c语言如何读取一个exc文件,15.19 从C语言中读取类文件对象

解决方案¶

要读取一个类文件对象的数据，你需要重复调用 read() 方法，然后正确的解码获得的数据。

下面是一个C扩展函数例子，仅仅只是读取一个类文件对象中的所有数据并将其输出到标准输出：

#define CHUNK_SIZE 8192

/* Consume a "file-like" object and write bytes to stdout */

static PyObject *py_consume_file(PyObject *self, PyObject *args) {

PyObject *obj;

PyObject *read_meth;

PyObject *result = NULL;

PyObject *read_args;

if (!PyArg_ParseTuple(args,"O", &obj)) {

return NULL;

}

/* Get the read method of the passed object */

if ((read_meth = PyObject_GetAttrString(obj, "read")) == NULL) {

return NULL;

}

/* Build the argument list to read() */

read_args = Py_BuildValue("(i)", CHUNK_SIZE);

while (1) {

PyObject *data;

PyObject *enc_data;

char *buf;

Py_ssize_t len;

/* Call read() */

if ((data = PyObject_Call(read_meth, read_args, NULL)) == NULL) {

goto final;

}

/* Check for EOF */

if (PySequence_Length(data) == 0) {

Py_DECREF(data);

break;

}

/* Encode Unicode as Bytes for C */

if ((enc_data=PyUnicode_AsEncodedString(data,"utf-8","strict"))==NULL) {

Py_DECREF(data);

goto final;

}

/* Extract underlying buffer data */

PyBytes_AsStringAndSize(enc_data, &buf, &len);

/* Write to stdout (replace with something more useful) */

write(1, buf, len);

/* Cleanup */

Py_DECREF(enc_data);

Py_DECREF(data);

}

result = Py_BuildValue("");

final:

/* Cleanup */

Py_DECREF(read_meth);

Py_DECREF(read_args);

return result;

}

要测试这个代码，先构造一个类文件对象比如一个StringIO实例，然后传递进来：

>>>import io

>>>f = io.StringIO('Hello\nWorld\n')

>>>import sample

>>>sample.consume_file(f)

Hello

World

>>>