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Memoize cwstring when used for env lookup / modification on Windows #51371

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merged 9 commits into from
Nov 27, 2023
Merged

Memoize cwstring when used for env lookup / modification on Windows #51371

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90e65d4
Workaround to improve `@debug` performance on Windows
MasonProtter Sep 18, 2023
0a90885
Merge branch 'master' into patch-10
IanButterworth Oct 4, 2023
6c7fbe4
use a lookup dict for all env variables on windows
MasonProtter Nov 25, 2023
bb4ac4d
Merge branch 'master' into patch-10
MasonProtter Nov 26, 2023
328170b
refactor memoization into separate function
MasonProtter Nov 26, 2023
b5d7c18
Update env.jl
MasonProtter Nov 26, 2023
bc86c4f
fix typos
MasonProtter Nov 26, 2023
29b32c0
Update base/env.jl
MasonProtter Nov 26, 2023
cd94fc2
Merge branch 'master' into patch-10
MasonProtter Nov 26, 2023
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27 changes: 22 additions & 5 deletions base/env.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -3,12 +3,29 @@
if Sys.iswindows()
const ERROR_ENVVAR_NOT_FOUND = UInt32(203)

const env_dict = IdDict{String, Vector{Cwchar_t}}()
const env_lock = ReentrantLock()

function memoized_env_lookup(str::AbstractString)
# Windows environment variables have a different format from Linux / MacOS, and previously
# incurred allocations because we had to convert a String to a Vector{Cwchar_t} each time
# an environment variable was looked up. This function memoizes that lookup process, storing
# the String => Vector{Cwchar_t} pairs in env_dict
var = get(env_dict, str, nothing)
if isnothing(var)
var = @lock env_lock begin
env_dict[str] = cwstring(str)
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end
end
var
end

_getenvlen(var::Vector{UInt16}) = ccall(:GetEnvironmentVariableW,stdcall,UInt32,(Ptr{UInt16},Ptr{UInt16},UInt32),var,C_NULL,0)
_hasenv(s::Vector{UInt16}) = _getenvlen(s) != 0 || Libc.GetLastError() != ERROR_ENVVAR_NOT_FOUND
_hasenv(s::AbstractString) = _hasenv(cwstring(s))
_hasenv(s::AbstractString) = _hasenv(memoized_env_lookup(s))

function access_env(onError::Function, str::AbstractString)
var = cwstring(str)
var = memoized_env_lookup(str)
len = _getenvlen(var)
if len == 0
return Libc.GetLastError() != ERROR_ENVVAR_NOT_FOUND ? "" : onError(str)
Expand All @@ -21,16 +38,16 @@ if Sys.iswindows()
end

function _setenv(svar::AbstractString, sval::AbstractString, overwrite::Bool=true)
var = cwstring(svar)
val = cwstring(sval)
var = memoized_env_lookup(svar)
val = memoized_env_lookup(sval)
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if overwrite || !_hasenv(var)
ret = ccall(:SetEnvironmentVariableW,stdcall,Int32,(Ptr{UInt16},Ptr{UInt16}),var,val)
windowserror(:setenv, ret == 0)
end
end

function _unsetenv(svar::AbstractString)
var = cwstring(svar)
var = memoized_env_lookup(svar)
ret = ccall(:SetEnvironmentVariableW,stdcall,Int32,(Ptr{UInt16},Ptr{UInt16}),var,C_NULL)
windowserror(:setenv, ret == 0 && Libc.GetLastError() != ERROR_ENVVAR_NOT_FOUND)
end
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