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perf: avoid generating utf8_len_func at runtime #36

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Sep 18, 2020
Merged

perf: avoid generating utf8_len_func at runtime #36

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37 changes: 17 additions & 20 deletions lib/jsonschema.lua
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Original file line number Diff line number Diff line change
Expand Up @@ -10,6 +10,7 @@ local DEBUG = os and os.getenv and os.getenv('DEBUG') == '1'
local tab_concat = table.concat
local tab_insert = table.insert
local string = string
local str_byte = string.byte

-- default null token
local default_null = nil
Expand Down Expand Up @@ -316,6 +317,20 @@ function validatorlib.tablekind(t)
return 0 -- mixed array/object
end

function validatorlib.utf8_len(s)
local c, j=0, 1
while j <= #s do
local cb = str_byte(s, j)
if cb >= 0 and cb <= 127 then j = j + 1
elseif cb >= 192 and cb <= 223 then j = j + 2
elseif cb >= 224 and cb <= 239 then j = j + 3
elseif cb >= 240 and cb <= 247 then j = j + 4
end
c = c + 1
end
return c
end

-- used for unique items in arrays (not fast at all)
-- from: http://stackoverflow.com/questions/25922437
-- If we consider only the JSON case, this function could be simplified:
Expand Down Expand Up @@ -464,22 +479,6 @@ local function to_lua_code(var)
return code .. "}"
end

local function utf8_len_func(ctx)
return sformat([[function(s)
local c, j=0, 1
while j <= #s do
local cb = %s(s, j)
if cb >= 0 and cb <= 127 then j = j + 1
elseif cb >= 192 and cb <= 223 then j = j + 2
elseif cb >= 224 and cb <= 239 then j = j + 3
elseif cb >= 240 and cb <= 247 then j = j + 4
end
c = c + 1
end
return c
end]], ctx:libfunc("string.byte"))
end

generate_validator = function(ctx, schema)
-- get type informations as they will be necessary anyway
local datatype = ctx:localvar(sformat('%s(%s)',
Expand Down Expand Up @@ -827,16 +826,14 @@ generate_validator = function(ctx, schema)
if schema.minLength or schema.maxLength or schema.pattern then
ctx:stmt(sformat('if %s == "string" then', datatype))
if schema.minLength then
ctx:stmt(sformat(' local utf8_len_func = %s', utf8_len_func(ctx)))
ctx:stmt(sformat(' local c = utf8_len_func(%s)',ctx:param(1)))
ctx:stmt(sformat(' local c = %s(%s)', ctx:libfunc('lib.utf8_len'), ctx:param(1)))
ctx:stmt(sformat(' if c < %d then', schema.minLength))
ctx:stmt(sformat(' return false, %s("string too short, expected at least %d, got ") ..c',
ctx:libfunc('string.format'), schema.minLength))
ctx:stmt( ' end')
end
if schema.maxLength then
ctx:stmt(sformat(' local utf8_len_func = %s', utf8_len_func(ctx)))
ctx:stmt(sformat(' local c = utf8_len_func(%s)',ctx:param(1)))
ctx:stmt(sformat(' local c = %s(%s)', ctx:libfunc('lib.utf8_len'), ctx:param(1)))
ctx:stmt(sformat(' if c > %d then', schema.maxLength))
ctx:stmt(sformat(' return false, %s("string too long, expected at most %d, got ") .. c',
ctx:libfunc('string.format'), schema.maxLength))
Expand Down