| // Copyright 2019 The LUCI Authors. |
| // |
| // Licensed under the Apache License, Version 2.0 (the "License"); |
| // you may not use this file except in compliance with the License. |
| // You may obtain a copy of the License at |
| // |
| // http://www.apache.org/licenses/LICENSE-2.0 |
| // |
| // Unless required by applicable law or agreed to in writing, software |
| // distributed under the License is distributed on an "AS IS" BASIS, |
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| // See the License for the specific language governing permissions and |
| // limitations under the License. |
| |
| package lucicfg |
| |
| import ( |
| "go.starlark.net/starlark" |
| |
| "go.chromium.org/luci/starlark/interpreter" |
| ) |
| |
| // How many times a file needs to be read before its data is cached in memory. |
| // |
| // E.g. if cachingThreshold is 2, first two io.read_file calls will actually |
| // load the file from disk, and only the third call (and onward) will use |
| // the cached data. |
| // |
| // This is a heuristic to avoid spending RAM on files that will be read only |
| // once. |
| const cachingThreshold = 2 |
| |
| type fileCache struct { |
| interner stringInterner |
| cache map[interpreter.ModuleKey]fileCacheEntry |
| } |
| |
| type fileCacheEntry struct { |
| hits int // 0, 1, .., cachingThreshold (no counting after cachingThreshold) |
| data string // the cached data if hits == cachingThreshold, "" otherwise |
| } |
| |
| func newFileCache(interner stringInterner) fileCache { |
| return fileCache{ |
| interner: interner, |
| cache: map[interpreter.ModuleKey]fileCacheEntry{}, |
| } |
| } |
| |
| func (c *fileCache) get(key interpreter.ModuleKey, load func() (string, error)) (string, error) { |
| entry := c.cache[key] |
| if entry.hits == cachingThreshold { |
| return entry.data, nil |
| } |
| |
| data, err := load() |
| if err != nil { |
| return "", err |
| } |
| |
| if data != "" { |
| entry.hits += 1 |
| if entry.hits == cachingThreshold { |
| entry.data = c.interner.internString(data) |
| } |
| } else { |
| // Can cache "" right away, no RAM impact. |
| entry.hits = cachingThreshold |
| } |
| |
| c.cache[key] = entry |
| return data, nil |
| } |
| |
| func init() { |
| // See //internal/io.star. |
| declNative("read_file", func(call nativeCall) (starlark.Value, error) { |
| var path starlark.String |
| if err := call.unpack(1, &path); err != nil { |
| return nil, err |
| } |
| intr := interpreter.GetThreadInterpreter(call.Thread) |
| key, err := interpreter.MakeModuleKey(call.Thread, path.GoString()) |
| if err != nil { |
| return nil, err |
| } |
| src, err := call.State.files.get(key, func() (string, error) { |
| return intr.LoadSource(call.Thread, path.GoString()) |
| }) |
| return starlark.String(src), err |
| }) |
| } |