annotate mercurial/parsers.c @ 21823:925d1bb9a971 stable

repoview: do not crash when localtags refers to non existing revisions

This fixes a crash that may happen when using mercurial 3.0.x.

The _gethiddenblockers function assumed that the output of tags.readlocaltags()
was a dict mapping tags to of valid nodes. However this was not necessarily the
case. When a repository had obsolete revisions and had local tag pointing to a
non existing revision was found, many mercurial commands would crash.

This revision fixes the problem by removing any tags from the output of
tags.readlocaltags() which point to invalid nodes.

We may want to add a warning when this happens (although it might be
annoying to get that warning for every command, possibly even more than once per
command).

A test for this problem has been added to test-obsolete.t. Without this fix the
test would output:

  $ hg tags
  abort: 00changelog.i@3816541e5485: no node!
  [255]

Instead of:

  $ hg tags
  tiptag                             2:3816541e5485
  tip                                2:3816541e5485
  visible                            0:193e9254ce7e

/*
 parsers.c - efficient content parsing

 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.
*/

#include <Python.h>
#include <ctype.h>
#include <stddef.h>
#include <string.h>

#include "util.h"

static char *versionerrortext = "Python minor version mismatch";

static int8_t hextable[256] = {
	-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,
	 0,  1,  2,  3,  4,  5,  6,  7,  8,  9, -1, -1, -1, -1, -1, -1, /* 0-9 */
	-1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1, /* A-F */
	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
	-1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1, /* a-f */
	-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,
	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1
};

static inline int hexdigit(const char *p, Py_ssize_t off)
{
	int8_t val = hextable[(unsigned char)p[off]];

	if (val >= 0) {
		return val;
	}

	PyErr_SetString(PyExc_ValueError, "input contains non-hex character");
	return 0;
}

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

/*
 * This code assumes that a manifest is stitched together with newline
 * ('\n') characters.
 */
static PyObject *parse_manifest(PyObject *self, PyObject *args)
{
	PyObject *mfdict, *fdict;
	char *str, *start, *end;
	int len;

	if (!PyArg_ParseTuple(args, "O!O!s#:parse_manifest",
			      &PyDict_Type, &mfdict,
			      &PyDict_Type, &fdict,
			      &str, &len))
		goto quit;

	start = str;
	end = str + len;
	while (start < end) {
		PyObject *file = NULL, *node = NULL;
		PyObject *flags = NULL;
		char *zero = NULL, *newline = NULL;
		ptrdiff_t nlen;

		zero = memchr(start, '\0', end - start);
		if (!zero) {
			PyErr_SetString(PyExc_ValueError,
					"manifest entry has no separator");
			goto quit;
		}

		newline = memchr(zero + 1, '\n', end - (zero + 1));
		if (!newline) {
			PyErr_SetString(PyExc_ValueError,
					"manifest contains trailing garbage");
			goto quit;
		}

		file = PyBytes_FromStringAndSize(start, zero - start);

		if (!file)
			goto bail;

		nlen = newline - zero - 1;

		node = unhexlify(zero + 1, nlen > 40 ? 40 : (int)nlen);
		if (!node)
			goto bail;

		if (nlen > 40) {
			flags = PyBytes_FromStringAndSize(zero + 41,
							   nlen - 40);
			if (!flags)
				goto bail;

			if (PyDict_SetItem(fdict, file, flags) == -1)
				goto bail;
		}

		if (PyDict_SetItem(mfdict, file, node) == -1)
			goto bail;

		start = newline + 1;

		Py_XDECREF(flags);
		Py_XDECREF(node);
		Py_XDECREF(file);
		continue;
	bail:
		Py_XDECREF(flags);
		Py_XDECREF(node);
		Py_XDECREF(file);
		goto quit;
	}

	Py_INCREF(Py_None);
	return Py_None;
quit:
	return NULL;
}

static PyObject *parse_dirstate(PyObject *self, PyObject *args)
{
	PyObject *dmap, *cmap, *parents = NULL, *ret = NULL;
	PyObject *fname = NULL, *cname = NULL, *entry = NULL;
	char state, *cur, *str, *cpos;
	int mode, size, mtime;
	unsigned int flen;
	int len, pos = 40;

	if (!PyArg_ParseTuple(args, "O!O!s#:parse_dirstate",
			      &PyDict_Type, &dmap,
			      &PyDict_Type, &cmap,
			      &str, &len))
		goto quit;

	/* read parents */
	if (len < 40)
		goto quit;

	parents = Py_BuildValue("s#s#", str, 20, str + 20, 20);
	if (!parents)
		goto quit;

	/* read filenames */
	while (pos >= 40 && pos < len) {
		cur = str + pos;
		/* unpack header */
		state = *cur;
		mode = getbe32(cur + 1);
		size = getbe32(cur + 5);
		mtime = getbe32(cur + 9);
		flen = getbe32(cur + 13);
		pos += 17;
		cur += 17;
		if (flen > len - pos) {
			PyErr_SetString(PyExc_ValueError, "overflow in dirstate");
			goto quit;
		}

		entry = Py_BuildValue("ciii", state, mode, size, mtime);
		if (!entry)
			goto quit;
		PyObject_GC_UnTrack(entry); /* don't waste time with this */

		cpos = memchr(cur, 0, flen);
		if (cpos) {
			fname = PyBytes_FromStringAndSize(cur, cpos - cur);
			cname = PyBytes_FromStringAndSize(cpos + 1,
							   flen - (cpos - cur) - 1);
			if (!fname || !cname ||
			    PyDict_SetItem(cmap, fname, cname) == -1 ||
			    PyDict_SetItem(dmap, fname, entry) == -1)
				goto quit;
			Py_DECREF(cname);
		} else {
			fname = PyBytes_FromStringAndSize(cur, flen);
			if (!fname ||
			    PyDict_SetItem(dmap, fname, entry) == -1)
				goto quit;
		}
		Py_DECREF(fname);
		Py_DECREF(entry);
		fname = cname = entry = NULL;
		pos += flen;
	}

	ret = parents;
	Py_INCREF(ret);
quit:
	Py_XDECREF(fname);
	Py_XDECREF(cname);
	Py_XDECREF(entry);
	Py_XDECREF(parents);
	return ret;
}

static inline int getintat(PyObject *tuple, int off, uint32_t *v)
{
	PyObject *o = PyTuple_GET_ITEM(tuple, off);
	long val;

	if (PyInt_Check(o))
		val = PyInt_AS_LONG(o);
	else if (PyLong_Check(o)) {
		val = PyLong_AsLong(o);
		if (val == -1 && PyErr_Occurred())
			return -1;
	} else {
		PyErr_SetString(PyExc_TypeError, "expected an int or long");
		return -1;
	}
	if (LONG_MAX > INT_MAX && (val > INT_MAX || val < INT_MIN)) {
		PyErr_SetString(PyExc_OverflowError,
				"Python value to large to convert to uint32_t");
		return -1;
	}
	*v = (uint32_t)val;
	return 0;
}

static PyObject *dirstate_unset;

/*
 * Efficiently pack a dirstate object into its on-disk format.
 */
static PyObject *pack_dirstate(PyObject *self, PyObject *args)
{
	PyObject *packobj = NULL;
	PyObject *map, *copymap, *pl;
	Py_ssize_t nbytes, pos, l;
	PyObject *k, *v, *pn;
	char *p, *s;
	double now;

	if (!PyArg_ParseTuple(args, "O!O!Od:pack_dirstate",
			      &PyDict_Type, &map, &PyDict_Type, &copymap,
			      &pl, &now))
		return NULL;

	if (!PySequence_Check(pl) || PySequence_Size(pl) != 2) {
		PyErr_SetString(PyExc_TypeError, "expected 2-element sequence");
		return NULL;
	}

	/* Figure out how much we need to allocate. */
	for (nbytes = 40, pos = 0; PyDict_Next(map, &pos, &k, &v);) {
		PyObject *c;
		if (!PyString_Check(k)) {
			PyErr_SetString(PyExc_TypeError, "expected string key");
			goto bail;
		}
		nbytes += PyString_GET_SIZE(k) + 17;
		c = PyDict_GetItem(copymap, k);
		if (c) {
			if (!PyString_Check(c)) {
				PyErr_SetString(PyExc_TypeError,
						"expected string key");
				goto bail;
			}
			nbytes += PyString_GET_SIZE(c) + 1;
		}
	}

	packobj = PyString_FromStringAndSize(NULL, nbytes);
	if (packobj == NULL)
		goto bail;

	p = PyString_AS_STRING(packobj);

	pn = PySequence_ITEM(pl, 0);
	if (PyString_AsStringAndSize(pn, &s, &l) == -1 || l != 20) {
		PyErr_SetString(PyExc_TypeError, "expected a 20-byte hash");
		goto bail;
	}
	memcpy(p, s, l);
	p += 20;
	pn = PySequence_ITEM(pl, 1);
	if (PyString_AsStringAndSize(pn, &s, &l) == -1 || l != 20) {
		PyErr_SetString(PyExc_TypeError, "expected a 20-byte hash");
		goto bail;
	}
	memcpy(p, s, l);
	p += 20;

	for (pos = 0; PyDict_Next(map, &pos, &k, &v); ) {
		uint32_t mode, size, mtime;
		Py_ssize_t len, l;
		PyObject *o;
		char *s, *t;

		if (!PyTuple_Check(v) || PyTuple_GET_SIZE(v) != 4) {
			PyErr_SetString(PyExc_TypeError, "expected a 4-tuple");
			goto bail;
		}
		o = PyTuple_GET_ITEM(v, 0);
		if (PyString_AsStringAndSize(o, &s, &l) == -1 || l != 1) {
			PyErr_SetString(PyExc_TypeError, "expected one byte");
			goto bail;
		}
		*p++ = *s;
		if (getintat(v, 1, &mode) == -1)
			goto bail;
		if (getintat(v, 2, &size) == -1)
			goto bail;
		if (getintat(v, 3, &mtime) == -1)
			goto bail;
		if (*s == 'n' && mtime == (uint32_t)now) {
			/* See pure/parsers.py:pack_dirstate for why we do
			 * this. */
			if (PyDict_SetItem(map, k, dirstate_unset) == -1)
				goto bail;
			mtime = -1;
		}
		putbe32(mode, p);
		putbe32(size, p + 4);
		putbe32(mtime, p + 8);
		t = p + 12;
		p += 16;
		len = PyString_GET_SIZE(k);
		memcpy(p, PyString_AS_STRING(k), len);
		p += len;
		o = PyDict_GetItem(copymap, k);
		if (o) {
			*p++ = '\0';
			l = PyString_GET_SIZE(o);
			memcpy(p, PyString_AS_STRING(o), l);
			p += l;
			len += l + 1;
		}
		putbe32((uint32_t)len, t);
	}

	pos = p - PyString_AS_STRING(packobj);
	if (pos != nbytes) {
		PyErr_Format(PyExc_SystemError, "bad dirstate size: %ld != %ld",
                             (long)pos, (long)nbytes);
		goto bail;
	}

	return packobj;
bail:
	Py_XDECREF(packobj);
	return NULL;
}

/*
 * A base-16 trie for fast node->rev mapping.
 *
 * Positive value is index of the next node in the trie
 * Negative value is a leaf: -(rev + 1)
 * Zero is empty
 */
typedef struct {
	int children[16];
} nodetree;

/*
 * This class has two behaviours.
 *
 * When used in a list-like way (with integer keys), we decode an
 * entry in a RevlogNG index file on demand. Our last entry is a
 * sentinel, always a nullid.  We have limited support for
 * integer-keyed insert and delete, only at elements right before the
 * sentinel.
 *
 * With string keys, we lazily perform a reverse mapping from node to
 * rev, using a base-16 trie.
 */
typedef struct {
	PyObject_HEAD
	/* Type-specific fields go here. */
	PyObject *data;        /* raw bytes of index */
	PyObject **cache;      /* cached tuples */
	const char **offsets;  /* populated on demand */
	Py_ssize_t raw_length; /* original number of elements */
	Py_ssize_t length;     /* current number of elements */
	PyObject *added;       /* populated on demand */
	PyObject *headrevs;    /* cache, invalidated on changes */
	nodetree *nt;          /* base-16 trie */
	int ntlength;          /* # nodes in use */
	int ntcapacity;        /* # nodes allocated */
	int ntdepth;           /* maximum depth of tree */
	int ntsplits;          /* # splits performed */
	int ntrev;             /* last rev scanned */
	int ntlookups;         /* # lookups */
	int ntmisses;          /* # lookups that miss the cache */
	int inlined;
} indexObject;

static Py_ssize_t index_length(const indexObject *self)
{
	if (self->added == NULL)
		return self->length;
	return self->length + PyList_GET_SIZE(self->added);
}

static PyObject *nullentry;
static const char nullid[20];

static long inline_scan(indexObject *self, const char **offsets);

#if LONG_MAX == 0x7fffffffL
static char *tuple_format = "Kiiiiiis#";
#else
static char *tuple_format = "kiiiiiis#";
#endif

/* A RevlogNG v1 index entry is 64 bytes long. */
static const long v1_hdrsize = 64;

/*
 * Return a pointer to the beginning of a RevlogNG record.
 */
static const char *index_deref(indexObject *self, Py_ssize_t pos)
{
	if (self->inlined && pos > 0) {
		if (self->offsets == NULL) {
			self->offsets = malloc(self->raw_length *
					       sizeof(*self->offsets));
			if (self->offsets == NULL)
				return (const char *)PyErr_NoMemory();
			inline_scan(self, self->offsets);
		}
		return self->offsets[pos];
	}

	return PyString_AS_STRING(self->data) + pos * v1_hdrsize;
}

/*
 * RevlogNG format (all in big endian, data may be inlined):
 *    6 bytes: offset
 *    2 bytes: flags
 *    4 bytes: compressed length
 *    4 bytes: uncompressed length
 *    4 bytes: base revision
 *    4 bytes: link revision
 *    4 bytes: parent 1 revision
 *    4 bytes: parent 2 revision
 *   32 bytes: nodeid (only 20 bytes used)
 */
static PyObject *index_get(indexObject *self, Py_ssize_t pos)
{
	uint64_t offset_flags;
	int comp_len, uncomp_len, base_rev, link_rev, parent_1, parent_2;
	const char *c_node_id;
	const char *data;
	Py_ssize_t length = index_length(self);
	PyObject *entry;

	if (pos < 0)
		pos += length;

	if (pos < 0 || pos >= length) {
		PyErr_SetString(PyExc_IndexError, "revlog index out of range");
		return NULL;
	}

	if (pos == length - 1) {
		Py_INCREF(nullentry);
		return nullentry;
	}

	if (pos >= self->length - 1) {
		PyObject *obj;
		obj = PyList_GET_ITEM(self->added, pos - self->length + 1);
		Py_INCREF(obj);
		return obj;
	}

	if (self->cache) {
		if (self->cache[pos]) {
			Py_INCREF(self->cache[pos]);
			return self->cache[pos];
		}
	} else {
		self->cache = calloc(self->raw_length, sizeof(PyObject *));
		if (self->cache == NULL)
			return PyErr_NoMemory();
	}

	data = index_deref(self, pos);
	if (data == NULL)
		return NULL;

	offset_flags = getbe32(data + 4);
	if (pos == 0) /* mask out version number for the first entry */
		offset_flags &= 0xFFFF;
	else {
		uint32_t offset_high = getbe32(data);
		offset_flags |= ((uint64_t)offset_high) << 32;
	}

	comp_len = getbe32(data + 8);
	uncomp_len = getbe32(data + 12);
	base_rev = getbe32(data + 16);
	link_rev = getbe32(data + 20);
	parent_1 = getbe32(data + 24);
	parent_2 = getbe32(data + 28);
	c_node_id = data + 32;

	entry = Py_BuildValue(tuple_format, offset_flags, comp_len,
			      uncomp_len, base_rev, link_rev,
			      parent_1, parent_2, c_node_id, 20);

	if (entry) {
		PyObject_GC_UnTrack(entry);
		Py_INCREF(entry);
	}

	self->cache[pos] = entry;

	return entry;
}

/*
 * Return the 20-byte SHA of the node corresponding to the given rev.
 */
static const char *index_node(indexObject *self, Py_ssize_t pos)
{
	Py_ssize_t length = index_length(self);
	const char *data;

	if (pos == length - 1 || pos == INT_MAX)
		return nullid;

	if (pos >= length)
		return NULL;

	if (pos >= self->length - 1) {
		PyObject *tuple, *str;
		tuple = PyList_GET_ITEM(self->added, pos - self->length + 1);
		str = PyTuple_GetItem(tuple, 7);
		return str ? PyString_AS_STRING(str) : NULL;
	}

	data = index_deref(self, pos);
	return data ? data + 32 : NULL;
}

static int nt_insert(indexObject *self, const char *node, int rev);

static int node_check(PyObject *obj, char **node, Py_ssize_t *nodelen)
{
	if (PyString_AsStringAndSize(obj, node, nodelen) == -1)
		return -1;
	if (*nodelen == 20)
		return 0;
	PyErr_SetString(PyExc_ValueError, "20-byte hash required");
	return -1;
}

static PyObject *index_insert(indexObject *self, PyObject *args)
{
	PyObject *obj;
	char *node;
	long offset;
	Py_ssize_t len, nodelen;

	if (!PyArg_ParseTuple(args, "lO", &offset, &obj))
		return NULL;

	if (!PyTuple_Check(obj) || PyTuple_GET_SIZE(obj) != 8) {
		PyErr_SetString(PyExc_TypeError, "8-tuple required");
		return NULL;
	}

	if (node_check(PyTuple_GET_ITEM(obj, 7), &node, &nodelen) == -1)
		return NULL;

	len = index_length(self);

	if (offset < 0)
		offset += len;

	if (offset != len - 1) {
		PyErr_SetString(PyExc_IndexError,
				"insert only supported at index -1");
		return NULL;
	}

	if (offset > INT_MAX) {
		PyErr_SetString(PyExc_ValueError,
				"currently only 2**31 revs supported");
		return NULL;
	}

	if (self->added == NULL) {
		self->added = PyList_New(0);
		if (self->added == NULL)
			return NULL;
	}

	if (PyList_Append(self->added, obj) == -1)
		return NULL;

	if (self->nt)
		nt_insert(self, node, (int)offset);

	Py_CLEAR(self->headrevs);
	Py_RETURN_NONE;
}

static void _index_clearcaches(indexObject *self)
{
	if (self->cache) {
		Py_ssize_t i;

		for (i = 0; i < self->raw_length; i++)
			Py_CLEAR(self->cache[i]);
		free(self->cache);
		self->cache = NULL;
	}
	if (self->offsets) {
		free(self->offsets);
		self->offsets = NULL;
	}
	if (self->nt) {
		free(self->nt);
		self->nt = NULL;
	}
	Py_CLEAR(self->headrevs);
}

static PyObject *index_clearcaches(indexObject *self)
{
	_index_clearcaches(self);
	self->ntlength = self->ntcapacity = 0;
	self->ntdepth = self->ntsplits = 0;
	self->ntrev = -1;
	self->ntlookups = self->ntmisses = 0;
	Py_RETURN_NONE;
}

static PyObject *index_stats(indexObject *self)
{
	PyObject *obj = PyDict_New();

	if (obj == NULL)
		return NULL;

#define istat(__n, __d) \
	if (PyDict_SetItemString(obj, __d, PyInt_FromSsize_t(self->__n)) == -1) \
		goto bail;

	if (self->added) {
		Py_ssize_t len = PyList_GET_SIZE(self->added);
		if (PyDict_SetItemString(obj, "index entries added",
					 PyInt_FromSsize_t(len)) == -1)
			goto bail;
	}

	if (self->raw_length != self->length - 1)
		istat(raw_length, "revs on disk");
	istat(length, "revs in memory");
	istat(ntcapacity, "node trie capacity");
	istat(ntdepth, "node trie depth");
	istat(ntlength, "node trie count");
	istat(ntlookups, "node trie lookups");
	istat(ntmisses, "node trie misses");
	istat(ntrev, "node trie last rev scanned");
	istat(ntsplits, "node trie splits");

#undef istat

	return obj;

bail:
	Py_XDECREF(obj);
	return NULL;
}

/*
 * When we cache a list, we want to be sure the caller can't mutate
 * the cached copy.
 */
static PyObject *list_copy(PyObject *list)
{
	Py_ssize_t len = PyList_GET_SIZE(list);
	PyObject *newlist = PyList_New(len);
	Py_ssize_t i;

	if (newlist == NULL)
		return NULL;

	for (i = 0; i < len; i++) {
		PyObject *obj = PyList_GET_ITEM(list, i);
		Py_INCREF(obj);
		PyList_SET_ITEM(newlist, i, obj);
	}

	return newlist;
}

static PyObject *index_headrevs(indexObject *self)
{
	Py_ssize_t i, len, addlen;
	char *nothead = NULL;
	PyObject *heads;

	if (self->headrevs)
		return list_copy(self->headrevs);

	len = index_length(self) - 1;
	heads = PyList_New(0);
	if (heads == NULL)
		goto bail;
	if (len == 0) {
		PyObject *nullid = PyInt_FromLong(-1);
		if (nullid == NULL || PyList_Append(heads, nullid) == -1) {
			Py_XDECREF(nullid);
			goto bail;
		}
		goto done;
	}

	nothead = calloc(len, 1);
	if (nothead == NULL)
		goto bail;

	for (i = 0; i < self->raw_length; i++) {
		const char *data = index_deref(self, i);
		int parent_1 = getbe32(data + 24);
		int parent_2 = getbe32(data + 28);
		if (parent_1 >= 0)
			nothead[parent_1] = 1;
		if (parent_2 >= 0)
			nothead[parent_2] = 1;
	}

	addlen = self->added ? PyList_GET_SIZE(self->added) : 0;

	for (i = 0; i < addlen; i++) {
		PyObject *rev = PyList_GET_ITEM(self->added, i);
		PyObject *p1 = PyTuple_GET_ITEM(rev, 5);
		PyObject *p2 = PyTuple_GET_ITEM(rev, 6);
		long parent_1, parent_2;

		if (!PyInt_Check(p1) || !PyInt_Check(p2)) {
			PyErr_SetString(PyExc_TypeError,
					"revlog parents are invalid");
			goto bail;
		}
		parent_1 = PyInt_AS_LONG(p1);
		parent_2 = PyInt_AS_LONG(p2);
		if (parent_1 >= 0)
			nothead[parent_1] = 1;
		if (parent_2 >= 0)
			nothead[parent_2] = 1;
	}

	for (i = 0; i < len; i++) {
		PyObject *head;

		if (nothead[i])
			continue;
		head = PyInt_FromLong(i);
		if (head == NULL || PyList_Append(heads, head) == -1) {
			Py_XDECREF(head);
			goto bail;
		}
	}

done:
	self->headrevs = heads;
	free(nothead);
	return list_copy(self->headrevs);
bail:
	Py_XDECREF(heads);
	free(nothead);
	return NULL;
}

static inline int nt_level(const char *node, Py_ssize_t level)
{
	int v = node[level>>1];
	if (!(level & 1))
		v >>= 4;
	return v & 0xf;
}

/*
 * Return values:
 *
 *   -4: match is ambiguous (multiple candidates)
 *   -2: not found
 * rest: valid rev
 */
static int nt_find(indexObject *self, const char *node, Py_ssize_t nodelen,
		   int hex)
{
	int (*getnybble)(const char *, Py_ssize_t) = hex ? hexdigit : nt_level;
	int level, maxlevel, off;

	if (nodelen == 20 && node[0] == '\0' && memcmp(node, nullid, 20) == 0)
		return -1;

	if (self->nt == NULL)
		return -2;

	if (hex)
		maxlevel = nodelen > 40 ? 40 : (int)nodelen;
	else
		maxlevel = nodelen > 20 ? 40 : ((int)nodelen * 2);

	for (level = off = 0; level < maxlevel; level++) {
		int k = getnybble(node, level);
		nodetree *n = &self->nt[off];
		int v = n->children[k];

		if (v < 0) {
			const char *n;
			Py_ssize_t i;

			v = -v - 1;
			n = index_node(self, v);
			if (n == NULL)
				return -2;
			for (i = level; i < maxlevel; i++)
				if (getnybble(node, i) != nt_level(n, i))
					return -2;
			return v;
		}
		if (v == 0)
			return -2;
		off = v;
	}
	/* multiple matches against an ambiguous prefix */
	return -4;
}

static int nt_new(indexObject *self)
{
	if (self->ntlength == self->ntcapacity) {
		self->ntcapacity *= 2;
		self->nt = realloc(self->nt,
				   self->ntcapacity * sizeof(nodetree));
		if (self->nt == NULL) {
			PyErr_SetString(PyExc_MemoryError, "out of memory");
			return -1;
		}
		memset(&self->nt[self->ntlength], 0,
		       sizeof(nodetree) * (self->ntcapacity - self->ntlength));
	}
	return self->ntlength++;
}

static int nt_insert(indexObject *self, const char *node, int rev)
{
	int level = 0;
	int off = 0;

	while (level < 40) {
		int k = nt_level(node, level);
		nodetree *n;
		int v;

		n = &self->nt[off];
		v = n->children[k];

		if (v == 0) {
			n->children[k] = -rev - 1;
			return 0;
		}
		if (v < 0) {
			const char *oldnode = index_node(self, -v - 1);
			int noff;

			if (!oldnode || !memcmp(oldnode, node, 20)) {
				n->children[k] = -rev - 1;
				return 0;
			}
			noff = nt_new(self);
			if (noff == -1)
				return -1;
			/* self->nt may have been changed by realloc */
			self->nt[off].children[k] = noff;
			off = noff;
			n = &self->nt[off];
			n->children[nt_level(oldnode, ++level)] = v;
			if (level > self->ntdepth)
				self->ntdepth = level;
			self->ntsplits += 1;
		} else {
			level += 1;
			off = v;
		}
	}

	return -1;
}

static int nt_init(indexObject *self)
{
	if (self->nt == NULL) {
		if (self->raw_length > INT_MAX) {
			PyErr_SetString(PyExc_ValueError, "overflow in nt_init");
			return -1;
		}
		self->ntcapacity = self->raw_length < 4
			? 4 : (int)self->raw_length / 2;

		self->nt = calloc(self->ntcapacity, sizeof(nodetree));
		if (self->nt == NULL) {
			PyErr_NoMemory();
			return -1;
		}
		self->ntlength = 1;
		self->ntrev = (int)index_length(self) - 1;
		self->ntlookups = 1;
		self->ntmisses = 0;
		if (nt_insert(self, nullid, INT_MAX) == -1)
			return -1;
	}
	return 0;
}

/*
 * Return values:
 *
 *   -3: error (exception set)
 *   -2: not found (no exception set)
 * rest: valid rev
 */
static int index_find_node(indexObject *self,
			   const char *node, Py_ssize_t nodelen)
{
	int rev;

	self->ntlookups++;
	rev = nt_find(self, node, nodelen, 0);
	if (rev >= -1)
		return rev;

	if (nt_init(self) == -1)
		return -3;

	/*
	 * For the first handful of lookups, we scan the entire index,
	 * and cache only the matching nodes. This optimizes for cases
	 * like "hg tip", where only a few nodes are accessed.
	 *
	 * After that, we cache every node we visit, using a single
	 * scan amortized over multiple lookups.  This gives the best
	 * bulk performance, e.g. for "hg log".
	 */
	if (self->ntmisses++ < 4) {
		for (rev = self->ntrev - 1; rev >= 0; rev--) {
			const char *n = index_node(self, rev);
			if (n == NULL)
				return -2;
			if (memcmp(node, n, nodelen > 20 ? 20 : nodelen) == 0) {
				if (nt_insert(self, n, rev) == -1)
					return -3;
				break;
			}
		}
	} else {
		for (rev = self->ntrev - 1; rev >= 0; rev--) {
			const char *n = index_node(self, rev);
			if (n == NULL) {
				self->ntrev = rev + 1;
				return -2;
			}
			if (nt_insert(self, n, rev) == -1) {
				self->ntrev = rev + 1;
				return -3;
			}
			if (memcmp(node, n, nodelen > 20 ? 20 : nodelen) == 0) {
				break;
			}
		}
		self->ntrev = rev;
	}

	if (rev >= 0)
		return rev;
	return -2;
}

static PyObject *raise_revlog_error(void)
{
	static PyObject *errclass;
	PyObject *mod = NULL, *errobj;

	if (errclass == NULL) {
		PyObject *dict;

		mod = PyImport_ImportModule("mercurial.error");
		if (mod == NULL)
			goto classfail;

		dict = PyModule_GetDict(mod);
		if (dict == NULL)
			goto classfail;

		errclass = PyDict_GetItemString(dict, "RevlogError");
		if (errclass == NULL) {
			PyErr_SetString(PyExc_SystemError,
					"could not find RevlogError");
			goto classfail;
		}
		Py_INCREF(errclass);
	}

	errobj = PyObject_CallFunction(errclass, NULL);
	if (errobj == NULL)
		return NULL;
	PyErr_SetObject(errclass, errobj);
	return errobj;

classfail:
	Py_XDECREF(mod);
	return NULL;
}

static PyObject *index_getitem(indexObject *self, PyObject *value)
{
	char *node;
	Py_ssize_t nodelen;
	int rev;

	if (PyInt_Check(value))
		return index_get(self, PyInt_AS_LONG(value));

	if (node_check(value, &node, &nodelen) == -1)
		return NULL;
	rev = index_find_node(self, node, nodelen);
	if (rev >= -1)
		return PyInt_FromLong(rev);
	if (rev == -2)
		raise_revlog_error();
	return NULL;
}

static int nt_partialmatch(indexObject *self, const char *node,
			   Py_ssize_t nodelen)
{
	int rev;

	if (nt_init(self) == -1)
		return -3;

	if (self->ntrev > 0) {
		/* ensure that the radix tree is fully populated */
		for (rev = self->ntrev - 1; rev >= 0; rev--) {
			const char *n = index_node(self, rev);
			if (n == NULL)
				return -2;
			if (nt_insert(self, n, rev) == -1)
				return -3;
		}
		self->ntrev = rev;
	}

	return nt_find(self, node, nodelen, 1);
}

static PyObject *index_partialmatch(indexObject *self, PyObject *args)
{
	const char *fullnode;
	int nodelen;
	char *node;
	int rev, i;

	if (!PyArg_ParseTuple(args, "s#", &node, &nodelen))
		return NULL;

	if (nodelen < 4) {
		PyErr_SetString(PyExc_ValueError, "key too short");
		return NULL;
	}

	if (nodelen > 40) {
		PyErr_SetString(PyExc_ValueError, "key too long");
		return NULL;
	}

	for (i = 0; i < nodelen; i++)
		hexdigit(node, i);
	if (PyErr_Occurred()) {
		/* input contains non-hex characters */
		PyErr_Clear();
		Py_RETURN_NONE;
	}

	rev = nt_partialmatch(self, node, nodelen);

	switch (rev) {
	case -4:
		raise_revlog_error();
	case -3:
		return NULL;
	case -2:
		Py_RETURN_NONE;
	case -1:
		return PyString_FromStringAndSize(nullid, 20);
	}

	fullnode = index_node(self, rev);
	if (fullnode == NULL) {
		PyErr_Format(PyExc_IndexError,
			     "could not access rev %d", rev);
		return NULL;
	}
	return PyString_FromStringAndSize(fullnode, 20);
}

static PyObject *index_m_get(indexObject *self, PyObject *args)
{
	Py_ssize_t nodelen;
	PyObject *val;
	char *node;
	int rev;

	if (!PyArg_ParseTuple(args, "O", &val))
		return NULL;
	if (node_check(val, &node, &nodelen) == -1)
		return NULL;
	rev = index_find_node(self, node, nodelen);
	if (rev ==  -3)
		return NULL;
	if (rev == -2)
		Py_RETURN_NONE;
	return PyInt_FromLong(rev);
}

static int index_contains(indexObject *self, PyObject *value)
{
	char *node;
	Py_ssize_t nodelen;

	if (PyInt_Check(value)) {
		long rev = PyInt_AS_LONG(value);
		return rev >= -1 && rev < index_length(self);
	}

	if (node_check(value, &node, &nodelen) == -1)
		return -1;

	switch (index_find_node(self, node, nodelen)) {
	case -3:
		return -1;
	case -2:
		return 0;
	default:
		return 1;
	}
}

static inline void index_get_parents(indexObject *self, int rev, int *ps)
{
	if (rev >= self->length - 1) {
		PyObject *tuple = PyList_GET_ITEM(self->added,
						  rev - self->length + 1);
		ps[0] = (int)PyInt_AS_LONG(PyTuple_GET_ITEM(tuple, 5));
		ps[1] = (int)PyInt_AS_LONG(PyTuple_GET_ITEM(tuple, 6));
	} else {
		const char *data = index_deref(self, rev);
		ps[0] = getbe32(data + 24);
		ps[1] = getbe32(data + 28);
	}
}

typedef uint64_t bitmask;

/*
 * Given a disjoint set of revs, return all candidates for the
 * greatest common ancestor. In revset notation, this is the set
 * "heads(::a and ::b and ...)"
 */
static PyObject *find_gca_candidates(indexObject *self, const int *revs,
				     int revcount)
{
	const bitmask allseen = (1ull << revcount) - 1;
	const bitmask poison = 1ull << revcount;
	PyObject *gca = PyList_New(0);
	int i, v, interesting;
	int maxrev = -1;
	long sp;
	bitmask *seen;

	if (gca == NULL)
		return PyErr_NoMemory();

	for (i = 0; i < revcount; i++) {
		if (revs[i] > maxrev)
			maxrev = revs[i];
	}

	seen = calloc(sizeof(*seen), maxrev + 1);
	if (seen == NULL) {
		Py_DECREF(gca);
		return PyErr_NoMemory();
	}

	for (i = 0; i < revcount; i++)
		seen[revs[i]] = 1ull << i;

	interesting = revcount;

	for (v = maxrev; v >= 0 && interesting; v--) {
		long sv = seen[v];
		int parents[2];

		if (!sv)
			continue;

		if (sv < poison) {
			interesting -= 1;
			if (sv == allseen) {
				PyObject *obj = PyInt_FromLong(v);
				if (obj == NULL)
					goto bail;
				if (PyList_Append(gca, obj) == -1) {
					Py_DECREF(obj);
					goto bail;
				}
				sv |= poison;
				for (i = 0; i < revcount; i++) {
					if (revs[i] == v)
						goto done;
				}
			}
		}
		index_get_parents(self, v, parents);

		for (i = 0; i < 2; i++) {
			int p = parents[i];
			if (p == -1)
				continue;
			sp = seen[p];
			if (sv < poison) {
				if (sp == 0) {
					seen[p] = sv;
					interesting++;
				}
				else if (sp != sv)
					seen[p] |= sv;
			} else {
				if (sp && sp < poison)
					interesting--;
				seen[p] = sv;
			}
		}
	}

done:
	free(seen);
	return gca;
bail:
	free(seen);
	Py_XDECREF(gca);
	return NULL;
}

/*
 * Given a disjoint set of revs, return the subset with the longest
 * path to the root.
 */
static PyObject *find_deepest(indexObject *self, PyObject *revs)
{
	const Py_ssize_t revcount = PyList_GET_SIZE(revs);
	static const Py_ssize_t capacity = 24;
	int *depth, *interesting = NULL;
	int i, j, v, ninteresting;
	PyObject *dict = NULL, *keys = NULL;
	long *seen = NULL;
	int maxrev = -1;
	long final;

	if (revcount > capacity) {
		PyErr_Format(PyExc_OverflowError,
			     "bitset size (%ld) > capacity (%ld)",
			     (long)revcount, (long)capacity);
		return NULL;
	}

	for (i = 0; i < revcount; i++) {
		int n = (int)PyInt_AsLong(PyList_GET_ITEM(revs, i));
		if (n > maxrev)
			maxrev = n;
	}

	depth = calloc(sizeof(*depth), maxrev + 1);
	if (depth == NULL)
		return PyErr_NoMemory();

	seen = calloc(sizeof(*seen), maxrev + 1);
	if (seen == NULL) {
		PyErr_NoMemory();
		goto bail;
	}

	interesting = calloc(sizeof(*interesting), 2 << revcount);
	if (interesting == NULL) {
		PyErr_NoMemory();
		goto bail;
	}

	if (PyList_Sort(revs) == -1)
		goto bail;

	for (i = 0; i < revcount; i++) {
		int n = (int)PyInt_AsLong(PyList_GET_ITEM(revs, i));
		long b = 1l << i;
		depth[n] = 1;
		seen[n] = b;
		interesting[b] = 1;
	}

	ninteresting = (int)revcount;

	for (v = maxrev; v >= 0 && ninteresting > 1; v--) {
		int dv = depth[v];
		int parents[2];
		long sv;

		if (dv == 0)
			continue;

		sv = seen[v];
		index_get_parents(self, v, parents);

		for (i = 0; i < 2; i++) {
			int p = parents[i];
			long nsp, sp;
			int dp;

			if (p == -1)
				continue;

			dp = depth[p];
			nsp = sp = seen[p];
			if (dp <= dv) {
				depth[p] = dv + 1;
				if (sp != sv) {
					interesting[sv] += 1;
					nsp = seen[p] = sv;
					if (sp) {
						interesting[sp] -= 1;
						if (interesting[sp] == 0)
							ninteresting -= 1;
					}
				}
			}
			else if (dv == dp - 1) {
				nsp = sp | sv;
				if (nsp == sp)
					continue;
				seen[p] = nsp;
				interesting[sp] -= 1;
				if (interesting[sp] == 0 && interesting[nsp] > 0)
					ninteresting -= 1;
				interesting[nsp] += 1;
			}
		}
		interesting[sv] -= 1;
		if (interesting[sv] == 0)
			ninteresting -= 1;
	}

	final = 0;
	j = ninteresting;
	for (i = 0; i < (int)(2 << revcount) && j > 0; i++) {
		if (interesting[i] == 0)
			continue;
		final |= i;
		j -= 1;
	}
	if (final == 0) {
		keys = PyList_New(0);
		goto bail;
	}

	dict = PyDict_New();
	if (dict == NULL)
		goto bail;

	for (i = 0; i < revcount; i++) {
		PyObject *key;

		if ((final & (1 << i)) == 0)
			continue;

		key = PyList_GET_ITEM(revs, i);
		Py_INCREF(key);
		Py_INCREF(Py_None);
		if (PyDict_SetItem(dict, key, Py_None) == -1) {
			Py_DECREF(key);
			Py_DECREF(Py_None);
			goto bail;
		}
	}

	keys = PyDict_Keys(dict);

bail:
	free(depth);
	free(seen);
	free(interesting);
	Py_XDECREF(dict);

	return keys;
}

/*
 * Given a (possibly overlapping) set of revs, return the greatest
 * common ancestors: those with the longest path to the root.
 */
static PyObject *index_ancestors(indexObject *self, PyObject *args)
{
	PyObject *ret = NULL, *gca = NULL;
	Py_ssize_t argcount, i, len;
	bitmask repeat = 0;
	int revcount = 0;
	int *revs;

	argcount = PySequence_Length(args);
	revs = malloc(argcount * sizeof(*revs));
	if (argcount > 0 && revs == NULL)
		return PyErr_NoMemory();
	len = index_length(self) - 1;

	for (i = 0; i < argcount; i++) {
		static const int capacity = 24;
		PyObject *obj = PySequence_GetItem(args, i);
		bitmask x;
		long val;

		if (!PyInt_Check(obj)) {
			PyErr_SetString(PyExc_TypeError,
					"arguments must all be ints");
			goto bail;
		}
		val = PyInt_AsLong(obj);
		if (val == -1) {
			ret = PyList_New(0);
			goto done;
		}
		if (val < 0 || val >= len) {
			PyErr_SetString(PyExc_IndexError,
					"index out of range");
			goto bail;
		}
		/* this cheesy bloom filter lets us avoid some more
		 * expensive duplicate checks in the common set-is-disjoint
		 * case */
		x = 1ull << (val & 0x3f);
		if (repeat & x) {
			int k;
			for (k = 0; k < revcount; k++) {
				if (val == revs[k])
					goto duplicate;
			}
		}
		else repeat |= x;
		if (revcount >= capacity) {
			PyErr_Format(PyExc_OverflowError,
				     "bitset size (%d) > capacity (%d)",
				     revcount, capacity);
			goto bail;
		}
		revs[revcount++] = (int)val;
	duplicate:;
	}

	if (revcount == 0) {
		ret = PyList_New(0);
		goto done;
	}
	if (revcount == 1) {
		PyObject *obj;
		ret = PyList_New(1);
		if (ret == NULL)
			goto bail;
		obj = PyInt_FromLong(revs[0]);
		if (obj == NULL)
			goto bail;
		PyList_SET_ITEM(ret, 0, obj);
		goto done;
	}

	gca = find_gca_candidates(self, revs, revcount);
	if (gca == NULL)
		goto bail;

	if (PyList_GET_SIZE(gca) <= 1) {
		ret = gca;
		Py_INCREF(gca);
	}
	else ret = find_deepest(self, gca);

done:
	free(revs);
	Py_XDECREF(gca);

	return ret;

bail:
	free(revs);
	Py_XDECREF(gca);
	Py_XDECREF(ret);
	return NULL;
}

/*
 * Given a (possibly overlapping) set of revs, return all the
 * common ancestors heads: heads(::args[0] and ::a[1] and ...)
 */
static PyObject *index_commonancestorsheads(indexObject *self, PyObject *args)
{
	PyObject *ret = NULL;
	Py_ssize_t argcount, i, len;
	bitmask repeat = 0;
	int revcount = 0;
	int *revs;

	argcount = PySequence_Length(args);
	revs = malloc(argcount * sizeof(*revs));
	if (argcount > 0 && revs == NULL)
		return PyErr_NoMemory();
	len = index_length(self) - 1;

	for (i = 0; i < argcount; i++) {
		static const int capacity = 24;
		PyObject *obj = PySequence_GetItem(args, i);
		bitmask x;
		long val;

		if (!PyInt_Check(obj)) {
			PyErr_SetString(PyExc_TypeError,
					"arguments must all be ints");
			goto bail;
		}
		val = PyInt_AsLong(obj);
		if (val == -1) {
			ret = PyList_New(0);
			goto done;
		}
		if (val < 0 || val >= len) {
			PyErr_SetString(PyExc_IndexError,
					"index out of range");
			goto bail;
		}
		/* this cheesy bloom filter lets us avoid some more
		 * expensive duplicate checks in the common set-is-disjoint
		 * case */
		x = 1ull << (val & 0x3f);
		if (repeat & x) {
			int k;
			for (k = 0; k < revcount; k++) {
				if (val == revs[k])
					goto duplicate;
			}
		}
		else repeat |= x;
		if (revcount >= capacity) {
			PyErr_Format(PyExc_OverflowError,
				     "bitset size (%d) > capacity (%d)",
				     revcount, capacity);
			goto bail;
		}
		revs[revcount++] = (int)val;
	duplicate:;
	}

	if (revcount == 0) {
		ret = PyList_New(0);
		goto done;
	}
	if (revcount == 1) {
		PyObject *obj;
		ret = PyList_New(1);
		if (ret == NULL)
			goto bail;
		obj = PyInt_FromLong(revs[0]);
		if (obj == NULL)
			goto bail;
		PyList_SET_ITEM(ret, 0, obj);
		goto done;
	}

	ret = find_gca_candidates(self, revs, revcount);
	if (ret == NULL)
		goto bail;

done:
	free(revs);
	return ret;

bail:
	free(revs);
	Py_XDECREF(ret);
	return NULL;
}

/*
 * Invalidate any trie entries introduced by added revs.
 */
static void nt_invalidate_added(indexObject *self, Py_ssize_t start)
{
	Py_ssize_t i, len = PyList_GET_SIZE(self->added);

	for (i = start; i < len; i++) {
		PyObject *tuple = PyList_GET_ITEM(self->added, i);
		PyObject *node = PyTuple_GET_ITEM(tuple, 7);

		nt_insert(self, PyString_AS_STRING(node), -1);
	}

	if (start == 0)
		Py_CLEAR(self->added);
}

/*
 * Delete a numeric range of revs, which must be at the end of the
 * range, but exclude the sentinel nullid entry.
 */
static int index_slice_del(indexObject *self, PyObject *item)
{
	Py_ssize_t start, stop, step, slicelength;
	Py_ssize_t length = index_length(self);
	int ret = 0;

	if (PySlice_GetIndicesEx((PySliceObject*)item, length,
				 &start, &stop, &step, &slicelength) < 0)
		return -1;

	if (slicelength <= 0)
		return 0;

	if ((step < 0 && start < stop) || (step > 0 && start > stop))
		stop = start;

	if (step < 0) {
		stop = start + 1;
		start = stop + step*(slicelength - 1) - 1;
		step = -step;
	}

	if (step != 1) {
		PyErr_SetString(PyExc_ValueError,
				"revlog index delete requires step size of 1");
		return -1;
	}

	if (stop != length - 1) {
		PyErr_SetString(PyExc_IndexError,
				"revlog index deletion indices are invalid");
		return -1;
	}

	if (start < self->length - 1) {
		if (self->nt) {
			Py_ssize_t i;

			for (i = start + 1; i < self->length - 1; i++) {
				const char *node = index_node(self, i);

				if (node)
					nt_insert(self, node, -1);
			}
			if (self->added)
				nt_invalidate_added(self, 0);
			if (self->ntrev > start)
				self->ntrev = (int)start;
		}
		self->length = start + 1;
		if (start < self->raw_length) {
			if (self->cache) {
				Py_ssize_t i;
				for (i = start; i < self->raw_length; i++)
					Py_CLEAR(self->cache[i]);
			}
			self->raw_length = start;
		}
		goto done;
	}

	if (self->nt) {
		nt_invalidate_added(self, start - self->length + 1);
		if (self->ntrev > start)
			self->ntrev = (int)start;
	}
	if (self->added)
		ret = PyList_SetSlice(self->added, start - self->length + 1,
				      PyList_GET_SIZE(self->added), NULL);
done:
	Py_CLEAR(self->headrevs);
	return ret;
}

/*
 * Supported ops:
 *
 * slice deletion
 * string assignment (extend node->rev mapping)
 * string deletion (shrink node->rev mapping)
 */
static int index_assign_subscript(indexObject *self, PyObject *item,
				  PyObject *value)
{
	char *node;
	Py_ssize_t nodelen;
	long rev;

	if (PySlice_Check(item) && value == NULL)
		return index_slice_del(self, item);

	if (node_check(item, &node, &nodelen) == -1)
		return -1;

	if (value == NULL)
		return self->nt ? nt_insert(self, node, -1) : 0;
	rev = PyInt_AsLong(value);
	if (rev > INT_MAX || rev < 0) {
		if (!PyErr_Occurred())
			PyErr_SetString(PyExc_ValueError, "rev out of range");
		return -1;
	}
	return nt_insert(self, node, (int)rev);
}

/*
 * Find all RevlogNG entries in an index that has inline data. Update
 * the optional "offsets" table with those entries.
 */
static long inline_scan(indexObject *self, const char **offsets)
{
	const char *data = PyString_AS_STRING(self->data);
	Py_ssize_t pos = 0;
	Py_ssize_t end = PyString_GET_SIZE(self->data);
	long incr = v1_hdrsize;
	Py_ssize_t len = 0;

	while (pos + v1_hdrsize <= end && pos >= 0) {
		uint32_t comp_len;
		/* 3rd element of header is length of compressed inline data */
		comp_len = getbe32(data + pos + 8);
		incr = v1_hdrsize + comp_len;
		if (offsets)
			offsets[len] = data + pos;
		len++;
		pos += incr;
	}

	if (pos != end) {
		if (!PyErr_Occurred())
			PyErr_SetString(PyExc_ValueError, "corrupt index file");
		return -1;
	}

	return len;
}

static int index_init(indexObject *self, PyObject *args)
{
	PyObject *data_obj, *inlined_obj;
	Py_ssize_t size;

	/* Initialize before argument-checking to avoid index_dealloc() crash. */
	self->raw_length = 0;
	self->added = NULL;
	self->cache = NULL;
	self->data = NULL;
	self->headrevs = NULL;
	self->nt = NULL;
	self->offsets = NULL;

	if (!PyArg_ParseTuple(args, "OO", &data_obj, &inlined_obj))
		return -1;
	if (!PyString_Check(data_obj)) {
		PyErr_SetString(PyExc_TypeError, "data is not a string");
		return -1;
	}
	size = PyString_GET_SIZE(data_obj);

	self->inlined = inlined_obj && PyObject_IsTrue(inlined_obj);
	self->data = data_obj;

	self->ntlength = self->ntcapacity = 0;
	self->ntdepth = self->ntsplits = 0;
	self->ntlookups = self->ntmisses = 0;
	self->ntrev = -1;
	Py_INCREF(self->data);

	if (self->inlined) {
		long len = inline_scan(self, NULL);
		if (len == -1)
			goto bail;
		self->raw_length = len;
		self->length = len + 1;
	} else {
		if (size % v1_hdrsize) {
			PyErr_SetString(PyExc_ValueError, "corrupt index file");
			goto bail;
		}
		self->raw_length = size / v1_hdrsize;
		self->length = self->raw_length + 1;
	}

	return 0;
bail:
	return -1;
}

static PyObject *index_nodemap(indexObject *self)
{
	Py_INCREF(self);
	return (PyObject *)self;
}

static void index_dealloc(indexObject *self)
{
	_index_clearcaches(self);
	Py_XDECREF(self->data);
	Py_XDECREF(self->added);
	PyObject_Del(self);
}

static PySequenceMethods index_sequence_methods = {
	(lenfunc)index_length,   /* sq_length */
	0,                       /* sq_concat */
	0,                       /* sq_repeat */
	(ssizeargfunc)index_get, /* sq_item */
	0,                       /* sq_slice */
	0,                       /* sq_ass_item */
	0,                       /* sq_ass_slice */
	(objobjproc)index_contains, /* sq_contains */
};

static PyMappingMethods index_mapping_methods = {
	(lenfunc)index_length,                 /* mp_length */
	(binaryfunc)index_getitem,             /* mp_subscript */
	(objobjargproc)index_assign_subscript, /* mp_ass_subscript */
};

static PyMethodDef index_methods[] = {
	{"ancestors", (PyCFunction)index_ancestors, METH_VARARGS,
	 "return the gca set of the given revs"},
	{"commonancestorsheads", (PyCFunction)index_commonancestorsheads,
	  METH_VARARGS,
	  "return the heads of the common ancestors of the given revs"},
	{"clearcaches", (PyCFunction)index_clearcaches, METH_NOARGS,
	 "clear the index caches"},
	{"get", (PyCFunction)index_m_get, METH_VARARGS,
	 "get an index entry"},
	{"headrevs", (PyCFunction)index_headrevs, METH_NOARGS,
	 "get head revisions"},
	{"insert", (PyCFunction)index_insert, METH_VARARGS,
	 "insert an index entry"},
	{"partialmatch", (PyCFunction)index_partialmatch, METH_VARARGS,
	 "match a potentially ambiguous node ID"},
	{"stats", (PyCFunction)index_stats, METH_NOARGS,
	 "stats for the index"},
	{NULL} /* Sentinel */
};

static PyGetSetDef index_getset[] = {
	{"nodemap", (getter)index_nodemap, NULL, "nodemap", NULL},
	{NULL} /* Sentinel */
};

static PyTypeObject indexType = {
	PyObject_HEAD_INIT(NULL)
	0,                         /* ob_size */
	"parsers.index",           /* tp_name */
	sizeof(indexObject),       /* tp_basicsize */
	0,                         /* tp_itemsize */
	(destructor)index_dealloc, /* tp_dealloc */
	0,                         /* tp_print */
	0,                         /* tp_getattr */
	0,                         /* tp_setattr */
	0,                         /* tp_compare */
	0,                         /* tp_repr */
	0,                         /* tp_as_number */
	&index_sequence_methods,   /* tp_as_sequence */
	&index_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,        /* tp_flags */
	"revlog index",            /* tp_doc */
	0,                         /* tp_traverse */
	0,                         /* tp_clear */
	0,                         /* tp_richcompare */
	0,                         /* tp_weaklistoffset */
	0,                         /* tp_iter */
	0,                         /* tp_iternext */
	index_methods,             /* tp_methods */
	0,                         /* tp_members */
	index_getset,              /* tp_getset */
	0,                         /* tp_base */
	0,                         /* tp_dict */
	0,                         /* tp_descr_get */
	0,                         /* tp_descr_set */
	0,                         /* tp_dictoffset */
	(initproc)index_init,      /* tp_init */
	0,                         /* tp_alloc */
};

/*
 * returns a tuple of the form (index, index, cache) with elements as
 * follows:
 *
 * index: an index object that lazily parses RevlogNG records
 * cache: if data is inlined, a tuple (index_file_content, 0), else None
 *
 * added complications are for backwards compatibility
 */
static PyObject *parse_index2(PyObject *self, PyObject *args)
{
	PyObject *tuple = NULL, *cache = NULL;
	indexObject *idx;
	int ret;

	idx = PyObject_New(indexObject, &indexType);
	if (idx == NULL)
		goto bail;

	ret = index_init(idx, args);
	if (ret == -1)
		goto bail;

	if (idx->inlined) {
		cache = Py_BuildValue("iO", 0, idx->data);
		if (cache == NULL)
			goto bail;
	} else {
		cache = Py_None;
		Py_INCREF(cache);
	}

	tuple = Py_BuildValue("NN", idx, cache);
	if (!tuple)
		goto bail;
	return tuple;

bail:
	Py_XDECREF(idx);
	Py_XDECREF(cache);
	Py_XDECREF(tuple);
	return NULL;
}

static char parsers_doc[] = "Efficient content parsing.";

PyObject *encodedir(PyObject *self, PyObject *args);
PyObject *pathencode(PyObject *self, PyObject *args);
PyObject *lowerencode(PyObject *self, PyObject *args);

static PyMethodDef methods[] = {
	{"pack_dirstate", pack_dirstate, METH_VARARGS, "pack a dirstate\n"},
	{"parse_manifest", parse_manifest, METH_VARARGS, "parse a manifest\n"},
	{"parse_dirstate", parse_dirstate, METH_VARARGS, "parse a dirstate\n"},
	{"parse_index2", parse_index2, METH_VARARGS, "parse a revlog index\n"},
	{"encodedir", encodedir, METH_VARARGS, "encodedir a path\n"},
	{"pathencode", pathencode, METH_VARARGS, "fncache-encode a path\n"},
	{"lowerencode", lowerencode, METH_VARARGS, "lower-encode a path\n"},
	{NULL, NULL}
};

void dirs_module_init(PyObject *mod);

static void module_init(PyObject *mod)
{
	/* This module constant has two purposes.  First, it lets us unit test
	 * the ImportError raised without hard-coding any error text.  This
	 * means we can change the text in the future without breaking tests,
	 * even across changesets without a recompile.  Second, its presence
	 * can be used to determine whether the version-checking logic is
	 * present, which also helps in testing across changesets without a
	 * recompile.  Note that this means the pure-Python version of parsers
	 * should not have this module constant. */
	PyModule_AddStringConstant(mod, "versionerrortext", versionerrortext);

	dirs_module_init(mod);

	indexType.tp_new = PyType_GenericNew;
	if (PyType_Ready(&indexType) < 0)
		return;
	Py_INCREF(&indexType);

	PyModule_AddObject(mod, "index", (PyObject *)&indexType);

	nullentry = Py_BuildValue("iiiiiiis#", 0, 0, 0,
				  -1, -1, -1, -1, nullid, 20);
	if (nullentry)
		PyObject_GC_UnTrack(nullentry);

	dirstate_unset = Py_BuildValue("ciii", 'n', 0, -1, -1);
}

static int check_python_version(void)
{
	PyObject *sys = PyImport_ImportModule("sys");
	long hexversion = PyInt_AsLong(PyObject_GetAttrString(sys, "hexversion"));
	/* sys.hexversion is a 32-bit number by default, so the -1 case
	 * should only occur in unusual circumstances (e.g. if sys.hexversion
	 * is manually set to an invalid value). */
	if ((hexversion == -1) || (hexversion >> 16 != PY_VERSION_HEX >> 16)) {
		PyErr_Format(PyExc_ImportError, "%s: The Mercurial extension "
			"modules were compiled with Python " PY_VERSION ", but "
			"Mercurial is currently using Python with sys.hexversion=%ld: "
			"Python %s\n at: %s", versionerrortext, hexversion,
			Py_GetVersion(), Py_GetProgramFullPath());
		return -1;
	}
	return 0;
}

#ifdef IS_PY3K
static struct PyModuleDef parsers_module = {
	PyModuleDef_HEAD_INIT,
	"parsers",
	parsers_doc,
	-1,
	methods
};

PyMODINIT_FUNC PyInit_parsers(void)
{
	PyObject *mod;

	if (check_python_version() == -1)
		return;
	mod = PyModule_Create(&parsers_module);
	module_init(mod);
	return mod;
}
#else
PyMODINIT_FUNC initparsers(void)
{
	PyObject *mod;

	if (check_python_version() == -1)
		return;
	mod = Py_InitModule3("parsers", methods, parsers_doc);
	module_init(mod);
}
#endif