hostlist: add hostlist_find_hostname and support

problem: each time we search for a hostname in a hostlist, even with the
allocations avoided and so-forth, we have to find its length, parse the
integer at the end, and validate it.  All of this is quite expensive, to
the tune of as much as 60-70% of the search time.

solution: add an interface to do all the prep work and return an opaque
handle to the hostname object hostlist uses internally so a caller can
re-use a pre-built object with the new hostlist_find_hostname interface.
The result comes out a bit over twice as fast as directly using the
allocation-free interface.

src/common/libhostlist/hostlist.c

@@ -688,16 +688,10 @@ int hostlist_count (struct hostlist *hl)
 }
 
 static int hostlist_find_host (struct hostlist *hl,
-                               const char *hostname,
+                               struct stack_hostname *hn,
                                struct current *cur)
 {
     int i, count, ret = -1;
-    struct stack_hostname hn_storage;
-
-    struct stack_hostname *hn = hostname_stack_create (&hn_storage, hostname);
-    if (!hn)
-        return -1;
-
     for (i = 0, count = 0; i < hl->nranges; i++) {
         int offset = hostrange_hn_within (hl->hr[i], hn);
         if (offset >= 0) {
@@ -721,7 +715,33 @@ int hostlist_find (struct hostlist *hl, const char *hostname)
         errno = EINVAL;
         return -1;
     }
-    return hostlist_find_host (hl, hostname, &hl->current);
+    struct stack_hostname hn_storage;
+
+    struct stack_hostname *hn = hostname_stack_create (&hn_storage, hostname);
+    if (!hn)
+        return -1;
+    return hostlist_find_host (hl, hn, &hl->current);
+}
+
+int hostlist_find_hostname (struct hostlist *hl, struct hostname *hn)
+{
+    if (!hl || !hn) {
+        errno = EINVAL;
+        return -1;
+    }
+    struct stack_hostname hn_storage;
+
+    struct stack_hostname *shn = hostname_stack_create_from_hostname (&hn_storage, hn);
+    if (!hn)
+        return -1;
+    return hostlist_find_host (hl, shn, &hl->current);
+}
+
+struct hostname *hostlist_hostname_create (const char *hn) {
+    return hostname_create (hn);
+}
+void hostlist_hostname_destroy (struct hostname *hn) {
+    hostname_destroy(hn);
 }
 
 /*  Remove host at cursor 'cur'. If the current real cursor hl->current
@@ -786,7 +806,12 @@ static int hostlist_remove_at (struct hostlist *hl, struct current *cur)
 static int hostlist_delete_host (struct hostlist *hl, const char *hostname)
 {
     struct current cur = { 0 };
-    int n = hostlist_find_host (hl, hostname, &cur);
+    struct stack_hostname hn_storage;
+
+    struct stack_hostname *hn = hostname_stack_create (&hn_storage, hostname);
+    if (!hn)
+        return -1;
+    int n = hostlist_find_host (hl, hn, &cur);
     if (n < 0)
         return errno == ENOENT ? 0 : -1;
     return hostlist_remove_at (hl, &cur);

src/common/libhostlist/hostlist.h

@@ -67,6 +67,42 @@ const char * hostlist_nth (struct hostlist * hl, int n);
  */
 int hostlist_find (struct hostlist * hl, const char *hostname);
 
+/*
+ *  Search hostlist hl for the first host matching hostname
+ *   and return position in list if found.
+ *
+ *  Leaves cursor pointing to the matching host.
+ *
+ *  Returns -1 if host is not found.
+ */
+struct hostname *hostlist_hostname_create (const char *);
+
+/*
+ *  Free resources associated with hostname hn.
+ */
+void hostlist_hostname_destroy (struct hostname *hn);
+
+/*
+ *  Search hostlist hl for the first host matching hn
+ *   and return position in list if found.
+ *
+ *  Leaves cursor pointing to the matching host.
+ *
+ *  Returns -1 if host is not found.
+ */
+int hostlist_find_hostname (struct hostlist *hl, struct hostname *hn);
+
+/*
+ *  Search hostlist hl for the first host matching the current hostname in
+ *  hostlist hl_src and return position in list if found.
+ *
+ *  Leaves the cursor of hl pointing to the matching host, and hl_src pointing
+ *  to the same value.
+ *
+ *  Returns -1 if host is not found.
+ */
+int hostlist_find_current (struct hostlist * hl, struct hostlist *hl_src);
+
 /*
  *  Delete all hosts in the list represented by `hosts'
  *

src/common/libhostlist/hostname.c

@@ -52,6 +52,20 @@ static int hostname_len (const char *hostname)
     return len;
 }
 
+struct stack_hostname * hostname_stack_create_from_hostname (struct stack_hostname *hn, struct hostname *src) {
+    if (!hn || !src) {
+        errno = EINVAL;
+        return NULL;
+    }
+    hn->hostname = src->hostname;
+    hn->suffix = src->suffix;
+    hn->len = src->len;
+    hn->len_prefix = src->len_prefix;
+    hn->width = src->width;
+    hn->num = src->num;
+    return hn;
+}
+
 struct stack_hostname * hostname_stack_create_with_suffix (struct stack_hostname *hn,
         const char *hostname, int len,  int idx) {
     if (!hostname || !hn || len < 0) {
@@ -128,6 +142,9 @@ struct hostname * hostname_create_with_suffix (const char *hostname,
     }
 
     hn->num = 0;
+    hn->len = len;
+    hn->len_prefix = idx + 1;
+    hn->width = hn->len - hn->len_prefix;
     hn->prefix = NULL;
     hn->suffix = NULL;
 

src/common/libhostlist/hostname.h

@@ -18,6 +18,9 @@
 struct hostname {
     char *hostname;         /* cache of initialized hostname        */
     char *prefix;           /* hostname prefix                      */
+    int len; /* length minus invalid characters */
+    int len_prefix; /* length of the prefix */
+    int width;   /* length of the suffix */
     unsigned long num;      /* numeric suffix                       */
 
     /* string representation of numeric suffix
@@ -30,7 +33,7 @@ struct stack_hostname {
     int len; /* length minus invalid characters */
     int len_prefix; /* length of the prefix */
     int width;   /* length of the suffix */
-    int num;      /* numeric suffix                       */
+    unsigned long num;      /* numeric suffix                       */
 
     /* string representation of numeric suffix
      * points into `hostname'                                       */
@@ -40,6 +43,7 @@ struct stack_hostname {
 struct hostname * hostname_create (const char *s);
 struct hostname * hostname_create_with_suffix (const char *s, int i);
 struct stack_hostname * hostname_stack_create (struct stack_hostname *hn, const char *hostname);
+struct stack_hostname * hostname_stack_create_from_hostname (struct stack_hostname *hn, struct hostname* hn_src);
 struct stack_hostname * hostname_stack_create_with_suffix (struct stack_hostname *hn,
         const char *hostname, int len, int idx);
 struct stack_hostname * hostname_stack_copy_one_less_digit (struct stack_hostname *dst,

src/common/libhostlist/hostrange.c

@@ -75,7 +75,7 @@ struct hostrange * hostrange_create_single (const char *prefix)
 
 /* Create a hostrange object with a prefix, hi, lo, and format width
  */
-struct hostrange * hostrange_create (char *prefix,
+struct hostrange * hostrange_create (const char *prefix,
                                      unsigned long lo,
                                      unsigned long hi,
                                      int width)

src/common/libhostlist/hostrange.h

@@ -32,7 +32,7 @@ struct hostrange {
 
 struct hostrange * hostrange_create_single (const char *);
 
-struct hostrange * hostrange_create (char *s,
+struct hostrange * hostrange_create (const char *s,
                                      unsigned long lo,
                                      unsigned long hi,
                                      int width);