1 files changed, 72 insertions, 0 deletions
diff --git a/indra/newview/scripts/lua/util.lua b/indra/newview/scripts/lua/util.lua
new file mode 100644
index 0000000000..bb8d492d12
--- /dev/null
+++ b/indra/newview/scripts/lua/util.lua
@@ -0,0 +1,72 @@
+-- utility functions, in alpha order
+
+local util = {}
+
+-- cheap test whether table t is empty
+function util.empty(t)
+    for _ in pairs(t) do
+        return false
+    end
+    return true
+end
+
+-- reliable count of the number of entries in table t
+-- (since #t is unreliable)
+function util.count(t)
+    local count = 0
+    for _ in pairs(t) do
+        count += 1
+    end
+    return count
+end
+
+-- recursive table equality
+function util.equal(t1, t2)
+    if not (type(t1) == 'table' and type(t2) == 'table') then
+        return t1 == t2
+    end
+    -- both t1 and t2 are tables: get modifiable copy of t2
+    local temp = table.clone(t2)
+    for k, v in pairs(t1) do
+        -- if any key in t1 doesn't have same value in t2, not equal
+        if not util.equal(v, temp[k]) then
+            return false
+        end
+        -- temp[k] == t1[k], delete temp[k]
+        temp[k] = nil
+    end
+    -- All keys in t1 have equal values in t2; t2 == t1 if there are no extra keys in t2
+    return util.empty(temp)
+end
+
+-- Concatentate the strings in the passed list, return the composite string.
+-- For iterative string building, the theory is that building a list with
+-- table.insert() and then using join() to allocate the full-size result
+-- string once should be more efficient than reallocating an intermediate
+-- string for every partial concatenation.
+function util.join(list, sep)
+    -- This succinct implementation assumes that string.format() precomputes
+    -- the required size of its output buffer before populating it. We don't
+    -- know that. Moreover, this implementation predates our sep argument.
+--  return string.format(string.rep('%s', #list), table.unpack(list))
+
+    -- this implementation makes it explicit
+    local sep = sep or ''
+    local size = if util.empty(list) then 0 else -#sep
+    for _, s in pairs(list) do
+        size += #sep + #s
+    end
+    local result = buffer.create(size)
+    size = 0
+    for i, s in pairs(list) do
+        if i > 1 then
+            buffer.writestring(result, size, sep)
+            size += #sep
+        end
+        buffer.writestring(result, size, s)
+        size += #s
+    end
+    return buffer.tostring(result)
+end
+
+return util