Add bufgetpwuid. (Repeated calls to getpwuid() are really expensive.)

3 files changed, 30 insertions, 1 deletions

diff --git a/lib/lib.c b/lib/lib.c
index 0df45bf9..98597b24 100644
--- a/lib/lib.c
+++ b/lib/lib.c
@@ -1074,3 +1074,31 @@ int dev_makedev(int major, int minor)
 {
   return (minor&0xff)|((major&0xfff)<<8)|((minor&0xfff00)<<12);
 }
+
+// Return cached passwd entries.
+struct passwd *bufgetpwuid(uid_t uid)
+{
+  struct pwuidbuf_list {
+    struct pwuidbuf_list *next;
+    struct passwd pw;
+  } *list;
+  struct passwd *temp;
+  static struct pwuidbuf_list *pwuidbuf;
+
+  for (list = pwuidbuf; list; list = list->next)
+    if (list->pw.pw_uid == uid) return &(list->pw);
+
+  list = xmalloc(512);
+  list->next = pwuidbuf;
+
+  errno = getpwuid_r(uid, &list->pw, sizeof(*list)+(char *)list,
+    512-sizeof(*list), &temp);
+  if (!temp) {
+    free(list);
+
+    return 0;
+  }
+  pwuidbuf = list;
+
+  return &list->pw;
+}
diff --git a/lib/lib.h b/lib/lib.h
index aafa9693..b1f4ca11 100644
--- a/lib/lib.h
+++ b/lib/lib.h
@@ -205,6 +205,7 @@ char *strnstr(char *line, char *str);
 int dev_minor(int dev);
 int dev_major(int dev);
 int dev_makedev(int major, int minor);
+struct passwd *bufgetpwuid(uid_t uid);
 
 #define HR_SPACE 1 // Space between number and units
 #define HR_B     2 // Use "B" for single byte units
diff --git a/toys/posix/ps.c b/toys/posix/ps.c
index 9557b64d..445228fd 100644
--- a/toys/posix/ps.c
+++ b/toys/posix/ps.c
@@ -453,7 +453,7 @@ static char *string_field(struct carveup *tb, struct strawberry *field)
 
         if (gr) out = gr->gr_name;
       } else {
-        struct passwd *pw = getpwuid(ll);
+        struct passwd *pw = bufgetpwuid(ll);
 
         if (pw) out = pw->pw_name;
       }