Patchwork [1,of,4,lazy-manifest,v2] manifest.c: new extension code to lazily parse manifests

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Submitter Ryan McElroy
Date Jan. 14, 2015, 6:37 p.m.
Message ID <54B6B774.1010501@fb.com>
Download mbox | patch
Permalink /patch/7451/
State Superseded
Commit a5f1bccd2996e76d1d9de82c37129078151e240d
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Comments

Ryan McElroy - Jan. 14, 2015, 6:37 p.m.
On 1/12/2015 12:04 PM, Augie Fackler wrote:
> # HG changeset patch
> # User Augie Fackler <augie@google.com>
> # Date 1420871231 28800
> #      Fri Jan 09 22:27:11 2015 -0800
> # Node ID b9d67bf3ea8196c8530afdcf6b1727682b681259
> # Parent  678f53865c6860a950392691814766957ee89316
> manifest.c: new extension code to lazily parse manifests
>
> This lets us iterate manifests in order, but do a _lot_ less work in
> the common case when we only care about a few manifest entries.
>
> Many thanks to Mike Edgar for reviewing this in advance of it going
> out to the list, which caught many things I missed.
>
> This version of the patch includes C89 fixes from Sean Farley and
> many correctness/efficiency cleanups from Martin von
> Zweigbergk. Thanks to both!
>
> diff --git a/mercurial/manifest.c b/mercurial/manifest.c
> new file mode 100644
> --- /dev/null
> +++ b/mercurial/manifest.c
> @@ -0,0 +1,865 @@
> +/*
> + * manifest.c - manifest type that does on-demand parsing.
> + *
> + * Copyright 2015, Google Inc.
> + *
> + * This software may be used and distributed according to the terms of
> + * the GNU General Public License, incorporated herein by reference.
> + */
> +#include <assert.h>
> +#include <string.h>
> +#include <stdlib.h>
> +
> +#include <Python.h>
> +
> +/* VC9 doesn't include bool and lacks stdbool.h based on my searching */
> +#ifdef _MSC_VER
> +#define true 1
> +#define false 0
> +typedef unsigned char bool;
> +#else
> +#include <stdbool.h>
> +#endif
> +
> +#define DEFAULT_LINES 100000
> +
> +typedef struct {
> +	char *start;
> +	Py_ssize_t len; /* length of line not including terminal newline */
> +	char hash_suffix;
> +	bool from_malloc;
> +	bool deleted;
> +} line;
> +
> +typedef struct {
> +	PyObject_HEAD
> +	PyObject *pydata;
> +	line *lines;
> +	int numlines; /* number of line entries */
> +	int livelines; /* number of non-deleted lines */
> +	int maxlines; /* allocated number of lines */
> +	bool dirty;
> +} lazymanifest;
> +
> +#define MANIFEST_OOM -1
> +#define MANIFEST_NOT_SORTED -2
> +#define MANIFEST_MALFORMED -3
> +
> +/* defined in parsers.c */
> +PyObject *unhexlify(const char *str, int len);
> +
> +/* get the length of the path for a line */
> +static size_t pathlen(line *l) {
> +	return strnlen(l->start, l->len);
> +}
> +
> +/* get the node value of a single line */
> +static PyObject *nodeof(line *l) {
> +	char *s = l->start;
> +	ssize_t llen = pathlen(l);
> +	PyObject *hash = unhexlify(s + llen + 1, 40);
> +	if (!hash) {
> +		return NULL;
> +	}
> +	if (l->hash_suffix != '\0') {
> +		char newhash[21];
> +		memcpy(newhash, PyString_AsString(hash), 20);
> +		Py_DECREF(hash);
> +		newhash[20] = l->hash_suffix;
> +		hash = PyString_FromStringAndSize(newhash, 21);
> +	}
> +	return hash;
> +}
> +
> +/* get the node hash and flags of a line as a tuple */
> +static PyObject *hashflags(line *l)
> +{
> +	char *s = l->start;
> +	size_t plen = pathlen(l);
> +	PyObject *hash = nodeof(l);
> +
> +	/* 40 for hash, 1 for null byte, 1 for newline */
> +	size_t hplen = plen + 42;
> +	Py_ssize_t flen = l->len - hplen;
> +	PyObject *flags;
> +	PyObject *tup;
> +
> +	if (!hash)
> +		return NULL;
> +	if (flen > 0) {
> +		flags = PyString_FromStringAndSize(s + hplen - 1, flen);
> +	} else {
> +		flags = PyString_FromString("");
> +	}
> +	if (!flags) {
> +		Py_DECREF(hash);
> +		return NULL;
> +	}
> +	tup = PyTuple_Pack(2, hash, flags);
> +	Py_DECREF(flags);
> +	Py_DECREF(hash);
> +	return tup;
> +}
> +
> +/* if we're about to run out of space in the line index, add more */
> +static bool realloc_if_full(lazymanifest *self)
> +{
> +	if (self->numlines == self->maxlines) {
> +		self->maxlines *= 2;
> +		self->lines = realloc(self->lines, self->maxlines * sizeof(line));
> +	}
> +	return self->lines;
> +}
> +
> +/*
> + * Find the line boundaries in the manifest that 'data' points to and store
> + * information about each line in 'self'.
> + */
> +static int find_lines(lazymanifest *self, char *data, Py_ssize_t len)
> +{
> +	char *prev = NULL;
> +	line *l = NULL;
> +	while (len > 0) {
> +		char *next = memchr(data, '\n', len);
> +		if (!next) {
> +			return MANIFEST_MALFORMED;
> +		}
> +		next++; /* advance past newline */
> +		if (!realloc_if_full(self)) {
> +			return MANIFEST_OOM; /* no memory */
> +		}
> +		if (prev && strcmp(prev, data) > -1) {
> +			/* This data isn't sorted, so we have to abort. */
> +			return MANIFEST_NOT_SORTED;
> +		}
> +		l = self->lines + ((self->numlines)++);
> +		l->start = data;
> +		l->len = next - data;
> +		l->hash_suffix = '\0';
> +		l->from_malloc = false;
> +		l->deleted = false;
> +		len = len - l->len;
> +		prev = data;
> +		data = next;
> +	}
> +	self->livelines = self->numlines;
> +	return 0;
> +}
> +
> +static int lazymanifest_init(lazymanifest *self, PyObject *args)
> +{
> +	char *data;
> +	Py_ssize_t len;
> +	int err, ret;
> +	PyObject *pydata;
> +	if (!PyArg_ParseTuple(args, "S", &pydata)) {
> +		return -1;
> +	}
> +	err = PyString_AsStringAndSize(pydata, &data, &len);
> +
> +	self->dirty = false;
> +	if (err == -1)
> +		return -1;
> +	self->pydata = pydata;
> +	Py_INCREF(self->pydata);
> +	Py_BEGIN_ALLOW_THREADS
> +	self->lines = malloc(DEFAULT_LINES * sizeof(line));
> +	self->maxlines = DEFAULT_LINES;
> +	self->numlines = 0;
> +	if (!self->lines)
> +		ret = -2;
> +	else
> +		ret = find_lines(self, data, len);
> +	Py_END_ALLOW_THREADS
> +	switch (ret) {
> +	case 0:
> +		break;
> +	case MANIFEST_OOM:
> +		PyErr_NoMemory();
> +		break;
> +	case MANIFEST_NOT_SORTED:
> +		PyErr_Format(PyExc_ValueError,
> +		             "Manifest lines not in sorted order.");
> +		break;
> +	case MANIFEST_MALFORMED:
> +		PyErr_Format(PyExc_ValueError,
> +		             "Manifest did not end in a newline.");
> +		break;
> +	default:
> +		PyErr_Format(PyExc_ValueError,
> +		             "Unknown problem parsing manifest.");
> +	}
> +	return ret == 0 ? 0 : -1;
> +}
> +
> +static void lazymanifest_dealloc(lazymanifest *self)
> +{
> +	/* free any extra lines we had to allocate */
> +	int i;
> +	for (i = 0; i < self->numlines; i++) {
> +		if (self->lines[i].from_malloc) {
> +			free(self->lines[i].start);
> +		}
> +	}
> +	if (self->lines) {
> +		free(self->lines);
> +		self->lines = NULL;
> +	}
> +	if (self->pydata) {
> +		Py_DECREF(self->pydata);
> +		self->pydata = NULL;
> +	}
> +	PyObject_Del(self);
> +}
> +
> +/* iteration support */
> +
> +typedef struct {
> +	PyObject_HEAD lazymanifest *m;
> +	Py_ssize_t pos;
> +} lmIter;
> +
> +static void lmiter_dealloc(PyObject *o)
> +{
> +	lmIter *self = (lmIter *)o;
> +	Py_DECREF(self->m);
> +	PyObject_Del(self);
> +}
> +
> +static PyObject *lmiter_iternext(PyObject *o)
> +{
> +	size_t pl;
> +	line *l;
> +	Py_ssize_t consumed;
> +	PyObject *ret = NULL, *path = NULL, *hash = NULL, *flags = NULL;
> +	lmIter *self = (lmIter *)o;
> +	Py_ssize_t index = self->pos++;
> +	/* skip over deleted manifest entries */
> +	while (index < self->m->numlines &&
> +	       self->m->lines[index].deleted) {
> +		index = ++(self->pos);
> +	}
> +	if (self->m->numlines <= index) {
> +		goto bail;
> +	}
> +	l = &(self->m->lines[index]);
> +	pl = pathlen(l);
> +	path = PyString_FromStringAndSize(l->start, pl);
> +	hash = nodeof(l);
> +	consumed = pl + 41;
> +	if (l->len > (consumed + 1)) {
> +		flags = PyString_FromStringAndSize(l->start + consumed,
> +		                                   l->len - consumed - 1);
> +	} else {
> +		flags = PyString_FromString("");
> +
> +	}
> +	if (!flags) {
> +		goto bail;
> +	}
> +	ret = PyTuple_Pack(3, path, hash, flags);
> + bail:
> +	Py_XDECREF(path);
> +	Py_XDECREF(hash);
> +	Py_XDECREF(flags);
> +	return ret;
> +}
> +
> +static PyTypeObject lazymanifestIterator = {
> +	PyObject_HEAD_INIT(NULL)
> +	0,                               /*ob_size */
> +	"parsers.lazymanifest.iterator", /*tp_name */
> +	sizeof(lmIter),                  /*tp_basicsize */
> +	0,                               /*tp_itemsize */
> +	lmiter_dealloc,                  /*tp_dealloc */
> +	0,                               /*tp_print */
> +	0,                               /*tp_getattr */
> +	0,                               /*tp_setattr */
> +	0,                               /*tp_compare */
> +	0,                               /*tp_repr */
> +	0,                               /*tp_as_number */
> +	0,                               /*tp_as_sequence */
> +	0,                               /*tp_as_mapping */
> +	0,                               /*tp_hash */
> +	0,                               /*tp_call */
> +	0,                               /*tp_str */
> +	0,                               /*tp_getattro */
> +	0,                               /*tp_setattro */
> +	0,                               /*tp_as_buffer */
> +	/* tp_flags: Py_TPFLAGS_HAVE_ITER tells python to
> +	   use tp_iter and tp_iternext fields. */
> +	Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_ITER,
> +	"Iterator for a lazymanifest.",  /* tp_doc */
> +	0,                               /* tp_traverse */
> +	0,                               /* tp_clear */
> +	0,                               /* tp_richcompare */
> +	0,                               /* tp_weaklistoffset */
> +	PyObject_SelfIter,               /* tp_iter: __iter__() method */
> +	lmiter_iternext,                 /* tp_iternext: next() method */
> +};
> +
> +static lazymanifest *lazymanifest_copy(
> +	lazymanifest *self, PyObject *unused_args);
> +
> +static PyObject *lazymanifest_getiter(lazymanifest *self)
> +{
> +	lmIter *i = NULL;
> +	lazymanifest *t = lazymanifest_copy(self, NULL);
> +	if (!t) {
> +		PyErr_NoMemory();
> +		return NULL;
> +	}
> +	i = PyObject_New(lmIter, &lazymanifestIterator);
> +	if (i) {
> +		i->m = t;
> +		i->pos = 0;
> +	} else {
> +		Py_DECREF(t);
> +		PyErr_NoMemory();
> +	}
> +	return (PyObject *)i;
> +}
> +
> +/* __getitem__ and __setitem__ support */
> +
> +static Py_ssize_t lazymanifest_size(lazymanifest *self)
> +{
> +	return self->livelines;
> +}
> +
> +static int linecmp(const void *left, const void *right)
> +{
> +	return strcmp(((const line *)left)->start,
> +	              ((const line *)right)->start);
> +}
> +
> +static PyObject *lazymanifest_getitem(lazymanifest *self, PyObject *key)
> +{
> +	line needle;
> +	line *hit;
> +	if (!PyString_Check(key)) {
> +		PyErr_Format(PyExc_TypeError,
> +		             "getitem: manifest keys must be a string.");
> +		return NULL;
> +	}
> +	needle.start = PyString_AsString(key);
> +	needle.len = 0;
> +	hit = bsearch(&needle, self->lines, self->numlines, sizeof(line),
> +	              &linecmp);
> +	if (!hit || hit->deleted) {
> +		PyErr_Format(PyExc_KeyError, "No such manifest entry.");
> +		return NULL;
> +	}
> +	return hashflags(hit);
> +}
> +
> +static int lazymanifest_delitem(lazymanifest *self, PyObject *key)
> +{
> +	line needle;
> +	line *hit;
> +	if (!PyString_Check(key)) {
> +		PyErr_Format(PyExc_TypeError,
> +		             "delitem: manifest keys must be a string.");
> +		return -1;
> +	}
> +	needle.start = PyString_AsString(key);
> +	needle.len = 0;
> +	hit = bsearch(&needle, self->lines, self->numlines, sizeof(line),
> +	              &linecmp);
> +	if (!hit || hit->deleted) {
> +		PyErr_Format(PyExc_KeyError,
> +		             "Tried to delete nonexistent manifest entry.");
> +		return -1;
> +	}
> +	self->dirty = true;
> +	hit->deleted = true;
> +	self->livelines--;
> +	return 0;
> +}
> +
> +static int lazymanifest_setitem(
> +	lazymanifest *self, PyObject *key, PyObject *value)
> +{
> +	char *path;
> +	Py_ssize_t plen;
> +	PyObject *pyhash;
> +	Py_ssize_t hlen;
> +	char *hash;
> +	char hashextra;
> +	PyObject *pyflags;
> +	char *flags;
> +	Py_ssize_t flen;
> +	size_t dlen;
> +	char *dest;
> +	int i;
> +	line new;
> +	line *hit;
> +	if (!PyString_Check(key)) {
> +		PyErr_Format(PyExc_TypeError,
> +		             "setitem: manifest keys must be a string.");
> +		return -1;
> +	}
> +	if (!value) {
> +		return lazymanifest_delitem(self, key);
> +	}
> +	if (!PyTuple_Check(value) || PyTuple_Size(value) != 2) {
> +		PyErr_Format(PyExc_TypeError,
> +		             "Manifest values must be a tuple of (node, flags).");
> +		return -1;
> +	}
> +	if (PyString_AsStringAndSize(key, &path, &plen) == -1) {
> +		return -1;
> +	}
> +
> +	pyhash = PyTuple_GetItem(value, 0);
> +	if (!PyString_Check(pyhash)) {
> +		PyErr_Format(PyExc_TypeError,
> +		             "node must be a 20-byte string");
> +		return -1;
> +	}
> +	hlen = PyString_Size(pyhash);
> +	/* Some parts of the codebase try and set 21 or 22
> +	 * byte "hash" values in order to perturb things for
> +	 * status. We have to preserve at least the 21st
> +	 * byte. Sigh. If there's a 22nd byte, we drop it on
> +	 * the floor, which works fine.
> +	 */
> +	if (hlen != 20 && hlen != 21 && hlen != 22) {
> +		PyErr_Format(PyExc_TypeError,
> +		             "node must be a 20-byte string");
> +		return -1;
> +	}
> +	hash = PyString_AsString(pyhash);
> +	hashextra = '\0';
> +	if (hlen > 20) {
> +		hashextra = hash[20];
> +	}
> +
> +	pyflags = PyTuple_GetItem(value, 1);
> +	if (!PyString_Check(pyflags) || PyString_Size(pyflags) > 1) {
> +		PyErr_Format(PyExc_TypeError,
> +		             "flags must a 0 or 1 byte string");
> +		return -1;
> +	}
> +	if (PyString_AsStringAndSize(pyflags, &flags, &flen) == -1) {
> +		return -1;
> +	}
> +	/* 3 -> two null bytes and one newline */
> +	dlen = plen + 40 + flen + 3;
> +	dest = malloc(dlen);
> +	if (!dest) {
> +		PyErr_NoMemory();
> +		return -1;
> +	}
> +	memcpy(dest, path, plen + 1);
> +	for (i = 0; i < 20; i++) {
> +		sprintf(dest + plen + 1 + (i * 2), "%02hhx", hash[i]);
> +	}
> +	sprintf(dest + plen + 41, "%s\n", flags);
> +	new.start = dest;
> +	new.len = dlen - 1;
> +	new.hash_suffix = hashextra;
> +	new.from_malloc = true;     /* is `start` a pointer we allocated? */
> +	new.deleted = false;        /* is this entry deleted? */
> +	hit = bsearch(&new, self->lines, self->numlines,
> +	              sizeof(line), &linecmp);
> +	self->dirty = true;
> +	if (hit) {
> +		/* updating a line we already had */
> +		if (hit->from_malloc) {
> +			free(hit->start);
> +		}
> +		if (hit->deleted) {
> +			self->livelines++;
> +		}
> +		*hit = new;
> +	} else {
> +		/* new line */
> +		if (!realloc_if_full(self)) {
> +			PyErr_NoMemory();
> +			return -1;
> +		}
> +		self->lines[self->numlines++] = new;
> +		self->livelines++;
> +		/* TODO: do a binary search and insert rather than
> +		 * append and qsort. Also offer a batch-insert
> +		 * interface, which should be a nice little
> +		 * performance win.
> +		 */
> +		qsort(self->lines, self->numlines, sizeof(line), &linecmp);
> +	}
> +	return 0;
> +}
> +
> +static PyMappingMethods lazymanifest_mapping_methods = {
> +	(lenfunc)lazymanifest_size,             /* mp_length */
> +	(binaryfunc)lazymanifest_getitem,       /* mp_subscript */
> +	(objobjargproc)lazymanifest_setitem,    /* mp_ass_subscript */
> +};
> +
> +/* sequence methods (important or __contains__ builds an iterator */
> +
> +static int lazymanifest_contains(lazymanifest *self, PyObject *key)
> +{
> +	line needle;
> +	line *hit;
> +	if (!PyString_Check(key)) {
> +		PyErr_Format(PyExc_TypeError,
> +		             "contains: manifest keys must be a string.");
> +		return 0;
> +	}
> +	needle.start = PyString_AsString(key);
> +	needle.len = 0;
> +	hit = bsearch(&needle, self->lines, self->numlines, sizeof(line),
> +	              &linecmp);
> +	if (!hit || hit->deleted) {
> +		return 0;
> +	}
> +	return 1;
> +}
> +
> +static PySequenceMethods lazymanifest_seq_meths = {
> +	(lenfunc)lazymanifest_size, /* sq_length */
> +	0, /* sq_concat */
> +	0, /* sq_repeat */
> +	0, /* sq_item */
> +	0, /* sq_slice */
> +	0, /* sq_ass_item */
> +	0, /* sq_ass_slice */
> +	(objobjproc)lazymanifest_contains, /* sq_contains */
> +	0, /* sq_inplace_concat */
> +	0, /* sq_inplace_repeat */
> +};
> +
> +
> +/* Other methods (copy, diff, etc) */
> +static PyTypeObject lazymanifestType;
> +
> +/* If the manifest has changes, build the new manifest text and reindex it. */
> +static int compact(lazymanifest *self) {
> +	int i;
> +	ssize_t need = 0;
> +	char *data;
> +	ssize_t copied = 0;
> +	int real = 0;
> +	line *src, *dst;
> +	char *tofree;
> +	ssize_t c;
> +	PyObject *pydata;
> +	char *realdest;
> +	int err;
> +	Py_ssize_t offset;
> +	line new;
> +	if (!self->dirty)
> +		return 0;
> +	for (i = 0; i < self->numlines; i++) {
> +		if (!self->lines[i].deleted) {
> +			need += self->lines[i].len;
> +		}
> +	}
> +	pydata = PyString_FromStringAndSize(NULL, need);
> +	if (!pydata)
> +		return -1;
> +	data = PyString_AsString(pydata);
> +	if (!data) {
> +		return -1;
> +	}
> +	src = self->lines;
> +	dst = self->lines;
> +	for (i = 0; i < self->numlines; i++, src++) {
> +		tofree = NULL;
> +		if (src->from_malloc) {
> +			tofree = src->start;
> +		}
> +		if (!src->deleted) {
> +			memcpy(data, src->start, src->len);
> +			*dst = *src;
> +			dst->start = data;
> +			dst->from_malloc = false;
> +			data += dst->len;
> +			dst++;
> +		}
> +		free(tofree);
> +	}
> +	Py_DECREF(self->pydata);
> +	self->pydata = pydata;
> +	self->numlines = self->livelines;
> +	self->dirty = false;
> +	return 0;
> +}
> +
> +static PyObject *lazymanifest_text(lazymanifest *self, PyObject *unused_args)
> +{
> +	if (compact(self) != 0) {
> +		PyErr_NoMemory();
> +		return NULL;
> +	}
> +	Py_INCREF(self->pydata);
> +	return self->pydata;
> +}
> +
> +static lazymanifest *lazymanifest_copy(
> +	lazymanifest *self, PyObject *unused_args)
> +{
> +	lazymanifest *copy = NULL;
> +	if (compact(self) != 0) {
> +		goto nomem;
> +	}
> +	copy = PyObject_New(lazymanifest, &lazymanifestType);
> +	if (!copy) {
> +		goto nomem;
> +	}
> +	copy->numlines = self->numlines;
> +	copy->livelines = self->livelines;
> +	copy->dirty = false;
> +	copy->lines = malloc(self->maxlines *sizeof(line));
> +	if (!copy->lines) {
> +		goto nomem;
> +	}
> +	memcpy(copy->lines, self->lines, self->numlines * sizeof(line));
> +	copy->maxlines = self->maxlines;
> +	copy->pydata = self->pydata;
> +	Py_INCREF(copy->pydata);
> +	return copy;
> + nomem:
> +	PyErr_NoMemory();
> +	Py_XDECREF(copy);
> +	return NULL;
> +}
> +
> +static lazymanifest *lazymanifest_filtercopy(
> +	lazymanifest *self, PyObject *matchfn)
> +{
> +	lazymanifest *tmp;
> +	PyObject *arg;
> +	PyObject *arglist;
> +	PyObject *result;
> +	int i;
> +	if (!PyCallable_Check(matchfn)) {
> +		PyErr_SetString(PyExc_TypeError, "matchfn must be callable");
> +		return NULL;
> +	}
> +	/* compact ourselves first to avoid double-frees later when we
> +	 * compact tmp so that it doesn't have random pointers to our
> +	 * underlying data */
> +	compact(self);
> +	tmp = PyObject_New(lazymanifest, &lazymanifestType);
> +	tmp->lines = malloc(self->maxlines * sizeof(line));
> +	tmp->maxlines = self->maxlines;
> +	tmp->livelines = 0;
> +	tmp->numlines = 0;
> +	tmp->pydata = self->pydata;
> +	Py_INCREF(self->pydata);
> +	for (i = 0; i < self->numlines; i++) {
> +		arg = PyString_FromString(self->lines[i].start);
> +		arglist = PyTuple_Pack(1, arg);
> +		result = PyObject_CallObject(matchfn, arglist);
> +		/* if the callback raised an exception, just let it
> +		 * through and give up */
> +		if (!result) {
> +			free(tmp->lines);
> +			tmp->lines = NULL;
> +			Py_DECREF(self->pydata);
> +			return NULL;
> +		}
> +		if (PyObject_IsTrue(result)) {
> +			assert(!(self->lines[i].from_malloc));
> +			tmp->lines[tmp->numlines++] = self->lines[i];
> +			tmp->livelines++;
> +		}
> +		Py_DECREF(arglist);
> +		Py_DECREF(arg);
> +		Py_DECREF(result);
> +	}
> +	compact(tmp);
> +	return tmp;
> +}
> +
> +static PyObject *lazymanifest_diff(lazymanifest *self, PyObject *args)
> +{
> +	lazymanifest *other;
> +	PyObject *pyclean = NULL;
> +	bool clean;
> +	PyObject *emptyTup = NULL, *ret = NULL;
> +	PyObject *es;
> +	int sneedle = 0, oneedle = 0;
> +	line *left;
> +	line *right;
> +	int result;
> +	PyObject *key;
> +	PyObject *tup;
> +	PyObject *outer;
> +	PyObject *r;
> +	if (!PyArg_ParseTuple(args, "O!|O", &lazymanifestType, &other, &pyclean)) {
> +		return NULL;
> +	}
> +	clean = (!pyclean) ? false : PyObject_IsTrue(pyclean);
> +	es = PyString_FromString("");
> +	if (!es) {
> +		goto nomem;
> +	}
> +	emptyTup = PyTuple_Pack(2, Py_None, es);
> +	Py_DECREF(es);
> +	if (!emptyTup) {
> +		goto nomem;
> +	}
> +	ret = PyDict_New();
> +	if (!ret) {
> +		goto nomem;
> +	}
> +	while (sneedle != self->numlines || oneedle != other->numlines) {
> +		left = self->lines + sneedle;
> +		right = other->lines + oneedle;
> +		/* If we're looking at a deleted entry and it's not
> +		 * the end of the manifest, just skip it. */
> +		if (left->deleted && sneedle < self->numlines) {
> +			sneedle++;
> +			continue;
> +		}
> +		if (right->deleted && oneedle < other->numlines) {
> +			oneedle++;
> +			continue;
> +		}
> +		/* if we're at the end of either manifest, then we
> +		 * know the remaining items are adds so we can skip
> +		 * the strcmp. */
> +		if (sneedle == self->numlines) {
> +			result = 1;
> +		} else if (oneedle == other->numlines) {
> +			result = -1;
> +		} else {
> +			result = linecmp(left, right);
> +		}
> +		key = result <= 0 ?
> +			PyString_FromString(left->start) :
> +			PyString_FromString(right->start);
> +		if (!key)
> +			goto nomem;
> +		if (result < 0) {
> +			tup = hashflags(left);
> +			if (!tup) {
> +				goto nomem;
> +			}
> +			outer = PyTuple_Pack(2, tup, emptyTup);
> +			Py_DECREF(tup);
> +			if (!outer) {
> +				goto nomem;
> +			}
> +			PyDict_SetItem(ret, key, outer);
> +			Py_DECREF(outer);
> +			sneedle++;
> +		} else if (result > 0) {
> +			tup = hashflags(right);
> +			if (!tup) {
> +				goto nomem;
> +			}
> +			outer = PyTuple_Pack(2, emptyTup, tup);
> +			Py_DECREF(tup);
> +			if (!outer) {
> +				goto nomem;
> +			}
> +			PyDict_SetItem(ret, key, outer);
> +			Py_DECREF(outer);
> +			oneedle++;
> +		} else {
> +			/* file exists in both manifests */
> +			if (left->len != right->len
> +			    || memcmp(left->start, right->start, left->len)
> +			    || left->hash_suffix != right->hash_suffix) {
> +				PyObject *l = hashflags(left);
> +				if (!l) {
> +					goto nomem;
> +				}
> +				r = hashflags(right);
> +				if (!r) {
> +					Py_DECREF(l);
> +					goto nomem;
> +				}
> +				outer = PyTuple_Pack(2, l, r);
> +				Py_DECREF(l);
> +				Py_DECREF(r);
> +				if (!outer) {
> +					goto nomem;
> +				}
> +				PyDict_SetItem(ret, key, outer);
> +				Py_DECREF(outer);
> +			} else if (clean) {
> +				PyDict_SetItem(ret, key, Py_None);
> +			}
> +			sneedle++;
> +			oneedle++;
> +		}
> +		Py_DECREF(key);
> +	}
> +	Py_DECREF(emptyTup);
> +	return ret;
> + nomem:
> +	PyErr_NoMemory();
> +	Py_XDECREF(ret);
> +	Py_XDECREF(emptyTup);
> +	return NULL;
> +}
> +
> +static PyMethodDef lazymanifest_methods[] = {
> +	{"copy", (PyCFunction)lazymanifest_copy, METH_NOARGS,
> +	 "Make a copy of this lazymanifest."},
> +	{"filtercopy", (PyCFunction)lazymanifest_filtercopy, METH_O,
> +	 "Make a copy of this manifest filtered by matchfn."},
> +	{"diff", (PyCFunction)lazymanifest_diff, METH_VARARGS,
> +	 "Compare this lazymanifest to another one."},
> +	{"text", (PyCFunction)lazymanifest_text, METH_NOARGS,
> +	 "Encode this manifest to text."},
> +	{NULL},
> +};
> +
> +static PyTypeObject lazymanifestType = {
> +	PyObject_HEAD_INIT(NULL)
> +	0,                                                /* ob_size */
> +	"parsers.lazymanifest",                           /* tp_name */
> +	sizeof(lazymanifest),                             /* tp_basicsize */
> +	0,                                                /* tp_itemsize */
> +	(destructor)lazymanifest_dealloc,                 /* tp_dealloc */
> +	0,                                                /* tp_print */
> +	0,                                                /* tp_getattr */
> +	0,                                                /* tp_setattr */
> +	0,                                                /* tp_compare */
> +	0,                                                /* tp_repr */
> +	0,                                                /* tp_as_number */
> +	&lazymanifest_seq_meths,                          /* tp_as_sequence */
> +	&lazymanifest_mapping_methods,                    /* tp_as_mapping */
> +	0,                                                /* tp_hash */
> +	0,                                                /* tp_call */
> +	0,                                                /* tp_str */
> +	0,                                                /* tp_getattro */
> +	0,                                                /* tp_setattro */
> +	0,                                                /* tp_as_buffer */
> +	Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_SEQUENCE_IN, /* tp_flags */
> +	"TODO(augie)",                                    /* tp_doc */
> +	0,                                                /* tp_traverse */
> +	0,                                                /* tp_clear */
> +	0,                                                /* tp_richcompare */
> +	0,                                             /* tp_weaklistoffset */
> +	(getiterfunc)lazymanifest_getiter,                /* tp_iter */
> +	0,                                                /* tp_iternext */
> +	lazymanifest_methods,                             /* tp_methods */
> +	0,                                                /* tp_members */
> +	0,                                                /* tp_getset */
> +	0,                                                /* tp_base */
> +	0,                                                /* tp_dict */
> +	0,                                                /* tp_descr_get */
> +	0,                                                /* tp_descr_set */
> +	0,                                                /* tp_dictoffset */
> +	(initproc)lazymanifest_init,                      /* tp_init */
> +	0,                                                /* tp_alloc */
> +};
> +
> +void manifest_module_init(PyObject * mod)
> +{
> +	lazymanifestType.tp_new = PyType_GenericNew;
> +	if (PyType_Ready(&lazymanifestType) < 0)
> +		return;
> +	Py_INCREF(&lazymanifestType);
> +
> +	PyModule_AddObject(mod, "lazymanifest",
> +	                   (PyObject *)&lazymanifestType);
> +}
> diff --git a/mercurial/parsers.c b/mercurial/parsers.c
> --- a/mercurial/parsers.c
> +++ b/mercurial/parsers.c
> @@ -71,7 +71,7 @@ static inline int hexdigit(const char *p
>   /*
>    * Turn a hex-encoded string into binary.
>    */
> -static PyObject *unhexlify(const char *str, int len)
> +PyObject *unhexlify(const char *str, int len)
>   {
>   	PyObject *ret;
>   	char *d;
> @@ -2233,6 +2233,7 @@ static PyMethodDef methods[] = {
>   };
>   
>   void dirs_module_init(PyObject *mod);
> +void manifest_module_init(PyObject *mod);
>   
>   static void module_init(PyObject *mod)
>   {
> @@ -2247,6 +2248,7 @@ static void module_init(PyObject *mod)
>   	PyModule_AddStringConstant(mod, "versionerrortext", versionerrortext);
>   
>   	dirs_module_init(mod);
> +	manifest_module_init(mod);
>   
>   	indexType.tp_new = PyType_GenericNew;
>   	if (PyType_Ready(&indexType) < 0 ||
> diff --git a/setup.py b/setup.py
> --- a/setup.py
> +++ b/setup.py
> @@ -491,6 +491,7 @@ extmodules = [
>       Extension('mercurial.mpatch', ['mercurial/mpatch.c'],
>                 depends=common_depends),
>       Extension('mercurial.parsers', ['mercurial/dirs.c',
> +                                    'mercurial/manifest.c',
>                                       'mercurial/parsers.c',
>                                       'mercurial/pathencode.c'],
>                 depends=common_depends),
> diff --git a/tests/test-manifest.py b/tests/test-manifest.py
> new file mode 100644
> --- /dev/null
> +++ b/tests/test-manifest.py
> @@ -0,0 +1,209 @@
> +import binascii
> +import unittest
> +import itertools
> +
> +import silenttestrunner
> +
> +from mercurial import parsers
> +
> +HASH_1 = '1' * 40
> +HASH_2 = 'f' * 40
> +HASH_3 = '1234567890abcdef0987654321deadbeef0fcafe'
> +A_SHORT_MANIFEST = (
> +    'bar/baz/qux.py\0%(hash2)s%(flag2)s\n'
> +    'foo\0%(hash1)s%(flag1)s\n'
> +    ) % {'hash1': HASH_1,
> +         'flag1': '',
> +         'hash2': HASH_2,
> +         'flag2': 'l',
> +         }
> +
> +HUGE_MANIFEST_ENTRIES = 200001
> +
> +A_HUGE_MANIFEST = ''.join(sorted(
> +    'file%d\0%s%s\n' % (i, h, f) for i, h, f in
> +    itertools.izip(xrange(200001),
> +                   itertools.cycle((HASH_1, HASH_2)),
> +                   itertools.cycle(('', 'x', 'l')))))
> +
> +class testmanifest(unittest.TestCase):
> +    def testEmptyManifest(self):
> +        m = parsers.lazymanifest('')
> +        self.assertEqual(0, len(m))
> +        self.assertEqual([], list(m))
> +
> +    def testManifest(self):
> +        m = parsers.lazymanifest(A_SHORT_MANIFEST)
> +        want = [
> +            ('bar/baz/qux.py', binascii.unhexlify(HASH_2), 'l'),
> +            ('foo', binascii.unhexlify(HASH_1), ''),
> +            ]
> +        self.assertEqual(len(want), len(m))
> +        self.assertEqual(want, list(m))
> +        self.assertEqual((binascii.unhexlify(HASH_1), ''), m['foo'])
> +        self.assertRaises(KeyError, lambda : m['wat'])
> +        self.assertEqual((binascii.unhexlify(HASH_2), 'l'),
> +                         m['bar/baz/qux.py'])
> +
> +    def testSetItem(self):
> +        want = binascii.unhexlify(HASH_1), ''
> +
> +        m = parsers.lazymanifest('')
> +        m['a'] = want
> +        self.assertIn('a', m)
assertIn is not available in python 2.6 :-(
> +        self.assertEqual(want, m['a'])
> +        self.assertEqual('a\0' + HASH_1 + '\n', m.text())
> +
> +        m = parsers.lazymanifest(A_SHORT_MANIFEST)
> +        m['a'] = want
> +        self.assertEqual(want, m['a'])
> +        self.assertEqual('a\0' + HASH_1 + '\n' + A_SHORT_MANIFEST,
> +                         m.text())
> +        m2 = m.copy()
> +        del m
> +        del m2 # make sure we don't double free() anything
> +
> +    def testCompaction(self):
> +        unhex = binascii.unhexlify
> +        h1, h2 = unhex(HASH_1), unhex(HASH_2)
> +        m = parsers.lazymanifest(A_SHORT_MANIFEST)
> +        m['alpha'] = h1, ''
> +        m['beta'] = h2, ''
> +        del m['foo']
> +        want = 'alpha\0%s\nbar/baz/qux.py\0%sl\nbeta\0%s\n' % (
> +            HASH_1, HASH_2, HASH_2)
> +        self.assertEqual(want, m.text())
> +        self.assertEqual(3, len(m))
> +        self.assertEqual((h1, ''), m['alpha'])
> +        self.assertEqual((h2, ''), m['beta'])
> +        self.assertRaises(KeyError, lambda : m['foo'])
> +        w = [('alpha', h1, ''), ('bar/baz/qux.py', h2, 'l'), ('beta', h2, '')]
> +        self.assertEqual(w, list(m))
> +
> +    def testSetGetNodeSuffix(self):
> +        clean = parsers.lazymanifest(A_SHORT_MANIFEST)
> +        m = parsers.lazymanifest(A_SHORT_MANIFEST)
> +        h, f = m['foo']
> +        want = h + 'a', f
> +        # Merge code wants to set 21-byte fake hashes at times
> +        m['foo'] = want
> +        self.assertEqual(want, m['foo'])
> +        self.assertEqual([('bar/baz/qux.py', binascii.unhexlify(HASH_2), 'l'),
> +                          ('foo', binascii.unhexlify(HASH_1) + 'a', '')],
> +                         list(m))
> +        # Sometimes it even tries a 22-byte fake hash, but we can
> +        # return 21 and it'll work out
> +        m['foo'] = want[0] + '+', f
> +        self.assertEqual(want, m['foo'])
> +        # make sure the suffix survives a copy
> +        m2 = m.filtercopy(lambda x: x == 'foo')
> +        self.assertEqual(want, m2['foo'])
> +        m2 = m.copy()
> +        self.assertEqual(want, m2['foo'])
> +        # suffix with iteration
> +        self.assertEqual([('bar/baz/qux.py', binascii.unhexlify(HASH_2), 'l'),
> +                          ('foo', want[0], '')], list(m))
> +        # shows up in diff
> +        self.assertEqual({'foo': (want, (h, ''))}, m.diff(clean))
> +        self.assertEqual({'foo': ((h, ''), want)}, clean.diff(m))
> +
> +    def testFilterCopyException(self):
> +        m = parsers.lazymanifest(A_SHORT_MANIFEST)
> +        def filt(path):
> +            if path == 'foo':
> +                assert False
> +            return True
> +        self.assertRaises(AssertionError, m.filtercopy, filt)
> +
> +    def testRemoveItem(self):
> +        m = parsers.lazymanifest(A_SHORT_MANIFEST)
> +        del m['foo']
> +        self.assertRaises(KeyError, lambda : m['foo'])
> +        self.assertEqual(1, len(m))
> +        self.assertEqual(1, len(list(m)))
> +
> +    def testManifestDiff(self):
> +        MISSING = (None, '')
> +        addl = 'z-only-in-left\0' + HASH_1 + '\n'
> +        addr = 'z-only-in-right\0' + HASH_2 + 'x\n'
> +        left = parsers.lazymanifest(
> +            A_SHORT_MANIFEST.replace(HASH_1, HASH_3 + 'x') + addl)
> +        right = parsers.lazymanifest(A_SHORT_MANIFEST + addr)
> +        want = {
> +            'foo': ((binascii.unhexlify(HASH_3), 'x'),
> +                    (binascii.unhexlify(HASH_1), '')),
> +            'z-only-in-left': ((binascii.unhexlify(HASH_1), ''), MISSING),
> +            'z-only-in-right': (MISSING, (binascii.unhexlify(HASH_2), 'x')),
> +            }
> +        self.assertEqual(want, left.diff(right))
> +
> +        want = {
> +            'bar/baz/qux.py': (MISSING, (binascii.unhexlify(HASH_2), 'l')),
> +            'foo': (MISSING, (binascii.unhexlify(HASH_3), 'x')),
> +            'z-only-in-left': (MISSING, (binascii.unhexlify(HASH_1), '')),
> +            }
> +        self.assertEqual(want, parsers.lazymanifest('').diff(left))
> +
> +        want = {
> +            'bar/baz/qux.py': ((binascii.unhexlify(HASH_2), 'l'), MISSING),
> +            'foo': ((binascii.unhexlify(HASH_3), 'x'), MISSING),
> +            'z-only-in-left': ((binascii.unhexlify(HASH_1), ''), MISSING),
> +            }
> +        self.assertEqual(want, left.diff(parsers.lazymanifest('')))
> +        copy = right.copy()
> +        del copy['z-only-in-right']
> +        del right['foo']
> +        want = {
> +            'foo': (MISSING, (binascii.unhexlify(HASH_1), '')),
> +            'z-only-in-right': ((binascii.unhexlify(HASH_2), 'x'), MISSING),
> +            }
> +        self.assertEqual(want, right.diff(copy))
> +
> +        short = parsers.lazymanifest(A_SHORT_MANIFEST)
> +        pruned = short.copy()
> +        del pruned['foo']
> +        want = {
> +            'foo': ((binascii.unhexlify(HASH_1), ''), MISSING),
> +            }
> +        self.assertEqual(want, short.diff(pruned))
> +        want = {
> +            'foo': (MISSING, (binascii.unhexlify(HASH_1), '')),
> +            }
> +        self.assertEqual(want, pruned.diff(short))
> +        want = {
> +            'bar/baz/qux.py': None,
> +            'foo': (MISSING, (binascii.unhexlify(HASH_1), '')),
> +            }
> +        self.assertEqual(want, pruned.diff(short, True))
> +
> +    def testReversedLines(self):
> +        backwards = ''.join(
> +            l + '\n' for l in reversed(A_SHORT_MANIFEST.split('\n')) if l)
> +        try:
> +            parsers.lazymanifest(backwards)
> +            self.fail('Should have raised ValueError')
> +        except ValueError, v:
> +            self.assertEqual('Manifest lines not in sorted order.', v.message)
This line and the next two similar lines give off an annoying 
DeprecationWarnings, eg:

$ ./run-tests.py test-manifest.py

+  self.assertEqual('Manifest did not end in a newline.', v.message)

ERROR: test-manifest.py output changed
!
Failed test-manifest.py: output changed
# Ran 1 tests, 0 skipped, 0 warned, 1 failed.
python hash seed: 3186688111

> +
> +    def testNoTerminalNewline(self):
> +        try:
> +            parsers.lazymanifest(A_SHORT_MANIFEST + 'wat')
> +            self.fail('Should have raised ValueError')
> +        except ValueError, v:
> +            self.assertEqual('Manifest did not end in a newline.', v.message)
> +
> +    def testNoNewLineAtAll(self):
> +        try:
> +            parsers.lazymanifest('wat')
> +            self.fail('Should have raised ValueError')
> +        except ValueError, v:
> +            self.assertEqual('Manifest did not end in a newline.', v.message)
> +
> +    def testHugeManifest(self):
> +        m = parsers.lazymanifest(A_HUGE_MANIFEST)
> +        self.assertEqual(HUGE_MANIFEST_ENTRIES, len(m))
> +        self.assertEqual(len(m), len(list(m)))
> +
> +
> +if __name__ == '__main__':
> +    silenttestrunner.main(__name__)

Patch

--- hg/tests/test-manifest.py.out
+++ hg/tests/test-manifest.py.err
@@ -1,0 +1,2 @@ 
+ hg/tests/test-manifest.py:203: DeprecationWarning: 
BaseException.message has been deprecated as of Python 2.6