njames93 created this revision.
njames93 added a reviewer: sammccall.
Herald added subscribers: usaxena95, kadircet, arphaman.
njames93 requested review of this revision.
Herald added subscribers: cfe-commits, MaskRay, ilya-biryukov.
Herald added a project: clang.
Reusing the buffers for reading messages will alleviate some malloc pressure,
alluded to in D93452 <https://reviews.llvm.org/D93452>.
This is potentially unsafe as the StringRef returned will be invalidated on
sucessive calls and its not thread-safe.
However given there is only 1 call site those both appear to be non-issues.
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D93531
Files:
clang-tools-extra/clangd/JSONTransport.cpp
Index: clang-tools-extra/clangd/JSONTransport.cpp
===================================================================
--- clang-tools-extra/clangd/JSONTransport.cpp
+++ clang-tools-extra/clangd/JSONTransport.cpp
@@ -136,12 +136,20 @@
}
// Read raw string messages from input stream.
- llvm::Optional<std::string> readRawMessage() {
+ // This stores the message in buffer owned by this class, as such once this
+ // method is called, any previous StringRefs held from this are invalidated.
+ llvm::Optional<StringRef> readRawMessage() {
return Style == JSONStreamStyle::Delimited ? readDelimitedMessage()
: readStandardMessage();
}
- llvm::Optional<std::string> readDelimitedMessage();
- llvm::Optional<std::string> readStandardMessage();
+ llvm::Optional<StringRef> readDelimitedMessage();
+ llvm::Optional<StringRef> readStandardMessage();
+
+ // Accept that these buffers are going to be large enough that there is no
+ // point in inline storage. Using a SmallString also saves the need for
+ // unnecessary things null terminators.
+ llvm::SmallString<0> JsonContentBuffer;
+ llvm::SmallString<0> JsonLineBuffer;
std::FILE *In;
llvm::raw_ostream &Out;
@@ -190,7 +198,7 @@
// Tries to read a line up to and including \n.
// If failing, feof(), ferror(), or shutdownRequested() will be set.
-bool readLine(std::FILE *In, std::string &Out) {
+bool readLine(std::FILE *In, llvm::SmallVectorImpl<char> &Out) {
static constexpr int BufSize = 1024;
size_t Size = 0;
Out.clear();
@@ -215,17 +223,16 @@
// Returns None when:
// - ferror(), feof(), or shutdownRequested() are set.
// - Content-Length is missing or empty (protocol error)
-llvm::Optional<std::string> JSONTransport::readStandardMessage() {
+llvm::Optional<StringRef> JSONTransport::readStandardMessage() {
// A Language Server Protocol message starts with a set of HTTP headers,
// delimited by \r\n, and terminated by an empty line (\r\n).
unsigned long long ContentLength = 0;
- std::string Line;
while (true) {
- if (feof(In) || ferror(In) || !readLine(In, Line))
+ if (feof(In) || ferror(In) || !readLine(In, JsonLineBuffer))
return llvm::None;
- InMirror << Line;
+ InMirror << JsonLineBuffer;
- llvm::StringRef LineRef(Line);
+ llvm::StringRef LineRef(JsonLineBuffer);
// We allow comments in headers. Technically this isn't part
@@ -264,23 +271,23 @@
return llvm::None;
}
- std::string JSON(ContentLength, '\0');
+ JsonContentBuffer.resize(ContentLength);
for (size_t Pos = 0, Read; Pos < ContentLength; Pos += Read) {
// Handle EINTR which is sent when a debugger attaches on some platforms.
- Read = retryAfterSignalUnlessShutdown(0, [&]{
- return std::fread(&JSON[Pos], 1, ContentLength - Pos, In);
+ Read = retryAfterSignalUnlessShutdown(0, [&] {
+ return std::fread(&JsonContentBuffer[Pos], 1, ContentLength - Pos, In);
});
if (Read == 0) {
elog("Input was aborted. Read only {0} bytes of expected {1}.", Pos,
ContentLength);
return llvm::None;
}
- InMirror << llvm::StringRef(&JSON[Pos], Read);
+ InMirror << llvm::StringRef(&JsonContentBuffer[Pos], Read);
clearerr(In); // If we're done, the error was transient. If we're not done,
// either it was transient or we'll see it again on retry.
Pos += Read;
}
- return std::move(JSON);
+ return StringRef(JsonContentBuffer);
}
// For lit tests we support a simplified syntax:
@@ -288,12 +295,11 @@
// - lines starting with # are ignored.
// This is a testing path, so favor simplicity over performance here.
// When returning None, feof(), ferror(), or shutdownRequested() will be set.
-llvm::Optional<std::string> JSONTransport::readDelimitedMessage() {
- std::string JSON;
- std::string Line;
- while (readLine(In, Line)) {
- InMirror << Line;
- auto LineRef = llvm::StringRef(Line).trim();
+llvm::Optional<StringRef> JSONTransport::readDelimitedMessage() {
+ JsonContentBuffer.clear();
+ while (readLine(In, JsonLineBuffer)) {
+ InMirror << JsonLineBuffer;
+ auto LineRef = llvm::StringRef(JsonLineBuffer).trim();
if (LineRef.startswith("#")) // comment
continue;
@@ -301,7 +307,7 @@
if (LineRef.rtrim() == "---")
break;
- JSON += Line;
+ JsonContentBuffer += JsonLineBuffer;
}
if (shutdownRequested())
@@ -310,7 +316,7 @@
elog("Input error while reading message!");
return llvm::None;
}
- return std::move(JSON); // Including at EOF
+ return StringRef(JsonContentBuffer); // Including at EOF
}
} // namespace
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