & 3 deletions Python/marshal.c
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Original file line number Diff line number Diff line change
Expand Up @@ -305,6 +305,11 @@ w_bytecode(PyCodeObject *code, WFILE *p)
}
i += _PyOpcode_Caches[opcode];
}
// Terminate with two zero bytes, so that programs scanning .pyc files can
// skip over the bytecode (even if they don't know the compression scheme).
// This is simpler than writing the compressed size in the header, which
// requires two loops (one to count the bytes, then one to write them):
w_short(0, p);
Comment on lines +308 to +312
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Ugh, sorry, I can't stomach this. It feels certain that at some point in the future we'll have a corner case where we encounter \0\0 in the middle. If an extra pass is too expensive let's just go with what you had before. Or let's not do this -- I am feeling pretty lukewarm about this scheme, especially since the register VM will require a whole new approach anyway.

}

static int
Expand Down Expand Up @@ -969,8 +974,8 @@ r_bytecode(RFILE *p)
else {
oparg = 0;
}
assert(0x00 <= opcode && opcode < 0x100);
assert(0x00 <= oparg && oparg < 0x100);
assert(0x01 <= opcode && opcode <= 0xFF);
assert(0x00 <= oparg && oparg <= 0xFF);
buffer[i].opcode = opcode;
buffer[i].oparg = oparg;
i++;
Expand All @@ -981,7 +986,10 @@ r_bytecode(RFILE *p)
i++;
}
}
if (i != size) {
// The compressed bytecode is terminated with two zero bytes (see the
// comment at the bottom of w_bytecode):
int zero_zero = r_short(p);
if (zero_zero == EOF || zero_zero != 0 || i != size) {
const char *e = "bad marshal data (bytecode size incorrect)";
PyErr_SetString(PyExc_ValueError, e);
return NULL;
Expand Down
7 changes: 4 additions & 3 deletions Tools/build/umarshal.py
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65C4
Original file line number Diff line number Diff line change
Expand Up @@ -192,12 +192,13 @@ def r_bytecode(self) -> bytes:
oparg_byte = self.r_byte()
else:
oparg_byte = 0
assert 0x00 <= opcode_byte < 0x100
assert 0x00 <= oparg_byte < 0x100
assert 0x01 <= opcode_byte <= 0xFF
assert 0x00 <= oparg_byte <= 0xFF
bytecode.extend([opcode_byte, oparg_byte])
for _ in range(opcode._inline_cache_entries[opcode_byte]):
bytecode.extend([CACHE, 0])
assert len(bytecode) == nbytes
zero_zero = self.r_short()
assert zero_zero == 0 and len(bytecode) == nbytes
return bytes(bytecode)

def _r_object(self) -> Any:
Expand Down
0