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authorMatthew Wild <mwild1@gmail.com>2020-10-28 14:21:09 +0000
committerMatthew Wild <mwild1@gmail.com>2020-10-28 14:21:09 +0000
commit0b9a8e9ac32b5b34ffaa826d2d4d9c271f0449ec (patch)
tree75beeff8eed91adb1fdf3bd572cf240191381fd1
parent667b367b5f254920466b95bcb70cfe03560664a3 (diff)
downloadprosody-0b9a8e9ac32b5b34ffaa826d2d4d9c271f0449ec.tar.gz
prosody-0b9a8e9ac32b5b34ffaa826d2d4d9c271f0449ec.zip
util.dbuffer: Optimize :sub() and :byte()
-rw-r--r--util/dbuffer.lua30
1 files changed, 26 insertions, 4 deletions
diff --git a/util/dbuffer.lua b/util/dbuffer.lua
index 9d58b306..640c1449 100644
--- a/util/dbuffer.lua
+++ b/util/dbuffer.lua
@@ -1,5 +1,6 @@
local queue = require "util.queue";
+local s_byte, s_sub = string.byte, string.sub;
local dbuffer_methods = {};
local dynamic_buffer_mt = { __index = dbuffer_methods };
@@ -101,7 +102,11 @@ function dbuffer_methods:discard(requested_bytes)
return true;
end
-function dbuffer_methods:sub(i, j)
+-- Normalize i, j into absolute offsets within the
+-- front chunk (accounting for front_consumed), and
+-- ensure there is enough data in the first chunk
+-- to cover any subsequent :sub() or :byte() operation
+function dbuffer_methods:_prep_sub(i, j)
if j == nil then
j = -1;
end
@@ -118,18 +123,35 @@ function dbuffer_methods:sub(i, j)
j = self._length;
end
if i > j then
- return "";
+ return nil;
end
self:collapse(j);
- return self.items:peek():sub(self.front_consumed+1):sub(i, j);
+ if self.front_consumed > 0 then
+ i = i + self.front_consumed;
+ j = j + self.front_consumed;
+ end
+
+ return i, j;
+end
+
+function dbuffer_methods:sub(i, j)
+ i, j = self:_prep_sub(i, j);
+ if not i then
+ return "";
+ end
+ return s_sub(self.items:peek(), i, j);
end
function dbuffer_methods:byte(i, j)
i = i or 1;
j = j or i;
- return string.byte(self:sub(i, j), 1, -1);
+ i, j = self:_prep_sub(i, j);
+ if not i then
+ return;
+ end
+ return s_byte(self.items:peek(), i, j);
end
function dbuffer_methods:length()