static int
getlock(char *lock)
{
char buf[ERRMAX];
int i, fd;
enum { SECS = 200 };
for(i=0; i<SECS*10; i++){
fd = wcreate(lock, ORDWR, DMEXCL|0666);
if(fd >= 0)
return fd;
buf[0] = '\0';
rerrstr(buf, sizeof buf);
if(strstr(buf, "locked") == nil)
break;
sleep(1000/10);
}
werrstr("couldn't acquire lock %s: %r", lock);
return -1;
}
/* insert word into a redblack tree */
int insert(char *word)
{
TREEREC *curr = ans->root, *par, *gpar, *prev = NULL, *wcreate();
int val;
if( ans->root == NULL )
{
ans->ans = ans->root = wcreate(word, NULL);
return 1;
}
while( curr != NULL && (val = scmp(word, curr->word)) != 0 )
{
prev = curr;
if( val > 0 )
curr = curr->right;
else
curr = curr->left;
}
ans->ans = curr;
if( curr == NULL ) /* insert a new node, rotate up if necessary */
{
if( val > 0 )
curr = prev->right = wcreate(word, prev);
else
curr = prev->left = wcreate(word, prev);
curr->colour = RED;
while( (par = curr->par) != NULL
&& ( gpar = par->par ) != NULL
&& curr->par->colour == RED )
{
if( par == gpar->left )
{
if( gpar->right!=NULL && gpar->right->colour == RED )
{
par->colour = BLACK;
gpar->right->colour = BLACK;
gpar->colour = RED;
curr = gpar;
}
else
{
if( curr == par->right )
{
curr = par;
leftrotate(ans, curr);
par = curr->par;
}
par->colour = BLACK;
if( ( gpar=par->par ) != NULL )
{
gpar->colour = RED;
rightrotate(ans, gpar);
}
}
}
else
{
if( gpar->left!=NULL && gpar->left->colour == RED )
{
par->colour = BLACK;
gpar->left->colour = BLACK;
gpar->colour = RED;
curr = gpar;
}
else
{
if( curr == par->left )
{
curr = par;
rightrotate(ans, curr);
par = curr->par;
}
par->colour = BLACK;
if( ( gpar=par->par ) != NULL )
{
gpar->colour = RED;
leftrotate(ans, gpar);
}
}
}
}
if( curr->par == NULL )
ans->root = curr;
ans->root->colour = BLACK;
return 1;
}
return 0;
}
/*
* Attempt to install a new page. If t==0 we are creating.
* Otherwise, we are editing and t must be set to the current
* version (t is the version we started with) to avoid conflicting
* writes.
*
* If there is a conflicting write, we still write the page to
* the history file, but mark it as a failed write.
*/
int
writepage(int num, uint32_t t, String *s, char *title)
{
char tmp[40], tmplock[40], err[ERRMAX], hist[40], *p;
int conflict, lfd, fd;
Biobuf *b;
String *os;
sprint(tmp, "d/%d", num);
sprint(tmplock, "d/L.%d", num);
sprint(hist, "d/%d.hist", num);
if((lfd = getlock(tmplock)) < 0)
return -1;
conflict = 0;
if(b = wBopen(tmp, OREAD)){
Brdline(b, '\n'); /* title */
if(p = Brdline(b, '\n')) /* version */
p[Blinelen(b)-1] = '\0';
if(p==nil || p[0] != 'D'){
snprint(err, sizeof err, "bad format in extant file");
conflict = 1;
}else if(strtoul(p+1, 0, 0) != t){
os = Brdstring(b); /* why read the whole file? */
p = strchr(s_to_c(s), '\n');
if(p!=nil && strcmp(p+1, s_to_c(os))==0){ /* ignore dup write */
close(lfd);
s_free(os);
Bterm(b);
return 0;
}
s_free(os);
snprint(err, sizeof err, "update conflict %lud != %s", t, p+1);
conflict = 1;
}
Bterm(b);
}else{
if(t != 0){
close(lfd);
werrstr("did not expect to create");
return -1;
}
}
if((fd = wopen(hist, OWRITE)) < 0){
if((fd = wcreate(hist, OWRITE, 0666)) < 0){
close(lfd);
return -1;
}else
fprint(fd, "%s\n", title);
}
if(seek(fd, 0, 2) < 0
|| (conflict && write(fd, "X\n", 2) != 2)
|| write(fd, s_to_c(s), s_len(s)) != s_len(s)){
close(fd);
close(lfd);
return -1;
}
close(fd);
if(conflict){
close(lfd);
voidcache(num);
werrstr(err);
return -1;
}
if((fd = wcreate(tmp, OWRITE, 0666)) < 0){
close(lfd);
voidcache(num);
return -1;
}
if(write(fd, title, strlen(title)) != strlen(title)
|| write(fd, "\n", 1) != 1
|| write(fd, s_to_c(s), s_len(s)) != s_len(s)){
close(fd);
close(lfd);
voidcache(num);
return -1;
}
close(fd);
close(lfd);
voidcache(num);
return 0;
}
