@ -8,9 +8,10 @@
@@ -8,9 +8,10 @@
*
*/
#include <stdlib.h>
#include <openssl/bn.h> // provides arbitrary precision integers
// required to accurately represent fractional
//mass
/* Provides arbitrary precision integers required to accurately represent
* fractional mass: */
#include <openssl/bn.h>
#include "cache.h"
#include "commit.h"
@ -125,7 +126,6 @@ static struct fraction *add(struct fraction *result, struct fraction *left, stru
@@ -125,7 +126,6 @@ static struct fraction *add(struct fraction *result, struct fraction *left, stru
static int compare(struct fraction *left, struct fraction *right)
{
BIGNUM a, b;
int result;
BN_init(&a);
@ -159,7 +159,8 @@ static struct mass_counter *new_mass_counter(struct commit *commit, struct fract
@@ -159,7 +159,8 @@ static struct mass_counter *new_mass_counter(struct commit *commit, struct fract
copy(&mass_counter->seen, get_zero());
if (commit->object.util) {
die("multiple attempts to initialize mass counter for %s\n", sha1_to_hex(commit->object.sha1));
die("multiple attempts to initialize mass counter for %s",
sha1_to_hex(commit->object.sha1));
}
commit->object.util = mass_counter;
@ -174,64 +175,59 @@ static void free_mass_counter(struct mass_counter *counter)
@@ -174,64 +175,59 @@ static void free_mass_counter(struct mass_counter *counter)
free(counter);
}
//
// Finds the base commit of a list of commits.
//
// One property of the commit being searched for is that every commit reachable
// from the base commit is reachable from the commits in the starting list only
// via paths that include the base commit.
//
// This algorithm uses a conservation of mass approach to find the base commit.
//
// We start by injecting one unit of mass into the graph at each
// of the commits in the starting list. Injecting mass into a commit
// is achieved by adding to its pending mass counter and, if it is not already
// enqueued, enqueuing the commit in a list of pending commits, in latest
// commit date first order.
//
// The algorithm then preceeds to visit each commit in the pending queue.
// Upon each visit, the pending mass is added to the mass already seen for that
// commit and then divided into N equal portions, where N is the number of
// parents of the commit being visited. The divided portions are then injected
// into each of the parents.
//
// The algorithm continues until we discover a commit which has seen all the
// mass originally injected or until we run out of things to do.
//
// If we find a commit that has seen all the original mass, we have found
// the common base of all the commits in the starting list.
//
// The algorithm does _not_ depend on accurate timestamps for correct operation.
// However, reasonably sane (e.g. non-random) timestamps are required in order
// to prevent an exponential performance characteristic. The occasional
// timestamp inaccuracy will not dramatically affect performance but may
// result in more nodes being processed than strictly necessary.
//
// This procedure sets *boundary to the address of the base commit. It returns
// non-zero if, and only if, there was a problem parsing one of the
// commits discovered during the traversal.
//
/*
* Finds the base commit of a list of commits.
*
* One property of the commit being searched for is that every commit reachable
* from the base commit is reachable from the commits in the starting list only
* via paths that include the base commit.
*
* This algorithm uses a conservation of mass approach to find the base commit.
*
* We start by injecting one unit of mass into the graph at each
* of the commits in the starting list. Injecting mass into a commit
* is achieved by adding to its pending mass counter and, if it is not already
* enqueued, enqueuing the commit in a list of pending commits, in latest
* commit date first order.
*
* The algorithm then preceeds to visit each commit in the pending queue.
* Upon each visit, the pending mass is added to the mass already seen for that
* commit and then divided into N equal portions, where N is the number of
* parents of the commit being visited. The divided portions are then injected
* into each of the parents.
*
* The algorithm continues until we discover a commit which has seen all the
* mass originally injected or until we run out of things to do.
*
* If we find a commit that has seen all the original mass, we have found
* the common base of all the commits in the starting list.
*
* The algorithm does _not_ depend on accurate timestamps for correct operation.
* However, reasonably sane (e.g. non-random) timestamps are required in order
* to prevent an exponential performance characteristic. The occasional
* timestamp inaccuracy will not dramatically affect performance but may
* result in more nodes being processed than strictly necessary.
*
* This procedure sets *boundary to the address of the base commit. It returns
* non-zero if, and only if, there was a problem parsing one of the
* commits discovered during the traversal.
*/
static int find_base_for_list(struct commit_list *list, struct commit **boundary)
{
int ret = 0;
struct commit_list *cleaner = NULL;
struct commit_list *pending = NULL;
*boundary = NULL;
struct fraction injected;
init_fraction(&injected);
*boundary = NULL;
for (; list; list = list->next) {
struct commit *item = list->item;
if (item->object.util) {
die("%s:%d:%s: logic error: this should not have happened - commit %s\n",
__FILE__, __LINE__, __FUNCTION__, sha1_to_hex(item->object.sha1));
die("%s:%d:%s: logic error: this should not have happened - commit %s",
__FILE__, __LINE__, __FUNCTION__,
sha1_to_hex(item->object.sha1));
}
new_mass_counter(list->item, get_one());
@ -242,81 +238,62 @@ static int find_base_for_list(struct commit_list *list, struct commit **boundary
@@ -242,81 +238,62 @@ static int find_base_for_list(struct commit_list *list, struct commit **boundary
}
while (!*boundary && pending && !ret) {
struct commit *latest = pop_commit(&pending);
struct mass_counter *latest_node = (struct mass_counter *) latest->object.util;
int num_parents;
if ((ret = parse_commit(latest)))
continue;
add(&latest_node->seen, &latest_node->seen, &latest_node->pending);
int num_parents = count_parents(latest);
num_parents = count_parents(latest);
if (num_parents) {
struct fraction distribution;
struct commit_list *parents;
divide(init_fraction(&distribution), &latest_node->pending, num_parents);
for (parents = latest->parents; parents; parents = parents->next) {
struct commit *parent = parents->item;
struct mass_counter *parent_node = (struct mass_counter *) parent->object.util;
if (!parent_node) {
parent_node = new_mass_counter(parent, &distribution);
insert_by_date(&pending, parent);
commit_list_insert(parent, &cleaner);
} else {
if (!compare(&parent_node->pending, get_zero())) {
if (!compare(&parent_node->pending, get_zero()))
insert_by_date(&pending, parent);
}
add(&parent_node->pending, &parent_node->pending, &distribution);
}
}
clear_fraction(&distribution);
}
if (!compare(&latest_node->seen, &injected)) {
if (!compare(&latest_node->seen, &injected))
*boundary = latest;
}
copy(&latest_node->pending, get_zero());
}
while (cleaner) {
struct commit *next = pop_commit(&cleaner);
free_mass_counter((struct mass_counter *) next->object.util);
next->object.util = NULL;
}
if (pending)
free_commit_list(pending);
clear_fraction(&injected);
return ret;
}
//
// Finds the base of an minimal, non-linear epoch, headed at head, by
// applying the find_base_for_list to a list consisting of the parents
//
/*
* Finds the base of an minimal, non-linear epoch, headed at head, by
* applying the find_base_for_list to a list consisting of the parents
*/
static int find_base(struct commit *head, struct commit **boundary)
{
int ret = 0;
@ -332,14 +309,14 @@ static int find_base(struct commit *head, struct commit **boundary)
@@ -332,14 +309,14 @@ static int find_base(struct commit *head, struct commit **boundary)
return ret;
}
//
// This procedure traverses to the boundary of the first epoch in the epoch
// sequence of the epoch headed at head_of_epoch. This is either the end of
// the maximal linear epoch or the base of a minimal non-linear epoch.
//
// The queue of pending nodes is sorted in reverse date order and each node
// is currently in the queue at most once.
//
/*
* This procedure traverses to the boundary of the first epoch in the epoch
* sequence of the epoch headed at head_of_epoch. This is either the end of
* the maximal linear epoch or the base of a minimal non-linear epoch.
*
* The queue of pending nodes is sorted in reverse date order and each node
* is currently in the queue at most once.
*/
static int find_next_epoch_boundary(struct commit *head_of_epoch, struct commit **boundary)
{
int ret;
@ -350,10 +327,10 @@ static int find_next_epoch_boundary(struct commit *head_of_epoch, struct commit
@@ -350,10 +327,10 @@ static int find_next_epoch_boundary(struct commit *head_of_epoch, struct commit
return ret;
if (HAS_EXACTLY_ONE_PARENT(item)) {
// we are at the start of a maximimal linear epoch .. traverse to the end
// traverse to the end of a maximal linear epoch
/*
* We are at the start of a maximimal linear epoch.
* Traverse to the end.
*/
while (HAS_EXACTLY_ONE_PARENT(item) && !ret) {
item = item->parents->item;
ret = parse_commit(item);
@ -361,35 +338,35 @@ static int find_next_epoch_boundary(struct commit *head_of_epoch, struct commit
@@ -361,35 +338,35 @@ static int find_next_epoch_boundary(struct commit *head_of_epoch, struct commit
*boundary = item;
} else {
// otherwise, we are at the start of a minimal, non-linear
// epoch - find the common base of all parents.
/*
* Otherwise, we are at the start of a minimal, non-linear
* epoch - find the common base of all parents.
*/
ret = find_base(item, boundary);
}
return ret;
}
//
// Returns non-zero if parent is known to be a parent of child.
//
/*
* Returns non-zero if parent is known to be a parent of child.
*/
static int is_parent_of(struct commit *parent, struct commit *child)
{
struct commit_list *parents;
for (parents = child->parents; parents; parents = parents->next) {
if (!memcmp(parent->object.sha1, parents->item->object.sha1, sizeof(parents->item->object.sha1)))
if (!memcmp(parent->object.sha1, parents->item->object.sha1,
sizeof(parents->item->object.sha1)))
return 1;
}
return 0;
}
//
// Pushes an item onto the merge order stack. If the top of the stack is
// marked as being a possible "break", we check to see whether it actually
// is a break.
//
/*
* Pushes an item onto the merge order stack. If the top of the stack is
* marked as being a possible "break", we check to see whether it actually
* is a break.
*/
static void push_onto_merge_order_stack(struct commit_list **stack, struct commit *item)
{
struct commit_list *top = *stack;
@ -401,54 +378,53 @@ static void push_onto_merge_order_stack(struct commit_list **stack, struct commi
@@ -401,54 +378,53 @@ static void push_onto_merge_order_stack(struct commit_list **stack, struct commi
commit_list_insert(item, stack);
}
//
// Marks all interesting, visited commits reachable from this commit
// as uninteresting. We stop recursing when we reach the epoch boundary,
// an unvisited node or a node that has already been marking uninteresting.
// This doesn't actually mark all ancestors between the start node and the
// epoch boundary uninteresting, but does ensure that they will
// eventually be marked uninteresting when the main sort_first_epoch
// traversal eventually reaches them.
//
/*
* Marks all interesting, visited commits reachable from this commit
* as uninteresting. We stop recursing when we reach the epoch boundary,
* an unvisited node or a node that has already been marking uninteresting.
*
* This doesn't actually mark all ancestors between the start node and the
* epoch boundary uninteresting, but does ensure that they will eventually
* be marked uninteresting when the main sort_first_epoch() traversal
* eventually reaches them.
*/
static void mark_ancestors_uninteresting(struct commit *commit)
{
unsigned int flags = commit->object.flags;
int visited = flags & VISITED;
int boundary = flags & BOUNDARY;
int uninteresting = flags & UNINTERESTING;
struct commit_list *next;
commit->object.flags |= UNINTERESTING;
if (uninteresting || boundary || !visited) {
return;
// we only need to recurse if
// we are not on the boundary, and,
// we have not already been marked uninteresting, and,
// we have already been visited.
//
// the main sort_first_epoch traverse will
// mark unreachable all uninteresting, unvisited parents
// as they are visited so there is no need to duplicate
// that traversal here.
//
// similarly, if we are already marked uninteresting
// then either all ancestors have already been marked
// uninteresting or will be once the sort_first_epoch
// traverse reaches them.
//
}
struct commit_list *next;
/*
* We only need to recurse if
* we are not on the boundary and
* we have not already been marked uninteresting and
* we have already been visited.
*
* The main sort_first_epoch traverse will mark unreachable
* all uninteresting, unvisited parents as they are visited
* so there is no need to duplicate that traversal here.
*
* Similarly, if we are already marked uninteresting
* then either all ancestors have already been marked
* uninteresting or will be once the sort_first_epoch
* traverse reaches them.
*/
if (uninteresting || boundary || !visited)
return;
for (next = commit->parents; next; next = next->next)
mark_ancestors_uninteresting(next->item);
}
//
// Sorts the nodes of the first epoch of the epoch sequence of the epoch headed at head
// into merge order.
//
/*
* Sorts the nodes of the first epoch of the epoch sequence of the epoch headed at head
* into merge order.
*/
static void sort_first_epoch(struct commit *head, struct commit_list **stack)
{
struct commit_list *parents;
@ -456,63 +432,59 @@ static void sort_first_epoch(struct commit *head, struct commit_list **stack)
@@ -456,63 +432,59 @@ static void sort_first_epoch(struct commit *head, struct commit_list **stack)
head->object.flags |= VISITED;
//
// parse_commit builds the parent list in reverse order with respect to the order of
// the git-commit-tree arguments.
//
// so we need to reverse this list to output the oldest (or most "local") commits last.
//
/*
* parse_commit() builds the parent list in reverse order with respect
* to the order of the git-commit-tree arguments. So we need to reverse
* this list to output the oldest (or most "local") commits last.
*/
for (parents = head->parents; parents; parents = parents->next)
commit_list_insert(parents->item, &reversed_parents);
//
// todo: by sorting the parents in a different order, we can alter the
// merge order to show contemporaneous changes in parallel branches
// occurring after "local" changes. This is useful for a developer
// when a developer wants to see all changes that were incorporated
// into the same merge as her own changes occur after her own
// changes.
//
/*
* TODO: By sorting the parents in a different order, we can alter the
* merge order to show contemporaneous changes in parallel branches
* occurring after "local" changes. This is useful for a developer
* when a developer wants to see all changes that were incorporated
* into the same merge as her own changes occur after her own
* changes.
*/
while (reversed_parents) {
struct commit *parent = pop_commit(&reversed_parents);
if (head->object.flags & UNINTERESTING) {
// propagates the uninteresting bit to
// all parents. if we have already visited
// this parent, then the uninteresting bit
// will be propagated to each reachable
// commit that is still not marked uninteresting
// and won't otherwise be reached.
/*
* Propagates the uninteresting bit to all parents.
* if we have already visited this parent, then
* the uninteresting bit will be propagated to each
* reachable commit that is still not marked
* uninteresting and won't otherwise be reached.
*/
mark_ancestors_uninteresting(parent);
}
if (!(parent->object.flags & VISITED)) {
if (parent->object.flags & BOUNDARY) {
if (*stack) {
die("something else is on the stack - %s\n", sha1_to_hex((*stack)->item->object.sha1));
die("something else is on the stack - %s",
sha1_to_hex((*stack)->item->object.sha1));
}
push_onto_merge_order_stack(stack, parent);
parent->object.flags |= VISITED;
} else {
sort_first_epoch(parent, stack);
if (reversed_parents) {
//
// this indicates a possible discontinuity
// it may not be be actual discontinuity if
// the head of parent N happens to be the tail
// of parent N+1
//
// the next push onto the stack will resolve the
// question
//
/*
* This indicates a possible
* discontinuity it may not be be
* actual discontinuity if the head
* of parent N happens to be the tail
* of parent N+1.
*
* The next push onto the stack will
* resolve the question.
*/
(*stack)->item->object.flags |= DISCONTINUITY;
}
}
@ -522,27 +494,23 @@ static void sort_first_epoch(struct commit *head, struct commit_list **stack)
@@ -522,27 +494,23 @@ static void sort_first_epoch(struct commit *head, struct commit_list **stack)
push_onto_merge_order_stack(stack, head);
}
//
// Emit the contents of the stack.
//
// The stack is freed and replaced by NULL.
//
// Sets the return value to STOP if no further output should be generated.
//
/*
* Emit the contents of the stack.
*
* The stack is freed and replaced by NULL.
*
* Sets the return value to STOP if no further output should be generated.
*/
static int emit_stack(struct commit_list **stack, emitter_func emitter)
{
unsigned int seen = 0;
int action = CONTINUE;
while (*stack && (action != STOP)) {
struct commit *next = pop_commit(stack);
seen |= next->object.flags;
if (*stack) {
if (*stack)
action = (*emitter) (next);
}
}
if (*stack) {
@ -553,13 +521,13 @@ static int emit_stack(struct commit_list **stack, emitter_func emitter)
@@ -553,13 +521,13 @@ static int emit_stack(struct commit_list **stack, emitter_func emitter)
return (action == STOP || (seen & UNINTERESTING)) ? STOP : CONTINUE;
}
//
// Sorts an arbitrary epoch into merge order by sorting each epoch
// of its epoch sequence into order.
//
// Note: this algorithm currently leaves traces of its execution in the
// object flags of nodes it discovers. This should probably be fixed.
//
/*
* Sorts an arbitrary epoch into merge order by sorting each epoch
* of its epoch sequence into order.
*
* Note: this algorithm currently leaves traces of its execution in the
* object flags of nodes it discovers. This should probably be fixed.
*/
static int sort_in_merge_order(struct commit *head_of_epoch, emitter_func emitter)
{
struct commit *next = head_of_epoch;
@ -569,29 +537,24 @@ static int sort_in_merge_order(struct commit *head_of_epoch, emitter_func emitte
@@ -569,29 +537,24 @@ static int sort_in_merge_order(struct commit *head_of_epoch, emitter_func emitte
ret = parse_commit(head_of_epoch);
while (next && next->parents && !ret && (action != STOP)) {
struct commit *base = NULL;
if ((ret = find_next_epoch_boundary(next, &base)))
ret = find_next_epoch_boundary(next, &base);
if (ret)
return ret;
next->object.flags |= BOUNDARY;
if (base) {
if (base)
base->object.flags |= BOUNDARY;
}
if (HAS_EXACTLY_ONE_PARENT(next)) {
while (HAS_EXACTLY_ONE_PARENT(next)
&& (action != STOP)
&& !ret) {
if (next->object.flags & UNINTERESTING) {
action = STOP;
} else {
action = (*emitter) (next);
}
if (action != STOP) {
next = next->parents->item;
ret = parse_commit(next);
@ -599,14 +562,11 @@ static int sort_in_merge_order(struct commit *head_of_epoch, emitter_func emitte
@@ -599,14 +562,11 @@ static int sort_in_merge_order(struct commit *head_of_epoch, emitter_func emitte
}
} else {
struct commit_list *stack = NULL;
sort_first_epoch(next, &stack);
action = emit_stack(&stack, emitter);
next = base;
}
}
if (next && (action != STOP) && !ret) {
@ -616,29 +576,27 @@ static int sort_in_merge_order(struct commit *head_of_epoch, emitter_func emitte
@@ -616,29 +576,27 @@ static int sort_in_merge_order(struct commit *head_of_epoch, emitter_func emitte
return ret;
}
//
// Sorts the nodes reachable from a starting list in merge order, we
// first find the base for the starting list and then sort all nodes in this
// subgraph using the sort_first_epoch algorithm. Once we have reached the base
// we can continue sorting using sort_in_merge_order.
//
/*
* Sorts the nodes reachable from a starting list in merge order, we
* first find the base for the starting list and then sort all nodes
* in this subgraph using the sort_first_epoch algorithm. Once we have
* reached the base we can continue sorting using sort_in_merge_order.
*/
int sort_list_in_merge_order(struct commit_list *list, emitter_func emitter)
{
struct commit_list *stack = NULL;
struct commit *base;
int ret = 0;
int action = CONTINUE;
struct commit_list *reversed = NULL;
for (; list; list = list->next) {
struct commit *next = list->item;
if (!(next->object.flags & UNINTERESTING)) {
if (next->object.flags & DUPCHECK) {
fprintf(stderr, "%s: duplicate commit %s ignored\n", __FUNCTION__, sha1_to_hex(next->object.sha1));
fprintf(stderr, "%s: duplicate commit %s ignored\n",
__FUNCTION__, sha1_to_hex(next->object.sha1));
} else {
next->object.flags |= DUPCHECK;
commit_list_insert(list->item, &reversed);
@ -647,36 +605,35 @@ int sort_list_in_merge_order(struct commit_list *list, emitter_func emitter)
@@ -647,36 +605,35 @@ int sort_list_in_merge_order(struct commit_list *list, emitter_func emitter)
}
if (!reversed->next) {
// if there is only one element in the list, we can sort it using
// sort_in_merge_order.
/*
* If there is only one element in the list, we can sort it
* using sort_in_merge_order.
*/
base = reversed->item;
} else {
// otherwise, we search for the base of the list
if ((ret = find_base_for_list(reversed, &base)))
/*
* Otherwise, we search for the base of the list.
*/
ret = find_base_for_list(reversed, &base);
if (ret)
return ret;
if (base) {
if (base)
base->object.flags |= BOUNDARY;
}
while (reversed) {
sort_first_epoch(pop_commit(&reversed), &stack);
if (reversed) {
//
// if we have more commits to push, then the
// first push for the next parent may (or may not)
// represent a discontinuity with respect to the
// parent currently on the top of the stack.
//
// mark it for checking here, and check it
// with the next push...see sort_first_epoch for
// more details.
//
/*
* If we have more commits to push, then the
* first push for the next parent may (or may
* not) represent a discontinuity with respect
* to the parent currently on the top of
* the stack.
*
* Mark it for checking here, and check it
* with the next push. See sort_first_epoch()
* for more details.
*/
stack->item->object.flags |= DISCONTINUITY;
}
}