view mercurial/cext/charencode.c @ 39559:07b58266bce3

wireprotov2: implement commands as a generator of objects

Previously, wire protocol version 2 inherited version 1's model of
having separate types to represent the results of different wire
protocol commands.

As I implemented more powerful commands in future commits, I found
I was using a common pattern of returning a special type to hold a
generator. This meant the command function required a closure to
do most of the work. That made logic flow more difficult to follow.
I also noticed that many commands were effectively a sequence of
objects to be CBOR encoded.

I think it makes sense to define version 2 commands as generators.
This way, commands can simply emit the data structures they wish to
send to the client. This eliminates the need for a closure in
command functions and removes encoding from the bodies of commands.

As part of this commit, the handling of response objects has been
moved into the serverreactor class. This puts the reactor in the
driver's seat with regards to CBOR encoding and error handling.
Having error handling in the function that emits frames is
particularly important because exceptions in that function can lead
to things getting in a bad state: I'm fairly certain that uncaught
exceptions in the frame generator were causing deadlocks.

I also introduced a dedicated error type for explicit error reporting
in command handlers. This will be used in subsequent commits.

There's still a bit of work to be done here, especially around
formalizing the error handling "protocol." I've added yet another
TODO to track this so we don't forget.

Test output changed because we're using generators and no longer know
we are at the end of the data until we hit the end of the generator.
This means we can't emit the end-of-stream flag until we've exhausted
the generator. Hence the introduction of 0-sized end-of-stream frames.

Differential Revision: https://phab.mercurial-scm.org/D4472

/*
 charencode.c - miscellaneous character encoding

 Copyright 2008 Matt Mackall <[e-mail]> and others

 This software may be used and distributed according to the terms of
 the GNU General Public License, incorporated herein by reference.
*/

#define PY_SSIZE_T_CLEAN
#include <Python.h>
#include <assert.h>

#include "charencode.h"
#include "compat.h"
#include "util.h"

#ifdef IS_PY3K
/* The mapping of Python types is meant to be temporary to get Python
 * 3 to compile. We should remove this once Python 3 support is fully
 * supported and proper types are used in the extensions themselves. */
#define PyInt_Type PyLong_Type
#define PyInt_AS_LONG PyLong_AS_LONG
#endif

/* clang-format off */
static const char lowertable[128] = {
	'\x00', '\x01', '\x02', '\x03', '\x04', '\x05', '\x06', '\x07',
	'\x08', '\x09', '\x0a', '\x0b', '\x0c', '\x0d', '\x0e', '\x0f',
	'\x10', '\x11', '\x12', '\x13', '\x14', '\x15', '\x16', '\x17',
	'\x18', '\x19', '\x1a', '\x1b', '\x1c', '\x1d', '\x1e', '\x1f',
	'\x20', '\x21', '\x22', '\x23', '\x24', '\x25', '\x26', '\x27',
	'\x28', '\x29', '\x2a', '\x2b', '\x2c', '\x2d', '\x2e', '\x2f',
	'\x30', '\x31', '\x32', '\x33', '\x34', '\x35', '\x36', '\x37',
	'\x38', '\x39', '\x3a', '\x3b', '\x3c', '\x3d', '\x3e', '\x3f',
	'\x40',
	        '\x61', '\x62', '\x63', '\x64', '\x65', '\x66', '\x67', /* A-G */
	'\x68', '\x69', '\x6a', '\x6b', '\x6c', '\x6d', '\x6e', '\x6f', /* H-O */
	'\x70', '\x71', '\x72', '\x73', '\x74', '\x75', '\x76', '\x77', /* P-W */
	'\x78', '\x79', '\x7a',                                         /* X-Z */
	                        '\x5b', '\x5c', '\x5d', '\x5e', '\x5f',
	'\x60', '\x61', '\x62', '\x63', '\x64', '\x65', '\x66', '\x67',
	'\x68', '\x69', '\x6a', '\x6b', '\x6c', '\x6d', '\x6e', '\x6f',
	'\x70', '\x71', '\x72', '\x73', '\x74', '\x75', '\x76', '\x77',
	'\x78', '\x79', '\x7a', '\x7b', '\x7c', '\x7d', '\x7e', '\x7f'
};

static const char uppertable[128] = {
	'\x00', '\x01', '\x02', '\x03', '\x04', '\x05', '\x06', '\x07',
	'\x08', '\x09', '\x0a', '\x0b', '\x0c', '\x0d', '\x0e', '\x0f',
	'\x10', '\x11', '\x12', '\x13', '\x14', '\x15', '\x16', '\x17',
	'\x18', '\x19', '\x1a', '\x1b', '\x1c', '\x1d', '\x1e', '\x1f',
	'\x20', '\x21', '\x22', '\x23', '\x24', '\x25', '\x26', '\x27',
	'\x28', '\x29', '\x2a', '\x2b', '\x2c', '\x2d', '\x2e', '\x2f',
	'\x30', '\x31', '\x32', '\x33', '\x34', '\x35', '\x36', '\x37',
	'\x38', '\x39', '\x3a', '\x3b', '\x3c', '\x3d', '\x3e', '\x3f',
	'\x40', '\x41', '\x42', '\x43', '\x44', '\x45', '\x46', '\x47',
	'\x48', '\x49', '\x4a', '\x4b', '\x4c', '\x4d', '\x4e', '\x4f',
	'\x50', '\x51', '\x52', '\x53', '\x54', '\x55', '\x56', '\x57',
	'\x58', '\x59', '\x5a', '\x5b', '\x5c', '\x5d', '\x5e', '\x5f',
	'\x60',
		'\x41', '\x42', '\x43', '\x44', '\x45', '\x46', '\x47', /* a-g */
	'\x48', '\x49', '\x4a', '\x4b', '\x4c', '\x4d', '\x4e', '\x4f', /* h-o */
	'\x50', '\x51', '\x52', '\x53', '\x54', '\x55', '\x56', '\x57', /* p-w */
	'\x58', '\x59', '\x5a', 					/* x-z */
				'\x7b', '\x7c', '\x7d', '\x7e', '\x7f'
};

/* 1: no escape, 2: \<c>, 6: \u<x> */
static const uint8_t jsonlentable[256] = {
	6, 6, 6, 6, 6, 6, 6, 6, 2, 2, 2, 6, 2, 2, 6, 6, /* b, t, n, f, r */
	6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
	1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, /* " */
	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, /* \\ */
	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 6, /* DEL */
	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
};

static const uint8_t jsonparanoidlentable[128] = {
	6, 6, 6, 6, 6, 6, 6, 6, 2, 2, 2, 6, 2, 2, 6, 6, /* b, t, n, f, r */
	6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6,
	1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, /* " */
	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 6, 1, 6, 1, /* <, > */
	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, /* \\ */
	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
	1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 6, /* DEL */
};

static const char hexchartable[16] = {
	'0', '1', '2', '3', '4', '5', '6', '7',
	'8', '9', 'a', 'b', 'c', 'd', 'e', 'f',
};
/* clang-format on */

/*
 * Turn a hex-encoded string into binary.
 */
PyObject *unhexlify(const char *str, Py_ssize_t len)
{
	PyObject *ret;
	char *d;
	Py_ssize_t i;

	ret = PyBytes_FromStringAndSize(NULL, len / 2);

	if (!ret)
		return NULL;

	d = PyBytes_AsString(ret);

	for (i = 0; i < len;) {
		int hi = hexdigit(str, i++);
		int lo = hexdigit(str, i++);
		*d++ = (hi << 4) | lo;
	}

	return ret;
}

PyObject *isasciistr(PyObject *self, PyObject *args)
{
	const char *buf;
	Py_ssize_t i, len;
	if (!PyArg_ParseTuple(args, PY23("s#:isasciistr", "y#:isasciistr"),
	                      &buf, &len))
		return NULL;
	i = 0;
	/* char array in PyStringObject should be at least 4-byte aligned */
	if (((uintptr_t)buf & 3) == 0) {
		const uint32_t *p = (const uint32_t *)buf;
		for (; i < len / 4; i++) {
			if (p[i] & 0x80808080U)
				Py_RETURN_FALSE;
		}
		i *= 4;
	}
	for (; i < len; i++) {
		if (buf[i] & 0x80)
			Py_RETURN_FALSE;
	}
	Py_RETURN_TRUE;
}

static inline PyObject *
_asciitransform(PyObject *str_obj, const char table[128], PyObject *fallback_fn)
{
	char *str, *newstr;
	Py_ssize_t i, len;
	PyObject *newobj = NULL;
	PyObject *ret = NULL;

	str = PyBytes_AS_STRING(str_obj);
	len = PyBytes_GET_SIZE(str_obj);

	newobj = PyBytes_FromStringAndSize(NULL, len);
	if (!newobj)
		goto quit;

	newstr = PyBytes_AS_STRING(newobj);

	for (i = 0; i < len; i++) {
		char c = str[i];
		if (c & 0x80) {
			if (fallback_fn != NULL) {
				ret = PyObject_CallFunctionObjArgs(
				    fallback_fn, str_obj, NULL);
			} else {
				PyObject *err = PyUnicodeDecodeError_Create(
				    "ascii", str, len, i, (i + 1),
				    "unexpected code byte");
				PyErr_SetObject(PyExc_UnicodeDecodeError, err);
				Py_XDECREF(err);
			}
			goto quit;
		}
		newstr[i] = table[(unsigned char)c];
	}

	ret = newobj;
	Py_INCREF(ret);
quit:
	Py_XDECREF(newobj);
	return ret;
}

PyObject *asciilower(PyObject *self, PyObject *args)
{
	PyObject *str_obj;
	if (!PyArg_ParseTuple(args, "O!:asciilower", &PyBytes_Type, &str_obj))
		return NULL;
	return _asciitransform(str_obj, lowertable, NULL);
}

PyObject *asciiupper(PyObject *self, PyObject *args)
{
	PyObject *str_obj;
	if (!PyArg_ParseTuple(args, "O!:asciiupper", &PyBytes_Type, &str_obj))
		return NULL;
	return _asciitransform(str_obj, uppertable, NULL);
}

PyObject *make_file_foldmap(PyObject *self, PyObject *args)
{
	PyObject *dmap, *spec_obj, *normcase_fallback;
	PyObject *file_foldmap = NULL;
	enum normcase_spec spec;
	PyObject *k, *v;
	dirstateTupleObject *tuple;
	Py_ssize_t pos = 0;
	const char *table;

	if (!PyArg_ParseTuple(args, "O!O!O!:make_file_foldmap", &PyDict_Type,
	                      &dmap, &PyInt_Type, &spec_obj, &PyFunction_Type,
	                      &normcase_fallback))
		goto quit;

	spec = (int)PyInt_AS_LONG(spec_obj);
	switch (spec) {
	case NORMCASE_LOWER:
		table = lowertable;
		break;
	case NORMCASE_UPPER:
		table = uppertable;
		break;
	case NORMCASE_OTHER:
		table = NULL;
		break;
	default:
		PyErr_SetString(PyExc_TypeError, "invalid normcasespec");
		goto quit;
	}

	/* Add some more entries to deal with additions outside this
	   function. */
	file_foldmap = _dict_new_presized((PyDict_Size(dmap) / 10) * 11);
	if (file_foldmap == NULL)
		goto quit;

	while (PyDict_Next(dmap, &pos, &k, &v)) {
		if (!dirstate_tuple_check(v)) {
			PyErr_SetString(PyExc_TypeError,
			                "expected a dirstate tuple");
			goto quit;
		}

		tuple = (dirstateTupleObject *)v;
		if (tuple->state != 'r') {
			PyObject *normed;
			if (table != NULL) {
				normed = _asciitransform(k, table,
				                         normcase_fallback);
			} else {
				normed = PyObject_CallFunctionObjArgs(
				    normcase_fallback, k, NULL);
			}

			if (normed == NULL)
				goto quit;
			if (PyDict_SetItem(file_foldmap, normed, k) == -1) {
				Py_DECREF(normed);
				goto quit;
			}
			Py_DECREF(normed);
		}
	}
	return file_foldmap;
quit:
	Py_XDECREF(file_foldmap);
	return NULL;
}

/* calculate length of JSON-escaped string; returns -1 if unsupported */
static Py_ssize_t jsonescapelen(const char *buf, Py_ssize_t len, bool paranoid)
{
	Py_ssize_t i, esclen = 0;

	if (paranoid) {
		/* don't want to process multi-byte escapes in C */
		for (i = 0; i < len; i++) {
			char c = buf[i];
			if (c & 0x80) {
				PyErr_SetString(PyExc_ValueError,
				                "cannot process non-ascii str");
				return -1;
			}
			esclen += jsonparanoidlentable[(unsigned char)c];
			if (esclen < 0) {
				PyErr_SetString(PyExc_MemoryError,
				                "overflow in jsonescapelen");
				return -1;
			}
		}
	} else {
		for (i = 0; i < len; i++) {
			char c = buf[i];
			esclen += jsonlentable[(unsigned char)c];
			if (esclen < 0) {
				PyErr_SetString(PyExc_MemoryError,
				                "overflow in jsonescapelen");
				return -1;
			}
		}
	}

	return esclen;
}

/* map '\<c>' escape character */
static char jsonescapechar2(char c)
{
	switch (c) {
	case '\b':
		return 'b';
	case '\t':
		return 't';
	case '\n':
		return 'n';
	case '\f':
		return 'f';
	case '\r':
		return 'r';
	case '"':
		return '"';
	case '\\':
		return '\\';
	}
	return '\0'; /* should not happen */
}

/* convert 'origbuf' to JSON-escaped form 'escbuf'; 'origbuf' should only
   include characters mappable by json(paranoid)lentable */
static void encodejsonescape(char *escbuf, Py_ssize_t esclen,
                             const char *origbuf, Py_ssize_t origlen,
                             bool paranoid)
{
	const uint8_t *lentable =
	    (paranoid) ? jsonparanoidlentable : jsonlentable;
	Py_ssize_t i, j;

	for (i = 0, j = 0; i < origlen; i++) {
		char c = origbuf[i];
		uint8_t l = lentable[(unsigned char)c];
		assert(j + l <= esclen);
		switch (l) {
		case 1:
			escbuf[j] = c;
			break;
		case 2:
			escbuf[j] = '\\';
			escbuf[j + 1] = jsonescapechar2(c);
			break;
		case 6:
			memcpy(escbuf + j, "\\u00", 4);
			escbuf[j + 4] = hexchartable[(unsigned char)c >> 4];
			escbuf[j + 5] = hexchartable[(unsigned char)c & 0xf];
			break;
		}
		j += l;
	}
}

PyObject *jsonescapeu8fast(PyObject *self, PyObject *args)
{
	PyObject *origstr, *escstr;
	const char *origbuf;
	Py_ssize_t origlen, esclen;
	int paranoid;
	if (!PyArg_ParseTuple(args, "O!i:jsonescapeu8fast", &PyBytes_Type,
	                      &origstr, &paranoid))
		return NULL;

	origbuf = PyBytes_AS_STRING(origstr);
	origlen = PyBytes_GET_SIZE(origstr);
	esclen = jsonescapelen(origbuf, origlen, paranoid);
	if (esclen < 0)
		return NULL; /* unsupported char found or overflow */
	if (origlen == esclen) {
		Py_INCREF(origstr);
		return origstr;
	}

	escstr = PyBytes_FromStringAndSize(NULL, esclen);
	if (!escstr)
		return NULL;
	encodejsonescape(PyBytes_AS_STRING(escstr), esclen, origbuf, origlen,
	                 paranoid);

	return escstr;
}