python - 使用 C python api 时消息长度不正确

Question

我正在尝试扩展 libhydrogen(在此处找到开源代码:https://github.com/jedisct1/libhydrogen/)以支持对 Python 中的底层库的调用。但是，我遇到了一个奇怪的问题。具体来说，我有以下代码:

static PyObject* crypto_secretbox_encrypt(PyObject* self, PyObject* args){
    char* m;
    size_t mlen;
    uint64_t msg_id;
    char *ctx;
    size_t ctx_len;
    const uint8_t *key; //this shouldn't matter its secret
    size_t key_len;
    PyArg_ParseTuple(args, "s#|K|s#|s#", &m, &mlen, &msg_id, &ctx, &ctx_len, &key, &key_len); //only s# accepts null bytes, need to random pointers to store lengths
    //printf("Parsed \n");
    //printf("MSG: %s, MSG_ID: %" PRIu64 ", CTX: %s\n", m, msg_id, ctx);
    if(ctx_len != hydro_secretbox_CONTEXTBYTES){
        PyErr_Format(PyExc_ValueError, "Context not of correct size: Received %lu bytes", ctx_len);
        return NULL;
    }

    if(key_len != hydro_secretbox_KEYBYTES){
        PyErr_Format(PyExc_ValueError, "Key not of correct size: Received %lu bytes", key_len);
        return NULL;
    }

它能够成功解析ctx的长度，但是，当它到达键时会抛出错误，

  File "cryptotest.py", line 7, in <module>
    c1 = crypto.secretbox_encrypt("message1", 0, "\x00"*8, '\x00'*32);
ValueError: Key not of correct size: Received 140123308032032 bytes

关于为什么我无法成功解析 key 长度的任何想法？

Answer 1

您已将长度指定为 size_t。 s# 格式不采用 size_t。 It takes an int or Py_ssize_t ，取决于 PY_SSIZE_T_CLEAN 宏在包含 Python.h 之前是否为 #defined。

Note: For all # variants of formats (s#, y#, etc.), the type of the length argument (int or Py_ssize_t) is controlled by defining the macro PY_SSIZE_T_CLEAN before including Python.h. If the macro was defined, length is a Py_ssize_t rather than an int. This behavior will change in a future Python version to only support Py_ssize_t and drop int support. It is best to always define PY_SSIZE_T_CLEAN.