[Coverage] Move logic to encode filenames and mappings into llvm (NFC)

Currently, frontends which emit source-based code coverage have to
duplicate logic to encode filenames and raw coverage mappings properly.
This violates an abstraction layer and forces frontends to copy tricky
code.

Introduce llvm::coverage::encodeFilenamesAndRawMappings() to take care
of this.

This will help us experiment with zlib-compressing coverage mapping
data.

llvm-svn: 273055

1 files changed, 49 insertions, 8 deletions

diff --git a/llvm/lib/ProfileData/Coverage/CoverageMappingWriter.cpp b/llvm/lib/ProfileData/Coverage/CoverageMappingWriter.cpp
index 8ff90d6..4ac3ab3 100644
--- a/llvm/lib/ProfileData/Coverage/CoverageMappingWriter.cpp
+++ b/llvm/lib/ProfileData/Coverage/CoverageMappingWriter.cpp
@@ -18,14 +18,6 @@
 using namespace llvm;
 using namespace coverage;
 
-void CoverageFilenamesSectionWriter::write(raw_ostream &OS) {
-  encodeULEB128(Filenames.size(), OS);
-  for (const auto &Filename : Filenames) {
-    encodeULEB128(Filename.size(), OS);
-    OS << Filename;
-  }
-}
-
 namespace {
 /// \brief Gather only the expressions that are used by the mapping
 /// regions in this function.
@@ -181,3 +173,52 @@ void CoverageMappingWriter::write(raw_ostream &OS) {
   // Ensure that all file ids have at least one mapping region.
   assert(CurrentFileID == (VirtualFileMapping.size() - 1));
 }
+
+/// \brief Encode coverage data into \p OS.
+static void encodeCoverageData(ArrayRef<std::string> Filenames,
+                               ArrayRef<std::string> CoverageMappings,
+                               size_t &FilenamesSize,
+                               size_t &CoverageMappingsSize, raw_ostream &OS) {
+  size_t OSOffset = OS.GetNumBytesInBuffer();
+
+  // Encode the filenames.
+  encodeULEB128(Filenames.size(), OS);
+  for (const auto &Filename : Filenames) {
+    encodeULEB128(Filename.size(), OS);
+    OS << Filename;
+  }
+
+  FilenamesSize = OS.GetNumBytesInBuffer() - OSOffset;
+
+  // Encode the coverage mappings.
+  for (const auto &RawMapping : CoverageMappings)
+    OS << RawMapping;
+
+  // Pad the output stream to an 8-byte boundary. Account for the padding bytes
+  // in \p CoverageMappingsSize.
+  if (size_t Rem = OS.GetNumBytesInBuffer() % 8) {
+    CoverageMappingsSize += 8 - Rem;
+    for (size_t I = 0, S = 8 - Rem; I < S; ++I)
+      OS << '\0';
+  }
+
+  CoverageMappingsSize = OS.GetNumBytesInBuffer() - FilenamesSize - OSOffset;
+}
+
+namespace llvm {
+namespace coverage {
+
+Expected<std::string> encodeFilenamesAndRawMappings(
+    ArrayRef<std::string> Filenames, ArrayRef<std::string> CoverageMappings,
+    size_t &FilenamesSize, size_t &CoverageMappingsSize) {
+  std::string CoverageData;
+  {
+    raw_string_ostream OS{CoverageData};
+    encodeCoverageData(Filenames, CoverageMappings, FilenamesSize,
+                       CoverageMappingsSize, OS);
+  }
+  return std::move(CoverageData);
+}
+
+} // end namespace coverage
+} // end namespace llvm