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util.dbuffer: Optimize :sub() and :byte()

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This commit is contained in:
Matthew Wild 2020-10-28 14:21:09 +00:00
parent a095a0c533
commit 01c5bf5529
1 changed files with 26 additions and 4 deletions
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30
util/dbuffer.lua
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@ -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()