From 97d9c3cdeafb9f48075987c76373a71e6874c6eb Mon Sep 17 00:00:00 2001
From: Linus Torvalds <torvalds@ppc970.osdl.org>
Date: Mon, 11 Apr 2005 16:42:13 -0700
Subject: [PATCH] Make "rev-tree" more efficient and more useful.

Slight change of output format: it now lists all parents on the same line.

This allows it to work on initial commits too (which have no parents), and
also makes the output format a lot more intuitive.
---
 rev-tree.c | 112 +++++++++++++++++++++++++++++++++++++------------------------
 1 file changed, 68 insertions(+), 44 deletions(-)

diff --git a/rev-tree.c b/rev-tree.c
index bbf6281f..73c9d1f5 100644
--- a/rev-tree.c
+++ b/rev-tree.c
@@ -1,28 +1,33 @@
 #include "cache.h"
 
-struct relationship {
+#define SEEN 1
+
+struct parent {
+	struct revision *parent;
+	struct parent *next;
+};
+
+struct revision {
+	unsigned int flags;
 	unsigned char sha1[20];
-	unsigned char parent[20];
+	struct parent *parent;
 };
 
-static struct relationship **rels;
-static int nr_rels, rel_allocs;
+static struct revision **revs;
+static int nr_revs, rev_allocs;
 
-static int find_relationship(unsigned char *sha1, unsigned char *parent)
+static int find_rev(unsigned char *sha1)
 {
-	int first = 0, last = nr_rels;
+	int first = 0, last = nr_revs;
 
 	while (first < last) {
 		int next = (first + last) / 2;
-		struct relationship *rel = rels[next];
+		struct revision *rev = revs[next];
 		int cmp;
 
-		cmp = memcmp(sha1, rel->sha1, 20);
-		if (!cmp) {
-			cmp = memcmp(parent, rel->parent, 20);
-			if (!cmp)
-				return next;
-		}
+		cmp = memcmp(sha1, rev->sha1, 20);
+		if (!cmp)
+			return next;
 		if (cmp < 0) {
 			last = next;
 			continue;
@@ -32,56 +37,69 @@ static int find_relationship(unsigned char *sha1, unsigned char *parent)
 	return -first-1;
 }
 
-static int add_relationship(unsigned char *sha1, unsigned char *parent)
+static struct revision *lookup_rev(unsigned char *sha1)
 {
-	struct relationship *n;
-	int pos;
+	int pos = find_rev(sha1);
+	struct revision *n;
 
-	pos = find_relationship(sha1, parent);
 	if (pos >= 0)
-		return 0;
+		return revs[pos];
+	
 	pos = -pos-1;
 
-	if (rel_allocs == nr_rels) {
-		rel_allocs = alloc_nr(rel_allocs);
-		rels = realloc(rels, rel_allocs * sizeof(struct relationship *));
+	if (rev_allocs == nr_revs) {
+		rev_allocs = alloc_nr(rev_allocs);
+		revs = realloc(revs, rev_allocs * sizeof(struct revision *));
 	}
-	n = malloc(sizeof(struct relationship));
-	
-	memmove(rels + pos + 1, rels + pos, (nr_rels - pos) * sizeof(struct relationship *));
-	rels[pos] = n;
-	nr_rels++;
+	n = malloc(sizeof(struct revision));
+
+	n->flags = 0;
 	memcpy(n->sha1, sha1, 20);
-	memcpy(n->parent, parent, 20);
-	return 1;
+	n->parent = NULL;
+
+	/* Insert it into the right place */
+	memmove(revs + pos + 1, revs + pos, (nr_revs - pos) * sizeof(struct revision *));
+	revs[pos] = n;
+	nr_revs++;
+
+	return n;
 }
 
-static int already_seen(unsigned char *sha1)
+static int add_relationship(struct revision *rev, unsigned char *parent_sha)
 {
-	static char null_sha[20];
-	int pos = find_relationship(sha1, null_sha);
+	struct revision *parent_rev = lookup_rev(parent_sha);
+	struct parent **pp = &rev->parent, *p;
 
-	if (pos < 0) 
-		pos = -pos-1;
-	if (pos < nr_rels && !memcmp(sha1, rels[pos]->sha1, 20))
-		return 1;
-	return 0;
+	while ((p = *pp) != NULL) {
+		if (p->parent == parent_rev)
+			return 0;
+		pp = &p->next;
+	}
+
+	p = malloc(sizeof(*p));
+	p->parent = parent_rev;
+	p->next = NULL;
+	*pp = p;
+	return 1;
 }
 
 static int parse_commit(unsigned char *sha1)
 {
-	if (!already_seen(sha1)) {
+	struct revision *rev = lookup_rev(sha1);
+
+	if (!(rev->flags & SEEN)) {
 		void *buffer;
 		unsigned long size;
 		char type[20];
 		unsigned char parent[20];
 
+		rev->flags |= SEEN;
 		buffer = read_sha1_file(sha1, type, &size);
 		if (!buffer || strcmp(type, "commit"))
 			return -1;
 		buffer += 46; /* "tree " + "hex sha1" + "\n" */
 		while (!memcmp(buffer, "parent ", 7) && !get_sha1_hex(buffer+7, parent)) {
-			add_relationship(sha1, parent);
+			add_relationship(rev, parent);
 			parse_commit(parent);
 			buffer += 48;	/* "parent " + "hex sha1" + "\n" */
 		}
@@ -98,7 +116,7 @@ static void read_cache_file(const char *path)
 		unsigned char sha1[20], parent[20];
 		if (get_sha1_hex(line, sha1) || get_sha1_hex(line + 41, parent))
 			usage("bad rev-tree cache file %s", path);
-		add_relationship(sha1, parent);
+		add_relationship(lookup_rev(sha1), parent);
 	}
 	fclose(file);
 }
@@ -128,11 +146,17 @@ int main(int argc, char **argv)
 	if (argc != 2 || get_sha1_hex(argv[1], sha1))
 		usage("rev-tree [--cache <cache-file>] <commit-id>");
 	parse_commit(sha1);
-	for (i = 0; i < nr_rels; i++) {
-		char parent[60];
-		struct relationship *rel = rels[i];
-		strcpy(parent, sha1_to_hex(rel->parent));
-		printf("%s %s\n", sha1_to_hex(rel->sha1), parent);
+	for (i = 0; i < nr_revs; i++) {
+		struct revision *rev = revs[i];
+		struct parent *p;
+
+		printf("%s", sha1_to_hex(rev->sha1));
+		p = rev->parent;
+		while (p) {
+			printf(" %s", sha1_to_hex(p->parent->sha1));
+			p = p->next;
+		}
+		printf("\n");
 	}
 	return 0;
 }
-- 
2.11.0