96 lines
4.3 KiB
Plaintext
96 lines
4.3 KiB
Plaintext
import testcheck
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# 大小端字节序专项：
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# · 标记 `bigend` 的槽位，在（默认的）小端目标上必须以**大端字节序列**存放；
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# · 标记 `littlend` 的槽位与目标序一致，按目标序存放；
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# · 无标记 = native，不参与任何交换。
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# 因此本测试既校验「读写成对交换」的语义不变式（round-trip），
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# 又**直接检查内存里的字节序列** —— 只有后者能真正证明交换发生了
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# （纯 round-trip 即使不交换也会通过，因为读写交换会互相抵消）。
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def read_byte(p: rawptr, i: int) -> int:
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"""读指针第 i 个字节；i8 按有符号解释，这里只取低 8 位。"""
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return int(p[i]) & 0xFF
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def test_big_endian_local() -> None:
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"""大端局部变量：内存字节必须是 12 34 56 78（MSB 在前），读回值不变。"""
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testcheck.section("BigEndian local variable")
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x: bigend int32 = 0x12345678
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px: rawptr = rawptr(&x)
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testcheck.check(read_byte(px, 0) == 0x12, "BigEndian memory byte[0] = 0x12 (MSB first)", "expect 0x12")
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testcheck.check(read_byte(px, 1) == 0x34, "BigEndian memory byte[1] = 0x34", "expect 0x34")
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testcheck.check(read_byte(px, 2) == 0x56, "BigEndian memory byte[2] = 0x56", "expect 0x56")
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testcheck.check(read_byte(px, 3) == 0x78, "BigEndian memory byte[3] = 0x78 (LSB last)", "expect 0x78")
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testcheck.check(x == 0x12345678, "BigEndian local round-trip", "expect 0x12345678")
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def test_little_endian_local() -> None:
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"""小端局部变量：小端目标上与目标序一致，内存字节是 78 56 34 12（LSB 在前）。"""
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testcheck.section("LittleEndian local variable")
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y: littlend int32 = 0x12345678
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py: rawptr = rawptr(&y)
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testcheck.check(read_byte(py, 0) == 0x78, "LittleEndian memory byte[0] = 0x78 (LSB first)", "expect 0x78")
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testcheck.check(read_byte(py, 3) == 0x12, "LittleEndian memory byte[3] = 0x12", "expect 0x12")
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testcheck.check(y == 0x12345678, "LittleEndian local round-trip", "expect 0x12345678")
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def test_be_le_differ() -> None:
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"""同一值分别按大端/小端存放，内存字节序列必须互为反转。"""
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testcheck.section("BigEndian vs LittleEndian memory layout")
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a: bigend int32 = 0x22334455
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b: littlend int32 = 0x22334455
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pa: rawptr = rawptr(&a)
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pb: rawptr = rawptr(&b)
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testcheck.check(read_byte(pa, 0) == read_byte(pb, 3), "BE byte[0] == LE byte[3]", "expect reversed byte order")
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testcheck.check(read_byte(pa, 1) == read_byte(pb, 2), "BE byte[1] == LE byte[2]", "expect reversed byte order")
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testcheck.check(read_byte(pa, 0) == 0x22, "BigEndian starts with MSB (0x22)", "expect 0x22")
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class NetHeader:
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"""经典用法：结构体成员带字节序标记（对齐 TransPyC 文档里的 NetHeader）。"""
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magic: bigend int32
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length: littlend int16
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body: int32
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def test_struct_field_roundtrip() -> None:
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"""结构体成员：带标记的字段读写必须相等（读写成对交换的语义不变式）。"""
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testcheck.section("Byte-order struct fields")
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h: NetHeader = NetHeader()
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h.magic = 0x11223344
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h.length = 0x5566
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h.body = 0x778899AA
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testcheck.check(h.magic == 0x11223344, "BigEndian field magic round-trip", "expect 0x11223344")
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testcheck.check(h.length == 0x5566, "BigEndian field length round-trip", "expect 0x5566")
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testcheck.check(h.body == 0x778899AA, "native field body round-trip", "expect 0x778899AA")
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# 赋值后再读第二次，确保交换是成对的、不会逐次累积
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testcheck.check(h.magic == 0x11223344, "BigEndian field second read unchanged", "expect 0x11223344")
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def test_repeated_write() -> None:
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"""反复写入不同值，读回始终正确（交换必须成对且不残留）。"""
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testcheck.section("Repeated writes")
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x: bigend int32 = 0
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i: int = 0
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ok: int = 1
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for i in range(int(4)):
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v: int32 = int32(0x10000000 * (i + 1))
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x = v
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if x != v:
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ok = 0
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testcheck.check(ok == 1, "BigEndian repeated writes stay consistent", "expect all round-trips to match")
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def main() -> int:
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testcheck.begin("EndianTest: BigEndian / LittleEndian byte order")
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test_big_endian_local()
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test_little_endian_local()
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test_be_le_differ()
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test_struct_field_roundtrip()
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test_repeated_write()
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return testcheck.end()
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