OS::readFile: use SmallVector::resize_for_overwrite for minor efficie…

…ncy gain

include/slang/text/SourceManager.h

@@ -20,6 +20,7 @@
 
 #include "slang/text/SourceLocation.h"
 #include "slang/util/Hash.h"
+#include "slang/util/SmallVector.h"
 #include "slang/util/Util.h"
 
 namespace slang {
@@ -146,7 +147,7 @@ class SLANG_EXPORT SourceManager {
 
     /// Instead of loading source from a file, move it from text already in memory.
     /// Pretend it came from a file located at @a path.
-    SourceBuffer assignBuffer(std::string_view path, std::vector<char>&& buffer,
+    SourceBuffer assignBuffer(std::string_view path, SmallVector<char>&& buffer,
                               SourceLocation includedFrom = SourceLocation(),
                               const SourceLibrary* library = nullptr);
 
@@ -227,12 +228,12 @@ class SLANG_EXPORT SourceManager {
     // Stores actual file contents and metadata; only one per loaded file
     struct FileData {
         const std::string name;                       // name of the file
-        const std::vector<char> mem;                  // file contents
+        const SmallVector<char> mem;                  // file contents
         std::vector<size_t> lineOffsets;              // cache of compute line offsets
         const std::filesystem::path* const directory; // directory in which the file exists
         const std::filesystem::path fullPath;         // full path to the file
 
-        FileData(const std::filesystem::path* directory, std::string name, std::vector<char>&& data,
+        FileData(const std::filesystem::path* directory, std::string name, SmallVector<char>&& data,
                  std::filesystem::path fullPath) :
             name(std::move(name)),
             mem(std::move(data)), directory(directory), fullPath(std::move(fullPath)) {}
@@ -319,7 +320,7 @@ class SLANG_EXPORT SourceManager {
                              const SourceLibrary* library);
     SourceBuffer cacheBuffer(std::filesystem::path&& path, std::string&& pathStr,
                              SourceLocation includedFrom, const SourceLibrary* library,
-                             std::vector<char>&& buffer);
+                             SmallVector<char>&& buffer);
 
     template<IsLock TLock>
     size_t getRawLineNumber(SourceLocation location, TLock& lock) const;
@@ -339,7 +340,7 @@ class SLANG_EXPORT SourceManager {
     template<IsLock TLock>
     SourceRange getExpansionRangeImpl(SourceLocation location, TLock& lock) const;
 
-    static void computeLineOffsets(const std::vector<char>& buffer,
+    static void computeLineOffsets(const SmallVector<char>& buffer,
                                    std::vector<size_t>& offsets) noexcept;
 };
 

include/slang/util/OS.h

@@ -8,9 +8,9 @@
 #pragma once
 
 #include <filesystem>
-#include <vector>
 
 #include "slang/util/ScopeGuard.h"
+#include "slang/util/SmallVector.h"
 #include "slang/util/Util.h"
 
 namespace fmt {
@@ -42,7 +42,7 @@ class SLANG_EXPORT OS {
     /// Reads a file from @a path into memory. If successful, the bytes are placed
     /// into @a buffer -- otherwise, returns false.
     /// Note that the buffer will be null-terminated.
-    static std::error_code readFile(const std::filesystem::path& path, std::vector<char>& buffer);
+    static std::error_code readFile(const std::filesystem::path& path, SmallVector<char>& buffer);
 
     /// Prints text to stdout.
     static void print(std::string_view text);

source/driver/Driver.cpp

@@ -309,7 +309,7 @@ bool Driver::processCommandFiles(std::string_view pattern, bool makeRelative) {
         return onError(pattern, globEc);
 
     for (auto& path : files) {
-        std::vector<char> buffer;
+        SmallVector<char> buffer;
         if (auto readEc = OS::readFile(path, buffer))
             return onError(getU8Str(path), readEc);
 

source/text/SourceManager.cpp

@@ -245,15 +245,15 @@ SourceBuffer SourceManager::assignText(std::string_view path, std::string_view t
         path = temp;
     }
 
-    std::vector<char> buffer;
+    SmallVector<char> buffer;
     buffer.insert(buffer.end(), text.begin(), text.end());
     if (buffer.empty() || buffer.back() != '\0')
         buffer.push_back('\0');
 
     return assignBuffer(path, std::move(buffer), includedFrom, library);
 }
 
-SourceBuffer SourceManager::assignBuffer(std::string_view bufferPath, std::vector<char>&& buffer,
+SourceBuffer SourceManager::assignBuffer(std::string_view bufferPath, SmallVector<char>&& buffer,
                                          SourceLocation includedFrom,
                                          const SourceLibrary* library) {
     // first see if we have this file cached
@@ -453,7 +453,7 @@ SourceManager::BufferOrError SourceManager::openCached(const fs::path& fullPath,
     }
 
     // do the read
-    std::vector<char> buffer;
+    SmallVector<char> buffer;
     if (std::error_code ec = OS::readFile(absPath, buffer)) {
         std::unique_lock lock(mutex);
         lookupCache.emplace(pathStr, std::pair{nullptr, ec});
@@ -466,7 +466,7 @@ SourceManager::BufferOrError SourceManager::openCached(const fs::path& fullPath,
 
 SourceBuffer SourceManager::cacheBuffer(fs::path&& path, std::string&& pathStr,
                                         SourceLocation includedFrom, const SourceLibrary* library,
-                                        std::vector<char>&& buffer) {
+                                        SmallVector<char>&& buffer) {
     std::string name;
     if (!disableProximatePaths) {
         std::error_code ec;
@@ -593,7 +593,7 @@ SourceLocation SourceManager::getOriginalLocImpl(SourceLocation location, TLock&
     return std::get<ExpansionInfo>(bufferEntries[buffer.getId()]).originalLoc + location.offset();
 }
 
-void SourceManager::computeLineOffsets(const std::vector<char>& buffer,
+void SourceManager::computeLineOffsets(const SmallVector<char>& buffer,
                                        std::vector<size_t>& offsets) noexcept {
     // first line always starts at offset 0
     offsets.push_back(0);

source/util/OS.cpp

@@ -69,7 +69,7 @@ bool OS::fileSupportsColors(FILE* file) {
     return fileSupportsColors(_fileno(file));
 }
 
-std::error_code OS::readFile(const fs::path& path, std::vector<char>& buffer) {
+std::error_code OS::readFile(const fs::path& path, SmallVector<char>& buffer) {
     HANDLE handle = ::CreateFileW(path.native().c_str(), GENERIC_READ,
                                   FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE, NULL,
                                   OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL | FILE_FLAG_SEQUENTIAL_SCAN,
@@ -93,7 +93,7 @@ std::error_code OS::readFile(const fs::path& path, std::vector<char>& buffer) {
         }
         else {
             size_t fileSize = (size_t(fileInfo.nFileSizeHigh) << 32) + fileInfo.nFileSizeLow;
-            buffer.resize(fileSize + 1);
+            buffer.resize_for_overwrite(fileSize + 1);
 
             char* buf = buffer.data();
             while (fileSize) {
@@ -126,7 +126,7 @@ std::error_code OS::readFile(const fs::path& path, std::vector<char>& buffer) {
 
         size_t currSize = 0;
         while (true) {
-            buffer.resize(currSize + ChunkSize);
+            buffer.resize_for_overwrite(currSize + ChunkSize + 1);
 
             DWORD bytesRead = 0;
             BOOL result = ::ReadFile(handle, buffer.data() + currSize, ChunkSize, &bytesRead, NULL);
@@ -168,7 +168,7 @@ bool OS::fileSupportsColors(FILE* file) {
     return fileSupportsColors(fileno(file));
 }
 
-std::error_code OS::readFile(const fs::path& path, std::vector<char>& buffer) {
+std::error_code OS::readFile(const fs::path& path, SmallVector<char>& buffer) {
     int fd;
     while (true) {
         fd = ::open(path.native().c_str(), O_RDONLY | O_CLOEXEC);
@@ -186,7 +186,7 @@ std::error_code OS::readFile(const fs::path& path, std::vector<char>& buffer) {
     }
     else if (S_ISREG(status.st_mode) || S_ISBLK(status.st_mode)) {
         auto fileSize = (size_t)status.st_size;
-        buffer.resize(fileSize + 1);
+        buffer.resize_for_overwrite(fileSize + 1);
 
         char* buf = buffer.data();
         while (fileSize) {
@@ -217,7 +217,7 @@ std::error_code OS::readFile(const fs::path& path, std::vector<char>& buffer) {
 
         size_t currSize = 0;
         while (true) {
-            buffer.resize(currSize + ChunkSize);
+            buffer.resize_for_overwrite(currSize + ChunkSize + 1);
 
             ssize_t numRead = ::read(fd, buffer.data() + currSize, ChunkSize);
             if (numRead < 0) {